From rssh at gradsoft.com.ua  Wed Apr  1 00:16:19 2009
From: rssh at gradsoft.com.ua (rssh at gradsoft.com.ua)
Date: Wed, 1 Apr 2009 10:16:19 +0300 (EEST)
Subject: PROPOSAL: Templated Construction Expressions (i.e.,
	Expressions Embedded in Strings)
In-Reply-To: <D3460884-91EF-4A03-A27C-55C80EBC8A23@Sun.COM>
References: <3dd3f56a0903181505m517125a0w30f0aa540d1d038b@mail.gmail.com>
	<977c14e250a47d19b21f818f9aceb1aa.squirrel@wmail.gradsoft.ua>
	<7D2077BFF677D2429DDDEE095D9A48AC105DFB8D@osiris2.e-spirit.de>
	<d676b6030903190833r411aa4caia1b208e1d00bd618@mail.gmail.com>
	<C67745F8-23F3-4BBE-B809-A7BFF40FB7B3@sun.com>
	<9EA33E4A-C6EB-4F54-93E5-0E06FBD1876F@sun.com>
	<c85ebad40b68337eb125b306c12cfa07.squirrel@wmail.gradsoft.ua>
	<D3460884-91EF-4A03-A27C-55C80EBC8A23@Sun.COM>
Message-ID: <dbcac46b7835c95f8afda71dd57a783e.squirrel@wmail.gradsoft.ua>

>
> On Mar 30, 2009, at 10:37 PM, rssh at gradsoft.com.ua wrote:
>
>>> On Mar 20, 2009, at 1:50 PM, John Rose wrote:
>>>
>> 3. COMPABILITY - this breaks all code with use $ in string literals.
>> (Or I
>> read something incorrectly ?)   So better prefix such string with
>> something. (may be yet one '$' or '@' ?)
>
> You read incorrectly.  Template constructor expressions are distinct
> from string literals.  They are prefixed with the token "new".
>

 Thanks, I reread you proposal and see that I missed too many during first
reading.

 With explicit compile, I see that - we already have analogical JSR223
mechanism in language, which would be nice to reuse.

>> 4. Why just not call this parser from some method ?  I. e. what
>> arguments
>> for including string templates in language itself, instead library
>> call ?
>
> The usual:  Sugar like that can help API designers build APIs whose
> code is more maintainable:  Less noisy.  Template-based systems are
> popular for a reason.
>

This would be difference between

new "template-text"

and

new MyCompiler("template-text")

// i. e. main magic is in assigned template-expression to appendable.

Thanks, now I understand.
   Hope will be change implement this in (E x: x>=7): Java x


> -- John
>




From Ulf.Zibis at gmx.de  Wed Apr  1 01:39:23 2009
From: Ulf.Zibis at gmx.de (Ulf Zibis)
Date: Wed, 01 Apr 2009 10:39:23 +0200
Subject: Proposal and updates OVERSEEN
Message-ID: <49D3283B.4040709@gmx.de>

Hi Joe,

in the last update of your blog, you have overseen my proposal:
http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001163.html
and it's update:
Extend switch .. case statement for all types and simple expressions 
<http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001182.html>

Also you've overseen this update:
Simply implicit method invocation chaining 
<http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001180.html>

Hopefully you will update your blog :-)

-Ulf



From tim.lebedkov at googlemail.com  Wed Apr  1 02:00:06 2009
From: tim.lebedkov at googlemail.com (Tim Lebedkov)
Date: Wed, 1 Apr 2009 11:00:06 +0200
Subject: PROPOSAL: 'final' without explicit type (update)
In-Reply-To: <28bca0ff0903310658k15b0c9abk45270080ab7cf7af@mail.gmail.com>
References: <28bca0ff0903301426o7449e309t9de2e43743593ea6@mail.gmail.com>
	<cf66e280903301545v1132a31dx2f53e041d4572295@mail.gmail.com>
	<28bca0ff0903301609y10c30815ice919d750f523745@mail.gmail.com>
	<cf66e280903301806h3b7edd12se160364e0f88f04c@mail.gmail.com>
	<28bca0ff0903302340s3aa480a4h3f675ca5e1a00741@mail.gmail.com>
	<e07797830903310643y1a4bb46dw616767f2bf44f465@mail.gmail.com>
	<28bca0ff0903310658k15b0c9abk45270080ab7cf7af@mail.gmail.com>
Message-ID: <e07797830904010200w5faec38fh9ad2fecddcec647f@mail.gmail.com>

Hello Marek,

now it's more clear to me why you use 'final'.

Thanks
Tim

On Tue, Mar 31, 2009 at 3:58 PM, Marek Kozie? <develop4lasu at gmail.com> wrote:
> W dniu 31 marca 2009 15:43 u?ytkownik Tim Lebedkov
> <tim.lebedkov at googlemail.com> napisa?:
>> Hello Marek,
>>
>> my proposal (http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001055.html)
>> is very similar to yours (it just uses 'auto' instead of 'final').
>>
>> Does yours declare variables as final (I mean here 'constant') only
>> because you try to avoid introducing a new keyword? Or is there
>> another motivation?
>>
>> Tim
>>
>
> First of all I want Java to have clear separation on variables and values.
> And then:
> - variables should have explicit type.
> - values should have clear context;
>
> While now people use variables even if they need value, it's because
> cost using value is higher than using variable. This provide worse
> code, more bugs, and provoke reusing variables.
>
>
> --
> Pozdrowionka. / Regards.
> Lasu aka Marek Kozie?
>
> http://lasu2string.blogspot.com/
>


From tim.lebedkov at googlemail.com  Wed Apr  1 02:02:53 2009
From: tim.lebedkov at googlemail.com (Tim Lebedkov)
Date: Wed, 1 Apr 2009 11:02:53 +0200
Subject: PROPOSAL: 'final' without explicit type (update)
In-Reply-To: <A90AEE09-5276-4839-89C7-13D53AAB7127@zwitserloot.com>
References: <28bca0ff0903301426o7449e309t9de2e43743593ea6@mail.gmail.com>
	<cf66e280903301545v1132a31dx2f53e041d4572295@mail.gmail.com>
	<28bca0ff0903301609y10c30815ice919d750f523745@mail.gmail.com>
	<cf66e280903301806h3b7edd12se160364e0f88f04c@mail.gmail.com>
	<28bca0ff0903302340s3aa480a4h3f675ca5e1a00741@mail.gmail.com>
	<e07797830903310643y1a4bb46dw616767f2bf44f465@mail.gmail.com>
	<A90AEE09-5276-4839-89C7-13D53AAB7127@zwitserloot.com>
Message-ID: <e07797830904010202h201fb098u65517961075c7635@mail.gmail.com>

Hello Reinier,

2009/3/31 Reinier Zwitserloot <reinier at zwitserloot.com>:

> FWIW, I'm -strongly- in favour of implicit typing for final local method
> variables, and opposed to extending this for non-finals, not just because
> its hard to come up with a syntax for it, due to there being no readily
> available keywords or operators to do it with. := comes to mind, but that's
> about it.
>
> NB2: If you want to push forward with this proposal anyway, I strongly
> suggest you rewrite it to this, which would be far more backwards
> compatible:
>
> foo := expression;
>
> instead of:
>
> auto foo = expression;

Thank you for the suggestion, but I think 'auto' is better and fits
better in the current language.

Regards
--Tim


From Ulf.Zibis at gmx.de  Wed Apr  1 02:17:30 2009
From: Ulf.Zibis at gmx.de (Ulf Zibis)
Date: Wed, 01 Apr 2009 11:17:30 +0200
Subject: Extend switch .. case statement for all types and simple
	expressions
In-Reply-To: <49D14427.5070105@gmx.de>
References: <49D14427.5070105@gmx.de>
Message-ID: <49D33129.2090600@gmx.de>

I would like to add, that the MAJOR ADVANTAGE of my proposal is,
that the numerous grades/levels of this proposal could be implemented 
step by step, depending on the complexity of changes, which could be 
done for JDK 7.
More sophisticated grades/levels could be seamlessly added later.
This would be impossible, if the concurring syntax of "Strings in 
switch", which only compares for equality, comes to account.
Also Multiple switch expressions and case ranges 
<http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000213.html> 
could seamlessly be integrated in my proposal.

As I argued more detailed before, default semantic of "switch..case" 
should stay on determining the cases by IDENTITY.
Strings, which are equal, could simply be made identical by String#intern().

Example:
    switch (myStringFromElsewere.intern()) {
        case STRING1 : ...; // all constants are interned by definition
        case STRING2 : ...; //       "            "
        case "foo" : ...; // automatically interned
        case "bar" : ...; //       "            "
        ...
    }

-Ulf


Am 31.03.2009 00:13, Ulf Zibis schrieb:
> AUTHOR(S): Ulf Zibis, Cologne, Germany
>
> OVERVIEW
> FEATURE SUMMARY: Extend switch .. case statement for all types and simple expressions.
> MAJOR ADVANTAGE:
> - Increases readability of source in concurrence to if .. else if .. else syntax.
> - Sophisticated jumps.
> - maybe in some cases javac and hotspot has chance to compute better optimized code.
> MAJOR BENEFIT:
> Stop some programmers escaping to some modern scripting language.
> MAJOR DISADVANTAGE:
> Programmers from other languages, especially C, may be confused about such rich syntax.
>
> EXAMPLES
> SIMPLE EXAMPLE:
> (1):
>      switch( myObject) {
>          case CONSTANT1 : doSomething(); break;
>          case CONSTANT2 : doSomethingElse(); break;
>          default : doSomethingDefault();
>      }
> (2):
>      switch( myString) {
>          case equals("red") : stop(); break;
>          case equals("green") : go(); break;
>          default : openYourEyesForCrossingTraffic();
>      }
> (3):
>      switch( myString) {
>          case equalsIgnoreCase("RED") : sureStop(); break;
>          case equalsIgnoreCase("GREEN") : sureGo(); break;
>          default : beAwareOfPoliceWachtingYou();
>      }
>
> ADVANCED EXAMPLE:
> (4):
>      switch( primitiveInt) {
>          case == 10 : doOnlyIf10(); // alternative syntax for 'case 10:'
>          case < 10 :
>          case >= 20 : break;
>          default : doOnlyInRange();
>      }
> (5):
>      switch( primitiveInt) {
>          case (>= 10 && < 20) : doOnlyInRange();
>          default : throw new Exception("Out of range");
>      }
> (6):
>      switch( myString) {
>          case contains("foo") : doSomething(); break;
>          case regionMatches(true, 2, otherString, 4, 6) : doSomethingElse(); break;
>          default : doSomethingDefault();
>      }
> (7):
>      switch( myString.equals()) { // alternative: myString.equals(..)
>          case "foo" : foo(); break;
>          case "bar" : bar(); break;
>          default : dontCare();
>      }
> (8):
>      switch( className.startsWith("String", ..)) { // alternative: className.startsWith("String", ?)
>          case 0 : doForSimpleName(); break;
>          case 9 : doForFullName(); break;
>          default : canNotDecide();
>      }
> (9):
>      switch( anyObjectOrPrimitive instanceof) { // note, that casting is solved implicit
>          case boolean, byte, ... float : break; // Don't do anything
>          case double : forDouble(anyObjectOrPrimitive);
>          case HashMap :
>          case TreeMap : forPlattformMap(anyObjectOrPrimitive); break;
>          case Map : forOtherMap(anyObjectOrPrimitive); break;
>          default : forObject(anyObjectOrPrimitive);
>      }
> (10): (minimizee chance for NPE)
>      switch( .equals(myString)) { // alternative: ?.equals(myString)
>          case "foo" : foo(); break;
>          case "bar" : bar(); break;
>          default : dontCare();
>      }
> (11):
>      switch( some_lethargic_function_we_cant_call_much().equals(..) ) {
>          case "this":
>          case "that":       this_or_that(); break;
>          case "bigjump":    big();    // fall
>          case "jump":       jump(); break;
>          case "secondlastchance":
>          case "lastchance": last_chance(); break;
>          default:           do_default();
>      }
> .. as replacement for:
>      String sSomeString = some_lethargic_function_we_cant_call_much();
>      if( sSomeString.equals( "this" ) || sSomeString.equals( "that" ) )
>          this_or_that();
>      else if( sSomeString.equals( "jump" ) || sSomeString.equals( "bigjump" ) )
>      {
>          if( sSomeString.equals( "bigjump" ) )
>              big();
>          jump();
>      } else if( sSomeString.equals( "secondlastchance" ) ||
>              sSomeString.equals( "lastchance" ) )
>      {
>          last_chance();
>      } else do_default();
>
> ALTERNATIVES:
> (12):
>      switch( myString) {  // note the '.', I personally would prefer this alternative!
>          case .equals("red") : stop(); break;
>          case .equals("green") : go(); break;
>          default : openYourEyesForCrossingTraffic();
>      }
> (13):
>      switch( primitiveInt) {  // note the '.'
>          case (. >= 10 && . < 20) : doOnlyInRange();
> //        case (? >= 10 && ? < 20) : doOnlyInRange(); // alternative
>          default : throw new Exception("Out of range");
>      }
>
>
> DETAILS
> SPECIFICATION:
> The new syntax should be interpreted as
>      switch ( leftExpressionPart ) {
>          case rightExpressionPart1 :
>          case rightExpressionPart2 :
>          ...
>          default :
>      }
> The result of entire expression should be boolean type.
> There is shortcut for:
>      leftExpressionPart: intVariable
>      rightExpressionPart: == intLiteral
> (the '==' could be ommitted.)
>
> COMPILATION:
> Compiler could first pre-compile to appropriate if..then..else syntax.
> Bytecode would not be affected, but in special cases it could be more compact, if noted 
> pre-compilation would be replaced by sophisticated optimization.
> TESTING:
> Compiler byte-code results for new syntax should be same than from equivalent hand-coded legacy 
> if..then..else syntax
> . Exception: sophisticated optimization.
> LIBRARY SUPPORT: No supporting libraries are needed for the feature?
> REFLECTIVE APIS: There should not be any affection to reflection API.
> OTHER CHANGES: No.
> MIGRATION:
> No refactoring is needed to stay compatible.
>
> COMPATIBILITY
> BREAKING CHANGES:
> No previously valid programs are now invalid.
> ... but ATTENTION:
> If proposals from some other guys regarding "Strings in switch" would be taken into JDK 7, there 
> won't be any compatible way to implement my more general proposal in future version of JDK !!!
> --> So switch .. case statement should compare for IDENTITY if not syntactically determined otherwise.
> --> compare for EQUALITY would also break semantic of existing switch .. case statement.
> Another reason, why I'm against comparing for equality by default syntax, is, that it is good 
> practice to use String constants instead of widely spreaded String literals with same signature for 
> numerous reasons (performance, error prone, ...). The "only-for-String" syntax would lead 
> programmers to stay on widely spreaded String literals of same value.
> If constant is not available for switch variable (e.g. if read from stream), variable could be 
> internalized before, so it's instance becomes identical to the existing constant.
> ===>> If just "Strings in switch" is taken over for JDK 7, there is NO NEED, to compare for equality.
> EXISTING PROGRAMS:
> Source and class files of earlier platform versions interact with the feature without any notice.
>
> REFERENCES
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-February/000001.html
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000213.html
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000855.html
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001089.html
> http://forums.java.net/jive/thread.jspa?messageID=27781&#27781
> http://forums.java.net/jive/thread.jspa?messageID=15769&#15769
> http://forums.java.net/jive/thread.jspa?messageID=27773&#27773
> http://forums.java.net/jive/thread.jspa?messageID=11393&#11393
> http://lasu2string.blogspot.com/2008/12/string-switch-small-language-changes-on.html
> EXISTING BUGS:
> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5012262
> URL FOR PROTOTYPE (optional):
>
>
>
>
>
>
>
>   


From jl0235 at yahoo.com  Wed Apr  1 06:21:39 2009
From: jl0235 at yahoo.com (james lowden)
Date: Wed, 1 Apr 2009 06:21:39 -0700 (PDT)
Subject: Opportunity Cost and Proposal Selection
In-Reply-To: <49D2CA2F.1040401@sun.com>
Message-ID: <751882.88756.qm@web63706.mail.re1.yahoo.com>


Joe-

I noticed that the version of the "large arrays" linked from your blog is the older (and messier) one; I updated it to this one:

http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000869.html





--- On Tue, 3/31/09, Joe Darcy <Joe.Darcy at Sun.COM> wrote:

> From: Joe Darcy <Joe.Darcy at Sun.COM>
> Subject: Opportunity Cost and Proposal Selection
> To: "coin-dev at openjdk.java.net" <coin-dev at openjdk.java.net>
> Date: Tuesday, March 31, 2009, 8:58 PM
> Hello.
> 
> There has been some traffic on the list about criteria for
> proposal 
> selection (and non-selection) and I wanted to discuss that
> briefly.
> 
> First, a reminder from some earlier blog entries describing
> the context 
> for Project Coin:
> 
> "Especially with the maturity of the Java platform,
> the onus is on the 
> proposer to convince that a language change should go in;
> the onus is 
> not to prove the change should stay out."
> http://blogs.sun.com/darcy/entry/criteria_for_desirable_small_language
> December 23, 2008
> 
> "Given the rough timeline for JDK 7 and other on-going
> efforts to change 
> the language, such as modules and annotations on types,
> only a limited 
> number of small changes can be considered for JDK 7."
> http://blogs.sun.com/darcy/entry/guidance_measure_language_change_size
> December 11, 2008
> 
> With nearly 70 proposals submitted to the mailing list and
> the Sun bug 
> database having well over 100 open "requests for
> enhancements" (rfe's) 
> for the language, the large majority of those proposals and
> rfe's will 
> *not* be included in JDK 7 as part of Project Coin or any
> other effort.
> 
> Project Coin will be limited to around 5 proposals total. 
> That's it.
> 
> Therefore for Project Coin, in addition to determining
> whether a 
> proposal to change the language is in and of itself
> appropriate, a 
> determination also has to be made as to whether the change
> is more 
> compelling than all but four or so other proposals.
> 
> In economic terms, there an an opportunity cost in the
> proposal 
> selection; that is, because of finite resources, choosing
> to have a 
> particular proposal in the platform removes the opportunity
> to do other 
> proposals.
> 
> There will be good, compelling proposals that would improve
> the language 
> *not* selected for Project Coin because there are a full
> set of better, 
> more compelling proposals that are more useful to include
> instead.
> 
> Having available prototypes for proposals, running the
> existing tests, 
> and writing new tests can only better inform the
> forthcoming proposal 
> evaluation and selection.
> 
> -Joe


      


From glenn.a.marshall at gmail.com  Wed Apr  1 07:12:40 2009
From: glenn.a.marshall at gmail.com (Glenn A. Marshall)
Date: Wed, 1 Apr 2009 10:12:40 -0400
Subject: PROPOSAL: open and close brace optional for single statement try, 
	catch, finally, method declaration
In-Reply-To: <15e8b9d20903310751m2da11e10q97ea59c4ffed1bd2@mail.gmail.com>
References: <49d02e12.18038e0a.6c4e.ffffa859@mx.google.com>
	<980366fa0903300445y6727dfaehc885c184d0dbe2c6@mail.gmail.com>
	<49D0C82D.1000208@sun.com>
	<980366fa0903310522u31ac7641r6a1554c188122175@mail.gmail.com>
	<15e8b9d20903310751m2da11e10q97ea59c4ffed1bd2@mail.gmail.com>
Message-ID: <980366fa0904010712r5ce024c6xaf0185cf923dc068@mail.gmail.com>

I understand that the grammar to handle this, if it was implemented in the
obvious way (analogous to the dangling else) is hackish and thus not
preferred.  I sympathize and agree with this.  I agree that this increases
the effort/cost to implement this proposal, as well as make the grammar more
hackish on an ongoing basis.  Part of the assessment is to consider the
cost, thus this is a relevant point.

This proposal is still in an early state, and does not have an prototype
implementation, nor a proposed grammar, both of which would reduce the cost
to implement this proposal.  I understand that some implementation questions
will be resolved if the grammar component of the implementation was
available, and it was unambiguous, from a grammar perspective.

But you seem to be saying something else - that, conceptually, from a code
perspective this proposal isn't clear.  Can you elaborate please?  I believe
the code snippet you originally provided is handled.

Tom:  you seemed to be saying that you thought this was clear, originally,
then later you also raised questions - have your questions been answered?

On Tue, Mar 31, 2009 at 10:51 AM, Neal Gafter <neal at gafter.com> wrote:

> On Tue, Mar 31, 2009 at 5:22 AM, Glenn A. Marshall
> <glenn.a.marshall at gmail.com> wrote:
> > Indeed, the grammar would change.  It was my hope that this proposal was
> > sufficiently detailed that the grammar changes needed would be clear,
> > conceptually.  Are they?
>
> Not to me.  Seeing the (unambiguous) grammar for your proposal would
> clear up a bunch of questions.
>


From glenn.a.marshall at gmail.com  Wed Apr  1 07:33:35 2009
From: glenn.a.marshall at gmail.com (Glenn A. Marshall)
Date: Wed, 1 Apr 2009 10:33:35 -0400
Subject: Opportunity Cost and Proposal Selection
Message-ID: <980366fa0904010733o5655fe5di10aa2c44883f7a6e@mail.gmail.com>

Will the details of the proposal evaluations be published?  The thinking
here is that for proposals that almost made the cut, perhaps the evaluations
would reveal where a bit more work might push them over the line for the
next round - increase benefit/decrease cost.

This is assuming there will be a next round.

Any thoughts on round II?  It would seem to be worth considering, given the
level of interest.  It would, of course, have to wait until Java 8, but why
not start early?

Surely you're busy with round I for now, but perhaps there could be a
parallel effort, with the initial effort primarily around email.

thanks for doing all of this,

Glenn


From neal at gafter.com  Wed Apr  1 07:39:57 2009
From: neal at gafter.com (Neal Gafter)
Date: Wed, 1 Apr 2009 07:39:57 -0700
Subject: PROPOSAL: open and close brace optional for single statement try, 
	catch, finally, method declaration
In-Reply-To: <980366fa0904010712r5ce024c6xaf0185cf923dc068@mail.gmail.com>
References: <49d02e12.18038e0a.6c4e.ffffa859@mx.google.com>
	<980366fa0903300445y6727dfaehc885c184d0dbe2c6@mail.gmail.com>
	<49D0C82D.1000208@sun.com>
	<980366fa0903310522u31ac7641r6a1554c188122175@mail.gmail.com>
	<15e8b9d20903310751m2da11e10q97ea59c4ffed1bd2@mail.gmail.com>
	<980366fa0904010712r5ce024c6xaf0185cf923dc068@mail.gmail.com>
Message-ID: <15e8b9d20904010739w3d877199k2846e84cb7cb47b@mail.gmail.com>

On Wed, Apr 1, 2009 at 7:12 AM, Glenn A. Marshall
<glenn.a.marshall at gmail.com> wrote:
> But you seem to be saying something else - that, conceptually, from a code
> perspective this proposal isn't clear.? Can you elaborate please?? I believe
> the code snippet you originally provided is handled.

The usual technique for handling the dangling else problem is to
rewrite the grammar so that it is no longer ambiguous.  In other
words, programs that under an ambiguous grammar would have more than
one interpretation will, under the rewritten grammar, get a single
interpretation.  I gave an example that is ambiguous in your proposal.
 Instead of suggesting that it would be handled in one way or another,
you said that it would be illegal.  That's not the same solution
normally applied to the dangling-else problem.  A more precise
specification in the form of a grammar would help us better understand
what you have in mind.

However, I believe the question is moot because I don't believe this
proposal has any chance of being considered.  Besides lacking a
specification, it doesn't address a common pain point for Java
programmers or add to the expressive power of the language.


From fw at deneb.enyo.de  Wed Apr  1 08:56:27 2009
From: fw at deneb.enyo.de (Florian Weimer)
Date: Wed, 01 Apr 2009 17:56:27 +0200
Subject: PROPOSAL: 'final' without explicit type
References: <28bca0ff0903261305x2de00436r5ca8183fe01578d4@mail.gmail.com>
	<A0A1A39D-6569-41C5-AFD4-250EB82BF0C3@zwitserloot.com>
	<87fxgwzfew.fsf@mid.deneb.enyo.de>
	<28bca0ff0903291422s77f11c44j4ddf6ea45ec0b669@mail.gmail.com>
Message-ID: <87zlf0pduc.fsf@mid.deneb.enyo.de>

* Marek Kozie?:

> 	<T extends I1&I2,K extends I1&I2> void noInterection(T t,K k){
> 		if (boo)t=k; // Type mismatch: cannot convert from K to T
> 		...
> 	}

The assignment is not type-safe anyway, as the following modification
shows:


	<T extends I1&I2,K extends I1&I2> T noInterection(T t,K k){
		if (boo)t=k; // Type mismatch: cannot convert from K to T
		return t;
	}

This would allow to convert values of any type which implements I1 and
I2 to any other type which implements the two interfaces, which is
clearly bogus.

Consequently, I think your snippet doesn't show what you claim.


From alexandre.makarenko at free.fr  Wed Apr  1 10:16:54 2009
From: alexandre.makarenko at free.fr (alexandre.makarenko at free.fr)
Date: Wed, 1 Apr 2009 19:16:54 +0200 (CEST)
Subject: Naked dot - accessing object fields through unqualified "." [C1]
In-Reply-To: <28bca0ff0903310631o2cb0b4dey19e857514cece0e8@mail.gmail.com>
Message-ID: <14413946.4511781238606214731.JavaMail.root@spooler2-g27.priv.proxad.net>

Hi Marek,
could you comment this please

Read:
     class Bar {
          public String     name;
          public Bar          right;
     }

     class Root {
          public Bar     right;
          public Bar     left;

          public Root(Bar right, Bar left) {
               this.left = this.// left is set here
               right = right;
          }

     }


alex


----- Original Message -----
From: "Marek Kozie?" <develop4lasu at gmail.com>
To: "Derek Foster" <vapor1 at teleport.com>
Cc: coin-dev at openjdk.java.net
Sent: Tuesday, March 31, 2009 3:31:13 PM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
Subject: Re: Naked dot - accessing object fields through unqualified "." [C1]

2009/3/29 Derek Foster <vapor1 at teleport.com>:
> The major problem I have with this proposal is that it does not address the point of why I use a prefix on field names. As such, I would still continue to use a prefix even if this proposal were implemented.
>
> In short, I use a prefix to avoid typographical mistakes, like this one:
>
> void setFoo(Thing foob) { // Typo!
> ? ?this.foo = foo;
> }
>
> This will compile, and no warnings are produced, but it ends up assigning foo to itself, which is not what was intended.
>
> Your proposal has exactly the same problem:
>
> void setFoo(Thing foob) { // Typo!
> ? ?.foo = foo;
> }
>
> It therefore does not substitute for a field prefix, which WILL fix the problem:
>
> void setFoo(Thing foob) { // Typo!
> ? ?_foo = foo; // ERROR! Undefined variable 'foo'.
> }
>

You can use:
Eclipse -> Java -> Code Style -> Edit -> Member Access -> Use 'this'
qualifier for field access. (Always)

> So unless you had some way to make use of the dot prefix mandatory and the only legal way to access fields (which I would like, but which would be an extremely backwards-incompatible change that will never happen in Java), I don't see that adding an optional dot prefix helps the situation except to reduce typing in constructor and setter methods slightly.
>
> (Note: I would love a "self-assignment is forbidden" change to Java. If I have time after my other proposals, I might write one up. (Anyone else want to volunteer? This one is easy!) I might be willing to forego prefixes and use the "this.foo = foo" approach, or even the ".foo = foo" approach, if I was sure it wouldn't cause me to fall into the self-assignment trap.)
>
> Derek
>
>
>

Read:
     class Bar {
          public String     name;
          public Bar          right;
     }

     class Root {
          public Bar     right;
          public Bar     left;

          public Root(Bar right, Bar left) {
               this.left = left// left is set here
               .right = right;
          }

     }


Did you noticed missing semicolon?

-- 
Pozdrowionka. / Regards.
Lasu aka Marek Kozie?

http://lasu2string.blogspot.com/



From christian at fi12.de  Wed Apr  1 11:03:14 2009
From: christian at fi12.de (Christian Fischer)
Date: Wed, 1 Apr 2009 20:03:14 +0200 (CEST)
Subject: Proposal: Sameness operators
In-Reply-To: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.n
	et>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
Message-ID: <b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>

These $-operators doesn't seem intuitive to me, but replacing equal-calls
sounds interesting.

Maybe a better solution would be something like this:
if (a eq b) // equals
if (a ne b) // not equal
if (a lt b) // lesser than
if (a le b) // lesser or equal
....


From Thomas.Hawtin at Sun.COM  Wed Apr  1 11:26:43 2009
From: Thomas.Hawtin at Sun.COM (Tom Hawtin)
Date: Wed, 01 Apr 2009 19:26:43 +0100
Subject: Proposal: Sameness operators
In-Reply-To: <b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>
Message-ID: <49D3B1E3.8070109@sun.com>

Christian Fischer wrote:
> These $-operators doesn't seem intuitive to me, but replacing equal-calls
> sounds interesting.
> 
> Maybe a better solution would be something like this:
> if (a eq b) // equals
> if (a ne b) // not equal
> if (a lt b) // lesser than
> if (a le b) // lesser or equal

Along with other concerns, four new keywords?! Theoretically they could 
be context sensitive, but then we are boxing in the grammar.

If something like this were to be done (and let's face it, operator 
overloading ain't gonna happen in JDK7), then I think there needs to be 
to changes in fundamental direction of the proposal.

  * We need new symbols. .<. and the like were proposed in another 
similar proposal. So long as the symbol is a sequence of characters 
which is not valid in an existing Java program (outside of comments and 
literal strings).

  * I think it's clear that we can't use Comparable.compareTo and 
Object.equals. It requires a new method for each operator.

Tom


From Joe.Darcy at Sun.COM  Wed Apr  1 11:54:40 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Wed, 01 Apr 2009 11:54:40 -0700
Subject: Opportunity Cost and Proposal Selection
In-Reply-To: <751882.88756.qm@web63706.mail.re1.yahoo.com>
References: <751882.88756.qm@web63706.mail.re1.yahoo.com>
Message-ID: <49D3B870.7030601@sun.com>

james lowden wrote:
> Joe-
>
> I noticed that the version of the "large arrays" linked from your blog is the older (and messier) one; I updated it to this one:
>
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000869.html
>   

Hello.

I added a link to the revised version.

-Joe


From Joe.Darcy at Sun.COM  Wed Apr  1 12:55:14 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Wed, 01 Apr 2009 12:55:14 -0700
Subject: Proposal and updates OVERSEEN
In-Reply-To: <49D3283B.4040709@gmx.de>
References: <49D3283B.4040709@gmx.de>
Message-ID: <49D3C6A2.2040505@sun.com>

Ulf Zibis wrote:
> Hi Joe,
>
> in the last update of your blog, you have overseen my proposal:
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001163.html
> and it's update:
> Extend switch .. case statement for all types and simple expressions 
> <http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001182.html>
>
> Also you've overseen this update:
> Simply implicit method invocation chaining 
> <http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001180.html>
>
> Hopefully you will update your blog :-)
>
> -Ulf
>
>   

Blog updated accordingly.

Thanks,

-Joe



From howard.lovatt at iee.org  Wed Apr  1 13:34:07 2009
From: howard.lovatt at iee.org (Howard Lovatt)
Date: Thu, 2 Apr 2009 07:34:07 +1100
Subject: Proposal idea - generators
In-Reply-To: <15e8b9d20903310749n4bb99322ldd92a96e3aa965c0@mail.gmail.com>
References: <3dd3f56a0903310414w4c579d63xbc8f31ff0ff82021@mail.gmail.com>
	<15e8b9d20903310749n4bb99322ldd92a96e3aa965c0@mail.gmail.com>
Message-ID: <3dd3f56a0904011334n50b17e59rd2ffaab5985b018a@mail.gmail.com>

Hi Neal,

I couldn't see in your blog where the problem is. Note I am not
proposing, and I don't believe the original poster was either, a
continuation style yield. More a Scala and other non-lazy functional
language style were the results are stored in a Map and the Map is
returned, i.e. like applying (mapping) a function to each element of a
list but with more control (in particular break and continue
functionality).

Maybe you read the original post differently to me.

  -- Howard.

2009/4/1 Neal Gafter <neal at gafter.com>:
> On Tue, Mar 31, 2009 at 4:14 AM, Howard Lovatt <howard.lovatt at iee.org> wrote:
>> You can write a library to do this and also have break/continue
>> control and parallel processing if needed:
>>
>> ? ? ? http://www.artima.com/weblogs/viewpost.jsp?thread=240412
>
> Howard-
>
> Your library does not "do this". ?See
> http://gafter.blogspot.com/2007/07/internal-versus-external-iterators.html
> for an explanation of why not.
>
> Regards,
> Neal
>
> ______________________________________________________________________
> This email has been scanned by the MessageLabs Email Security System.
> For more information please visit http://www.messagelabs.com/email
> ______________________________________________________________________
>


From neal at gafter.com  Wed Apr  1 14:41:34 2009
From: neal at gafter.com (Neal Gafter)
Date: Wed, 1 Apr 2009 14:41:34 -0700
Subject: Proposal idea - generators
In-Reply-To: <3dd3f56a0904011334n50b17e59rd2ffaab5985b018a@mail.gmail.com>
References: <3dd3f56a0903310414w4c579d63xbc8f31ff0ff82021@mail.gmail.com>
	<15e8b9d20903310749n4bb99322ldd92a96e3aa965c0@mail.gmail.com>
	<3dd3f56a0904011334n50b17e59rd2ffaab5985b018a@mail.gmail.com>
Message-ID: <15e8b9d20904011441l3736b6b4me3ac78808bb9f450@mail.gmail.com>

On Wed, Apr 1, 2009 at 1:34 PM, Howard Lovatt <howard.lovatt at iee.org> wrote:
> Note I am not
> proposing, and I don't believe the original poster was either, a
> continuation style yield. More a Scala and other non-lazy functional
> language style were the results are stored in a Map and the Map is
> returned, i.e. like applying (mapping) a function to each element of a
> list but with more control (in particular break and continue
> functionality).

Scala's comprehensions using their standard libraries are lazy.  See,
for example, Iterator.range.  C#'s iterator methods are translated
into a state machine (i.e. coroutines) and are inherently lazy.  F#
and OCaml are the most widely used non-lazy functional languages, but
their comprehensions are lazy too.  So I'm not sure what you're saying
your proposal is comparable to.


From neal at gafter.com  Wed Apr  1 14:56:34 2009
From: neal at gafter.com (Neal Gafter)
Date: Wed, 1 Apr 2009 14:56:34 -0700
Subject: Proposal idea - generators
In-Reply-To: <15e8b9d20904011441l3736b6b4me3ac78808bb9f450@mail.gmail.com>
References: <3dd3f56a0903310414w4c579d63xbc8f31ff0ff82021@mail.gmail.com>
	<15e8b9d20903310749n4bb99322ldd92a96e3aa965c0@mail.gmail.com>
	<3dd3f56a0904011334n50b17e59rd2ffaab5985b018a@mail.gmail.com>
	<15e8b9d20904011441l3736b6b4me3ac78808bb9f450@mail.gmail.com>
Message-ID: <15e8b9d20904011456r8084a0dsf4f6878c1fa4a5a8@mail.gmail.com>

On Wed, Apr 1, 2009 at 2:41 PM, Neal Gafter <neal at gafter.com> wrote:
> On Wed, Apr 1, 2009 at 1:34 PM, Howard Lovatt <howard.lovatt at iee.org> wrote:
>> Note I am not
>> proposing, and I don't believe the original poster was either, a
>> continuation style yield. More a Scala and other non-lazy functional
>> language style were the results are stored in a Map and the Map is
>> returned, i.e. like applying (mapping) a function to each element of a
>> list but with more control (in particular break and continue
>> functionality).
>
> Scala's comprehensions using their standard libraries are lazy. ?See,
> for example, Iterator.range. ?C#'s iterator methods are translated
> into a state machine (i.e. coroutines) and are inherently lazy. ?F#
> and OCaml are the most widely used non-lazy functional languages, but
> their comprehensions are lazy too. ?So I'm not sure what you're saying
> your proposal is comparable to.

I may be wrong about OCaml's generators.


From develop4lasu at gmail.com  Wed Apr  1 15:28:15 2009
From: develop4lasu at gmail.com (=?UTF-8?Q?Marek_Kozie=C5=82?=)
Date: Thu, 2 Apr 2009 00:28:15 +0200
Subject: Proposal and updates OVERSEEN
In-Reply-To: <49D3C6A2.2040505@sun.com>
References: <49D3283B.4040709@gmx.de> <49D3C6A2.2040505@sun.com>
Message-ID: <28bca0ff0904011528p1041b241yc1d41bcb546bc2ad@mail.gmail.com>

2009/4/1 Joseph D. Darcy <Joe.Darcy at sun.com>:
>
> Blog updated accordingly.
>
> Thanks,
>
> -Joe
>

Hi.
I'll add my:


Updated proposals:
 - Return 'this'
http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001185.html

- 'final' without explicit type
http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001178.html



Can be removed:
 - 'This' type - while it require from generics to have tagged types
it's not possible to introduce it into language.
 - Enhanced while statement - It was created only to show complex
problems with loops.



Missed:
 - Delegation proposal
http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000477.html

- 'forget' keyword
http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001093.html

  Even if they were missed by reason I would like to know that.


-- 
Pozdrowionka. / Regards.
Lasu aka Marek Kozie?

http://lasu2string.blogspot.com/


From develop4lasu at gmail.com  Wed Apr  1 16:05:38 2009
From: develop4lasu at gmail.com (=?UTF-8?Q?Marek_Kozie=C5=82?=)
Date: Thu, 2 Apr 2009 01:05:38 +0200
Subject: Naked dot - accessing object fields through unqualified "." [C1]
In-Reply-To: <14413946.4511781238606214731.JavaMail.root@spooler2-g27.priv.proxad.net>
References: <28bca0ff0903310631o2cb0b4dey19e857514cece0e8@mail.gmail.com>
	<14413946.4511781238606214731.JavaMail.root@spooler2-g27.priv.proxad.net>
Message-ID: <28bca0ff0904011605x6d65fd7cqf87d058ae0d3724d@mail.gmail.com>

2009/4/1  <alexandre.makarenko at free.fr>:
> Hi Marek,
> could you comment this please
>
> Read:
> ? ? class Bar {
> ? ? ? ? ?public String ? ? name;
> ? ? ? ? ?public Bar ? ? ? ? ?right;
> ? ? }
>
> ? ? class Root {
> ? ? ? ? ?public Bar ? ? right;
> ? ? ? ? ?public Bar ? ? left;
>
> ? ? ? ? ?public Root(Bar right, Bar left) {
> ? ? ? ? ? ? ? this.left = this.// left is set here
> ? ? ? ? ? ? ? right = right;
> ? ? ? ? ?}
>
> ? ? }
>
>
> alex
>

Hi.
This was measured that if you split expresion into more lines operator
should be placed at start:

Operator(s) (during splitting exprestion into two lines) should be
placed in a new line, like:
String s = "could you comment this please " //
   + "\n\nRead:";

This is easier to read, bacause it shows directly that previous line
need to be checked to understand this one.
What's more, operator placed in the end of the line can be over the screen.

So, this line:
   this.left = this.// left is set here
is consider to be bad style.

-- 
Pozdrowionka. / Regards.
Lasu aka Marek Kozie?

http://lasu2string.blogspot.com/


From neal at gafter.com  Wed Apr  1 17:20:43 2009
From: neal at gafter.com (Neal Gafter)
Date: Wed, 1 Apr 2009 17:20:43 -0700
Subject: Proposal idea - generators
In-Reply-To: <5090A08F-7225-477B-A390-D3A73A62823E@gmail.com>
References: <3dd3f56a0903310414w4c579d63xbc8f31ff0ff82021@mail.gmail.com>
	<15e8b9d20903310749n4bb99322ldd92a96e3aa965c0@mail.gmail.com>
	<3dd3f56a0904011334n50b17e59rd2ffaab5985b018a@mail.gmail.com>
	<15e8b9d20904011441l3736b6b4me3ac78808bb9f450@mail.gmail.com>
	<15e8b9d20904011456r8084a0dsf4f6878c1fa4a5a8@mail.gmail.com>
	<5090A08F-7225-477B-A390-D3A73A62823E@gmail.com>
Message-ID: <15e8b9d20904011720t349fd2e4x98ee29b16328cd86@mail.gmail.com>

On Wed, Apr 1, 2009 at 4:13 PM, Howard Lovatt <howard.lovatt at gmail.com> wrote:
> My reading of the Scala Language Specification, page 83, is that the for
> loop is translated into a map call (or similar). Therefore whether this is
> lazy or not is an implementation detail. So I think it is valid to eagerly
> evaluate the loop and store the results in a hash map. After all, the
> current Java for loop evaluates eagerly.

Whether a given Iterator used in a Java for-each loop produces its
values eagerly or lazily is an implementation detail of that iterator.
 Requiring it to be eager reduces the flexibility.


From howard.lovatt at gmail.com  Wed Apr  1 16:13:08 2009
From: howard.lovatt at gmail.com (Howard Lovatt)
Date: Thu, 2 Apr 2009 10:13:08 +1100
Subject: Proposal idea - generators
In-Reply-To: <15e8b9d20904011456r8084a0dsf4f6878c1fa4a5a8@mail.gmail.com>
References: <3dd3f56a0903310414w4c579d63xbc8f31ff0ff82021@mail.gmail.com>
	<15e8b9d20903310749n4bb99322ldd92a96e3aa965c0@mail.gmail.com>
	<3dd3f56a0904011334n50b17e59rd2ffaab5985b018a@mail.gmail.com>
	<15e8b9d20904011441l3736b6b4me3ac78808bb9f450@mail.gmail.com>
	<15e8b9d20904011456r8084a0dsf4f6878c1fa4a5a8@mail.gmail.com>
Message-ID: <5090A08F-7225-477B-A390-D3A73A62823E@gmail.com>

My reading of the Scala Language Specification, page 83, is that the  
for loop is translated into a map call (or similar). Therefore whether  
this is lazy or not is an implementation detail. So I think it is  
valid to eagerly evaluate the loop and store the results in a hash  
map. After all, the current Java for loop evaluates eagerly.

Functional languages like Mathematica, which are extensively used in  
Science and maths, eagerly evalate and store the results. In fact this  
is a common array generation means.

   -- Howard

On 02/04/2009, at 8:56 AM, Neal Gafter <neal at gafter.com> wrote:

> On Wed, Apr 1, 2009 at 2:41 PM, Neal Gafter <neal at gafter.com> wrote:
>> On Wed, Apr 1, 2009 at 1:34 PM, Howard Lovatt  
>> <howard.lovatt at iee.org> wrote:
>>> Note I am not
>>> proposing, and I don't believe the original poster was either, a
>>> continuation style yield. More a Scala and other non-lazy functional
>>> language style were the results are stored in a Map and the Map is
>>> returned, i.e. like applying (mapping) a function to each element  
>>> of a
>>> list but with more control (in particular break and continue
>>> functionality).
>>
>> Scala's comprehensions using their standard libraries are lazy.  See,
>> for example, Iterator.range.  C#'s iterator methods are translated
>> into a state machine (i.e. coroutines) and are inherently lazy.  F#
>> and OCaml are the most widely used non-lazy functional languages, but
>> their comprehensions are lazy too.  So I'm not sure what you're  
>> saying
>> your proposal is comparable to.
>
> I may be wrong about OCaml's generators.
>
> ______________________________________________________________________
> This email has been scanned by the MessageLabs Email Security System.
> For more information please visit http://www.messagelabs.com/email
> ______________________________________________________________________


From markmahieu at googlemail.com  Wed Apr  1 23:05:17 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Thu, 2 Apr 2009 07:05:17 +0100
Subject: Proposal and updates OVERSEEN
In-Reply-To: <28bca0ff0904011528p1041b241yc1d41bcb546bc2ad@mail.gmail.com>
References: <49D3283B.4040709@gmx.de> <49D3C6A2.2040505@sun.com>
	<28bca0ff0904011528p1041b241yc1d41bcb546bc2ad@mail.gmail.com>
Message-ID: <cf90c1f10904012305y606f207ek9ed5b25ba485a13d@mail.gmail.com>

One more :)

The 'Rethrows Clause' proposal was also updated with JLS references, here:
http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001198.html

(The proposal and prototype linked to at
http://slm888.com/javac/coin-rethrows.html has a further minor adjustment to
simplify the rules around exception type constructors which themselves throw
checked exceptions).

Mark


2009/4/1 Marek Kozie? <develop4lasu at gmail.com>

> 2009/4/1 Joseph D. Darcy <Joe.Darcy at sun.com>:
> >
> > Blog updated accordingly.
> >
> > Thanks,
> >
> > -Joe
> >
>
> Hi.
> I'll add my:
>
>
> Updated proposals:
>  - Return 'this'
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001185.html
>
> - 'final' without explicit type
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001178.html
>
>
>
> Can be removed:
>  - 'This' type - while it require from generics to have tagged types
> it's not possible to introduce it into language.
>  - Enhanced while statement - It was created only to show complex
> problems with loops.
>
>
>
> Missed:
>  - Delegation proposal
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000477.html
>
> - 'forget' keyword
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001093.html
>
>  Even if they were missed by reason I would like to know that.
>
>
> --
> Pozdrowionka. / Regards.
> Lasu aka Marek Kozie?
>
> http://lasu2string.blogspot.com/
>
>


From scolebourne at joda.org  Thu Apr  2 04:39:56 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Thu, 2 Apr 2009 12:39:56 +0100
Subject: Helping to find the usefulness of a proposal
Message-ID: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>

All,
One possible way I'd like to suggest that the coin evaluation could be
helped would be to write a script to find out how frequently the
specific issue comes up in real code.

It should be possible to devise, write and run a script to find the
number of LOCs affected by many of the proposals. For example:

- strings in switch (find if else on constant strings)
- multi-catch (find duplicate catch blocks)
- elvis operator (find ternary and if else defaulting)
- for each where the iterator remove can be accessed (% of loops that
access iterator)
- for each where index is needed (% of loops that use int looping)
- method and field literals
- byte and short literals
and probably many others (I've just listed some proposals I remember)

Ideally, any script would be ASM/BCEL based, but grep style might work too.

I mention all this because I don't have the spare time to write such a
script, but if you do, then I'm sure we'd all like to run it and
discuss the results ;-)

Stephen


From markmahieu at googlemail.com  Thu Apr  2 04:44:21 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Thu, 2 Apr 2009 12:44:21 +0100
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
Message-ID: <cf90c1f10904020444t13f0594eme1205f7d30b1342b@mail.gmail.com>

Definitely.

I did that for the Auto-assigned Parameters proposal actually, but I chose
to use javac's parser and then did my own analysis based on the AST.
There might be something generically useful I can split out from that
hacked-up code, if people want to use the same technique.

Mark


2009/4/2 Stephen Colebourne <scolebourne at joda.org>

> All,
> One possible way I'd like to suggest that the coin evaluation could be
> helped would be to write a script to find out how frequently the
> specific issue comes up in real code.
>
> It should be possible to devise, write and run a script to find the
> number of LOCs affected by many of the proposals. For example:
>
> - strings in switch (find if else on constant strings)
> - multi-catch (find duplicate catch blocks)
> - elvis operator (find ternary and if else defaulting)
> - for each where the iterator remove can be accessed (% of loops that
> access iterator)
> - for each where index is needed (% of loops that use int looping)
> - method and field literals
> - byte and short literals
> and probably many others (I've just listed some proposals I remember)
>
> Ideally, any script would be ASM/BCEL based, but grep style might work too.
>
> I mention all this because I don't have the spare time to write such a
> script, but if you do, then I'm sure we'd all like to run it and
> discuss the results ;-)
>
> Stephen
>
>


From reinier at zwitserloot.com  Thu Apr  2 04:46:30 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Thu, 2 Apr 2009 13:46:30 +0200
Subject: Proposal: Sameness operators
In-Reply-To: <49D3B1E3.8070109@sun.com>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>
	<49D3B1E3.8070109@sun.com>
Message-ID: <88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>

Why can't we use compareTo and equals?

.<. syntax had severe problems that disqualified them - see the  
archive of this mailing list.

'is' has slightly more precedence than 'eq' and the set 'eq', 'ne',  
'lt', and 'le' need 'gt' and 'ge' as well, which makes them rather  
unwieldy. You can reduce a thing or two by going with just 'eq', 'lt'  
and 'gt', filling the holes with && and ! as usual (not equal becomes ! 
(a eq b)), or even a !eq b, but this is all devolving into way too  
much slap-dash language design unless those become global, non-context  
sensitive keywords. I'm okay with that, but Joe Darcy definitely  
isn't, so that's right out, at least for now.

More symbols is similarly unwieldy; there are no appropriate symbols  
for these operations available. It would be an even greater mistake to  
come up with some non-standard and unwieldly syntax for them, such as  
$=. That way lies perl cartoon-swearing craziness and nobody wants  
that. Wholesale operator overloading would be far preferable to that  
situation. ":=" for some sort of inference typing would make some  
sense and is still free, but that's about where it ends.


The cleanest solution to me remains a cleaning of the slate, so to  
speak, and an explicit demarkation in your source file that you're on  
'new java', such as with "source 1.8". With that at the top, "a == b"  
is compiled the same way as old java's "a == null ? b == null :  
a.equals(b)" for non-boxable objects (for unboxables and primitives,  
Unbox everything you can, then do a numeric comparison, or if it's  
primitive v. object, error), "a < b" and its ilk translate  
to .compareTo for non-unboxable Comparables, lead to unboxing for  
unboxables, no change for primitives, and error otherwise. Past  
mistakes are rectified, blahblahblah. We've been over this before, I'm  
sure most coin-dev readers have a good idea about how such a thing  
would work and the decade+ timerift it would cause between code bases  
that (stubbornly?) stay with non-new java.



  --Reinier Zwitserloot
Like it? Tip it!
http://tipit.to



On Apr 1, 2009, at 20:26, Tom Hawtin wrote:

> Christian Fischer wrote:
>> These $-operators doesn't seem intuitive to me, but replacing equal- 
>> calls
>> sounds interesting.
>>
>> Maybe a better solution would be something like this:
>> if (a eq b) // equals
>> if (a ne b) // not equal
>> if (a lt b) // lesser than
>> if (a le b) // lesser or equal
>
> Along with other concerns, four new keywords?! Theoretically they  
> could
> be context sensitive, but then we are boxing in the grammar.
>
> If something like this were to be done (and let's face it, operator
> overloading ain't gonna happen in JDK7), then I think there needs to  
> be
> to changes in fundamental direction of the proposal.
>
>  * We need new symbols. .<. and the like were proposed in another
> similar proposal. So long as the symbol is a sequence of characters
> which is not valid in an existing Java program (outside of comments  
> and
> literal strings).
>
>  * I think it's clear that we can't use Comparable.compareTo and
> Object.equals. It requires a new method for each operator.
>
> Tom
>



From peter.levart at gmail.com  Thu Apr  2 04:59:25 2009
From: peter.levart at gmail.com (Peter Levart)
Date: Thu, 2 Apr 2009 13:59:25 +0200
Subject: Proposal: Automatic Resource Management
Message-ID: <aad309390904020459m6d85ea6aqa8ade12dbab67399@mail.gmail.com>

Hello Coiners!

The debate about ARM proposal has calmed down lately and I was thinking
about it last few days. Initially I submitted a comment that got lost by
list processor and was about using a "marker" interface as a supertype of
sigle-method disposable interfaces like this:


package java.lang;

public interface AutomaticResource {}


... and for example, retroffiting java.io.Closeable:


package java.io;

public interface Closeable extends AutomaticResource {
    void close() throws IOException;
}


... this way even the name of the method would not be "coined". There would
have to be some rules that compiler will enforce to make sure it can
uniquely identify the method to be called on resource disposal (for example:
the static type of the resource should not directly or indirectly implement
or extend two different single-method interfaces marked with
AutomaticResource marker superinterface).

But then I thought. Why would this language feature even have to be tied to
a particular interface. The "foreach" loop did take this approach with
java.lang.Iterable, but this had nothing to do with exceptions and catching
them and ignoring them silently. A language construct that hides this often
cited "bad practice" under the carpet is no good!

For example, this snippet of code, written to the proposed ARM spec.,
submited by Bob Lee in this thread a month ago, asking Neal Gafter to
demonstrate how the equivalent BGGA version would look like:

  try (InputStream in = new FileInputStream(src);
      OutputStream out = new FileOutputStream(dest)) {
    byte[] buf = new byte[8 * 1024];
    int n;
    while ((n = in.read(buf)) >= 0)
      out.write(buf, 0, n);
  } catch (IOException e) {
    showDialog("Copy failed.");
  }

... is flawed. This code does not guarantee that in the absence of shown
exception the file has been copied in it's intirety.

Ignoring exception thrown on an InputStream.close() might be desireable, but
ignoring exception thrown on OutputStream.close() migh mean that you don't
mind missing writing some final bytes into the file. Closing OutputStream
should not be part of automatic resource disposal but part of main code
block. This brings us to the question how is ARM supposed to be able do
differentiate InputStream from OutputStream if both implement Closeable?

So I thought how to circumvent these two weeknesses. My take on this is
something like the following:


        try (InputStream in = new FileInputStream("inputFile");
             OutputStream out = new FileOutputStream("outputFile"))
        {
          // try body
        }
        catch (IOException e)
        {
          // catch body
        }
        finally (IOException e1 : in.close();
                 IOException e2 : out.close())
        {
          // finally body
        }


... would be translated to ...


        {
            IOException e1 = null;
            IOException e2 = null;

            try
            {
                InputStream in = new FileInputStream("inputFile");

                try
                {
                    OutputStream out = new FileOutputStream("outputFile");

                    try
                    {
                        // try body
                    }
                    finally
                    {
                        try
                        {
                            out.close();
                        }
                        catch (IOException $$e)
                        {
                            e2 = $$e;
                        }
                    }
                }
                finally
                {
                    try
                    {
                        in.close();
                    }
                    catch (IOException $$e)
                    {
                        e1 = $$e;
                    }
                }
            }
            catch (IOException e)
            {
                // catch body
            }
            finally
            {
                // finally body
            }
        }



... no special interfaces are used here. The code to dispose of resources is
clearly visible (it has to be writen, yes, but that also means that it can
be read, which is a good thing).

The above example is the "full monty" version. The thing to note is that a
try (...; ...; ...) construct is to be matched by an optional finally (...;
...; ...) construct in that both, if the second is specified, must have an
equal number of semicolons. Each "statement" in the try construct gets it's
own slot that must be matched by the coresponding slot in the finally (...;
...; ...) construct. Any slot in finally construct can be left empty (like
any of the 3 slots in the for (;;) statement).

The following minimal version is also possible (in this example no catching
of exceptions on resource cleanup is attempted):

int i, j;
ReadWriteLock iLock = ...;
ReadWriteLock jLock = ...;

// ...

try (jLock.readLock().lock(); iLock.writeLock().lock()) {
  i += j;
}
finally (jLock.readLock().unlock(); iLock.writeLock().unlock())


... gets translated to:


{
    jLock.readLock().lock();
    try {
      iLock.writeLock().lock();
      try {
        i += j;
      }
      finally {
        iLock.writeLock().unlock();
      }
    }
    finally {
      jLock.readLock().unlock();
    }
}


All this will have to be formalized. This is just an idea to keep the debate
going.

Regards, Peter


From rssh at gradsoft.com.ua  Thu Apr  2 05:03:33 2009
From: rssh at gradsoft.com.ua (rssh at gradsoft.com.ua)
Date: Thu, 2 Apr 2009 15:03:33 +0300 (EEST)
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
Message-ID: <9ca625bf5b892e4a94f495a155f66e6f.squirrel@wmail.gradsoft.ua>

> All,
> One possible way I'd like to suggest that the coin evaluation could be
> helped would be to write a script to find out how frequently the
> specific issue comes up in real code.
>
> It should be possible to devise, write and run a script to find the
> number of LOCs affected by many of the proposals. For example:
>

Clever idea.
 If I would know, that one will used, I will wrote one during next week-end.

> - strings in switch (find if else on constant strings)
> - multi-catch (find duplicate catch blocks)
> - elvis operator (find ternary and if else defaulting)
> - for each where the iterator remove can be accessed (% of loops that
> access iterator)
> - for each where index is needed (% of loops that use int looping)
> - method and field literals
> - byte and short literals
> and probably many others (I've just listed some proposals I remember)
>
> Ideally, any script would be ASM/BCEL based, but grep style might work
> too.
>
> I mention all this because I don't have the spare time to write such a
> script, but if you do, then I'm sure we'd all like to run it and
> discuss the results ;-)
>
> Stephen
>
>




From pdoubleya at gmail.com  Thu Apr  2 05:15:35 2009
From: pdoubleya at gmail.com (Patrick Wright)
Date: Thu, 2 Apr 2009 14:15:35 +0200
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
Message-ID: <64efa1ba0904020515m679910b4n1be9cce0034e474d@mail.gmail.com>

This would be useful.

One might be able to start by building on the infrastructure in
Checkstyle, PMD or FindBugs for some of these. I don't know about
FindBugs, but the other two allow you to write your own matching
rules. Jackpot could be used as well, but it's no longer maintained as
an independent project (now part of NB refactoring infrastructure).
One would have to use a slightly older version of it.



Patrick


From scolebourne at joda.org  Thu Apr  2 05:24:32 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Thu, 2 Apr 2009 13:24:32 +0100
Subject: Proposal: Sameness operators
In-Reply-To: <88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>
	<49D3B1E3.8070109@sun.com>
	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
Message-ID: <4b4f45e00904020524p27741baeo40483e83d71dc768@mail.gmail.com>

The best alternative operator symbols I've come up with yet are bracketed ones:

 a (==) b
 a (<) b

I don't think that the symbols are ideal, but they do look reasonably
readable, and its way better than .equals().

Do I expect anything to happen here? No. There is a long history of
"operator overloading"  being frowned on in the Java language. The net
result is more of an argument to use Groovy, Scala, Fan etc.

Stephen


2009/4/2 Reinier Zwitserloot <reinier at zwitserloot.com>:
> Why can't we use compareTo and equals?
>
> .<. syntax had severe problems that disqualified them - see the
> archive of this mailing list.
>
> 'is' has slightly more precedence than 'eq' and the set 'eq', 'ne',
> 'lt', and 'le' need 'gt' and 'ge' as well, which makes them rather
> unwieldy. You can reduce a thing or two by going with just 'eq', 'lt'
> and 'gt', filling the holes with && and ! as usual (not equal becomes !
> (a eq b)), or even a !eq b, but this is all devolving into way too
> much slap-dash language design unless those become global, non-context
> sensitive keywords. I'm okay with that, but Joe Darcy definitely
> isn't, so that's right out, at least for now.
>
> More symbols is similarly unwieldy; there are no appropriate symbols
> for these operations available. It would be an even greater mistake to
> come up with some non-standard and unwieldly syntax for them, such as
> $=. That way lies perl cartoon-swearing craziness and nobody wants
> that. Wholesale operator overloading would be far preferable to that
> situation. ":=" for some sort of inference typing would make some
> sense and is still free, but that's about where it ends.
>
>
> The cleanest solution to me remains a cleaning of the slate, so to
> speak, and an explicit demarkation in your source file that you're on
> 'new java', such as with "source 1.8". With that at the top, "a == b"
> is compiled the same way as old java's "a == null ? b == null :
> a.equals(b)" for non-boxable objects (for unboxables and primitives,
> Unbox everything you can, then do a numeric comparison, or if it's
> primitive v. object, error), "a < b" and its ilk translate
> to .compareTo for non-unboxable Comparables, lead to unboxing for
> unboxables, no change for primitives, and error otherwise. Past
> mistakes are rectified, blahblahblah. We've been over this before, I'm
> sure most coin-dev readers have a good idea about how such a thing
> would work and the decade+ timerift it would cause between code bases
> that (stubbornly?) stay with non-new java.
>
>
>
> ?--Reinier Zwitserloot
> Like it? Tip it!
> http://tipit.to
>
>
>
> On Apr 1, 2009, at 20:26, Tom Hawtin wrote:
>
>> Christian Fischer wrote:
>>> These $-operators doesn't seem intuitive to me, but replacing equal-
>>> calls
>>> sounds interesting.
>>>
>>> Maybe a better solution would be something like this:
>>> if (a eq b) // equals
>>> if (a ne b) // not equal
>>> if (a lt b) // lesser than
>>> if (a le b) // lesser or equal
>>
>> Along with other concerns, four new keywords?! Theoretically they
>> could
>> be context sensitive, but then we are boxing in the grammar.
>>
>> If something like this were to be done (and let's face it, operator
>> overloading ain't gonna happen in JDK7), then I think there needs to
>> be
>> to changes in fundamental direction of the proposal.
>>
>> ?* We need new symbols. .<. and the like were proposed in another
>> similar proposal. So long as the symbol is a sequence of characters
>> which is not valid in an existing Java program (outside of comments
>> and
>> literal strings).
>>
>> ?* I think it's clear that we can't use Comparable.compareTo and
>> Object.equals. It requires a new method for each operator.
>>
>> Tom
>>
>
>
>


From reinier at zwitserloot.com  Thu Apr  2 05:24:42 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Thu, 2 Apr 2009 14:24:42 +0200
Subject: Proposal: Automatic Resource Management
In-Reply-To: <aad309390904020459m6d85ea6aqa8ade12dbab67399@mail.gmail.com>
References: <aad309390904020459m6d85ea6aqa8ade12dbab67399@mail.gmail.com>
Message-ID: <370F8DB1-A374-43B4-9F83-ABCD5A925D93@zwitserloot.com>

I remember quite a bit of discussion on that. Some of the problems no  
one really solved:

  - What if one object ends up implementing multiple interfaces that  
are all AutomaticResource subtypes? Call all of them? Compile-time  
error? What if that situation happens at runtime due to updating a  
library? Class Validation? Close all of them in that case, but compile- 
time error if the compiler detects such a situation? Runtime exception?

  - What if one implements AutomaticResource but has multiple methods?  
Who is responsible for warning? Compiler? What if I construct a class  
file with this 'bug' in it? Its easy even without ASM: Use jruby,  
jython, or just an older version of javac. Piece of pie. The JVM can't  
just up and crash when it encounters such a type, so some sort of  
behaviour must be specified.


You also seem to mistaken about the ARM proposal's 'exception hiding'  
principle. As I understand it, this is relevant ONLY if the guarded  
scope  (=contents of the try block) threw an exception of its own. You  
can't throw 2 exceptions simultaneously in java, so one of them has to  
win out. Normally, in try/finally blocks, whatever the finally block  
does wins, but for ARM, the idea is that the try block's exception  
wins, because often .close() will fail if some method on the resource  
itself also failed, and the problem is probably better described with  
a more useful stack trace on the original.

If a try block ends normally, but during resource cleanup the .close()  
causes an exception, that exception will propagate out, it will NOT be  
ignored!

There is no need to catch exceptions wafting off of  
InputStream.close() because they basically never happen. The thing  
that is strongly preferable is to take the annoyance of having to  
worry about InputStream.close() away from the programmer, which ARM  
essentially does. The problem isn't IOExceptions being thrown by  
close(), the problem is InputStream.close()'s declaration that it  
throws this exception, which forces you to handle it. This isn't the  
only erroneous checked exception in java (new String(somebytes,  
"UTF-8") declares that it can throw the checked  
UnsupportedEncodingException, eventhough it actually cant, because  
UTF-8 is guaranteed by the JVM spec to exist. The appropriate way to  
handle this is to catch the UEncEx, and rethrow it as an  
InternalError("JVM Bug"). But I digress - at any rate,  
InputStream.close() in practice doesn't throw exceptions unless  
there's a good reason for it, whereas the UEncEx from String.<init> is  
*defined* that it MUST NOT throw that exception, which puts it in a  
different ballpark).


Your proposal is vague to me: What, exactly, are e1 and e2? Will one  
of them be non-null if there is an exception? What happens if I leave  
my finally body empty, which is what I imagine most people who are in  
a hurry will do? Just get ignored? That would be very bad.

Having to remember the order of the try-block's parameters because  
these are applied to the finally parameters also strikes me as  
particularly bad design; making mistakes in ordering seems like a  
great way to make a puzzler.


  --Reinier Zwitserloot



On Apr 2, 2009, at 13:59, Peter Levart wrote:

> Hello Coiners!
>
> The debate about ARM proposal has calmed down lately and I was  
> thinking
> about it last few days. Initially I submitted a comment that got  
> lost by
> list processor and was about using a "marker" interface as a  
> supertype of
> sigle-method disposable interfaces like this:
>
>
> package java.lang;
>
> public interface AutomaticResource {}
>
>
> ... and for example, retroffiting java.io.Closeable:
>
>
> package java.io;
>
> public interface Closeable extends AutomaticResource {
>    void close() throws IOException;
> }
>
>
> ... this way even the name of the method would not be "coined".  
> There would
> have to be some rules that compiler will enforce to make sure it can
> uniquely identify the method to be called on resource disposal (for  
> example:
> the static type of the resource should not directly or indirectly  
> implement
> or extend two different single-method interfaces marked with
> AutomaticResource marker superinterface).
>
> But then I thought. Why would this language feature even have to be  
> tied to
> a particular interface. The "foreach" loop did take this approach with
> java.lang.Iterable, but this had nothing to do with exceptions and  
> catching
> them and ignoring them silently. A language construct that hides  
> this often
> cited "bad practice" under the carpet is no good!
>
> For example, this snippet of code, written to the proposed ARM spec.,
> submited by Bob Lee in this thread a month ago, asking Neal Gafter to
> demonstrate how the equivalent BGGA version would look like:
>
>  try (InputStream in = new FileInputStream(src);
>      OutputStream out = new FileOutputStream(dest)) {
>    byte[] buf = new byte[8 * 1024];
>    int n;
>    while ((n = in.read(buf)) >= 0)
>      out.write(buf, 0, n);
>  } catch (IOException e) {
>    showDialog("Copy failed.");
>  }
>
> ... is flawed. This code does not guarantee that in the absence of  
> shown
> exception the file has been copied in it's intirety.
>
> Ignoring exception thrown on an InputStream.close() might be  
> desireable, but
> ignoring exception thrown on OutputStream.close() migh mean that you  
> don't
> mind missing writing some final bytes into the file. Closing  
> OutputStream
> should not be part of automatic resource disposal but part of main  
> code
> block. This brings us to the question how is ARM supposed to be able  
> do
> differentiate InputStream from OutputStream if both implement  
> Closeable?
>
> So I thought how to circumvent these two weeknesses. My take on this  
> is
> something like the following:
>
>
>        try (InputStream in = new FileInputStream("inputFile");
>             OutputStream out = new FileOutputStream("outputFile"))
>        {
>          // try body
>        }
>        catch (IOException e)
>        {
>          // catch body
>        }
>        finally (IOException e1 : in.close();
>                 IOException e2 : out.close())
>        {
>          // finally body
>        }
>
>
> ... would be translated to ...
>
>
>        {
>            IOException e1 = null;
>            IOException e2 = null;
>
>            try
>            {
>                InputStream in = new FileInputStream("inputFile");
>
>                try
>                {
>                    OutputStream out = new  
> FileOutputStream("outputFile");
>
>                    try
>                    {
>                        // try body
>                    }
>                    finally
>                    {
>                        try
>                        {
>                            out.close();
>                        }
>                        catch (IOException $$e)
>                        {
>                            e2 = $$e;
>                        }
>                    }
>                }
>                finally
>                {
>                    try
>                    {
>                        in.close();
>                    }
>                    catch (IOException $$e)
>                    {
>                        e1 = $$e;
>                    }
>                }
>            }
>            catch (IOException e)
>            {
>                // catch body
>            }
>            finally
>            {
>                // finally body
>            }
>        }
>
>
>
> ... no special interfaces are used here. The code to dispose of  
> resources is
> clearly visible (it has to be writen, yes, but that also means that  
> it can
> be read, which is a good thing).
>
> The above example is the "full monty" version. The thing to note is  
> that a
> try (...; ...; ...) construct is to be matched by an optional  
> finally (...;
> ...; ...) construct in that both, if the second is specified, must  
> have an
> equal number of semicolons. Each "statement" in the try construct  
> gets it's
> own slot that must be matched by the coresponding slot in the  
> finally (...;
> ...; ...) construct. Any slot in finally construct can be left empty  
> (like
> any of the 3 slots in the for (;;) statement).
>
> The following minimal version is also possible (in this example no  
> catching
> of exceptions on resource cleanup is attempted):
>
> int i, j;
> ReadWriteLock iLock = ...;
> ReadWriteLock jLock = ...;
>
> // ...
>
> try (jLock.readLock().lock(); iLock.writeLock().lock()) {
>  i += j;
> }
> finally (jLock.readLock().unlock(); iLock.writeLock().unlock())
>
>
> ... gets translated to:
>
>
> {
>    jLock.readLock().lock();
>    try {
>      iLock.writeLock().lock();
>      try {
>        i += j;
>      }
>      finally {
>        iLock.writeLock().unlock();
>      }
>    }
>    finally {
>      jLock.readLock().unlock();
>    }
> }
>
>
> All this will have to be formalized. This is just an idea to keep  
> the debate
> going.
>
> Regards, Peter
>



From reinier at zwitserloot.com  Thu Apr  2 05:25:38 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Thu, 2 Apr 2009 14:25:38 +0200
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <64efa1ba0904020515m679910b4n1be9cce0034e474d@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<64efa1ba0904020515m679910b4n1be9cce0034e474d@mail.gmail.com>
Message-ID: <8FD8F030-FE9E-4225-ABD0-40E043B6F1ED@zwitserloot.com>

... or resurrect it by ripping it out of netbeans. I love the idea of  
jackpot and am saddened that it is no longer a stand-alone thing.

  --Reinier Zwitserloot



On Apr 2, 2009, at 14:15, Patrick Wright wrote:

> This would be useful.
>
> One might be able to start by building on the infrastructure in
> Checkstyle, PMD or FindBugs for some of these. I don't know about
> FindBugs, but the other two allow you to write your own matching
> rules. Jackpot could be used as well, but it's no longer maintained as
> an independent project (now part of NB refactoring infrastructure).
> One would have to use a slightly older version of it.
>
>
>
> Patrick
>



From develop4lasu at gmail.com  Thu Apr  2 05:28:13 2009
From: develop4lasu at gmail.com (=?UTF-8?Q?Marek_Kozie=C5=82?=)
Date: Thu, 2 Apr 2009 14:28:13 +0200
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
Message-ID: <28bca0ff0904020528l51d803f2t5a6dc29a8f6a67dc@mail.gmail.com>

2009/4/2 Stephen Colebourne <scolebourne at joda.org>:
> All,
> One possible way I'd like to suggest that the coin evaluation could be
> helped would be to write a script to find out how frequently the
> specific issue comes up in real code.
>
> It should be possible to devise, write and run a script to find the
> number of LOCs affected by many of the proposals. For example:
>
> - strings in switch (find if else on constant strings)
> - multi-catch (find duplicate catch blocks)
> - elvis operator (find ternary and if else defaulting)
> - for each where the iterator remove can be accessed (% of loops that
> access iterator)
> - for each where index is needed (% of loops that use int looping)
> - method and field literals
> - byte and short literals
> and probably many others (I've just listed some proposals I remember)
>
> Ideally, any script would be ASM/BCEL based, but grep style might work too.
>
> I mention all this because I don't have the spare time to write such a
> script, but if you do, then I'm sure we'd all like to run it and
> discuss the results ;-)
>
> Stephen
>
>

We may list all proposals and write opinions & statistics (as we think).

-- 
Pozdrowionka. / Regards.
Lasu aka Marek Kozie?

http://lasu2string.blogspot.com/


From Thomas.Hawtin at Sun.COM  Thu Apr  2 05:29:17 2009
From: Thomas.Hawtin at Sun.COM (Tom Hawtin)
Date: Thu, 02 Apr 2009 13:29:17 +0100
Subject: Proposal: Sameness operators
In-Reply-To: <88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>
	<49D3B1E3.8070109@sun.com>
	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
Message-ID: <49D4AF9D.9090407@sun.com>

Reinier Zwitserloot wrote:
> Why can't we use compareTo and equals?

  * compareTo may well be unreasonably inefficient.
  * equals handles nulls (asymmetrically), compareTo does not
  * equals does test-and-cast (event for generic types - urgh), 
compareTo uses generics
  * equals does not throw ClassCastException, compareTo does (but 
probably shouldn't with generics)

Therefore, new methods please. I'm sure you are aware the whole subject 
of operator overloading in general is a minefield.

> .<. syntax had severe problems that disqualified them - see the  
> archive of this mailing list.

Other than reminding me of the F-language, as a lexical token it is 
perfectly upstanding. The IDE behaviour is a bonus (well I find menus 
popping up as I type almost as annoying as Flash adverts and b***king 
cursors, but you get what I mean).

> The cleanest solution to me remains a cleaning of the slate, so to  

Making a slight change wouldn't be an effective cleaning of the slate, 
IMO. Lots of downsides (not necessarily to you in particular) and not 
enough upsides.


Anyway, I think we all knew which way the wind was blowing on proposals 
like this one from the start of the process.

Tom Hawtin


From reinier at zwitserloot.com  Thu Apr  2 05:36:24 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Thu, 2 Apr 2009 14:36:24 +0200
Subject: Proposal: Sameness operators
In-Reply-To: <4b4f45e00904020524p27741baeo40483e83d71dc768@mail.gmail.com>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>
	<49D3B1E3.8070109@sun.com>
	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
	<4b4f45e00904020524p27741baeo40483e83d71dc768@mail.gmail.com>
Message-ID: <275433EA-A420-42C8-891D-3B0C2629222A@zwitserloot.com>

It's certainly the best backwards compatible alternative that I have  
ever seen, but they are still FAR from ideal.

Take your average programmer who is just reading some code. He first  
sees:

a == b

He rightly assumes this is some sort of equality check, though he  
would probably be surprised to learn that in java, it's object pointer  
identity, not object equality, if a and b are objects. Still, that's  
one sort of (mostly useless) equality, and it is the same as C's  
meaning for this operation, which is not an unimportant benefit,  
because many things in java that look indistinguishable from C code do  
roughly the same thing.


Then he sees:

a (==) b

a few lines down, and now he's just confused and will need to hit the  
books to figure any of this out. I'll grant you that the readability  
of the current situation is not very good either, and I will certainly  
grant that the practical nature of the == operator is very bad indeed  
(In fact, when this comes up in discussion, I always suggest just  
dropping support for object identity altogether in the language, and  
moving that to System.identicalPointers(a, b) or some such. Who needs  
to know about this stuff? Nobody. It's like copying arrays quickly.  
Yes, java should be capable of doing it, but not even close to useful  
enough to warrant an operator!)

Crazy idea: We can get a little closer to ideal by creating a class in  
java lang with useful static methods which you can then import, like:

public static void is(Object x, Object y) {
     if ( x == null ) return y == null;
     return x.equals(y);
}

public static void is(Object x, int y) {
    // Yes, you'd need a few gazillion is methods to cover all the  
primitives on either side, but 1 static import will grab all of them
}

... loads more is methods


Then same with lt, gt, le, ge.

Then you could write:

if ( is(a, b) ) {
   //doStuff
}

Which is a small improvement.

Add an ability to specify 'as infix' in static imports, and you have  
pretty much what we all want without backwards compatibility issues:

import static java.lang.Equality.is infix;

if ( a is b ) {
   //do something
}

I'd consider that a large improvement.


In my perfect world:

':=' is assignment, assignment to a boolean is no longer an expression  
but just a statement to avoid bugs, '=' is equality, and '==' is a  
deprecated syntax for System.identicalPointer, or just '=' for  
primitives/unboxables.

That would no longer be even remotely compatible with java as is,  
though.

  --Reinier Zwitserloot



On Apr 2, 2009, at 14:24, Stephen Colebourne wrote:

> The best alternative operator symbols I've come up with yet are  
> bracketed ones:
>
> a (==) b
> a (<) b
>
> I don't think that the symbols are ideal, but they do look reasonably
> readable, and its way better than .equals().
>
> Do I expect anything to happen here? No. There is a long history of
> "operator overloading"  being frowned on in the Java language. The net
> result is more of an argument to use Groovy, Scala, Fan etc.
>
> Stephen
>
>
> 2009/4/2 Reinier Zwitserloot <reinier at zwitserloot.com>:
>> Why can't we use compareTo and equals?
>>
>> .<. syntax had severe problems that disqualified them - see the
>> archive of this mailing list.
>>
>> 'is' has slightly more precedence than 'eq' and the set 'eq', 'ne',
>> 'lt', and 'le' need 'gt' and 'ge' as well, which makes them rather
>> unwieldy. You can reduce a thing or two by going with just 'eq', 'lt'
>> and 'gt', filling the holes with && and ! as usual (not equal  
>> becomes !
>> (a eq b)), or even a !eq b, but this is all devolving into way too
>> much slap-dash language design unless those become global, non- 
>> context
>> sensitive keywords. I'm okay with that, but Joe Darcy definitely
>> isn't, so that's right out, at least for now.
>>
>> More symbols is similarly unwieldy; there are no appropriate symbols
>> for these operations available. It would be an even greater mistake  
>> to
>> come up with some non-standard and unwieldly syntax for them, such as
>> $=. That way lies perl cartoon-swearing craziness and nobody wants
>> that. Wholesale operator overloading would be far preferable to that
>> situation. ":=" for some sort of inference typing would make some
>> sense and is still free, but that's about where it ends.
>>
>>
>> The cleanest solution to me remains a cleaning of the slate, so to
>> speak, and an explicit demarkation in your source file that you're on
>> 'new java', such as with "source 1.8". With that at the top, "a == b"
>> is compiled the same way as old java's "a == null ? b == null :
>> a.equals(b)" for non-boxable objects (for unboxables and primitives,
>> Unbox everything you can, then do a numeric comparison, or if it's
>> primitive v. object, error), "a < b" and its ilk translate
>> to .compareTo for non-unboxable Comparables, lead to unboxing for
>> unboxables, no change for primitives, and error otherwise. Past
>> mistakes are rectified, blahblahblah. We've been over this before,  
>> I'm
>> sure most coin-dev readers have a good idea about how such a thing
>> would work and the decade+ timerift it would cause between code bases
>> that (stubbornly?) stay with non-new java.
>>
>>
>>
>>  --Reinier Zwitserloot
>> Like it? Tip it!
>> http://tipit.to
>>
>>
>>
>> On Apr 1, 2009, at 20:26, Tom Hawtin wrote:
>>
>>> Christian Fischer wrote:
>>>> These $-operators doesn't seem intuitive to me, but replacing  
>>>> equal-
>>>> calls
>>>> sounds interesting.
>>>>
>>>> Maybe a better solution would be something like this:
>>>> if (a eq b) // equals
>>>> if (a ne b) // not equal
>>>> if (a lt b) // lesser than
>>>> if (a le b) // lesser or equal
>>>
>>> Along with other concerns, four new keywords?! Theoretically they
>>> could
>>> be context sensitive, but then we are boxing in the grammar.
>>>
>>> If something like this were to be done (and let's face it, operator
>>> overloading ain't gonna happen in JDK7), then I think there needs to
>>> be
>>> to changes in fundamental direction of the proposal.
>>>
>>>  * We need new symbols. .<. and the like were proposed in another
>>> similar proposal. So long as the symbol is a sequence of characters
>>> which is not valid in an existing Java program (outside of comments
>>> and
>>> literal strings).
>>>
>>>  * I think it's clear that we can't use Comparable.compareTo and
>>> Object.equals. It requires a new method for each operator.
>>>
>>> Tom
>>>
>>
>>
>>
>



From mthornton at optrak.co.uk  Thu Apr  2 05:48:15 2009
From: mthornton at optrak.co.uk (Mark Thornton)
Date: Thu, 02 Apr 2009 13:48:15 +0100
Subject: Proposal: Sameness operators
In-Reply-To: <49D4AF9D.9090407@sun.com>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>	<49D3B1E3.8070109@sun.com>	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
	<49D4AF9D.9090407@sun.com>
Message-ID: <49D4B40F.2010100@optrak.co.uk>

Tom Hawtin wrote:
> Reinier Zwitserloot wrote:
>   
>> Why can't we use compareTo and equals?
>>     
>
>   * compareTo may well be unreasonably inefficient.
>   * equals handles nulls (asymmetrically), compareTo does not
>   * equals does test-and-cast (event for generic types - urgh), 
> compareTo uses generics
>   * equals does not throw ClassCastException, compareTo does (but 
> probably shouldn't with generics)
>
> Therefore, new methods please. I'm sure you are aware the whole subject 
> of operator overloading in general is a minefield.
>   
a.compareTo(b) == 0 and a.equals(b) are not always the same, sometimes 
for very good reasons. I seem to remember that there is at least one 
such class in the Java platform.

Mark Thornton



From rssh at gradsoft.com.ua  Thu Apr  2 05:56:20 2009
From: rssh at gradsoft.com.ua (rssh at gradsoft.com.ua)
Date: Thu, 2 Apr 2009 15:56:20 +0300 (EEST)
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <64efa1ba0904020515m679910b4n1be9cce0034e474d@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<64efa1ba0904020515m679910b4n1be9cce0034e474d@mail.gmail.com>
Message-ID: <7a2038dee31c8246dde1340615ec8b3a.squirrel@wmail.gradsoft.ua>

> This would be useful.
>
> One might be able to start by building on the infrastructure in
> Checkstyle, PMD or FindBugs for some of these. I don't know about
> FindBugs, but the other two allow you to write your own matching
> rules. Jackpot could be used as well, but it's no longer maintained as
> an independent project (now part of NB refactoring infrastructure).
> One would have to use a slightly older version of it.
>

<shameless plug>

 With JavaChecker infrastructure
(http://redmine.gradsoft.ua/projects/show/javachecker) it's easy to write
declarative rules for counting source-code patterns. For example, rule
for catching exception with empty catch block  look's like:

catch($x,Block(NIL)) -> true
    [ violationDiscovered(EmptyCatchBlock,
                 "empty catch block",$x) ].

And as I know, this is one tool, which contains own Java resolver.

 (jackport can use javacc resolver,  CheckStyle and PMD does not have
resolvers yet; FindBugs work with .class files, so it can check only
compiled stuff).

But I will have time to write rules only during next week-end;
if anybody want to write this rules earlier - I recommend use JavaChecker
as starting point

Reading sources and some introductory article: (for example
http://www.gradsoft.ua/eng/whitepapers/secr2008/secr2008-1.html) must be
enough for starting hacking.

</shameless plug>



>
>
> Patrick
>
>




From david.goodenough at linkchoose.co.uk  Thu Apr  2 06:07:21 2009
From: david.goodenough at linkchoose.co.uk (David Goodenough)
Date: Thu, 2 Apr 2009 14:07:21 +0100
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
Message-ID: <200904021407.24330.david.goodenough@linkchoose.co.uk>

On Thursday 02 April 2009, Stephen Colebourne wrote:
> All,
> One possible way I'd like to suggest that the coin evaluation could be
> helped would be to write a script to find out how frequently the
> specific issue comes up in real code.
>
> It should be possible to devise, write and run a script to find the
> number of LOCs affected by many of the proposals. For example:
>
> - strings in switch (find if else on constant strings)
> - multi-catch (find duplicate catch blocks)
> - elvis operator (find ternary and if else defaulting)
> - for each where the iterator remove can be accessed (% of loops that
> access iterator)
> - for each where index is needed (% of loops that use int looping)
> - method and field literals
> - byte and short literals
> and probably many others (I've just listed some proposals I remember)
>
> Ideally, any script would be ASM/BCEL based, but grep style might work too.
>
> I mention all this because I don't have the spare time to write such a
> script, but if you do, then I'm sure we'd all like to run it and
> discuss the results ;-)
>
> Stephen

As a matter of interest, how would you go about finding the instances of
the problem that my lightweight properties proposal aims to solve, i.e.
field names in strings (binding frameworks, SQL and Criteria strings, and
PropertyChangeSupport events).  You could always just build a list of
fields and look for all strings that contained those string values (they might
be EL strings, or parts of an SQL statement), but I think you would come
up with a large number of false positives.  There are plenty of instances
of this out there, but I am not at all sure how you would count them 
accurately.  

This lack of ability to check them was of course the point of needing a 
solution.

David


From rssh at gradsoft.com.ua  Thu Apr  2 06:10:39 2009
From: rssh at gradsoft.com.ua (rssh at gradsoft.com.ua)
Date: Thu, 2 Apr 2009 16:10:39 +0300 (EEST)
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <28bca0ff0904020528l51d803f2t5a6dc29a8f6a67dc@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<28bca0ff0904020528l51d803f2t5a6dc29a8f6a67dc@mail.gmail.com>
Message-ID: <b1cac5cf489dbd8c889200db29eb11cd.squirrel@wmail.gradsoft.ua>



 Yes, yet one idea - create poll, where each proposal is listed  with link
and rated from -5 to 5
// -5 - I strongly against this in Java; +5 - I strongly for; 0 - neutral.
(by default all is null))  and publish somewhere.
// better different instances for controlled and non-controlled auditory.

It will be interesting.



> 2009/4/2 Stephen Colebourne <scolebourne at joda.org>:
>> All,
>> One possible way I'd like to suggest that the coin evaluation could be
>> helped would be to write a script to find out how frequently the
>> specific issue comes up in real code.
>>
>> It should be possible to devise, write and run a script to find the
>> number of LOCs affected by many of the proposals. For example:
>>
>> - strings in switch (find if else on constant strings)
>> - multi-catch (find duplicate catch blocks)
>> - elvis operator (find ternary and if else defaulting)
>> - for each where the iterator remove can be accessed (% of loops that
>> access iterator)
>> - for each where index is needed (% of loops that use int looping)
>> - method and field literals
>> - byte and short literals
>> and probably many others (I've just listed some proposals I remember)
>>
>> Ideally, any script would be ASM/BCEL based, but grep style might work
>> too.
>>
>> I mention all this because I don't have the spare time to write such a
>> script, but if you do, then I'm sure we'd all like to run it and
>> discuss the results ;-)
>>
>> Stephen
>>
>>
>
> We may list all proposals and write opinions & statistics (as we think).
>
> --
> Pozdrowionka. / Regards.
> Lasu aka Marek Kozie??
>
> http://lasu2string.blogspot.com/
>
>




From mthornton at optrak.co.uk  Thu Apr  2 06:14:24 2009
From: mthornton at optrak.co.uk (Mark Thornton)
Date: Thu, 02 Apr 2009 14:14:24 +0100
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <200904021407.24330.david.goodenough@linkchoose.co.uk>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<200904021407.24330.david.goodenough@linkchoose.co.uk>
Message-ID: <49D4BA30.8070702@optrak.co.uk>

David Goodenough wrote:
> On Thursday 02 April 2009, Stephen Colebourne wrote:
>   
>> All,
>> One possible way I'd like to suggest that the coin evaluation could be
>> helped would be to write a script to find out how frequently the
>> specific issue comes up in real code.
>>
>> It should be possible to devise, write and run a script to find the
>> number of LOCs affected by many of the proposals. For example:
>>
>> - strings in switch (find if else on constant strings)
>> - multi-catch (find duplicate catch blocks)
>> - elvis operator (find ternary and if else defaulting)
>> - for each where the iterator remove can be accessed (% of loops that
>> access iterator)
>> - for each where index is needed (% of loops that use int looping)
>> - method and field literals
>> - byte and short literals
>> and probably many others (I've just listed some proposals I remember)
>>
>> Ideally, any script would be ASM/BCEL based, but grep style might work too.
>>
>> I mention all this because I don't have the spare time to write such a
>> script, but if you do, then I'm sure we'd all like to run it and
>> discuss the results ;-)
>>
>> Stephen
>>     
>
> As a matter of interest, how would you go about finding the instances of
> the problem that my lightweight properties proposal aims to solve, i.e.
>   
There are a number of types of change which are hard to verify or 
quantify using existing code. For example escape analysis may fail to 
show benefits from eliminating allocation because the programmers have 
already done it manually. In particular they might have used integer 
loops instead of an iterator when looping over an ArrayList. I still 
have quite a few old style loops simply because there hasn't been a 
sufficiently good reason to change them yet.

Mark Thornton



From rssh at gradsoft.com.ua  Thu Apr  2 06:14:44 2009
From: rssh at gradsoft.com.ua (rssh at gradsoft.com.ua)
Date: Thu, 2 Apr 2009 16:14:44 +0300 (EEST)
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <200904021407.24330.david.goodenough@linkchoose.co.uk>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<200904021407.24330.david.goodenough@linkchoose.co.uk>
Message-ID: <2d40714ad6407ff97935bcf5acf6b1fc.squirrel@wmail.gradsoft.ua>

> As a matter of interest, how would you go about finding the instances of
> the problem that my lightweight properties proposal aims to solve, i.e.

 .... afraid none = scripts will  works only for simple proposals.






From markmahieu at googlemail.com  Thu Apr  2 06:25:15 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Thu, 2 Apr 2009 14:25:15 +0100
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
Message-ID: <cf90c1f10904020625s49088dbbv11685b9811b8c14a@mail.gmail.com>

Wow.

http://www.geekherocomic.com/comics-highres/2009-02-25-coding-overkill.png


Here are the important bits from my quick hack.  Took under half an hour to
get it finding cases where Auto-assignment Parameters would and wouldn't
work across large source trees.

Of course, javac makes much more than parsing available if you need it...



import com.sun.tools.javac.file.JavacFileManager;
import com.sun.tools.javac.parser.JavacParser;
import com.sun.tools.javac.parser.ParserFactory;
import com.sun.tools.javac.tree.TreeScanner;
import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
import com.sun.tools.javac.tree.JCTree.JCMethodDecl;
import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.util.List;

...

// create a TreeScanner to do your analysis
TreeScanner scanner = new TreeScanner() {

@Override
public void visitMethodDef(JCMethodDecl tree) {
 // look at a method's parameters
for (List<JCVariableDecl> l = params; l.nonEmpty(); l = l.tail) {
JCVariableDecl param = l.head;
 // examine param or whatever
}
 // continue recursively scanning the method body etc
super.visitMethodDef(tree);
}
};

...

Context context = new Context();
JavacFileManager.preRegister(context);
ParserFactory factory = ParserFactory.instance(context);

String sourceCode = readSourceFromFile(...);

JavacParser parser = (JavacParser) factory.newParser(sourceCode, false,
false, false);
JCCompilationUnit cu = parser.parseCompilationUnit();

// do your analysis
scanner.scan(cu);


From misterm at gmail.com  Thu Apr  2 06:34:05 2009
From: misterm at gmail.com (Michael Nascimento)
Date: Thu, 2 Apr 2009 10:34:05 -0300
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <cf90c1f10904020625s49088dbbv11685b9811b8c14a@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<cf90c1f10904020625s49088dbbv11685b9811b8c14a@mail.gmail.com>
Message-ID: <389b9d740904020634u321941d0l9c61c56d9d7ea295@mail.gmail.com>

Using JDK 6, you can write an annotation processor for all sources
that uses the Tree API for that.

Regards,
Michael Nascimento Santos
https://genesis.dev.java.net/
https://jsr-310.dev.java.net/

On Thu, Apr 2, 2009 at 10:25 AM, Mark Mahieu <markmahieu at googlemail.com> wrote:
> Wow.
>
> http://www.geekherocomic.com/comics-highres/2009-02-25-coding-overkill.png
>
>
> Here are the important bits from my quick hack. ?Took under half an hour to
> get it finding cases where Auto-assignment Parameters would and wouldn't
> work across large source trees.
>
> Of course, javac makes much more than parsing available if you need it...
>
>
>
> import com.sun.tools.javac.file.JavacFileManager;
> import com.sun.tools.javac.parser.JavacParser;
> import com.sun.tools.javac.parser.ParserFactory;
> import com.sun.tools.javac.tree.TreeScanner;
> import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
> import com.sun.tools.javac.tree.JCTree.JCMethodDecl;
> import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
> import com.sun.tools.javac.util.Context;
> import com.sun.tools.javac.util.List;
>
> ...
>
> // create a TreeScanner to do your analysis
> TreeScanner scanner = new TreeScanner() {
>
> @Override
> public void visitMethodDef(JCMethodDecl tree) {
> ?// look at a method's parameters
> for (List<JCVariableDecl> l = params; l.nonEmpty(); l = l.tail) {
> JCVariableDecl param = l.head;
> ?// examine param or whatever
> }
> ?// continue recursively scanning the method body etc
> super.visitMethodDef(tree);
> }
> };
>
> ...
>
> Context context = new Context();
> JavacFileManager.preRegister(context);
> ParserFactory factory = ParserFactory.instance(context);
>
> String sourceCode = readSourceFromFile(...);
>
> JavacParser parser = (JavacParser) factory.newParser(sourceCode, false,
> false, false);
> JCCompilationUnit cu = parser.parseCompilationUnit();
>
> // do your analysis
> scanner.scan(cu);
>
>


From markmahieu at googlemail.com  Thu Apr  2 06:47:26 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Thu, 2 Apr 2009 14:47:26 +0100
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <389b9d740904020634u321941d0l9c61c56d9d7ea295@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<cf90c1f10904020625s49088dbbv11685b9811b8c14a@mail.gmail.com>
	<389b9d740904020634u321941d0l9c61c56d9d7ea295@mail.gmail.com>
Message-ID: <cf90c1f10904020647q37d10339o99f53d95da2d0f6d@mail.gmail.com>

Yep, which is a better option if the code is going to be more than a quick
throwaway.
The advantage with using the javac versions of those types is that you get
familiarity with other APIs you need to interact with when building an
actual prototype...
Mark


2009/4/2 Michael Nascimento <misterm at gmail.com>

> Using JDK 6, you can write an annotation processor for all sources
> that uses the Tree API for that.
>
> Regards,
> Michael Nascimento Santos
> https://genesis.dev.java.net/
> https://jsr-310.dev.java.net/
>
> On Thu, Apr 2, 2009 at 10:25 AM, Mark Mahieu <markmahieu at googlemail.com>
> wrote:
> > Wow.
> >
> >
> http://www.geekherocomic.com/comics-highres/2009-02-25-coding-overkill.png
> >
> >
> > Here are the important bits from my quick hack.  Took under half an hour
> to
> > get it finding cases where Auto-assignment Parameters would and wouldn't
> > work across large source trees.
> >
> > Of course, javac makes much more than parsing available if you need it...
> >
> >
> >
> > import com.sun.tools.javac.file.JavacFileManager;
> > import com.sun.tools.javac.parser.JavacParser;
> > import com.sun.tools.javac.parser.ParserFactory;
> > import com.sun.tools.javac.tree.TreeScanner;
> > import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
> > import com.sun.tools.javac.tree.JCTree.JCMethodDecl;
> > import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
> > import com.sun.tools.javac.util.Context;
> > import com.sun.tools.javac.util.List;
> >
> > ...
> >
> > // create a TreeScanner to do your analysis
> > TreeScanner scanner = new TreeScanner() {
> >
> > @Override
> > public void visitMethodDef(JCMethodDecl tree) {
> >  // look at a method's parameters
> > for (List<JCVariableDecl> l = params; l.nonEmpty(); l = l.tail) {
> > JCVariableDecl param = l.head;
> >  // examine param or whatever
> > }
> >  // continue recursively scanning the method body etc
> > super.visitMethodDef(tree);
> > }
> > };
> >
> > ...
> >
> > Context context = new Context();
> > JavacFileManager.preRegister(context);
> > ParserFactory factory = ParserFactory.instance(context);
> >
> > String sourceCode = readSourceFromFile(...);
> >
> > JavacParser parser = (JavacParser) factory.newParser(sourceCode, false,
> > false, false);
> > JCCompilationUnit cu = parser.parseCompilationUnit();
> >
> > // do your analysis
> > scanner.scan(cu);
> >
> >
>
>


From david.goodenough at linkchoose.co.uk  Thu Apr  2 06:28:25 2009
From: david.goodenough at linkchoose.co.uk (David Goodenough)
Date: Thu, 2 Apr 2009 14:28:25 +0100
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <2d40714ad6407ff97935bcf5acf6b1fc.squirrel@wmail.gradsoft.ua>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<200904021407.24330.david.goodenough@linkchoose.co.uk>
	<2d40714ad6407ff97935bcf5acf6b1fc.squirrel@wmail.gradsoft.ua>
Message-ID: <200904021428.26371.david.goodenough@linkchoose.co.uk>

On Thursday 02 April 2009, rssh at gradsoft.com.ua wrote:
> > As a matter of interest, how would you go about finding the instances of
> > the problem that my lightweight properties proposal aims to solve, i.e.
>
>  .... afraid none = scripts will  works only for simple proposals.

Well I suppose a first pass would simply be to count all occurences of
String values who's value matched a field name, but how deep do you
go looking for fields - probably just in the user's code not the libraries
even though you would then miss lots of PropertyChange fires and
all the named properties inside Swing. 

Could your code do the simple string == fieldname scan?  That would
under-count, but it would be a start.

David


From rssh at gradsoft.com.ua  Thu Apr  2 07:18:26 2009
From: rssh at gradsoft.com.ua (rssh at gradsoft.com.ua)
Date: Thu, 2 Apr 2009 17:18:26 +0300 (EEST)
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <200904021428.26371.david.goodenough@linkchoose.co.uk>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<200904021407.24330.david.goodenough@linkchoose.co.uk>
	<2d40714ad6407ff97935bcf5acf6b1fc.squirrel@wmail.gradsoft.ua>
	<200904021428.26371.david.goodenough@linkchoose.co.uk>
Message-ID: <69bcb3eed8382ed8d1ca39bc49797501.squirrel@wmail.gradsoft.ua>

> On Thursday 02 April 2009, rssh at gradsoft.com.ua wrote:
>> > As a matter of interest, how would you go about finding the instances
>> of
>> > the problem that my lightweight properties proposal aims to solve,
>> i.e.
>>
>>  .... afraid none = scripts will  works only for simple proposals.
>
> Well I suppose a first pass would simply be to count all occurences of
> String values who's value matched a field name, but how deep do you
> go looking for fields - probably just in the user's code not the libraries
> even though you would then miss lots of PropertyChange fires and
> all the named properties inside Swing.
>
> Could your code do the simple string == fieldname scan?  That would
> under-count, but it would be a start.
>

Yes, this is possible. But if we have class X with field "fx", than String
"fx" somewhere in class Y - how count this ?
 This can be undercount or overcount.
Knowledge about Y import (i. e. X is accessible from X or not) also give
us nothing, because exists possibility, that this is something generic in
Y.

So, we can receive some counts and they would have some correlation with
property access, but all with some level of 'vagueness' in interpretation.

> David
>
>




From david.goodenough at linkchoose.co.uk  Thu Apr  2 07:29:27 2009
From: david.goodenough at linkchoose.co.uk (David Goodenough)
Date: Thu, 2 Apr 2009 15:29:27 +0100
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <69bcb3eed8382ed8d1ca39bc49797501.squirrel@wmail.gradsoft.ua>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<200904021428.26371.david.goodenough@linkchoose.co.uk>
	<69bcb3eed8382ed8d1ca39bc49797501.squirrel@wmail.gradsoft.ua>
Message-ID: <200904021529.29938.david.goodenough@linkchoose.co.uk>

On Thursday 02 April 2009, rssh at gradsoft.com.ua wrote:
> > On Thursday 02 April 2009, rssh at gradsoft.com.ua wrote:
> >> > As a matter of interest, how would you go about finding the instances
> >>
> >> of
> >>
> >> > the problem that my lightweight properties proposal aims to solve,
> >>
> >> i.e.
> >>
> >>  .... afraid none = scripts will  works only for simple proposals.
> >
> > Well I suppose a first pass would simply be to count all occurences of
> > String values who's value matched a field name, but how deep do you
> > go looking for fields - probably just in the user's code not the
> > libraries even though you would then miss lots of PropertyChange fires
> > and all the named properties inside Swing.
> >
> > Could your code do the simple string == fieldname scan?  That would
> > under-count, but it would be a start.
>
> Yes, this is possible. But if we have class X with field "fx", than String
> "fx" somewhere in class Y - how count this ?
>  This can be undercount or overcount.
> Knowledge about Y import (i. e. X is accessible from X or not) also give
> us nothing, because exists possibility, that this is something generic in
> Y.
>
> So, we can receive some counts and they would have some correlation with
> property access, but all with some level of 'vagueness' in interpretation.
It would be a start I suppose.  It would probably overcount, but then this
test is also missing all the field names embedded in Criteria or similar APIs
and in SQL and related beasts.

David
>
> > David




From peter.levart at gmail.com  Thu Apr  2 07:33:49 2009
From: peter.levart at gmail.com (Peter Levart)
Date: Thu, 2 Apr 2009 16:33:49 +0200
Subject: Proposal: Automatic Resource Management
In-Reply-To: <370F8DB1-A374-43B4-9F83-ABCD5A925D93@zwitserloot.com>
References: <aad309390904020459m6d85ea6aqa8ade12dbab67399@mail.gmail.com>
	<370F8DB1-A374-43B4-9F83-ABCD5A925D93@zwitserloot.com>
Message-ID: <aad309390904020733v2b3527ffg2d00783bc0f904af@mail.gmail.com>

I apologise! The code snipped submitted by Bob Lee is not flawed at all as I
have suggested in my previous message. I did not read ARM specification
correctly.

Nevertheless with increasing number of resources managed by a single ARM
construct, the track of which method has thrown exception and why is lost.
This is also true if to many statements that can throw the same exception
are written in a single try block.

Ideally all thrown exceptions should be individually accessible together
within a single block (being catch or finally block I don't know which).
This way any additional logic can act on the whole failure context.

So in this respect my proposed construct is no better because it separates
exception thrown in initialization and try block from exceptions thrown in
clean-up code which are accessible in finally block.

I understand that sometimes one just wants to be passed a single variable
that holds the "most meaningful" exception thrown among several and that is
what ARM proposal is trying to solve. A programmer using ARM construct will
have to evaluate whether ARM is the correct tool for the particular problem
and not blindly accept it because it is the correct tool for most problems
(and it is so easy to use).

On the other hand the try-catch-finally statement as we have now in Java is
always the right tool (if used correctly) but it unfortunately can too
easily be used incorrectly.

Regards, Peter


From reinier at zwitserloot.com  Thu Apr  2 08:18:25 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Thu, 2 Apr 2009 17:18:25 +0200
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <b1cac5cf489dbd8c889200db29eb11cd.squirrel@wmail.gradsoft.ua>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<28bca0ff0904020528l51d803f2t5a6dc29a8f6a67dc@mail.gmail.com>
	<b1cac5cf489dbd8c889200db29eb11cd.squirrel@wmail.gradsoft.ua>
Message-ID: <31AB3E69-CCE7-4134-95C9-4DB5BF6C9281@zwitserloot.com>

Polling has many, many problems associated with it:

1. It does not reliably measure impact. Let's say generics gets a 9.0  
in the polls, and the foreach loop gets only an 8.0. The right answer  
is to implement foreach, eventhough it scored lower. It's easier and  
has less impact. implementing difficulty can be decided by an expert  
group, but there's also the concept of impact.

A nice case in point: Almost everyone rated operator support for  
BigDecimal and BigInteger as very low in Stephen Colebourne's polls,  
but is that reflective? I don't think so. It's just the one with the  
lowest impact - no body cares about that a lot, and some care about it  
not at all. It is, however, hard to see how operator support for  
BigDecimal/BigInteger can break, well, anything. The value of any  
proposal is its positive impact divided by its negative impact, and  
dividing by a very small number gives you a very large number.

2. Not all know about intricacies. For example, with generics, I bet  
many who vocally supported them did not know the details about  
reification, the sheer complexity of co/contra-variance (which just  
cannot be simplified, the core concept is difficult, period),  
etcetera.  By not being aware of the weight put on future expansions  
and patchy stopgaps in the proposal itself, some proposals that are  
technically (but not obviously) complex get an unfairly inflated poll  
score.



Perhaps a fairer way would be to first reduce the list to a manageable  
number, and then to poll, but only amongst those who have attempted to  
read and fully grok all proposals on the list, and can be expected to  
know enough repercussions to make a fair analysis, and to poll not  
just on 'how much would you like this in java?' but also on 'how much  
would you NOT like this in java?' - in order to give the simpler stuff  
like e.g. operators for BigDecimal/Integer a fighting chance. How do  
you determine that someone is both skilled enough to understand AND  
has attempted to grok all proposals on the short-list? I have no idea.


  --Reinier Zwitserloot



On Apr 2, 2009, at 15:10, rssh at gradsoft.com.ua wrote:

>
>
> Yes, yet one idea - create poll, where each proposal is listed  with  
> link
> and rated from -5 to 5
> // -5 - I strongly against this in Java; +5 - I strongly for; 0 -  
> neutral.
> (by default all is null))  and publish somewhere.
> // better different instances for controlled and non-controlled  
> auditory.
>
> It will be interesting.
>
>
>
>> 2009/4/2 Stephen Colebourne <scolebourne at joda.org>:
>>> All,
>>> One possible way I'd like to suggest that the coin evaluation  
>>> could be
>>> helped would be to write a script to find out how frequently the
>>> specific issue comes up in real code.
>>>
>>> It should be possible to devise, write and run a script to find the
>>> number of LOCs affected by many of the proposals. For example:
>>>
>>> - strings in switch (find if else on constant strings)
>>> - multi-catch (find duplicate catch blocks)
>>> - elvis operator (find ternary and if else defaulting)
>>> - for each where the iterator remove can be accessed (% of loops  
>>> that
>>> access iterator)
>>> - for each where index is needed (% of loops that use int looping)
>>> - method and field literals
>>> - byte and short literals
>>> and probably many others (I've just listed some proposals I  
>>> remember)
>>>
>>> Ideally, any script would be ASM/BCEL based, but grep style might  
>>> work
>>> too.
>>>
>>> I mention all this because I don't have the spare time to write  
>>> such a
>>> script, but if you do, then I'm sure we'd all like to run it and
>>> discuss the results ;-)
>>>
>>> Stephen
>>>
>>>
>>
>> We may list all proposals and write opinions & statistics (as we  
>> think).
>>
>> --
>> Pozdrowionka. / Regards.
>> Lasu aka Marek Kozie??
>>
>> http://lasu2string.blogspot.com/
>>
>>
>
>
>



From Joe.Darcy at Sun.COM  Thu Apr  2 08:27:56 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Thu, 02 Apr 2009 08:27:56 -0700
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <31AB3E69-CCE7-4134-95C9-4DB5BF6C9281@zwitserloot.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<28bca0ff0904020528l51d803f2t5a6dc29a8f6a67dc@mail.gmail.com>
	<b1cac5cf489dbd8c889200db29eb11cd.squirrel@wmail.gradsoft.ua>
	<31AB3E69-CCE7-4134-95C9-4DB5BF6C9281@zwitserloot.com>
Message-ID: <49D4D97C.5090808@sun.com>

Reinier Zwitserloot wrote:
> Polling has many, many problems associated with it:
>   

I will treat any polling information as strictly informative and in no 
way binding on the decisions that get made.

Polling is the limit case of design by committee and not well-suited to 
technical decisions.

-Joe



From rssh at gradsoft.com.ua  Thu Apr  2 09:09:28 2009
From: rssh at gradsoft.com.ua (rssh at gradsoft.com.ua)
Date: Thu, 2 Apr 2009 19:09:28 +0300 (EEST)
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <31AB3E69-CCE7-4134-95C9-4DB5BF6C9281@zwitserloot.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<28bca0ff0904020528l51d803f2t5a6dc29a8f6a67dc@mail.gmail.com>
	<b1cac5cf489dbd8c889200db29eb11cd.squirrel@wmail.gradsoft.ua>
	<31AB3E69-CCE7-4134-95C9-4DB5BF6C9281@zwitserloot.com>
Message-ID: <d8e827e34ea76f830c27ec529a882e57.squirrel@wmail.gradsoft.ua>

> Polling has many, many problems associated with it:
>

 yes.  But we have no other ways to know 'meaning of mass'. I. e. 'design
by poll' is not good idea, but 'design without any information from real
word' is not good idea also.

It's well-known problem in sociology, where, unlike computer science, we
 have no correct instruments at all. Exists some 'non-direct' ways
 to know how correct is poll: controlled auditories, same poll in different
cases, but all this is not panacea.

> 1. It does not reliably measure impact. Let's say generics gets a 9.0
> in the polls, and the foreach loop gets only an 8.0. The right answer
> is to implement foreach, eventhough it scored lower. It's easier and
> has less impact. implementing difficulty can be decided by an expert
> group, but there's also the concept of impact.
>

 Yes. I think all understand this.
// btw, near all proposals in project coin are easy implementable.

> A nice case in point: Almost everyone rated operator support for
> BigDecimal and BigInteger as very low in Stephen Colebourne's polls,
> but is that reflective? I don't think so. It's just the one with the
> lowest impact - no body cares about that a lot, and some care about it
> not at all. It is, however, hard to see how operator support for
> BigDecimal/BigInteger can break, well, anything. The value of any
> proposal is its positive impact divided by its negative impact, and
> dividing by a very small number gives you a very large number.
>

I also have question to Stephen polls: i. e. I can't understand why
multiline strings rated so low.  Anybody, who works with databases
 know, that analyzing query plan or copy non-trivial query test
 in java is a big pain, and most of Java project in corporate sector use 
non-trivial sql queris".
  Only one answer, which I can suggest - that auditory which attend Java
conferences does not reflect auditory of Java users: most of Java
conferences attenders do system programming or research and have nothing
with most of  database projects which is not so interesting and rare
have academics interest.
  To verify this, possible repeat his poll on some programmer event, which
is not so academics.


> 2. Not all know about intricacies. For example, with generics, I bet
> many who vocally supported them did not know the details about
> reification, the sheer complexity of co/contra-variance (which just
> cannot be simplified, the core concept is difficult, period),
> etcetera.  By not being aware of the weight put on future expansions
> and patchy stopgaps in the proposal itself, some proposals that are
> technically (but not obviously) complex get an unfairly inflated poll
> score.
>

Filtration by proposal size, as I know, already was done.

>
>
> Perhaps a fairer way would be to first reduce the list to a manageable
> number, and then to poll, but only amongst those who have attempted to
> read and fully grok all proposals on the list, and can be expected to

 Or just does not touch proposals, which was not readed.
(mark as 0, 'neutral')


> know enough repercussions to make a fair analysis, and to poll not
> just on 'how much would you like this in java?' but also on 'how much
> would you NOT like this in java?' - in order to give the simpler stuff
> like e.g. operators for BigDecimal/Integer a fighting chance. How do

 Yes.

> you determine that someone is both skilled enough to understand AND
> has attempted to grok all proposals on the short-list? I have no idea.
>

'Skilled enough', sorry, I think that people, which skilled enough prefer
haskell and will poll for haskell-like features, which is not ordinary
Java programmer want ;)

Also will be wery interested difference between this audience (subscribers
of the list) and general audience of Java programmers.

Note, that I does not propose use polls as one and only one criteria. I
just tell that see result of such poll will be interest.

// btw - from other side, all this activity is overkill, I can suggest,
// that  accepted proposals would be exactly same, which was listed in
// project-coin description (before coin was started)
//     http://blogs.sun.com/darcy/entry/project_coin
//   +ARM  +jsr292  and ...  it's already 6, which is more than 5 :)

I. e. doing project coin with external auditory  was a 'Sun system error',
I guess; if they want some feedback from community, correct way was at
first implement own stuff, than ask community for something new ;)


>
>   --Reinier Zwitserloot
>
>
>
> On Apr 2, 2009, at 15:10, rssh at gradsoft.com.ua wrote:
>
>>
>>
>> Yes, yet one idea - create poll, where each proposal is listed  with
>> link
>> and rated from -5 to 5
>> // -5 - I strongly against this in Java; +5 - I strongly for; 0 -
>> neutral.
>> (by default all is null))  and publish somewhere.
>> // better different instances for controlled and non-controlled
>> auditory.
>>
>> It will be interesting.
>>
>>
>>
>>> 2009/4/2 Stephen Colebourne <scolebourne at joda.org>:
>>>> All,
>>>> One possible way I'd like to suggest that the coin evaluation
>>>> could be
>>>> helped would be to write a script to find out how frequently the
>>>> specific issue comes up in real code.
>>>>
>>>> It should be possible to devise, write and run a script to find the
>>>> number of LOCs affected by many of the proposals. For example:
>>>>
>>>> - strings in switch (find if else on constant strings)
>>>> - multi-catch (find duplicate catch blocks)
>>>> - elvis operator (find ternary and if else defaulting)
>>>> - for each where the iterator remove can be accessed (% of loops
>>>> that
>>>> access iterator)
>>>> - for each where index is needed (% of loops that use int looping)
>>>> - method and field literals
>>>> - byte and short literals
>>>> and probably many others (I've just listed some proposals I
>>>> remember)
>>>>
>>>> Ideally, any script would be ASM/BCEL based, but grep style might
>>>> work
>>>> too.
>>>>
>>>> I mention all this because I don't have the spare time to write
>>>> such a
>>>> script, but if you do, then I'm sure we'd all like to run it and
>>>> discuss the results ;-)
>>>>
>>>> Stephen
>>>>
>>>>
>>>
>>> We may list all proposals and write opinions & statistics (as we
>>> think).
>>>
>>> --
>>> Pozdrowionka. / Regards.
>>> Lasu aka Marek Kozie?????
>>>
>>> http://lasu2string.blogspot.com/
>>>
>>>
>>
>>
>>
>
>




From reinier at zwitserloot.com  Thu Apr  2 09:15:22 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Thu, 2 Apr 2009 18:15:22 +0200
Subject: Proposal: Sameness operators
In-Reply-To: <49D4B40F.2010100@optrak.co.uk>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>	<49D3B1E3.8070109@sun.com>	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
	<49D4AF9D.9090407@sun.com> <49D4B40F.2010100@optrak.co.uk>
Message-ID: <27F0EA9D-8936-4330-A5FE-97F522C290F0@zwitserloot.com>

The argument that .compareTo should not be used because it isn't  
entirely congruent with either the meaning of .equals() or the  
meanings of all the comparison operators (from == to <) on the  
primitives, just doesn't hold water, for this simple reason:

They make absolutely no sense now, either, and nobody cares about that.


Here's some fun facts (all asserts are true):

int x = 0/0; //ArithmeticException
double x = 0/0.0; //okay, x = NaN
double y = 0/0.0;

assert x != y;
assert ! (x == y);
assert Double.valueOf(x).equals(Double.valueOf(y)); //WTF!
assert Double.valueOf(x).equals(y); //WTF!

Clearly, equals is fundamentally broken. We need a new equals! Oh no!

assert ! (x < y);
assert ! (x <= y);
assert Double.valueOf(x).compareTo(y) == 0; //WTF!

So, compareTo is broken as well. Just like equals is.

assert x < "foo"; //Compiler Error: Cant compare those two.
assert Double.valueOf(x).compareTo("foo"); //With java 1.4: Runtime  
error.
assert Double.valueOf(x).compareTo("foo"); //With java 1.5+: Compile  
time error.

A compiler error is better, but these two results certainly are  
consistent. In fact, in java 1.5+, you DO get a compiler error.

So, if x < "foo" would be rewritten to the version below that after  
comparison operator support is added that uses compareTo, you get  
roughly the same situation: A compiler error that tells you that the  
compiler didn't expect a String there. The exact text of the error is  
slightly different, but other than that, it's the same. Why is this a  
problem?



The fix to me seems relatively simple:

1. Anything that is legal now needs to stay legal. I would write down  
the rules for this, except they are totally nuts, as the above samples  
show. So, just do whatever java 6 does for everything that would have  
been legal in 6. In particular, this involves unboxing both sides if  
both sides can be unboxed. And unbox one side if the other side is a  
numeric primitive. Yes, this leads to crazy puzzlers, such as:

Double x = Double.valueOf(Double.NaN);
double y = 0;
if ( x != y && !(x < y) && !(x > y) ) System.out.println("This line  
prints? Whoa!");

But that's what we're stuck with. Unless Lovatt's and my crazy idea of  
breaking backwards compatibility with an explicit source keyword is  
implemented, this craziness can't go away, we're stuck with it.

2. First unbox whatever can be unboxed, then continue to:

3. If either LHS or RHS implements Comparable, we'll use that. Note  
that primitives do not implement Comparable. Comparison operations  
between primitives are hardcoded into the JLS spec. If both sides do  
implement Comparable, LHS wins. If only the RHS does, the order is  
mathematically reversed (a > b becomes b < a). If the winning HS is  
willing to take Number according to the generics bound of Comparable  
(which means RAW types *DO*, as they take all objects), then numeric  
primitives are boxed. If neither side implements Comparable, compiler  
error. If a side does, but the type of the other side isn't compatible  
with Comparable's bound, or is a non-numeric primitive (boolean - char  
is actually numeric, because this didn't look quite enough like a  
Salvador Dali painting yet, go figure) you get a compile-time error,  
even if the other way around would have worked.

4. BigDecimal and BigInteger are changed to implement  
Comparable<Number> instead. The fact that they currently don't is  
something I don't really understand would consider filing as a bug if  
I worked more with mixed BI/BD and primitives math. By doing this,  
something like:

5 < new BigInteger("10") would work out the way you expect it to (that  
would return 'true').


BI/BD's comparison methods can't just convert the incoming primitive  
to a BI/BD, because NaN and the infinities don't convert, yet the  
answer to this expression:

Double.NEGATIVE_INFINITY < BigInteger.ZERO

should clearly be true. The above plan can make that happen by adding  
more logic to BI/BD's compareTo methods.



The reason Double and company need to unbox is because their  
implementations of compareTo can then stay blissfully unaware of BI  
and BD's existence. There's a problem if you attempt to compare 2  
numeric entities that aren't hardcoded into the JVM, but I don't think  
a perfect solution is possible here.

This proposal is not entirely consistent with the primitive's compare  
operators, but attempting to be consistent with the current mess that  
is comparison operators between primitives is not a goal that we  
should aspire to, IMO. The concept of 'I'll give you an answer if  
there is a mathematical answer, and if there isn't, I will give you a  
compile-time error if I can, and a runtime error otherwise' seems  
perfect to me. That's compareTo's current semantics, so, lucky us!


NB: Attempting to integrate equality into compareTo is probably a bad  
idea, eventhough we are stuck with some funny puzzlers where equality  
and comparison clearly aren't consistent. The real problem is that  
numeric equality is just different from object equality (numerically,  
NaN is not equal to NaN, but as objects, they are, and asking if apple  
== pear makes no sense numerically, but as objects, there's a logical  
answer: No, they aren't). I don't see us getting out of that one.  
Possibly use <> as an operator that specifically means: Not  
Numerically equal, and !<> as numerically equal. Yeah, that doesn't  
really look too readable to me either.


  --Reinier Zwitserloot



On Apr 2, 2009, at 14:48, Mark Thornton wrote:

> Tom Hawtin wrote:
>> Reinier Zwitserloot wrote:
>>
>>> Why can't we use compareTo and equals?
>>>
>>
>>  * compareTo may well be unreasonably inefficient.
>>  * equals handles nulls (asymmetrically), compareTo does not
>>  * equals does test-and-cast (event for generic types - urgh),  
>> compareTo uses generics
>>  * equals does not throw ClassCastException, compareTo does (but  
>> probably shouldn't with generics)
>>
>> Therefore, new methods please. I'm sure you are aware the whole  
>> subject of operator overloading in general is a minefield.
>>
> a.compareTo(b) == 0 and a.equals(b) are not always the same,  
> sometimes for very good reasons. I seem to remember that there is at  
> least one such class in the Java platform.
>
> Mark Thornton
>



From develop4lasu at gmail.com  Thu Apr  2 10:34:24 2009
From: develop4lasu at gmail.com (=?UTF-8?Q?Marek_Kozie=C5=82?=)
Date: Thu, 2 Apr 2009 19:34:24 +0200
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <d8e827e34ea76f830c27ec529a882e57.squirrel@wmail.gradsoft.ua>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<28bca0ff0904020528l51d803f2t5a6dc29a8f6a67dc@mail.gmail.com>
	<b1cac5cf489dbd8c889200db29eb11cd.squirrel@wmail.gradsoft.ua>
	<31AB3E69-CCE7-4134-95C9-4DB5BF6C9281@zwitserloot.com>
	<d8e827e34ea76f830c27ec529a882e57.squirrel@wmail.gradsoft.ua>
Message-ID: <28bca0ff0904021034w40f2c5d1nfa8b574e99f61a11@mail.gmail.com>

As pool I would suggest, while [yes/no] do not give any knowledge:

Problem:
-> Analyzed(0~5~6) // did you took much time to analyze it? // (0 =
no) (5 = a lot)
-> IHadSuchProblem(0~5~6) // how often you had such problem ? (0 = no)
(5 = often) (6 = almost all time)
-> IWouldUseIt(0~5~6) // would you use in new JDK ? (0 = no) (5= a lot)
-> Problems(0~5~6[,sample]) // like: to many interactions, to
complicated, potential problems .... (0 = none) (5 = a lot)
-> OtherSolutionWouldSolveProblem(0~5~6[,SolutionName]) // do you know
other solution (0 = do not know any) (5 = in 100%) (6 = 100% and would
be better)
-> SolutionNotComplete(0~5~6[,description]) // what is missing in
yours opinion? (0 = none) (5 = incomplete)
-> Except(0~5~6,what) // some parts of this solution should be removed
(0 = none)
-> Extend(0~5~6,what) // this soultion need to be extended to work
correctly (0 = no need) (5 = to weak to solve problem at current
version)

where (in YOUR opinion):
0 : none  ~  5 : much
6 : very much

     Like:


[Marek Kozie?]
StringInSwitch:
-> Analyzed(5)
-> IHadSuchProblem(3)
-> IWouldUseIt(1)
-> Problems(3)
-> OtherSolutionWouldSolveProblem(6,enum)
-> SolutionNotComplete(5,onlyForStaticData)
-> Exclude(0)
-> Extend(6,dynamicData comparator)
NextSolution/Proposal:
...


Explanation:

-> Analyzed(5) : I took a lot of time to analyze it
-> IHadSuchProblem(3) : i had it some times
-> IWouldUseIt(1) : I think this solution have no much use for me (to
weak = no dynamic data).
-> Problems(3) : would cause bad style
-> OtherSolutionWouldSolveProblem(6,enum) : can have all those and more
-> SolutionNotComplete(5,onlyForStaticData) :
-> Exclude(0) : nothing to exclude
-> Extend(6,dynamicData asymetricComparator) : should be extended with
... and It would help a lot

This could be parsed to bring some critical informations (like
potential problem).



-- 
Pozdrowionka. / Regards.
Lasu aka Marek Kozie?

http://lasu2string.blogspot.com/


From mthornton at optrak.co.uk  Thu Apr  2 10:42:21 2009
From: mthornton at optrak.co.uk (Mark Thornton)
Date: Thu, 02 Apr 2009 18:42:21 +0100
Subject: Proposal: Sameness operators
In-Reply-To: <27F0EA9D-8936-4330-A5FE-97F522C290F0@zwitserloot.com>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>	<49D3B1E3.8070109@sun.com>	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
	<49D4AF9D.9090407@sun.com> <49D4B40F.2010100@optrak.co.uk>
	<27F0EA9D-8936-4330-A5FE-97F522C290F0@zwitserloot.com>
Message-ID: <49D4F8FD.4080909@optrak.co.uk>

Reinier Zwitserloot wrote:
> The argument that .compareTo should not be used because it isn't 
> entirely congruent with either the meaning of .equals() or the 
> meanings of all the comparison operators (from == to <) on the 
> primitives, just doesn't hold water, for this simple reason:
>
I merely meant that if you want to have a set of comparison operators 
with some of them based on compareTo, then they all must be based on 
compareTo --- you can't use equals (or ==) for the equality comparisons. 
Therefore you have three sets of operations

==, System.identityHashCode(), plus for some types <, <=, >, >=

Object.equals(), Object.hashCode()

Comparable.compareTo()

All these need to remain clearly distinct because their existing 
behaviour is not always compatible.

Mark Thornton






From Jonathan.Gibbons at Sun.COM  Thu Apr  2 11:16:09 2009
From: Jonathan.Gibbons at Sun.COM (Jonathan Gibbons)
Date: Thu, 02 Apr 2009 11:16:09 -0700
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <cf90c1f10904020625s49088dbbv11685b9811b8c14a@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<cf90c1f10904020625s49088dbbv11685b9811b8c14a@mail.gmail.com>
Message-ID: <49D500E9.3050106@sun.com>

For all this sort of analysis, you'd do better to use the combination of 
javac's
annotation processing framework and the javac Tree API, than to use direct
access into private javac API.

Annotation processing isn't just for processing annotations ;-)  You can 
write
a processor that will be called on all types, and you can bridge from the
processing world (javax.lang.model.*) to the java Tree API 
(com.sun.source.*)
using com.sun.source.util.Trees.   This allows you to write utilities to
analyze ASTs without requiring the use of any javac internal API.

-- Jon



Mark Mahieu wrote:
> Wow.
>
> http://www.geekherocomic.com/comics-highres/2009-02-25-coding-overkill.png
>
>
> Here are the important bits from my quick hack.  Took under half an hour to
> get it finding cases where Auto-assignment Parameters would and wouldn't
> work across large source trees.
>
> Of course, javac makes much more than parsing available if you need it...
>
>
>
> import com.sun.tools.javac.file.JavacFileManager;
> import com.sun.tools.javac.parser.JavacParser;
> import com.sun.tools.javac.parser.ParserFactory;
> import com.sun.tools.javac.tree.TreeScanner;
> import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
> import com.sun.tools.javac.tree.JCTree.JCMethodDecl;
> import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
> import com.sun.tools.javac.util.Context;
> import com.sun.tools.javac.util.List;
>
> ...
>
> // create a TreeScanner to do your analysis
> TreeScanner scanner = new TreeScanner() {
>
> @Override
> public void visitMethodDef(JCMethodDecl tree) {
>  // look at a method's parameters
> for (List<JCVariableDecl> l = params; l.nonEmpty(); l = l.tail) {
> JCVariableDecl param = l.head;
>  // examine param or whatever
> }
>  // continue recursively scanning the method body etc
> super.visitMethodDef(tree);
> }
> };
>
> ...
>
> Context context = new Context();
> JavacFileManager.preRegister(context);
> ParserFactory factory = ParserFactory.instance(context);
>
> String sourceCode = readSourceFromFile(...);
>
> JavacParser parser = (JavacParser) factory.newParser(sourceCode, false,
> false, false);
> JCCompilationUnit cu = parser.parseCompilationUnit();
>
> // do your analysis
> scanner.scan(cu);
>
>   



From mthornton at optrak.co.uk  Thu Apr  2 11:31:51 2009
From: mthornton at optrak.co.uk (Mark Thornton)
Date: Thu, 02 Apr 2009 19:31:51 +0100
Subject: Proposal: Sameness operators
In-Reply-To: <27F0EA9D-8936-4330-A5FE-97F522C290F0@zwitserloot.com>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>	<49D3B1E3.8070109@sun.com>	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
	<49D4AF9D.9090407@sun.com> <49D4B40F.2010100@optrak.co.uk>
	<27F0EA9D-8936-4330-A5FE-97F522C290F0@zwitserloot.com>
Message-ID: <49D50497.4020801@optrak.co.uk>

Reinier Zwitserloot wrote:
>
> BI/BD's comparison methods can't just convert the incoming primitive 
> to a BI/BD, because NaN and the infinities don't convert, yet the 
> answer to this expression:
>
> Double.NEGATIVE_INFINITY < BigInteger.ZERO
>
> should clearly be true. The above plan can make that happen by adding 
> more logic to BI/BD's compareTo methods.
The 754R decimal format does include NaN and +-infinite, so perhaps the 
answer here is to modify Java's BigDecimal to match.

Joe could probably tell us more about the possibility of such a change.

Mark Thornton



From Joe.Darcy at Sun.COM  Thu Apr  2 11:33:45 2009
From: Joe.Darcy at Sun.COM (Joe Darcy)
Date: Thu, 02 Apr 2009 11:33:45 -0700
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <49D500E9.3050106@sun.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<cf90c1f10904020625s49088dbbv11685b9811b8c14a@mail.gmail.com>
	<49D500E9.3050106@sun.com>
Message-ID: <49D50509.4020909@sun.com>

On 04/02/09 11:16 AM, Jonathan Gibbons wrote:
> For all this sort of analysis, you'd do better to use the combination of 
> javac's
> annotation processing framework and the javac Tree API, than to use direct
> access into private javac API.
>
> Annotation processing isn't just for processing annotations ;-)  You can 
> write
> a processor that will be called on all types, and you can bridge from the
> processing world (javax.lang.model.*) to the java Tree API 
> (com.sun.source.*)
> using com.sun.source.util.Trees.   This allows you to write utilities to
> analyze ASTs without requiring the use of any javac internal API.
>   

+1

The annotation processing in javac with JSR 269 (and apt before it) is a 
general purpose meta-programming framework.

Combined with the javac tree API, many program analyses can be performed.

-Joe

> -- Jon
>
>
>
> Mark Mahieu wrote:
>   
>> Wow.
>>
>> http://www.geekherocomic.com/comics-highres/2009-02-25-coding-overkill.png
>>
>>
>> Here are the important bits from my quick hack.  Took under half an hour to
>> get it finding cases where Auto-assignment Parameters would and wouldn't
>> work across large source trees.
>>
>> Of course, javac makes much more than parsing available if you need it...
>>
>>
>>
>> import com.sun.tools.javac.file.JavacFileManager;
>> import com.sun.tools.javac.parser.JavacParser;
>> import com.sun.tools.javac.parser.ParserFactory;
>> import com.sun.tools.javac.tree.TreeScanner;
>> import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
>> import com.sun.tools.javac.tree.JCTree.JCMethodDecl;
>> import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
>> import com.sun.tools.javac.util.Context;
>> import com.sun.tools.javac.util.List;
>>
>> ...
>>
>> // create a TreeScanner to do your analysis
>> TreeScanner scanner = new TreeScanner() {
>>
>> @Override
>> public void visitMethodDef(JCMethodDecl tree) {
>>  // look at a method's parameters
>> for (List<JCVariableDecl> l = params; l.nonEmpty(); l = l.tail) {
>> JCVariableDecl param = l.head;
>>  // examine param or whatever
>> }
>>  // continue recursively scanning the method body etc
>> super.visitMethodDef(tree);
>> }
>> };
>>
>> ...
>>
>> Context context = new Context();
>> JavacFileManager.preRegister(context);
>> ParserFactory factory = ParserFactory.instance(context);
>>
>> String sourceCode = readSourceFromFile(...);
>>
>> JavacParser parser = (JavacParser) factory.newParser(sourceCode, false,
>> false, false);
>> JCCompilationUnit cu = parser.parseCompilationUnit();
>>
>> // do your analysis
>> scanner.scan(cu);
>>
>>   
>>     
>
>
>   



From reinier at zwitserloot.com  Thu Apr  2 11:53:18 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Thu, 2 Apr 2009 20:53:18 +0200
Subject: Proposal: Sameness operators
In-Reply-To: <49D4F8FD.4080909@optrak.co.uk>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>	<49D3B1E3.8070109@sun.com>	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
	<49D4AF9D.9090407@sun.com> <49D4B40F.2010100@optrak.co.uk>
	<27F0EA9D-8936-4330-A5FE-97F522C290F0@zwitserloot.com>
	<49D4F8FD.4080909@optrak.co.uk>
Message-ID: <F8EAC161-4969-4980-9B72-89F15C235757@zwitserloot.com>

Why must == also run off of compareTo? (Or, alternatively, why do you - 
need- an equality-checking operation based on compareTo that isn't  
==)? Java cannot enforce contracts in that way; for example, it's  
perfectly legal syntactically, eventhough you're breaking the API  
contract, to always "return 1;" in response to a compareTo. Unless an  
actual compare operation attempts both the stated comparison and the  
mathematically equivalent reverse (a < b and b > a) and throws an  
exception if the results aren't equal, there's no guarantee that  
compareTo makes any sense.

The current situation with boxing primitives is that == and <> and  
extremely inconsistent; new Double(5) vs. new Double(5) isn't ==  
equal, but they are equal as far as compareTo is concerned.

Nevertheless, people -do- apply comparisons in java. Making it easier  
ought to help.  To further complicate things, introducing a new  
Comparable-like interface that doesn't suffer from these problems as  
badly (for example by wanting an enum back instead of a positive/ 
negative/zero value) will not be compatible with the existing  
Comparable, which would be awkard for HashSet.

My point is thus: There is a perfect world, and java doesn't have it.  
And it never will. Either we do this, or we give up and never have any  
sort of improvement to the comparable situation. If that's the choice,  
I want comparator operators, even with the glitches.

  --Reinier Zwitserloot



On Apr 2, 2009, at 19:42, Mark Thornton wrote:

> Reinier Zwitserloot wrote:
>> The argument that .compareTo should not be used because it isn't  
>> entirely congruent with either the meaning of .equals() or the  
>> meanings of all the comparison operators (from == to <) on the  
>> primitives, just doesn't hold water, for this simple reason:
>>
> I merely meant that if you want to have a set of comparison  
> operators with some of them based on compareTo, then they all must  
> be based on compareTo --- you can't use equals (or ==) for the  
> equality comparisons. Therefore you have three sets of operations
>
> ==, System.identityHashCode(), plus for some types <, <=, >, >=
>
> Object.equals(), Object.hashCode()
>
> Comparable.compareTo()
>
> All these need to remain clearly distinct because their existing  
> behaviour is not always compatible.
>
> Mark Thornton
>
>
>
>



From mthornton at optrak.co.uk  Thu Apr  2 12:18:29 2009
From: mthornton at optrak.co.uk (Mark Thornton)
Date: Thu, 02 Apr 2009 20:18:29 +0100
Subject: Proposal: Sameness operators
In-Reply-To: <F8EAC161-4969-4980-9B72-89F15C235757@zwitserloot.com>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>	<49D3B1E3.8070109@sun.com>	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
	<49D4AF9D.9090407@sun.com> <49D4B40F.2010100@optrak.co.uk>
	<27F0EA9D-8936-4330-A5FE-97F522C290F0@zwitserloot.com>
	<49D4F8FD.4080909@optrak.co.uk>
	<F8EAC161-4969-4980-9B72-89F15C235757@zwitserloot.com>
Message-ID: <49D50F85.4040401@optrak.co.uk>

Reinier Zwitserloot wrote:
> My point is thus: There is a perfect world, and java doesn't have it. 
> And it never will. Either we do this, or we give up and never have any 
> sort of improvement to the comparable situation. If that's the choice, 
> I want comparator operators, even with the glitches.
>
A new set of operators like (==), (<), etc, all based on compareTo would 
work, but I don't know how likely such a change is. In their favour, 
these operators would NOT be overloaded so the usual complaints about 
operators wouldn't apply.

Mark



From peter.levart at gmail.com  Thu Apr  2 12:30:10 2009
From: peter.levart at gmail.com (Peter Levart)
Date: Thu, 2 Apr 2009 21:30:10 +0200
Subject: Proposal: Automatic Resource Management
In-Reply-To: <370F8DB1-A374-43B4-9F83-ABCD5A925D93@zwitserloot.com>
References: <aad309390904020459m6d85ea6aqa8ade12dbab67399@mail.gmail.com>
	<370F8DB1-A374-43B4-9F83-ABCD5A925D93@zwitserloot.com>
Message-ID: <aad309390904021230q117ff7f8n31652d2704b169ed@mail.gmail.com>

Hello Coiners!

I played with ARM a little more and also considered Reinier Zwitserloot's
remarks to
my idea of making ARM more SARM (Semi Automatic Resource Management).
I apologise again of accusing Bob Lee's example as flawed. Now that I fully
understand
Joshua Bloch's ARM proposal, I'm convinced that it's exception suppressing
logic
is correct for most usage scenarios.

One weakness that the ARM spec does not address yet is about how
AutomaticResource interface should be handled in obscure situations of
multiple
inheritance.

So I'm still trying to get rid of the need for special interface altogether.

Here's my second take:

        try (InputStream in = new FileInputStream(inputFile); in.close())
        {
            // try block
        }
        catch(IOException e)
        {
            // catch block
        }
        finally
        {
            // finally block
        }

... to be translated into:

        try
        {
            InputStream in = new FileInputStream(inputFile);
            boolean $$suppress = false;

            try
            {
                // try block
            }
            catch (final Throwable $$t)
            {
                $$suppress = true;
                throw $$t;
            }
            finally
            {
                if ($$suppress)
                    try { in.close(); } catch (Throwable $$ignore) {}
                else
                    in.close();
            }
        }
        catch (IOException e)
        {
            // catch block
        }
        finally
        {
            // finally block
        }

... that's not much different from Joshua's original proposal. In fact it
uses the same
exception suppressing logic. There are only 3 differences:

- does not use a special interface
- disposal is explicit (Semi Automatic)
- handles only a single resource

But with both "catch" and "finally" parts as optional, the following:

        try (InputStream in = new FileInputStream(inputFile); in.close())
        {
            // try block
        }

... is translated into:

        {
            InputStream in = new FileInputStream(inputFile);
            boolean $$suppress = false;

            try
            {
                // try block
            }
            catch (final Throwable $$t)
            {
                $$suppress = true;
                throw $$t;
            }
            finally
            {
                if ($$suppress)
                    try { in.close(); } catch (Throwable $$ignore) {}
                else
                    in.close();
            }
        }

... and so, single-resource SARM constructs can then be nested to construct
for example this:

        try (InputStream in = new FileInputStream(inputFile); in.close()) {
            try (OutputStream out = new FileOutputStream(outputFile);
out.close()) {
                // try block
            }
        }
        catch(IOException e)
        {
            // catch block
        }

... one more with locking:

        ReadWriteLock rwl = ...

        try (rwl.writeLock().lock(); rwl.writeLock().unlock()) {
            i++;
        }

That's it. What dou you think?

Regards, Peter


From develop4lasu at gmail.com  Thu Apr  2 12:33:10 2009
From: develop4lasu at gmail.com (=?UTF-8?Q?Marek_Kozie=C5=82?=)
Date: Thu, 2 Apr 2009 21:33:10 +0200
Subject: Proposal: Automatic Resource Management
In-Reply-To: <aad309390904020459m6d85ea6aqa8ade12dbab67399@mail.gmail.com>
References: <aad309390904020459m6d85ea6aqa8ade12dbab67399@mail.gmail.com>
Message-ID: <28bca0ff0904021233u2fae0949tb0a9c4171cd9ab1e@mail.gmail.com>

2009/4/2 Peter Levart <peter.levart at gmail.com>:
> Hello Coiners!
>
> The debate about ARM proposal has calmed down lately and I was thinking
> about it last few days. Initially I submitted a comment that got lost by
> list processor and was about using a "marker" interface as a supertype of
> sigle-method disposable interfaces like this:
>
>
> package java.lang;
>
> public interface AutomaticResource {}
>
>
> ... and for example, retroffiting java.io.Closeable:
>
>
> package java.io;
>
> public interface Closeable extends AutomaticResource {
> ? ?void close() throws IOException;
> }
>
>
> ... this way even the name of the method would not be "coined". There would
> have to be some rules that compiler will enforce to make sure it can
> uniquely identify the method to be called on resource disposal (for example:
> the static type of the resource should not directly or indirectly implement
> or extend two different single-method interfaces marked with
> AutomaticResource marker superinterface).
>
> But then I thought. Why would this language feature even have to be tied to
> a particular interface. The "foreach" loop did take this approach with
> java.lang.Iterable, but this had nothing to do with exceptions and catching
> them and ignoring them silently. A language construct that hides this often
> cited "bad practice" under the carpet is no good!
>
> For example, this snippet of code, written to the proposed ARM spec.,
> submited by Bob Lee in this thread a month ago, asking Neal Gafter to
> demonstrate how the equivalent BGGA version would look like:
>
> ?try (InputStream in = new FileInputStream(src);
> ? ? ?OutputStream out = new FileOutputStream(dest)) {
> ? ?byte[] buf = new byte[8 * 1024];
> ? ?int n;
> ? ?while ((n = in.read(buf)) >= 0)
> ? ? ?out.write(buf, 0, n);
> ?} catch (IOException e) {
> ? ?showDialog("Copy failed.");
> ?}
>
> ... is flawed. This code does not guarantee that in the absence of shown
> exception the file has been copied in it's intirety.
>
> Ignoring exception thrown on an InputStream.close() might be desireable, but
> ignoring exception thrown on OutputStream.close() migh mean that you don't
> mind missing writing some final bytes into the file. Closing OutputStream
> should not be part of automatic resource disposal but part of main code
> block. This brings us to the question how is ARM supposed to be able do
> differentiate InputStream from OutputStream if both implement Closeable?
>
> So I thought how to circumvent these two weeknesses. My take on this is
> something like the following:
>
>
> ? ? ? ?try (InputStream in = new FileInputStream("inputFile");
> ? ? ? ? ? ? OutputStream out = new FileOutputStream("outputFile"))
> ? ? ? ?{
> ? ? ? ? ?// try body
> ? ? ? ?}
> ? ? ? ?catch (IOException e)
> ? ? ? ?{
> ? ? ? ? ?// catch body
> ? ? ? ?}
> ? ? ? ?finally (IOException e1 : in.close();
> ? ? ? ? ? ? ? ? IOException e2 : out.close())
> ? ? ? ?{
> ? ? ? ? ?// finally body
> ? ? ? ?}
>
>
> ... would be translated to ...
>
>
> ? ? ? ?{
> ? ? ? ? ? ?IOException e1 = null;
> ? ? ? ? ? ?IOException e2 = null;
>
> ? ? ? ? ? ?try
> ? ? ? ? ? ?{
> ? ? ? ? ? ? ? ?InputStream in = new FileInputStream("inputFile");
>
> ? ? ? ? ? ? ? ?try
> ? ? ? ? ? ? ? ?{
> ? ? ? ? ? ? ? ? ? ?OutputStream out = new FileOutputStream("outputFile");
>
> ? ? ? ? ? ? ? ? ? ?try
> ? ? ? ? ? ? ? ? ? ?{
> ? ? ? ? ? ? ? ? ? ? ? ?// try body
> ? ? ? ? ? ? ? ? ? ?}
> ? ? ? ? ? ? ? ? ? ?finally
> ? ? ? ? ? ? ? ? ? ?{
> ? ? ? ? ? ? ? ? ? ? ? ?try
> ? ? ? ? ? ? ? ? ? ? ? ?{
> ? ? ? ? ? ? ? ? ? ? ? ? ? ?out.close();
> ? ? ? ? ? ? ? ? ? ? ? ?}
> ? ? ? ? ? ? ? ? ? ? ? ?catch (IOException $$e)
> ? ? ? ? ? ? ? ? ? ? ? ?{
> ? ? ? ? ? ? ? ? ? ? ? ? ? ?e2 = $$e;
> ? ? ? ? ? ? ? ? ? ? ? ?}
> ? ? ? ? ? ? ? ? ? ?}
> ? ? ? ? ? ? ? ?}
> ? ? ? ? ? ? ? ?finally
> ? ? ? ? ? ? ? ?{
> ? ? ? ? ? ? ? ? ? ?try
> ? ? ? ? ? ? ? ? ? ?{
> ? ? ? ? ? ? ? ? ? ? ? ?in.close();
> ? ? ? ? ? ? ? ? ? ?}
> ? ? ? ? ? ? ? ? ? ?catch (IOException $$e)
> ? ? ? ? ? ? ? ? ? ?{
> ? ? ? ? ? ? ? ? ? ? ? ?e1 = $$e;
> ? ? ? ? ? ? ? ? ? ?}
> ? ? ? ? ? ? ? ?}
> ? ? ? ? ? ?}
> ? ? ? ? ? ?catch (IOException e)
> ? ? ? ? ? ?{
> ? ? ? ? ? ? ? ?// catch body
> ? ? ? ? ? ?}
> ? ? ? ? ? ?finally
> ? ? ? ? ? ?{
> ? ? ? ? ? ? ? ?// finally body
> ? ? ? ? ? ?}
> ? ? ? ?}
>
>
>
> ... no special interfaces are used here. The code to dispose of resources is
> clearly visible (it has to be writen, yes, but that also means that it can
> be read, which is a good thing).
>
> The above example is the "full monty" version. The thing to note is that a
> try (...; ...; ...) construct is to be matched by an optional finally (...;
> ...; ...) construct in that both, if the second is specified, must have an
> equal number of semicolons. Each "statement" in the try construct gets it's
> own slot that must be matched by the coresponding slot in the finally (...;
> ...; ...) construct. Any slot in finally construct can be left empty (like
> any of the 3 slots in the for (;;) statement).
>
> The following minimal version is also possible (in this example no catching
> of exceptions on resource cleanup is attempted):
>
> int i, j;
> ReadWriteLock iLock = ...;
> ReadWriteLock jLock = ...;
>
> // ...
>
> try (jLock.readLock().lock(); iLock.writeLock().lock()) {
> ?i += j;
> }
> finally (jLock.readLock().unlock(); iLock.writeLock().unlock())
>
>
> ... gets translated to:
>
>
> {
> ? ?jLock.readLock().lock();
> ? ?try {
> ? ? ?iLock.writeLock().lock();
> ? ? ?try {
> ? ? ? ?i += j;
> ? ? ?}
> ? ? ?finally {
> ? ? ? ?iLock.writeLock().unlock();
> ? ? ?}
> ? ?}
> ? ?finally {
> ? ? ?jLock.readLock().unlock();
> ? ?}
> }
>
>
> All this will have to be formalized. This is just an idea to keep the debate
> going.
>
> Regards, Peter
>
>

If I can I would suggest:
       try (InputStream in = new FileInputStream("inputFile");
            OutputStream out = new FileOutputStream("outputFile"))
       {
         // try body
       }
       catch (IOException e)
       {
         // catch body
       }
       finally (IOException e1 : in.close();
                IOException e2 : out.close())
       {
         // finally body
       }

change to:
catch:
catch(variable = Type);
catch(variable = Type exceptionVariable){};
catch(Type exceptionVariable){};

allow mix try with new :
new try Constructor catch ....;
variable would be null is exception occurs.


IOException exception = null;
InputStream in = new try FileInputStream("inputFile") catch (exception
= IOException);
if (in == null) return ...;
OutputStream out = new try FileOutputStream("outputFile")) catch
(exception = IOException);
if ( (in != null) && (out != null) ) try{
     ...
     }
catch (exception = IOException);
if (in != null)  try {in.close(); } catch (exception = IOException);
if (out != null)  try {out.close(); } catch (exception = IOException);
if (exception != null) throw  exception;
...

But I didn't analyzed all interactions.


for locks I still think that they should be done by:
synchronize.write(lock){}


-- 
Pozdrowionka. / Regards.
Lasu aka Marek Kozie?

http://lasu2string.blogspot.com/


From develop4lasu at gmail.com  Thu Apr  2 12:48:30 2009
From: develop4lasu at gmail.com (=?UTF-8?Q?Marek_Kozie=C5=82?=)
Date: Thu, 2 Apr 2009 21:48:30 +0200
Subject: PROPOSAL: 'final' without explicit type
In-Reply-To: <87zlf0pduc.fsf@mid.deneb.enyo.de>
References: <28bca0ff0903261305x2de00436r5ca8183fe01578d4@mail.gmail.com>
	<A0A1A39D-6569-41C5-AFD4-250EB82BF0C3@zwitserloot.com>
	<87fxgwzfew.fsf@mid.deneb.enyo.de>
	<28bca0ff0903291422s77f11c44j4ddf6ea45ec0b669@mail.gmail.com>
	<87zlf0pduc.fsf@mid.deneb.enyo.de>
Message-ID: <28bca0ff0904021248t336d38d2tb1b4a7d8a6d51137@mail.gmail.com>

2009/4/1 Florian Weimer <fw at deneb.enyo.de>:
> * Marek Kozie?:
>
>> ? ? ? <T extends I1&I2,K extends I1&I2> void noInterection(T t,K k){
>> ? ? ? ? ? ? ? if (boo)t=k; // Type mismatch: cannot convert from K to T
>> ? ? ? ? ? ? ? ...
>> ? ? ? }
>
> The assignment is not type-safe anyway, as the following modification
> shows:
>
>
> ? ? ? ?<T extends I1&I2,K extends I1&I2> T noInterection(T t,K k){
> ? ? ? ? ? ? ? ?if (boo)t=k; // Type mismatch: cannot convert from K to T
> ? ? ? ? ? ? ? ?return t;
> ? ? ? ?}
>
> This would allow to convert values of any type which implements I1 and
> I2 to any other type which implements the two interfaces, which is
> clearly bogus.
>
> Consequently, I think your snippet doesn't show what you claim.
>

I wanted to show when assignment is possible :

Intersection : I1 & I2
Bounds : $ extends I1 & I2

Intersection = Bounds // OK
Intersection = Intersection // OK
Bounds = Intersection // Error
Bounds = Bounds // Error

-- 
Pozdrowionka. / Regards.
Lasu aka Marek Kozie?

http://lasu2string.blogspot.com/


From Joe.Darcy at Sun.COM  Thu Apr  2 12:48:54 2009
From: Joe.Darcy at Sun.COM (Joe Darcy)
Date: Thu, 02 Apr 2009 12:48:54 -0700
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <d8e827e34ea76f830c27ec529a882e57.squirrel@wmail.gradsoft.ua>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<28bca0ff0904020528l51d803f2t5a6dc29a8f6a67dc@mail.gmail.com>
	<b1cac5cf489dbd8c889200db29eb11cd.squirrel@wmail.gradsoft.ua>
	<31AB3E69-CCE7-4134-95C9-4DB5BF6C9281@zwitserloot.com>
	<d8e827e34ea76f830c27ec529a882e57.squirrel@wmail.gradsoft.ua>
Message-ID: <49D516A6.6000404@sun.com>

On 04/02/09 09:09 AM, rssh at gradsoft.com.ua wrote:
>> Polling has many, many problems associated with it:
>>
>>     
>
>  yes.  But we have no other ways to know 'meaning of mass'. I. e. 'design
> by poll' is not good idea, but 'design without any information from real
> word' is not good idea also.
>
> It's well-known problem in sociology, where, unlike computer science, we
>  have no correct instruments at all. Exists some 'non-direct' ways
>  to know how correct is poll: controlled auditories, same poll in different
> cases, but all this is not panacea.
>
>   
>> 1. It does not reliably measure impact. Let's say generics gets a 9.0
>> in the polls, and the foreach loop gets only an 8.0. The right answer
>> is to implement foreach, eventhough it scored lower. It's easier and
>> has less impact. implementing difficulty can be decided by an expert
>> group, but there's also the concept of impact.
>>
>>     
>
>  Yes. I think all understand this.
> // btw, near all proposals in project coin are easy implementable.
>   

I do not share that opinion.

There are no simple language changes in Java.

Given the relative scarcity of prototypes, to say nothing of prototypes 
with a thorough test suite, we can at best make informed estimates of 
the difficulty of various changes, but I'm certain there will be 
surprises down the line, as there were for every JDK 5 language change.

>> A nice case in point: Almost everyone rated operator support for
>> BigDecimal and BigInteger as very low in Stephen Colebourne's polls,
>> but is that reflective? I don't think so. It's just the one with the
>> lowest impact - no body cares about that a lot, and some care about it
>> not at all. It is, however, hard to see how operator support for
>> BigDecimal/BigInteger can break, well, anything. The value of any
>> proposal is its positive impact divided by its negative impact, and
>> dividing by a very small number gives you a very large number.
>>
>>     
>
> I also have question to Stephen polls: i. e. I can't understand why
> multiline strings rated so low.  Anybody, who works with databases
>  know, that analyzing query plan or copy non-trivial query test
>  in java is a big pain, and most of Java project in corporate sector use 
> non-trivial sql queris".
>   Only one answer, which I can suggest - that auditory which attend Java
> conferences does not reflect auditory of Java users: most of Java
> conferences attenders do system programming or research and have nothing
> with most of  database projects which is not so interesting and rare
> have academics interest.
>   To verify this, possible repeat his poll on some programmer event, which
> is not so academics.
>   

On this point, I've long thought the Java platform is like the elephant 
in the parable about the blind men and the elephant:

    http://en.wikipedia.org/wiki/Blind_Men_and_an_Elephant

That is, while each of us may know and understand our own usage of Java 
quite and well and have valid ideas about how Java could be changed to 
improve programming in our own areas of interest (properties! operator 
overloading! design by contract!  your favorite feature!), evolving the 
platform  with an eye toward optimizing it *as a whole* will  mean at 
least some areas don't get what they want.

[snip]

> Note, that I does not propose use polls as one and only one criteria. I
> just tell that see result of such poll will be interest.
>
> // btw - from other side, all this activity is overkill, I can suggest,
> // that  accepted proposals would be exactly same, which was listed in
> // project-coin description (before coin was started)
> //     http://blogs.sun.com/darcy/entry/project_coin
> //   +ARM  +jsr292  and ...  it's already 6, which is more than 5 :)
>   

Your own sentence disproves your point since ARM was not listed among 
the five proposal areas under consideration before Project Coin started.

> I. e. doing project coin with external auditory  was a 'Sun system error',
> I guess; if they want some feedback from community, correct way was at
> first implement own stuff, than ask community for something new ;)
>   

The call of proposal phase of Project Coin is an effort both to solicit 
feedback from the external community and also to invite the external 
community to participate more directly in evolving the language.  That 
opportunity to participate also implies participating in the large 
amount of work required to go from "I have this great idea!" to "I have 
this great idea and here is a carefully considered review of all the 
implications of the idea, along with a prototype."  The blogs I wrote 
last year and the proposal form itself are part of an effort to explain 
and expose what this language work entails so more people can get involved.

Unfortunately, many of the submitted proposals did not do a credible job 
of analyzing the true effect the proposal would have, which has a rather 
strong relation to why many were not chosen for further consideration.  
For example, let's take the "'This' type" proposal:

    http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000107.html

Including a this type/self type notion in a programming language type 
system is a well-studied problem in type systems; as I sent to the list, 
papers continue to be written on this topic in the programming language 
literature.  It known to *not* be a simple change to the type system.    
Let's look at the specification section of the proposal:

> SPECIFICATION:
> (I did not have time to analyze this completely.)
>   

The analysis is the part that matters most!  This proposal appears 
completely oblivious to and ignorant of the large amount of prior work 
on this topic.

It is not as if the notion of adding a self type to Java is a new idea; 
there is already a Sun bug for this from several years ago:

    6479372 Add self types (type of 'this' aka ThisClass) to the language
    http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6479372

So in total, this "proposal" added *nothing* to the understanding of 
what adding a this type to Java would mean and how the change could be done.

Those factors weighed quite strongly in why this particular proposal did 
not more on to "for further consideration."

Language design, especially additions to an existing language, is not an 
endeavor where enthusiasm can overcome lack of diligence and expertise.

-Joe



From markmahieu at googlemail.com  Thu Apr  2 13:53:45 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Thu, 2 Apr 2009 21:53:45 +0100
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <49D500E9.3050106@sun.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<cf90c1f10904020625s49088dbbv11685b9811b8c14a@mail.gmail.com>
	<49D500E9.3050106@sun.com>
Message-ID: <cf90c1f10904021353h7b554e82m6154608809c6568c@mail.gmail.com>

Hi Jon,
Invoking the parser directly seemed like the quickest way of grabbing some
figures at the time, but you (and Michael) are quite right of course.

The main point I was trying to get across was there are easily approachable
ways that people can attempt to do some of the analysis Stephen mentioned,
without ripping components out of Netbeans etc to do it, great though they
may be.

But I shouldn't be spreading my bad habits around with abandon like that,
quick hack or not :)

My apologies.

Mark


2009/4/2 Jonathan Gibbons <Jonathan.Gibbons at sun.com>

> For all this sort of analysis, you'd do better to use the combination of
> javac's
> annotation processing framework and the javac Tree API, than to use direct
> access into private javac API.
>
> Annotation processing isn't just for processing annotations ;-)  You can
> write
> a processor that will be called on all types, and you can bridge from the
> processing world (javax.lang.model.*) to the java Tree API
> (com.sun.source.*)
> using com.sun.source.util.Trees.   This allows you to write utilities to
> analyze ASTs without requiring the use of any javac internal API.
>
> -- Jon
>
>
>
>
> Mark Mahieu wrote:
>
>> Wow.
>>
>> http://www.geekherocomic.com/comics-highres/2009-02-25-coding-overkill.png
>>
>>
>> Here are the important bits from my quick hack.  Took under half an hour
>> to
>> get it finding cases where Auto-assignment Parameters would and wouldn't
>> work across large source trees.
>>
>> Of course, javac makes much more than parsing available if you need it...
>>
>>
>>
>> import com.sun.tools.javac.file.JavacFileManager;
>> import com.sun.tools.javac.parser.JavacParser;
>> import com.sun.tools.javac.parser.ParserFactory;
>> import com.sun.tools.javac.tree.TreeScanner;
>> import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
>> import com.sun.tools.javac.tree.JCTree.JCMethodDecl;
>> import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
>> import com.sun.tools.javac.util.Context;
>> import com.sun.tools.javac.util.List;
>>
>> ...
>>
>> // create a TreeScanner to do your analysis
>> TreeScanner scanner = new TreeScanner() {
>>
>> @Override
>> public void visitMethodDef(JCMethodDecl tree) {
>>  // look at a method's parameters
>> for (List<JCVariableDecl> l = params; l.nonEmpty(); l = l.tail) {
>> JCVariableDecl param = l.head;
>>  // examine param or whatever
>> }
>>  // continue recursively scanning the method body etc
>> super.visitMethodDef(tree);
>> }
>> };
>>
>> ...
>>
>> Context context = new Context();
>> JavacFileManager.preRegister(context);
>> ParserFactory factory = ParserFactory.instance(context);
>>
>> String sourceCode = readSourceFromFile(...);
>>
>> JavacParser parser = (JavacParser) factory.newParser(sourceCode, false,
>> false, false);
>> JCCompilationUnit cu = parser.parseCompilationUnit();
>>
>> // do your analysis
>> scanner.scan(cu);
>>
>>
>>
>
>


From develop4lasu at gmail.com  Thu Apr  2 13:59:02 2009
From: develop4lasu at gmail.com (=?UTF-8?Q?Marek_Kozie=C5=82?=)
Date: Thu, 2 Apr 2009 22:59:02 +0200
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <49D516A6.6000404@sun.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<28bca0ff0904020528l51d803f2t5a6dc29a8f6a67dc@mail.gmail.com>
	<b1cac5cf489dbd8c889200db29eb11cd.squirrel@wmail.gradsoft.ua>
	<31AB3E69-CCE7-4134-95C9-4DB5BF6C9281@zwitserloot.com>
	<d8e827e34ea76f830c27ec529a882e57.squirrel@wmail.gradsoft.ua>
	<49D516A6.6000404@sun.com>
Message-ID: <28bca0ff0904021359v4ea9aa05i1ed7782f60c7e84e@mail.gmail.com>

2009/4/2 Joe Darcy <Joe.Darcy at sun.com>:
> On 04/02/09 09:09 AM, rssh at gradsoft.com.ua wrote:
>>> Polling has many, many problems associated with it:
>>>
>>>
>>
>> ?yes. ?But we have no other ways to know 'meaning of mass'. I. e. 'design
>> by poll' is not good idea, but 'design without any information from real
>> word' is not good idea also.
>>
>> It's well-known problem in sociology, where, unlike computer science, we
>> ?have no correct instruments at all. Exists some 'non-direct' ways
>> ?to know how correct is poll: controlled auditories, same poll in different
>> cases, but all this is not panacea.
>>
>>
>>> 1. It does not reliably measure impact. Let's say generics gets a 9.0
>>> in the polls, and the foreach loop gets only an 8.0. The right answer
>>> is to implement foreach, eventhough it scored lower. It's easier and
>>> has less impact. implementing difficulty can be decided by an expert
>>> group, but there's also the concept of impact.
>>>
>>>
>>
>> ?Yes. I think all understand this.
>> // btw, near all proposals in project coin are easy implementable.
>>
>
> I do not share that opinion.
>
> There are no simple language changes in Java.
>
> Given the relative scarcity of prototypes, to say nothing of prototypes
> with a thorough test suite, we can at best make informed estimates of
> the difficulty of various changes, but I'm certain there will be
> surprises down the line, as there were for every JDK 5 language change.
>
>>> A nice case in point: Almost everyone rated operator support for
>>> BigDecimal and BigInteger as very low in Stephen Colebourne's polls,
>>> but is that reflective? I don't think so. It's just the one with the
>>> lowest impact - no body cares about that a lot, and some care about it
>>> not at all. It is, however, hard to see how operator support for
>>> BigDecimal/BigInteger can break, well, anything. The value of any
>>> proposal is its positive impact divided by its negative impact, and
>>> dividing by a very small number gives you a very large number.
>>>
>>>
>>
>> I also have question to Stephen polls: i. e. I can't understand why
>> multiline strings rated so low. ?Anybody, who works with databases
>> ?know, that analyzing query plan or copy non-trivial query test
>> ?in java is a big pain, and most of Java project in corporate sector use
>> non-trivial sql queris".
>> ? Only one answer, which I can suggest - that auditory which attend Java
>> conferences does not reflect auditory of Java users: most of Java
>> conferences attenders do system programming or research and have nothing
>> with most of ?database projects which is not so interesting and rare
>> have academics interest.
>> ? To verify this, possible repeat his poll on some programmer event, which
>> is not so academics.
>>
>
> On this point, I've long thought the Java platform is like the elephant
> in the parable about the blind men and the elephant:
>
> ? ?http://en.wikipedia.org/wiki/Blind_Men_and_an_Elephant
>
> That is, while each of us may know and understand our own usage of Java
> quite and well and have valid ideas about how Java could be changed to
> improve programming in our own areas of interest (properties! operator
> overloading! design by contract! ?your favorite feature!), evolving the
> platform ?with an eye toward optimizing it *as a whole* will ?mean at
> least some areas don't get what they want.
>
> [snip]
>
>> Note, that I does not propose use polls as one and only one criteria. I
>> just tell that see result of such poll will be interest.
>>
>> // btw - from other side, all this activity is overkill, I can suggest,
>> // that ?accepted proposals would be exactly same, which was listed in
>> // project-coin description (before coin was started)
>> // ? ? http://blogs.sun.com/darcy/entry/project_coin
>> // ? +ARM ?+jsr292 ?and ... ?it's already 6, which is more than 5 :)
>>
>
> Your own sentence disproves your point since ARM was not listed among
> the five proposal areas under consideration before Project Coin started.
>
>> I. e. doing project coin with external auditory ?was a 'Sun system error',
>> I guess; if they want some feedback from community, correct way was at
>> first implement own stuff, than ask community for something new ;)
>>
>
> The call of proposal phase of Project Coin is an effort both to solicit
> feedback from the external community and also to invite the external
> community to participate more directly in evolving the language. ?That
> opportunity to participate also implies participating in the large
> amount of work required to go from "I have this great idea!" to "I have
> this great idea and here is a carefully considered review of all the
> implications of the idea, along with a prototype." ?The blogs I wrote
> last year and the proposal form itself are part of an effort to explain
> and expose what this language work entails so more people can get involved.
>
> Unfortunately, many of the submitted proposals did not do a credible job
> of analyzing the true effect the proposal would have, which has a rather
> strong relation to why many were not chosen for further consideration.
> For example, let's take the "'This' type" proposal:
>
> ? ?http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000107.html
>
> Including a this type/self type notion in a programming language type
> system is a well-studied problem in type systems; as I sent to the list,
> papers continue to be written on this topic in the programming language
> literature. ?It known to *not* be a simple change to the type system.
> Let's look at the specification section of the proposal:
>
>> SPECIFICATION:
>> (I did not have time to analyze this completely.)
>>
>
> The analysis is the part that matters most! ?This proposal appears
> completely oblivious to and ignorant of the large amount of prior work
> on this topic.
>
> It is not as if the notion of adding a self type to Java is a new idea;
> there is already a Sun bug for this from several years ago:
>
> ? ?6479372 Add self types (type of 'this' aka ThisClass) to the language
> ? ?http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6479372
>
> So in total, this "proposal" added *nothing* to the understanding of
> what adding a this type to Java would mean and how the change could be done.
>
> Those factors weighed quite strongly in why this particular proposal did
> not more on to "for further consideration."
>
> Language design, especially additions to an existing language, is not an
> endeavor where enthusiasm can overcome lack of diligence and expertise.
>
> -Joe
>
>
>

YES I do make mistakes.
You already said that.

  While I'm against splitting Java into more languages, I'll be happy
even if one proposal will make Java better and more frendly.
  So if you think that i didn't helped at all then remove me from the group.

-- 
Pozdrowionka. / Regards.
Lasu aka Marek Kozie?

http://lasu2string.blogspot.com/


From Jonathan.Gibbons at Sun.COM  Thu Apr  2 14:02:54 2009
From: Jonathan.Gibbons at Sun.COM (Jonathan Gibbons)
Date: Thu, 02 Apr 2009 14:02:54 -0700
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <cf90c1f10904021353h7b554e82m6154608809c6568c@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<cf90c1f10904020625s49088dbbv11685b9811b8c14a@mail.gmail.com>
	<49D500E9.3050106@sun.com>
	<cf90c1f10904021353h7b554e82m6154608809c6568c@mail.gmail.com>
Message-ID: <49D527FE.3050105@sun.com>

Mark,

Quick hacks are good.  My point was just that once you know the coding 
pattern, it can be even easier/quicker to hack up an annotation 
processor to do what you want than to learn the innards of the 
compiler.  The internal API has never been intended for public 
consumption, and there are often undocumented quirks or constraints 
about individual specific methods, meaning it is very much a case of 
"proceed at your own risk".  The good news is that is now a goal to 
support utilities such as you all have been describing, and that JSR 
199, JSR 269 and the Tree API, are all part of the formal support for 
such work.

-- Jon




Mark Mahieu wrote:
> Hi Jon,
>
> Invoking the parser directly seemed like the quickest way of grabbing 
> some figures at the time, but you (and Michael) are quite right of course.
>
> The main point I was trying to get across was there are easily 
> approachable ways that people can attempt to do some of the analysis 
> Stephen mentioned, without ripping components out of Netbeans etc to 
> do it, great though they may be.
>
> But I shouldn't be spreading my bad habits around with abandon like 
> that, quick hack or not :)
>
> My apologies.
>
> Mark
>
>
> 2009/4/2 Jonathan Gibbons <Jonathan.Gibbons at sun.com 
> <mailto:Jonathan.Gibbons at sun.com>>
>
>     For all this sort of analysis, you'd do better to use the
>     combination of javac's
>     annotation processing framework and the javac Tree API, than to
>     use direct
>     access into private javac API.
>
>     Annotation processing isn't just for processing annotations ;-)
>      You can write
>     a processor that will be called on all types, and you can bridge
>     from the
>     processing world (javax.lang.model.*) to the java Tree API
>     (com.sun.source.*)
>     using com.sun.source.util.Trees.   This allows you to write
>     utilities to
>     analyze ASTs without requiring the use of any javac internal API.
>
>     -- Jon
>
>
>
>
>     Mark Mahieu wrote:
>
>         Wow.
>
>         http://www.geekherocomic.com/comics-highres/2009-02-25-coding-overkill.png
>
>
>         Here are the important bits from my quick hack.  Took under
>         half an hour to
>         get it finding cases where Auto-assignment Parameters would
>         and wouldn't
>         work across large source trees.
>
>         Of course, javac makes much more than parsing available if you
>         need it...
>
>
>
>         import com.sun.tools.javac.file.JavacFileManager;
>         import com.sun.tools.javac.parser.JavacParser;
>         import com.sun.tools.javac.parser.ParserFactory;
>         import com.sun.tools.javac.tree.TreeScanner;
>         import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
>         import com.sun.tools.javac.tree.JCTree.JCMethodDecl;
>         import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
>         import com.sun.tools.javac.util.Context;
>         import com.sun.tools.javac.util.List;
>
>         ...
>
>         // create a TreeScanner to do your analysis
>         TreeScanner scanner = new TreeScanner() {
>
>         @Override
>         public void visitMethodDef(JCMethodDecl tree) {
>          // look at a method's parameters
>         for (List<JCVariableDecl> l = params; l.nonEmpty(); l = l.tail) {
>         JCVariableDecl param = l.head;
>          // examine param or whatever
>         }
>          // continue recursively scanning the method body etc
>         super.visitMethodDef(tree);
>         }
>         };
>
>         ...
>
>         Context context = new Context();
>         JavacFileManager.preRegister(context);
>         ParserFactory factory = ParserFactory.instance(context);
>
>         String sourceCode = readSourceFromFile(...);
>
>         JavacParser parser = (JavacParser)
>         factory.newParser(sourceCode, false,
>         false, false);
>         JCCompilationUnit cu = parser.parseCompilationUnit();
>
>         // do your analysis
>         scanner.scan(cu);
>
>          
>
>
>



From Joe.Darcy at Sun.COM  Thu Apr  2 14:28:28 2009
From: Joe.Darcy at Sun.COM (Joe Darcy)
Date: Thu, 02 Apr 2009 14:28:28 -0700
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <28bca0ff0904021359v4ea9aa05i1ed7782f60c7e84e@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<28bca0ff0904020528l51d803f2t5a6dc29a8f6a67dc@mail.gmail.com>
	<b1cac5cf489dbd8c889200db29eb11cd.squirrel@wmail.gradsoft.ua>
	<31AB3E69-CCE7-4134-95C9-4DB5BF6C9281@zwitserloot.com>
	<d8e827e34ea76f830c27ec529a882e57.squirrel@wmail.gradsoft.ua>
	<49D516A6.6000404@sun.com>
	<28bca0ff0904021359v4ea9aa05i1ed7782f60c7e84e@mail.gmail.com>
Message-ID: <49D52DFC.9020306@sun.com>

On 04/02/09 01:59 PM, Marek Kozie? wrote:
> 2009/4/2 Joe Darcy <Joe.Darcy at sun.com>:
>   
>> On 04/02/09 09:09 AM, rssh at gradsoft.com.ua wrote:
>>     
>>>> Polling has many, many problems associated with it:
>>>>
>>>>
>>>>         
>
> YES I do make mistakes.
> You already said that.
>   

The problem is not that you made mistake; the problem is that despite 
being informed how and why your your proposals were inadequate, you 
proceed to submit more than half a dozen other proposals of the same 
character.

>   While I'm against splitting Java into more languages, I'll be happy
> even if one proposal will make Java better and more frendly.
>   

We do not have a deficiency of ideas for proposals; just in Sun's bug 
database there are dozens of valid ways to improve the language.  The 
analysis of the proposals is the scarce and valuable factor.

>   So if you think that i didn't helped at all then remove me from the group
>   

As you wish.

-Joe



From markmahieu at googlemail.com  Thu Apr  2 14:53:23 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Thu, 2 Apr 2009 22:53:23 +0100
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <49D516A6.6000404@sun.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<28bca0ff0904020528l51d803f2t5a6dc29a8f6a67dc@mail.gmail.com>
	<b1cac5cf489dbd8c889200db29eb11cd.squirrel@wmail.gradsoft.ua>
	<31AB3E69-CCE7-4134-95C9-4DB5BF6C9281@zwitserloot.com>
	<d8e827e34ea76f830c27ec529a882e57.squirrel@wmail.gradsoft.ua>
	<49D516A6.6000404@sun.com>
Message-ID: <cf90c1f10904021453t37753788w84de69edaefd6e56@mail.gmail.com>

2009/4/2 Joe Darcy <Joe.Darcy at sun.com>
>
> Given the relative scarcity of prototypes, to say nothing of prototypes
> with a thorough test suite, we can at best make informed estimates of
> the difficulty of various changes, but I'm certain there will be
> surprises down the line, as there were for every JDK 5 language change.


I'd certainly like to see more prototypes, personally; I find them extremely
useful for getting to the details of a proposal.

However, is there any value in people building test suites even if they
can't put together an actual prototype to test them with?  I think there may
be.

Mark


From Ulf.Zibis at gmx.de  Thu Apr  2 15:02:26 2009
From: Ulf.Zibis at gmx.de (Ulf Zibis)
Date: Fri, 03 Apr 2009 00:02:26 +0200
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
Message-ID: <49D535F2.6060009@gmx.de>

Am 02.04.2009 13:39, Stephen Colebourne schrieb:
> All,
> One possible way I'd like to suggest that the coin evaluation could be
> helped would be to write a script to find out how frequently the
> specific issue comes up in real code.
>
> It should be possible to devise, write and run a script to find the
> number of LOCs affected by many of the proposals. For example:
>
> - strings in switch (find if else on constant strings)
>   

More general:
- objects and simple expressions in switch (find repetitive+nested usage 
of if else constructs)

-Ulf

> - multi-catch (find duplicate catch blocks)
> - elvis operator (find ternary and if else defaulting)
> - for each where the iterator remove can be accessed (% of loops that
> access iterator)
> - for each where index is needed (% of loops that use int looping)
> - method and field literals
> - byte and short literals
> and probably many others (I've just listed some proposals I remember)
>
> Ideally, any script would be ASM/BCEL based, but grep style might work too.
>
> I mention all this because I don't have the spare time to write such a
> script, but if you do, then I'm sure we'd all like to run it and
> discuss the results ;-)
>
> Stephen
>
>
>   



From Joe.Darcy at Sun.COM  Thu Apr  2 15:19:40 2009
From: Joe.Darcy at Sun.COM (Joe Darcy)
Date: Thu, 02 Apr 2009 15:19:40 -0700
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <cf90c1f10904021453t37753788w84de69edaefd6e56@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<28bca0ff0904020528l51d803f2t5a6dc29a8f6a67dc@mail.gmail.com>
	<b1cac5cf489dbd8c889200db29eb11cd.squirrel@wmail.gradsoft.ua>
	<31AB3E69-CCE7-4134-95C9-4DB5BF6C9281@zwitserloot.com>
	<d8e827e34ea76f830c27ec529a882e57.squirrel@wmail.gradsoft.ua>
	<49D516A6.6000404@sun.com>
	<cf90c1f10904021453t37753788w84de69edaefd6e56@mail.gmail.com>
Message-ID: <49D539FC.4050005@sun.com>

Mark Mahieu wrote:
> 2009/4/2 Joe Darcy <Joe.Darcy at sun.com <mailto:Joe.Darcy at sun.com>>
> 
>     Given the relative scarcity of prototypes, to say nothing of prototypes
>     with a thorough test suite, we can at best make informed estimates of
>     the difficulty of various changes, but I'm certain there will be
>     surprises down the line, as there were for every JDK 5 language change.
> 
> 
> I'd certainly like to see more prototypes, personally; I find them 
> extremely useful for getting to the details of a proposal.

Yes; they can help in writing the specification too :-)

> However, is there any value in people building test suites even if they 
> can't put together an actual prototype to test them with?  I think there 
> may be.

I was more so thinking of regression style testing in conjunction with 
developing a prototype, but having a limited number of independent tests 
might help too.

-Joe


From forax at univ-mlv.fr  Thu Apr  2 15:25:42 2009
From: forax at univ-mlv.fr (=?ISO-8859-1?Q?R=E9mi_Forax?=)
Date: Fri, 03 Apr 2009 00:25:42 +0200
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <49D535F2.6060009@gmx.de>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<49D535F2.6060009@gmx.de>
Message-ID: <49D53B66.2000509@univ-mlv.fr>

Ulf Zibis a ?crit :
> Am 02.04.2009 13:39, Stephen Colebourne schrieb:
>   
>> All,
>> One possible way I'd like to suggest that the coin evaluation could be
>> helped would be to write a script to find out how frequently the
>> specific issue comes up in real code.
>>
>> It should be possible to devise, write and run a script to find the
>> number of LOCs affected by many of the proposals. For example:
>>
>> - strings in switch (find if else on constant strings)
>>   
>>     
>
> More general:
> - objects and simple expressions in switch (find repetitive+nested usage 
> of if else constructs)
>
> -Ulf
>   
Stephen, Ulf,
Strings can be stored, by example, in a HashMap,
so finding if  a part of a program can be retrofit  or not is far from 
simple.

R?mi



From brucechapman at paradise.net.nz  Thu Apr  2 15:35:52 2009
From: brucechapman at paradise.net.nz (brucechapman at paradise.net.nz)
Date: Fri, 03 Apr 2009 11:35:52 +1300 (NZDT)
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
Message-ID: <1238711752.49d53dc8e0a4c@www.paradise.net.nz>

Good idea,

Should they each be evaluated against the same corpus and what would be a
suitable corpus?

http://en.wikipedia.org/wiki/Corpus_linguistics

Bruce

Quoting Stephen Colebourne <scolebourne at joda.org>:

> All,
> One possible way I'd like to suggest that the coin evaluation could be
> helped would be to write a script to find out how frequently the
> specific issue comes up in real code.
> 
> It should be possible to devise, write and run a script to find the
> number of LOCs affected by many of the proposals. For example:
> 
> - strings in switch (find if else on constant strings)
> - multi-catch (find duplicate catch blocks)
> - elvis operator (find ternary and if else defaulting)
> - for each where the iterator remove can be accessed (% of loops that
> access iterator)
> - for each where index is needed (% of loops that use int looping)
> - method and field literals
> - byte and short literals
> and probably many others (I've just listed some proposals I remember)
> 
> Ideally, any script would be ASM/BCEL based, but grep style might work
> too.
> 
> I mention all this because I don't have the spare time to write such a
> script, but if you do, then I'm sure we'd all like to run it and
> discuss the results ;-)
> 
> Stephen
>  



From Joe.Darcy at Sun.COM  Thu Apr  2 16:02:56 2009
From: Joe.Darcy at Sun.COM (Joe Darcy)
Date: Thu, 02 Apr 2009 16:02:56 -0700
Subject: Proposal: Sameness operators
In-Reply-To: <275433EA-A420-42C8-891D-3B0C2629222A@zwitserloot.com>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>
	<49D3B1E3.8070109@sun.com>
	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
	<4b4f45e00904020524p27741baeo40483e83d71dc768@mail.gmail.com>
	<275433EA-A420-42C8-891D-3B0C2629222A@zwitserloot.com>
Message-ID: <49D54420.5090906@sun.com>

Reinier Zwitserloot wrote:

[snip]

> 
> public static void is(Object x, Object y) {
>      if ( x == null ) return y == null;
>      return x.equals(y);
> }
> 
> public static void is(Object x, int y) {
>     // Yes, you'd need a few gazillion is methods to cover all the  
> primitives on either side, but 1 static import will grab all of them
> }
> 
> ... loads more is methods
> 
> 
> Then same with lt, gt, le, ge.
> 
> Then you could write:
> 
> if ( is(a, b) ) {
>    //doStuff
> }
> 
> Which is a small improvement.
> 
> Add an ability to specify 'as infix' in static imports, and you have  
> pretty much what we all want without backwards compatibility issues:
> 
> import static java.lang.Equality.is infix;
> 
> if ( a is b ) {
>    //do something
> }
> 
> I'd consider that a large improvement.

Yes, in JDK 7 I'd like to see

     6797535 Add shared two argument static equals method to the platform
     http://bugs.sun.com/view_bug.do?bug_id=6797535

addressed in the platform.  I was thinking putting it in a place like a 
new utility class java.util.Object.

-Joe


From Joe.Darcy at Sun.COM  Thu Apr  2 16:13:36 2009
From: Joe.Darcy at Sun.COM (Joe Darcy)
Date: Thu, 02 Apr 2009 16:13:36 -0700
Subject: Proposal: Sameness operators
In-Reply-To: <49D50497.4020801@optrak.co.uk>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>
	<49D3B1E3.8070109@sun.com>
	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
	<49D4AF9D.9090407@sun.com> <49D4B40F.2010100@optrak.co.uk>
	<27F0EA9D-8936-4330-A5FE-97F522C290F0@zwitserloot.com>
	<49D50497.4020801@optrak.co.uk>
Message-ID: <49D546A0.4010406@sun.com>

Mark Thornton wrote:
> Reinier Zwitserloot wrote:
>> BI/BD's comparison methods can't just convert the incoming primitive 
>> to a BI/BD, because NaN and the infinities don't convert, yet the 
>> answer to this expression:
>>
>> Double.NEGATIVE_INFINITY < BigInteger.ZERO
>>
>> should clearly be true. The above plan can make that happen by adding 
>> more logic to BI/BD's compareTo methods.
> The 754R decimal format does include NaN and +-infinite, so perhaps the 
> answer here is to modify Java's BigDecimal to match.

Yes, I actually worked on incorporating the decimal changes into the 
754R draft while I was editor :-)  The "preferred exponent" nomenclature 
in the new 754 standard came from the JSR 13 BigDecimal specification 
work in JDK 5.

> Joe could probably tell us more about the possibility of such a change.

We don't plan to add the non-finite values and negative zero to the set 
of values recognized by BigDecimal.  If someone wanted to do this, I'd 
recommend creating a wrapper around BigDecimal that supported the new 
values and otherwise delegated to an internal BigDecimal.

-Joe


From rssh at gradsoft.com.ua  Thu Apr  2 16:30:27 2009
From: rssh at gradsoft.com.ua (rssh at gradsoft.com.ua)
Date: Fri, 3 Apr 2009 02:30:27 +0300 (EEST)
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <49D516A6.6000404@sun.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<28bca0ff0904020528l51d803f2t5a6dc29a8f6a67dc@mail.gmail.com>
	<b1cac5cf489dbd8c889200db29eb11cd.squirrel@wmail.gradsoft.ua>
	<31AB3E69-CCE7-4134-95C9-4DB5BF6C9281@zwitserloot.com>
	<d8e827e34ea76f830c27ec529a882e57.squirrel@wmail.gradsoft.ua>
	<49D516A6.6000404@sun.com>
Message-ID: <f1eba259d51e01b1f96f4fd29202fb94.squirrel@wmail.gradsoft.ua>


>>
>>  Yes. I think all understand this.
>> // btw, near all proposals in project coin are easy implementable.
>>
>
> I do not share that opinion.
>
> There are no simple language changes in Java.
>

Of course, word 'simple' is relative ;)
 // And to be correct, I mean proposals upward some quality point.

 .......
>
> On this point, I've long thought the Java platform is like the elephant
> in the parable about the blind men and the elephant:
>
>     http://en.wikipedia.org/wiki/Blind_Men_and_an_Elephant
>
> That is, while each of us may know and understand our own usage of Java
> quite and well and have valid ideas about how Java could be changed to
> improve programming in our own areas of interest (properties! operator
> overloading! design by contract!  your favorite feature!), evolving the
> platform  with an eye toward optimizing it *as a whole* will  mean at
> least some areas don't get what they want.
>

 Good point. In parable elephants exists and each blinder can touch his
part. In our case, for some blinders, elephant must not exists ;)))

Even if it can be 'build' in such direction, but we choose not to grow
elephant in all directions, because we can't grow quickly.

And also exists many group of blinders, near different points of elephants,
some groups are big but silent, some are small but loud. Elephant designers
are also blinders and guided listening ;)


> [snip]
>
>> Note, that I does not propose use polls as one and only one criteria. I
>> just tell that see result of such poll will be interest.
>>
>> // btw - from other side, all this activity is overkill, I can suggest,
>> // that  accepted proposals would be exactly same, which was listed in
>> // project-coin description (before coin was started)
>> //     http://blogs.sun.com/darcy/entry/project_coin
>> //   +ARM  +jsr292  and ...  it's already 6, which is more than 5 :)
>>
>
> Your own sentence disproves your point since ARM was not listed among
> the five proposal areas under consideration before Project Coin started.
>

I mean not '<cite>would be exactly same, which was listed in project-coin
description (before coin was started)[url]</cite>', but '<cite>would be
exactly same, which was listed in project-coin description (before coin
was started)[url] +ARM  +jsr292</cite>',
 sorry for ambiguity.

 ARM floating around (and widly discussed) from late 2007 or early 2008.
And all we know, that if BGGA will not available, than at least ARM must
be included.  I. e. I can't say that ARM is 'external' and new or not to
be generally known be included in Java 7 before project coin start.

I have no pretension about judgement process, It's only about information
flow: i. e. Sun have all proposals before and <IMHO> call for new
proposals with process of selecting 5 from set of newly received and 5
apriory well-known items, for which we know, that they are necessory, it's
near the same, that throw away all non-apriory proposals.
</IMHO>

I. e. I guess, that when people asked to submit new proposals, they expect
that exists demand for new proposals, not demand for choosing from five
well-known items. When appointment of all new proposals to be thrown away,
with role be backgroung for well-known items, people, which invested some
time in such activity, usually frustrated. It's why I think, that call for
new proposals, whithout real possibility to implement something new (not
well-known before) was an error. If we have slot, for example, in summary
for 10 proposals to implement (5 well know and 5 new) - then all ok, it's
fair game.


>> I. e. doing project coin with external auditory  was a 'Sun system
>> error',
>> I guess; if they want some feedback from community, correct way was at
>> first implement own stuff, than ask community for something new ;)
>>
>
> The call of proposal phase of Project Coin is an effort both to solicit
> feedback from the external community and also to invite the external
> community to participate more directly in evolving the language.  That
> opportunity to participate also implies participating in the large
> amount of work required to go from "I have this great idea!" to "I have
> this great idea and here is a carefully considered review of all the
> implications of the idea, along with a prototype."  The blogs I wrote
> last year and the proposal form itself are part of an effort to explain
> and expose what this language work entails so more people can get
> involved.
>


It would be great, to participate in language evolution in future.
For now I does not see general aviable process for future participation:
call closed, all new proposal throwed away.
Finish. Fire bug reports is useless - they will live in bugzilla for years.

One possible solution: is make 'coin project' regular, for example once a
year. (May be with
entry barrier as 'required implementation in some form')
Another - propose some process (may be long) for author, how to push his
proposal (whith implementation)
into language after JDK7 (or receive official position, that this change
is rejected)


> Unfortunately, many of the submitted proposals did not do a credible job
> of analyzing the true effect the proposal would have, which has a rather
> strong relation to why many were not chosen for further consideration.
> For example, let's take the "'This' type" proposal:
>
 ...


Problem with inaccurate proposals - it's well known problem, the same with
publications, wildly used technique is peer review. (Honesly, overall
quality of proposals was better that I was expected).

Good entry barrier can be requirement to proposal to be implemented in
some form.

P.S. Project coin involved me to think about Java more close than before.
So, despite my criticism, you achieve goal to raise interest to
participate in process of Java language evolution ;)







From tim.keith at gmail.com  Thu Apr  2 16:49:13 2009
From: tim.keith at gmail.com (Tim Keith)
Date: Thu, 2 Apr 2009 16:49:13 -0700
Subject: Proposal: Sameness operators
In-Reply-To: <49D54420.5090906@sun.com>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>
	<49D3B1E3.8070109@sun.com>
	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
	<4b4f45e00904020524p27741baeo40483e83d71dc768@mail.gmail.com>
	<275433EA-A420-42C8-891D-3B0C2629222A@zwitserloot.com>
	<49D54420.5090906@sun.com>
Message-ID: <e32549de0904021649t3eb92475me79a85206143e7e@mail.gmail.com>

I would like to suggest calling the class java.lang.Objects, similar
to java.util.Collections and java.util.Arrays.

And it would be handy to also have in there a null-safe static method
to help in implementing hashCode:
    public static int hashCode(Object o) {
        return o == null ? 0 : o.hashCode();
    }

-- Tim

On Thu, Apr 2, 2009 at 4:02 PM, Joe Darcy <Joe.Darcy at sun.com> wrote:
> Reinier Zwitserloot wrote:
>
> [snip]
>
>>
>> public static void is(Object x, Object y) {
>>      if ( x == null ) return y == null;
>>      return x.equals(y);
>> }
>>
>> public static void is(Object x, int y) {
>>     // Yes, you'd need a few gazillion is methods to cover all the
>> primitives on either side, but 1 static import will grab all of them
>> }
>>
>> ... loads more is methods
>>
>>
>> Then same with lt, gt, le, ge.
>>
>> Then you could write:
>>
>> if ( is(a, b) ) {
>>    //doStuff
>> }
>>
>> Which is a small improvement.
>>
>> Add an ability to specify 'as infix' in static imports, and you have
>> pretty much what we all want without backwards compatibility issues:
>>
>> import static java.lang.Equality.is infix;
>>
>> if ( a is b ) {
>>    //do something
>> }
>>
>> I'd consider that a large improvement.
>
> Yes, in JDK 7 I'd like to see
>
>     6797535 Add shared two argument static equals method to the platform
>     http://bugs.sun.com/view_bug.do?bug_id=6797535
>
> addressed in the platform.  I was thinking putting it in a place like a
> new utility class java.util.Object.
>
> -Joe
>
>


From scolebourne at joda.org  Thu Apr  2 17:28:02 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Fri, 03 Apr 2009 01:28:02 +0100
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <1238711752.49d53dc8e0a4c@www.paradise.net.nz>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<1238711752.49d53dc8e0a4c@www.paradise.net.nz>
Message-ID: <49D55812.9010809@joda.org>

I think that as a first step, any info on the most likely Coins would be 
beneficial. I'd suggest publishing the script alongside the results.

Stephen


brucechapman at paradise.net.nz wrote:
> Good idea,
> 
> Should they each be evaluated against the same corpus and what would be a
> suitable corpus?
> 
> http://en.wikipedia.org/wiki/Corpus_linguistics
> 
> Bruce
> 
> Quoting Stephen Colebourne <scolebourne at joda.org>:
> 
>> All,
>> One possible way I'd like to suggest that the coin evaluation could be
>> helped would be to write a script to find out how frequently the
>> specific issue comes up in real code.
>>
>> It should be possible to devise, write and run a script to find the
>> number of LOCs affected by many of the proposals. For example:
>>
>> - strings in switch (find if else on constant strings)
>> - multi-catch (find duplicate catch blocks)
>> - elvis operator (find ternary and if else defaulting)
>> - for each where the iterator remove can be accessed (% of loops that
>> access iterator)
>> - for each where index is needed (% of loops that use int looping)
>> - method and field literals
>> - byte and short literals
>> and probably many others (I've just listed some proposals I remember)
>>
>> Ideally, any script would be ASM/BCEL based, but grep style might work
>> too.
>>
>> I mention all this because I don't have the spare time to write such a
>> script, but if you do, then I'm sure we'd all like to run it and
>> discuss the results ;-)
>>
>> Stephen
>>  
> 
> 


From Joe.Darcy at Sun.COM  Thu Apr  2 19:08:43 2009
From: Joe.Darcy at Sun.COM (Joe Darcy)
Date: Thu, 02 Apr 2009 19:08:43 -0700
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <1238711752.49d53dc8e0a4c@www.paradise.net.nz>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<1238711752.49d53dc8e0a4c@www.paradise.net.nz>
Message-ID: <49D56FAB.8090405@sun.com>

brucechapman at paradise.net.nz wrote:
> Good idea,
> 
> Should they each be evaluated against the same corpus and what would 
> be a suitable corpus?
> 
> http://en.wikipedia.org/wiki/Corpus_linguistics

On that front, Alex sent me the following:

> Analysis of a micro-corpus of your own or your company's code is
> unscientific.
> 
> Ewan Tempero and his colleagues at the University of Auckland have 
> done excellent, peer-reviewed work on how Java language features are 
> used in real-world code. Their "Qualitas Corpus" consists of over 
> 100,000 classes - see http://www.cs.auckland.ac.nz/~ewan/corpus/
> 
> If someone showed that, say, a null check occurs on average every 15 
> lines of code in this corpus, and that null-safe operators could 
> remove those lines without adverse side effects, then that would be a
> real contribution to Project Coin.

I agree that using a standard, large corpus to empirically examine the 
utility of the Project Coin proposals would be a fine component of their 
evaluation.

-Joe


From Joe.Darcy at Sun.COM  Thu Apr  2 19:09:37 2009
From: Joe.Darcy at Sun.COM (Joe Darcy)
Date: Thu, 02 Apr 2009 19:09:37 -0700
Subject: Proposal: Sameness operators
In-Reply-To: <e32549de0904021649t3eb92475me79a85206143e7e@mail.gmail.com>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>
	<49D3B1E3.8070109@sun.com>
	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
	<4b4f45e00904020524p27741baeo40483e83d71dc768@mail.gmail.com>
	<275433EA-A420-42C8-891D-3B0C2629222A@zwitserloot.com>
	<49D54420.5090906@sun.com>
	<e32549de0904021649t3eb92475me79a85206143e7e@mail.gmail.com>
Message-ID: <49D56FE1.8080601@sun.com>

Tim Keith wrote:
> I would like to suggest calling the class java.lang.Objects, similar
> to java.util.Collections and java.util.Arrays.

Since this would be a utility class, I thought it would be better placed 
in java.util rather than java.lang.

> And it would be handy to also have in there a null-safe static method
> to help in implementing hashCode:
>     public static int hashCode(Object o) {
>         return o == null ? 0 : o.hashCode();
>     }

I've added this suggestion to the Sun bug.

Thanks,

-Joe


> -- Tim
> 
> On Thu, Apr 2, 2009 at 4:02 PM, Joe Darcy <Joe.Darcy at sun.com> wrote:
>> Reinier Zwitserloot wrote:
>>
>> [snip]
>>
>>> public static void is(Object x, Object y) {
>>>      if ( x == null ) return y == null;
>>>      return x.equals(y);
>>> }
>>>
>>> public static void is(Object x, int y) {
>>>     // Yes, you'd need a few gazillion is methods to cover all the
>>> primitives on either side, but 1 static import will grab all of them
>>> }
>>>
>>> ... loads more is methods
>>>
>>>
>>> Then same with lt, gt, le, ge.
>>>
>>> Then you could write:
>>>
>>> if ( is(a, b) ) {
>>>    //doStuff
>>> }
>>>
>>> Which is a small improvement.
>>>
>>> Add an ability to specify 'as infix' in static imports, and you have
>>> pretty much what we all want without backwards compatibility issues:
>>>
>>> import static java.lang.Equality.is infix;
>>>
>>> if ( a is b ) {
>>>    //do something
>>> }
>>>
>>> I'd consider that a large improvement.
>> Yes, in JDK 7 I'd like to see
>>
>>     6797535 Add shared two argument static equals method to the platform
>>     http://bugs.sun.com/view_bug.do?bug_id=6797535
>>
>> addressed in the platform.  I was thinking putting it in a place like a
>> new utility class java.util.Object.
>>
>> -Joe
>>
>>
> 



From brucechapman at paradise.net.nz  Thu Apr  2 20:59:32 2009
From: brucechapman at paradise.net.nz (brucechapman at paradise.net.nz)
Date: Fri, 03 Apr 2009 16:59:32 +1300 (NZDT)
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <49D56FAB.8090405@sun.com>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<1238711752.49d53dc8e0a4c@www.paradise.net.nz>
	<49D56FAB.8090405@sun.com>
Message-ID: <1238731172.49d589a4a3575@www.paradise.net.nz>

Comments inline

Bruce

Quoting Joe Darcy <Joe.Darcy at Sun.COM>:

> brucechapman at paradise.net.nz wrote:
> > Good idea,
> > 
> > Should they each be evaluated against the same corpus and what would 
> > be a suitable corpus?
> > 
> > http://en.wikipedia.org/wiki/Corpus_linguistics
> 
> On that front, Alex sent me the following:
> 
> > Analysis of a micro-corpus of your own or your company's code is
> > unscientific.
> > 
> > Ewan Tempero and his colleagues at the University of Auckland have 
> > done excellent, peer-reviewed work on how Java language features are 
> > used in real-world code. Their "Qualitas Corpus" consists of over 
> > 100,000 classes - see http://www.cs.auckland.ac.nz/~ewan/corpus/
> > 

OK,

I was aware of that one because the last JUG meeting here was about visualising
code and was working with that corpus.

The problem then is that the corpus is HUGE. Even the 20090202r version which
only has the latest release of each system (and is probably the appopriate one
for coin use) is 1.2Gb (my monthly broadband limit is 1Gb - I'd probably
sneakernet it from someone locally).  

Maybe this is one of those cases where it is better to take the analysis tools
to the corpus rather than the other way around. For that we'd need someone to
host the corpus and run jobs submitted against it.

Let me do some further research on that.

Bruce

> > If someone showed that, say, a null check occurs on average every 15 
> > lines of code in this corpus, and that null-safe operators could 
> > remove those lines without adverse side effects, then that would be a
> > real contribution to Project Coin.
> 
> I agree that using a standard, large corpus to empirically examine the 
> utility of the Project Coin proposals would be a fine component of their
> 
> evaluation.
> 
> -Joe
>  



From Joe.Darcy at Sun.COM  Thu Apr  2 21:30:57 2009
From: Joe.Darcy at Sun.COM (Joe Darcy)
Date: Thu, 02 Apr 2009 21:30:57 -0700
Subject: Of knapsacks and language features
Message-ID: <49D59101.6070400@sun.com>

A quick note on some additional considerations in language feature 
selection.

I view the selection of language proposals to be a kind of knapsack problem:

    http://en.wikipedia.org/wiki/Knapsack_problem

That is, each feature has some discrete size and complexity to implement 
and confers some improvement to the language.  There is a bounded size 
and complexity budget and the goal is maximizing the value held in the 
knapset, the value of improvements shipped in a release.

Of note is that implementing a language change has much more of a 
discrete size (or a small selection of possible sizes) rather than a 
continuous range of possible sizes.  In other words, because of the 
coordinated set of deliverables associated with a language change, it 
may be reasonable to implement 0% 50% or 100% of a possible feature but 
no other fraction.  And doing 50% of the feature might take 1/4 of the 
effort of doing the whole thing or 3/4 of that effort.

Even when precise costs and improvements can be quantified, because of 
these discrete sizes the "greedy" algorithm of putting the highest value 
/ cost item in the knapsack first can lead to globally poor results.

If nothing else, having a pre-pass to reduce the number of proposals 
being considered for further review greatly reduces the combinatorial 
possibilities of subsets of features that could be included in a release.

-Joe


From Joe.Darcy at Sun.COM  Thu Apr  2 21:48:46 2009
From: Joe.Darcy at Sun.COM (Joe Darcy)
Date: Thu, 02 Apr 2009 21:48:46 -0700
Subject: Opportunity Cost and Proposal Selection
In-Reply-To: <980366fa0904010733o5655fe5di10aa2c44883f7a6e@mail.gmail.com>
References: <980366fa0904010733o5655fe5di10aa2c44883f7a6e@mail.gmail.com>
Message-ID: <49D5952E.9040602@sun.com>

On 04/01/09 07:33 AM, Glenn A. Marshall wrote:
> Will the details of the proposal evaluations be published?  

In general, no.  I plan to write up some general retrospective comments 
on the proposals that were and were not chosen for further consideration 
in the coming weeks.  However, there will be more detailed analysis and 
discussion to get the set of "for further consideration" proposals down 
to the final set of proposals.

> The thinking here is that for proposals that almost made the cut, 
> perhaps the evaluations would reveal where a bit more work might push 
> them over the line for the next round - increase benefit/decrease cost.
>
> This is assuming there will be a next round.
>
> Any thoughts on round II?

I think we have to see how round I works out first ;-)

>   It would seem to be worth considering, given the level of interest.  
> It would, of course, have to wait until Java 8, but why not start early? 
>
> Surely you're busy with round I for now, but perhaps there could be a 
> parallel effort, with the initial effort primarily around email.

Thinking about and working on possible language is great fun of course, 
but I think in the near term the Project Coin list needs to focus on JDK 
7 related work.

> thanks for doing all of this,

It's an interesting project!

-Joe




From vapor1 at teleport.com  Thu Apr  2 23:33:14 2009
From: vapor1 at teleport.com (Derek Foster)
Date: Fri, 3 Apr 2009 02:33:14 -0400 (EDT)
Subject: PROPOSAL: Simplified StringBuffer/StringBuilder syntax
Message-ID: <29484356.1238740394998.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>

Replies inline.

-----Original Message-----
>From: Reinier Zwitserloot <reinier at zwitserloot.com>
>Sent: Mar 31, 2009 5:59 AM
>To: Mark Thornton <mthornton at optrak.co.uk>
>Cc: coin-dev at openjdk.java.net
>Subject: Re: PROPOSAL: Simplified StringBuffer/StringBuilder syntax
>
>+ being overloaded to also mean string concatenation was a mistake in  
>java 1.0*. Let's not enshrine it by making more of them.

Actually, I agree with this. I think they should have come up with a new "concatenation" operator instead of trying to reuse an existing one. However, + is what we have, and that's not going to change. However, it is obnoxious because it isn't really "complete" -- it takes care of one trivial use case in concatenating strings, but it doesn't handle the larger issue of what to do when all the concatenation doesn't occur in the same expression, and it isn't consistent in its coverage of the family of related types (String, StringBuffer, and StringBuilder) that are really used in creating strings.

My intent wasn't to create new operators -- it was to fix odd holes and (fairly inconvenient) missing features in the behavior of the existing ones. I just want the behavior of +, =, and += to behave consistently and intuitively when used with the classes that are used to generate Strings (StringBuffer, StringBuilder, and String). For anybody who knows that + means concatenation of strings, it's fairly obvious what:

StringBuilder foo = "abc";
foo += "def";

is supposed to do.

>Also, if '+' will call .append on any appendables, I guarantee you,  
>the first thing some clown will create is this:
>
>public class BigInteger2 extends Number implements Appendable {
>    //I'm a BigInteger that supports +! Oh - and I'm mutable too :/
>}

Two observations:

1) If you are programming alongside clowns, it's probably time to find a new job.

2) This is probably the least of the damage that a clown can do when armed with a Java compiler. See observation #1.


>Specific problems with the entire concept:
>
>1. + so far is strictly a 'create new object with result' kind of of  
>operation. "x + y" is an expression that does not change either the  
>value of x, or the value of y. It just creates a new value, and that  
>is the result of the expression. The same thing happens with strings,  
>but if you apply this to appendables, all of a sudden you get "x + y"  
>takes y and appends it to x. That is just strange.

That's not what the proposal says. It says "x = x + y" takes y and appends it to x, if x is a StringBuilder and y is a String. 

The append is only done so that this happens efficiently (by eliminating the need to create an unnecessary temporary String object). It's an optimization for an expression in a very common, specific pattern involving multiple operators which is known to be evaluated inefficiently if not treated as a special case. Compilers do this sort of large-scale optimization frequently for a variety of reasons. From the user's point of view, there is no difference in behavior.

"x + y" by itself does what it has always done.

>2. The whole point of not allowing operator overloading is to make  
>sure any given snippet of the form 'x + y' serves as an anchor of  
>sorts: You know nothing too weird is going on in those 3 characters.  
>If + can mean: Mathematical plus, -OR- string concatenation (utterly  
>unrelated), -OR- anything anybody may have cooked up by implementing  
>Appendable, then there's zero conservative anchoring left for the +  
>symbol. Ergo I assert that doing this is as bad as having full blown  
>operator overloading. Actually, it's worse - at least full blown  
>operator overloading has proper names for things ('+' is plus and not  
>append), and allows one to write proper libraries for it.

I personally am not particularly against operator overloading as a general principle. I've used C++ for many years and never really had a problem with someone abusing it. I've never really understood certain parts of the Java community's shock and horror at the concept of having it in a language -- lots of languages have it, and it doesn't really seem to be one of the major problems with any of them. (C++, for instance, has WAY bigger problems than that!) Whether it gets abused or not mostly depends on the culture and training of the average person who uses that particular language, not the features they have available to them. Also, libraries which aren't useful and reasonably intuitive don't tend to become widespread in their use. Operator overloading is only one of many possible ways that an API could be designed either well or poorly. As always, the market decides.

In any case, having limited use of operator overloading designed within the platform by the people who maintain it is presumably a lot less likely to lead to abuse than to turn the public at large loose on it, so the general arguments against operator overloading ("Everybody and his dog will define operators to have unintuitive meanings at every opportunity!") don't really seem to apply in this case.

Also, having operator overloading based on system interfaces which have defined meanings (and which may well be designed in ways that make them awkward to use in cases where those meanings do not apply) seems far less prone to abuse than the C++ model of "any operator can be redefined by anybody at any time for any purpose, as long as you remember to include the appropriate header file."

With regards to "things people cook up using Appendable", presumably those will be things for which appending strings is a meaningful operation, right? Otherwise, they shouldn't be implementing the Appendable interface in the first place (and it would be awkward to do so, since "append(String)" isn't the only method on it, and the others are harder to implement). Since that's what the interface is really defined for, why is it a bad thing for them to be able to use the same syntax for appending strings to something with that mandate as it would be for appending them to other things, like Strings?

Note that I'm not really all that sure that I'll add the Appendable concept to the proposal, since I have other concerns about it (such as the fact that append(int) isn't allowed, so there would be a lot of calling of String.valueOf(?) on the arguments). I'll have to think a bit more on that issue.

>*) string concat and numeric plus are unrelated to each other. In  
>fact, numeric plus ought to be commutative, which string concat isn't  
>(commutative = swapping arguments doesn't change result). It weakens  
>the information that a raw + sign is capable of telling you. There are  
>pros and cons to having a strict interpretation of a + sign, but given  
>that java does not allow operator overloading, the onus appears to be  
>on those in favour of weakening it to prove why this is acceptable.

Operator + is already defined within the language to mean concatenation as well as addition. You may argue that this shouldn't be the case, and I may even agree with you, but the fact remains that it is so, and neither of us can change that fact at this point. 

Given that we do, in fact, have operator + for strings meaning concatenation, I think that it is logical for us to make sure that the full set of operations that have related semantics all work together in a fashion that makes sense, given that + means concatenation for strings. Otherwise, we have a language that's not just inconsistent in the one detail that + has multiple meanings -- we have a language that's arbitrary and capricious with regards to which apparently similar operations are allowed versus which ones aren't.

That's harder for users to learn. "I'm supposed to use StringBuilder to build strings. Why can't I build them with nice syntax like I'm used to with expressions involving Strings? Why does making a small change (building a string in multiple statements versus a single statement) mean I have to use an entirely different syntax to get a similar level of efficiency?". Also, in this case, it leads to a lot of unnecessarily verbose code or unnecessarily inefficient code being written.

Derek

>  --Reinier Zwitserloot
>
>
>
>On Mar 28, 2009, at 21:14, Mark Thornton wrote:
>
>> Derek Foster wrote:
>>>
>>> CONCATENATION: An expression of the form
>>>
>>>    SB += S
>>>
>>> where SB is an RValue expression of type StringBuilder, and S is an  
>>> expression of type String, shall be considered to have meaning as  
>>> defined below. (Previously, this was a syntax error)
>>>
>>> SELF-CONCATENATION:
>>>
>>> An expression of the form
>>>
>>>    SB = SB + S
>>>
>> Why not allow any Appendable in these cases?
>>
>> Mark Thornton
>>
>
>



From peter.levart at gmail.com  Thu Apr  2 23:35:28 2009
From: peter.levart at gmail.com (Peter Levart)
Date: Fri, 3 Apr 2009 08:35:28 +0200
Subject: Proposal: Sameness operators
In-Reply-To: <49D54420.5090906@sun.com>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>
	<49D3B1E3.8070109@sun.com>
	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
	<4b4f45e00904020524p27741baeo40483e83d71dc768@mail.gmail.com>
	<275433EA-A420-42C8-891D-3B0C2629222A@zwitserloot.com>
	<49D54420.5090906@sun.com>
Message-ID: <aad309390904022335t253529ees538f0287f5a0cb93@mail.gmail.com>

On Fri, Apr 3, 2009 at 1:02 AM, Joe Darcy <Joe.Darcy at sun.com> wrote:

>
> Yes, in JDK 7 I'd like to see
>
>     6797535 Add shared two argument static equals method to the platform
>     http://bugs.sun.com/view_bug.do?bug_id=6797535
>
> addressed in the platform.  I was thinking putting it in a place like a
> new utility class java.util.Object.
>
> -Joe
>
>
Maybe not java.util.Object but java.util.Objects. Using the same name as a
java.lang class prevents IDEs to suggest the imports since java.lang classes
are already in scope. You would have to manually type import statements each
time you wanted to use this method. Nobody does this nowadays. It would be
very inconvenient.

Regards, Peter


From Joe.Darcy at Sun.COM  Thu Apr  2 23:47:37 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Thu, 02 Apr 2009 23:47:37 -0700
Subject: Proposal: Sameness operators
In-Reply-To: <aad309390904022335t253529ees538f0287f5a0cb93@mail.gmail.com>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>
	<49D3B1E3.8070109@sun.com>
	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
	<4b4f45e00904020524p27741baeo40483e83d71dc768@mail.gmail.com>
	<275433EA-A420-42C8-891D-3B0C2629222A@zwitserloot.com>
	<49D54420.5090906@sun.com>
	<aad309390904022335t253529ees538f0287f5a0cb93@mail.gmail.com>
Message-ID: <49D5B109.2020007@sun.com>

Peter Levart wrote:
>
> On Fri, Apr 3, 2009 at 1:02 AM, Joe Darcy <Joe.Darcy at sun.com 
> <mailto:Joe.Darcy at sun.com>> wrote:
>
>
>     Yes, in JDK 7 I'd like to see
>
>         6797535 Add shared two argument static equals method to the
>     platform
>         http://bugs.sun.com/view_bug.do?bug_id=6797535
>
>     addressed in the platform.  I was thinking putting it in a place
>     like a
>     new utility class java.util.Object.
>
>     -Joe
>
>
> Maybe not java.util.Object but java.util.Objects. Using the same name 
> as a java.lang class prevents IDEs to suggest the imports since 
> java.lang classes are already in scope. 

Yes, I meant to type "java.util.Objects"  -- having a class other than 
java.lang.Object named "Object" is just wrong!

-Joe



From vapor1 at teleport.com  Fri Apr  3 00:04:18 2009
From: vapor1 at teleport.com (Derek Foster)
Date: Fri, 3 Apr 2009 03:04:18 -0400 (EDT)
Subject: Naked dot - accessing object fields through unqualified
Message-ID: <19432589.1238742258930.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>

Replies inline.

-----Original Message-----
>From: Reinier Zwitserloot <reinier at zwitserloot.com>
>Sent: Mar 31, 2009 9:03 AM
>To: Derek Foster <vapor1 at teleport.com>
>Cc: coin-dev at openjdk.java.net
>Subject: Re: Naked dot - accessing object fields through unqualified "." [C1]
>
>'Self-assignment is forbidden' would not be backwards compatibile.  
>Yes, such code would most likely be a bug, but its still an issue. It  
>would have to be a warning, at best.

Personally, I think it should be an error, since there seems to be no valid reason to do it, and it almost certainly indicates a bug. I think that compilers should default to being in a 'strict' mode where things like this that have been found to be bad ideas with virtually no upside are treated as illegal, even if that makes them not fully backwards compatible. For backwards compatibility, there could be a command-line switch to turn off strict mode if necessary for compiling old code.

Some other things I'd like to see in this category:

* Having an abstract class with a constructor that has 'public' or 'private' access.

* Using C-style array declarations. (int x[] instead of int[] x)

I could probably think of a few more.

>However:
>
>Every single external java compiler I know of will warn you when you  
>self-assign. Eclipse does it. So does netbeans. So does IDEA. So does  
>pmd. So does findbugs.

Mere warnings are not enough to stop people from doing this sort of thing, especially when the warning message is buried in 436 other warning messages about code which is less unambiguously broken than this is. (Note: I *HATE* it when people ignore compiler warnings like this, but I am speaking from experience when I say that it usually takes years to convince a company to clean up its act.) Unfortunately, I have worked for lots of companies that routinely ignore warnings.

>If you internalize the self-assignment warning, where do you stop?  
>There are literally hundreds of 'duh, that must be a bug' warnings you  
>could generate. Not all of them are as obvious, or as non-contentious,  
>as 'self assignment'. So, where do you stop? Do we use the glacial  
>nature of the language changes process to set this up?

I think that when a practice is almost always problematic, is easy to fix, and has no legitimate purpose (and/or has an easy workaround in the few cases that it is legitimate), it should be made an error (with the caveats above). I don't think that we should carry along every single design mistake in the 1.0 edition of the Java Language Standard with us until the end of time. The ability to achieve backwards compatibility is important (hence the ability to turn off strict mode I described above), but clarity of language design and preventing common errors is too. Otherwise, the amount of code which contains the error in question just keeps growing over time.

> I say: No. The  
>community has done a fine job of addressing these issues by creating  
>code checkers.

In my experience, the community, by and large, does not use code checkers. Relatively few companies do. Again, I wish it were otherwise, but the truth is that most companies assume that if something passes the checks done by the compiler, it's probably fine. Having tried to introduce them into companies a few times, I can report that most software engineers really don't want to be bothered with them (and are convinced that checkers won't find any bugs important enough to justify the time spent learning to use them and cleaning up lots of innocuous warnings just for the sake of the tool). Again, I thoroughly disagree with that philosophy, but that's what I have heard repeatedly in industry.

Also, using a code checker is often a painful experience if you are forced to use a framework written by people who don't use them.

The other issue is that every code checker checks for a different set of things. Just because your code passes your code checker's rules doesn't mean it will pass mine, or vice versa. The Sun Java compiler as of a specific version, at least, is the same for everybody.

> So, I'd instead suggest:
>Any improvements to java core in this area should focus on improving  
>the ability for external tools to integrate better. For example, a way  
>to extend @SuppressWarnings with additional keywords would be great. A  
>way to let javac auto-find (via the SPI system) 'warning/error'  
>plugins would be another fine idea. Having any kind of plugin system  
>for the official javac to give other tools a go at creating warnings  
>and errors on the AST that javac's parser is building would be good  
>already, using SPI to find these automatically is just one way of  
>doing it. I'm not sure APT is quite right for the job; I don't want to  
>litter annotations to the gist of '@ExtensivelyCheckMe' all over the  
>place.

I'm certainly in favor of making life easier for code checkers. However, checkers that don't get used are no better than ones that don't exist. Javac (or jikes, etc.) gets used every time someone compiles a program. That means it's going to have far more influence on the correctness of the majority of Java code than any other tool.

Derek

>
>
>  --Reinier Zwitserloot
>
>
>
>On Mar 29, 2009, at 04:42, Derek Foster wrote:
>
>> The major problem I have with this proposal is that it does not  
>> address the point of why I use a prefix on field names. As such, I  
>> would still continue to use a prefix even if this proposal were  
>> implemented.
>>
>> In short, I use a prefix to avoid typographical mistakes, like this  
>> one:
>>
>> void setFoo(Thing foob) { // Typo!
>>    this.foo = foo;
>> }
>>
>> This will compile, and no warnings are produced, but it ends up  
>> assigning foo to itself, which is not what was intended.
>>
>> Your proposal has exactly the same problem:
>>
>> void setFoo(Thing foob) { // Typo!
>>    .foo = foo;
>> }
>>
>> It therefore does not substitute for a field prefix, which WILL fix  
>> the problem:
>>
>> void setFoo(Thing foob) { // Typo!
>>    _foo = foo; // ERROR! Undefined variable 'foo'.
>> }
>>
>> So unless you had some way to make use of the dot prefix mandatory  
>> and the only legal way to access fields (which I would like, but  
>> which would be an extremely backwards-incompatible change that will  
>> never happen in Java), I don't see that adding an optional dot  
>> prefix helps the situation except to reduce typing in constructor  
>> and setter methods slightly.
>>
>> (Note: I would love a "self-assignment is forbidden" change to Java.  
>> If I have time after my other proposals, I might write one up.  
>> (Anyone else want to volunteer? This one is easy!) I might be  
>> willing to forego prefixes and use the "this.foo = foo" approach, or  
>> even the ".foo = foo" approach, if I was sure it wouldn't cause me  
>> to fall into the self-assignment trap.)
>>
>> Derek
>>
>>
>



From vapor1 at teleport.com  Fri Apr  3 00:21:24 2009
From: vapor1 at teleport.com (Derek Foster)
Date: Fri, 3 Apr 2009 03:21:24 -0400 (EDT)
Subject: Proposal: Sameness operators
Message-ID: <12090747.1238743285109.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>



-----Original Message-----
>From: Tom Hawtin <Thomas.Hawtin at Sun.COM>
>Sent: Mar 31, 2009 7:09 AM
>To: Derek Foster <vapor1 at teleport.com>
>Cc: coin-dev at openjdk.java.net
>Subject: Re: Proposal: Sameness operators
>
>Derek Foster wrote:
>> a $$ b    "same as":              a==null ? b==null : a.equals(b), or a == b for primitive types.
>
>$ and $$ are valid identifier in (existing) Java. Not a lot of people 
>know that. http://jroller.com/tackline/entry/things_i_didn_t_know

I, however, do know it. In fact, I mentioned it in the "Breaking Changes" section of my proposal. However, use of generated code is rare in general, and fixing a code generator to comply with a new language version only has to be done once. I considered it a lesser risk than introducing syntax that might break non-generated programs, which are very common indeed.

I am open to other operators being used instead of the ones I suggested. I considered >#, <#, ##, and !#, for instance, but I thought that too many people might want to use # for closure-related things. Mostly, I wanted readability and understandability. The idea is you can just replace an = (which means "object identity" aka "equals") with a $ (which means "object equality" aka "sameness") and the related operators tend to mean what you would expect them to.

>> a !$ b    "not same as":          a==null ? b!=null : !a.equals(b), or a != b for primitive types.
>> a >$ b    "greater than or same": a.compareTo(b) >= 0, or a >= b for primitive types.
>> a <$ b    "less than or same":    a.compareTo(b) <= 0, or a <= b for primitive types.
>
>That's going to be jolly confusing for BigDecimal users (but I guess 
>that is not a state change).

Personally, I find

if (a >$ b) { do stuff }
if (a $$ b) { do stuff }

a lot less confusing than:

if (a.compareTo(b) >= 0) { do stuff }
if (a == null ? b == null : a.equals(b)) { do stuff }

so I would hope that these would eventually reduce the confusion, not add to it. Really, the confusion is already there in how or if classes like BigDecimal implement interfaces like Comparable. (Which maybe was your point.)

Derek



From mthornton at optrak.co.uk  Fri Apr  3 00:33:34 2009
From: mthornton at optrak.co.uk (Mark Thornton)
Date: Fri, 03 Apr 2009 08:33:34 +0100
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <1238731172.49d589a4a3575@www.paradise.net.nz>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>	<1238711752.49d53dc8e0a4c@www.paradise.net.nz>	<49D56FAB.8090405@sun.com>
	<1238731172.49d589a4a3575@www.paradise.net.nz>
Message-ID: <49D5BBCE.2030102@optrak.co.uk>

brucechapman at paradise.net.nz wrote:
> OK,
>
> I was aware of that one because the last JUG meeting here was about visualising
> code and was working with that corpus.
>
> The problem then is that the corpus is HUGE. Even the 20090202r version which
> only has the latest release of each system (and is probably the appopriate one
> for coin use) is 1.2Gb (my monthly broadband limit is 1Gb - I'd probably
> sneakernet it from someone locally).  
>   
Ouch, however I'm sure there are quite a few of us with substantially 
more generous download allowances.

Mark Thornton



From forax at univ-mlv.fr  Fri Apr  3 00:34:20 2009
From: forax at univ-mlv.fr (=?ISO-8859-1?Q?R=E9mi_Forax?=)
Date: Fri, 03 Apr 2009 09:34:20 +0200
Subject: Proposal: Sameness operators
In-Reply-To: <49D5B109.2020007@sun.com>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>	<49D3B1E3.8070109@sun.com>	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>	<4b4f45e00904020524p27741baeo40483e83d71dc768@mail.gmail.com>	<275433EA-A420-42C8-891D-3B0C2629222A@zwitserloot.com>	<49D54420.5090906@sun.com>	<aad309390904022335t253529ees538f0287f5a0cb93@mail.gmail.com>
	<49D5B109.2020007@sun.com>
Message-ID: <49D5BBFC.7040705@univ-mlv.fr>

Joseph D. Darcy a ?crit :
> Peter Levart wrote:
>   
>> On Fri, Apr 3, 2009 at 1:02 AM, Joe Darcy <Joe.Darcy at sun.com 
>> <mailto:Joe.Darcy at sun.com>> wrote:
>>
>>
>>     Yes, in JDK 7 I'd like to see
>>
>>         6797535 Add shared two argument static equals method to the
>>     platform
>>         http://bugs.sun.com/view_bug.do?bug_id=6797535
>>
>>     addressed in the platform.  I was thinking putting it in a place
>>     like a
>>     new utility class java.util.Object.
>>
>>     -Joe
>>
>>
>> Maybe not java.util.Object but java.util.Objects. Using the same name 
>> as a java.lang class prevents IDEs to suggest the imports since 
>> java.lang classes are already in scope. 
>>     
>
> Yes, I meant to type "java.util.Objects"  -- having a class other than 
> java.lang.Object named "Object" is just wrong!
>
> -Joe
>   
or fun, all programs that use import java.util.* will break.

R?mi



From vapor1 at teleport.com  Fri Apr  3 00:45:56 2009
From: vapor1 at teleport.com (Derek Foster)
Date: Fri, 3 Apr 2009 03:45:56 -0400 (EDT)
Subject: PROPOSAL: Underscores in numbers
Message-ID: <31694231.1238744756544.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>



-----Original Message-----
>From: Bruce Chapman <brucechapman at paradise.net.nz>
>Sent: Mar 31, 2009 3:14 AM
>To: Derek Foster <vapor1 at teleport.com>
>Cc: coin-dev at openjdk.java.net
>Subject: Re: PROPOSAL: Underscores in numbers
>
>Derek,
>thanks for writing this up, it saved me doing it. (and it would 
>complement my integer literal proposals nicely)

You're welcome!

Personally, I definitely hope that your type suffixes for bytes and shorts proposal goes through. Lack of that seems a weird omission in the language, and I am tired of casting to bytes.

I am not as keen on the other proposal with its "0h52" notation, however. That seems to be mixing radix and type in a way that is not very consistent with how the rest of the language works.

>A couple of comments:
>
>1. I don't really like most of your decimal examples because (apart from 
>the money one) although we talk about these as numbers, they are not 
>numbers really, just identifiers whose significant elements consist 
>solely of digits. As an explanation, prepending 00 to the front of any 
>of these would yield a different (or invalid) phone/credit card/SS 
>number, whereas prepending 00 to a number does not (but not in java 
>where it makes an octal or a compiler error :), similarly add two 
>together or subtracting them makes no sense.

I think that both pure numbers (underscores used for order-of-magnitude grouping of digits) and formatted numbers (underscores used in standard groups) like these are both valid use cases for this feature. They are definitely different use cases, but it is nice that the feature can be used for both.

>Real countable number examples that could be useful are populations, 
>national debt, Long.MAX_VALUE etc, as well as the hex and binary 
>examples you use later.

I'm not averse to adding more examples. I tried to make each existing example show a different likely use of the feature. So I really only needed one example to show the use of underscores to group big numbers in three-digit chunks (as commas would be used, for Americans anyway).

>I am not convinced of the utility of multiple consecutive underscore 
>separators, and I think the example that uses that is confusing and 
>asking for trouble. IMHO it would add to the value if you removed that 
>option, but you might have some good use case you are thinking about. 
>Similarly for underscore at either end seems strange. It might take more 
>effort to describe it such that these are illegal, but I don't think 
>anyone would complain at the absence of that form.

I left them in because I couldn't see a good reason to exclude them, and it's possible that someone might want to use them for some form of formatting that I haven't thought of. Perhaps someone might want to space the digits out to make a number line up with the characters in a comment field that's above it, for instance:

//       AreaCode Exchange Number
int x =       555______555___1212;
int y =       555______857___5309;

The question really is whether adding multiples causes actual problems. As far as I can see, it doesn't. If someone is abusing them to write unclear code, then it seems to me that that person is really the problem. I don't think the feature in and of itself particularly encourages abuse. It could be used in ways that make code clearer rather than harder to read. I don't really expect it to be used much, though.

>Any reason why in the syntax you didn't just add underscore to the 
>various XXXXDigits forms (and maybe change the name a little) rather 
>than the more complex approach, then describe the erasure of the 
>underscore in the description of each form?

Because that would have made things like "0x_" or "_._" be parseable as syntactically legal numbers, which would then become illegal once the underscores were removed.

Getting the grammar right for the underscores proposal turned out to be much trickier than I had anticipated. (It probably took me two hours.) I initially did it wrong, and had to revise it once I realized that I couldn't ever allow an underscore to appear if it wasn't next to a digit.

Derek

>Bruce
>
>Derek Foster wrote:
>> When I posted my Binary Literals proposal, I got feedback from several people stating that they would like to see a proposal regarding underscores in numbers, in the style of Ruby, since that would make numbers of all types (but especially binary ones) easier to read. Here is such a proposal.
>>
>> AUTHOR(S): Derek Foster
>>
>> OVERVIEW
>>
>> In Java, currently, numbers of various types currently are expressed in their pure form, as a long string of digits possibly interspersed with other punctuation (periods, an exponent specifier, etc.) needed to separate distinct sections of the number. While this is easy for a compiler to process, it is often difficult for a human being to visually parse.
>>
>> The ability of a human to visually separate separate items tops out somewhere near "seven plus or minus two" items. Research done by telephone companies suggests that for many practical purposes, the longest string of numbers an average human can successfully hold in memory at a time is around three or four. Also, it is difficult for the human eye to find common positions in numbers that have no break in their visual structure.
>>
>> As a result, most numbers that humans deal with in day-to-day life have separators included in them to break the long sequence of digits into manageable chunks that are easy to deal with as separate entities. This includes items such as (apologies to non-USA readers...):
>>
>> Phone numbers:           555-555-1212
>> Credit card numbers:     1234-5678-9012-3456
>> Social security numbers: 999-99-9999
>> Monetary amounts:        $12,345,132.12
>>
>> and a wide variety of other types of numbers.
>>
>> However, Java provides no way to add these kinds of visual separators into a number. Java expects the number to be essentially an unbroken string of digits.
>>
>> This proposal suggests that Java follow the lead of the Ruby programming language in allowing the underscore character to be inserted into numbers in most positions, for readability purposes.
>>
>>
>> FEATURE SUMMARY:
>>
>> Java numeric literals will allow underscores to be placed in (nearly) arbitrary positions within the number, at the programmer's discretion, for readability purposes. These underscores shall be ignored by the compiler for the purposes of code generation.
>>
>>
>> MAJOR ADVANTAGE:
>>
>> Programmers won't have to visually parse long strings of digits (a task humans are quite poor at). The internal digit-oriented structure of many numbers can be made more clear.
>>
>>
>> MAJOR BENEFIT:
>>
>> Increased readability of code.
>>
>>
>> MAJOR DISADVANTAGE:
>>
>> The number parsers in the Java compiler would have to be adjusted to parse and ignore the underscores. This is a small amount of effort, but nonzero. There might also be some small performance impact.
>>
>> If someone were to use this feature inappropriately, it could result in difficult to read code.
>>
>>
>> ALTERNATIVES:
>>
>> Do without separators in numbers, or use some other character for them.
>>
>>
>> EXAMPLES
>>
>>
>> SIMPLE EXAMPLE: Show the simplest possible program utilizing the new feature.
>>
>> int phoneNumber = 555_555_1212;
>>
>>
>> ADVANCED EXAMPLE:
>>
>> long creditCardNumber = 1234_5678_9012_3456L;
>> long socialSecurityNumbers = 999_99_9999L;
>> float monetaryAmount = 12_345_132.12;
>> long hexBytes = 0xFF_EC_DE_5E;
>> long hexWords = 0xFFEC_DE5E;
>> long maxLong = 0x7fff_ffff_ffff_ffffL;
>> long alsoMaxLong = 9_223_372_036_854_775_808L;
>> double whyWouldYouEverDoThis = 0x1_.ffff_ffff_ffff_fp10_23;
>>
>> (Additionally, if binary literals are ever added to the Java language, the following might also be possible...
>>    byte nybbles = 0b0010_0101;
>>    long bytes = 0b11010010_01101001_10010100_10010010;
>>    int weirdBitfields = 0b000_10_101;
>> )
>>
>> Note that underscores can be placed around and between digits, but that underscores cannot be placed by themselves in positions where a string of digits would normally be expected:
>>
>> int x1 = _52;  // This is an identifier, not a numeric literal.
>> int x2 = 5_2;  // OK. (decimal literal)
>> int x2 = 52_;  // OK. (decimal literal)
>> int x3 = 5_______2; // OK. (decimal literal.)
>>
>> int x4 = 0_x52;  // Illegal. Can't put underscores in the "0x" radix prefix.
>> int x5 = 0x_52;  // OK. (hexadecimal literal)
>> int x6 = 0x5_2;  // OK. (hexadecimal literal)
>> int x6 = 0x52_;  // OK. (hexadecimal literal)
>> int x6 = 0x_;    // Illegal. Not a valid hex number with the underscore removed.
>>
>> int x7 = 0_52;   // OK. (octal literal)
>> int x7 = 05_2;   // OK. (octal literal)
>> int x8 = 052_;   // OK. (octal literal)
>>
>>
>> DETAILS
>>
>> SPECIFICATION:
>>
>> DECIMALS:
>>
>> Section 3.10.1 ("Integer Literals") of the Java Language Specification 3rd edition shall be modified like so:
>>
>>     Underscores:
>>             _
>>             _ Underscores
>>
>>     DecimalNumeral:
>>             0
>>             NonZeroDigit DigitsAndUnderscores_opt
>>
>>     DigitsAndUnderscores:
>>             Underscores_opt Digit Underscores_opt
>>             DigitsAndUnderscores Digit Underscores_opt
>>
>>     Digit:
>>             0
>>             NonZeroDigit
>>
>>     NonZeroDigit: one of
>>             1 2 3 4 5 6 7 8 9
>>
>>     HexNumeral:
>>         0 x HexDigitsAndUnderscores
>>         0 X HexDigitsAndUnderscores
>>
>>     HexDigitsAndUnderscores:
>>         Underscores_opt HexDigit Underscores_opt
>>         Underscores_opt HexDigit HexDigitsAndUnderscores
>>
>>     HexDigit: one of
>>             0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F
>>
>>     OctalNumeral:
>>             0 OctalDigitsAndUnderscores
>>
>>     OctalDigitsAndUnderscores:
>>             Underscores_opt OctalDigit Underscores_opt
>>             Underscores_opt OctalDigit OctalDigitsAndUnderscores
>>
>>     OctalDigit: one of
>>             0 1 2 3 4 5 6 7
>>
>> Section 3.10.2 ("Floating-Point Literals") would be modified as follows:
>>
>>
>>     FloatingPointLiteral:
>>             DecimalFloatingPointLiteral
>>             HexadecimalFloatingPointLiteral
>>
>>     DecimalFloatingPointLiteral:
>>           Digit DigitsAndUnderscores_opt . DigitsAndUnderscores_opt ExponentPart_opt FloatTypeSuffix_opt
>>           . DigitsAndUnderscores ExponentPartopt FloatTypeSuffix_opt
>>           Digit DigitsAndUnderscores_opt ExponentPart FloatTypeSuffix_opt
>>           Digit DigitsAndUnderscores_opt ExponentPart_opt FloatTypeSuffix
>>
>>     ExponentPart:
>>             ExponentIndicator SignedInteger
>>
>>     ExponentIndicator: one of
>>             e E
>>
>>     SignedInteger:
>>             Sign_opt DigitsAndUnderscores
>>
>>     Sign: one of
>>             + -
>>
>>     FloatTypeSuffix: one of
>>             f F d D
>>
>>     HexadecimalFloatingPointLiteral:
>>             HexSignificand BinaryExponent FloatTypeSuffix_opt
>>
>>     HexSignificand:
>>             HexNumeral
>>             HexNumeral .
>>             0x HexDigitsAndUnderscores_opt . HexDigitsAndUnderscores
>>             0X HexDigitsAndUnderscores_opt . HexDigitsAndUnderscores
>>
>>     BinaryExponent:
>>             BinaryExponentIndicator SignedInteger
>>
>>     BinaryExponentIndicator:one of
>>             p P
>>
>>
>> COMPILATION:
>>
>> Numbers containing underscores are to be parsed and evaluated by the compiler exactly as if the underscores were not present. The above grammar ensures that removing underscores will not result in an unparseable number.
>>
>> A simple strategy for achieving this is that once a number has been parsed by the compiler lexer and determined to be syntactically valid according to the above grammar, then if the number contains any underscores, then all underscores in it may be removed (by something as simple as numberAsString.replaceAll("_","")) before passing the number on to the code that would normally have parsed the number prior to this proposal.
>>
>> More performant approaches are certainly possible.
>>
>>
>> TESTING: How can the feature be tested?
>>
>> A variety of literals may be generated, of the cross product of each of the following radicies:
>>
>>     hex, decimal, octal
>>
>> with each of the following types:
>>
>>     byte, char, short, int, long, float, double
>>
>> such that for each possible numeric field in the result, that one or more underscores are inserted at the beginning, in the middle, and at the end of the digits.
>>
>> Note that the above grammar is specifically designed to disallow any underscores from appearing which are not either preceded by or followed by a digit.
>>
>>
>> LIBRARY SUPPORT:
>>
>> Methods such as Integer.decode(String) and Long.decode(String) should probably be updated to ignore underscores in their inputs, since these methods attempt to parse according to Java conventions.
>>
>> I suggest that methods such as Integer.parseInt(), Float.parseFloat(), etc. should probably NOT be updated to ignore underscores, since these methods deal with numbers in their pure form, and are more focused and much more widely used. To alter them to ignore underscores would introduce ambiguity in (and have a performance impact on) various parsing code that uses them.
>>
>>
>> REFLECTIVE APIS:
>>
>> No changes to reflective APIs are needed.
>>
>>
>> OTHER CHANGES:
>>
>> No other changes are needed.
>>
>>
>> MIGRATION:
>>
>> Underscores can be inserted into numbers within an existing code base as desired for readability.
>>
>>
>> COMPATIBILITY
>>
>> BREAKING CHANGES:
>>
>> Since use of underscores within numbers was previously a syntax error, this should not break any existing programs.
>>
>>
>> EXISTING PROGRAMS:
>>
>> This feature does not affect the format of class files. It is purely a notational convenience. Hence, interaction with existing class files would not be affected.
>>
>> REFERENCES
>>
>> EXISTING BUGS:
>>
>> A search of the Bug Database did not find any bug ID's related to this proposal.
>>
>> URL FOR PROTOTYPE (optional):
>>
>> None.
>>
>>
>>
>>   
>



From vapor1 at teleport.com  Fri Apr  3 00:57:06 2009
From: vapor1 at teleport.com (Derek Foster)
Date: Fri, 3 Apr 2009 03:57:06 -0400 (EDT)
Subject: PROPOSAL: Auto-assignment Parameters
Message-ID: <31069284.1238745426303.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>



-----Original Message-----
>From: Reinier Zwitserloot <reinier at zwitserloot.com>
>Sent: Mar 31, 2009 9:05 AM
>To: Derek Foster <vapor1 at teleport.com>
>Cc: coin-dev at openjdk.java.net
>Subject: Re: PROPOSAL: Auto-assignment Parameters
>
>Derek, if this proposal will save you a lot of typing, I think you're  
>doing it wrong. Thare are many tools that will auto-generate POJOs for  
>you, including whatever setter you prefer. Most IDEs have this in  
>their 'source' or 'refactor' menu, for example.

It wasn't the typing of creating them in the first place that I had in mind, but what comes after that.

I would explain more on that point, but it seems you have saved me the trouble:

>What annoys me about these tools is that they are one-way operations.  
> From seeing the multiple pages of POJO auto-generated code (incl.  
>hashCode, equals, toString, and constructor, and in some cases, the  
>auto-generated builder as well), I cannot ascertain quickly if this is  
>'just' the usual auto-generated boilerplate, or if there's a fun  
>surprise in there someplace (like some field being excluded for equals/ 
>hashCode purposes, or a missing getter, or some such). This makes  
>POJOs spectacularly unmaintainable compared to the low impact they  
>should be having, in java. It's also somewhat difficult (but certainly  
>not impossible) to change things that were used to auto-generate code,  
>such as changing the type or name of a field later.

You and I are in rabid agreement on that point. I don't like code generation tools that spew forth blocks of code that I then have to maintain. To me, the existence of such tools indicates a deficiency in the language. (If it's easy enough for a tool to generate boilerplate code like that, it should be easy for the language to make that boilerplate code unnecessary by generating it for me as I compile.)

>That's why I want a 'data' modifier for class, which will completely  
>auto-generate everything. If the 'saves me typing' argument holds  
>water, imagine what this will do for you!

We agree on this. I want a data modifier for a class also (or could we just use the 'struct' keyword like C++?). However, the auto-assignment parameters proposal has more general applicability to classes other than data classes as well, so I want those too. I might even use them both together in the same class.

> I also don't want such a  
>feature to spin out of a control into an entirely new programming  
>definition syntax, so we'll just use java itself to fill in the gaps  
>and afford us flexibility: If the auto-gen isn't good enough for you,  
>then don't use it and write it the usual way. You get method-level  
>granularity for this process, but that's where it ends. Simple and yet  
>a great boon for code maintainability.

I agree with this as well. I think it's perfectly reasonable for there to be shorthand syntax for common cases, with the ability to override it when something more complex is needed. If I just want to return three values from a method, I don't want to have to write a full-blown class complete with a constructor, getters, and setters. Just specifying the fields is enough. A data class will probably do fine. But I want to be able to replace that data class later with the real thing if necessary without having to update all of the uses of it in the code.

Derek

>
>
>
>  --Reinier Zwitserloot
>
>
>
>On Mar 28, 2009, at 22:31, Derek Foster wrote:
>
>> Just to add a few kudos and comments:
>>
>> I like the proposal a lot. Even in its current form, this would save  
>> me a lot of typing. Of the proposals so far put forth on Project  
>> Coin, this is the one I would probably end up using the most often.  
>> I use a lot of immutable class objects, and this
>>
>> Some suggestions and things to consider:
>>
>> 1) I think that having to repeat "this." all over the place is  
>> perhaps unnecessary. You could use something shorter, like a leading  
>> dot, or perhaps a leading equals sign:
>>
>> class Foo {
>>   final int bar;
>>   final String baz;
>>   Foo(int .bar, String .baz) {}
>>   void setBar(int .bar) {}
>>   void setBaz(String .baz) {}
>> }
>>
>> 2) I think that allowing the syntax for all method parameters, not  
>> just constructor parameters, would be nice.
>>
>> 3) I think that allowing the syntax for return values from methods  
>> has some potential advantages as well. There are some potential  
>> advantages with
>> Javadoc generation, as I describe below, which would make:
>>
>>    String this.foo getFoo() {}
>>
>> advantageous in some circumstances even if it isn't much shorter than:
>>
>>    String getFoo() { return this.foo; }
>>
>> 4) I think you should consider the impact on Javadoc more carefully.  
>> Particularly in cases where people use a prefix ("_", "m_", etc.) on  
>> their internal fields, which is very common. It looks as though  
>> those prefixes would end up being displayed in Javadoc as  
>> constructor parameter names, which would be less than ideal.
>>
>> Also, autogeneration of Javadoc for the this. parameters, based on  
>> Javadoc for the class members they are initialized from would be  
>> nice. Currently, these often have to be maintained in parallel,  
>> which can be a significant annoyance.
>>
>> I often see people write code equivalent to:
>>
>> class Foo {
>>    /** This is the name of a famous person which can't be null and  
>> blah blah blah. */
>>    String _bar;
>>
>>    /**
>>     * Construct a new instance.
>>     * @param bar This is the name of a famous person which can't be  
>> null and blah blah blah.
>>     */
>>    Foo(String bar) {
>>        _bar = bar;
>>    }
>>
>>    /**
>>     * Sets the value of bar.
>>     * @param bar This is the name of a famous person which can't be  
>> null and blah blah blah.
>>     */
>>    void setBar(String bar) {
>>        _bar = bar;
>>    }
>>
>>    /**
>>     * Gets the value of bar.
>>     * @return This is the name of a famous person which can't be  
>> null and blah blah blah.
>>     */
>>    String getBar() {
>>        return _bar;
>>    }
>>
>> }
>>
>> which essentially reproduces the same JavaDoc comment four times  
>> (and means it must be maintained in quadruplicate if changes are  
>> made). It would be nice to replace this with something like:
>>
>> class Foo {
>>    /** This is the name of a famous person which can't be null and  
>> blah blah blah. */
>>    String _bar;
>>
>>    /** Construct a new instance. */
>>    Foo(String this.bar) {}
>>
>>    /** Sets the value of bar. */
>>    void setBar(String this.bar) {}
>>
>>    /** Gets the value of bar. */
>>    String this.bar getBar() {}
>> }
>>
>> with the same Javadoc being generated as the prior example.
>>
>> 5) Being able to omit the type in all of these cases would be a big  
>> plus. When I have a variable of a type like  
>> "List<Map<ReallyLongTypeName,OtherReallyLongTypeName>>", it would be  
>> awfully nice to be able to omit having to specify that detail  
>> redundantly in the constructor, settter, and getter.
>>
>> Derek
>>
>>
>>
>>
>> -----Original Message-----
>>> From: Mark Mahieu <markmahieu at googlemail.com>
>>> Sent: Mar 26, 2009 2:21 PM
>>> To: Marek Kozie? <develop4lasu at gmail.com>
>>> Cc: coin-dev <coin-dev at openjdk.java.net>
>>> Subject: Re: PROPOSAL: Auto-assignment Parameters
>>>
>>> 2009/3/26 Marek Kozie? <develop4lasu at gmail.com>
>>>
>>>> I see one problem here.
>>>> class Some{
>>>>  final String name;
>>>>  public Some(String this.name){}
>>>> }
>>>>
>>>> perform .intern() is impossible now.
>>>
>>>
>>> Correct, you'd have to write it the same way as you'd do now.  I  
>>> actually
>>> view that as a Good Thing though: there's a clear, visual distinction
>>> between parameters which are just assigned directly to the fields,  
>>> and those
>>> on which we perform some operation first.  Only the latter would  
>>> appear in
>>> the body of the constructor, without being cluttered by the former.
>>>
>>>
>>>> But I like the proposition 'much'.
>>>> Simple and clear.
>>>
>>>
>>> Glad you like it!
>>>
>>>
>>> Regards,
>>>
>>> Mark
>>>
>>
>>
>



From vapor1 at teleport.com  Fri Apr  3 01:09:56 2009
From: vapor1 at teleport.com (Derek Foster)
Date: Fri, 3 Apr 2009 04:09:56 -0400 (EDT)
Subject: PROPOSAL: @OverrideAll annotation
Message-ID: <17542308.1238746196681.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>

My major problem with this proposal is that it doesn't seem to be straightforward to generate the bodies of methods that have to return something. Particularly for code such as implementations of the Visitor pattern.

Having un-overridden methods simply return null or zero is often not the right thing to do.

It's OK for generating methods that just take parameters, I suppose.

Still, having annotations generate code or otherwise affect the operation of a program is apparently a no-no per Sun's rules. If something like this is going to happen, I think it needs a new keyword or something rather than using an annotation.

(Although, personally, I don't think it would be such a bad thing if code generation via annotation existed, but were limited only to certain annotations in a specific package duly designated by the language implementors. Annotations have one nice quality that other ways of extending the language don't: You can create new "keywords" at will with no risk of breaking someone's perfectly-working code. If they don't import the annotation, they won't need to be impacted by it. I sort of wish there was an alternative to annotations (@@Foo instead of @Foo?) which was explicitly for the purpose of telling the compiler to generate boilerplate code of various types. Decorators in Python sort of serve this purpose, for instance.)

Derek

-----Original Message-----
>From: rssh at gradsoft.com.ua
>Sent: Mar 31, 2009 10:02 AM
>To: Gabriel Belingueres <belingueres at gmail.com>
>Cc: coin-dev <coin-dev at openjdk.java.net>
>Subject: Re: PROPOSAL: @OverrideAll annotation
>
>> Hi,
>>
>> I've written a new feature that might be comfortable to use for
>> someone. All input is welcomed.
>>
>
>It-is possible to do near same with annotation API (create a superclass
> which will override all)
>
>But -- sometime we really need to say, that all methods 'mus be'
>overriden.  (For example - when implementing Proxy pattern).
>In such case class-level annotation '@OverrideAll'  which tell compiler
>to check, that all methods must be overriden -- brilliant idea.
>
>
>
>
>
>> Regards,
>> Gabriel
>>
>> PROJECT COIN SMALL LANGUAGE CHANGE PROPOSAL FORM v1.0
>>
>> AUTHOR(S): Gabriel Belingueres
>>
>> OVERVIEW
>>
>> Add an @OverrideAll annotation to allow a class to override all
>> inherited methods with a trivial implementation. The resulting class
>> then could be used as the basis for a Null Object pattern (or even a
>> basic Mock object.)
>>
>>
>> FEATURE SUMMARY:
>>
>> The proposed @OverrideAll annotation will allow the class to override
>> all methods (from its superclasses and implemented interfaces) with a
>> trivial body, but the defined class can choose to implement specific
>> methods, replacing those that would be produced automatically by the
>> annotation.
>>
>>
>> MAJOR ADVANTAGE:
>>
>> Less coding for implementing Null Objects, or simple tests.
>>
>>
>> MAJOR BENEFIT:
>>
>> Let the compiler implement all uninteresting, non relevant behavior by
>> automatically providing with a trivial implementation of the inherited
>> methods.
>>
>>
>> MAJOR DISADVANTAGE:
>>
>> Might be a cause of NullPointerException if not used judiciously.
>>
>>
>> ALTERNATIVES:
>>
>> Implement all uninteresting methods by yourself by providing yourself
>> a trivial implementation (though actually popular IDEs can do this
>> automatically for you already.)
>>
>> EXAMPLES
>>
>> Given:
>>
>> class B {}
>>
>> public class A implements I1, I2 {
>>
>>   public static final int VAR = 1;
>>
>>   private B b;
>>
>>   public static Integer getSome() {
>>     return VAR;
>>   }
>>
>>   public A() {
>>   }
>>
>>   public A(B b) {
>>     this.b=b;
>>   }
>>
>>   public B getB() {
>>     return b;
>>   }
>>
>>   public void setB(B b) {
>>     this.b=b;
>>   }
>>
>>   protected void doProtected() { ... }
>>
>>   private void doPrivate() { ... }
>>
>>   A someNewA() { ... }
>>
>>   public synchronized void someSynchronized() {
>>   }
>>
>> }
>>
>> then:
>>
>> @OverrideAll
>> public class NullA extends A {
>> }
>>
>> is equivalent to declare:
>>
>> public class NullA extends A {
>>
>>   public NullA() {}
>>
>>   public NullA(B b) {
>>     super(b);
>>   }
>>
>>   public B getB() {
>>     return null;
>>   }
>>
>>   public void setB(B b) {
>>   }
>>
>>   protected void doProtected() {
>>    // empty
>>   }
>>
>>   A someNewA() {
>>    return null;
>>   }
>>
>>   public synchronized void someSynchronized() {
>>     // empty
>>   }
>>
>> }
>>
>> You may not want the default trivial implementation in some methods,
>> then you override them as usual:
>>
>> @OverrideAll
>> public class NullA extends A {
>>
>>   @Override
>>   public B getB() {
>>     return new B();
>>   }
>>
>>   @Override
>>   public synchronized void someSynchronized() {
>>     System.out.println("overridden");
>>   }
>>
>> }
>>
>> EXAMPLE 2
>>
>> Implement a trivial Collection interface just to test that adding
>> elements will increase the collection size:
>>
>> Currently:
>>
>> public class SomeCollection<E> implements Collection<E> {
>>
>>   private int counter;
>>
>>   @Override
>>   public boolean add(E arg0) {
>>     counter++;
>>     return true;
>>   }
>>
>>   @Override
>>   public boolean addAll(Collection<? extends E> c) {
>>     counter += c.size();
>>     return true;
>>   }
>>
>>   @Override
>>   public void clear() {
>>   }
>>
>>   @Override
>>   public boolean contains(Object arg0) {
>>     return false;
>>   }
>>
>>   @Override
>>   public boolean containsAll(Collection<?> arg0) {
>>     return false;
>>   }
>>
>>   @Override
>>   public boolean isEmpty() {
>>     return false;
>>   }
>>
>>   @Override
>>   public Iterator<E> iterator() {
>>     return null;
>>   }
>>
>>   @Override
>>   public boolean remove(Object arg0) {
>>     return false;
>>   }
>>
>>   @Override
>>   public boolean removeAll(Collection<?> arg0) {
>>     return false;
>>   }
>>
>>   @Override
>>   public boolean retainAll(Collection<?> arg0) {
>>     return false;
>>   }
>>
>>   @Override
>>   public int size() {
>>     return counter;
>>   }
>>
>>   @Override
>>   public Object[] toArray() {
>>     return null;
>>   }
>>
>>   @Override
>>   public <T> T[] toArray(T[] arg0) {
>>     return null;
>>   }
>>
>> }
>>
>> With the annotation:
>>
>> @OverrideAll
>> public class SomeCollection<E> implements Collection<E> {
>>
>>   private int counter;
>>
>>   @Override
>>   public boolean add(E arg0) {
>>     counter++;
>>     return true;
>>   }
>>
>>   @Override
>>   public boolean addAll(Collection<? extends E> c) {
>>     counter += c.size();
>>     return true;
>>   }
>>
>>
>>   @Override
>>   public int size() {
>>     return counter;
>>   }
>>
>> }
>>
>>
>> DETAILS
>>
>>
>> SPECIFICATION:
>>
>> A preliminary specification follows:
>>
>> As this feature is proposed as an annotation for code generation, no
>> changes to the current JLSv3 are needed.
>>
>> The annotation will generate "trivial" overridden implementations for
>> all methods not specified in the class, for each superclass in the
>> hierarchy (except Object) and implemented interface.
>>
>> - Static methods, private methods, final methods, constructors and
>> methods from class Object should never be generated.
>> - If some superclass (except Object) has already overridden some
>> Object class methods, then do NOT generate an empty overridden method
>> (to reuse current behavior.) (for example, if some superclass already
>> override toString(), equals() or hashCode().)
>>
>> - OPTIONAL: add a parameter to the @OverrideAll annotation to indicate
>> if @Deprecated methods should not be implemented.
>>
>> Trivial implementation for generated methods:
>>
>> - Methods returning void will have an empty body. (OPTIONAL: add a
>> parameter to the @OverrideAll annotation to indicate that it should
>> throw UnsupportedOperationException instead)
>> - Methods returning a primitive type will have a body returning the
>> same default value that would have for uninitialized instance
>> variables. (JLS section 4.12.5.)
>> - Methods returning a reference type will "return null;". (JLS section
>> 4.12.5.)
>> - The method will never return a covariant return type (because in
>> case of implementing a Null object, it should be undistinguished from
>> the common case)
>> - Methods that throws checked exceptions can be modified to delete the
>> throws clause. (ie. the trivial implementation should not throw
>> checked exceptions)
>> - Synchronized methods should retain that attribute.
>>
>>
>> COMPILATION:
>>
>> Compilation should proceed as usual, except that the annotation
>> processor would generate the code when it encounters an annotated
>> class.
>>
>> No changes to the class file format are needed.
>>
>>
>> TESTING
>>
>> Test cases should be done, including testing with classes implementing
>> several interfaces, classes with generics, inner classes, etc.
>>
>>
>> LIBRARY SUPPORT:
>>
>> No, except creating the new annotation.
>>
>>
>> REFLECTIVE APIS:
>>
>> No changes foreseen.
>>
>>
>> OTHER CHANGES:
>>
>> Output of javadoc tool.
>>
>>
>> MIGRATION:
>>
>> Just add the annotation to class level, and erase your trivially
>> implemented overridden methods.
>>
>>
>> COMPATIBILITY
>>
>> BREAKING CHANGES:
>> All existing programs remain valid.
>>
>> EXISTING PROGRAMS:
>> The semantics of existing class files and legal source files are
>> unchanged by this feature.
>>
>>
>> REFERENCES
>>
>> EXISTING BUGS:
>>
>> None that I know about.
>>
>> URL FOR PROTOTYPE:
>>
>> None at this time.
>>
>>
>
>
>



From vapor1 at teleport.com  Fri Apr  3 01:15:25 2009
From: vapor1 at teleport.com (Derek Foster)
Date: Fri, 3 Apr 2009 04:15:25 -0400 (EDT)
Subject: Proposal: Accepting a subclass as an element type in a for loop
Message-ID: <9909880.1238746526010.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>

I was leaning somewhat on the side of thinking this would be a nice feature (it is, at least, an elegant one), but I think that Reiner's arguments have convinced me otherwise.

The example of the filtering method, in particular, shows that working around this is quite easy. Given that the need for this actually comes up pretty rarely in my experience (I have only ever wanted this once, that I can recall, and it was both easy and intuitive to work around in a manner somewhat similar to but less general than Reiner's suggestion), I think I have come to the conclusion that despite its elegance, this probably isn't worth adding to the language.

Derek



-----Original Message-----
>From: Reinier Zwitserloot <reinier at zwitserloot.com>
>Sent: Mar 31, 2009 11:16 AM
>To: Jean-Louis Ardoint <jlardoint at ilog.fr>
>Cc: coin-dev at openjdk.java.net
>Subject: Re: Proposal: Accepting a subclass as an element type in a for loop
>
>Why is this worthy of a language change? It's very niche.
>
>You can solve your problem by writing 1 method, like so:
>
>for ( Rectangle r : MyUtilityClass.filterOnType(shapes,  
>Rectangle.class) ) {
>    drawRectangle(r);
>}
>
>
>with:
>
>public class MyUtilityClass {
>     public static <A, B> List<B> filterOnType(Iterable<? extends A>  
>in, Class<B> outType) {
>         List<B> list = new ArrayList<B>();
>         for ( A a : in )
>             if ( outType.isInstance(a) ) list.add(outType.cast(a));
>         return list;
>}
>
>
>
>Even if you disregard for a moment that if you add this, I've got  
>about a gazillion other niche things that have about as many use cases  
>and are about as easy to solve with a library for coin,your proposal  
>has omitted a rather serious issue:
>
>What would you do if you have something like:
>
>List<Set<Number>> foo = someMethodCall();
>for ( Set<Double> set : foo ) {
>    // You can't do this in java.
>}
>
>
>
>  --Reinier Zwitserloot
>
>
>
>On Mar 31, 2009, at 14:55, Jean-Louis Ardoint wrote:
>
>> I'm maybe a bit too late. Here's my proposal anyway.
>>
>>
>>
>> -- Jean-Louis Ardoint
>>
>>
>>
>> Accepting a subclass as an element type in a for loop
>>
>>
>>
>> AUTHOR(S): Jean-Louis Ardoint
>>
>>
>>
>> OVERVIEW
>>
>>
>>
>> FEATURE SUMMARY
>>
>>
>>
>> Add a filtering and downcast capability to the enhanced for statement
>> (a.k.a for each).
>>
>>
>>
>> MAJOR ADVANTAGE
>>
>>
>>
>> It should reduce the number of lines of code and depth of nesting in
>> loops. The resulting code would be more readable that what is done
>> currently to achieve the same goal. The meaning of such a loop is  
>> quite
>> obvious.
>>
>>
>>
>> MAJOR BENEFIT
>>
>>
>>
>> Better readability and expressiveness.
>>
>>
>>
>> MAJOR DISADVANTAGE
>>
>>
>>
>> More complexity in the compiler to generate a little bit more  
>> bytecode.
>>
>>
>>
>> ALTERNATIVE
>>
>>
>>
>> You can currently the same thing, yet it means adding an extra if
>> statement and an intermediate variable to be cast.
>>
>>
>>
>> EXAMPLES
>>
>>
>>
>> Here is a small not very interesting example of such a enhanced for
>> loop:
>>
>>
>>
>> Shape[] shapes = ...;
>>
>> for (Shape s : shapes)
>>
>>      drawShape(s);
>>
>>
>>
>> If for a reason you would need to draw only the rectangles, you would
>> need to write:
>>
>>
>>
>> for (Shape s : shapes) {
>>
>>  if (s instanceof Rectangle)
>>
>>    drawRectangle((Rectangle)s);
>>
>> }
>>
>>
>>
>> This is not very aesthetic. If only the for loop would directly  
>> accept a
>> subclass as the element type and do the type checking and downcast, we
>> could be able to write:
>>
>>
>>
>> for (Rectangle r : shapes)
>>
>>  drawRectangle(r);
>>
>>
>>
>> Note that there is a subtlety w.r.t. the handling of nulls. See
>> Compilation below for more details
>>
>>
>>
>> DETAILS
>>
>>
>>
>> SPECIFICATION:
>>
>>
>>
>> The grammar is unchanged. The equivalence between an enhanced for loop
>> and a regular for loop has to be changed in JLS 14.14.2.
>>
>> COMPILATION:
>>
>>
>>
>> The way enhanced loop are translated into bytecode would change
>> depending on whether the loop variable type is a subclass of the
>> iterable or array element type.
>>
>> If the loop variable type is a subclass, then the loop is equivalent  
>> to:
>>
>>
>>
>> For an expression returning Iterable<C>:
>>
>> Iterable<C> cs...
>>
>> for (I #i = cs.iterator(); #i.hasNext(); ) {
>>
>>  C #c = #i.next();
>>
>>  if (#c == null || #c instanceof D) {
>>
>>    D d = (C)#c;
>>
>>    ...
>>
>>  }
>>
>> }
>>
>>
>>
>> For an array:
>>
>>
>>
>> C[] ca...
>>
>> for (int i = 0; i < ca.length; i++) {
>>
>>  C #c = ca[i];
>>
>>  if (#c == null || #c instanceof D) {
>>
>>    D d = (C)#c;
>>
>>    ...
>>
>>  }
>>
>> }
>>
>>
>>
>> Note that we need to test against null to keep the same behavior as  
>> the
>> regular enhanced for loop.
>>
>>
>>
>> TESTING:
>>
>>
>>
>> This feature can be tested in the same way the enhanced for loop is
>> tested.
>>
>>
>>
>>
>>
>> LIBRARY SUPPORT:
>>
>>
>>
>> There is no need for library support.
>>
>>
>>
>>
>>
>> REFLECTIVE APIS:
>>
>>
>>
>> No updates to the reflection APIs are needed.
>>
>>
>>
>>
>>
>> OTHER CHANGES:
>>
>>
>>
>> No other changes are needed.
>>
>>
>>
>>
>>
>> MIGRATION:
>>
>>
>>
>> Migration of existing enhanced for loop can be done if one desires so.
>>
>>
>>
>> COMPATIBILITY
>>
>>
>>
>>
>>
>> BREAKING CHANGES:
>>
>>
>>
>> This feature would not break any existing programs, since the new
>> feature only permits more code to be parsed than before.
>>
>>
>>
>>
>>
>> EXISTING PROGRAMS:
>>
>>
>>
>> Class file format does not change, so existing programs can use class
>> files compiled with the new feature without problems.
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
>



From rssh at gradsoft.com.ua  Fri Apr  3 01:19:42 2009
From: rssh at gradsoft.com.ua (rssh at gradsoft.com.ua)
Date: Fri, 3 Apr 2009 11:19:42 +0300 (EEST)
Subject: PROPOSAL: @OverrideAll annotation
In-Reply-To: <17542308.1238746196681.JavaMail.root@mswamui-thinleaf.atl.sa.earthlin
	k.net>
References: <17542308.1238746196681.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>
Message-ID: <ed1e4dbc1c2feaaab94a401188fec6aa.squirrel@wmail.gradsoft.ua>

> My major problem with this proposal is that it doesn't seem to be
> straightforward to generate the bodies of methods that have to return
> something. Particularly for code such as implementations of the Visitor
> pattern.
>
> Having un-overridden methods simply return null or zero is often not the
> right thing to do.
>
> It's OK for generating methods that just take parameters, I suppose.
>

May be this is not, what author of original proposal mean, but have
class annotation @OverrideAll, which does not generate any code, just
throw compile-time error when exists non-overridden member functions
is helpfull in some situations and prevent from hard to debug errors.



> Still, having annotations generate code or otherwise affect the operation
> of a program is apparently a no-no per Sun's rules. If something like this
> is going to happen, I think it needs a new keyword or something rather
> than using an annotation.
>
> (Although, personally, I don't think it would be such a bad thing if code
> generation via annotation existed, but were limited only to certain
> annotations in a specific package duly designated by the language
> implementors. Annotations have one nice quality that other ways of
> extending the language don't: You can create new "keywords" at will with
> no risk of breaking someone's perfectly-working code. If they don't import
> the annotation, they won't need to be impacted by it. I sort of wish there
> was an alternative to annotations (@@Foo instead of @Foo?) which was
> explicitly for the purpose of telling the compiler to generate boilerplate
> code of various types. Decorators in Python sort of serve this purpose,
> for instance.)
>
> Derek
>
> -----Original Message-----
>>From: rssh at gradsoft.com.ua
>>Sent: Mar 31, 2009 10:02 AM
>>To: Gabriel Belingueres <belingueres at gmail.com>
>>Cc: coin-dev <coin-dev at openjdk.java.net>
>>Subject: Re: PROPOSAL: @OverrideAll annotation
>>
>>> Hi,
>>>
>>> I've written a new feature that might be comfortable to use for
>>> someone. All input is welcomed.
>>>
>>
>>It-is possible to do near same with annotation API (create a superclass
>> which will override all)
>>
>>But -- sometime we really need to say, that all methods 'mus be'
>>overriden.  (For example - when implementing Proxy pattern).
>>In such case class-level annotation '@OverrideAll'  which tell compiler
>>to check, that all methods must be overriden -- brilliant idea.
>>
>>
>>
>>
>>
>>> Regards,
>>> Gabriel
>>>
>>> PROJECT COIN SMALL LANGUAGE CHANGE PROPOSAL FORM v1.0
>>>
>>> AUTHOR(S): Gabriel Belingueres
>>>
>>> OVERVIEW
>>>
>>> Add an @OverrideAll annotation to allow a class to override all
>>> inherited methods with a trivial implementation. The resulting class
>>> then could be used as the basis for a Null Object pattern (or even a
>>> basic Mock object.)
>>>
>>>
>>> FEATURE SUMMARY:
>>>
>>> The proposed @OverrideAll annotation will allow the class to override
>>> all methods (from its superclasses and implemented interfaces) with a
>>> trivial body, but the defined class can choose to implement specific
>>> methods, replacing those that would be produced automatically by the
>>> annotation.
>>>
>>>
>>> MAJOR ADVANTAGE:
>>>
>>> Less coding for implementing Null Objects, or simple tests.
>>>
>>>
>>> MAJOR BENEFIT:
>>>
>>> Let the compiler implement all uninteresting, non relevant behavior by
>>> automatically providing with a trivial implementation of the inherited
>>> methods.
>>>
>>>
>>> MAJOR DISADVANTAGE:
>>>
>>> Might be a cause of NullPointerException if not used judiciously.
>>>
>>>
>>> ALTERNATIVES:
>>>
>>> Implement all uninteresting methods by yourself by providing yourself
>>> a trivial implementation (though actually popular IDEs can do this
>>> automatically for you already.)
>>>
>>> EXAMPLES
>>>
>>> Given:
>>>
>>> class B {}
>>>
>>> public class A implements I1, I2 {
>>>
>>>   public static final int VAR = 1;
>>>
>>>   private B b;
>>>
>>>   public static Integer getSome() {
>>>     return VAR;
>>>   }
>>>
>>>   public A() {
>>>   }
>>>
>>>   public A(B b) {
>>>     this.b=b;
>>>   }
>>>
>>>   public B getB() {
>>>     return b;
>>>   }
>>>
>>>   public void setB(B b) {
>>>     this.b=b;
>>>   }
>>>
>>>   protected void doProtected() { ... }
>>>
>>>   private void doPrivate() { ... }
>>>
>>>   A someNewA() { ... }
>>>
>>>   public synchronized void someSynchronized() {
>>>   }
>>>
>>> }
>>>
>>> then:
>>>
>>> @OverrideAll
>>> public class NullA extends A {
>>> }
>>>
>>> is equivalent to declare:
>>>
>>> public class NullA extends A {
>>>
>>>   public NullA() {}
>>>
>>>   public NullA(B b) {
>>>     super(b);
>>>   }
>>>
>>>   public B getB() {
>>>     return null;
>>>   }
>>>
>>>   public void setB(B b) {
>>>   }
>>>
>>>   protected void doProtected() {
>>>    // empty
>>>   }
>>>
>>>   A someNewA() {
>>>    return null;
>>>   }
>>>
>>>   public synchronized void someSynchronized() {
>>>     // empty
>>>   }
>>>
>>> }
>>>
>>> You may not want the default trivial implementation in some methods,
>>> then you override them as usual:
>>>
>>> @OverrideAll
>>> public class NullA extends A {
>>>
>>>   @Override
>>>   public B getB() {
>>>     return new B();
>>>   }
>>>
>>>   @Override
>>>   public synchronized void someSynchronized() {
>>>     System.out.println("overridden");
>>>   }
>>>
>>> }
>>>
>>> EXAMPLE 2
>>>
>>> Implement a trivial Collection interface just to test that adding
>>> elements will increase the collection size:
>>>
>>> Currently:
>>>
>>> public class SomeCollection<E> implements Collection<E> {
>>>
>>>   private int counter;
>>>
>>>   @Override
>>>   public boolean add(E arg0) {
>>>     counter++;
>>>     return true;
>>>   }
>>>
>>>   @Override
>>>   public boolean addAll(Collection<? extends E> c) {
>>>     counter += c.size();
>>>     return true;
>>>   }
>>>
>>>   @Override
>>>   public void clear() {
>>>   }
>>>
>>>   @Override
>>>   public boolean contains(Object arg0) {
>>>     return false;
>>>   }
>>>
>>>   @Override
>>>   public boolean containsAll(Collection<?> arg0) {
>>>     return false;
>>>   }
>>>
>>>   @Override
>>>   public boolean isEmpty() {
>>>     return false;
>>>   }
>>>
>>>   @Override
>>>   public Iterator<E> iterator() {
>>>     return null;
>>>   }
>>>
>>>   @Override
>>>   public boolean remove(Object arg0) {
>>>     return false;
>>>   }
>>>
>>>   @Override
>>>   public boolean removeAll(Collection<?> arg0) {
>>>     return false;
>>>   }
>>>
>>>   @Override
>>>   public boolean retainAll(Collection<?> arg0) {
>>>     return false;
>>>   }
>>>
>>>   @Override
>>>   public int size() {
>>>     return counter;
>>>   }
>>>
>>>   @Override
>>>   public Object[] toArray() {
>>>     return null;
>>>   }
>>>
>>>   @Override
>>>   public <T> T[] toArray(T[] arg0) {
>>>     return null;
>>>   }
>>>
>>> }
>>>
>>> With the annotation:
>>>
>>> @OverrideAll
>>> public class SomeCollection<E> implements Collection<E> {
>>>
>>>   private int counter;
>>>
>>>   @Override
>>>   public boolean add(E arg0) {
>>>     counter++;
>>>     return true;
>>>   }
>>>
>>>   @Override
>>>   public boolean addAll(Collection<? extends E> c) {
>>>     counter += c.size();
>>>     return true;
>>>   }
>>>
>>>
>>>   @Override
>>>   public int size() {
>>>     return counter;
>>>   }
>>>
>>> }
>>>
>>>
>>> DETAILS
>>>
>>>
>>> SPECIFICATION:
>>>
>>> A preliminary specification follows:
>>>
>>> As this feature is proposed as an annotation for code generation, no
>>> changes to the current JLSv3 are needed.
>>>
>>> The annotation will generate "trivial" overridden implementations for
>>> all methods not specified in the class, for each superclass in the
>>> hierarchy (except Object) and implemented interface.
>>>
>>> - Static methods, private methods, final methods, constructors and
>>> methods from class Object should never be generated.
>>> - If some superclass (except Object) has already overridden some
>>> Object class methods, then do NOT generate an empty overridden method
>>> (to reuse current behavior.) (for example, if some superclass already
>>> override toString(), equals() or hashCode().)
>>>
>>> - OPTIONAL: add a parameter to the @OverrideAll annotation to indicate
>>> if @Deprecated methods should not be implemented.
>>>
>>> Trivial implementation for generated methods:
>>>
>>> - Methods returning void will have an empty body. (OPTIONAL: add a
>>> parameter to the @OverrideAll annotation to indicate that it should
>>> throw UnsupportedOperationException instead)
>>> - Methods returning a primitive type will have a body returning the
>>> same default value that would have for uninitialized instance
>>> variables. (JLS section 4.12.5.)
>>> - Methods returning a reference type will "return null;". (JLS section
>>> 4.12.5.)
>>> - The method will never return a covariant return type (because in
>>> case of implementing a Null object, it should be undistinguished from
>>> the common case)
>>> - Methods that throws checked exceptions can be modified to delete the
>>> throws clause. (ie. the trivial implementation should not throw
>>> checked exceptions)
>>> - Synchronized methods should retain that attribute.
>>>
>>>
>>> COMPILATION:
>>>
>>> Compilation should proceed as usual, except that the annotation
>>> processor would generate the code when it encounters an annotated
>>> class.
>>>
>>> No changes to the class file format are needed.
>>>
>>>
>>> TESTING
>>>
>>> Test cases should be done, including testing with classes implementing
>>> several interfaces, classes with generics, inner classes, etc.
>>>
>>>
>>> LIBRARY SUPPORT:
>>>
>>> No, except creating the new annotation.
>>>
>>>
>>> REFLECTIVE APIS:
>>>
>>> No changes foreseen.
>>>
>>>
>>> OTHER CHANGES:
>>>
>>> Output of javadoc tool.
>>>
>>>
>>> MIGRATION:
>>>
>>> Just add the annotation to class level, and erase your trivially
>>> implemented overridden methods.
>>>
>>>
>>> COMPATIBILITY
>>>
>>> BREAKING CHANGES:
>>> All existing programs remain valid.
>>>
>>> EXISTING PROGRAMS:
>>> The semantics of existing class files and legal source files are
>>> unchanged by this feature.
>>>
>>>
>>> REFERENCES
>>>
>>> EXISTING BUGS:
>>>
>>> None that I know about.
>>>
>>> URL FOR PROTOTYPE:
>>>
>>> None at this time.
>>>
>>>
>>
>>
>>
>
>




From Joe.Darcy at Sun.COM  Fri Apr  3 01:25:07 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Fri, 03 Apr 2009 01:25:07 -0700
Subject: PROPOSAL: language support for JSR 292
In-Reply-To: <6F835C91-A2F2-4050-BD03-DB1B462C2B4F@sun.com>
References: <80FFB064-577D-4CEA-A93A-73C424AAE21B@sun.com>
	<6F835C91-A2F2-4050-BD03-DB1B462C2B4F@sun.com>
Message-ID: <49D5C7E3.50801@sun.com>

Hello.

Some comments interspersed.

John Rose wrote:
> Here is a text form of the proposal, for the archives.  The wiki form  
> should be equivalent at the moment, but as edits are made the wiki  
> form will be normative.
>
> Best wishes,
> -- John
>
> AUTHOR(S):
>
> John Rose
>
> OVERVIEW
>
> Create source-code syntaxes for using new JVM features from JSR 292.   
> These are invokedynamic instructions, method handle invocation,  
> certain relaxed conversions, and exotic identifiers.

[snip]

> 1.3 Any call to a method in Dynamic accepts an optional type parameter  
> which specifies the return type of the call site's descriptor.  The  
> type parameter may any type whatever, including void or a primitive  
> type.  If it is omitted it defaults to the type java.dyn.Dynamic  
> itself.  (See part 4 for conversion rules involving Dynamic.)
>   

Reiterating a point Neal raised, if Dynamic is not related to Object, 
what does that mean when Dynamic is used as the format type argument to 
a type parameter?  What do "? extends Dynamic" and "? super Dynamic" 
mean to the type system?

>      Dynamic x = Dynamic.myGetCurrentThing();  // type () -> Dynamic
>      Dynamic.<void>myPutCurrentThing(x);  // type (Dynamic) -> void
>      int y = Dynamic.<int>myHashCode((Object)x);  // type (Object) ->  
> int
>      boolean z = Dynamic.<boolean>myEquals(x, y);  // type (Dynamic,  
> int) -> boolean
>
> (Rationale: Although it is strange for non-references to appear in the  
> syntactic position of type arguments, this design is far simpler than  
> inventing a completely new syntax for specifying the return type of  
> the call site, as some early prototypes did.)
>
> 1.4 For the purposes of determining the descriptor of the  
> invokedynamic instruction, null arguments (unless casted to some other  
> type) are deemed to be of reference type java.lang.Void.  This is a  
> pragmatic choice, compatible with the verifier and partially coherent  
> with the meaning of the type Void, since it happens to allow only null  
> reference values.  Conversely, void method return values are reflected  
> as null values.  The type Void will appear only to the bootstrap  
> method, and will serve notice that the call site contains a null,  
> rather than an explicitly typed reference.
>
>      Dynamic.myPrintLine(null);  // type (Void) -> Dynamic
>      Dynamic.<void>foo((String)null, null);  // type (String, Void) ->  
> void
>
> 1.5 No checked exceptions are produced by any call to Dynamic.
>
>      try { Dynamic.foo(); } catch (Exception ee) { }  // a compile- 
> time error
>   

Actually there is a special rule that catching Exception is always okay 
per JLS 11.2.3; this program is legal and compiles fine:

public class Test {
    public static void main(String... args){
    try {
        ;
    } catch (Exception e) {
        ;
    }
    }
}

[snip]

> 2.2 Any reference of type MethodHandle may be qualified with the  
> method name "invoke" and invoked on any number and type of arguments.   
> Only the method named "invoke" is treated this new way.  All other  
> expressions involving MethodHandle are unchanged in meaning, including  
> selection of members other than "invoke", casting, and instanceof.
>
>      MethodHandle mh = ...;
>      mh.invoke("foo", 42);  // argument types (String, int)
>      MethodType mtype = mh.type();  // no new rules here; see JSR 292  
> javadocs
>      mh.neverBeforeSeenName();  // no new rules; must raise an error
>
> In effect, java.dyn.MethodHandle appears to have an infinite number of  
> non-static methods named "invoke", of every possible signature.
>
> (In fact, JSR 292 specifies that each individual method handle has a  
> unique type signature, and may be invoked only under that specific  
> type.  This type is checked on every method handle call.  JSR 292  
> guarantees runtime type safety by requiring that an exception be  
> thrown if a method handle caller and callee do not agree exactly on  
> the argument and return types.  The details of this check are not part  
> of this specification, but rather of the MethodHandle API.)
>   

So what are the notions of identity and equality for method handles?

[snip]
> 4.1 As specified above, the interface java.dyn.Dynamic has no  
> supertypes or members.  As such, it is a bare reference type.  (As an  
> arbitrary relation, the superclass of Dynamic[] is Object[].)  We  
>   

Are there any other type building operations besides arrays we need to 
worry about?

[snip]

> 4.6 The expression syntaxes with predefined meaning for dynamic sub- 
> expressions are those which perform the conversions described above.   
> These are assignment "=" and casts.  Dynamic expressions may also be  
> tested with instanceof.  Also, Dynamic values may be declared,  
> assigned to variables, passed as method or constructor arguments, and  
> returned from methods.
>
> But, the Java operators "==" "!=" "+" "+=" on reference types are  
> clarified to apply only to reference types which are java.lang.Object  
> or one of its subtypes; they do not have a predefined meaning if  
> either operand is dynamic.  The "synchronized" and "throw" statements  
> cannot be applied to dynamic expressions.
>   

So if there is no predefined meaning, are those operations illegal?

[snip]

> REFLECTIVE APIS:
>
> The method java.lang.Class.getDeclaredMethod must be special-cased to  
> always succeed for MethodHandle.invoke and for Dynamic (any method  
> name), regardless of signature.  The JSR 292 JVM has this logic  
> already, but it must be exposed out through the Class API.
>
> Only single-result reflection lookups need to be changed.  Multiple- 
> method lookups should *not* produce implicitly defined methods.
>
> The javax.lang.model API (which is used internally by javac) does not  
> need specialization, because the implicitly defined methods of  
> MethodHandle and Dynamic do not ever need to mix with other more  
> normal methods.  The static (compile-time) model of Dynamic may not  
> present any enclosed elemeents, while that of MethodHandle must not  
> present any methods named "invoke".
>
> Facilities which compute type relations (such as  
> javax.lang.model.util.Types) may need to be updated to take Dynamic  
> into account.  Generally speaking, the new Dynamic conversions operate  
> in parallel to the implicit boxing conversions.  That is, they add no  
> new subtype or supertype relations, but they provide a few more ways  
> for values to be implicitly converted or casted.
>   

Yes, I would expect a few changes to the type-related APIs.  They may 
also need to be changes to programs that assume Object is the root of 
the reference type hierarchy.  I know I've written annotation processing 
code like that and Dynamic would need to be special cased in there.

-Joe



From vapor1 at teleport.com  Fri Apr  3 01:26:41 2009
From: vapor1 at teleport.com (Derek Foster)
Date: Fri, 3 Apr 2009 04:26:41 -0400 (EDT)
Subject: PROPOSAL: 'final' without explicit type (update)
Message-ID: <31420118.1238747201155.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>



-----Original Message-----
>From: Reinier Zwitserloot <reinier at zwitserloot.com>
>Sent: Mar 31, 2009 11:28 AM
>To: Tim Lebedkov <tim.lebedkov at googlemail.com>
>Cc: coin-dev at openjdk.java.net
>Subject: Re: PROPOSAL: 'final' without explicit type (update)
>
>Tim:
>
>This isn't the first time I've read about inferring types, and this  
>isn't the first time I've seen 'final' used for it.
>
>It's -not- just to avoid a new keyword. It's quite specifically  
>because auto-typing should only be done for final variables. The  
>problem is this:
> ...

This message had a good explanation of why final is preferred, and an explanation of why not using an interface type is probably OK in this limited circumstance. Probably the best explanations of these issues I've seen. (I've just snipped it away. Read the Reiner's original post for the original description.)

>FWIW, I'm -strongly- in favour of implicit typing for final local  
>method variables, and opposed to extending this for non-finals, not  
>just because its hard to come up with a syntax for it, due to there  
>being no readily available keywords or operators to do it with. :=  
>comes to mind, but that's about it.

I agree with this, on both points. (I'm perhaps not as "strongly" in favor as Reiner, but I do think that having implicit typing for local variables would be a net positive in readability, despite the lack of an explicit type in the code. I think that implicit typing would probably be a mistake for fields, however, even if they're final. (They're accessed in too many places.) With code that uses generics a lot, the overhead of having to mention long type names multiple times starts to become large. Improved type inference would help a lot.

Derek



From vapor1 at teleport.com  Fri Apr  3 02:13:23 2009
From: vapor1 at teleport.com (Derek Foster)
Date: Fri, 3 Apr 2009 05:13:23 -0400 (EDT)
Subject: PROPOSAL: Binary Literals
Message-ID: <31379447.1238750003379.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>



-----Original Message-----
>From: Mark Thornton <mthornton at optrak.co.uk>
>Sent: Mar 26, 2009 4:54 AM
>To: Derek Foster <vapor1 at teleport.com>
>Cc: coin-dev at openjdk.java.net
>Subject: Re: PROPOSAL: Binary Literals
>
>Derek Foster wrote:
>> You are not considering the impact of constant folding on compiler optimizations.
>>
>> Not all constants are created equal. Constants whose values can be determined at compile time can be inlined by the compiler, and arithmetic expressions involving them can often therefore be simplified at compile time. This process is known as "constant folding". The resulting code need not reference the original variable to get the constant at all -- it can just use the inlined result of evaluating the expression. Additional compiler optimizations may then be performed on the basis of these folded constants. For instance, a compiler might decide to compile this code:
>>   
>Perhaps you missed my suggestion that the range of operations permitted 
>in constant expressions be extended to include the bit munging 
>operations (and possibly others). We could perhaps have an annotation 
>that was only permitted on static methods in the java.* name space and 
>which required the compiler to execute the method at compile time if its 
>arguments were compile time constants. The compiler could alternatively 
>have a private list of such methods, the annotation conveniently tells 
>everyone else what is on the list.


I did miss that suggestion, actually. Though now that you've mentioned it:

It's not that I would mind that feature in the compiler ("that feature"
being compile-time evaluation of common library
methods which are passed parameters known at compile time). However,
it doesn't sound terribly easy to implement. Especially when you consider
the implications of having to do error handling on illegal function
arguments at compile time, rather than at runtime. In fact, it sounds
a whole lot more intrusive and a lot more work for the compiler team
than just being able to parse a simple binary number.

Besides that issue, however, and besides the also (substantial!) issue
of the readability of 

(0b11010100 & 0b01001011) ^ (0b01101010 | 0b10010100)

vs. 

(Byte.parseByte("0b11010100",2) & Byte.parseByte("0b01001011",2) ^ (Byte.parseByte("0b01101010",2) | Byte.parseByte("0b10010100",2))

there is also the fact that some Java platforms simply don't HAVE a Byte
class. For instance, consider JavaCard:

http://java.sun.com/javacard/

A JavaCard, if you weren't aware, is a literally credit-card-sized computer
running a very stripped-down JVM that is just capable enough that it
can do encryption calculations in order to ensure, for instance, that
the card is connecting to an authorized and properly authenticated bank
machine. There's no room in a machine that small for the vast majority
of standard library classes, most of which would be useless anyway in
a computer of those capabilities. For instance, there is no support
for java.lang.String, java.lang.Integer, and so forth (since this
computer has no need to process Strings, and only needs integers
for the purpose of number-crunching math, not nullness checks).

Programmers for JavaCard could easily use binary numbers in their
encryption algorithms. That's a use case that is easily handled by
my proposal. However, importing a library that depends on 
Byte.parseInt(java.lang.String, int) isn't going to be sufficient
for them, because they have neither Byte nor String.

When I worked on the massively parallel processor chip I described
earlier, our Java didn't have Byte or String classes either. Even
if it had had something like String, nobody probably would have
used it. Text processing is just not the kind of thing you use a
massively parallel number crunching chip to do. Also, when each
processor on the chip has around 8Kbytes of ROM to store program code,
you don't want to be wasting it on library routines, or calls
to them, that you don't really need.

Derek








>Mark Thornton
>



From mthornton at optrak.co.uk  Fri Apr  3 02:59:52 2009
From: mthornton at optrak.co.uk (Mark Thornton)
Date: Fri, 03 Apr 2009 10:59:52 +0100
Subject: PROPOSAL: Binary Literals
In-Reply-To: <31379447.1238750003379.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>
References: <31379447.1238750003379.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>
Message-ID: <49D5DE18.3000606@optrak.co.uk>

Derek Foster wrote:
>   
> I did miss that suggestion, actually. Though now that you've mentioned it:
>
> It's not that I would mind that feature in the compiler ("that feature"
> being compile-time evaluation of common library
> methods which are passed parameters known at compile time). However,
> it doesn't sound terribly easy to implement. Especially when you consider
> the implications of having to do error handling on illegal function
> arguments at compile time, rather than at runtime. In fact, it sounds
> a whole lot more intrusive and a lot more work for the compiler team
> than just being able to parse a simple binary number.
>   
They already have to handle the exception resulting from integer 
division by zero, so I don't think this makes much difference to compile 
time expression evaluation. This is especially true if only methods in 
the java namespace were permitted (and these could be restricted to 
'easy' methods).

> there is also the fact that some Java platforms simply don't HAVE a Byte
> class. For instance, consider JavaCard:
>
> http://java.sun.com/javacard/
>
> A JavaCard, if you weren't aware, is a literally credit-card-sized computer
>   
I was aware it existed but my Java experience hasn't gone any lower than 
JavaME. However when expressions are evaluated at compile time the 
resulting byte code contains no reference to the source of the 
computation -- only the result appears. Thus the fact that Byte isn't 
available in the target platform wouldn't matter. For example:

class A {
    public static final String STREET="Mead Lane";
}

class B {
    public static final String TOWN = "Hertford";
}

class MyApp {
    public static final String ADDRESS = A.STREET + "," + B.TOWN;
}

The byte code for MyApp contains
    ADDRESS = "Mead Lane, Hertford"

and no reference to classes A, or B. I don't like this behaviour, but it 
is what currently happens. I think it was intended to assist with 
implementation on restricted environments.

Regards,
Mark Thornton



From reinier at zwitserloot.com  Fri Apr  3 03:14:57 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Fri, 3 Apr 2009 12:14:57 +0200
Subject: Naked dot - accessing object fields through unqualified
In-Reply-To: <19432589.1238742258930.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>
References: <19432589.1238742258930.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>
Message-ID: <763DE2D4-9ADE-40FF-A37A-D8963DCA2CD5@zwitserloot.com>

You can think what you want, but that's not likely. Again, a source  
keyword would open up an opportunity to engage a bunch of strict  
checks, but you underestimate the amount of code that people have  
inherited from people that inherited it from people that inherited it,  
and each added their own little mess to the spaghetti. Them, and a  
bunch of contractors in between. It was thoroughly tested somewhere in  
1999, and nobody even knows how it works, but every so often someone  
does need to wade into the mess and fix something.

You can not force these people to deal with a gazillion 'these are  
likely bugs' errors. It needs to be opt-in.


Your further suggestions are even further off the mark; why is an  
abstract class with a private constructor bad? It's a matter of style;  
most people who want utility classes make their constructors final,  
but some make their class abstract as well, because of the link  
between 'abstract' classes (cannot be instantiated) and utility  
classes (should not be instantiated). I believe a programming language  
should set style as much as possible, but java doesn't do that now,  
and changing it is a massive turn-around in java dogma that you or I  
just cannot take.

C style array declarations - okay, fine. Yes. Guuuuhhhh, they are  
making working with the [ and ] symbols in a way that doesn't screw up  
the parser annoying, to say the least. Yet another argument for a  
'source' keyword.


If people don't want to listen to or setup their warnings, then more  
errors is just not going to help. Your suggestion is: Some companies  
are so boneheaded they won't listen to their IDE's warnings, so we'll  
just force it on them with a javac change? Nononono. That'll just  
result in them not updating their java, and that's one of those things  
sun (rightfully) wants to avoid like the plague without a solid reason  
to do it (like wiping the slate clean across the board, not just in  
this niche area).

At any rate, there's no way to centralize errors/warnings in javac.  
Period. They are far too contentious. As I have said before, APT is a  
good start, but some more support for external warning/error plugins  
would help (including the ability to add more SuppressWarnings  
keywords). It would be nice if javac shipped out of the box with an  
extensive set, sure, but, again, opt-in.





  --Reinier Zwitserloot



On Apr 3, 2009, at 09:04, Derek Foster wrote:

> Replies inline.
>
> -----Original Message-----
>> From: Reinier Zwitserloot <reinier at zwitserloot.com>
>> Sent: Mar 31, 2009 9:03 AM
>> To: Derek Foster <vapor1 at teleport.com>
>> Cc: coin-dev at openjdk.java.net
>> Subject: Re: Naked dot - accessing object fields through  
>> unqualified "." [C1]
>>
>> 'Self-assignment is forbidden' would not be backwards compatibile.
>> Yes, such code would most likely be a bug, but its still an issue. It
>> would have to be a warning, at best.
>
> Personally, I think it should be an error, since there seems to be  
> no valid reason to do it, and it almost certainly indicates a bug. I  
> think that compilers should default to being in a 'strict' mode  
> where things like this that have been found to be bad ideas with  
> virtually no upside are treated as illegal, even if that makes them  
> not fully backwards compatible. For backwards compatibility, there  
> could be a command-line switch to turn off strict mode if necessary  
> for compiling old code.
>
> Some other things I'd like to see in this category:
>
> * Having an abstract class with a constructor that has 'public' or  
> 'private' access.
>
> * Using C-style array declarations. (int x[] instead of int[] x)
>
> I could probably think of a few more.
>
>> However:
>>
>> Every single external java compiler I know of will warn you when you
>> self-assign. Eclipse does it. So does netbeans. So does IDEA. So does
>> pmd. So does findbugs.
>
> Mere warnings are not enough to stop people from doing this sort of  
> thing, especially when the warning message is buried in 436 other  
> warning messages about code which is less unambiguously broken than  
> this is. (Note: I *HATE* it when people ignore compiler warnings  
> like this, but I am speaking from experience when I say that it  
> usually takes years to convince a company to clean up its act.)  
> Unfortunately, I have worked for lots of companies that routinely  
> ignore warnings.
>
>> If you internalize the self-assignment warning, where do you stop?
>> There are literally hundreds of 'duh, that must be a bug' warnings  
>> you
>> could generate. Not all of them are as obvious, or as non- 
>> contentious,
>> as 'self assignment'. So, where do you stop? Do we use the glacial
>> nature of the language changes process to set this up?
>
> I think that when a practice is almost always problematic, is easy  
> to fix, and has no legitimate purpose (and/or has an easy workaround  
> in the few cases that it is legitimate), it should be made an error  
> (with the caveats above). I don't think that we should carry along  
> every single design mistake in the 1.0 edition of the Java Language  
> Standard with us until the end of time. The ability to achieve  
> backwards compatibility is important (hence the ability to turn off  
> strict mode I described above), but clarity of language design and  
> preventing common errors is too. Otherwise, the amount of code which  
> contains the error in question just keeps growing over time.
>
>> I say: No. The
>> community has done a fine job of addressing these issues by creating
>> code checkers.
>
> In my experience, the community, by and large, does not use code  
> checkers. Relatively few companies do. Again, I wish it were  
> otherwise, but the truth is that most companies assume that if  
> something passes the checks done by the compiler, it's probably  
> fine. Having tried to introduce them into companies a few times, I  
> can report that most software engineers really don't want to be  
> bothered with them (and are convinced that checkers won't find any  
> bugs important enough to justify the time spent learning to use them  
> and cleaning up lots of innocuous warnings just for the sake of the  
> tool). Again, I thoroughly disagree with that philosophy, but that's  
> what I have heard repeatedly in industry.
>
> Also, using a code checker is often a painful experience if you are  
> forced to use a framework written by people who don't use them.
>
> The other issue is that every code checker checks for a different  
> set of things. Just because your code passes your code checker's  
> rules doesn't mean it will pass mine, or vice versa. The Sun Java  
> compiler as of a specific version, at least, is the same for  
> everybody.
>
>> So, I'd instead suggest:
>> Any improvements to java core in this area should focus on improving
>> the ability for external tools to integrate better. For example, a  
>> way
>> to extend @SuppressWarnings with additional keywords would be  
>> great. A
>> way to let javac auto-find (via the SPI system) 'warning/error'
>> plugins would be another fine idea. Having any kind of plugin system
>> for the official javac to give other tools a go at creating warnings
>> and errors on the AST that javac's parser is building would be good
>> already, using SPI to find these automatically is just one way of
>> doing it. I'm not sure APT is quite right for the job; I don't want  
>> to
>> litter annotations to the gist of '@ExtensivelyCheckMe' all over the
>> place.
>
> I'm certainly in favor of making life easier for code checkers.  
> However, checkers that don't get used are no better than ones that  
> don't exist. Javac (or jikes, etc.) gets used every time someone  
> compiles a program. That means it's going to have far more influence  
> on the correctness of the majority of Java code than any other tool.
>
> Derek
>
>>
>>
>> --Reinier Zwitserloot
>>
>>
>>
>> On Mar 29, 2009, at 04:42, Derek Foster wrote:
>>
>>> The major problem I have with this proposal is that it does not
>>> address the point of why I use a prefix on field names. As such, I
>>> would still continue to use a prefix even if this proposal were
>>> implemented.
>>>
>>> In short, I use a prefix to avoid typographical mistakes, like this
>>> one:
>>>
>>> void setFoo(Thing foob) { // Typo!
>>>   this.foo = foo;
>>> }
>>>
>>> This will compile, and no warnings are produced, but it ends up
>>> assigning foo to itself, which is not what was intended.
>>>
>>> Your proposal has exactly the same problem:
>>>
>>> void setFoo(Thing foob) { // Typo!
>>>   .foo = foo;
>>> }
>>>
>>> It therefore does not substitute for a field prefix, which WILL fix
>>> the problem:
>>>
>>> void setFoo(Thing foob) { // Typo!
>>>   _foo = foo; // ERROR! Undefined variable 'foo'.
>>> }
>>>
>>> So unless you had some way to make use of the dot prefix mandatory
>>> and the only legal way to access fields (which I would like, but
>>> which would be an extremely backwards-incompatible change that will
>>> never happen in Java), I don't see that adding an optional dot
>>> prefix helps the situation except to reduce typing in constructor
>>> and setter methods slightly.
>>>
>>> (Note: I would love a "self-assignment is forbidden" change to Java.
>>> If I have time after my other proposals, I might write one up.
>>> (Anyone else want to volunteer? This one is easy!) I might be
>>> willing to forego prefixes and use the "this.foo = foo" approach, or
>>> even the ".foo = foo" approach, if I was sure it wouldn't cause me
>>> to fall into the self-assignment trap.)
>>>
>>> Derek
>>>
>>>
>>
>



From Thomas.Hawtin at Sun.COM  Fri Apr  3 03:24:24 2009
From: Thomas.Hawtin at Sun.COM (Tom Hawtin)
Date: Fri, 03 Apr 2009 11:24:24 +0100
Subject: Proposal: Sameness operators
In-Reply-To: <49D5B109.2020007@sun.com>
References: <2729451.1238478698193.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
	<b2b0980e4fe3d8d30d07f47c9bdc2b4e-EhVcX19AQQFeRwsRBAEdSjBXdh9XVlpBXkJHHF5aNkhfS1kPWUFwB0tWWDBeQ0YKWVpRSVFR-webmailer2@server05.webmailer.hosteurope.de>
	<49D3B1E3.8070109@sun.com>
	<88885FEA-F3CF-4D47-8379-7571E9E31F76@zwitserloot.com>
	<4b4f45e00904020524p27741baeo40483e83d71dc768@mail.gmail.com>
	<275433EA-A420-42C8-891D-3B0C2629222A@zwitserloot.com>
	<49D54420.5090906@sun.com>
	<aad309390904022335t253529ees538f0287f5a0cb93@mail.gmail.com>
	<49D5B109.2020007@sun.com>
Message-ID: <49D5E3D8.8020901@sun.com>

Joseph D. Darcy wrote:

> Yes, I meant to type "java.util.Objects"  -- having a class other than 
> java.lang.Object named "Object" is just wrong!

But having an interface named "Object" is just CORBA!

Tom


From reinier at zwitserloot.com  Fri Apr  3 03:27:40 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Fri, 3 Apr 2009 12:27:40 +0200
Subject: PROPOSAL: @OverrideAll annotation
In-Reply-To: <17542308.1238746196681.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>
References: <17542308.1238746196681.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>
Message-ID: <61773C12-3611-452A-B0A1-8B873F0E47E1@zwitserloot.com>

What Derek said - this is not a good idea.

rssh: The proposal specifically states that each non-overridden method  
is to be generated with an empty body, or if that isn't possible due  
to a return type, the default return for that type (0/false/0.0/'\0'/ 
null).



  --Reinier Zwitserloot



On Apr 3, 2009, at 10:09, Derek Foster wrote:

> My major problem with this proposal is that it doesn't seem to be  
> straightforward to generate the bodies of methods that have to  
> return something. Particularly for code such as implementations of  
> the Visitor pattern.
>
> Having un-overridden methods simply return null or zero is often not  
> the right thing to do.
>
> It's OK for generating methods that just take parameters, I suppose.
>
> Still, having annotations generate code or otherwise affect the  
> operation of a program is apparently a no-no per Sun's rules. If  
> something like this is going to happen, I think it needs a new  
> keyword or something rather than using an annotation.
>
> (Although, personally, I don't think it would be such a bad thing if  
> code generation via annotation existed, but were limited only to  
> certain annotations in a specific package duly designated by the  
> language implementors. Annotations have one nice quality that other  
> ways of extending the language don't: You can create new "keywords"  
> at will with no risk of breaking someone's perfectly-working code.  
> If they don't import the annotation, they won't need to be impacted  
> by it. I sort of wish there was an alternative to annotations (@@Foo  
> instead of @Foo?) which was explicitly for the purpose of telling  
> the compiler to generate boilerplate code of various types.  
> Decorators in Python sort of serve this purpose, for instance.)
>
> Derek
>
> -----Original Message-----
>> From: rssh at gradsoft.com.ua
>> Sent: Mar 31, 2009 10:02 AM
>> To: Gabriel Belingueres <belingueres at gmail.com>
>> Cc: coin-dev <coin-dev at openjdk.java.net>
>> Subject: Re: PROPOSAL: @OverrideAll annotation
>>
>>> Hi,
>>>
>>> I've written a new feature that might be comfortable to use for
>>> someone. All input is welcomed.
>>>
>>
>> It-is possible to do near same with annotation API (create a  
>> superclass
>> which will override all)
>>
>> But -- sometime we really need to say, that all methods 'mus be'
>> overriden.  (For example - when implementing Proxy pattern).
>> In such case class-level annotation '@OverrideAll'  which tell  
>> compiler
>> to check, that all methods must be overriden -- brilliant idea.
>>
>>
>>
>>
>>
>>> Regards,
>>> Gabriel
>>>
>>> PROJECT COIN SMALL LANGUAGE CHANGE PROPOSAL FORM v1.0
>>>
>>> AUTHOR(S): Gabriel Belingueres
>>>
>>> OVERVIEW
>>>
>>> Add an @OverrideAll annotation to allow a class to override all
>>> inherited methods with a trivial implementation. The resulting class
>>> then could be used as the basis for a Null Object pattern (or even a
>>> basic Mock object.)
>>>
>>>
>>> FEATURE SUMMARY:
>>>
>>> The proposed @OverrideAll annotation will allow the class to  
>>> override
>>> all methods (from its superclasses and implemented interfaces)  
>>> with a
>>> trivial body, but the defined class can choose to implement specific
>>> methods, replacing those that would be produced automatically by the
>>> annotation.
>>>
>>>
>>> MAJOR ADVANTAGE:
>>>
>>> Less coding for implementing Null Objects, or simple tests.
>>>
>>>
>>> MAJOR BENEFIT:
>>>
>>> Let the compiler implement all uninteresting, non relevant  
>>> behavior by
>>> automatically providing with a trivial implementation of the  
>>> inherited
>>> methods.
>>>
>>>
>>> MAJOR DISADVANTAGE:
>>>
>>> Might be a cause of NullPointerException if not used judiciously.
>>>
>>>
>>> ALTERNATIVES:
>>>
>>> Implement all uninteresting methods by yourself by providing  
>>> yourself
>>> a trivial implementation (though actually popular IDEs can do this
>>> automatically for you already.)
>>>
>>> EXAMPLES
>>>
>>> Given:
>>>
>>> class B {}
>>>
>>> public class A implements I1, I2 {
>>>
>>>  public static final int VAR = 1;
>>>
>>>  private B b;
>>>
>>>  public static Integer getSome() {
>>>    return VAR;
>>>  }
>>>
>>>  public A() {
>>>  }
>>>
>>>  public A(B b) {
>>>    this.b=b;
>>>  }
>>>
>>>  public B getB() {
>>>    return b;
>>>  }
>>>
>>>  public void setB(B b) {
>>>    this.b=b;
>>>  }
>>>
>>>  protected void doProtected() { ... }
>>>
>>>  private void doPrivate() { ... }
>>>
>>>  A someNewA() { ... }
>>>
>>>  public synchronized void someSynchronized() {
>>>  }
>>>
>>> }
>>>
>>> then:
>>>
>>> @OverrideAll
>>> public class NullA extends A {
>>> }
>>>
>>> is equivalent to declare:
>>>
>>> public class NullA extends A {
>>>
>>>  public NullA() {}
>>>
>>>  public NullA(B b) {
>>>    super(b);
>>>  }
>>>
>>>  public B getB() {
>>>    return null;
>>>  }
>>>
>>>  public void setB(B b) {
>>>  }
>>>
>>>  protected void doProtected() {
>>>   // empty
>>>  }
>>>
>>>  A someNewA() {
>>>   return null;
>>>  }
>>>
>>>  public synchronized void someSynchronized() {
>>>    // empty
>>>  }
>>>
>>> }
>>>
>>> You may not want the default trivial implementation in some methods,
>>> then you override them as usual:
>>>
>>> @OverrideAll
>>> public class NullA extends A {
>>>
>>>  @Override
>>>  public B getB() {
>>>    return new B();
>>>  }
>>>
>>>  @Override
>>>  public synchronized void someSynchronized() {
>>>    System.out.println("overridden");
>>>  }
>>>
>>> }
>>>
>>> EXAMPLE 2
>>>
>>> Implement a trivial Collection interface just to test that adding
>>> elements will increase the collection size:
>>>
>>> Currently:
>>>
>>> public class SomeCollection<E> implements Collection<E> {
>>>
>>>  private int counter;
>>>
>>>  @Override
>>>  public boolean add(E arg0) {
>>>    counter++;
>>>    return true;
>>>  }
>>>
>>>  @Override
>>>  public boolean addAll(Collection<? extends E> c) {
>>>    counter += c.size();
>>>    return true;
>>>  }
>>>
>>>  @Override
>>>  public void clear() {
>>>  }
>>>
>>>  @Override
>>>  public boolean contains(Object arg0) {
>>>    return false;
>>>  }
>>>
>>>  @Override
>>>  public boolean containsAll(Collection<?> arg0) {
>>>    return false;
>>>  }
>>>
>>>  @Override
>>>  public boolean isEmpty() {
>>>    return false;
>>>  }
>>>
>>>  @Override
>>>  public Iterator<E> iterator() {
>>>    return null;
>>>  }
>>>
>>>  @Override
>>>  public boolean remove(Object arg0) {
>>>    return false;
>>>  }
>>>
>>>  @Override
>>>  public boolean removeAll(Collection<?> arg0) {
>>>    return false;
>>>  }
>>>
>>>  @Override
>>>  public boolean retainAll(Collection<?> arg0) {
>>>    return false;
>>>  }
>>>
>>>  @Override
>>>  public int size() {
>>>    return counter;
>>>  }
>>>
>>>  @Override
>>>  public Object[] toArray() {
>>>    return null;
>>>  }
>>>
>>>  @Override
>>>  public <T> T[] toArray(T[] arg0) {
>>>    return null;
>>>  }
>>>
>>> }
>>>
>>> With the annotation:
>>>
>>> @OverrideAll
>>> public class SomeCollection<E> implements Collection<E> {
>>>
>>>  private int counter;
>>>
>>>  @Override
>>>  public boolean add(E arg0) {
>>>    counter++;
>>>    return true;
>>>  }
>>>
>>>  @Override
>>>  public boolean addAll(Collection<? extends E> c) {
>>>    counter += c.size();
>>>    return true;
>>>  }
>>>
>>>
>>>  @Override
>>>  public int size() {
>>>    return counter;
>>>  }
>>>
>>> }
>>>
>>>
>>> DETAILS
>>>
>>>
>>> SPECIFICATION:
>>>
>>> A preliminary specification follows:
>>>
>>> As this feature is proposed as an annotation for code generation, no
>>> changes to the current JLSv3 are needed.
>>>
>>> The annotation will generate "trivial" overridden implementations  
>>> for
>>> all methods not specified in the class, for each superclass in the
>>> hierarchy (except Object) and implemented interface.
>>>
>>> - Static methods, private methods, final methods, constructors and
>>> methods from class Object should never be generated.
>>> - If some superclass (except Object) has already overridden some
>>> Object class methods, then do NOT generate an empty overridden  
>>> method
>>> (to reuse current behavior.) (for example, if some superclass  
>>> already
>>> override toString(), equals() or hashCode().)
>>>
>>> - OPTIONAL: add a parameter to the @OverrideAll annotation to  
>>> indicate
>>> if @Deprecated methods should not be implemented.
>>>
>>> Trivial implementation for generated methods:
>>>
>>> - Methods returning void will have an empty body. (OPTIONAL: add a
>>> parameter to the @OverrideAll annotation to indicate that it should
>>> throw UnsupportedOperationException instead)
>>> - Methods returning a primitive type will have a body returning the
>>> same default value that would have for uninitialized instance
>>> variables. (JLS section 4.12.5.)
>>> - Methods returning a reference type will "return null;". (JLS  
>>> section
>>> 4.12.5.)
>>> - The method will never return a covariant return type (because in
>>> case of implementing a Null object, it should be undistinguished  
>>> from
>>> the common case)
>>> - Methods that throws checked exceptions can be modified to delete  
>>> the
>>> throws clause. (ie. the trivial implementation should not throw
>>> checked exceptions)
>>> - Synchronized methods should retain that attribute.
>>>
>>>
>>> COMPILATION:
>>>
>>> Compilation should proceed as usual, except that the annotation
>>> processor would generate the code when it encounters an annotated
>>> class.
>>>
>>> No changes to the class file format are needed.
>>>
>>>
>>> TESTING
>>>
>>> Test cases should be done, including testing with classes  
>>> implementing
>>> several interfaces, classes with generics, inner classes, etc.
>>>
>>>
>>> LIBRARY SUPPORT:
>>>
>>> No, except creating the new annotation.
>>>
>>>
>>> REFLECTIVE APIS:
>>>
>>> No changes foreseen.
>>>
>>>
>>> OTHER CHANGES:
>>>
>>> Output of javadoc tool.
>>>
>>>
>>> MIGRATION:
>>>
>>> Just add the annotation to class level, and erase your trivially
>>> implemented overridden methods.
>>>
>>>
>>> COMPATIBILITY
>>>
>>> BREAKING CHANGES:
>>> All existing programs remain valid.
>>>
>>> EXISTING PROGRAMS:
>>> The semantics of existing class files and legal source files are
>>> unchanged by this feature.
>>>
>>>
>>> REFERENCES
>>>
>>> EXISTING BUGS:
>>>
>>> None that I know about.
>>>
>>> URL FOR PROTOTYPE:
>>>
>>> None at this time.
>>>
>>>
>>
>>
>>
>
>



From reinier at zwitserloot.com  Fri Apr  3 03:34:47 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Fri, 3 Apr 2009 12:34:47 +0200
Subject: PROPOSAL: Binary Literals
In-Reply-To: <31379447.1238750003379.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>
References: <31379447.1238750003379.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>
Message-ID: <483055E7-EAC0-4FF0-9B11-2F828F90B917@zwitserloot.com>

public static byte b(String in) {
     return Byte.parseByte(in, 2);
}


then:


(0b11010100 & 0b01001011) ^ (0b01101010 | 0b10010100)


vs:

import static ByteUtils.b;

(b("11010100") & b("01001011")) ^ (b("01101010") | b("10010100"))



I can live with that.


  --Reinier Zwitserloot



On Apr 3, 2009, at 11:13, Derek Foster wrote:

>
>
> -----Original Message-----
>> From: Mark Thornton <mthornton at optrak.co.uk>
>> Sent: Mar 26, 2009 4:54 AM
>> To: Derek Foster <vapor1 at teleport.com>
>> Cc: coin-dev at openjdk.java.net
>> Subject: Re: PROPOSAL: Binary Literals
>>
>> Derek Foster wrote:
>>> You are not considering the impact of constant folding on compiler  
>>> optimizations.
>>>
>>> Not all constants are created equal. Constants whose values can be  
>>> determined at compile time can be inlined by the compiler, and  
>>> arithmetic expressions involving them can often therefore be  
>>> simplified at compile time. This process is known as "constant  
>>> folding". The resulting code need not reference the original  
>>> variable to get the constant at all -- it can just use the inlined  
>>> result of evaluating the expression. Additional compiler  
>>> optimizations may then be performed on the basis of these folded  
>>> constants. For instance, a compiler might decide to compile this  
>>> code:
>>>
>> Perhaps you missed my suggestion that the range of operations  
>> permitted
>> in constant expressions be extended to include the bit munging
>> operations (and possibly others). We could perhaps have an annotation
>> that was only permitted on static methods in the java.* name space  
>> and
>> which required the compiler to execute the method at compile time  
>> if its
>> arguments were compile time constants. The compiler could  
>> alternatively
>> have a private list of such methods, the annotation conveniently  
>> tells
>> everyone else what is on the list.
>
>
> I did miss that suggestion, actually. Though now that you've  
> mentioned it:
>
> It's not that I would mind that feature in the compiler ("that  
> feature"
> being compile-time evaluation of common library
> methods which are passed parameters known at compile time). However,
> it doesn't sound terribly easy to implement. Especially when you  
> consider
> the implications of having to do error handling on illegal function
> arguments at compile time, rather than at runtime. In fact, it sounds
> a whole lot more intrusive and a lot more work for the compiler team
> than just being able to parse a simple binary number.
>
> Besides that issue, however, and besides the also (substantial!) issue
> of the readability of
>
> (0b11010100 & 0b01001011) ^ (0b01101010 | 0b10010100)
>
> vs.
>
> (Byte.parseByte("0b11010100",2) & Byte.parseByte("0b01001011",2) ^  
> (Byte.parseByte("0b01101010",2) | Byte.parseByte("0b10010100",2))
>
> there is also the fact that some Java platforms simply don't HAVE a  
> Byte
> class. For instance, consider JavaCard:
>
> http://java.sun.com/javacard/
>
> A JavaCard, if you weren't aware, is a literally credit-card-sized  
> computer
> running a very stripped-down JVM that is just capable enough that it
> can do encryption calculations in order to ensure, for instance, that
> the card is connecting to an authorized and properly authenticated  
> bank
> machine. There's no room in a machine that small for the vast majority
> of standard library classes, most of which would be useless anyway in
> a computer of those capabilities. For instance, there is no support
> for java.lang.String, java.lang.Integer, and so forth (since this
> computer has no need to process Strings, and only needs integers
> for the purpose of number-crunching math, not nullness checks).
>
> Programmers for JavaCard could easily use binary numbers in their
> encryption algorithms. That's a use case that is easily handled by
> my proposal. However, importing a library that depends on
> Byte.parseInt(java.lang.String, int) isn't going to be sufficient
> for them, because they have neither Byte nor String.
>
> When I worked on the massively parallel processor chip I described
> earlier, our Java didn't have Byte or String classes either. Even
> if it had had something like String, nobody probably would have
> used it. Text processing is just not the kind of thing you use a
> massively parallel number crunching chip to do. Also, when each
> processor on the chip has around 8Kbytes of ROM to store program code,
> you don't want to be wasting it on library routines, or calls
> to them, that you don't really need.
>
> Derek
>
>
>
>
>
>
>
>
>> Mark Thornton
>>
>
>



From mthornton at optrak.co.uk  Fri Apr  3 03:48:37 2009
From: mthornton at optrak.co.uk (Mark Thornton)
Date: Fri, 03 Apr 2009 11:48:37 +0100
Subject: Annotation processors
Message-ID: <49D5E985.8010408@optrak.co.uk>

These have come up several times on this list. I suspect many people 
have only a vague idea of what they can do. Is there any good 
documentation or introductory material available?

Mark Thornton



From pdoubleya at gmail.com  Fri Apr  3 04:05:38 2009
From: pdoubleya at gmail.com (Patrick Wright)
Date: Fri, 3 Apr 2009 13:05:38 +0200
Subject: Annotation processors
In-Reply-To: <49D5E985.8010408@optrak.co.uk>
References: <49D5E985.8010408@optrak.co.uk>
Message-ID: <64efa1ba0904030405w4d68cec9xbee57f8a9969ec25@mail.gmail.com>

Here are some links I found on searching for this yesterday

http://today.java.net/pub/a/today/2008/04/10/source-code-analysis-using-java-6-compiler-apis.html
http://blogs.sun.com/sundararajan/entry/javac_tree_api_-_check
http://scg.unibe.ch/archive/projects/Erni08b.pdf
http://java.sun.com/javase/6/docs/technotes/guides/javac/index.html
http://smallwiki.unibe.ch/adriankuhn/javacompiler/


HTH
Patrick


From mthornton at optrak.co.uk  Fri Apr  3 04:21:02 2009
From: mthornton at optrak.co.uk (Mark Thornton)
Date: Fri, 03 Apr 2009 12:21:02 +0100
Subject: Annotation processors
In-Reply-To: <64efa1ba0904030405w4d68cec9xbee57f8a9969ec25@mail.gmail.com>
References: <49D5E985.8010408@optrak.co.uk>
	<64efa1ba0904030405w4d68cec9xbee57f8a9969ec25@mail.gmail.com>
Message-ID: <49D5F11E.9030806@optrak.co.uk>

Thanks

Patrick Wright wrote:
> http://scg.unibe.ch/archive/projects/Erni08b.pdf
>   
I like the section: "How to abuse JSR269 for AST rewriting". I wonder if 
I can use that to extend the compile time evaluation of constant 
expressions.

Regards,
Mark


From belingueres at gmail.com  Fri Apr  3 08:23:59 2009
From: belingueres at gmail.com (Gabriel Belingueres)
Date: Fri, 3 Apr 2009 12:23:59 -0300
Subject: PROPOSAL: @OverrideAll annotation
In-Reply-To: <61773C12-3611-452A-B0A1-8B873F0E47E1@zwitserloot.com>
References: <17542308.1238746196681.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>
	<61773C12-3611-452A-B0A1-8B873F0E47E1@zwitserloot.com>
Message-ID: <cf66e280904030823o6aafd62fx170ac538c3866761@mail.gmail.com>

Hi,

Thanks for taking the time for reading this.

@Derek: My current approach for implementing this feature is to use
the reflection API to get the Methods and generate from there the
source file. (I'm not very experienced with the annotation API so this
may not be the shortest path to do it, but for a first try I think
it's OK.) However my mayor problem here is how to generate the
concrete class, for example let's say we have:

class A {
  public void method1() {};
  public void method2() {};
}
@OverrideAll
class B extends A {
  public void method1() {
    ...
  }
}

the easiest way I'm thinking I can generate the code is to create a
superclass class A_overrideAll which extends A with all methods
overridden, and then make B extends A_overrideAll. However, AFAIK I
can't modify the original source file (where class B is declared) so
how can now make it a subclass of A_overrideAll?

I choose an annotation instead of introducing a new keyword because it
was less intrusive than the other, that is, with a new keyword I would
need to modify the JLS, which is unnecessary because no language rule
changes. If further analysis reveal that a new keyword would be better
than an annotation, then it's fine with me.

@rssh: no compile time error should be thrown, instead, at runtime the
execution of a method should have a default behavior. In terms of the
language, the most basic behavior is do nothing/return default values,
but in general, the idea was to create a Null Object, meaning that the
client code could call methods that do nothing instead of checking for
!= null. (Hopefully you could avoid some NPEs with this idiom.)

Other idiom that apply for @OverrideAll are the AWT/Swing Listeners
and Adapters. There are lots of XXXListener interfaces with an
associated XXXAdapter abstract class that are used with a (sometimes
anonymous) class just to listen to particular events offered in the
listener interface.  With the @OverrideAll annotation, you could avoid
the declaration of the abstract adapter class.

Regards,
Gabriel

2009/4/3 Reinier Zwitserloot <reinier at zwitserloot.com>:
> What Derek said - this is not a good idea.
>
> rssh: The proposal specifically states that each non-overridden method
> is to be generated with an empty body, or if that isn't possible due
> to a return type, the default return for that type (0/false/0.0/'\0'/
> null).
>
>
>
> ?--Reinier Zwitserloot
>
>
>
> On Apr 3, 2009, at 10:09, Derek Foster wrote:
>
>> My major problem with this proposal is that it doesn't seem to be
>> straightforward to generate the bodies of methods that have to
>> return something. Particularly for code such as implementations of
>> the Visitor pattern.
>>
>> Having un-overridden methods simply return null or zero is often not
>> the right thing to do.
>>
>> It's OK for generating methods that just take parameters, I suppose.
>>
>> Still, having annotations generate code or otherwise affect the
>> operation of a program is apparently a no-no per Sun's rules. If
>> something like this is going to happen, I think it needs a new
>> keyword or something rather than using an annotation.
>>
>> (Although, personally, I don't think it would be such a bad thing if
>> code generation via annotation existed, but were limited only to
>> certain annotations in a specific package duly designated by the
>> language implementors. Annotations have one nice quality that other
>> ways of extending the language don't: You can create new "keywords"
>> at will with no risk of breaking someone's perfectly-working code.
>> If they don't import the annotation, they won't need to be impacted
>> by it. I sort of wish there was an alternative to annotations (@@Foo
>> instead of @Foo?) which was explicitly for the purpose of telling
>> the compiler to generate boilerplate code of various types.
>> Decorators in Python sort of serve this purpose, for instance.)
>>
>> Derek
>>
>> -----Original Message-----
>>> From: rssh at gradsoft.com.ua
>>> Sent: Mar 31, 2009 10:02 AM
>>> To: Gabriel Belingueres <belingueres at gmail.com>
>>> Cc: coin-dev <coin-dev at openjdk.java.net>
>>> Subject: Re: PROPOSAL: @OverrideAll annotation
>>>
>>>> Hi,
>>>>
>>>> I've written a new feature that might be comfortable to use for
>>>> someone. All input is welcomed.
>>>>
>>>
>>> It-is possible to do near same with annotation API (create a
>>> superclass
>>> which will override all)
>>>
>>> But -- sometime we really need to say, that all methods 'mus be'
>>> overriden. ?(For example - when implementing Proxy pattern).
>>> In such case class-level annotation '@OverrideAll' ?which tell
>>> compiler
>>> to check, that all methods must be overriden -- brilliant idea.
>>>
>>>
>>>
>>>
>>>
>>>> Regards,
>>>> Gabriel
>>>>
>>>> PROJECT COIN SMALL LANGUAGE CHANGE PROPOSAL FORM v1.0
>>>>
>>>> AUTHOR(S): Gabriel Belingueres
>>>>
>>>> OVERVIEW
>>>>
>>>> Add an @OverrideAll annotation to allow a class to override all
>>>> inherited methods with a trivial implementation. The resulting class
>>>> then could be used as the basis for a Null Object pattern (or even a
>>>> basic Mock object.)
>>>>
>>>>
>>>> FEATURE SUMMARY:
>>>>
>>>> The proposed @OverrideAll annotation will allow the class to
>>>> override
>>>> all methods (from its superclasses and implemented interfaces)
>>>> with a
>>>> trivial body, but the defined class can choose to implement specific
>>>> methods, replacing those that would be produced automatically by the
>>>> annotation.
>>>>
>>>>
>>>> MAJOR ADVANTAGE:
>>>>
>>>> Less coding for implementing Null Objects, or simple tests.
>>>>
>>>>
>>>> MAJOR BENEFIT:
>>>>
>>>> Let the compiler implement all uninteresting, non relevant
>>>> behavior by
>>>> automatically providing with a trivial implementation of the
>>>> inherited
>>>> methods.
>>>>
>>>>
>>>> MAJOR DISADVANTAGE:
>>>>
>>>> Might be a cause of NullPointerException if not used judiciously.
>>>>
>>>>
>>>> ALTERNATIVES:
>>>>
>>>> Implement all uninteresting methods by yourself by providing
>>>> yourself
>>>> a trivial implementation (though actually popular IDEs can do this
>>>> automatically for you already.)
>>>>
>>>> EXAMPLES
>>>>
>>>> Given:
>>>>
>>>> class B {}
>>>>
>>>> public class A implements I1, I2 {
>>>>
>>>> ?public static final int VAR = 1;
>>>>
>>>> ?private B b;
>>>>
>>>> ?public static Integer getSome() {
>>>> ? ?return VAR;
>>>> ?}
>>>>
>>>> ?public A() {
>>>> ?}
>>>>
>>>> ?public A(B b) {
>>>> ? ?this.b=b;
>>>> ?}
>>>>
>>>> ?public B getB() {
>>>> ? ?return b;
>>>> ?}
>>>>
>>>> ?public void setB(B b) {
>>>> ? ?this.b=b;
>>>> ?}
>>>>
>>>> ?protected void doProtected() { ... }
>>>>
>>>> ?private void doPrivate() { ... }
>>>>
>>>> ?A someNewA() { ... }
>>>>
>>>> ?public synchronized void someSynchronized() {
>>>> ?}
>>>>
>>>> }
>>>>
>>>> then:
>>>>
>>>> @OverrideAll
>>>> public class NullA extends A {
>>>> }
>>>>
>>>> is equivalent to declare:
>>>>
>>>> public class NullA extends A {
>>>>
>>>> ?public NullA() {}
>>>>
>>>> ?public NullA(B b) {
>>>> ? ?super(b);
>>>> ?}
>>>>
>>>> ?public B getB() {
>>>> ? ?return null;
>>>> ?}
>>>>
>>>> ?public void setB(B b) {
>>>> ?}
>>>>
>>>> ?protected void doProtected() {
>>>> ? // empty
>>>> ?}
>>>>
>>>> ?A someNewA() {
>>>> ? return null;
>>>> ?}
>>>>
>>>> ?public synchronized void someSynchronized() {
>>>> ? ?// empty
>>>> ?}
>>>>
>>>> }
>>>>
>>>> You may not want the default trivial implementation in some methods,
>>>> then you override them as usual:
>>>>
>>>> @OverrideAll
>>>> public class NullA extends A {
>>>>
>>>> ?@Override
>>>> ?public B getB() {
>>>> ? ?return new B();
>>>> ?}
>>>>
>>>> ?@Override
>>>> ?public synchronized void someSynchronized() {
>>>> ? ?System.out.println("overridden");
>>>> ?}
>>>>
>>>> }
>>>>
>>>> EXAMPLE 2
>>>>
>>>> Implement a trivial Collection interface just to test that adding
>>>> elements will increase the collection size:
>>>>
>>>> Currently:
>>>>
>>>> public class SomeCollection<E> implements Collection<E> {
>>>>
>>>> ?private int counter;
>>>>
>>>> ?@Override
>>>> ?public boolean add(E arg0) {
>>>> ? ?counter++;
>>>> ? ?return true;
>>>> ?}
>>>>
>>>> ?@Override
>>>> ?public boolean addAll(Collection<? extends E> c) {
>>>> ? ?counter += c.size();
>>>> ? ?return true;
>>>> ?}
>>>>
>>>> ?@Override
>>>> ?public void clear() {
>>>> ?}
>>>>
>>>> ?@Override
>>>> ?public boolean contains(Object arg0) {
>>>> ? ?return false;
>>>> ?}
>>>>
>>>> ?@Override
>>>> ?public boolean containsAll(Collection<?> arg0) {
>>>> ? ?return false;
>>>> ?}
>>>>
>>>> ?@Override
>>>> ?public boolean isEmpty() {
>>>> ? ?return false;
>>>> ?}
>>>>
>>>> ?@Override
>>>> ?public Iterator<E> iterator() {
>>>> ? ?return null;
>>>> ?}
>>>>
>>>> ?@Override
>>>> ?public boolean remove(Object arg0) {
>>>> ? ?return false;
>>>> ?}
>>>>
>>>> ?@Override
>>>> ?public boolean removeAll(Collection<?> arg0) {
>>>> ? ?return false;
>>>> ?}
>>>>
>>>> ?@Override
>>>> ?public boolean retainAll(Collection<?> arg0) {
>>>> ? ?return false;
>>>> ?}
>>>>
>>>> ?@Override
>>>> ?public int size() {
>>>> ? ?return counter;
>>>> ?}
>>>>
>>>> ?@Override
>>>> ?public Object[] toArray() {
>>>> ? ?return null;
>>>> ?}
>>>>
>>>> ?@Override
>>>> ?public <T> T[] toArray(T[] arg0) {
>>>> ? ?return null;
>>>> ?}
>>>>
>>>> }
>>>>
>>>> With the annotation:
>>>>
>>>> @OverrideAll
>>>> public class SomeCollection<E> implements Collection<E> {
>>>>
>>>> ?private int counter;
>>>>
>>>> ?@Override
>>>> ?public boolean add(E arg0) {
>>>> ? ?counter++;
>>>> ? ?return true;
>>>> ?}
>>>>
>>>> ?@Override
>>>> ?public boolean addAll(Collection<? extends E> c) {
>>>> ? ?counter += c.size();
>>>> ? ?return true;
>>>> ?}
>>>>
>>>>
>>>> ?@Override
>>>> ?public int size() {
>>>> ? ?return counter;
>>>> ?}
>>>>
>>>> }
>>>>
>>>>
>>>> DETAILS
>>>>
>>>>
>>>> SPECIFICATION:
>>>>
>>>> A preliminary specification follows:
>>>>
>>>> As this feature is proposed as an annotation for code generation, no
>>>> changes to the current JLSv3 are needed.
>>>>
>>>> The annotation will generate "trivial" overridden implementations
>>>> for
>>>> all methods not specified in the class, for each superclass in the
>>>> hierarchy (except Object) and implemented interface.
>>>>
>>>> - Static methods, private methods, final methods, constructors and
>>>> methods from class Object should never be generated.
>>>> - If some superclass (except Object) has already overridden some
>>>> Object class methods, then do NOT generate an empty overridden
>>>> method
>>>> (to reuse current behavior.) (for example, if some superclass
>>>> already
>>>> override toString(), equals() or hashCode().)
>>>>
>>>> - OPTIONAL: add a parameter to the @OverrideAll annotation to
>>>> indicate
>>>> if @Deprecated methods should not be implemented.
>>>>
>>>> Trivial implementation for generated methods:
>>>>
>>>> - Methods returning void will have an empty body. (OPTIONAL: add a
>>>> parameter to the @OverrideAll annotation to indicate that it should
>>>> throw UnsupportedOperationException instead)
>>>> - Methods returning a primitive type will have a body returning the
>>>> same default value that would have for uninitialized instance
>>>> variables. (JLS section 4.12.5.)
>>>> - Methods returning a reference type will "return null;". (JLS
>>>> section
>>>> 4.12.5.)
>>>> - The method will never return a covariant return type (because in
>>>> case of implementing a Null object, it should be undistinguished
>>>> from
>>>> the common case)
>>>> - Methods that throws checked exceptions can be modified to delete
>>>> the
>>>> throws clause. (ie. the trivial implementation should not throw
>>>> checked exceptions)
>>>> - Synchronized methods should retain that attribute.
>>>>
>>>>
>>>> COMPILATION:
>>>>
>>>> Compilation should proceed as usual, except that the annotation
>>>> processor would generate the code when it encounters an annotated
>>>> class.
>>>>
>>>> No changes to the class file format are needed.
>>>>
>>>>
>>>> TESTING
>>>>
>>>> Test cases should be done, including testing with classes
>>>> implementing
>>>> several interfaces, classes with generics, inner classes, etc.
>>>>
>>>>
>>>> LIBRARY SUPPORT:
>>>>
>>>> No, except creating the new annotation.
>>>>
>>>>
>>>> REFLECTIVE APIS:
>>>>
>>>> No changes foreseen.
>>>>
>>>>
>>>> OTHER CHANGES:
>>>>
>>>> Output of javadoc tool.
>>>>
>>>>
>>>> MIGRATION:
>>>>
>>>> Just add the annotation to class level, and erase your trivially
>>>> implemented overridden methods.
>>>>
>>>>
>>>> COMPATIBILITY
>>>>
>>>> BREAKING CHANGES:
>>>> All existing programs remain valid.
>>>>
>>>> EXISTING PROGRAMS:
>>>> The semantics of existing class files and legal source files are
>>>> unchanged by this feature.
>>>>
>>>>
>>>> REFERENCES
>>>>
>>>> EXISTING BUGS:
>>>>
>>>> None that I know about.
>>>>
>>>> URL FOR PROTOTYPE:
>>>>
>>>> None at this time.
>>>>
>>>>
>>>
>>>
>>>
>>
>>
>
>
>


From belingueres at gmail.com  Fri Apr  3 08:58:18 2009
From: belingueres at gmail.com (Gabriel Belingueres)
Date: Fri, 3 Apr 2009 12:58:18 -0300
Subject: PROPOSAL: 'final' without explicit type (update)
In-Reply-To: <31420118.1238747201155.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>
References: <31420118.1238747201155.JavaMail.root@mswamui-thinleaf.atl.sa.earthlink.net>
Message-ID: <cf66e280904030858m662fce2axf743b8d70153e9b9@mail.gmail.com>

I agree that must be valid just for final, local variables.

Regards,
Gabriel

2009/4/3 Derek Foster <vapor1 at teleport.com>:
>
>
> -----Original Message-----
>>From: Reinier Zwitserloot <reinier at zwitserloot.com>
>>Sent: Mar 31, 2009 11:28 AM
>>To: Tim Lebedkov <tim.lebedkov at googlemail.com>
>>Cc: coin-dev at openjdk.java.net
>>Subject: Re: PROPOSAL: 'final' without explicit type (update)
>>
>>Tim:
>>
>>This isn't the first time I've read about inferring types, and this
>>isn't the first time I've seen 'final' used for it.
>>
>>It's -not- just to avoid a new keyword. It's quite specifically
>>because auto-typing should only be done for final variables. The
>>problem is this:
>> ...
>
> This message had a good explanation of why final is preferred, and an explanation of why not using an interface type is probably OK in this limited circumstance. Probably the best explanations of these issues I've seen. (I've just snipped it away. Read the Reiner's original post for the original description.)
>
>>FWIW, I'm -strongly- in favour of implicit typing for final local
>>method variables, and opposed to extending this for non-finals, not
>>just because its hard to come up with a syntax for it, due to there
>>being no readily available keywords or operators to do it with. :=
>>comes to mind, but that's about it.
>
> I agree with this, on both points. (I'm perhaps not as "strongly" in favor as Reiner, but I do think that having implicit typing for local variables would be a net positive in readability, despite the lack of an explicit type in the code. I think that implicit typing would probably be a mistake for fields, however, even if they're final. (They're accessed in too many places.) With code that uses generics a lot, the overhead of having to mention long type names multiple times starts to become large. Improved type inference would help a lot.
>
> Derek
>
>
>


From Joe.Darcy at Sun.COM  Fri Apr  3 10:07:37 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Fri, 03 Apr 2009 10:07:37 -0700
Subject: Annotation processors
In-Reply-To: <49D5E985.8010408@optrak.co.uk>
References: <49D5E985.8010408@optrak.co.uk>
Message-ID: <49D64259.1020801@sun.com>

Mark Thornton wrote:
> These have come up several times on this list. I suspect many people 
> have only a vague idea of what they can do. Is there any good 
> documentation or introductory material available?
>
> Mark Thornton
>
>   

The annotation processing in javac provides immutable data structures 
modeling the types in question.  However, much of the power of providing 
mutable source files can be had by either using an annotation processor 
to generate subclasses of a class or the *superclass* of a class.  Those 
capabilities are mandated for JSR 269 annotation processing frameworks, 
as implemented in javac and Eclipse.

For example, @MakeMeAPropertyInMySuperclass annotations could be used to 
automatically generate at build time the desired property structure that 
could be inherited.  It is technically possible (a small matter of 
programming ;-) to run

@MakeMeAPropertyInMySuperclass(name="foo",type=Type.class)
class Foo extends ToBeGenerated {}

into something like

class ToBeGenerated {
    private Type foo;
    Type getFoo() {
       return foo;
    }

    Type setFoo(Type type) {
       this.type = type;
       return this.type;
    }
}

Bruce Chapman has written interesting annotation processors as part of 
his rapt and hickory projects:

https://rapt.dev.java.net/
https://hickory.dev.java.net/

-Joe



From howard.lovatt at iee.org  Sat Apr  4 21:59:07 2009
From: howard.lovatt at iee.org (Howard Lovatt)
Date: Sun, 5 Apr 2009 14:59:07 +1000
Subject: Opportunity Cost and Proposal Selection
Message-ID: <3dd3f56a0904042159r741706fdq9e081f4043850950@mail.gmail.com>

Hi All,

I would like to thanks Sun and particularly Joe for running this
process, despite the fact that I think many of my favourites will not
make 'the list' :( I think it is a very health process.

  -- Howard.


From markmahieu at googlemail.com  Sun Apr  5 04:40:55 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Sun, 5 Apr 2009 12:40:55 +0100
Subject: Proposal: Elvis and Other Null-Safe Operators
In-Reply-To: <49C27E68.7020709@gmail.com>
References: <49C201C5.3090200@gmail.com>
	<15e8b9d20903190713i67595fe1hac45db43e4dc522c@mail.gmail.com>
	<49C27E68.7020709@gmail.com>
Message-ID: <84A9B0E6-9454-4A74-AFF1-BE92D6694D05@googlemail.com>

Hi Stephen,

Revisiting an email from a couple of weeks ago...

On 19 Mar 2009, at 17:18, Stephen Colebourne wrote:

> Neal Gafter wrote:
>> On Thu, Mar 19, 2009 at 1:26 AM, Jacek Kolodziejczyk
>> <jacek.p.kolodziejczyk at gmail.com> wrote:
>>
>>> In my opinion the most obtrusive part in the current state of  
>>> proposals
>>> is assumption that the invocation on null object should always  
>>> return null.
>>> If I understand it correctly the following would break at runtime,
>>> because null cannot be assigned to boolean:
>>>
>>>   List list = null;
>>>   boolean b = list?.isEmpty();
>>>
>>
>> That would be a compile-time error because of the incompatibility
>> between null and boolean.
>>
> The intention is that you can write a combination to handle this with
> the submitted Coin proposal:
>
> List list = null;
> boolean b = list?.isEmpty() ?: true;
>
> Stephen
>

I don't understand how that combination is supposed to work, given  
this part of the proposal:

"A null-safe method invocation expression e1?.name(args) ... the type  
of the result is the same as the type of e1.name(args).  It is an  
error if this is not a reference type."

Doesn't that mean that the compiler should reject the expression  
'list?.isEmpty()' ?


Mark



From neal at gafter.com  Sun Apr  5 07:11:33 2009
From: neal at gafter.com (Neal Gafter)
Date: Sun, 5 Apr 2009 07:11:33 -0700
Subject: Proposal: Elvis and Other Null-Safe Operators
In-Reply-To: <84A9B0E6-9454-4A74-AFF1-BE92D6694D05@googlemail.com>
References: <49C201C5.3090200@gmail.com>
	<15e8b9d20903190713i67595fe1hac45db43e4dc522c@mail.gmail.com>
	<49C27E68.7020709@gmail.com>
	<84A9B0E6-9454-4A74-AFF1-BE92D6694D05@googlemail.com>
Message-ID: <15e8b9d20904050711o124b388etca7847f8a456a45c@mail.gmail.com>

On Sun, Apr 5, 2009 at 4:40 AM, Mark Mahieu <markmahieu at googlemail.com> wrote:
>> List list = null;
>> boolean b = list?.isEmpty() ?: true;
>>
>> Stephen
>>
>
> I don't understand how that combination is supposed to work, given
> this part of the proposal:
>
> "A null-safe method invocation expression e1?.name(args) ... the type
> of the result is the same as the type of e1.name(args). ?It is an
> error if this is not a reference type."
>
> Doesn't that mean that the compiler should reject the expression
> 'list?.isEmpty()' ?

Given the spec as written, yes.  However, it could be changed so that
the result is the same as the result of the rewriting in the
"compilation" section of the spec.  In that case its result would be
Boolean.  However, that is likely to result in more runtime null
errors, not fewer, if people do things like

if (list?.isEmpty()) ...

-Neal


From markmahieu at googlemail.com  Sun Apr  5 10:19:52 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Sun, 5 Apr 2009 18:19:52 +0100
Subject: Proposal: Elvis and Other Null-Safe Operators
In-Reply-To: <15e8b9d20904050711o124b388etca7847f8a456a45c@mail.gmail.com>
References: <49C201C5.3090200@gmail.com>
	<15e8b9d20903190713i67595fe1hac45db43e4dc522c@mail.gmail.com>
	<49C27E68.7020709@gmail.com>
	<84A9B0E6-9454-4A74-AFF1-BE92D6694D05@googlemail.com>
	<15e8b9d20904050711o124b388etca7847f8a456a45c@mail.gmail.com>
Message-ID: <cf90c1f10904051019y73531b3cga714eaca16062a7e@mail.gmail.com>

2009/4/5 Neal Gafter <neal at gafter.com>

> On Sun, Apr 5, 2009 at 4:40 AM, Mark Mahieu <markmahieu at googlemail.com>
> wrote:
> > Doesn't that mean that the compiler should reject the expression
> > 'list?.isEmpty()' ?
>
> Given the spec as written, yes.  However, it could be changed so that
> the result is the same as the result of the rewriting in the
> "compilation" section of the spec.  In that case its result would be
> Boolean.  However, that is likely to result in more runtime null
> errors, not fewer, if people do things like
>
> if (list?.isEmpty()) ...
>
> -Neal
>

Thanks, Neal.

I've started putting a rough implementation of this proposal together, just
to aid my own understanding.  Are you or Stephen (or anyone else) intending
to produce a prototype, or would it be useful if I polish up what I've been
doing?

Mark


From neal at gafter.com  Sun Apr  5 10:52:55 2009
From: neal at gafter.com (Neal Gafter)
Date: Sun, 5 Apr 2009 10:52:55 -0700
Subject: Proposal: Elvis and Other Null-Safe Operators
In-Reply-To: <cf90c1f10904051019y73531b3cga714eaca16062a7e@mail.gmail.com>
References: <49C201C5.3090200@gmail.com>
	<15e8b9d20903190713i67595fe1hac45db43e4dc522c@mail.gmail.com>
	<49C27E68.7020709@gmail.com>
	<84A9B0E6-9454-4A74-AFF1-BE92D6694D05@googlemail.com>
	<15e8b9d20904050711o124b388etca7847f8a456a45c@mail.gmail.com>
	<cf90c1f10904051019y73531b3cga714eaca16062a7e@mail.gmail.com>
Message-ID: <15e8b9d20904051052q530820e5m9fcb3441c8cb59d3@mail.gmail.com>

On Sun, Apr 5, 2009 at 10:19 AM, Mark Mahieu <markmahieu at googlemail.com> wrote:
> I've started putting a rough implementation of this proposal together, just
> to aid my own understanding. ?Are you or Stephen (or anyone else) intending
> to produce a prototype, or would it be useful if I polish up what I've been
> doing?

I'm not planning to prototype this.


From jodastephen at gmail.com  Sun Apr  5 05:11:57 2009
From: jodastephen at gmail.com (Stephen Colebourne)
Date: Sun, 05 Apr 2009 13:11:57 +0100
Subject: Proposal: Elvis and Other Null-Safe Operators
In-Reply-To: <84A9B0E6-9454-4A74-AFF1-BE92D6694D05@googlemail.com>
References: <49C201C5.3090200@gmail.com>
	<15e8b9d20903190713i67595fe1hac45db43e4dc522c@mail.gmail.com>
	<49C27E68.7020709@gmail.com>
	<84A9B0E6-9454-4A74-AFF1-BE92D6694D05@googlemail.com>
Message-ID: <49D8A00D.7040909@gmail.com>


Mark Mahieu wrote:
>>
>> List list = null;
>> boolean b = list?.isEmpty() ?: true;
>>
>> Stephen
>>
>
> I don't understand how that combination is supposed to work, given 
> this part of the proposal:
>
> "A null-safe method invocation expression e1?.name(args) ... the type 
> of the result is the same as the type of e1.name(args).  It is an 
> error if this is not a reference type."
>
> Doesn't that mean that the compiler should reject the expression 
> 'list?.isEmpty()' ?
I hope Neal can comment as he wrote up the details of the proposal. I 
did ask him about this when I first read it, and he replied that 
primitives were handled in the "boxedValue ?: primitive" case. At the 
time, I assumed that meant that the "list?.isEmpty() ?: false" was also 
handled, but on re-reading today, you may be right.

I'd like the "list?.isEmpty() ?: false" to be handled though.

Stephen



From stephen at joda.org  Sun Apr  5 11:07:51 2009
From: stephen at joda.org (Stephen C)
Date: Sun, 05 Apr 2009 19:07:51 +0100
Subject: Proposal: Elvis and Other Null-Safe Operators
In-Reply-To: <cf90c1f10904051019y73531b3cga714eaca16062a7e@mail.gmail.com>
References: <49C201C5.3090200@gmail.com>	
	<15e8b9d20903190713i67595fe1hac45db43e4dc522c@mail.gmail.com>	
	<49C27E68.7020709@gmail.com>	
	<84A9B0E6-9454-4A74-AFF1-BE92D6694D05@googlemail.com>	
	<15e8b9d20904050711o124b388etca7847f8a456a45c@mail.gmail.com>
	<cf90c1f10904051019y73531b3cga714eaca16062a7e@mail.gmail.com>
Message-ID: <49D8F377.4080308@joda.org>

Mark Mahieu wrote:
> I've started putting a rough implementation of this proposal together, 
> just to aid my own understanding.  Are you or Stephen (or anyone else) 
> intending to produce a prototype, or would it be useful if I polish up 
> what I've been doing?
I haven't got time to do so, thus it would be great if you do some 
polishing.
Stephen



From markmahieu at googlemail.com  Sun Apr  5 23:05:24 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Mon, 6 Apr 2009 07:05:24 +0100
Subject: Proposal: Elvis and Other Null-Safe Operators
In-Reply-To: <49D8F377.4080308@joda.org>
References: <49C201C5.3090200@gmail.com>
	<15e8b9d20903190713i67595fe1hac45db43e4dc522c@mail.gmail.com>
	<49C27E68.7020709@gmail.com>
	<84A9B0E6-9454-4A74-AFF1-BE92D6694D05@googlemail.com>
	<15e8b9d20904050711o124b388etca7847f8a456a45c@mail.gmail.com>
	<cf90c1f10904051019y73531b3cga714eaca16062a7e@mail.gmail.com>
	<49D8F377.4080308@joda.org>
Message-ID: <cf90c1f10904052305n49582133ub6dda409e07dff9d@mail.gmail.com>

2009/4/5 Stephen C <stephen at joda.org>

> Mark Mahieu wrote:
> > I've started putting a rough implementation of this proposal together,
> > just to aid my own understanding.  Are you or Stephen (or anyone else)
> > intending to produce a prototype, or would it be useful if I polish up
> > what I've been doing?
> I haven't got time to do so, thus it would be great if you do some
> polishing.
> Stephen
>

OK, will do.
Mark


From alexandre.makarenko at free.fr  Mon Apr  6 14:25:23 2009
From: alexandre.makarenko at free.fr (alex)
Date: Mon, 6 Apr 2009 23:25:23 +0200
Subject: Proposal: Type inference for variable definition/initialization
	using the 'auto' keyword.
In-Reply-To: <e07797830903280135x36f85116y6336e0973b5641b8@mail.gmail.com>
References: <e07797830903280135x36f85116y6336e0973b5641b8@mail.gmail.com>
Message-ID: <200904062325.23836.alexandre.makarenko@free.fr>

Hi Tim,
a little bit late comment...

what if 

Map<String, List<String>> anagrams();

compiled as

Map<String, List<String>> anagrams = new HashMap<String, List<String>>();

?



In more general way for a class C

C c( constructor-args );

would be equivalent to

C c = new C( constructor-args );

@lex

ps: C++ trick ;-)


On Saturday 28 March 2009 09:35:46 Tim Lebedkov wrote:
> Type inference for variable definition/initialization using the 'auto'
> keyword.
>
> AUTHOR(S): Tim Lebedkov
>
> OVERVIEW
>
> Provide a two sentence or shorter description of these five aspects of
> the feature:
>
> FEATURE SUMMARY: Should be suitable as a summary in a language tutorial.
>
> This proposal addresses the addition of type inference for
> variable definitions to the Java programming language using the 'auto'
> keyword instead of specific type name.
>
> For example, consider the following assignment statement:
>
> Map<String, List<String>> anagrams = new HashMap<String, List<String>>();
>
> This is rather lengthy, so it can be replaced with this:
>
> auto anagrams = new HashMap<String, List<String>>();
>
> and anagrams is automatically typed as HashMap<String, List<String>>
>
> MAJOR ADVANTAGE: What makes the proposal a favorable change?
>
> Generics have had a tremendously positive impact on type safety in the
> Java programming language. They  have made it possible to provide
> static guarantees about the type of instances used by other classes,
> preventing entire classes of runtime errors from occurring. However,
> generics have added complexity to Java, making the code far more
> verbose and occasionally difficult to read. Although solving this
> problem is well outside the scope of this proposal, a limited form of
> type inference would remove unnecessary redundancy from the language.
> Even without generics it seems unnecessary to duplicate type names for
> simple variable definitions/assignments like:
>
> Integer a = new Integer(1023);
>
> MAJOR BENEFIT: Why is the platform better if the proposal is adopted?
>
> Less code and no duplication has a positive impact on many things:
> - faster typing/faster code changes
> - easier code changing without IDE assistance
> - code versioning diffs are more clear
>
> MAJOR DISADVANTAGE: There is always a cost.
>
> - it could be harder to read the code.
> - auto will be a keyword and may break some old code
>
> ALTERNATIVES: Can the benefits and advantages be had some way without
> a language change?
>
> no
>
> EXAMPLES
>
> SIMPLE EXAMPLE: Show the simplest possible program utilizing the new
> feature.
>
> 1. simple assignment
>
> Map<String, List<String>> a = new HashMap<String, List<String>>();
>
> becomes
>
> auto a = new HashMap<String, List<String>>();
>
> 2. auto in for
>
> List<String> list = ...
> for (auto s: list)
>     ...
>
> 3. auto for a final variable
>
> final ArrayList<String> list = new ArrayList<String>();
>
> becomes
>
> final auto list = new ArrayList<String>();
>
> 4. class field definition
>
> class A {
>     String a = "";
> }
>
> becomes
>
> class A {
>     auto a = "";
> }
>
> ADVANCED EXAMPLE: Show advanced usage(s) of the feature.
>
> auto i = 5 + 3;  // same as "int i = 5 + 3"
> auto i = 5 + 3L;  // same as "long i = 5 + 3L"
> for (auto entry : (new HashMap<Integer, String>>).entrySet()) { }
>
> DETAILS
>
> SPECIFICATION: Describe how the proposal affects the grammar, type
> system, and meaning of expressions and statements in the Java
> Programming Language as well as any other known impacts.
>
> Informally, the specification adds syntax to replace the type definition
> in variable definitions with assignments by 'auto'. The type of the
> variable is automatically determined.
>
> COMPILATION: How would the feature be compiled to class files? Show
> how the simple and advanced examples would be compiled. Compilation
> can be expressed as at least one of a desugaring to existing source
> constructs and a translation down to bytecode. If a new bytecode is
> used or the semantics of an existing bytecode are changed, describe
> those changes, including how they impact verification. Also discuss
> any new class file attributes that are introduced. Note that there are
> many downstream tools that consume class files and that they may to be
> updated to support the proposal!
>
> The resulting bytecode would be identical to bytecode generated by the
> same code with the types inferred.
>
> TESTING: How can the feature be tested?
>
> The proposed construct can be tested by writing a number of statements
> that construct instances using
> inferred types. These instances can then be assigned to variables and
> fields of specific types, and passed to
> methods that expect specific types. These tests should compile and run
> as expected:
> auto set = new SortedSet<String>();
> set.add("A");
> set.add("B");
> set.add("C");
> // verify that set contains "A", "B", "C".
>
> LIBRARY SUPPORT: Are any supporting libraries needed for the feature?
>
> No library support is required, although libraries can be rewritten to
> take advantage of the new feature.
>
> REFLECTIVE APIS: Do any of the various and sundry reflection APIs need
> to be updated? This list of reflective APIs includes but is not
> limited to core reflection (java.lang.Class and java.lang.reflect.*),
> javax.lang.model.*, the doclet API, and JPDA.
>
> No reflective APIs need to be changed.
>
> OTHER CHANGES: Do any other parts of the platform need be updated too?
> Possibilities include but are not limited to JNI, serialization, and
> output of the javadoc tool.
>
> No other parts of the platform need to be updated.
>
> MIGRATION: Sketch how a code base could be converted, manually or
> automatically, to use the new feature.
>
> Libraries can be rewritten to take advantage of this feature, but it
> is not imperative that they do so.
>
> COMPATIBILITY
>
> This change is backwards incompatible on the source code level.
>
> BREAKING CHANGES: Are any previously valid programs now invalid? If
> so, list one.
>
> All programs that use auto as a name for an identifier would become
> invalid.
>
> EXISTING PROGRAMS: How do source and class files of earlier platform
> versions interact with the feature? Can any new overloadings occur?
> Can any new overriding occur?
>
> The feature is completely transparent to the class files. Class files
> do not contain
> any information about the variables declared using 'auto'.
>
> REFERENCES
>
> [1] Thanks to Jeremy Manson (his proposal served as a template for this
> one)
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-February/000009.html
> [2] Jaako Jarvi and Bjarne Stroustrup. Decltype and auto (revision 3).
> Paper N1607,
> JTC1-SC22/WG21, February 17 2004. Online: http://www.open-std.org/jtc1/
> sc22/wg21/docs/papers/2004/n1607.pdf; same as ANSI NCITS/J16 04-0047.
> [3] James Gosling, Bill Joy, Guy Steele, and Gilad Bracha. The Java
> Language Specification, 3rd Edition.
> Addison Wesley, 2004.
>
>
> EXISTING BUGS: Please include a list of any existing Sun bug ids
> related to this proposal.
> 6242254, 4983159, 6368076
>
> URL FOR PROTOTYPE (optional):
> none



From mthornton at optrak.co.uk  Mon Apr  6 14:31:32 2009
From: mthornton at optrak.co.uk (Mark Thornton)
Date: Mon, 06 Apr 2009 22:31:32 +0100
Subject: Proposal: Type inference for variable definition/initialization
	using the 'auto' keyword.
In-Reply-To: <200904062325.23836.alexandre.makarenko@free.fr>
References: <e07797830903280135x36f85116y6336e0973b5641b8@mail.gmail.com>
	<200904062325.23836.alexandre.makarenko@free.fr>
Message-ID: <49DA74B4.5080304@optrak.co.uk>

alex wrote:
> Hi Tim,
> a little bit late comment...
>
> what if 
>
> Map<String, List<String>> anagrams();
>
> compiled as
>
> Map<String, List<String>> anagrams = new HashMap<String, List<String>>();
>
>   
Why HashMap and not some other implementation of Map? That approach only 
works if the LHS specifies a concrete type and not an interface or 
abstract class.

Mark Thornton



From rssh at gradsoft.com.ua  Mon Apr  6 17:33:12 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Tue, 7 Apr 2009 03:33:12 +0300 (EEST)
Subject: scripts and results (was Helping to find the usefulness of a 
	proposal)
Message-ID: <60287e9e1530b3e1ae49976316e8dc57.squirrel@wmail.gradsoft.ua>


 Good day,

Few days ago Stephan give idea about writing simple script, which
 count amount of possible-optimizations of existing code.

So, I wrote few checks for some of such entries. They count
low bound of number of code patterns, which can be optimized with
some of coin proposal and situated on distinct source lines.

I'm afraid that information, which come from count of such code patterns
can give incorrect direction:  when we have such patterns in code,
it's means that problem is not so big and we can easy live with one.
 Big language problems solved (or not) in non-trivial way, when we have no
common (may be ugly) workaround.
For example. in Java we rare will see BigDecimal.add()  because it is not
easy to work with BigDecimals, instead people work with double and have
troubles
with floating points rounding issues (see
http://www.ddj.com/java/184405721)).
Yet one example - choosing another language for implementing db-intensive
parts of projects.

Ok, you warned;  data still can be interesting:

Checked patterns was:
  string in switch
  instanceof switch
  byte literals
  multi catch
  loop by iterator, with call remove inside loop

 (if you want include other checks, you can add one at
 etc/checkers_coin.def or ask me [but without any warranty])

<BTW>
Exists one proposal, which I can't find on Joe blog: is change of variable
subtype inside 'if instance' statement
I. e. patterns look:
if (x instanceof something)
{
 something sx = (something)x;
}
And proposal tell type 'x' as 'something' inside dominate if block.
Are anybody remember such proposal or it's was my fantasy ?
</BTW>

Some results:

For jetty6_11: (web server)
byte literal    :       52
elvis   :       43
instanceof switch       :       8
loop with remove        :       0
multi catch     :       22
string in switch        :       19
Files:187

For gwt-user (google ajax library)
byte literal    :       2
elvis   :       30
instanceof switch       :       6
loop with remove        :       5
multi catch     :       9
string in switch        :       10
Files:920

For openjdk-jdk part: (system library)
byte literal    :       1245
elvis   :       725
instanceof switch       :       252
loop with remove        :       61
multi catch     :       349
string in switch        :       380
Files:7375



If you want to play with checks - most easy way is get special modified
source
distributive of JavaChecker, which I published as 2.5.0p0 and run it, i.e.
(assuming you on Unix console)

retrive distributive:

 wget
http://datacenter.gradsoft.ua/public.repository/ua.gradsoft/javachecker/installations/JavaCheckerSourceInstaller-2.5.0p0.jar

run installer:
java -jar JavaCheckerSourceInstaller-2.5.0p0.jar
 (install one from UI)

cd <where-you-install-javacheker>

vi build-check-external.xml, look at few last tasks at end

vi check-external.properties

add own task and run one, as example:
ant -f build-check-external.xml check-coin-openjdk

Note, that speed of JavaChecker is far from ideal: openJDK-jdk
 processed near 50 minutes, so be patient ;)

Hope, this information can be useful, as one (and not main) of  sources.

Regards !




From reinier at zwitserloot.com  Mon Apr  6 17:37:18 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Tue, 7 Apr 2009 02:37:18 +0200
Subject: Proposal: Type inference for variable definition/initialization
	using the 'auto' keyword.
In-Reply-To: <49DA74B4.5080304@optrak.co.uk>
References: <e07797830903280135x36f85116y6336e0973b5641b8@mail.gmail.com>
	<200904062325.23836.alexandre.makarenko@free.fr>
	<49DA74B4.5080304@optrak.co.uk>
Message-ID: <30B1D532-AA2B-4D1E-A8AC-700D54C05CA5@zwitserloot.com>

Also,

> Map<String, List<String>> anagrams();

Actually looks like a method declaration (in fact, it is  
indistinguishable from it!), so the syntax needs work.

  --Reinier Zwitserloot
Like it? Tip it!
http://tipit.to



On Apr 6, 2009, at 23:31, Mark Thornton wrote:

> alex wrote:
>> Hi Tim,
>> a little bit late comment...
>>
>> what if
>>
>> Map<String, List<String>> anagrams();
>>
>> compiled as
>>
>> Map<String, List<String>> anagrams = new HashMap<String,  
>> List<String>>();
>>
>>
> Why HashMap and not some other implementation of Map? That approach  
> only
> works if the LHS specifies a concrete type and not an interface or
> abstract class.
>
> Mark Thornton
>
>



From brucechapman at paradise.net.nz  Tue Apr  7 01:22:27 2009
From: brucechapman at paradise.net.nz (Bruce Chapman)
Date: Tue, 07 Apr 2009 20:22:27 +1200
Subject: scripts and results (was Helping to find the usefulness of a
	proposal)
In-Reply-To: <60287e9e1530b3e1ae49976316e8dc57.squirrel@wmail.gradsoft.ua>
References: <60287e9e1530b3e1ae49976316e8dc57.squirrel@wmail.gradsoft.ua>
Message-ID: <49DB0D43.1050605@paradise.net.nz>

Ruslan,

Thanks for doing that.

Bruce

P.S. One answer below



Ruslan Shevchenko wrote:
>  Good day,
>
> Few days ago Stephan give idea about writing simple script, which
>  count amount of possible-optimizations of existing code.
>
>   
- SNIP -

> <BTW>
> Exists one proposal, which I can't find on Joe blog: is change of variable
> subtype inside 'if instance' statement
> I. e. patterns look:
> if (x instanceof something)
> {
>  something sx = (something)x;
> }
> And proposal tell type 'x' as 'something' inside dominate if block.
> Are anybody remember such proposal or it's was my fantasy ?
> </BTW>
>
>
>   
This is part of the functionality of the switch instanceof proposal, the 
desugaring probably has something that looks like that in it, and I 
mentioned it in one of my comments regarding that proposal.

Bruce



From tim.lebedkov at googlemail.com  Tue Apr  7 09:52:29 2009
From: tim.lebedkov at googlemail.com (Tim Lebedkov)
Date: Tue, 7 Apr 2009 18:52:29 +0200
Subject: Proposal: Type inference for variable definition/initialization 
	using the 'auto' keyword.
In-Reply-To: <200904062325.23836.alexandre.makarenko@free.fr>
References: <e07797830903280135x36f85116y6336e0973b5641b8@mail.gmail.com>
	<200904062325.23836.alexandre.makarenko@free.fr>
Message-ID: <e07797830904070952h23521966t5ecd403984b8febc@mail.gmail.com>

Hello Alex,

yes, C++ has a lot of interesting syntax. It is one of Java "parents"
and very similar/compatible to Java. IMHO it is always worth a look at
how something is implemented there. By the way, C++0x will have both
features: "auto" and "definition=initialization". This is probably
because you can write something like:

auto birthday = user.getBirthday(); // no constructor call and no type name here

Regards
--Tim

On Mon, Apr 6, 2009 at 11:25 PM, alex <alexandre.makarenko at free.fr> wrote:
> Hi Tim,
> a little bit late comment...
>
> what if
>
> Map<String, List<String>> anagrams();
>
> compiled as
>
> Map<String, List<String>> anagrams = new HashMap<String, List<String>>();
>
> ?
>
>
>
> In more general way for a class C
>
> C c( constructor-args );
>
> would be equivalent to
>
> C c = new C( constructor-args );
>
> @lex
>
> ps: C++ trick ;-)
>
>
> On Saturday 28 March 2009 09:35:46 Tim Lebedkov wrote:
>> Type inference for variable definition/initialization using the 'auto'
>> keyword.
>>
>> AUTHOR(S): Tim Lebedkov
>>
>> OVERVIEW
>>
>> Provide a two sentence or shorter description of these five aspects of
>> the feature:
>>
>> FEATURE SUMMARY: Should be suitable as a summary in a language tutorial.
>>
>> This proposal addresses the addition of type inference for
>> variable definitions to the Java programming language using the 'auto'
>> keyword instead of specific type name.
>>
>> For example, consider the following assignment statement:
>>
>> Map<String, List<String>> anagrams = new HashMap<String, List<String>>();
>>
>> This is rather lengthy, so it can be replaced with this:
>>
>> auto anagrams = new HashMap<String, List<String>>();
>>
>> and anagrams is automatically typed as HashMap<String, List<String>>
>>
>> MAJOR ADVANTAGE: What makes the proposal a favorable change?
>>
>> Generics have had a tremendously positive impact on type safety in the
>> Java programming language. They ?have made it possible to provide
>> static guarantees about the type of instances used by other classes,
>> preventing entire classes of runtime errors from occurring. However,
>> generics have added complexity to Java, making the code far more
>> verbose and occasionally difficult to read. Although solving this
>> problem is well outside the scope of this proposal, a limited form of
>> type inference would remove unnecessary redundancy from the language.
>> Even without generics it seems unnecessary to duplicate type names for
>> simple variable definitions/assignments like:
>>
>> Integer a = new Integer(1023);
>>
>> MAJOR BENEFIT: Why is the platform better if the proposal is adopted?
>>
>> Less code and no duplication has a positive impact on many things:
>> - faster typing/faster code changes
>> - easier code changing without IDE assistance
>> - code versioning diffs are more clear
>>
>> MAJOR DISADVANTAGE: There is always a cost.
>>
>> - it could be harder to read the code.
>> - auto will be a keyword and may break some old code
>>
>> ALTERNATIVES: Can the benefits and advantages be had some way without
>> a language change?
>>
>> no
>>
>> EXAMPLES
>>
>> SIMPLE EXAMPLE: Show the simplest possible program utilizing the new
>> feature.
>>
>> 1. simple assignment
>>
>> Map<String, List<String>> a = new HashMap<String, List<String>>();
>>
>> becomes
>>
>> auto a = new HashMap<String, List<String>>();
>>
>> 2. auto in for
>>
>> List<String> list = ...
>> for (auto s: list)
>> ? ? ...
>>
>> 3. auto for a final variable
>>
>> final ArrayList<String> list = new ArrayList<String>();
>>
>> becomes
>>
>> final auto list = new ArrayList<String>();
>>
>> 4. class field definition
>>
>> class A {
>> ? ? String a = "";
>> }
>>
>> becomes
>>
>> class A {
>> ? ? auto a = "";
>> }
>>
>> ADVANCED EXAMPLE: Show advanced usage(s) of the feature.
>>
>> auto i = 5 + 3; ?// same as "int i = 5 + 3"
>> auto i = 5 + 3L; ?// same as "long i = 5 + 3L"
>> for (auto entry : (new HashMap<Integer, String>>).entrySet()) { }
>>
>> DETAILS
>>
>> SPECIFICATION: Describe how the proposal affects the grammar, type
>> system, and meaning of expressions and statements in the Java
>> Programming Language as well as any other known impacts.
>>
>> Informally, the specification adds syntax to replace the type definition
>> in variable definitions with assignments by 'auto'. The type of the
>> variable is automatically determined.
>>
>> COMPILATION: How would the feature be compiled to class files? Show
>> how the simple and advanced examples would be compiled. Compilation
>> can be expressed as at least one of a desugaring to existing source
>> constructs and a translation down to bytecode. If a new bytecode is
>> used or the semantics of an existing bytecode are changed, describe
>> those changes, including how they impact verification. Also discuss
>> any new class file attributes that are introduced. Note that there are
>> many downstream tools that consume class files and that they may to be
>> updated to support the proposal!
>>
>> The resulting bytecode would be identical to bytecode generated by the
>> same code with the types inferred.
>>
>> TESTING: How can the feature be tested?
>>
>> The proposed construct can be tested by writing a number of statements
>> that construct instances using
>> inferred types. These instances can then be assigned to variables and
>> fields of specific types, and passed to
>> methods that expect specific types. These tests should compile and run
>> as expected:
>> auto set = new SortedSet<String>();
>> set.add("A");
>> set.add("B");
>> set.add("C");
>> // verify that set contains "A", "B", "C".
>>
>> LIBRARY SUPPORT: Are any supporting libraries needed for the feature?
>>
>> No library support is required, although libraries can be rewritten to
>> take advantage of the new feature.
>>
>> REFLECTIVE APIS: Do any of the various and sundry reflection APIs need
>> to be updated? This list of reflective APIs includes but is not
>> limited to core reflection (java.lang.Class and java.lang.reflect.*),
>> javax.lang.model.*, the doclet API, and JPDA.
>>
>> No reflective APIs need to be changed.
>>
>> OTHER CHANGES: Do any other parts of the platform need be updated too?
>> Possibilities include but are not limited to JNI, serialization, and
>> output of the javadoc tool.
>>
>> No other parts of the platform need to be updated.
>>
>> MIGRATION: Sketch how a code base could be converted, manually or
>> automatically, to use the new feature.
>>
>> Libraries can be rewritten to take advantage of this feature, but it
>> is not imperative that they do so.
>>
>> COMPATIBILITY
>>
>> This change is backwards incompatible on the source code level.
>>
>> BREAKING CHANGES: Are any previously valid programs now invalid? If
>> so, list one.
>>
>> All programs that use auto as a name for an identifier would become
>> invalid.
>>
>> EXISTING PROGRAMS: How do source and class files of earlier platform
>> versions interact with the feature? Can any new overloadings occur?
>> Can any new overriding occur?
>>
>> The feature is completely transparent to the class files. Class files
>> do not contain
>> any information about the variables declared using 'auto'.
>>
>> REFERENCES
>>
>> [1] Thanks to Jeremy Manson (his proposal served as a template for this
>> one)
>> http://mail.openjdk.java.net/pipermail/coin-dev/2009-February/000009.html
>> [2] Jaako Jarvi and Bjarne Stroustrup. Decltype and auto (revision 3).
>> Paper N1607,
>> JTC1-SC22/WG21, February 17 2004. Online: http://www.open-std.org/jtc1/
>> sc22/wg21/docs/papers/2004/n1607.pdf; same as ANSI NCITS/J16 04-0047.
>> [3] James Gosling, Bill Joy, Guy Steele, and Gilad Bracha. The Java
>> Language Specification, 3rd Edition.
>> Addison Wesley, 2004.
>>
>>
>> EXISTING BUGS: Please include a list of any existing Sun bug ids
>> related to this proposal.
>> 6242254, 4983159, 6368076
>>
>> URL FOR PROTOTYPE (optional):
>> none
>
>


From alexandre.makarenko at free.fr  Tue Apr  7 11:57:15 2009
From: alexandre.makarenko at free.fr (alexandre.makarenko at free.fr)
Date: Tue, 7 Apr 2009 20:57:15 +0200 (CEST)
Subject: Proposal: Type inference for variable definition/initialization
	using the 'auto' keyword.
In-Reply-To: <49DA74B4.5080304@optrak.co.uk>
Message-ID: <32658616.5264011239130635849.JavaMail.root@spooler2-g27.priv.proxad.net>

exactly ;-)

----- Original Message -----
From: "Mark Thornton" <mthornton at optrak.co.uk>
To: "alex" <alexandre.makarenko at free.fr>
Cc: "Tim Lebedkov" <tim.lebedkov at googlemail.com>, coin-dev at openjdk.java.net
Sent: Monday, April 6, 2009 11:31:32 PM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
Subject: Re: Proposal: Type inference for variable definition/initialization using the 'auto' keyword.

alex wrote:
> Hi Tim,
> a little bit late comment...
>
> what if 
>
> Map<String, List<String>> anagrams();
>
> compiled as
>
> Map<String, List<String>> anagrams = new HashMap<String, List<String>>();
>
>   
Why HashMap and not some other implementation of Map? That approach only 
works if the LHS specifies a concrete type and not an interface or 
abstract class.

Mark Thornton



From alexandre.makarenko at free.fr  Tue Apr  7 12:00:49 2009
From: alexandre.makarenko at free.fr (alexandre.makarenko at free.fr)
Date: Tue, 7 Apr 2009 21:00:49 +0200 (CEST)
Subject: Proposal: Type inference for variable definition/initialization
	using the 'auto' keyword.
In-Reply-To: <30B1D532-AA2B-4D1E-A8AC-700D54C05CA5@zwitserloot.com>
Message-ID: <20015364.5264851239130849035.JavaMail.root@spooler2-g27.priv.proxad.net>

method ?

it lacks the method body (or abstract or native modifier)

alex


----- Original Message -----
From: "Reinier Zwitserloot" <reinier at zwitserloot.com>
To: coin-dev at openjdk.java.net
Sent: Tuesday, April 7, 2009 2:37:18 AM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
Subject: Re: Proposal: Type inference for variable definition/initialization using the 'auto' keyword.

Also,

> Map<String, List<String>> anagrams();

Actually looks like a method declaration (in fact, it is  
indistinguishable from it!), so the syntax needs work.

  --Reinier Zwitserloot
Like it? Tip it!
http://tipit.to



On Apr 6, 2009, at 23:31, Mark Thornton wrote:

> alex wrote:
>> Hi Tim,
>> a little bit late comment...
>>
>> what if
>>
>> Map<String, List<String>> anagrams();
>>
>> compiled as
>>
>> Map<String, List<String>> anagrams = new HashMap<String,  
>> List<String>>();
>>
>>
> Why HashMap and not some other implementation of Map? That approach  
> only
> works if the LHS specifies a concrete type and not an interface or
> abstract class.
>
> Mark Thornton
>
>




From alexandre.makarenko at free.fr  Tue Apr  7 12:02:36 2009
From: alexandre.makarenko at free.fr (alexandre.makarenko at free.fr)
Date: Tue, 7 Apr 2009 21:02:36 +0200 (CEST)
Subject: Proposal: Type inference for variable definition/initialization
	using the 'auto' keyword.
In-Reply-To: <e07797830904070952h23521966t5ecd403984b8febc@mail.gmail.com>
Message-ID: <28935064.5265151239130956325.JavaMail.root@spooler2-g27.priv.proxad.net>


sounds great !

----- Original Message -----
From: "Tim Lebedkov" <tim.lebedkov at googlemail.com>
To: "alex" <alexandre.makarenko at free.fr>
Cc: coin-dev at openjdk.java.net
Sent: Tuesday, April 7, 2009 6:52:29 PM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
Subject: Re: Proposal: Type inference for variable definition/initialization  using the 'auto' keyword.

Hello Alex,

yes, C++ has a lot of interesting syntax. It is one of Java "parents"
and very similar/compatible to Java. IMHO it is always worth a look at
how something is implemented there. By the way, C++0x will have both
features: "auto" and "definition=initialization". This is probably
because you can write something like:

auto birthday = user.getBirthday(); // no constructor call and no type name here

Regards
--Tim

On Mon, Apr 6, 2009 at 11:25 PM, alex <alexandre.makarenko at free.fr> wrote:
> Hi Tim,
> a little bit late comment...
>
> what if
>
> Map<String, List<String>> anagrams();
>
> compiled as
>
> Map<String, List<String>> anagrams = new HashMap<String, List<String>>();
>
> ?
>
>
>
> In more general way for a class C
>
> C c( constructor-args );
>
> would be equivalent to
>
> C c = new C( constructor-args );
>
> @lex
>
> ps: C++ trick ;-)
>
>
> On Saturday 28 March 2009 09:35:46 Tim Lebedkov wrote:
>> Type inference for variable definition/initialization using the 'auto'
>> keyword.
>>
>> AUTHOR(S): Tim Lebedkov
>>
>> OVERVIEW
>>
>> Provide a two sentence or shorter description of these five aspects of
>> the feature:
>>
>> FEATURE SUMMARY: Should be suitable as a summary in a language tutorial.
>>
>> This proposal addresses the addition of type inference for
>> variable definitions to the Java programming language using the 'auto'
>> keyword instead of specific type name.
>>
>> For example, consider the following assignment statement:
>>
>> Map<String, List<String>> anagrams = new HashMap<String, List<String>>();
>>
>> This is rather lengthy, so it can be replaced with this:
>>
>> auto anagrams = new HashMap<String, List<String>>();
>>
>> and anagrams is automatically typed as HashMap<String, List<String>>
>>
>> MAJOR ADVANTAGE: What makes the proposal a favorable change?
>>
>> Generics have had a tremendously positive impact on type safety in the
>> Java programming language. They ?have made it possible to provide
>> static guarantees about the type of instances used by other classes,
>> preventing entire classes of runtime errors from occurring. However,
>> generics have added complexity to Java, making the code far more
>> verbose and occasionally difficult to read. Although solving this
>> problem is well outside the scope of this proposal, a limited form of
>> type inference would remove unnecessary redundancy from the language.
>> Even without generics it seems unnecessary to duplicate type names for
>> simple variable definitions/assignments like:
>>
>> Integer a = new Integer(1023);
>>
>> MAJOR BENEFIT: Why is the platform better if the proposal is adopted?
>>
>> Less code and no duplication has a positive impact on many things:
>> - faster typing/faster code changes
>> - easier code changing without IDE assistance
>> - code versioning diffs are more clear
>>
>> MAJOR DISADVANTAGE: There is always a cost.
>>
>> - it could be harder to read the code.
>> - auto will be a keyword and may break some old code
>>
>> ALTERNATIVES: Can the benefits and advantages be had some way without
>> a language change?
>>
>> no
>>
>> EXAMPLES
>>
>> SIMPLE EXAMPLE: Show the simplest possible program utilizing the new
>> feature.
>>
>> 1. simple assignment
>>
>> Map<String, List<String>> a = new HashMap<String, List<String>>();
>>
>> becomes
>>
>> auto a = new HashMap<String, List<String>>();
>>
>> 2. auto in for
>>
>> List<String> list = ...
>> for (auto s: list)
>> ? ? ...
>>
>> 3. auto for a final variable
>>
>> final ArrayList<String> list = new ArrayList<String>();
>>
>> becomes
>>
>> final auto list = new ArrayList<String>();
>>
>> 4. class field definition
>>
>> class A {
>> ? ? String a = "";
>> }
>>
>> becomes
>>
>> class A {
>> ? ? auto a = "";
>> }
>>
>> ADVANCED EXAMPLE: Show advanced usage(s) of the feature.
>>
>> auto i = 5 + 3; ?// same as "int i = 5 + 3"
>> auto i = 5 + 3L; ?// same as "long i = 5 + 3L"
>> for (auto entry : (new HashMap<Integer, String>>).entrySet()) { }
>>
>> DETAILS
>>
>> SPECIFICATION: Describe how the proposal affects the grammar, type
>> system, and meaning of expressions and statements in the Java
>> Programming Language as well as any other known impacts.
>>
>> Informally, the specification adds syntax to replace the type definition
>> in variable definitions with assignments by 'auto'. The type of the
>> variable is automatically determined.
>>
>> COMPILATION: How would the feature be compiled to class files? Show
>> how the simple and advanced examples would be compiled. Compilation
>> can be expressed as at least one of a desugaring to existing source
>> constructs and a translation down to bytecode. If a new bytecode is
>> used or the semantics of an existing bytecode are changed, describe
>> those changes, including how they impact verification. Also discuss
>> any new class file attributes that are introduced. Note that there are
>> many downstream tools that consume class files and that they may to be
>> updated to support the proposal!
>>
>> The resulting bytecode would be identical to bytecode generated by the
>> same code with the types inferred.
>>
>> TESTING: How can the feature be tested?
>>
>> The proposed construct can be tested by writing a number of statements
>> that construct instances using
>> inferred types. These instances can then be assigned to variables and
>> fields of specific types, and passed to
>> methods that expect specific types. These tests should compile and run
>> as expected:
>> auto set = new SortedSet<String>();
>> set.add("A");
>> set.add("B");
>> set.add("C");
>> // verify that set contains "A", "B", "C".
>>
>> LIBRARY SUPPORT: Are any supporting libraries needed for the feature?
>>
>> No library support is required, although libraries can be rewritten to
>> take advantage of the new feature.
>>
>> REFLECTIVE APIS: Do any of the various and sundry reflection APIs need
>> to be updated? This list of reflective APIs includes but is not
>> limited to core reflection (java.lang.Class and java.lang.reflect.*),
>> javax.lang.model.*, the doclet API, and JPDA.
>>
>> No reflective APIs need to be changed.
>>
>> OTHER CHANGES: Do any other parts of the platform need be updated too?
>> Possibilities include but are not limited to JNI, serialization, and
>> output of the javadoc tool.
>>
>> No other parts of the platform need to be updated.
>>
>> MIGRATION: Sketch how a code base could be converted, manually or
>> automatically, to use the new feature.
>>
>> Libraries can be rewritten to take advantage of this feature, but it
>> is not imperative that they do so.
>>
>> COMPATIBILITY
>>
>> This change is backwards incompatible on the source code level.
>>
>> BREAKING CHANGES: Are any previously valid programs now invalid? If
>> so, list one.
>>
>> All programs that use auto as a name for an identifier would become
>> invalid.
>>
>> EXISTING PROGRAMS: How do source and class files of earlier platform
>> versions interact with the feature? Can any new overloadings occur?
>> Can any new overriding occur?
>>
>> The feature is completely transparent to the class files. Class files
>> do not contain
>> any information about the variables declared using 'auto'.
>>
>> REFERENCES
>>
>> [1] Thanks to Jeremy Manson (his proposal served as a template for this
>> one)
>> http://mail.openjdk.java.net/pipermail/coin-dev/2009-February/000009.html
>> [2] Jaako Jarvi and Bjarne Stroustrup. Decltype and auto (revision 3).
>> Paper N1607,
>> JTC1-SC22/WG21, February 17 2004. Online: http://www.open-std.org/jtc1/
>> sc22/wg21/docs/papers/2004/n1607.pdf; same as ANSI NCITS/J16 04-0047.
>> [3] James Gosling, Bill Joy, Guy Steele, and Gilad Bracha. The Java
>> Language Specification, 3rd Edition.
>> Addison Wesley, 2004.
>>
>>
>> EXISTING BUGS: Please include a list of any existing Sun bug ids
>> related to this proposal.
>> 6242254, 4983159, 6368076
>>
>> URL FOR PROTOTYPE (optional):
>> none
>
>


From reinier at zwitserloot.com  Tue Apr  7 13:45:26 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Tue, 7 Apr 2009 22:45:26 +0200
Subject: Proposal: Type inference for variable definition/initialization
	using the 'auto' keyword.
In-Reply-To: <20015364.5264851239130849035.JavaMail.root@spooler2-g27.priv.proxad.net>
References: <20015364.5264851239130849035.JavaMail.root@spooler2-g27.priv.proxad.net>
Message-ID: <514D5836-B9FA-438C-AD05-04E9B6C916AF@zwitserloot.com>

Yes, so?

The parser cannot distinguish between the two, so the only solution  
would be to amend the semantic translation of parser tokens as such:

Any method declaration that is abstract but lacks the abstract or  
native modifier is actually a field declaration with an auto- 
initialization scheme.

I'm extremely prejudiced against such hackery at the parser level.  
What if later we want to give the 'abstract' keyword meaning when it  
is used on fields? All existing tools would also have to do some  
potentially serious rewriting and refactoring in order to accomodate  
such a change.

  --Reinier Zwitserloot
Like it? Tip it!
http://tipit.to



On Apr 7, 2009, at 21:00, alexandre.makarenko at free.fr wrote:

> method ?
>
> it lacks the method body (or abstract or native modifier)
>
> alex
>
>
> ----- Original Message -----
> From: "Reinier Zwitserloot" <reinier at zwitserloot.com>
> To: coin-dev at openjdk.java.net
> Sent: Tuesday, April 7, 2009 2:37:18 AM GMT +01:00 Amsterdam /  
> Berlin / Bern / Rome / Stockholm / Vienna
> Subject: Re: Proposal: Type inference for variable definition/ 
> initialization using the 'auto' keyword.
>
> Also,
>
>> Map<String, List<String>> anagrams();
>
> Actually looks like a method declaration (in fact, it is
> indistinguishable from it!), so the syntax needs work.
>
>  --Reinier Zwitserloot
> Like it? Tip it!
> http://tipit.to
>
>
>
> On Apr 6, 2009, at 23:31, Mark Thornton wrote:
>
>> alex wrote:
>>> Hi Tim,
>>> a little bit late comment...
>>>
>>> what if
>>>
>>> Map<String, List<String>> anagrams();
>>>
>>> compiled as
>>>
>>> Map<String, List<String>> anagrams = new HashMap<String,
>>> List<String>>();
>>>
>>>
>> Why HashMap and not some other implementation of Map? That approach
>> only
>> works if the LHS specifies a concrete type and not an interface or
>> abstract class.
>>
>> Mark Thornton
>>
>>
>
>



From markmahieu at googlemail.com  Thu Apr  9 12:25:47 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Thu, 9 Apr 2009 20:25:47 +0100
Subject: Prototype: Elvis and Other Null-Safe Operators
Message-ID: <8CD6752E-879D-41BA-BB11-D5AE9F35C3F9@googlemail.com>

I've made available a prototype of Stephen Colebourne's Elvis  
proposal (based on Neal Gafter's spec), if anyone who wants to play  
around with it:

http://slm888.com/javac/elvis.html

The usual caveats apply : expect bugs, misinterpretations of the  
proposal etc.  I'll be happy to look into any bug reports, especially  
if they're accompanied by a simple test case ;)

Mark


From Joe.Darcy at Sun.COM  Thu Apr  9 14:41:12 2009
From: Joe.Darcy at Sun.COM (Joe Darcy)
Date: Thu, 09 Apr 2009 14:41:12 -0700
Subject: Prototype: Elvis and Other Null-Safe Operators
In-Reply-To: <8CD6752E-879D-41BA-BB11-D5AE9F35C3F9@googlemail.com>
References: <8CD6752E-879D-41BA-BB11-D5AE9F35C3F9@googlemail.com>
Message-ID: <49DE6B78.2040900@sun.com>

Thanks for sending in the prototype!

Which javac was the starting point?

-Joe

On 04/09/09 12:25 PM, Mark Mahieu wrote:
> I've made available a prototype of Stephen Colebourne's Elvis  
> proposal (based on Neal Gafter's spec), if anyone who wants to play  
> around with it:
>
> http://slm888.com/javac/elvis.html
>
> The usual caveats apply : expect bugs, misinterpretations of the  
> proposal etc.  I'll be happy to look into any bug reports, especially  
> if they're accompanied by a simple test case ;)
>
> Mark
>
>   



From markmahieu at googlemail.com  Thu Apr  9 14:50:04 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Thu, 9 Apr 2009 22:50:04 +0100
Subject: Prototype: Elvis and Other Null-Safe Operators
In-Reply-To: <49DE6B78.2040900@sun.com>
References: <8CD6752E-879D-41BA-BB11-D5AE9F35C3F9@googlemail.com>
	<49DE6B78.2040900@sun.com>
Message-ID: <cf90c1f10904091450g3dae03e1ra695cba8db26ef21@mail.gmail.com>

Hi Joe,
The starting point was a clone of the JDK 7 "tl" forest, as of a few days
ago.

Mark


2009/4/9 Joe Darcy <Joe.Darcy at sun.com>

> Thanks for sending in the prototype!
>
> Which javac was the starting point?
>
> -Joe
>
>
> On 04/09/09 12:25 PM, Mark Mahieu wrote:
>
>> I've made available a prototype of Stephen Colebourne's Elvis  proposal
>> (based on Neal Gafter's spec), if anyone who wants to play  around with it:
>>
>> http://slm888.com/javac/elvis.html
>>
>> The usual caveats apply : expect bugs, misinterpretations of the  proposal
>> etc.  I'll be happy to look into any bug reports, especially  if they're
>> accompanied by a simple test case ;)
>>
>> Mark
>>
>>
>>
>
>


From markmahieu at googlemail.com  Mon Apr 13 05:01:53 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Mon, 13 Apr 2009 13:01:53 +0100
Subject: Some notes on Elvis and Other Null-Safe Operators
Message-ID: <171AADE5-112F-43EB-AEED-4E502EE0914E@googlemail.com>

Below are a few observations I compiled while building and testing  
the prototype for Elvis and friends, in case they're of interest.   
They are in note form and fairly random order, so please shout if  
anything isn't clear.

Mark


--------


Elvis operator can be approximated as a library method:

         static <T> T elvis(T t1, T t2) { return t1 != null ? t1 : t2; }

In a core-libs round table recording (at http://mail.openjdk.java.net/ 
pipermail/core-libs-dev/2009-April/001406.html) the possibility of  
adding core library methods for common null-handling tasks is  
mentioned, such as throwing a standard exception if a supplied  
argument is null (presumably similar to methods in  
com.google.common.base.Preconditions).  Is it reasonable to implement  
the Elvis operator as a language change but other null-handling  
facilities as library changes?


Cannot use null-safe method invocation as a statement:

         stringBuilder?.append(?some text?);   // compiler error

     which is legal in Groovy and Fan, even for methods with void (or  
Void) result, eg. given:

         Map<Key, Runnable> map = ...

     some legal Groovy code:

         map?.get(someKey)?.run();

     and the equivalent with this proposal:

         Runnable r = map?.get(someKey);
         if (r != null)
                 r.run();


However, this is accepted:

         map?.get(someKey).run();

     yet is almost certainly an error.  Should there at least be a  
warning in this case?


Groovy will also allow the following:

         someObject?.someField = someValue

     which does nothing at runtime if someObject is null.  Fan and  
this proposal both reject it.


As discussed on coin-dev, this isn't legal as containsKey() returns a  
primitive type:

         if (!map?.containsKey(key) ?: false) ...	// compiler error

Would it be clear to someone reading the code that these two  
statements are equivalent?

         if (map?.get(key) == null) ...
         if (map == null || map.get(key) == null) ...


Given:

         101:    Map<Foo, Bar> map = ..
         102:    Bar bar = map?.get(someFoo);
         103:    ...
         204:    bar.execute();

     where the programmer has forgotten to protect the bar.execute()  
call (or was unaware of the need, perhaps in a different method), the  
NPE will point at line 204, even if the root cause was 'map' being  
null.  Without use of ?. It would point at line 102 or 204 depending  
on which variable was null.


Groovy has supported Elvis since v1.5 (Dec 2007), other operators for  
longer.  Few Google Code Search results for the former, plenty for  
the latter (but a large percentage cannot be adapted to use  
equivalents from this proposal because the method call results in a  
primitive type, or is used as a statement).

Fan has only had Elvis etc since a July 2008 build (1.0.29).

C# has had Elvis-equivalent '??' operator since v2.0.



From Chris.Allen at nationalcity.com  Mon Apr 13 09:26:18 2009
From: Chris.Allen at nationalcity.com (Allen, Chris)
Date: Mon, 13 Apr 2009 12:26:18 -0400
Subject: Automatic Resource Management
Message-ID: <7108D662C5ED344CBAD8CAFEEC94244115F59488@ohclemsx1023.corp.ntl-city.net>

I've looked at Automatic Resource Management proposal, and written this
email and then sat on it for several days, and it seems that the current
proposal, adding a Disposable interface, is arbitrarily restrictive and
that by using an attribute combined with a signature matching we could
get better bang for our buck.

We already use annotations to describe classes such as persistable or
deprecated, why not as a resource?  I've read the objections on this
list to using an annotation, and the interface proposal does list common
resources such as Streams and SQL constructs, but while the interface
would probably be the preferred way to add this if we were designing the
language from scratch, we already have a huge collection of code out
there where a typical resource pattern is already used - but where
close() is not the disposal method.  People have pointed out locks for
instance, but were told that locks were beyond the scope of this small
change.

Why?

We're looking to make a small change to Java that will make source code
easier to read, write and maintain while making the new constructs easy
to recognize.

The try() syntax that's been proposed seems to meet that criteria,
although I would argue against multiple resources being opened in one
try statement (that's not easy to read) and propose this two-step
processes to find the method called to dispose the target of the try:

1. If the instance's class or one of it parent classes or interfaces has
an attribute of @Disposable the method named in the attributes "value"
value is the name of the method to call.  The default value for "value"
is "close".

So:

    @Disposable("close")
    public abstract java.io.InputStream { ...

    or

    @Disposable
    public abstract java.io.InputStream { ...

    Would call close() to dispose of an InputStream.

where as

    @Disposable("unlock")
   public interface java.util.concurrent.locks.Lock { ...

    Would call unlock() to dispose of a Lock.

2. If the instance's class and all of it's parent classes and interfaces
has no @Disposable attribute, and a instance method matching this
signature 'public void close()' exists, regardless of exception thrown,
it can also be used as a resource.

So:

public void MyClass {

   public void close() throws MyOwnException;

}

Could still be used even without the @Disposable attribute even if it's
compiled in some jar file that I don't have the source for.

I understand the parallelism that we'd like to achieve with the
interface decisions made with Iterator.  There a very small change was
introduced in by the addition of an interface, and voila for-each loops.
But we're talking a much broader range of classes here, including
various 3rd party binaries that have classes that are resources.  With
Iterator there was a very small set of classes affected - mainly
Collection and arrays, but resources could be database connections, text
files, locks, threads, servers, memory, scripting engine or any number
of other things.

Besides, the Disposable interface ends up basically being a marker
interface.  Since no one is going to go around throwing Exception from
the Disposable interface, you're always going to have to narrow the list
of thrown exceptions to something like java.sql.ResultSet so that you
can deal with SQLException instead.  I can't think of a situation where
you're going to be using a Disposable objects directly (other than
perhaps some resource manager).  So Disposable degrades into a marker
interface, and when I think marker interface, I squirm a bit.

Here's how the annotation might be described.

@Documented
@Retention(RetentionPolicy.CLASS)
@Target({ElementType.TYPE})
public @interface java.lang.Disposable {
  String value() default "close";
}

The compiler simply picks the correct dispose method (or methods if
parent classes define additional dispose methods) at compile time so
this has no effect on runtime speed.  Remember, the whole idea is to
change:

A a = new A();
try {
    B b = new B();
    try {   
        a.doSomethingTo(b);
    }
    finally {
        b.dispose();
    }
}
finally {
   a.dispose();
}

into an easier to read, easier to understand, easier to write:

try (A a = new A()) {
    try (B b = new B()) {
        a.doSomethingTo(b);
    }
}

Why should it be limited to classes that have a close() method and have
to have a Disposable interface, too?

As an aside, one of the ideas that needs to be promoted in any of these
proposals, is the idea that the exception thrown during the main life of
the resource receives priority over any exception thrown by the dispose
method(s).  This is a fantastic idea, but sounds fishy at first glance.
By responsibly closing your resource even during some catastrophic event
you can actually erase what the catastrophic event was and waste many
hours of debugging.  This idea needs to be made clear: the proposal
doesn't not hide the dispose exception, just doesn't favor it when
competing with the primary exception.

We already have a lot of JDK code out there and a good portion of it
does not use close() as it's dispose method.  Adding the Dispose
interface to so many classes seems to break the "small change rule".  An
annotation combined with a backup method signature match, covers many
more resources than the interface proposal and is more compatible with
the various types of resources already in use.

P.S. Apologies to any people who's toes I've stepped on, some of the
ideas I've stated here have been stated by others, too.

-Chris Allen

-------------------------------------------------------------------------------------------
***National City made the following annotations
-------------------------------------------------------------------------------------------
This communication is a confidential and proprietary business communication.  
It is intended solely for the use of the designated recipient(s).  If this
communication is received in error, please contact the sender and delete 
this communication.
===========================================================================================

From jjb at google.com  Mon Apr 13 09:38:30 2009
From: jjb at google.com (Joshua Bloch)
Date: Mon, 13 Apr 2009 09:38:30 -0700
Subject: Automatic Resource Management
In-Reply-To: <7108D662C5ED344CBAD8CAFEEC94244115F59488@ohclemsx1023.corp.ntl-city.net>
References: <7108D662C5ED344CBAD8CAFEEC94244115F59488@ohclemsx1023.corp.ntl-city.net>
Message-ID: <17b2302a0904130938y76bc6719g25eb5b6aa413a57e@mail.gmail.com>

Allen,
Hi.  Thanks for taking the time to read the proposal.

On Mon, Apr 13, 2009 at 9:26 AM, Allen, Chris
<Chris.Allen at nationalcity.com>wrote:

> I've looked at Automatic Resource Management proposal, and written this
> email and then sat on it for several days, and it seems that the current
> proposal, adding a Disposable interface, is arbitrarily restrictive and
> that by using an attribute combined with a signature matching we could
> get better bang for our buck.


We discussed this extensively (you can find it in the archive) and Sun made
it clear that this violates the "prime directive" concerning the use of
annotations: they are not permitted to change program semantics.

I floated a related proposal involving the use of "finally" as a modifier
(again, you can find it in the archive), but it necessarily involved changes
to the class file format, the tool chain, etc.  The consensus was that this
was too big a change for Coin, and probably to big a change for the added
benefit.  Moreover, the added flexibility came with added potential for
trouble (how do you ensure that there is a unique disposal method on a given
type, or deal with the situation where there's more than one?).


>
>
> As an aside, one of the ideas that needs to be promoted in any of these
> proposals, is the idea that the exception thrown during the main life of
> the resource receives priority over any exception thrown by the dispose
> method(s).  This is a fantastic idea, but sounds fishy at first glance.
> By responsibly closing your resource even during some catastrophic event
> you can actually erase what the catastrophic event was and waste many
> hours of debugging.  This idea needs to be made clear: the proposal
> doesn't not hide the dispose exception, just doesn't favor it when
> competing with the primary exception.


  I'm hard at work on a revision, and hope to have it out later today.  I
will  make sure to make this clear.


>
>
> We already have a lot of JDK code out there and a good portion of it
> does not use close() as it's dispose method.


That's true, and this facility won't cover everything right away.  But it
will cover enough types to pay for itself and it will cover more over time.
 And in the worst case, you can cover arbitrary types by writing adapters.

           Regards,

           Josh


From angelo.borsotti at gmail.com  Mon Apr 13 14:21:10 2009
From: angelo.borsotti at gmail.com (Angelo Borsotti)
Date: Mon, 13 Apr 2009 23:21:10 +0200
Subject: Proposal for a small language change
Message-ID: <541298b90904131421ocf2aa4buc0bda308f4480367@mail.gmail.com>

Author: Angelo Borsotti, former Senior Director Software Technology,
Alcatel-Lucent Optics

Overview
  Feature Summary: fast and accurate measurement of execution time
  Major Advantage: optimization of algorithms by measuring execution
      times of small snippets of code executed many times
  Major Benefit: greatly increases observability of programs
  Major Disadvantage: very little cost
  Alternatives: there are no alternatives

Examples:

  Simple example:
       long c0 = System.cycles();
       i++;
       long c = System.cycles() - c0;
  Advanced example:
       long cycles = 0;
       for (int i = 0; i < bound; i++){
          ...
          long c0 = System.cycles();
          some statements
          cycles += System.cycles()- c0;
       }

Details
  Specification
     Add a new method System.cycles().
  Compilation
     The method must be compiled inline, translating it into a single
instruction,
     present in most architectures, that reads the cycle counter
register (e.g. the
     TSC in x86 architectures).
     To measure execution time, System.nanoTime() is currently
provided. This, however,
     is by far too inaccurate to measure the execution time of code
which lies inside
     methods, possibly inside loops. The accuracy that it provides is
comparable to the
     time needed to execute thousands of java statements, which is too low.
     Moreover, the time spent to execute the nanoTime() method itself
makes this tool
     too much invasive. Execution times become often much higher when
nanoTime() is
     added, to the point to provide useless results.
     Note that when a piece of code lies inside loops, measuring its execution
     time means adding many small durations. This means that the invasivity
     and the accuracy of the tool to measure time is extremely important.
     Note that also a native method would be too much invasive. The
only way to provide
     a means to measure execution times that introduces an acceptable
noise (i.e. an
     error that is sufficiently lower than the times measured) is to
compile the call
     inline into a machine instruction. Profilers are orders of
magnitude coarser than
     what is needed.
  Testing
     A simple test case in which a very simple example (as the one
above) is used,
     that computes the number of cycles needed to perform a simple
operation. The
     result should then be compared agains an estimate.
  Library suppor
     None needed
  Reflective APIs
     No change
  Other changes
     None
  Migration
     None

Compatibility
  Completely downward compatible

References
  Bug ID: 6685613


From Joe.Darcy at Sun.COM  Mon Apr 13 14:28:49 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Mon, 13 Apr 2009 14:28:49 -0700
Subject: Proposal for a small language change
In-Reply-To: <541298b90904131421ocf2aa4buc0bda308f4480367@mail.gmail.com>
References: <541298b90904131421ocf2aa4buc0bda308f4480367@mail.gmail.com>
Message-ID: <49E3AE91.7010303@sun.com>

The Project Coin call for proposals phase is over; no new proposals are 
being accepted.

Microbenching is a tricky area, but not one requiring language support!

-Joe

PS Somewhat related might be JSR 284: Resource Consumption Management API
http://www.jcp.org/en/jsr/detail?id=284

Angelo Borsotti wrote:
> Author: Angelo Borsotti, former Senior Director Software Technology,
> Alcatel-Lucent Optics
>
> Overview
>   Feature Summary: fast and accurate measurement of execution time
>   Major Advantage: optimization of algorithms by measuring execution
>       times of small snippets of code executed many times
>   Major Benefit: greatly increases observability of programs
>   Major Disadvantage: very little cost
>   Alternatives: there are no alternatives
>
> Examples:
>
>   Simple example:
>        long c0 = System.cycles();
>        i++;
>        long c = System.cycles() - c0;
>   Advanced example:
>        long cycles = 0;
>        for (int i = 0; i < bound; i++){
>           ...
>           long c0 = System.cycles();
>           some statements
>           cycles += System.cycles()- c0;
>        }
>
> Details
>   Specification
>      Add a new method System.cycles().
>   Compilation
>      The method must be compiled inline, translating it into a single
> instruction,
>      present in most architectures, that reads the cycle counter
> register (e.g. the
>      TSC in x86 architectures).
>      To measure execution time, System.nanoTime() is currently
> provided. This, however,
>      is by far too inaccurate to measure the execution time of code
> which lies inside
>      methods, possibly inside loops. The accuracy that it provides is
> comparable to the
>      time needed to execute thousands of java statements, which is too low.
>      Moreover, the time spent to execute the nanoTime() method itself
> makes this tool
>      too much invasive. Execution times become often much higher when
> nanoTime() is
>      added, to the point to provide useless results.
>      Note that when a piece of code lies inside loops, measuring its execution
>      time means adding many small durations. This means that the invasivity
>      and the accuracy of the tool to measure time is extremely important.
>      Note that also a native method would be too much invasive. The
> only way to provide
>      a means to measure execution times that introduces an acceptable
> noise (i.e. an
>      error that is sufficiently lower than the times measured) is to
> compile the call
>      inline into a machine instruction. Profilers are orders of
> magnitude coarser than
>      what is needed.
>   Testing
>      A simple test case in which a very simple example (as the one
> above) is used,
>      that computes the number of cycles needed to perform a simple
> operation. The
>      result should then be compared agains an estimate.
>   Library suppor
>      None needed
>   Reflective APIs
>      No change
>   Other changes
>      None
>   Migration
>      None
>
> Compatibility
>   Completely downward compatible
>
> References
>   Bug ID: 6685613
>
>   



From Ulf.Zibis at gmx.de  Mon Apr 13 14:43:08 2009
From: Ulf.Zibis at gmx.de (Ulf Zibis)
Date: Mon, 13 Apr 2009 23:43:08 +0200
Subject: Proposal for a small language change
In-Reply-To: <541298b90904131421ocf2aa4buc0bda308f4480367@mail.gmail.com>
References: <541298b90904131421ocf2aa4buc0bda308f4480367@mail.gmail.com>
Message-ID: <49E3B1EC.7060309@gmx.de>

+1

-Ulf


Am 13.04.2009 23:21, Angelo Borsotti schrieb:
> Author: Angelo Borsotti, former Senior Director Software Technology,
> Alcatel-Lucent Optics
>
> Overview
>   Feature Summary: fast and accurate measurement of execution time
>   Major Advantage: optimization of algorithms by measuring execution
>       times of small snippets of code executed many times
>   Major Benefit: greatly increases observability of programs
>   Major Disadvantage: very little cost
>   Alternatives: there are no alternatives
>
> Examples:
>
>   Simple example:
>        long c0 = System.cycles();
>        i++;
>        long c = System.cycles() - c0;
>   Advanced example:
>        long cycles = 0;
>        for (int i = 0; i < bound; i++){
>           ...
>           long c0 = System.cycles();
>           some statements
>           cycles += System.cycles()- c0;
>        }
>
> Details
>   Specification
>      Add a new method System.cycles().
>   Compilation
>      The method must be compiled inline, translating it into a single
> instruction,
>      present in most architectures, that reads the cycle counter
> register (e.g. the
>      TSC in x86 architectures).
>      To measure execution time, System.nanoTime() is currently
> provided. This, however,
>      is by far too inaccurate to measure the execution time of code
> which lies inside
>      methods, possibly inside loops. The accuracy that it provides is
> comparable to the
>      time needed to execute thousands of java statements, which is too low.
>      Moreover, the time spent to execute the nanoTime() method itself
> makes this tool
>      too much invasive. Execution times become often much higher when
> nanoTime() is
>      added, to the point to provide useless results.
>      Note that when a piece of code lies inside loops, measuring its execution
>      time means adding many small durations. This means that the invasivity
>      and the accuracy of the tool to measure time is extremely important.
>      Note that also a native method would be too much invasive. The
> only way to provide
>      a means to measure execution times that introduces an acceptable
> noise (i.e. an
>      error that is sufficiently lower than the times measured) is to
> compile the call
>      inline into a machine instruction. Profilers are orders of
> magnitude coarser than
>      what is needed.
>   Testing
>      A simple test case in which a very simple example (as the one
> above) is used,
>      that computes the number of cycles needed to perform a simple
> operation. The
>      result should then be compared agains an estimate.
>   Library suppor
>      None needed
>   Reflective APIs
>      No change
>   Other changes
>      None
>   Migration
>      None
>
> Compatibility
>   Completely downward compatible
>
> References
>   Bug ID: 6685613
>
>
>   



From mthornton at optrak.co.uk  Mon Apr 13 14:44:22 2009
From: mthornton at optrak.co.uk (Mark Thornton)
Date: Mon, 13 Apr 2009 22:44:22 +0100
Subject: Proposal for a small language change
In-Reply-To: <541298b90904131421ocf2aa4buc0bda308f4480367@mail.gmail.com>
References: <541298b90904131421ocf2aa4buc0bda308f4480367@mail.gmail.com>
Message-ID: <49E3B236.2050406@optrak.co.uk>

Angelo Borsotti wrote:
> Author: Angelo Borsotti, former Senior Director Software Technology,
> Alcatel-Lucent Optics
>
> Overview
>   Feature Summary: fast and accurate measurement of execution time
>   Major Advantage: optimization of algorithms by measuring execution
>       times of small snippets of code executed many times
>   Major Benefit: greatly increases observability of programs
>   Major Disadvantage: very little cost
>   Alternatives: there are no alternatives
>
> Examples:
>
>   Simple example:
>        long c0 = System.cycles();
>        i++;
>        long c = System.cycles() - c0;
>   Advanced example:
>        long cycles = 0;
>        for (int i = 0; i < bound; i++){
>           ...
>           long c0 = System.cycles();
>           some statements
>           cycles += System.cycles()- c0;
>        }
>
>   
As Joe has said the proposal period is over and this proposal doesn't 
need a language change.

The existing System.nanoTime() method could be implemented using CPU 
cycle counters. However there are significant problems on multi-core or 
multi-processor systems and where power management is in use. Some 
systems don't keep the cycle counters synchronized across CPUs, so if a 
thread is migrated from one CPU to another the computed elapsed cycle 
time is not reliable.

Some interesting information on timing can be found here:

http://blogs.sun.com/dholmes/entry/inside_the_hotspot_vm_clocks

Mark Thornton



From reinier at zwitserloot.com  Mon Apr 13 14:58:22 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Mon, 13 Apr 2009 23:58:22 +0200
Subject: Proposal for a small language change
In-Reply-To: <49E3B1EC.7060309@gmx.de>
References: <541298b90904131421ocf2aa4buc0bda308f4480367@mail.gmail.com>
	<49E3B1EC.7060309@gmx.de>
Message-ID: <EF7ECA20-6384-4981-9C61-6E1C3438F8FB@zwitserloot.com>

Bad Idea:

What you're talking about is microbenchmarking. Trying to do it, is  
almost always a good indicator that you're Doing It Wrong. Java  
doesn't microbenchmark well for several reasons. If you really must  
benchmark some code, here's how you MUST do it; the following scheme  
is a neccessary but not sufficient guarantee that you might just be  
getting relevant timing numbers:


Set up something that can be looped over many times. Then, time the  
time it takes to run the entire loop. Make sure the data that is  
calculated is used someplace; for example, if you're calculating  
lists, add the sizes of the lists to a number, then, at the end, print  
the number (do the printing after the timing, of course - it takes  
ages!) - otherwise the hotspot compiler will just excise the entire  
code!

Time it for many different loop invocations, and draw a chart. loop  
count on the x-axis, time taken (in total, not per iteration) on the y- 
axis.

Keep doing this until you get a graph that looks a little like this:

for the first X iterations, the line is roughly linear, with a slope  
of m. Then, there's a sudden spike, and after the spike, the line  
becomes linear again, with a different slope of n. n is significantly  
smaller than m (the line is closer to the horizontal).

Once you've reached this chart, you've got your answer: The spike is  
the hotspot compiler kicking in. The m slope gives you the time for  
the loop pre-hotspot and is mostly irrelevant. The n slope gives you  
the post-hotspot and is more relevant.

This is better than blind microbenchmarking but I'm leaving out many,  
many important details about how to do microbenchmarking appropriately  
in java.



A 'cycle' method really isn't going to help much - the timing you need  
to do is many orders of magnitude larger than what System.nanoTime()  
can reliably measure, so existing tools are fine.


Secondly, and more importantly: That's not where timing is _supposed_  
to be done in the first place. That's where JVMTI comes in - that's  
where you need to be doing this. Download a profiler (netbeans has a  
nice one!) and work with that. A JVM debug can generate cycle  
instructions if that really would be helpful, just like debug JVMs can  
print the assembler code generated when hotspotting for the local  
architecture.

If the profiler team needs something to improve their ability to  
profile, that should certainly be considered, but I seriously doubt  
they'll be needing a cycle() JVM bytecode to do their job.

  --Reinier Zwitserloot



On Apr 13, 2009, at 23:43, Ulf Zibis wrote:

> +1
>
> -Ulf
>
>
> Am 13.04.2009 23:21, Angelo Borsotti schrieb:
>> Author: Angelo Borsotti, former Senior Director Software Technology,
>> Alcatel-Lucent Optics
>>
>> Overview
>>  Feature Summary: fast and accurate measurement of execution time
>>  Major Advantage: optimization of algorithms by measuring execution
>>      times of small snippets of code executed many times
>>  Major Benefit: greatly increases observability of programs
>>  Major Disadvantage: very little cost
>>  Alternatives: there are no alternatives
>>
>> Examples:
>>
>>  Simple example:
>>       long c0 = System.cycles();
>>       i++;
>>       long c = System.cycles() - c0;
>>  Advanced example:
>>       long cycles = 0;
>>       for (int i = 0; i < bound; i++){
>>          ...
>>          long c0 = System.cycles();
>>          some statements
>>          cycles += System.cycles()- c0;
>>       }
>>
>> Details
>>  Specification
>>     Add a new method System.cycles().
>>  Compilation
>>     The method must be compiled inline, translating it into a single
>> instruction,
>>     present in most architectures, that reads the cycle counter
>> register (e.g. the
>>     TSC in x86 architectures).
>>     To measure execution time, System.nanoTime() is currently
>> provided. This, however,
>>     is by far too inaccurate to measure the execution time of code
>> which lies inside
>>     methods, possibly inside loops. The accuracy that it provides is
>> comparable to the
>>     time needed to execute thousands of java statements, which is  
>> too low.
>>     Moreover, the time spent to execute the nanoTime() method itself
>> makes this tool
>>     too much invasive. Execution times become often much higher when
>> nanoTime() is
>>     added, to the point to provide useless results.
>>     Note that when a piece of code lies inside loops, measuring its  
>> execution
>>     time means adding many small durations. This means that the  
>> invasivity
>>     and the accuracy of the tool to measure time is extremely  
>> important.
>>     Note that also a native method would be too much invasive. The
>> only way to provide
>>     a means to measure execution times that introduces an acceptable
>> noise (i.e. an
>>     error that is sufficiently lower than the times measured) is to
>> compile the call
>>     inline into a machine instruction. Profilers are orders of
>> magnitude coarser than
>>     what is needed.
>>  Testing
>>     A simple test case in which a very simple example (as the one
>> above) is used,
>>     that computes the number of cycles needed to perform a simple
>> operation. The
>>     result should then be compared agains an estimate.
>>  Library suppor
>>     None needed
>>  Reflective APIs
>>     No change
>>  Other changes
>>     None
>>  Migration
>>     None
>>
>> Compatibility
>>  Completely downward compatible
>>
>> References
>>  Bug ID: 6685613
>>
>>
>>
>
>



From reinier at zwitserloot.com  Mon Apr 13 15:21:44 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Tue, 14 Apr 2009 00:21:44 +0200
Subject: Automatic Resource Management
In-Reply-To: <7108D662C5ED344CBAD8CAFEEC94244115F59488@ohclemsx1023.corp.ntl-city.net>
References: <7108D662C5ED344CBAD8CAFEEC94244115F59488@ohclemsx1023.corp.ntl-city.net>
Message-ID: <1A55DAD4-F03E-4E06-8C52-C9939006A70A@zwitserloot.com>

Allen, you haven't answered any of the questions about using an  
annotation, even if we forget for a moment that annotations aren't  
supposed to be used for this in the first place:

1. Do @Disposable annotations inherit (if not, the proposal really  
stinks, so I'll assume it does, which leads to):

2. What if 1 object has multiple @Disposable annotations? Call them  
all? That's rather a lot of exceptions that could occur - do we stop  
calling them all once one of them throws an exception, or keep going?

3. What if the close() method doesn't actually exist? Whose job is it  
to generate a compiler error?

4. Should @Disposable be sorted out at runtime, or at compiletime? In  
other words, if I have a variable typed 'Foobar', named 'foobar', and  
I try() on this, should I just call all the close methods that I can  
find when chasing down the Disposable annotations of Foobar, or should  
I ask for foobar's actual type (foobar.getClass()) and work with that  
instead? If we go with the compile-time option, then won't this cause  
some fairly serious confusion and possible resource leakage?


These are all serious issues, and while you could pick a solution for  
them all, and document this extensively, your average java programming  
just doesn't read all of the JLS - in other words, language changes  
should be as self-sensible as possible. Josh's proposal may not work  
for every existing class, but it has clear and obvious answers for ALL  
of those issues. In case people are wondering what they are, here they  
briefly follow:

1. interfaces inherit already (if your superclass implements X, so do  
you - you can't undo this), so the answer is obvious: Yes.

2. There's only one method, so even if the Disposable interface is  
implemented many times over, it makes absolutely no difference:  
close() willbe called, and that's the only method.

3. It's already an error to not implement an abstract method, so  
that's easy.

4. This situation cannot occur; either the compile-time type is a  
Disposable, and thus the close() method is called, or it isn't, and  
the try() form is not even legal. You could cast your object to a  
Disposable, and this would work, but then the method to call is also  
obvious (close), as is the error when the object isn't actually  
disposable at all (ClassCastException). None of these things even need  
to be specified in Josh's ARM proposal, because these are the rules  
that already apply to implementing interfaces.



I hope this mail summarizes the major issues (aside from the notion  
that annotations should not affect compilation like this) with using  
an annotation. Before initiating too much discussion on these  
problems, please review the (many, many) emails that have already been  
spent on the topic, lest we just rehash the same arguments over and  
over.


A telling point: NOBODY submitted an official annotation based ARM  
proposal for coin (at least none that had a snowball's chance of being  
accepted - i.e. having enough detail to update javac and covering  
every open issue like the ones stated above).


  --Reinier Zwitserloot



On Apr 13, 2009, at 18:26, Allen, Chris wrote:

> I've looked at Automatic Resource Management proposal, and written  
> this
> email and then sat on it for several days, and it seems that the  
> current
> proposal, adding a Disposable interface, is arbitrarily restrictive  
> and
> that by using an attribute combined with a signature matching we could
> get better bang for our buck.
>
> We already use annotations to describe classes such as persistable or
> deprecated, why not as a resource?  I've read the objections on this
> list to using an annotation, and the interface proposal does list  
> common
> resources such as Streams and SQL constructs, but while the interface
> would probably be the preferred way to add this if we were designing  
> the
> language from scratch, we already have a huge collection of code out
> there where a typical resource pattern is already used - but where
> close() is not the disposal method.  People have pointed out locks for
> instance, but were told that locks were beyond the scope of this small
> change.
>
> Why?
>
> We're looking to make a small change to Java that will make source  
> code
> easier to read, write and maintain while making the new constructs  
> easy
> to recognize.
>
> The try() syntax that's been proposed seems to meet that criteria,
> although I would argue against multiple resources being opened in one
> try statement (that's not easy to read) and propose this two-step
> processes to find the method called to dispose the target of the try:
>
> 1. If the instance's class or one of it parent classes or interfaces  
> has
> an attribute of @Disposable the method named in the attributes "value"
> value is the name of the method to call.  The default value for  
> "value"
> is "close".
>
> So:
>
>    @Disposable("close")
>    public abstract java.io.InputStream { ...
>
>    or
>
>    @Disposable
>    public abstract java.io.InputStream { ...
>
>    Would call close() to dispose of an InputStream.
>
> where as
>
>    @Disposable("unlock")
>   public interface java.util.concurrent.locks.Lock { ...
>
>    Would call unlock() to dispose of a Lock.
>
> 2. If the instance's class and all of it's parent classes and  
> interfaces
> has no @Disposable attribute, and a instance method matching this
> signature 'public void close()' exists, regardless of exception  
> thrown,
> it can also be used as a resource.
>
> So:
>
> public void MyClass {
>
>   public void close() throws MyOwnException;
>
> }
>
> Could still be used even without the @Disposable attribute even if  
> it's
> compiled in some jar file that I don't have the source for.
>
> I understand the parallelism that we'd like to achieve with the
> interface decisions made with Iterator.  There a very small change was
> introduced in by the addition of an interface, and voila for-each  
> loops.
> But we're talking a much broader range of classes here, including
> various 3rd party binaries that have classes that are resources.  With
> Iterator there was a very small set of classes affected - mainly
> Collection and arrays, but resources could be database connections,  
> text
> files, locks, threads, servers, memory, scripting engine or any number
> of other things.
>
> Besides, the Disposable interface ends up basically being a marker
> interface.  Since no one is going to go around throwing Exception from
> the Disposable interface, you're always going to have to narrow the  
> list
> of thrown exceptions to something like java.sql.ResultSet so that you
> can deal with SQLException instead.  I can't think of a situation  
> where
> you're going to be using a Disposable objects directly (other than
> perhaps some resource manager).  So Disposable degrades into a marker
> interface, and when I think marker interface, I squirm a bit.
>
> Here's how the annotation might be described.
>
> @Documented
> @Retention(RetentionPolicy.CLASS)
> @Target({ElementType.TYPE})
> public @interface java.lang.Disposable {
>  String value() default "close";
> }
>
> The compiler simply picks the correct dispose method (or methods if
> parent classes define additional dispose methods) at compile time so
> this has no effect on runtime speed.  Remember, the whole idea is to
> change:
>
> A a = new A();
> try {
>    B b = new B();
>    try {
>        a.doSomethingTo(b);
>    }
>    finally {
>        b.dispose();
>    }
> }
> finally {
>   a.dispose();
> }
>
> into an easier to read, easier to understand, easier to write:
>
> try (A a = new A()) {
>    try (B b = new B()) {
>        a.doSomethingTo(b);
>    }
> }
>
> Why should it be limited to classes that have a close() method and  
> have
> to have a Disposable interface, too?
>
> As an aside, one of the ideas that needs to be promoted in any of  
> these
> proposals, is the idea that the exception thrown during the main  
> life of
> the resource receives priority over any exception thrown by the  
> dispose
> method(s).  This is a fantastic idea, but sounds fishy at first  
> glance.
> By responsibly closing your resource even during some catastrophic  
> event
> you can actually erase what the catastrophic event was and waste many
> hours of debugging.  This idea needs to be made clear: the proposal
> doesn't not hide the dispose exception, just doesn't favor it when
> competing with the primary exception.
>
> We already have a lot of JDK code out there and a good portion of it
> does not use close() as it's dispose method.  Adding the Dispose
> interface to so many classes seems to break the "small change  
> rule".  An
> annotation combined with a backup method signature match, covers many
> more resources than the interface proposal and is more compatible with
> the various types of resources already in use.
>
> P.S. Apologies to any people who's toes I've stepped on, some of the
> ideas I've stated here have been stated by others, too.
>
> -Chris Allen
>
> -------------------------------------------------------------------------------------------
> ***National City made the following annotations
> -------------------------------------------------------------------------------------------
> This communication is a confidential and proprietary business  
> communication.
> It is intended solely for the use of the designated recipient(s).   
> If this
> communication is received in error, please contact the sender and  
> delete
> this communication.
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
>



From reinier at zwitserloot.com  Mon Apr 13 16:54:54 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Tue, 14 Apr 2009 01:54:54 +0200
Subject: Automatic Resource Management
In-Reply-To: <200904140134.22467.peter.levart@gmail.com>
References: <7108D662C5ED344CBAD8CAFEEC94244115F59488@ohclemsx1023.corp.ntl-city.net>
	<1A55DAD4-F03E-4E06-8C52-C9939006A70A@zwitserloot.com>
	<200904140134.22467.peter.levart@gmail.com>
Message-ID: <EAC85F99-5B9E-4663-969E-D1E01C182362@zwitserloot.com>

If the notion that 1 interface, with the associated forced 'close()'  
method, is considered too great of a problem, then your proposal is  
certainly the only viable alternative IMO. You can even play with the  
syntax to open multiple resources (but personally I'm somewhat opposed  
to letting any kind of ARM block open multiple resources in one  
statement; what's the problem with nesting a few of them?).


The problem I have with your proposal is twofold. One is simple, one  
is fairly esoteric:

1. Disposable/close() fits almost all use-cases, and the foreach  
syntax has shown that not covering every single existent base is not  
going to be a problem; the java world will adapt and come around to  
it. Especially because the libraries that can't work with this scheme  
don't seem too important to the java community at this point (more on  
that later).

2. The esoteric one: For semantics' sake, I would consider the closing  
statement to be better located at the end of the guarded block - but  
how do we figure this out, syntax wise? You could use the 'finally'  
keyword, which makes some sense, but the finally keyword already has  
meanings which are not quite compatible with the meaning of ARM-style  
final code: exceptions in the main body have precedence in ARM blocks,  
but they lose out in the usual try/finally. This makes finally a bad  
keyword, and in fact gets in the way of the entire concept: It LOOKS  
like you're just using a slightly different version of try/finally  
syntax, but that's not really what's going on. That makes your  
proposal somewhat ambiguous without knowing the JLS specifics. It's  
not nearly as bad as some of the other proposals, so not a  
showstopper, but certainly a nit.


Having said that, there might be a way out of this, by integrating  
both proposals.

1. Remove the ability to put multiple resources in one statement;  
what's the problem with nesting trywith blocks again?

2. Use the ; to switch to the alternate form of resource management:  
try ( a ; b ) {} no longer requires that is an expression of type  
'Disposable' (or a variable declaration of a Disposable), and instead,  
b is run at the end analogous to your proposal.


Then, for all objects that know how to dispose of themselves, you just  
go try ( object ) { stuff }, but when they don't, you can work around  
it with try ( object ; closeIt ) { stuff }.

NOTE: I'm not actually in favour of this, because, at the risk of  
taking a contentious position, I don't rate the libraries that can't  
deal with Disposable very highly. SWT was absolutely excellent when it  
was released, and the java community owes it a great thank you for  
lighting the fire of competition under awt/swing's behind, but between  
new swing versions and javaFX, SWT's time has gone, eclipse needs to  
migrate over, and SWT needs to slowly but surely go away now. Locks  
are handled just as well, IMO, with the existing try/finally  
structure, primarily because lock.unlock() generally doesn't throw  
exceptions, which is a big reason for using ARM in the first place.

  --Reinier Zwitserloot



On Apr 14, 2009, at 01:34, Peter Levart wrote:

> Hello Reinier,
>
> What do you think of the idea of explicit resource cleanup (as  
> opposed to
> using interface) that I have described a few days ago (in
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001383.html) 
> .
>
> The way I see it is best described by the following parallelism:
>
> Cleaning up resources correctly with existing try-catch-finally  
> construct as
> opposed to using Joshua's ARM is like iterating over elements of the  
> array
> using while loop as opposed to using foreach.
>
> int i = 0;
> while (i < array.length)
> {
> 	Type a = array[i] ;
> 	...
> 	i++;
> }
>
> vs.
>
> foreach (Type a : array)
> {
> 	...
> }
>
>
> ... but using existing  try-catch-finally vs. Semi-Automatic- 
> Resource-Cleanup
> (described in my previous mail) is like using while vs. for
>
> int i = 0;
> while (i < array.length)
> {
> 	Type a = array[i] ;
> 	...
> 	i++;
> }
>
> vs.
>
> for (int i = 0; i < array.length; i++)
> {
> 	Type a = array[i];
> 	...
> }
>
>
> ...there's not much less typing, everything is still explicit. But  
> the idiom
> is "captured" in a predefined construct leaving less chance for an  
> average
> programmer to do it wrong.
>
> Using 'for' instead of 'foreach' leaves you more flexibility if you  
> need it.
> For example:
>
> for (int i = offset; i < array.length && i < offset + length; i+ 
> +) ... etc.
>
> The question is: Do we want to be more flexible (and type a little  
> more) when
> capturing the resource cleanup idiom?
>
> Regards, Peter
>



From Joe.Darcy at Sun.COM  Mon Apr 13 18:55:08 2009
From: Joe.Darcy at Sun.COM (Joe Darcy)
Date: Mon, 13 Apr 2009 18:55:08 -0700
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <f1eba259d51e01b1f96f4fd29202fb94.squirrel@wmail.gradsoft.ua>
References: <4b4f45e00904020439q28caaeacrc6f53fa1cae50187@mail.gmail.com>
	<28bca0ff0904020528l51d803f2t5a6dc29a8f6a67dc@mail.gmail.com>
	<b1cac5cf489dbd8c889200db29eb11cd.squirrel@wmail.gradsoft.ua>
	<31AB3E69-CCE7-4134-95C9-4DB5BF6C9281@zwitserloot.com>
	<d8e827e34ea76f830c27ec529a882e57.squirrel@wmail.gradsoft.ua>
	<49D516A6.6000404@sun.com>
	<f1eba259d51e01b1f96f4fd29202fb94.squirrel@wmail.gradsoft.ua>
Message-ID: <49E3ECFC.6000002@sun.com>

On 04/02/09 04:30 PM, rssh at gradsoft.com.ua wrote:

[snip]

>>> Note, that I does not propose use polls as one and only one criteria. I
>>> just tell that see result of such poll will be interest.
>>>
>>> // btw - from other side, all this activity is overkill, I can suggest,
>>> // that  accepted proposals would be exactly same, which was listed in
>>> // project-coin description (before coin was started)
>>> //     http://blogs.sun.com/darcy/entry/project_coin
>>> //   +ARM  +jsr292  and ...  it's already 6, which is more than 5 :)
>>>
>>>       
>> Your own sentence disproves your point since ARM was not listed among
>> the five proposal areas under consideration before Project Coin started.
>>
>>     
>
> I mean not '<cite>would be exactly same, which was listed in project-coin
> description (before coin was started)[url]</cite>', but '<cite>would be
> exactly same, which was listed in project-coin description (before coin
> was started)[url] +ARM  +jsr292</cite>',
>  sorry for ambiguity.
>
>  ARM floating around (and widly discussed) from late 2007 or early 2008.
> And all we know, that if BGGA will not available, than at least ARM must
> be included.  

I don't know that.

> I. e. I can't say that ARM is 'external' and new or not to
> be generally known be included in Java 7 before project coin start.
>   


> I have no pretension about judgement process, It's only about information
> flow: i. e. Sun have all proposals before and <IMHO> call for new
> proposals with process of selecting 5 from set of newly received and 5
> apriory well-known items, for which we know, that they are necessory, it's
> near the same, that throw away all non-apriory proposals.
> </IMHO>
>
> I. e. I guess, that when people asked to submit new proposals, they expect
> that exists demand for new proposals, not demand for choosing from five
> well-known items. When appointment of all new proposals to be thrown away,
> with role be backgroung for well-known items, people, which invested some
> time in such activity, usually frustrated. It's why I think, that call for
> new proposals, whithout real possibility to implement something new (not
> well-known before) was an error. If we have slot, for example, in summary
> for 10 proposals to implement (5 well know and 5 new) - then all ok, it's
> fair game.
>   

Amongst other factors, the maximum number of proposals that can get in 
is a function of how many people work on implementations.  Very few of 
the proposals had any accompanying prototype.  For example, I'm 
sympathetic to the idea of having literals for bit strings and the like; 
those are much more likely to end up as part of the platform if people 
outside of Sun take the lead on the implementation.  However, even with 
help from the broader community, there is still an upper-bound on how 
many small language changes can get in because of various kinds of 
coordination activities that do not scale and the non-implementation 
aspects of the work (specification and testing).

Many of the submitted proposals were not really proposals in terms of a 
thoughtful analysis of what it would take to add a feature to the 
platform; rather they were "requests for enhancement" in Sun bug 
database terminology where much of the hard work of thinking through 
implications and interactions was left undone.  Existing discussion of 
such issues from Sun's bug database were often ignored even though they 
can be found by a simple web search query.  And a specification is much 
more than the grammatical changes involved!

>>> I. e. doing project coin with external auditory  was a 'Sun system
>>> error',
>>> I guess; if they want some feedback from community, correct way was at
>>> first implement own stuff, than ask community for something new ;)
>>>
>>>       
>> The call of proposal phase of Project Coin is an effort both to solicit
>> feedback from the external community and also to invite the external
>> community to participate more directly in evolving the language.  That
>> opportunity to participate also implies participating in the large
>> amount of work required to go from "I have this great idea!" to "I have
>> this great idea and here is a carefully considered review of all the
>> implications of the idea, along with a prototype."  The blogs I wrote
>> last year and the proposal form itself are part of an effort to explain
>> and expose what this language work entails so more people can get
>> involved.
>>
>>     
>
>
> It would be great, to participate in language evolution in future.
> For now I does not see general aviable process for future participation:
> call closed, all new proposal throwed away.
>   

I would counter the list received few serious actual proposals, which is 
directly tied to why few proposals (so far) have been selected for 
further consideration.  I reviewed all open language specification RFEs 
last year.  A restatement of an existing RFE in Sun's bug database as a 
Project Coin proposal without any further analysis has approximately 
zero value. 

Last year I published a list of five proposal ideas to seed the 
discussion.  Opinions will differ of course (different parts of the 
elephant), but I think few of the submitted proposals were as compelling 
as the problems being addressed by those initial five proposals, which 
again relates to why those proposal areas have not been displaced by 
subsequent ones.

> Finish. Fire bug reports is useless - they will live in bugzilla for years.
>
> One possible solution: is make 'coin project' regular, for example once a
> year. (May be with
> entry barrier as 'required implementation in some form')
> Another - propose some process (may be long) for author, how to push his
> proposal (whith implementation)
> into language after JDK7 (or receive official position, that this change
> is rejected)
>
>
>   
>> Unfortunately, many of the submitted proposals did not do a credible job
>> of analyzing the true effect the proposal would have, which has a rather
>> strong relation to why many were not chosen for further consideration.
>> For example, let's take the "'This' type" proposal:
>>
>>     
>  ...
>
>
> Problem with inaccurate proposals - it's well known problem, the same with
> publications, wildly used technique is peer review. (Honesly, overall
> quality of proposals was better that I was expected).
>   

Yes, the list is for peer review and many proposals found a vigorous 
discussion there!

In retrospect, I think it would have been helpful to publish, say, the 
completed strings in switch proposal form sooner after the proposal form 
was published.  That form for a very simple language change indicates 
the degree of thoroughnesses I would have liked to have seen from all 
the proposals:

http://mail.openjdk.java.net/pipermail/coin-dev/2009-February/000001.html

> Good entry barrier can be requirement to proposal to be implemented in
> some form.
>
> P.S. Project coin involved me to think about Java more close than before.
> So, despite my criticism, you achieve goal to raise interest to
> participate in process of Java language evolution ;)
>   
That is something at least ;-)

-Joe


From peter.levart at gmail.com  Tue Apr 14 00:04:23 2009
From: peter.levart at gmail.com (Peter Levart)
Date: Tue, 14 Apr 2009 09:04:23 +0200
Subject: Automatic Resource Management
In-Reply-To: <EAC85F99-5B9E-4663-969E-D1E01C182362@zwitserloot.com>
References: <7108D662C5ED344CBAD8CAFEEC94244115F59488@ohclemsx1023.corp.ntl-city.net>
	<1A55DAD4-F03E-4E06-8C52-C9939006A70A@zwitserloot.com>
	<200904140134.22467.peter.levart@gmail.com>
	<EAC85F99-5B9E-4663-969E-D1E01C182362@zwitserloot.com>
Message-ID: <aad309390904140004w551c71d3h24a1602ec649b62b@mail.gmail.com>

On Tue, Apr 14, 2009 at 1:54 AM, Reinier Zwitserloot <
reinier at zwitserloot.com> wrote:

> Having said that, there might be a way out of this, by integrating both
> proposals.
>
> 1. Remove the ability to put multiple resources in one statement; what's
> the problem with nesting trywith blocks again?
>
> 2. Use the ; to switch to the alternate form of resource management: try (
> a ; b ) {} no longer requires that is an expression of type 'Disposable' (or
> a variable declaration of a Disposable), and instead, b is run at the end
> analogous to your proposal.
>
> Then, for all objects that know how to dispose of themselves, you just go
> try ( object ) { stuff }, but when they don't, you can work around it with
> try ( object ; closeIt ) { stuff }.


That's a great idea. It would encourage people to build APIs around a common
interface but still allow using a different style of programming or enable
proper resource cleanup even in situations where the shear reference to the
resource is not enough to dispose it. What am I talking about?


> NOTE: I'm not actually in favour of this, because, at the risk of taking a
> contentious position, I don't rate the libraries that can't deal with
> Disposable very highly. SWT was absolutely excellent when it was released,
> and the java community owes it a great thank you for lighting the fire of
> competition under awt/swing's behind, but between new swing versions and
> javaFX, SWT's time has gone, eclipse needs to migrate over, and SWT needs to
> slowly but surely go away now. Locks are handled just as well, IMO, with the
> existing try/finally structure, primarily because lock.unlock() generally
> doesn't throw exceptions, which is a big reason for using ARM in the first
> place.
>
>  --Reinier Zwitserloot


... I'm thinking of numerous situations where propper clean-up is the
responsibility of third party code, not the resource itself. This is usually
the case of libraries that are build as a wrapper arround some other
lower-level API and expose references to lower-level resources. Take for
example Hibernate. There's a snippet of code from an "identity generator"
(the resources are not closed optimally here since exceptions thrown in
resource cleanup override main exceptions. The reason? Probably laziness):

        try
        {
            PreparedStatement st =
session.getBatcher().prepareSelectStatement(sql);
            try
            {
                ResultSet rs = st.executeQuery();
                try
                {
                    rs.next();
                    return rs.getLong(1);
                }
                finally
                {
                    rs.close();
                }
            }
            finally
            {
                session.getBatcher().closeStatement(st);
            }
        }
        catch (SQLException sqle)
        {
            throw JDBCExceptionHelper.convert(
                session.getFactory().getSQLExceptionConverter(),
                sqle,
                "could not execute select statement",
                sql
            );
        }

... here a special class called Batcher is the manager of the JDBC resource
called PreparedStatement. Proper initialization and cleanup is it's
responsibillity. You may argue that Hibernate should not "leak" lower-level
API through it's own API and should wrap PreparedStatement in it's own
class. That is the ideal world. In reality this is often practiced to make
code more "economic".


Regards, Peter


From Ulf.Zibis at gmx.de  Wed Apr 15 07:33:04 2009
From: Ulf.Zibis at gmx.de (Ulf Zibis)
Date: Wed, 15 Apr 2009 16:33:04 +0200
Subject: scripts and results (was Helping to find the usefulness of a
	proposal)
In-Reply-To: <60287e9e1530b3e1ae49976316e8dc57.squirrel@wmail.gradsoft.ua>
References: <60287e9e1530b3e1ae49976316e8dc57.squirrel@wmail.gradsoft.ua>
Message-ID: <49E5F020.7060508@gmx.de>

Hi Ruslan,

I would like to see the results for

     "objects and expressions in switch"

which includes:
- string in switch
- instanceof switch

I guess a very big chunk of all if-else if-structures would be covered by:
http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001182.html

A n y   C A P A C I T Y   t o   a d d   t h i s  p a t t e r n   t o   y 
o u r   s c r i p t ? ?

As I argued before, I'm against the current syntax of the "string in 
switch"-proposal, as it weakens switch..case semantics for identity, and 
it encumbers later enhancements for the future. See: 
http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001328.html.

- Ulf



Am 07.04.2009 02:33, Ruslan Shevchenko schrieb:
>  Good day,
>
> Few days ago Stephan give idea about writing simple script, which
>  count amount of possible-optimizations of existing code.
>
> So, I wrote few checks for some of such entries. They count
> low bound of number of code patterns, which can be optimized with
> some of coin proposal and situated on distinct source lines.
>
> I'm afraid that information, which come from count of such code patterns
> can give incorrect direction:  when we have such patterns in code,
> it's means that problem is not so big and we can easy live with one.
>  Big language problems solved (or not) in non-trivial way, when we have no
> common (may be ugly) workaround.
> For example. in Java we rare will see BigDecimal.add()  because it is not
> easy to work with BigDecimals, instead people work with double and have
> troubles
> with floating points rounding issues (see
> http://www.ddj.com/java/184405721)).
> Yet one example - choosing another language for implementing db-intensive
> parts of projects.
>
> Ok, you warned;  data still can be interesting:
>
> Checked patterns was:
>   string in switch
>   instanceof switch
>   byte literals
>   multi catch
>   loop by iterator, with call remove inside loop
>
>  (if you want include other checks, you can add one at
>  etc/checkers_coin.def or ask me [but without any warranty])
>
> <BTW>
> Exists one proposal, which I can't find on Joe blog: is change of variable
> subtype inside 'if instance' statement
> I. e. patterns look:
> if (x instanceof something)
> {
>  something sx = (something)x;
> }
> And proposal tell type 'x' as 'something' inside dominate if block.
> Are anybody remember such proposal or it's was my fantasy ?
> </BTW>
>
> Some results:
>
> For jetty6_11: (web server)
> byte literal    :       52
> elvis   :       43
> instanceof switch       :       8
> loop with remove        :       0
> multi catch     :       22
> string in switch        :       19
> Files:187
>
> For gwt-user (google ajax library)
> byte literal    :       2
> elvis   :       30
> instanceof switch       :       6
> loop with remove        :       5
> multi catch     :       9
> string in switch        :       10
> Files:920
>
> For openjdk-jdk part: (system library)
> byte literal    :       1245
> elvis   :       725
> instanceof switch       :       252
> loop with remove        :       61
> multi catch     :       349
> string in switch        :       380
> Files:7375
>
>
>
> If you want to play with checks - most easy way is get special modified
> source
> distributive of JavaChecker, which I published as 2.5.0p0 and run it, i.e.
> (assuming you on Unix console)
>
> retrive distributive:
>
>  wget
> http://datacenter.gradsoft.ua/public.repository/ua.gradsoft/javachecker/installations/JavaCheckerSourceInstaller-2.5.0p0.jar
>
> run installer:
> java -jar JavaCheckerSourceInstaller-2.5.0p0.jar
>  (install one from UI)
>
> cd <where-you-install-javacheker>
>
> vi build-check-external.xml, look at few last tasks at end
>
> vi check-external.properties
>
> add own task and run one, as example:
> ant -f build-check-external.xml check-coin-openjdk
>
> Note, that speed of JavaChecker is far from ideal: openJDK-jdk
>  processed near 50 minutes, so be patient ;)
>
> Hope, this information can be useful, as one (and not main) of  sources.
>
> Regards !
>
>
>
>
>   



From paul.martin at gmail.com  Wed Apr 15 15:54:04 2009
From: paul.martin at gmail.com (paul.martin at gmail.com)
Date: Wed, 15 Apr 2009 22:54:04 +0000
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <49E3ECFC.6000002@sun.com>
Message-ID: <001485f6307408a1e304679fd349@google.com>

(In reply to "On Apr 14, 2009 2:5am, Joe Darcy <Joe.Darcy at sun.com> wrote:")

Hi,

Some of this discussion is frustrating. I think that to say that "the list  
received few serious actual proposals" is unfair, at least in terms of the  
enthusiasm of the discussions, and in terms of the criticism of the  
proposals themselves. I also don't remember seeing many requests for  
further detail in discussions about proposals, so it is unfair to criticise  
their "degree of thoroughness" after the process has closed. Further detail  
(including prototypes) could always have been provided where necessary,  
though in most cases I don't think that this was required - the extra  
detail would be most useful when taking selected proposals further on in  
the process, but that detail would not necessarily be required when making  
that selection.

Some proposals were effectively repeating RFEs, but without knowing why you  
didn't include them on your initial candidate list we cannot know whether  
raising them as proposals is actually justified (maybe you missed an  
important use case). For example my proposal on named parameters does have  
a relevant bug: 6444738 (which admittedly I did not mention, though I did  
reference another), which has an evaluation comment of "We should do this  
for 7; parameter names are also needed for keyword parameters". Named  
parameters were even on the slides at a recent (March) Sun Java  
presentation in London, but they don't now seem to be on the cards for Java  
7. My proposal was really to ask why not, but I don't think that question  
was answered.

I am also not suggesting that the selected proposals will not be useful and  
should not be chosen - they are all good choices (though they mainly ease  
syntax rather than increasing the capabilities of the language). However, I  
would like to know why other proposals were not selected, but this only  
needs to be at a high level. For example, the following categorisation  
would work for me: 'Good' (the right size, but not as good as the selected  
proposals), 'out of scope' for Coin (good, but too hard), 'rejected' (we  
won't ever do this - though a brief reason would help), and 'not  
understood'.

Much of this is probably just miscommunication and misunderstanding: after  
looking through your posts and presentations in the light of this  
discussion, I can see that you probably did want fewer and more detailed  
proposals, but that wasn't clear (to me at least) in your weekly blog posts  
and comments on the proposals.

Hopefully this all makes sense. I really did enjoy the process, and  
appreciate the effort that you put in to make it happen. But maybe a  
little 'finessing' of your conclusions would keep me happy!

Regards,

Paul


From reinier at zwitserloot.com  Wed Apr 15 17:03:09 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Thu, 16 Apr 2009 02:03:09 +0200
Subject: Splitting the meat of a proposal from the trivial details.
In-Reply-To: <001485f6307408a1e304679fd349@google.com>
References: <001485f6307408a1e304679fd349@google.com>
Message-ID: <906692CA-71E0-4869-9591-076C05A15420@zwitserloot.com>

Actually, Joe has repeatedly turned down proposals because they were  
laughably incomplete, and Neal Gafter had gone through the trouble of  
writing up an example proposal before March 1st that showed most of  
the concerns that were nonetheless completely skipped in most  
proposals (such as definitive assignment rules).

However - I still mostly agree with your sentiment. The amount of work  
and detail required before a proposal was considered 'complete' was  
considerable, and yet the vast majority of proposals (even with the  
neccessary detail) were clearly going to be rejected (only 4 to 5,  
tops, that's been said many times).

This provides a dilemma: Put in all that effort for not much to show  
for it?

I felt that many (but not all) of the proposals essentially had enough  
detail in them to allow you to figure out if they were a good idea or  
not. If there had been another month, such a half-finished proposal  
could have been pointed out as 'would be on the shortlist, if only  
someone went through the effort of going through all the details,  
including writing down something like the definitive assignment rules.  
I think we'd have seen more useful discussion on proposals, and waste  
less time on trivialities, if it had been set up like that.

For example, I was going to write up my plan to allow named parameters  
in method signatures, but in the end decided against it, because  
writing out the full JLS spec including chapter and verse would have  
been too much effort, compared to the tiny chance it would have been  
considered worthy for coin. If, however, there was a separate pre- 
proposal phase, I could have easily written up the gist of the  
proposal, many examples, and ample support that my proposal would be  
backwards and migration compatible, would not lead to much confusion,  
and would not be amiguous. If, then, the proposal would be accepted as  
'likely good for java, -if- fully specced and no surprises turn up',  
I'd gladly have taken the time to write it out in excruciating detail,  
and cook up a prototype.


This Project Coin was pressed for time, so much more than a month just  
wasn't on the table, but for next time, I suggest smearing out coin  
across 3 months:

Day 1-30: Pre-proposal Month.

A Pre-proposal discusses the feature at hand, what it'll solve, ample  
example code of real-life situations so we can all assess the utility  
and impact of the change, and much discussion about backwards and  
migration compatibility, how confusing the feature may be in certain  
situations (a.k.a. the java puzzler factor), and if the proposal is  
ambiguous. This is not the time to complain about potential problems  
and ambiguities for which the complainer-to-be can already think of a  
fairly simple solution by himself - this is about fundamental issues  
with a proposal, and the merits of each. Not for sweating the small  
stuff.

The deadline for submitting a pre-proposal is day 20 (to give pre- 
proposals submitted on the deadline at least 10 days to be discussed).

Day 31-37: Rest week.

Day 38-45: Pre-proposal sorting. Be it via polling or internal  
decision by sun or a combination of the two, this is the time to sort  
pre-proposals into 'no way', and 'on the shortlist'.

Day 45-90: Prototype and spec month.

This is the time for the shortlisted proposals to be fully specced  
(with chapter and verse of the JLS as well as rewrites for the JLS),  
and preferably a working prototype.  The deadline for delivering the  
spec+prototype is day 75, to give the list time to analyse all  
proposals, even those submitted on the deadline. This IS the time to  
name rare and easily solved nitpicks, ambiguities, no matter how  
trivial, and other ommissions. At this point the discussion should  
turn towards implementation detail, and not so much the merits (all  
pre-proposals on the shortlist have already been deemed as having the  
merit to make it, so if you don't like a proposal that's on the  
shortlist, or you do like one that isn't, tough - the decision has  
been made, move on). Of course, proposals that end up being more  
complicated than they appeared to be in the pre-proposal phase can  
still be discussed on merit (is it STILL worth it, now that we figured  
out it's going to be this complicated?). I would be tempted to say  
that ONLY shortlisted pre-proposals should even be considered in this  
phase, as to keep down unrelated chatter on pet projects.

Aftermath: The shortlist is amended: Those on the shortlist that were  
unsifficiently specced out are tossed, regardless of merit (if it was  
such a good idea, ostensibly someone would have written it up  
properly). Those that are fully specced are reconsidered again.  
Preferably soon after the end of the 3 month period, the semi-official  
list is released. (semi-official as in: These are the new language  
features, barring unexpected surprises when we implement these into  
the JLS and javac).



How some of the proposals would have gone, if the above flow had been  
used for coin:

ARM - posted early in the pre-proposal phase, all the discussion we've  
seen, without the need for Josh to keep updating the proposal in all  
that detail. Somewhere around today, Josh or someone else coordinating  
with Josh, starts working on a prototype. 2 months from now, with a  
complete spec and prototype, ARM is officially accepted into java7  
(well, if there hadn't been JSR issues).

Neal's expression blocks - little discussion (we haven't seen much in  
coin either), but nobody can come up with serious issues either, and  
neal adequatedly shows that the block proposal is unlikely to cause  
serious issues. For whatever reason (denying pre-proposals should not  
need a lengthy defense), the pre-proposal is not put on the shortlist,  
and that's where it ends.

  --Reinier Zwitserloot



On Apr 16, 2009, at 00:54, paul.martin at gmail.com wrote:

> (In reply to "On Apr 14, 2009 2:5am, Joe Darcy <Joe.Darcy at sun.com>  
> wrote:")
>
> Hi,
>
> Some of this discussion is frustrating. I think that to say that  
> "the list
> received few serious actual proposals" is unfair, at least in terms  
> of the
> enthusiasm of the discussions, and in terms of the criticism of the
> proposals themselves. I also don't remember seeing many requests for
> further detail in discussions about proposals, so it is unfair to  
> criticise
> their "degree of thoroughness" after the process has closed. Further  
> detail
> (including prototypes) could always have been provided where  
> necessary,
> though in most cases I don't think that this was required - the extra
> detail would be most useful when taking selected proposals further  
> on in
> the process, but that detail would not necessarily be required when  
> making
> that selection.
>
> Some proposals were effectively repeating RFEs, but without knowing  
> why you
> didn't include them on your initial candidate list we cannot know  
> whether
> raising them as proposals is actually justified (maybe you missed an
> important use case). For example my proposal on named parameters  
> does have
> a relevant bug: 6444738 (which admittedly I did not mention, though  
> I did
> reference another), which has an evaluation comment of "We should do  
> this
> for 7; parameter names are also needed for keyword parameters". Named
> parameters were even on the slides at a recent (March) Sun Java
> presentation in London, but they don't now seem to be on the cards  
> for Java
> 7. My proposal was really to ask why not, but I don't think that  
> question
> was answered.
>
> I am also not suggesting that the selected proposals will not be  
> useful and
> should not be chosen - they are all good choices (though they mainly  
> ease
> syntax rather than increasing the capabilities of the language).  
> However, I
> would like to know why other proposals were not selected, but this  
> only
> needs to be at a high level. For example, the following categorisation
> would work for me: 'Good' (the right size, but not as good as the  
> selected
> proposals), 'out of scope' for Coin (good, but too hard),  
> 'rejected' (we
> won't ever do this - though a brief reason would help), and 'not
> understood'.
>
> Much of this is probably just miscommunication and misunderstanding:  
> after
> looking through your posts and presentations in the light of this
> discussion, I can see that you probably did want fewer and more  
> detailed
> proposals, but that wasn't clear (to me at least) in your weekly  
> blog posts
> and comments on the proposals.
>
> Hopefully this all makes sense. I really did enjoy the process, and
> appreciate the effort that you put in to make it happen. But maybe a
> little 'finessing' of your conclusions would keep me happy!
>
> Regards,
>
> Paul
>



From neal at gafter.com  Wed Apr 15 17:33:55 2009
From: neal at gafter.com (Neal Gafter)
Date: Wed, 15 Apr 2009 17:33:55 -0700
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <001485f6307408a1e304679fd349@google.com>
References: <49E3ECFC.6000002@sun.com>
	<001485f6307408a1e304679fd349@google.com>
Message-ID: <15e8b9d20904151733o32920606ve31c5ade09b6c4fd@mail.gmail.com>

On Wed, Apr 15, 2009 at 3:54 PM, <paul.martin at gmail.com> wrote:
> Some of this discussion is frustrating. I think that to say that "the list
> received few serious actual proposals" is unfair, at least in terms of the
> enthusiasm of the discussions, and in terms of the criticism of the
> proposals themselves.

Paul-

Specificity is needed to determine if a proposal is simple enough for
project Coin.  I didn't bother commenting on proposals that had only a
hint of a specification.  An RFE - requesting that a problem be solved
(even if it suggests a direction for the solution) - is far from a
proposal for a specific solution.  Evaluating an RFE to the needed
level of detail would require we not just comment on the problem
space, but evaluate the entire solution space and comment on the best
of the solutions we can imagine.  The proposer was supposed to do
that, and describe precisely one selected solution.  I know that is a
lot of work and may require specialized skills.  That is why the
readers of a proposal cannot be expected to do it.

I didn't bother commenting on some proposals because I just didn't see
much benefit compared to the effort.

As much fun as it is to discuss language design, this list is not
really the best place for that design to take place.  If a lot of
discussion is needed to move a proposal forward now, that is a sign
that the proposal is complex, or imprecise, or immature and likely to
require extensive discussion and refinement in the expert group.  Any
of these suggests that the proposal would probably require more effort
than is appropriate for project Coin.

Regards,
Neal


From Joe.Darcy at Sun.COM  Wed Apr 15 21:35:24 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Wed, 15 Apr 2009 21:35:24 -0700
Subject: Splitting the meat of a proposal from the trivial details.
In-Reply-To: <906692CA-71E0-4869-9591-076C05A15420@zwitserloot.com>
References: <001485f6307408a1e304679fd349@google.com>
	<906692CA-71E0-4869-9591-076C05A15420@zwitserloot.com>
Message-ID: <49E6B58C.7020107@sun.com>

Reinier Zwitserloot wrote:
> Actually, Joe has repeatedly turned down proposals because they were  
> laughably incomplete, 

Quite so!

> and Neal Gafter had gone through the trouble of  
> writing up an example proposal before March 1st that showed most of  
> the concerns that were nonetheless completely skipped in most  
> proposals (such as definitive assignment rules).
>   

Part of my goal of sending in the strings in switch proposal (first 
post!) was to demonstrate the sort of details that can come up even in 
the simplest of changes.

> However - I still mostly agree with your sentiment. The amount of work  
> and detail required before a proposal was considered 'complete' was  
> considerable, and yet the vast majority of proposals (even with the  
> neccessary detail) were clearly going to be rejected (only 4 to 5,  
> tops, that's been said many times).
>   

Yes, the limited size of the set of possible proposals was established 
before the call for proposals started.

However, the time required to write up even a fairly detailed proposal, 
say 8 hours, pales in comparison to the possible effort needed to fully 
implement a proposal.

For example, implementing just the *single method* Class.isEnum probably 
took around five hours of effort during JDK 5.  While this method is 
only two lines long, three tries were needed before getting the right 
two lines; more detail on why this happened is described in:
http://blogs.sun.com/darcy/entry/so_you_want_to_change

> This provides a dilemma: Put in all that effort for not much to show  
> for it?
>   

As I've stated before, Project Coin is a participatory process, which 
means people have the opportunity to participate in the work of a 
proposal too :-)

> I felt that many (but not all) of the proposals essentially had enough  
> detail in them to allow you to figure out if they were a good idea or  
> not. If there had been another month, such a half-finished proposal  
> could have been pointed out as 'would be on the shortlist, if only  
> someone went through the effort of going through all the details,  
> including writing down something like the definitive assignment rules.  
> I think we'd have seen more useful discussion on proposals, and waste  
> less time on trivialities, if it had been set up like that.
>   

While some iteration and refinement of proposals is fine and expected, 
details are not trivialities.  Seemingly small details can make a 
difference and having some set of details available early allows better 
decisions to be made.

> For example, I was going to write up my plan to allow named parameters  
> in method signatures, but in the end decided against it, because  
> writing out the full JLS spec including chapter and verse would have  
> been too much effort, compared to the tiny chance it would have been  
> considered worthy for coin. If, however, there was a separate pre- 
> proposal phase, I could have easily written up the gist of the  
> proposal, many examples, and ample support that my proposal would be  
> backwards and migration compatible, would not lead to much confusion,  
> and would not be amiguous. If, then, the proposal would be accepted as  
> 'likely good for java, -if- fully specced and no surprises turn up',  
> I'd gladly have taken the time to write it out in excruciating detail,  
> and cook up a prototype.
>
>
> This Project Coin was pressed for time, so much more than a month just  
> wasn't on the table, but for next time, I suggest smearing out coin  
> across 3 months:
>   

The future existence of what would be known of Project Coin was 
announced on December 8, 2008 
(http://blogs.sun.com/darcy/entry/small_language_changes_jdk_7).  This 
included an overview of the coming call for proposals and a link to "So 
you want to change the Java Programming Language...", whose content 
served as the skeleton for the later proposal form.  The proposal form 
was published in January 27, 2009 
(http://blogs.sun.com/darcy/entry/project_coin) and the mailing list 
started a month later, February 27, 2009.

So there was a three month period before the call for proposals 
officially got underway, and a month after the form was published but 
before a proposal could be submitted, where interested parties could 
think about proposal ideas and possibly implement them, guided by the 
published criteria for the effort.

There were a few inquiries to the list to ask for help drafting a 
proposal and some "pre-proposals" sent in to get a reading on whether a 
proposal topic would be smiled upon, both of which are good, on-topic 
uses of the list!  However, after my unfavorable assessment of the 
"Source and Encoding keyword" pre-proposal 
(http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000298.html) 
was sent to the list, people choose to continue the discussion for a 
time.  Some continued discussion is fine, but people who send in 
proposals or pre-proposals don't to tend to give up right away ;-)  To 
reiterate terms of roles and responsibilities here,

"Especially with the maturity of the Java platform, the onus is on the 
proposer to convince that a language change should go in; the onus is 
not to prove the change should stay out."
http://blogs.sun.com/darcy/entry/criteria_for_desirable_small_language
December 23, 2008

Having thought through the details is one way to be more convincing.

-Joe



From Joe.Darcy at Sun.COM  Wed Apr 15 23:00:23 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Wed, 15 Apr 2009 23:00:23 -0700
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <15e8b9d20904151733o32920606ve31c5ade09b6c4fd@mail.gmail.com>
References: <49E3ECFC.6000002@sun.com>
	<001485f6307408a1e304679fd349@google.com>
	<15e8b9d20904151733o32920606ve31c5ade09b6c4fd@mail.gmail.com>
Message-ID: <49E6C977.5080702@sun.com>

Neal Gafter wrote:
> On Wed, Apr 15, 2009 at 3:54 PM, <paul.martin at gmail.com> wrote:
>   
>> Some of this discussion is frustrating. I think that to say that "the list
>> received few serious actual proposals" is unfair, at least in terms of the
>> enthusiasm of the discussions, and in terms of the criticism of the
>> proposals themselves.
>>     
>
> Paul-
>
> Specificity is needed to determine if a proposal is simple enough for
> project Coin.  I didn't bother commenting on proposals that had only a
> hint of a specification.  An RFE - requesting that a problem be solved
> (even if it suggests a direction for the solution) - is far from a
> proposal for a specific solution.  Evaluating an RFE to the needed
> level of detail would require we not just comment on the problem
> space, but evaluate the entire solution space and comment on the best
> of the solutions we can imagine.  The proposer was supposed to do
> that, and describe precisely one selected solution.  I know that is a
> lot of work and may require specialized skills.  That is why the
> readers of a proposal cannot be expected to do it.
>   

Moreover, the set of people currently with these skills is small and it 
would be helpful if this set grew in size.  The Project Coin proposal 
form and other material was intended to give guidance on all that can be 
required as part of the task of growing the Java language so that more 
people can participate now and going forward.  Discussions on the list 
provide a public, archived record of the proposals, their analysis, and 
decision making to better inform current and future discussions.

Certainly merely sending an incomplete proposal to the list should in no 
way be expected to oblige others to undertake the hard task of analyzing 
and completing the work!

-Joe


From Ruslan at Shevchenko.Kiev.UA  Wed Apr 15 23:27:08 2009
From: Ruslan at Shevchenko.Kiev.UA (Ruslan Shevchenko)
Date: Thu, 16 Apr 2009 09:27:08 +0300 (EEST)
Subject: scripts and results (was Helping to find the usefulness of a 
	proposal)
In-Reply-To: <49E5F020.7060508@gmx.de>
References: <60287e9e1530b3e1ae49976316e8dc57.squirrel@wmail.gradsoft.ua>
	<49E5F020.7060508@gmx.de>
Message-ID: <114ad93adfd2eb30f7ecd1388b69b1be.squirrel@wmail.gradsoft.ua>

> Hi Ruslan,
>
> I would like to see the results for
>
>      "objects and expressions in switch"
>
> which includes:
> - string in switch
> - instanceof switch
>
> I guess a very big chunk of all if-else if-structures would be covered by:
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001182.html
>

Ok, I will alloc some time during next week-end for more patterns and
statistics and will try include this one.  This will some 'near' refinemed
of proposal, becouse original proposal does not define what is 'leftPart'
and 'rightPart' of Java expression in formal way [this is not so trivial,
as expected. For example what left part will be in function expressions:
'this' or nothing ?. How we split chained expressions on left and right ?]
 For this reasons, I guess probability that this proposal will seen
seriously is very low.


(Second change which I plan: add statistics about relative number of
chainged construction/number of  all such constructions).




> A n y   C A P A C I T Y   t o   a d d   t h i s  p a t t e r n   t o   y
> o u r   s c r i p t ? ?
>
> As I argued before, I'm against the current syntax of the "string in
> switch"-proposal, as it weakens switch..case semantics for identity, and
> it encumbers later enhancements for the future. See:
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001328.html.
>
> - Ulf
>
>
>
> Am 07.04.2009 02:33, Ruslan Shevchenko schrieb:
>>  Good day,
>>
>> Few days ago Stephan give idea about writing simple script, which
>>  count amount of possible-optimizations of existing code.
>>
>> So, I wrote few checks for some of such entries. They count
>> low bound of number of code patterns, which can be optimized with
>> some of coin proposal and situated on distinct source lines.
>>
>> I'm afraid that information, which come from count of such code patterns
>> can give incorrect direction:  when we have such patterns in code,
>> it's means that problem is not so big and we can easy live with one.
>>  Big language problems solved (or not) in non-trivial way, when we have
>> no
>> common (may be ugly) workaround.
>> For example. in Java we rare will see BigDecimal.add()  because it is
>> not
>> easy to work with BigDecimals, instead people work with double and have
>> troubles
>> with floating points rounding issues (see
>> http://www.ddj.com/java/184405721)).
>> Yet one example - choosing another language for implementing
>> db-intensive
>> parts of projects.
>>
>> Ok, you warned;  data still can be interesting:
>>
>> Checked patterns was:
>>   string in switch
>>   instanceof switch
>>   byte literals
>>   multi catch
>>   loop by iterator, with call remove inside loop
>>
>>  (if you want include other checks, you can add one at
>>  etc/checkers_coin.def or ask me [but without any warranty])
>>
>> <BTW>
>> Exists one proposal, which I can't find on Joe blog: is change of
>> variable
>> subtype inside 'if instance' statement
>> I. e. patterns look:
>> if (x instanceof something)
>> {
>>  something sx = (something)x;
>> }
>> And proposal tell type 'x' as 'something' inside dominate if block.
>> Are anybody remember such proposal or it's was my fantasy ?
>> </BTW>
>>
>> Some results:
>>
>> For jetty6_11: (web server)
>> byte literal    :       52
>> elvis   :       43
>> instanceof switch       :       8
>> loop with remove        :       0
>> multi catch     :       22
>> string in switch        :       19
>> Files:187
>>
>> For gwt-user (google ajax library)
>> byte literal    :       2
>> elvis   :       30
>> instanceof switch       :       6
>> loop with remove        :       5
>> multi catch     :       9
>> string in switch        :       10
>> Files:920
>>
>> For openjdk-jdk part: (system library)
>> byte literal    :       1245
>> elvis   :       725
>> instanceof switch       :       252
>> loop with remove        :       61
>> multi catch     :       349
>> string in switch        :       380
>> Files:7375
>>
>>
>>
>> If you want to play with checks - most easy way is get special modified
>> source
>> distributive of JavaChecker, which I published as 2.5.0p0 and run it,
>> i.e.
>> (assuming you on Unix console)
>>
>> retrive distributive:
>>
>>  wget
>> http://datacenter.gradsoft.ua/public.repository/ua.gradsoft/javachecker/installations/JavaCheckerSourceInstaller-2.5.0p0.jar
>>
>> run installer:
>> java -jar JavaCheckerSourceInstaller-2.5.0p0.jar
>>  (install one from UI)
>>
>> cd <where-you-install-javacheker>
>>
>> vi build-check-external.xml, look at few last tasks at end
>>
>> vi check-external.properties
>>
>> add own task and run one, as example:
>> ant -f build-check-external.xml check-coin-openjdk
>>
>> Note, that speed of JavaChecker is far from ideal: openJDK-jdk
>>  processed near 50 minutes, so be patient ;)
>>
>> Hope, this information can be useful, as one (and not main) of  sources.
>>
>> Regards !
>>
>>
>>
>>
>>
>
>




From markmahieu at googlemail.com  Wed Apr 15 23:40:43 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Thu, 16 Apr 2009 07:40:43 +0100
Subject: Some notes on Elvis and Other Null-Safe Operators
In-Reply-To: <171AADE5-112F-43EB-AEED-4E502EE0914E@googlemail.com>
References: <171AADE5-112F-43EB-AEED-4E502EE0914E@googlemail.com>
Message-ID: <6BDB603A-7DCB-4621-9691-E31566265C32@googlemail.com>

One more thought regarding Elvis and friends.  In the code-base I'm  
currently working on, I keep seeing code like the following:

	Map<Key, Set<Foo>> map = ...

	if (map != null) {
		Set<Foo> fooSet = map.get(key);
		if (fooSet != null) {
			for (Foo foo : fooSet) {
				...
			}
		}
	}

which can be 'simplified' in a number of ways, for example with the  
liberal sprinkling of a couple of null-transforming methods:

	Set<Foo> fooSet = emptyIfNull(map).get(key);
	for (Foo foo : emptyIfNull(fooSet)) {
		...
	}

Alternatively, with Elvis etc it could be written like this:

	for (Foo foo : map?.get(key) ?: Collections.<Foo>emptySet()) {
		...
	}

Which doesn't seem like much of an improvement, to me.  But I keep  
thinking that, in the context of this proposal, a null-safe form of  
the foreach loop might not be so bad:

	for (Foo foo :? map?.get(key)) {
		...
	}

I seem to recall that kind of example being talked about fairly  
extensively during JSR-201, but I think the discussion then was  
around whether foreach should be 'null-safe' by default.  Perhaps  
it's an example of trying to fit the proposal to the use-case, though.


Mark



From paul.martin at gmail.com  Thu Apr 16 01:35:20 2009
From: paul.martin at gmail.com (Paul Martin)
Date: Thu, 16 Apr 2009 09:35:20 +0100
Subject: Helping to find the usefulness of a proposal
In-Reply-To: <49E6C977.5080702@sun.com>
References: <49E3ECFC.6000002@sun.com>
	<001485f6307408a1e304679fd349@google.com>
	<15e8b9d20904151733o32920606ve31c5ade09b6c4fd@mail.gmail.com>
	<49E6C977.5080702@sun.com>
Message-ID: <4ce75f920904160135m66750f12ja9e85c134082c554@mail.gmail.com>

Hi,

Joe, Neal, and Reinier - many thanks for your replies.  I think that I
do understand the process much better now, and appreciate its goals.
I had actually considered just asking the question about named
parameters and/or just submitting a pre-proposal, which in hindsight
would probably have been more useful (maybe I'll update the existing
related bugs if necessary).

In particular, I hadn't really considered the following idea, but can
see that it is a valuable result of the process:

> ... Discussions on the list provide a
> public, archived record of the proposals, their analysis, and decision
> making to better inform current and future discussions.

Being able to see why changes were made and what was considered is
definitely a good thing.

Once again, thanks for your replies.

Regards,

Paul


From brucechapman at paradise.net.nz  Thu Apr 16 03:12:21 2009
From: brucechapman at paradise.net.nz (Bruce Chapman)
Date: Thu, 16 Apr 2009 22:12:21 +1200
Subject: PROPOSAL: Underscores in numbers
In-Reply-To: <11482659.1238468832504.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
References: <11482659.1238468832504.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
Message-ID: <49E70485.5050100@paradise.net.nz>

I am just doing some work (in kijaro) building prototype compiler for my 
integer literal proposals, and this proposal, and during testing found a 
wee bug in this spec.


> long alsoMaxLong = 9_223_372_036_854_775_808L;
that particular literal is only valid as the right hand side of a unary 
minus. The last digit should be changed to a '7'.

Will post a link to the prototype in the next few days now that I have 
everything working. I still need to create something that is relatively 
easy to download and deploy.

Bruce


From reinier at zwitserloot.com  Thu Apr 16 03:51:28 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Thu, 16 Apr 2009 12:51:28 +0200
Subject: Splitting the meat of a proposal from the trivial details.
In-Reply-To: <49E6B58C.7020107@sun.com>
References: <001485f6307408a1e304679fd349@google.com>
	<906692CA-71E0-4869-9591-076C05A15420@zwitserloot.com>
	<49E6B58C.7020107@sun.com>
Message-ID: <059B6404-A031-4340-ADC8-92BDBFDB2719@zwitserloot.com>

If Coin did effectively take 3 months, that's all the more reason to  
open up coin-dev for the complete 3 month timespan!

By restricting discussion to the shortlist after a month and a week, a  
lot of interesting but not relevant chatter about proposals that  
definitely won't make the grade anyway can be weeded out. At times I  
felt the coin discussion turned needlessly specific for early stage  
proposals, and yet for other proposals, the idle banter on vague  
proposals was distracting from finalizing the details on something  
like ARM.


  --Reinier Zwitserloot



On Apr 16, 2009, at 06:35, Joseph D. Darcy wrote:

> Reinier Zwitserloot wrote:
>> Actually, Joe has repeatedly turned down proposals because they  
>> were  laughably incomplete,
>
> Quite so!
>
>> and Neal Gafter had gone through the trouble of  writing up an  
>> example proposal before March 1st that showed most of  the concerns  
>> that were nonetheless completely skipped in most  proposals (such  
>> as definitive assignment rules).
>>
>
> Part of my goal of sending in the strings in switch proposal (first  
> post!) was to demonstrate the sort of details that can come up even  
> in the simplest of changes.
>
>> However - I still mostly agree with your sentiment. The amount of  
>> work  and detail required before a proposal was considered  
>> 'complete' was  considerable, and yet the vast majority of  
>> proposals (even with the  neccessary detail) were clearly going to  
>> be rejected (only 4 to 5,  tops, that's been said many times).
>>
>
> Yes, the limited size of the set of possible proposals was  
> established before the call for proposals started.
>
> However, the time required to write up even a fairly detailed  
> proposal, say 8 hours, pales in comparison to the possible effort  
> needed to fully implement a proposal.
>
> For example, implementing just the *single method* Class.isEnum  
> probably took around five hours of effort during JDK 5.  While this  
> method is only two lines long, three tries were needed before  
> getting the right two lines; more detail on why this happened is  
> described in:
> http://blogs.sun.com/darcy/entry/so_you_want_to_change
>
>> This provides a dilemma: Put in all that effort for not much to  
>> show  for it?
>>
>
> As I've stated before, Project Coin is a participatory process,  
> which means people have the opportunity to participate in the work  
> of a proposal too :-)
>
>> I felt that many (but not all) of the proposals essentially had  
>> enough  detail in them to allow you to figure out if they were a  
>> good idea or  not. If there had been another month, such a half- 
>> finished proposal  could have been pointed out as 'would be on the  
>> shortlist, if only  someone went through the effort of going  
>> through all the details,  including writing down something like the  
>> definitive assignment rules.  I think we'd have seen more useful  
>> discussion on proposals, and waste  less time on trivialities, if  
>> it had been set up like that.
>>
>
> While some iteration and refinement of proposals is fine and  
> expected, details are not trivialities.  Seemingly small details can  
> make a difference and having some set of details available early  
> allows better decisions to be made.
>
>> For example, I was going to write up my plan to allow named  
>> parameters  in method signatures, but in the end decided against  
>> it, because  writing out the full JLS spec including chapter and  
>> verse would have  been too much effort, compared to the tiny chance  
>> it would have been  considered worthy for coin. If, however, there  
>> was a separate pre- proposal phase, I could have easily written up  
>> the gist of the  proposal, many examples, and ample support that my  
>> proposal would be  backwards and migration compatible, would not  
>> lead to much confusion,  and would not be amiguous. If, then, the  
>> proposal would be accepted as  'likely good for java, -if- fully  
>> specced and no surprises turn up',  I'd gladly have taken the time  
>> to write it out in excruciating detail,  and cook up a prototype.
>>
>>
>> This Project Coin was pressed for time, so much more than a month  
>> just  wasn't on the table, but for next time, I suggest smearing  
>> out coin  across 3 months:
>>
>
> The future existence of what would be known of Project Coin was  
> announced on December 8, 2008 (http://blogs.sun.com/darcy/entry/small_language_changes_jdk_7 
> ).  This included an overview of the coming call for proposals and a  
> link to "So you want to change the Java Programming Language...",  
> whose content served as the skeleton for the later proposal form.   
> The proposal form was published in January 27, 2009 (http://blogs.sun.com/darcy/entry/project_coin 
> ) and the mailing list started a month later, February 27, 2009.
>
> So there was a three month period before the call for proposals  
> officially got underway, and a month after the form was published  
> but before a proposal could be submitted, where interested parties  
> could think about proposal ideas and possibly implement them, guided  
> by the published criteria for the effort.
>
> There were a few inquiries to the list to ask for help drafting a  
> proposal and some "pre-proposals" sent in to get a reading on  
> whether a proposal topic would be smiled upon, both of which are  
> good, on-topic uses of the list!  However, after my unfavorable  
> assessment of the "Source and Encoding keyword" pre-proposal (http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000298.html 
> ) was sent to the list, people choose to continue the discussion for  
> a time.  Some continued discussion is fine, but people who send in  
> proposals or pre-proposals don't to tend to give up right away ;-)   
> To reiterate terms of roles and responsibilities here,
>
> "Especially with the maturity of the Java platform, the onus is on  
> the proposer to convince that a language change should go in; the  
> onus is not to prove the change should stay out."
> http://blogs.sun.com/darcy/entry/criteria_for_desirable_small_language
> December 23, 2008
>
> Having thought through the details is one way to be more convincing.
>
> -Joe
>



From scolebourne at joda.org  Sat Apr 18 03:33:31 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Sat, 18 Apr 2009 11:33:31 +0100
Subject: Some notes on Elvis and Other Null-Safe Operators
In-Reply-To: <6BDB603A-7DCB-4621-9691-E31566265C32@googlemail.com>
References: <171AADE5-112F-43EB-AEED-4E502EE0914E@googlemail.com>
	<6BDB603A-7DCB-4621-9691-E31566265C32@googlemail.com>
Message-ID: <49E9AC7B.3010509@joda.org>

Mark Mahieu wrote:
> Which doesn't seem like much of an improvement, to me.  But I keep  
> thinking that, in the context of this proposal, a null-safe form of  
> the foreach loop might not be so bad:
> 
> 	for (Foo foo :? map?.get(key)) {
> 		...
> 	}

I certainly think thats an interesting idea.

However, having a null list is something that rarely comes up in the 
code I write. I think thats because I always return an empty list from 
methods and never null (something that is definitely good practice).

Where the null-safe operators come in is in handling object model 
structure such as a bean holding an optional value (String/Integer/Date 
etcc), or a bean holding another optional bean (person holding optional 
spouse). In these cases, holding null to represent the absence of data 
is a valid design choice.

Stephen


From markmahieu at googlemail.com  Sat Apr 18 12:17:07 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Sat, 18 Apr 2009 20:17:07 +0100
Subject: Some notes on Elvis and Other Null-Safe Operators
In-Reply-To: <49E9AC7B.3010509@joda.org>
References: <171AADE5-112F-43EB-AEED-4E502EE0914E@googlemail.com>
	<6BDB603A-7DCB-4621-9691-E31566265C32@googlemail.com>
	<49E9AC7B.3010509@joda.org>
Message-ID: <7ED41D61-84A5-4149-82F1-D39333038C21@googlemail.com>


On 18 Apr 2009, at 11:33, Stephen Colebourne wrote:

> Mark Mahieu wrote:
>> Which doesn't seem like much of an improvement, to me.  But I keep
>> thinking that, in the context of this proposal, a null-safe form of
>> the foreach loop might not be so bad:
>>
>> 	for (Foo foo :? map?.get(key)) {
>> 		...
>> 	}
>
> I certainly think thats an interesting idea.
>
> However, having a null list is something that rarely comes up in the
> code I write. I think thats because I always return an empty list from
> methods and never null (something that is definitely good practice).

Yes, if I were writing the code I mentioned I would also consider  
using different data structures entirely, such as:

http://google-collections.googlecode.com/svn/trunk/javadoc/com/google/ 
common/collect/Multimap.html

That's not always an option though.  It would certainly be a fairly  
substantial change in my example.


Mark



From bugeaud at gmail.com  Sat Apr 18 15:15:42 2009
From: bugeaud at gmail.com (Jean-Baptiste Bugeaud)
Date: Sun, 19 Apr 2009 00:15:42 +0200
Subject: SUBMISSION : A second look on "named parameters"
Message-ID: <2dc3bd00904181515o2df0a1d3n3cf5ddd75d58d4ff@mail.gmail.com>

Hi everybody,

Here is an late submission, sorry I missed the initial deadline. If
you think (as I do) that this is a key small change for lots of
improvement, maybe there is still a very small gap to go for JDK7;-)

A proposition including the same goal was introduced in JDK6 JSR but
withdawn in final version. So legacy impact, issues ... should be
already well known by the JDK core team. This second look has tried to
solve all the problems.

Let's go ....

Author(s): Jean-Baptiste BUGEAUD, Paris, France

OVERVIEW :
  FEATURE SUMMARY : Introduce named parameter on methods into the language
  MAJOR ADVANTAGE : Integration with the legacy, fully backward
compatible. Clear paradigm separation.
  MAJOR BENEFIT : Consistent way of naming the parameter help to unify
existing APIs, remove boiler plate core thus simplify object
marshaling and reflection usage (WS, JMX, EJB ...).
  MAJOR DISADVANTAGE : Semantic of static keyword on parameter might
not be clear for beginers
  ALTERNATIVES : Usage of existing bytecode handling lib can expose
the parameter names already, but this leads to dependency [5][6] and
potential security issues. Usage of APT[7] to store parameter names
constraint to a prequirement : apply it to all the code you target.
This is unlikely to happen for JARS you have not created, thus
reducing the potential benefits.

EXAMPLE

SIMPLE EXAMPLE :

(1a) :

class OrderManager{
 public void order(String product, int amount){
  // do the login
 }
}

(1b)

class OrderManager{
 public void order(static String product, static int amount){
  // do the login
 }
}

(2a)
void displayOrderCriteria(){
 Method[] methods = OrderManager.class.getMedthods();
 for (Method m : methods){
  System.out.println("To call :"+m);
  for(String n : m.getParameterNames[]){
   System.out.println("\tYou must provide :"+n);
  }
 }
}

(2b)
void displayOrderCriteria(){
 Method[] methods = OrderManager.class.getMedthods();
 for (Method m : methods){
  System.out.println("To call :"+m);
  for(String n : m.getStaticParameterNames[]){
   System.out.println("\tYou must provide :"+n);
  }
 }
}

ADVANCED EXAMPLE :

(3.1)
package java.lang.annotation

@Documented
@Retention(value = RetentionPolicy.SOURCE)
@Target( { ElementType.METHOD, ElementType.ANNOTATION_TYPE })
 public @interface StaticParameterNames {
};

(3.2)

@Retention(value = RetentionPolicy.RUNTIME)
@Target( { ElementType.METHOD })
@Inside(WebService.class)
@ValidWebOperation
@StaticParameterNames
public @interface WebMethod {
 String operationName() default "";
 String action() default "";
};


(3.3)

@WebService
class LoginManager{
 @WebMethod public void doLogin(String user, char[] password){
  // simply log the user
 }
}

DETAILS

SPECIFICATION :

Historicaly, method's parameter names can be stored in the Java
bytecode using appropriate compiler switch [2]. Although, no standard
API is available to benefit from them they aready. But when compiler
optimisation is set or an obfuscater is enabled, then are no more
available. This is not reliable.

Such inconsistency, along with some other problems, have prevented the
inclusion for JDK6 of previous proposition [3][4].

This proposition of small language change, introduce named parameter
on methods into the language thru the add of a new language paradigm :
static named parameter. At source level, this new kind of parameter is
simply a regular parameter with the modifier static set on it.

As a summary, we will get two kind of parameters in the language :
 - regular named parameter (see method on (1a)) : the legacy, we "keep
the good-old way", parameter might be stored in bytecode depending on
compiler option, no change on language/semantic/compilation
 - static named parameter (see method on (1b)) : a regular named
parameter with a static modifier added, whatever happens (compiler
option, obfuscator, etc) parameter name will always be kept at
bytecode level.

At Java API level, on java.lang.reflec.Method, two new method will
help API implementer to leverage both kind of parameters.
 - String[] getParameterNames()
 - String[] getParameterStaticNames()

IDE would be most interrested into calling the first one. But API
implementer (such as JAXWS for instance) requiring a consistent
behavior could rely on the second. But they could downgrade on the
first one for legacy JAR if they wish so.

Introduction of an annotation StaticParameterNames could also be
leverage by API implementer to include automatic parameter name
storage. This one alone will ease lots of library code. For instance,
in JAXWS (see example 3.3), WebParam are now optional to get a web
service working : WebMethod would be enough as long as JAXWS
implementer apply StaticParameterNames on the WebMethod annotation
(see example 3.2).

COMPILATION :

Static named parameters are compiled the same way of regular named
ones but with addition of the static modifier set on the reference at
the bytecode level and the parameter name parameter kept in the table.
No compiler/optimizer/obfuscator should remove/change the parameter
names at bytecode level on a static named parameter.

Thus, at a higher level, although not taking part of the method
signature (and call resolution), the static named parameter could now
be seen as part of the method contract: changing a static named
parameter's name could have the same impact as renaming a method. This
is the developper resposability to analyze impact of such a change.

If a method is tagged with the annotation (or an inherited annotation)
StaticParameterNames, all its method parameter should be compiled as
if they were static named parameters.

TESTING :

Compile test classes (such as examples 1a & 1b) using compiler with
the feature enable with and without optimization enable (the one that
remove the parameter names on regular named parameters).

For each scenario (with & without optimization) :
Call the reflection API for listing regular named parameters, and
check according to the names that should be returned as per the test
class.
Call the reflection API for listing static named parameters, and check
according to the names that should be returned as per the test class.

LIBRARY SUPPORT :

Two methods must be added to java.lang.relfect.Method :

String[] getParameterNames()

List the parameter names as existing in the bytecode. No guaranty of
reliability is made : can be renamed, removed, added, ...
Array is of the same size of getParameterTypes(), for a given index,
if the corresponding name is not found a null value is returned.

String[] getParameterStaticNames()

List the static parameter names as existing in the bytecode. Those
named are reliable. Any change impact the contract.
Array is of the same size of getParameterTypes(), for a given index,
if the corresponding parameter is not tagged with static modifier, a
null value is returned.


StaticParameterNames (see example 3.1) annotation must be introduced
to indicate to the compiler all parameters of a tagged method are
meant to be static nammed parameters although not tagged with the
static modifier. This anotation can tag other annotation.


OTHER CHANGES:

 Any existing API willing to benefit from this feature, could inherit
from StaticParameterNames but this is out of scope of this proposal.

COMPATIBILITY

MIGRATION :
 Manual migration is done adding static modifier on parameters.
 Automatic migration could be done by APIs leader using the
StaticParameterNames annotation, thus all the existing code base would
be migrated at the next build automatically.


COMPATIBILITY :

 BREAKING CHANGES: no, this is the reason of using static modifier.
 EXISTING PROGRAMS: code using legacy class can benefit from the
getParameterNames(). But getParameterStaticNames() will always return
an array of null values.


REFERENCES

EXISTING BUGS

http://bugs.sun.com/view_bug.do?bug_id=6444738

URL FOR PROTOTYPE

None at this time. Early feasibility check in the native VM coden plus
pure Java code is feasible [5].


[1] http://paulhammant.com/blog/parameter-names-for-java6-question.html
[2] http://java.sun.com/j2se/1.4.2/docs/tooldocs/windows/javac.html
[3] http://weblogs.java.net/blog/mreinhold/archive/2005/12/mustang_release.html
[4] http://blogs.sun.com/mr/entry/java_se_6_public_review
[5] http://paranamer.codehaus.org/
[6] http://www.jroller.com/eu/entry/using_asm_to_read_mathod
[7] http://weblogs.java.net/blog/emcmanus/archive/2006/06/using_annotatio.html


From reinier at zwitserloot.com  Sat Apr 18 17:14:16 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Sun, 19 Apr 2009 02:14:16 +0200
Subject: SUBMISSION : A second look on "named parameters"
In-Reply-To: <2dc3bd00904181515o2df0a1d3n3cf5ddd75d58d4ff@mail.gmail.com>
References: <2dc3bd00904181515o2df0a1d3n3cf5ddd75d58d4ff@mail.gmail.com>
Message-ID: <79191A56-6622-4AFE-A999-02280E1A9CD0@zwitserloot.com>

Your proposal is very incomplete. Three major nits:


A. Did I miss something, or did you totally forget to include an  
example of calling a method with named parameters? Something like:

doLogin(user: "foobar", password: new char[] { 'a', 'b', 'c' });

B. Why static? You might as well have picked 'strictfp' - it's a total  
non-sequitur choice. Re-use of existing keywords is not really a  
panacea; it waters down the anchoring ability of a keyword to  
virtually nothing. I'm not sure if context-sensitive keywords are any  
better, but java7 is already going to have at least one ('module'), so  
don't beat around the bush and just call it 'named'). Could be just  
me, but introducing a change which is not backwards compatible IF you  
have a type that's called 'named' (written just like that, all-lower  
case), is not something I find troublesome in the least. That's very  
ugly code, and a migration tool can fix this easily.

C. You don't mention having default values for parameters, which is  
sort of the point of this exercise (otherwise you really still need  
builders  ; any method that has so many parameters that they need  
names probably needs a builder, and without defaults, not providing  
one and instead relying on named params is just an inferior bandaid to  
your ugly API; to get it right you STILL need to provide a builder.  
If, however, parameters can have defaults, then you no longer need to  
make builders at all).

I suggest you look over the coin-dev mailing list; I entered a rough  
sketch of a named parameters proposal near the end of coin. I never  
wrote it up because I thought of it far too close to the deadline, and  
it's still of such high impact that I doubt it would pass muster for  
coin.


  --Reinier Zwitserloot



On Apr 19, 2009, at 00:15, Jean-Baptiste Bugeaud wrote:

> Hi everybody,
>
> Here is an late submission, sorry I missed the initial deadline. If
> you think (as I do) that this is a key small change for lots of
> improvement, maybe there is still a very small gap to go for JDK7;-)
>
> A proposition including the same goal was introduced in JDK6 JSR but
> withdawn in final version. So legacy impact, issues ... should be
> already well known by the JDK core team. This second look has tried to
> solve all the problems.
>
> Let's go ....
>
> Author(s): Jean-Baptiste BUGEAUD, Paris, France
>
> OVERVIEW :
>  FEATURE SUMMARY : Introduce named parameter on methods into the  
> language
>  MAJOR ADVANTAGE : Integration with the legacy, fully backward
> compatible. Clear paradigm separation.
>  MAJOR BENEFIT : Consistent way of naming the parameter help to unify
> existing APIs, remove boiler plate core thus simplify object
> marshaling and reflection usage (WS, JMX, EJB ...).
>  MAJOR DISADVANTAGE : Semantic of static keyword on parameter might
> not be clear for beginers
>  ALTERNATIVES : Usage of existing bytecode handling lib can expose
> the parameter names already, but this leads to dependency [5][6] and
> potential security issues. Usage of APT[7] to store parameter names
> constraint to a prequirement : apply it to all the code you target.
> This is unlikely to happen for JARS you have not created, thus
> reducing the potential benefits.
>
> EXAMPLE
>
> SIMPLE EXAMPLE :
>
> (1a) :
>
> class OrderManager{
> public void order(String product, int amount){
>  // do the login
> }
> }
>
> (1b)
>
> class OrderManager{
> public void order(static String product, static int amount){
>  // do the login
> }
> }
>
> (2a)
> void displayOrderCriteria(){
> Method[] methods = OrderManager.class.getMedthods();
> for (Method m : methods){
>  System.out.println("To call :"+m);
>  for(String n : m.getParameterNames[]){
>   System.out.println("\tYou must provide :"+n);
>  }
> }
> }
>
> (2b)
> void displayOrderCriteria(){
> Method[] methods = OrderManager.class.getMedthods();
> for (Method m : methods){
>  System.out.println("To call :"+m);
>  for(String n : m.getStaticParameterNames[]){
>   System.out.println("\tYou must provide :"+n);
>  }
> }
> }
>
> ADVANCED EXAMPLE :
>
> (3.1)
> package java.lang.annotation
>
> @Documented
> @Retention(value = RetentionPolicy.SOURCE)
> @Target( { ElementType.METHOD, ElementType.ANNOTATION_TYPE })
> public @interface StaticParameterNames {
> };
>
> (3.2)
>
> @Retention(value = RetentionPolicy.RUNTIME)
> @Target( { ElementType.METHOD })
> @Inside(WebService.class)
> @ValidWebOperation
> @StaticParameterNames
> public @interface WebMethod {
> String operationName() default "";
> String action() default "";
> };
>
>
> (3.3)
>
> @WebService
> class LoginManager{
> @WebMethod public void doLogin(String user, char[] password){
>  // simply log the user
> }
> }
>
> DETAILS
>
> SPECIFICATION :
>
> Historicaly, method's parameter names can be stored in the Java
> bytecode using appropriate compiler switch [2]. Although, no standard
> API is available to benefit from them they aready. But when compiler
> optimisation is set or an obfuscater is enabled, then are no more
> available. This is not reliable.
>
> Such inconsistency, along with some other problems, have prevented the
> inclusion for JDK6 of previous proposition [3][4].
>
> This proposition of small language change, introduce named parameter
> on methods into the language thru the add of a new language paradigm :
> static named parameter. At source level, this new kind of parameter is
> simply a regular parameter with the modifier static set on it.
>
> As a summary, we will get two kind of parameters in the language :
> - regular named parameter (see method on (1a)) : the legacy, we "keep
> the good-old way", parameter might be stored in bytecode depending on
> compiler option, no change on language/semantic/compilation
> - static named parameter (see method on (1b)) : a regular named
> parameter with a static modifier added, whatever happens (compiler
> option, obfuscator, etc) parameter name will always be kept at
> bytecode level.
>
> At Java API level, on java.lang.reflec.Method, two new method will
> help API implementer to leverage both kind of parameters.
> - String[] getParameterNames()
> - String[] getParameterStaticNames()
>
> IDE would be most interrested into calling the first one. But API
> implementer (such as JAXWS for instance) requiring a consistent
> behavior could rely on the second. But they could downgrade on the
> first one for legacy JAR if they wish so.
>
> Introduction of an annotation StaticParameterNames could also be
> leverage by API implementer to include automatic parameter name
> storage. This one alone will ease lots of library code. For instance,
> in JAXWS (see example 3.3), WebParam are now optional to get a web
> service working : WebMethod would be enough as long as JAXWS
> implementer apply StaticParameterNames on the WebMethod annotation
> (see example 3.2).
>
> COMPILATION :
>
> Static named parameters are compiled the same way of regular named
> ones but with addition of the static modifier set on the reference at
> the bytecode level and the parameter name parameter kept in the table.
> No compiler/optimizer/obfuscator should remove/change the parameter
> names at bytecode level on a static named parameter.
>
> Thus, at a higher level, although not taking part of the method
> signature (and call resolution), the static named parameter could now
> be seen as part of the method contract: changing a static named
> parameter's name could have the same impact as renaming a method. This
> is the developper resposability to analyze impact of such a change.
>
> If a method is tagged with the annotation (or an inherited annotation)
> StaticParameterNames, all its method parameter should be compiled as
> if they were static named parameters.
>
> TESTING :
>
> Compile test classes (such as examples 1a & 1b) using compiler with
> the feature enable with and without optimization enable (the one that
> remove the parameter names on regular named parameters).
>
> For each scenario (with & without optimization) :
> Call the reflection API for listing regular named parameters, and
> check according to the names that should be returned as per the test
> class.
> Call the reflection API for listing static named parameters, and check
> according to the names that should be returned as per the test class.
>
> LIBRARY SUPPORT :
>
> Two methods must be added to java.lang.relfect.Method :
>
> String[] getParameterNames()
>
> List the parameter names as existing in the bytecode. No guaranty of
> reliability is made : can be renamed, removed, added, ...
> Array is of the same size of getParameterTypes(), for a given index,
> if the corresponding name is not found a null value is returned.
>
> String[] getParameterStaticNames()
>
> List the static parameter names as existing in the bytecode. Those
> named are reliable. Any change impact the contract.
> Array is of the same size of getParameterTypes(), for a given index,
> if the corresponding parameter is not tagged with static modifier, a
> null value is returned.
>
>
> StaticParameterNames (see example 3.1) annotation must be introduced
> to indicate to the compiler all parameters of a tagged method are
> meant to be static nammed parameters although not tagged with the
> static modifier. This anotation can tag other annotation.
>
>
> OTHER CHANGES:
>
> Any existing API willing to benefit from this feature, could inherit
> from StaticParameterNames but this is out of scope of this proposal.
>
> COMPATIBILITY
>
> MIGRATION :
> Manual migration is done adding static modifier on parameters.
> Automatic migration could be done by APIs leader using the
> StaticParameterNames annotation, thus all the existing code base would
> be migrated at the next build automatically.
>
>
> COMPATIBILITY :
>
> BREAKING CHANGES: no, this is the reason of using static modifier.
> EXISTING PROGRAMS: code using legacy class can benefit from the
> getParameterNames(). But getParameterStaticNames() will always return
> an array of null values.
>
>
> REFERENCES
>
> EXISTING BUGS
>
> http://bugs.sun.com/view_bug.do?bug_id=6444738
>
> URL FOR PROTOTYPE
>
> None at this time. Early feasibility check in the native VM coden plus
> pure Java code is feasible [5].
>
>
> [1] http://paulhammant.com/blog/parameter-names-for-java6- 
> question.html
> [2] http://java.sun.com/j2se/1.4.2/docs/tooldocs/windows/javac.html
> [3] http://weblogs.java.net/blog/mreinhold/archive/2005/12/mustang_release.html
> [4] http://blogs.sun.com/mr/entry/java_se_6_public_review
> [5] http://paranamer.codehaus.org/
> [6] http://www.jroller.com/eu/entry/using_asm_to_read_mathod
> [7] http://weblogs.java.net/blog/emcmanus/archive/2006/06/using_annotatio.html
>



From Joe.Darcy at Sun.COM  Sat Apr 18 17:20:41 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Sat, 18 Apr 2009 17:20:41 -0700
Subject: SUBMISSION : A second look on "named parameters"
In-Reply-To: <2dc3bd00904181515o2df0a1d3n3cf5ddd75d58d4ff@mail.gmail.com>
References: <2dc3bd00904181515o2df0a1d3n3cf5ddd75d58d4ff@mail.gmail.com>
Message-ID: <49EA6E59.3080700@sun.com>

Yes, we are well aware of the desire for named parameters from some 
quarters and the list received some related proposals.

This late submission will not be considered.

Regards,

-Joe

Jean-Baptiste Bugeaud wrote:
> Hi everybody,
>
> Here is an late submission, sorry I missed the initial deadline. If
> you think (as I do) that this is a key small change for lots of
> improvement, maybe there is still a very small gap to go for JDK7;-)
>
> A proposition including the same goal was introduced in JDK6 JSR but
> withdawn in final version. So legacy impact, issues ... should be
> already well known by the JDK core team. This second look has tried to
> solve all the problems.
>
> Let's go ....
>
> Author(s): Jean-Baptiste BUGEAUD, Paris, France
>
> OVERVIEW :
>   FEATURE SUMMARY : Introduce named parameter on methods into the language
>   MAJOR ADVANTAGE : Integration with the legacy, fully backward
> compatible. Clear paradigm separation.
>   MAJOR BENEFIT : Consistent way of naming the parameter help to unify
> existing APIs, remove boiler plate core thus simplify object
> marshaling and reflection usage (WS, JMX, EJB ...).
>   MAJOR DISADVANTAGE : Semantic of static keyword on parameter might
> not be clear for beginers
>   ALTERNATIVES : Usage of existing bytecode handling lib can expose
> the parameter names already, but this leads to dependency [5][6] and
> potential security issues. Usage of APT[7] to store parameter names
> constraint to a prequirement : apply it to all the code you target.
> This is unlikely to happen for JARS you have not created, thus
> reducing the potential benefits.
>
> EXAMPLE
>
> SIMPLE EXAMPLE :
>
> (1a) :
>
> class OrderManager{
>  public void order(String product, int amount){
>   // do the login
>  }
> }
>
> (1b)
>
> class OrderManager{
>  public void order(static String product, static int amount){
>   // do the login
>  }
> }
>
> (2a)
> void displayOrderCriteria(){
>  Method[] methods = OrderManager.class.getMedthods();
>  for (Method m : methods){
>   System.out.println("To call :"+m);
>   for(String n : m.getParameterNames[]){
>    System.out.println("\tYou must provide :"+n);
>   }
>  }
> }
>
> (2b)
> void displayOrderCriteria(){
>  Method[] methods = OrderManager.class.getMedthods();
>  for (Method m : methods){
>   System.out.println("To call :"+m);
>   for(String n : m.getStaticParameterNames[]){
>    System.out.println("\tYou must provide :"+n);
>   }
>  }
> }
>
> ADVANCED EXAMPLE :
>
> (3.1)
> package java.lang.annotation
>
> @Documented
> @Retention(value = RetentionPolicy.SOURCE)
> @Target( { ElementType.METHOD, ElementType.ANNOTATION_TYPE })
>  public @interface StaticParameterNames {
> };
>
> (3.2)
>
> @Retention(value = RetentionPolicy.RUNTIME)
> @Target( { ElementType.METHOD })
> @Inside(WebService.class)
> @ValidWebOperation
> @StaticParameterNames
> public @interface WebMethod {
>  String operationName() default "";
>  String action() default "";
> };
>
>
> (3.3)
>
> @WebService
> class LoginManager{
>  @WebMethod public void doLogin(String user, char[] password){
>   // simply log the user
>  }
> }
>
> DETAILS
>
> SPECIFICATION :
>
> Historicaly, method's parameter names can be stored in the Java
> bytecode using appropriate compiler switch [2]. Although, no standard
> API is available to benefit from them they aready. But when compiler
> optimisation is set or an obfuscater is enabled, then are no more
> available. This is not reliable.
>
> Such inconsistency, along with some other problems, have prevented the
> inclusion for JDK6 of previous proposition [3][4].
>
> This proposition of small language change, introduce named parameter
> on methods into the language thru the add of a new language paradigm :
> static named parameter. At source level, this new kind of parameter is
> simply a regular parameter with the modifier static set on it.
>
> As a summary, we will get two kind of parameters in the language :
>  - regular named parameter (see method on (1a)) : the legacy, we "keep
> the good-old way", parameter might be stored in bytecode depending on
> compiler option, no change on language/semantic/compilation
>  - static named parameter (see method on (1b)) : a regular named
> parameter with a static modifier added, whatever happens (compiler
> option, obfuscator, etc) parameter name will always be kept at
> bytecode level.
>
> At Java API level, on java.lang.reflec.Method, two new method will
> help API implementer to leverage both kind of parameters.
>  - String[] getParameterNames()
>  - String[] getParameterStaticNames()
>
> IDE would be most interrested into calling the first one. But API
> implementer (such as JAXWS for instance) requiring a consistent
> behavior could rely on the second. But they could downgrade on the
> first one for legacy JAR if they wish so.
>
> Introduction of an annotation StaticParameterNames could also be
> leverage by API implementer to include automatic parameter name
> storage. This one alone will ease lots of library code. For instance,
> in JAXWS (see example 3.3), WebParam are now optional to get a web
> service working : WebMethod would be enough as long as JAXWS
> implementer apply StaticParameterNames on the WebMethod annotation
> (see example 3.2).
>
> COMPILATION :
>
> Static named parameters are compiled the same way of regular named
> ones but with addition of the static modifier set on the reference at
> the bytecode level and the parameter name parameter kept in the table.
> No compiler/optimizer/obfuscator should remove/change the parameter
> names at bytecode level on a static named parameter.
>
> Thus, at a higher level, although not taking part of the method
> signature (and call resolution), the static named parameter could now
> be seen as part of the method contract: changing a static named
> parameter's name could have the same impact as renaming a method. This
> is the developper resposability to analyze impact of such a change.
>
> If a method is tagged with the annotation (or an inherited annotation)
> StaticParameterNames, all its method parameter should be compiled as
> if they were static named parameters.
>
> TESTING :
>
> Compile test classes (such as examples 1a & 1b) using compiler with
> the feature enable with and without optimization enable (the one that
> remove the parameter names on regular named parameters).
>
> For each scenario (with & without optimization) :
> Call the reflection API for listing regular named parameters, and
> check according to the names that should be returned as per the test
> class.
> Call the reflection API for listing static named parameters, and check
> according to the names that should be returned as per the test class.
>
> LIBRARY SUPPORT :
>
> Two methods must be added to java.lang.relfect.Method :
>
> String[] getParameterNames()
>
> List the parameter names as existing in the bytecode. No guaranty of
> reliability is made : can be renamed, removed, added, ...
> Array is of the same size of getParameterTypes(), for a given index,
> if the corresponding name is not found a null value is returned.
>
> String[] getParameterStaticNames()
>
> List the static parameter names as existing in the bytecode. Those
> named are reliable. Any change impact the contract.
> Array is of the same size of getParameterTypes(), for a given index,
> if the corresponding parameter is not tagged with static modifier, a
> null value is returned.
>
>
> StaticParameterNames (see example 3.1) annotation must be introduced
> to indicate to the compiler all parameters of a tagged method are
> meant to be static nammed parameters although not tagged with the
> static modifier. This anotation can tag other annotation.
>
>
> OTHER CHANGES:
>
>  Any existing API willing to benefit from this feature, could inherit
> from StaticParameterNames but this is out of scope of this proposal.
>
> COMPATIBILITY
>
> MIGRATION :
>  Manual migration is done adding static modifier on parameters.
>  Automatic migration could be done by APIs leader using the
> StaticParameterNames annotation, thus all the existing code base would
> be migrated at the next build automatically.
>
>
> COMPATIBILITY :
>
>  BREAKING CHANGES: no, this is the reason of using static modifier.
>  EXISTING PROGRAMS: code using legacy class can benefit from the
> getParameterNames(). But getParameterStaticNames() will always return
> an array of null values.
>
>
> REFERENCES
>
> EXISTING BUGS
>
> http://bugs.sun.com/view_bug.do?bug_id=6444738
>
> URL FOR PROTOTYPE
>
> None at this time. Early feasibility check in the native VM coden plus
> pure Java code is feasible [5].
>
>
> [1] http://paulhammant.com/blog/parameter-names-for-java6-question.html
> [2] http://java.sun.com/j2se/1.4.2/docs/tooldocs/windows/javac.html
> [3] http://weblogs.java.net/blog/mreinhold/archive/2005/12/mustang_release.html
> [4] http://blogs.sun.com/mr/entry/java_se_6_public_review
> [5] http://paranamer.codehaus.org/
> [6] http://www.jroller.com/eu/entry/using_asm_to_read_mathod
> [7] http://weblogs.java.net/blog/emcmanus/archive/2006/06/using_annotatio.html
>
>   



From jjb at google.com  Sun Apr 19 23:45:15 2009
From: jjb at google.com (Joshua Bloch)
Date: Sun, 19 Apr 2009 23:45:15 -0700
Subject: Automatic Resource Management, V.2
Message-ID: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>

Fellow Coiners,

Thanks for all your feedback on the Automatic Resource Management proposal.
 I have revised the proposal in light of these comments.  The new version
(V.2) can be seen at this URL:
http://docs.google.com/Doc?id=ddv8ts74_3fs7483dp . It is included below for
archival purposes.

   Josh

Automatic Resource Management (V.2)

*AUTHOR: *Joshua Bloch


*OVERVIEW*


FEATURE SUMMARY: A *resource* is as an object that must be closed manually,
such as a java.io.InputStream, OutputStream, Reader, Writer, Formatter;
java.nio.Channel; java.net.socket; java.sql.Connection, Statement, ResultSet,
or java.awt.Graphics. The *automatic resource management statement* is a
form of the try statement that declares one or more resources. The scope of
these resource declarations is limited to the statement. When the statement
completes, whether normally or abruptly, all of its resources are closed
automatically.


MAJOR ADVANTAGE: The automatic resource management statement obviates the
need for manual resource termination, which has proven ugly and error prone.
Even good programmers get it wrong most of the time. For example, Sun?s
guide to Persistent Connections (http://tinyurl.com/6b5jc7) gets it wrong in
code that claims to be exemplary. Likewise, the solution on page 88 of Bloch
and Gafter?s *Java Puzzlers* (Addison-Wesley, 2006) is badly broken, and no
one ever noticed. In fact, 2/3 of the uses of the close method in the JDK
itself are wrong! The price for failing to terminate resources properly is
resource leaks or even outright failures, which may be silent (as in *Java
Puzzlers*).


Even the ?correct? idioms for manual resource management are deficient: if
an exception is thrown in the try block, and another when closing the
resource in the finally block, the second exception supplants the first,
making it difficult to determine the real cause of the trouble.  In other
words, by responsibly closing your resource even during some catastrophic
event, you can actually erase all record of the event, resulting in many
wasted hours of debugging. While it is possible to write code to suppress
the second exception in favor of the first, virtually no one does, as it is
just too verbose. This is not a theoretical problem; it has greatly
complicated the debugging of large systems.  A secondary advantage of the
automatic resource management construct is that it can suppress the
uninteresting (second) exception in favor of the interesting (first) one
with no effort on the part of the programmer, and no loss in the clarity of
the program.


Like the for-each statement (introduced in Java 1.5), the automatic resource
management statement is a small piece of syntactic sugar with a very high
power-to-weight ratio.


MAJOR DISADVANTAGE: Like all syntactic sugar, this construct removes a bit
of Java?s ?what you see is what you get? character (?transparency?). Another
disadvantage is increased coupling between the language specification and
libraries.


ALTERNATIVES: The benefits of this proposal cannot be had without a language
change. Absent a language change, you must close resources manually. That is
why Java?s competitors have automatic resource management constructs (C#
has using blocks and C++ has destructors).


*NONTRIVIAL CHANGES IN THIS VERSION*



   1. Renamed interface Disposable to AutoCloseable and moved it from
   package java.lang to java.lang.auto.
   2. Enhanced statement to allow expressions in place of declarations to
   designate resources.
   3. Added support for retention of suppressed exceptions.
   4. Added list of types to be retrofitted.
   5. Added design FAQ with additional examples.



*EXAMPLES*


SIMPLE EXAMPLE: Here is a static method to read the first line of a file,
demonstrating the minimal (nearly) correct code to release a single resource
today.


    static String readFirstLineFromFile(String path) throws IOException {

        BufferedReader br = new BufferedReader(new FileReader(path));

        try {

            return br.readLine();

        } finally {

            br.close();

        }

    }


Unfortunately, if the readLine and close invocations both throw exceptions,
the latter exception supplants the former. The only practical way around
this today would to be to ignore any exception thrown by the close invocation.
While this might be reasonable in the case of a Reader or InputStream, it
would be disastrous for a Writer or OutputStream.


Here?s how it would look with an automatic resource management statement:



    static String readFirstLineFromFile2(String path) throws IOException {

        try (BufferedReader br = new BufferedReader(new FileReader(path)) {

           return br.readLine();

        }

    }


ADVANCED EXAMPLES*:* Here is a static method to make a copy of a file,
demonstrating the minimal correct code to release two resources today:


    static void copy(String src, String dest) throws IOException {

        InputStream in = new FileInputStream(src);

        try {

            OutputStream out = new FileOutputStream(dest);

            try {

                byte[] buf = new byte[8 * 1024];

                int n;

                while ((n = in.read(buf)) >= 0)

                    out.write(buf, 0, n);

            } finally {

                out.close();

            }

        } finally {

            in.close();

        }

    }


Here?s how it would look with an automatic resource management statement:


    static void copy(String src, String dest) throws IOException {

        try (InputStream in = new FileInputStream(src);

             OutputStream out = new FileOutputStream(dest)) {

            byte[] buf = new byte[8192];

            int n;

            while ((n = in.read(buf)) >= 0)

                out.write(buf, 0, n);

        }

    }



*DETAILS*

* *

SPECIFICATION: What follows is not intended to be a formal JLS-quality
specification. It emphasizes brevity and clarity over thoroughness.



SYNTAX: The production for *TryStatement* in JLS ?14.20 would be extended
with this alternative:



*TryStatement*:

    try ( *ResourceSpecifications* ) *Block Catchesopt Finallyopt*

*Resource**Specifications*:

    *Resource**Specification*

    *Resource**Specification *; *Resource**Specifications*

*Resource**Specification**:*

*    **LocalVariableDeclaration*

*    Expression*

* *

The type of each *LocalVariableDeclaration* or *Expression *in a *
ResourceDeclarations *must be a subtype of AutoCloseable. Such types are
known as *resource types*.



SEMANTICS and COMPILATION: An automatic resource management statement with a
single local variable declaration and no *Finally* or *Catches* would behave
as if replaced by the following source code:



{

    final *LocalVariableDeclaration* ;

    try *Block* finally {

        *localVar*.close();  // *localVar* is the variable declared in *
LocalVariableDeclaration*

    }

}


An automatic resource management statement with a single resource expression
and no *Finally* or *Catches* would behave as if replaced by the following
source code:



{

    final *T**ype* #localVar = *Expression*;

    try *Block* finally {

        #*localVar*.close();

    }

}



The variable #localVar is a compiler-generated identifier distinct from any
other identifiers (compiler-generated or otherwise) that are in scope (JLS
?6.3) at the point where the automatic resource management statement occurs.
The *Type *in the above desugaring is replaced by the static type of *
Expression*.


An automatic resource management statement with multiple resource
specifications (declarations or expressions) and no *Finally* or
*Catches* would
behave as if (recursively) replaced by the following source code:



{

    final *LocalVariableDeclaration* ;              // First variable
declaration

    try( *ResourceDeclarations* ) *Block* finally {  // Remaining resource
declarations

        *localVar*.close();  // *localVar* is the variable declared in *
LocalVariableDeclaration*

    }

}



When you initially desugar an automatic resource management statement with n
resource specifications for n > 1, you get an automatic resource management
statement with n-1 resource declarations. After n such replacements, you
have n nested try-finally statements, and the desugaring is complete. A
single declaration that declares multiple resources is treated as if it were
multiple declarations, each declaring a single resource. Note that resource
declarations are implicitly final. For consistency with existing constructs
with implicit modifiers, it is legal (though discouraged) for the programmer
to provide an explicit final modifier.



Note that the close method is only called on resources whose declarations
(or expressions) execute without throwing an exception, and that the first
such exception causes the statement to complete abruptly.



An automatic resource management statement with a *Finally* or *Catches* would
behave as if replaced by the following code (which contains an automatic
resource management statement with no *Finally* or *Catches that must be
expanded as per the desugaring above*). Note that resources are closed
before any explicit finally or catch clauses have executed, and that
resource variable declarations are not in scope in explicit finally and
catch clauses:



try {

    try ( *ResourceDeclarations* ) *Block*

}* Catchesopt Finallyopt*


The above desugarings are simplified for pedagogical purposes. They solve
most of the problems described above but one problem remains: if the
*Block* throws
one exception, and the automatically generated close invocation throws
another, the latter exception supplants the former. This shortcoming is
corrected by using a slightly more complex desugaring for the
single-local-variable-declaration forms of the construct.  In this
desugaring, an exception thrown during the lifetime of a resource (the *
Block*) receives priority over an exception thrown by an automatically
generated close invocation.  Such a *suppressed exception* is not discarded,
but is associated with the *primary exception *(the one thrown from the *
Block*), and can be extracted using Throwable's getSuppressedExceptions
 method.


The following desugaring should be regarded as definitive (though the
compiler is free to emit any object code that obeys its semantics):



{

    final *LocalVariableDeclaration* ;  // Or final *T**ype* #localVar = *
Expression *;

    Throwable #primaryException = null;

    try *Block* catch (final Throwable #t) {

        #primaryException = t;

        throw #t;

    } finally {

        if (#primaryException != null) {

            try {

                localVar.close();

            } catch(Exception #suppressedException) {


 #primaryException.addSuppressedException(#suppressedException);

            }

        } else {

            localVar.close();

        }

    }

}



The variables #primaryException,  #t, and  #suppressedException are
compiler-generated identifiers that are distinct from one and other, and
from any other identifiers (compiler-generated or otherwise) that are in
scope (JLS ?6.3) at the point where the automatic resource management
statement occurs.


This de-sugaring takes advantage of the ability to rethrow a final caught
exception, which has been proposed for Java 7. The present proposal does *
not* depend on this ability. In its absence, one could use a method such as
sneakyThrow (*Java Puzzlers*, Puzzle 43).


It is suggested that the line number table emitted by the compiler make the
automatically generated resource-closing code appear to come from the last
line of the *Block* (which will contain a close bracket), immediately prior
to any *Catches**opt* or *Finally**opt*.


TYPE SYSTEM: The proposal has no effect on the type system (other than
classifying certain types as resources).


REACHABILITY AND DEFINITE ASSIGNMENT: The reachability and definite
assignment rules for this construct are specified by the desugaring above.
It has been noted that under certain pathological conditions, the compiler
must generate an error message indicating that the construct can throw an
exception that cannot occur. These pathological conditions are unlikely to
occur in any real code. If we ever wish to address this issue, we could do
so by modifying the DA/DU rules for the language so that the following
program becomes legal:


public static void main(String[] args) {
    if (false)
        throw new Exception();  // Compiler error!
}



TESTING: The proposed construct can be tested by writing automatic resource
management statements with a number of resources varying from 1 to some
upper limit (say 10). Each resource can throw an exception (or not) during
initialization, use, or termination. JUnit assertions are added to check
that all resources opened are automatically closed, and that the correct
exception (if any) is thrown.



LIBRARY SUPPORT: A class must implement a designated interface to make it
eligible for automatic resource management. An obvious choice would be
Closeable, but unfortunately its close method is specified to throw
IOException, which precludes its use in a general purpose resource
management facility. It is, however, possible to retrofit Closeable with a
superinterface:



*package** java.lang.auto;*

*/***

* * A resource that must be closed when it is no longer needed.*

* */*

*public interface AutoCloseable {*

*    void close() throws Exception;*

*}*



package java.io;

public interface Closeable *extends AutoCloseable* {

    void close() throws IOException;

}


Retrofitting java.io.Closeable to implement AutoCloseable will also provide
automatic resource management for its 11 subinterfacs and 81 implementing
classes in the JDK. Other existing classes and interfaces can be similarly
retrofitted, for example:



package java.sql;

interface Connection *extends AutoCloseable* {

    void close() throws SQLException;

    ...    // (and all the other members of the Connection interface)

}


Other types that should be retrofitted include java.sql.Statement,
PreparedStatement, ResultSet; and java.awt.Graphics. Other possibilities
include java.nio.channels.FileLock; javax.imageio.ImageReader, ImageWriter;
javax.naming.Context; javax.xml.stream.XMLEventReader, XMLEventWriter,
XMLStreamReader, XMLStreamWriter; java.beans.XMLEncoder, and XMLDecoder. It
is best to err on the side of caution, and to only retrofit classes that we
know are appropriate for automatic resource management. More classes can be
retrofitted over time, and new types can be designed with automatic resource
management in mind.  See this document for additional
information<http://docs.google.com/Doc?id=ddv8ts74_1d7tz65fd>
.


To support automatic retention of suppressed exceptions (for high-quality
diagnostics), we add these methods to java.lang.Throwable:


/**

 * Adds the specified exception to the list of exceptions that were
suppressed,

 * typically by the automatic resource management statement, in order to

 * deliver this exception.

 */

public void addSuppressedException(Throwable suppressedException);


/**

 * Returns an array containing all of the exceptions that were suppressed,

 * typically by the automatic resource management statement, in order to

 * deliver this exception.

 */

public Throwable[] getSuppressedExceptions().


The printStackTrace method should be modified to append the stack traces for
any suppressed exceptions.


REFLECTIVE APIS: This proposal has no effect on core reflective APIs. The
tree API inside javac (
http://java.sun.com/javase/6/docs/jdk/api/javac/tree/index.html) would
require a minor extension.



OTHER CHANGES: No other parts of the platform need be to be updated.



MIGRATION: As discussed above in *Library Support*, any lexically scoped
resource type that must be closed manually should be retrofitted to
implement the AutoCloseable interface. New code using classes that
implement AutoCloseable should use automatic resource management statements
(for clarity and correctness). Manual resource management in existing code
can be replaced by automatic resource management for increased clarity and
improved behavior. Given the number of resource management errors observed
in existing code, it may be worth the time to do this systematically. It is
very easy to do this with any modern IDE, which can search for all uses of a
method (such as java.io.Closeable.close()).



*COMPATIBILITY*

* *

BREAKING CHANGES: All previously valid programs remain valid, and their
semantics is unaffected.

* *

EXISTING PROGRAMS: Source and class files of earlier versions are unaffected
by this feature. No new overloadings or overridings can occur.


*REFERENCES*

* *

EXISTING BUGS: 4888664, 4364906, 4331290, 4215007, 4120342.


*DESIGN FAQ*


*1. Does the construct support locks?*

The automatic resource management statement was not designed for use with
locks. The synchronized block already handles Java's built-in monitor locks.
The java.util.concurrent.locks.Lock interface and its implementations were
added to handle some special cases that built-in synchronization doesn't
support, such as non-block-structured locking, and most programmers have no
need for them. (Many uses of Lock would be better replaced by a
higher-level java.util.concurrent abstraction such as Semaphore,
CountDownLatch, or CyclicBarrier.)

Also, it is quite straightforward to acquire and release these locks
manually, so even legitimate users of the Lock interface have little
incentive to use a more automated solution:

     myLock.lock();
     try {
         // Access the resource protected by myLock
     } finally {
         myLock.unlock();
     }

That said, it *is* possible to use the proposed automatic resource
management statement for lock management with the aid of an adapter like
this one:

  interface AutoLock extends AutoCloseable {
      AutoLock lock();  // Locks lock and returns this
      void close();     // Unlocks lock
  }

  static AutoLock autoLock(final Lock lock) {
      return new AutoLock() {
          public AutoLock lock() { lock.lock(); return this; }
          public void close()    { lock.unlock(); }
      };
  }

With this adapter, you can use the following code to perform locked access
with automatic unlocking:

    AutoLock al = autoLock(myLock);
    ...
    try(al.lock()) {
        // Access the resource protected by lck
    }

*2. Does the construct allow access to resources after an exception is
thrown from within the block, but before the resource is closed?*

Not directly. The need for this functionality is rare. The workaround is to
nest a try-catch block inside the automatic resource management statement:

    try (LineNumberReader reader = getInput()) {
        try {
            parseInput(reader);
        } catch (CharacterCodingException ex) {
            report("Char encoding error at line " + reader.getLineNumber());
            throw ex;  // Rethrow the exception
        }
    }



* 3. Does the construct work properly with ?decorated? resources?*


There is a low probability of a resource leak when the construct is used in
this fashion:


    try (BufferedReader br = new BufferedReader(new FileReader(path)) {
       ... // Use buffered reader
    }




The problem is that there is a ?window of vulnerability? in between the time
the FileReader is constructed and the time the BufferedReader is
constructed. If the BufferedReader construction fails, say, because there is
insufficient memory for the buffer, the construct will *not *close the
FileReader. This is unfortunate but generally acceptable. The window of
vulnerability is small, and it seems likely that the application is moribund
if decorator construction fails.


In the unlikely event that this level of risk is unacceptable for your
application, you can eliminate the window of vulnerability by treating the
object and its decorator as separate resources:


    try (FileReader fr = new FileReader(path) {
        try (BufferedReader br = new BufferedReader(fr) {
            ... // Use buffered reader
        }
    }

* 4. Does the construct support resource types whose termination method has
a name other than **close**?*

Not directly. There are two obvious ways in which the construct could have
supported this functionality. One is to designate the termination method
with an annotation. But this violates the rule that annotations cannot
change the semantics of a program (JLS ?9.7). The other is to use an actual
modifier to denote the termination method (the finally keyword has been
proposed for this purpose). This would, however, require a class file format
change, and a mandate changes to tools such as JavaDoc. The resulting
construct would be more ?magical,? and wouldn't mesh as well with Java?s
type system.

The proposed construct is an ?80-20? solution. It is aimed squarely at
solving the serious problem of Closeables. Most resources can be retrofitted
to implement AutoCloseable, but a few can't (e.g., interface types that do
not already contain a parameterless close method and class types that
contain a parameterless close method with the wrong return type or
semantics). For such resources, we recommend the use of an adapter, such as
AutoLock above. The exact form of the adapter will differ depending on the
details of the resource.

*5. Some failures of the **close** method can be safely ignored (e.g.,
closing a file that was open for read). Does the construct provide for this?
*

No. While this functionality seems attractive, it is not clear that it's
worth the added complexity. As a practical matter these ?harmless
exceptions? rarely if ever occur, so a program will be no more robust if
these exceptions are ignored. If you feel you must ignore them, there is a
workaround, but it isn't pretty:

    static void copy(String src, String dest) throws IOException {
        boolean done = false;
        try (InputStream in = new FileInputStream(src)) {
            try(OutputStream out = new FileOutputStream(dest)) {
                byte[] buf = new byte[8192];
                int n;
                while ((n = in.read(buf)) >= 0)
                    out.write(buf, 0, n);
            }
            done = true;
        } catch(IOException e) {
            if (!done)
                throw e;
        }
    }


*ACKNOWLEDGMENTS*


I thank the members of the coin-dev list and my colleagues at Google for all
of the useful input on earlier versions of this proposal.


From forax at univ-mlv.fr  Mon Apr 20 00:11:04 2009
From: forax at univ-mlv.fr (=?windows-1252?Q?R=E9mi_Forax?=)
Date: Mon, 20 Apr 2009 09:11:04 +0200
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
Message-ID: <49EC2008.5040308@univ-mlv.fr>

Joshua Bloch a ?crit :
> Fellow Coiners,
>
> Thanks for all your feedback on the Automatic Resource Management proposal.
>  I have revised the proposal in light of these comments.  The new version
> (V.2) can be seen at this URL:
> http://docs.google.com/Doc?id=ddv8ts74_3fs7483dp . It is included below for
> archival purposes.
>
>    Josh
>   
Hi josh,
just a small question why AutoClosable is specified to be in java.lang.auto
and not java.lang.

regards,
R?mi


From jjb at google.com  Mon Apr 20 00:30:36 2009
From: jjb at google.com (Joshua Bloch)
Date: Mon, 20 Apr 2009 00:30:36 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <49EC2008.5040308@univ-mlv.fr>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<49EC2008.5040308@univ-mlv.fr>
Message-ID: <17b2302a0904200030j47c348f5ha40c744d8e9ff246@mail.gmail.com>

R?mi,
Good question. We did it to eliminate the possibility of name clashes in
existing programs. JBoss actually uses the name AutoCloseable. Types in
java.lang are automatically imported, and putting AutoCloseable in
java.lang.auto avoids this issue. It doesn't make the construct any less
usable, as you don't have to mention AutoCloseable explicitly to use the
construct.

Josh

On Mon, Apr 20, 2009 at 12:11 AM, R?mi Forax <forax at univ-mlv.fr> wrote:

> Joshua Bloch a ?crit :
>
>> Fellow Coiners,
>>
>> Thanks for all your feedback on the Automatic Resource Management
>> proposal.
>>  I have revised the proposal in light of these comments.  The new version
>> (V.2) can be seen at this URL:
>> http://docs.google.com/Doc?id=ddv8ts74_3fs7483dp . It is included below
>> for
>> archival purposes.
>>
>>   Josh
>>
>>
> Hi josh,
> just a small question why AutoClosable is specified to be in java.lang.auto
> and not java.lang.
>
> regards,
> R?mi
>


From bugeaud at gmail.com  Mon Apr 20 01:18:30 2009
From: bugeaud at gmail.com (Jean-Baptiste Bugeaud)
Date: Mon, 20 Apr 2009 10:18:30 +0200
Subject: SUBMISSION : A second look on "named parameters" / Clarification 
	on the scope
Message-ID: <2dc3bd00904200118s35e085fdk6f4ef3cac83cd6e9@mail.gmail.com>

Hello Reinier, Hello Joe,

Thanks for your feedback.

2009/4/19 Reinier Zwitserloot <reinier at zwitserloot.com>:
> Your proposal is very incomplete. Three major nits:
>
> A. Did I miss something, or did you totally forget to include an example of
> calling a method with named parameters? Something like:
>
> doLogin(user: "foobar", password: new char[] { 'a', 'b', 'c' })

Reiner, I think my submission name is misleading everybody. This is
not the same thing you debate some times back. My mistake ... I should
have clarified from the start : I do not look at adding direct call by
parameter name into the language (say "? la" ObjectiveC). But simply a
reliable way access to parameter name and name a parameter's name in
static way thru time. See bug 6444738 for differences.

Parameter names are very usefull information in most cases, and at
this time, either implementers use duplicate annotation (dummy
annotations storing again the same name) or they use tools such as ASM
to workaround the lack of API in the JDK.

At the begining, I thought this requirement did not required a small
synthax language change : a new API would be enough. But soon I
realized that introducing name parameter that are static thru time,
introduce anyway a new paradigm in the language that developer should
be able to control directly : do I want this parameter name to be
static thu time ? or do I want to let the compiler decide as usual ?

A compiler option is not the suitable tool for this.
If this is a global switch, it will not offer the fine grain required.
If this is a per class/per package option, it will clutter the command line.
And in both cases, it will not offer paradigm separation with the
legacy. Thus you can not rely on the parameter name because you never
know if developper has stored the name accidentaly or for purpose.

> B. Why static? You might as well have picked 'strictfp' - it's a total
> non-sequitur choice. Re-use of existing keywords is not really a panacea; it
> waters down the anchoring ability of a keyword to virtually nothing. I'm not
> sure if context-sensitive keywords are any better, but java7 is already
> going to have at least one ('module'), so don't beat around the bush and
> just call it 'named'). Could be just me, but introducing a change which is
> not backwards compatible IF you have a type that's called 'named' (written
> just like that, all-lower case), is not something I find troublesome in the
> least. That's very ugly code, and a migration tool can fix this easily.

Because of the definition a dictionary gives of it : something like
"showing little change" is exactly what I meant for this paradigm. And
no "strictfp", as well as "const" and "goto" are not matching, you see
;-)

If you think that this worth integrating a new keywork, then there is
room for debate. I think static fits perfectly and is clear enough.
AFAIK, we already have final that is contextual? why not static too ?
final is already stretched between two things : do not overload member
and do not reasign variable.

With the proposed language changed static modifier will be stretched
between static thru instances for members and static thru time for
variables.

> C. You don't mention having default values for parameters, which is sort of
> the point of this exercise (otherwise you really still need builders  ; any
> method that has so many parameters that they need names probably needs a
> builder, and without defaults, not providing one and instead relying on
> named params is just an inferior bandaid to your ugly API; to get it right
> you STILL need to provide a builder. If, however, parameters can have
> defaults, then you no longer need to make builders at all).

This is because I am not asking for named call of method ... simply
for a way to access name of parameter. Just a completely different
topic.
I don't see why a parameter on an EJB is not meanfull for the external
? same for an webservice ? why a parameter name could not be meanfull
? I don't get your point.

My design decision is the kind of decision that led to erasure based
genericity : it has some drawback, loss of real parametrics instances
that could be usefull while reflection. But was the right decision at
the right time or either we would have lots binary compatibility or we
would still be debating wether or not implementing generics.
	
My proposition on parameter name is analog, it is just meant to be
used ASAP but does it does not fully solve all the possible
expectations from this topic scope. Namely, should we call "by
parameter name" in the language ? and how ?

Room is let for the coming decade ;-) But the propopsition does not
close doors to anything.

> I suggest you look over the coin-dev mailing list; I entered a rough sketch
> of a named parameters proposal near the end of coin. I never wrote it up
> because I thought of it far too close to the deadline, and it's still of
> such high impact that I doubt it would pass muster for coin.

Yes I've followed the debate :) But, again its my mistake "call by
parameter names" is a much more complex topic with lots of
performance/plaform impact. This is not a small language change IMHO.
Again, I do not look for calling a direct method call using named
parameters .... just a way to retreive them.

-- --

Joe, yes "late I am" ;-)

FYI, I got this proposition cooking for several months I was not able
to find time to write & post it to you (pittyfull isn't it).

If we remove the "language change" part (static named parameter) and
only keep the getParameterNames() API part (keep the regular parameter
name), do you think this can be pushed to JDK7 even if out of scope of
coin ? This is a very small change to the API and would solve lot of
time from lot of people.

I mean, this API (along with the rest of the named parameter spec) was
removed from JDK6, skiping this in JDK7 means years again to wait for
it ? I think we are too much getting dependent on tools such as ASM in
lots of places (JavaEE implementation stacks for instance). And we
have a good opportunity to remove the dependency for a clean/simple
solution IMHO.

Best Regards,
JB


From scolebourne at joda.org  Mon Apr 20 02:31:11 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Mon, 20 Apr 2009 10:31:11 +0100
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
Message-ID: <4b4f45e00904200231p9ce1625o84f7281ccc514b78@mail.gmail.com>

2009/4/20 Joshua Bloch <jjb at google.com>:
> * 3. Does the construct work properly with ?decorated? resources?*
> ? ?try (FileReader fr = new FileReader(path) {
> ? ? ? ?try (BufferedReader br = new BufferedReader(fr) {
> ? ? ? ? ? ?... // Use buffered reader
> ? ? ? ?}
> ? ?}

Would this section be better written:

    try (FileReader fr = new FileReader(path); BufferedReader br = new
BufferedReader(fr) {
          ... // Use buffered reader
    }

ie. the second resource is derived from the first within one ARM block.

(More generally, I think I'd prefer a single resource per ARM, as I
think its a lot clearer overall and more consistent, but since you've
allowed it in the proposal, I assume you'd want to keep to that
style.)

Stephen


From reinier at zwitserloot.com  Mon Apr 20 03:16:05 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Mon, 20 Apr 2009 12:16:05 +0200
Subject: SUBMISSION : A second look on "named parameters" / Clarification
	on the scope
In-Reply-To: <2dc3bd00904200118s35e085fdk6f4ef3cac83cd6e9@mail.gmail.com>
References: <2dc3bd00904200118s35e085fdk6f4ef3cac83cd6e9@mail.gmail.com>
Message-ID: <E807B68F-1621-4AD7-8052-146B0C45FB89@zwitserloot.com>

Ah, now I understand.

I've got a much simpler proposal to address this issue.

NB: Joe, I know coin's long gone, but perhaps consider this one anyway  
- it seems to me that some sort of named parameters proposal is likely  
to be accepted in the future, and adding names now should ease  
transition. As part of the effort I've listed all possibly  
complication I can come up with, at the end.

Proposal:


Starting from the new class file format introduced in java7 (due to  
module support, the class format is definitely getting a version  
bump), all compilers MUST put the names of the parameters in the class  
file (javac -g style), and obfuscators/compressors/whatever MUST NOT  
remove this; a class file with version v50 (or whatever number its  
going to end up being) won't even pass the verifier without the names  
in place.

Add an API call on the java.lang.reflect.Method object to obtain the  
names of the parameters (returns a String[], or 'null' if they aren't  
there. Calling this on a param-less method returns an empty array, not  
null). Having the names is an all-or-nothing situation: Either the  
names are all there and this call works, or some/all are missing, and  
then this call does not work. I'm not sure if you can even have just a  
few names defined in the .class file format, but even if you can, that  
situation should be so extremely rare, its not worth writing up a  
complicated rule for). It is guaranteed that if the array exists (is  
not null), then each array element is not null.

Voila. No need to turn in a proposal that's more complicated than most  
just to solve this simple problem.

Complications:

A) It would no longer be possible to rewrite a v49 and below class  
without debug info into a v50 and up class file without having the  
source file, but I don't actually know of any tools that attempt to do  
this.

B) Code that generates class files on the fly (like proxy generators  
and the like) will need to consider the names of method parameters if/ 
when they update the class file format they generate to v50+. A proxy  
generator has issues when it is trying to generate a v50+ proxy where  
its input object's class spec AND the input interface to proxy on are  
both v49- without debug info, for example.

C) A (bad) quick-fix for either of the above issues is to just use  
'arg0', 'arg1', 'arg2', analogous to what e.g. eclipse does when  
showing method signatures for methods in classes where there is no  
source, no debug info and no javadoc. This is not at all the right  
idea. A small risk that the class file format documentation should  
mention as not being appropriate unless there is absolutely no other  
option.

D) Most code these days ships with source, or javadoc, or debug info,  
so that auto-complete shows the proper names for each parameter, but  
this certainly isn't true for /all/ java code out there. After this  
change, method param names become visible to all. This may not be a  
desired side-effect for programming shops that export libraries to  
clients where their method parameter names are inappropriate (swear  
words, or 'x', 'y', and 'z' and this creates deserved but nevertheless  
unexpected ridicule for sucking at programming style). I think this is  
an acceptable price to pay. Parameters are method-local which are  
extremely easy to rename with your friendly neighbourhood IDE's  
refactor tool.

E) While technically the names are NOT part of API, and you CAN freely  
change names around without breaking any code, old or new, the names  
still do become a little more enshrined as at least almost part of the  
public API. This is already the case to some extent (param names show  
up in various tooling support such as javadoc and auto-completing  
IDEs) but this change would move parameter names a little more towards  
a complete member of public API. This is an issue, but its also the  
point of this proposal: Move towards a java world where parameter  
names are universally available and are meaningful. I don't think this  
is a serious problem, because A) names already have a flavour of  
importance right now, and B) While they become more important with  
this proposal, they still aren't true public API, and changing names  
even after this proposal is accepted is not backwards incompatible.

F) Confusion may arise when these names are unintentionally taken as  
being either part of public API, or being hierarchical; they are in  
fact neither. For example, this proposal makes no attempt to harmonize  
name conflicts; if interface A has void foo(int bar), and interface B  
has void foo(int baz), you can still of course write a class that  
implements both of these. You can even name your foo's parameter  
'floobargle', of course. The aim of this proposal does not involve  
making parameter names inherit sensibly.


  --Reinier Zwitserloot



On Apr 20, 2009, at 10:18, Jean-Baptiste Bugeaud wrote:

> Hello Reinier, Hello Joe,
>
> Thanks for your feedback.
>
> 2009/4/19 Reinier Zwitserloot <reinier at zwitserloot.com>:
>> Your proposal is very incomplete. Three major nits:
>>
>> A. Did I miss something, or did you totally forget to include an  
>> example of
>> calling a method with named parameters? Something like:
>>
>> doLogin(user: "foobar", password: new char[] { 'a', 'b', 'c' })
>
> Reiner, I think my submission name is misleading everybody. This is
> not the same thing you debate some times back. My mistake ... I should
> have clarified from the start : I do not look at adding direct call by
> parameter name into the language (say "? la" ObjectiveC). But simply a
> reliable way access to parameter name and name a parameter's name in
> static way thru time. See bug 6444738 for differences.
>
> Parameter names are very usefull information in most cases, and at
> this time, either implementers use duplicate annotation (dummy
> annotations storing again the same name) or they use tools such as ASM
> to workaround the lack of API in the JDK.
>
> At the begining, I thought this requirement did not required a small
> synthax language change : a new API would be enough. But soon I
> realized that introducing name parameter that are static thru time,
> introduce anyway a new paradigm in the language that developer should
> be able to control directly : do I want this parameter name to be
> static thu time ? or do I want to let the compiler decide as usual ?
>
> A compiler option is not the suitable tool for this.
> If this is a global switch, it will not offer the fine grain required.
> If this is a per class/per package option, it will clutter the  
> command line.
> And in both cases, it will not offer paradigm separation with the
> legacy. Thus you can not rely on the parameter name because you never
> know if developper has stored the name accidentaly or for purpose.
>
>> B. Why static? You might as well have picked 'strictfp' - it's a  
>> total
>> non-sequitur choice. Re-use of existing keywords is not really a  
>> panacea; it
>> waters down the anchoring ability of a keyword to virtually  
>> nothing. I'm not
>> sure if context-sensitive keywords are any better, but java7 is  
>> already
>> going to have at least one ('module'), so don't beat around the  
>> bush and
>> just call it 'named'). Could be just me, but introducing a change  
>> which is
>> not backwards compatible IF you have a type that's called  
>> 'named' (written
>> just like that, all-lower case), is not something I find  
>> troublesome in the
>> least. That's very ugly code, and a migration tool can fix this  
>> easily.
>
> Because of the definition a dictionary gives of it : something like
> "showing little change" is exactly what I meant for this paradigm. And
> no "strictfp", as well as "const" and "goto" are not matching, you see
> ;-)
>
> If you think that this worth integrating a new keywork, then there is
> room for debate. I think static fits perfectly and is clear enough.
> AFAIK, we already have final that is contextual? why not static too ?
> final is already stretched between two things : do not overload member
> and do not reasign variable.
>
> With the proposed language changed static modifier will be stretched
> between static thru instances for members and static thru time for
> variables.
>
>> C. You don't mention having default values for parameters, which is  
>> sort of
>> the point of this exercise (otherwise you really still need  
>> builders  ; any
>> method that has so many parameters that they need names probably  
>> needs a
>> builder, and without defaults, not providing one and instead  
>> relying on
>> named params is just an inferior bandaid to your ugly API; to get  
>> it right
>> you STILL need to provide a builder. If, however, parameters can have
>> defaults, then you no longer need to make builders at all).
>
> This is because I am not asking for named call of method ... simply
> for a way to access name of parameter. Just a completely different
> topic.
> I don't see why a parameter on an EJB is not meanfull for the external
> ? same for an webservice ? why a parameter name could not be meanfull
> ? I don't get your point.
>
> My design decision is the kind of decision that led to erasure based
> genericity : it has some drawback, loss of real parametrics instances
> that could be usefull while reflection. But was the right decision at
> the right time or either we would have lots binary compatibility or we
> would still be debating wether or not implementing generics.
> 	
> My proposition on parameter name is analog, it is just meant to be
> used ASAP but does it does not fully solve all the possible
> expectations from this topic scope. Namely, should we call "by
> parameter name" in the language ? and how ?
>
> Room is let for the coming decade ;-) But the propopsition does not
> close doors to anything.
>
>> I suggest you look over the coin-dev mailing list; I entered a  
>> rough sketch
>> of a named parameters proposal near the end of coin. I never wrote  
>> it up
>> because I thought of it far too close to the deadline, and it's  
>> still of
>> such high impact that I doubt it would pass muster for coin.
>
> Yes I've followed the debate :) But, again its my mistake "call by
> parameter names" is a much more complex topic with lots of
> performance/plaform impact. This is not a small language change IMHO.
> Again, I do not look for calling a direct method call using named
> parameters .... just a way to retreive them.
>
> -- --
>
> Joe, yes "late I am" ;-)
>
> FYI, I got this proposition cooking for several months I was not able
> to find time to write & post it to you (pittyfull isn't it).
>
> If we remove the "language change" part (static named parameter) and
> only keep the getParameterNames() API part (keep the regular parameter
> name), do you think this can be pushed to JDK7 even if out of scope of
> coin ? This is a very small change to the API and would solve lot of
> time from lot of people.
>
> I mean, this API (along with the rest of the named parameter spec) was
> removed from JDK6, skiping this in JDK7 means years again to wait for
> it ? I think we are too much getting dependent on tools such as ASM in
> lots of places (JavaEE implementation stacks for instance). And we
> have a good opportunity to remove the dependency for a clean/simple
> solution IMHO.
>
> Best Regards,
> JB



From brucechapman at paradise.net.nz  Mon Apr 20 03:37:05 2009
From: brucechapman at paradise.net.nz (Bruce Chapman)
Date: Mon, 20 Apr 2009 22:37:05 +1200
Subject: PROTOTYPE:
In-Reply-To: <11482659.1238468832504.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
References: <11482659.1238468832504.JavaMail.root@mswamui-andean.atl.sa.earthlink.net>
Message-ID: <49EC5051.9000705@paradise.net.nz>

A prototype compiler for the follow proposals

Underscores in numbers
Narrow Hexadecimal and Binary Integer Literals
Byte and Short Integer Literal Suffixes

is now available at
https://kijaro.dev.java.net/servlets/ProjectDocumentList?folderID=11247&expandFolder=11247&folderID=8804

I have bundled them altogether so that the interaction between 
underscores and the others can be assessed and so that the two new 
literal forms can be compared side by side.

There is one fault in the test class, fix that and it should compile and 
run.

-- Joe, should we update the proposals with this information or is this 
email sufficient?


Bruce




From forax at univ-mlv.fr  Mon Apr 20 03:43:45 2009
From: forax at univ-mlv.fr (=?ISO-8859-1?Q?R=E9mi_Forax?=)
Date: Mon, 20 Apr 2009 12:43:45 +0200
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904200030j47c348f5ha40c744d8e9ff246@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>	
	<49EC2008.5040308@univ-mlv.fr>
	<17b2302a0904200030j47c348f5ha40c744d8e9ff246@mail.gmail.com>
Message-ID: <49EC51E1.6@univ-mlv.fr>

Joshua Bloch a ?crit :
> R?mi,
>
> Good question. We did it to eliminate the possibility of name clashes 
> in existing programs. JBoss actually uses the name AutoCloseable. 
> Types in java.lang are automatically imported, and putting 
> AutoCloseable in java.lang.auto avoids this issue. It doesn't make the 
> construct any less usable, as you don't have to mention AutoCloseable 
> explicitly to use the construct.
>
> Josh

I don't like the fact that the JDK will contains a package with only one 
interface
just to avoid name clash that is hypothetical because classes of the 
current package are imported
before java.lang ones and everybody should avoid to use import *.

In my opinion, (which is biased) , I prefer sacrificing  source backward 
compatibility to having to take
15 minutes each year because I will have to explain to my students why 
the package
java.lang.auto with one interface exists.

Else what about renaming (yes again) AutoCloseable to ARMCloseable ?

R?mi


From reinier at zwitserloot.com  Mon Apr 20 03:47:17 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Mon, 20 Apr 2009 12:47:17 +0200
Subject: Automatic Resource Management, V.2
In-Reply-To: <4b4f45e00904200231p9ce1625o84f7281ccc514b78@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<4b4f45e00904200231p9ce1625o84f7281ccc514b78@mail.gmail.com>
Message-ID: <1386C5FF-8568-439B-AA4C-2FCDF8663D00@zwitserloot.com>

The usage of package java.lang.auto isn't neccessary; classes in your  
own package always take precedence over java.lang classes, and any  
import statement that clashes with a java.lang class takes precedence  
over java.lang.

In other words, if there is an interface named 'jboss.AutoCloseable',  
then all classes in the jboss package will automatically use that  
AutoCloseable. Any code not in the jboss package that includes the  
statement "import jboss.AutoCloseable", will also use jboss's  
AutoCloseable. Client code (that is, code that USES trywith blocks)  
never needs to know about the name 'AutoCloseable' to use them. Any  
code that wants to be an ARM-style closable that is in jboss code will  
need be explicit:

public class IAmClosable implements java.lang.AutoCloseable {
     private AutoCloseable jbossAutoCloseable;
     public void close() {}
}

but such code has to be explicit even if AutoCloseable was moved to  
java.lang.auto as well, so I doubt thats relevant.

A search through a lot of java libraries did not produce any (public  
API) results for 'AutoCloseable':

http://myjavadoc.net/search/search-java.php/AutoCloseable

http://www.google.com/codesearch?hl=en&lr=&q=AutoCloseable+lang%3Ajava&sbtn=Search

So it seems that org.jboss.remoting.spi.AutoCloseable is the only one.

So, the only remaining issues are the following:

A) Confusion for jboss and whatever other library(ies) are lurking out  
there with an AutoCloseable. Forgetting to import the 'right'  
AutoCloseable gets you the 'wrong' one. However, this confusion is  
pretty much unavoidable; just like when Iterable was added, seeing the  
words 'AutoCloseable' in a sourcefile will instinctivly make a java  
programmer think it must be java.lang.(auto.)AutoCloseable. There's a  
java puzzler dedicated to this principle, which creates a local  
version of String. In other words, putting AutoCloseable in another  
package doesn't help all that much. So, I say: not important enough;  
not enough applicable classes and the alternative doesn't clear up  
enough confusion.

B) trying to import "jboss.*" will NOT take precedence over the  
implicit java.lang.* import; instead javac emits a compiler error:

bar/Bar.java:7: reference to Integer is ambiguous, both class  
bla.Integer in bla and class java.lang.Integer in java.lang match
		Integer y = new Integer(12);

So, its technically true there could be a migration compatibility  
issue, but I wouldn't be surprised if there isn't a single line of  
java code in existence that actually would run into this problem. I  
say: Not important enough; star imports are rarely used, there aren't  
many packages where this conflict can occur, java.lang.Iterable had  
the same problem and I've never seen a complaint there either, and a  
compiler error that hints at the problem (as above) is the next-best- 
thing to just working normally.


If I weigh these issues against creating a new package in the  
java.lang space, as well as putting only 1 type inside it, as well as  
being inconsistent with how java.lang.Iterable was handled (which  
could easily have been put in java.util if this had been any concern  
back then) I think its clear that just putting AutoCloseable in  
java.lang is preferable.



  --Reinier Zwitserloot
Like it? Tip it!
http://tipit.to



On Apr 20, 2009, at 11:31, Stephen Colebourne wrote:

> 2009/4/20 Joshua Bloch <jjb at google.com>:
>> * 3. Does the construct work properly with ?decorated? resources?*
>>    try (FileReader fr = new FileReader(path) {
>>        try (BufferedReader br = new BufferedReader(fr) {
>>            ... // Use buffered reader
>>        }
>>    }
>
> Would this section be better written:
>
>    try (FileReader fr = new FileReader(path); BufferedReader br = new
> BufferedReader(fr) {
>          ... // Use buffered reader
>    }
>
> ie. the second resource is derived from the first within one ARM  
> block.
>
> (More generally, I think I'd prefer a single resource per ARM, as I
> think its a lot clearer overall and more consistent, but since you've
> allowed it in the proposal, I assume you'd want to keep to that
> style.)
>
> Stephen
>



From brucechapman at paradise.net.nz  Mon Apr 20 04:00:34 2009
From: brucechapman at paradise.net.nz (Bruce Chapman)
Date: Mon, 20 Apr 2009 23:00:34 +1200
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
Message-ID: <49EC55D2.6010305@paradise.net.nz>

Joshua Bloch wrote:
> Fellow Coiners,
>
> Thanks for all your feedback on the Automatic Resource Management proposal.
>  I have revised the proposal in light of these comments.  The new version
> (V.2) can be seen at this URL:
> http://docs.google.com/Doc?id=ddv8ts74_3fs7483dp . It is included below for
> archival purposes.
>
>    Josh
>   
- SNIP -
> An automatic resource management statement with a single resource expression
> and no *Finally* or *Catches* would behave as if replaced by the following
> source code:
>
>
>
> {
>
>     final *T**ype* #localVar = *Expression*;
>   
The type in the generated declaration above could simply be AutoClosable 
rather than the specific type of the expression? (and especially so if 
the expression had a type which was an intersection type - which I think 
is possible).

Bruce




From paul.martin at gmail.com  Mon Apr 20 05:32:33 2009
From: paul.martin at gmail.com (Paul Martin)
Date: Mon, 20 Apr 2009 13:32:33 +0100
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
Message-ID: <4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com>

Hi,

I've got a few minor comments/questions:

> To support automatic retention of suppressed exceptions (for high-quality
> diagnostics), we add these methods to java.lang.Throwable:
>
...
> /**
>  * Returns an array containing all of the exceptions that were suppressed,
>  * typically by the automatic resource management statement, in order to
>  * deliver this exception.
>  */
> public Throwable[] getSuppressedExceptions().

Why not return a List<Throwable> instead of an array (since
Collections are generally nicer to use)?  If an array is to be
returned, is it a copy, or does changing its contents affect the
Throwable?  Will an empty array or null be returned if there are no
suppressed exceptions?

Would it be useful to distinguish exceptions suppressed by
AutoCloseable and those suppressed by other mechanisms (e.g. with an
associated enum or message, or even an EnumMap of <Cause, Exception>)?
 Why exceptions were suppressed might be useful in future (unless it
is expected that only AutoCloseable will suppress exceptions, or that
it is unlikely that there will be multiple suppressors of exceptions).

> The printStackTrace method should be modified to append the stack traces for
> any suppressed exceptions.

This might be difficult, particularly where there are a number of
"cause" and "suppressed" exceptions (each of which might have their
own) - it might be hard to associate each exception with its parent in
the output (whereas currently "cause" has only one immediate parent
and so it is easy to follow such a stack trace).  This would also have
an impact on the TESTING section (where "cause" exceptions should also
be included).

> *DESIGN FAQ*

It might be nice to answer "Why is the 'try' keyword used instead of
alternatives such as 'using'?" (though maybe only once the change has
been released - probably not important at this stage).

> *2. Does the construct allow access to resources after an exception is
> thrown from within the block, but before the resource is closed?*

I didn't really understand why this had to be the case - was it
because resource variables are final and initialised in order, so if
one resource fails to initialise it will not be in scope at all, so we
cannot guarantee that any will be in scope in explicit catch and
finally clauses?  If so, couldn't they just be set to null if they
were not initialised correctly?  As you say, it is probably not a
major issue in any case.

> * 3. Does the construct work properly with ?decorated? resources?*
...
>     try (FileReader fr = new FileReader(path) {
>         try (BufferedReader br = new BufferedReader(fr) {
>             ... // Use buffered reader
>         }
>     }

You are missing a closing ) on each of the try lines.

Could this be rewritten as the following?

try (FileReader fr = new FileReader(path); BufferedReader br = new
BufferedReader(fr)) {
           ... // Use buffered reader
}

> * 4. Does the construct support resource types whose termination method has
...
> with an annotation. But this violates the rule that annotations cannot
> change the semantics of a program (JLS ?9.7). The other is to use an actual

I can't see such a rule in the JLS - the closest seems to be "The
purpose of an annotation is simply to associate information with the
annotated program element" - is that what is meant?

> *5. Some failures of the **close** method can be safely ignored (e.g.,
...
> these exceptions are ignored. If you feel you must ignore them, there is a
> workaround, but it isn't pretty:

Could you use a decorator to simplify the code a little, such as:

public class HideAutoCloseableExceptionsAdapter implements AutoCloseable {
	private final AutoCloseable delegate;
	public HideAutoCloseableExceptionsAdapter(AutoCloseable delegate) {
		this.delegate = delegate;
	}
	@Override
	public void close() {
		try {
			delegate.close();
		} catch (Exception e) {
			// Do nothing
		}
	}
}

static void copy(String src, String dest) throws IOException {
       InputStream in = new FileInputStream(src);
       try (new HideAutoCloseableExceptionsAdapter(in)) {
           try(OutputStream out = new FileOutputStream(dest)) {
               byte[] buf = new byte[8192];
               int n;
               while ((n = in.read(buf)) >= 0)
                   out.write(buf, 0, n);
           }
       }
   }
}

Otherwise the proposal looks good to me.

Regards,

Paul


From jjb at google.com  Mon Apr 20 07:09:45 2009
From: jjb at google.com (Joshua Bloch)
Date: Mon, 20 Apr 2009 07:09:45 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <4b4f45e00904200231p9ce1625o84f7281ccc514b78@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<4b4f45e00904200231p9ce1625o84f7281ccc514b78@mail.gmail.com>
Message-ID: <17b2302a0904200709u4a2d3ecfh18888bdc87ab8e61@mail.gmail.com>

Stephen,
On Mon, Apr 20, 2009 at 2:31 AM, Stephen Colebourne <scolebourne at joda.org>wrote:

> 2009/4/20 Joshua Bloch <jjb at google.com>:
> > * 3. Does the construct work properly with ?decorated? resources?*
> >    try (FileReader fr = new FileReader(path) {
> >        try (BufferedReader br = new BufferedReader(fr) {
> >            ... // Use buffered reader
> >        }
> >    }
>
> Would this section be better written:
>
>    try (FileReader fr = new FileReader(path); BufferedReader br = new
> BufferedReader(fr) {
>          ... // Use buffered reader
>    }
>
> ie. the second resource is derived from the first within one ARM block.


Yes, thanks.  Fixed.

>
>
> (More generally, I think I'd prefer a single resource per ARM, as I
> think its a lot clearer overall and more consistent, but since you've
> allowed it in the proposal, I assume you'd want to keep to that
> style.)


Yes.  May people really care about keeping the nesting depth low, and the
ability to combine resources in a single ARM statement does that for them.

          Thanks again,

          Josh


From jjb at google.com  Mon Apr 20 07:15:05 2009
From: jjb at google.com (Joshua Bloch)
Date: Mon, 20 Apr 2009 07:15:05 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <49EC51E1.6@univ-mlv.fr>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<49EC2008.5040308@univ-mlv.fr>
	<17b2302a0904200030j47c348f5ha40c744d8e9ff246@mail.gmail.com>
	<49EC51E1.6@univ-mlv.fr>
Message-ID: <17b2302a0904200715u267785d5y46bc86fb39aa61ce@mail.gmail.com>

R?mi,
It is possible that we may end up with some other "auto" interfaces in
future.  And as mentioned, a package-based solution is 100% safe, as it
requires explicit import.  Of course I agree with you that package with a
single class in it is a bit suspect.  I think this is best left as an "open
issue" for the time being.

      Thanks,

      Josh

On Mon, Apr 20, 2009 at 3:43 AM, R?mi Forax <forax at univ-mlv.fr> wrote:

> Joshua Bloch a ?crit :
>
>> R?mi,
>>
>> Good question. We did it to eliminate the possibility of name clashes in
>> existing programs. JBoss actually uses the name AutoCloseable. Types in
>> java.lang are automatically imported, and putting AutoCloseable in
>> java.lang.auto avoids this issue. It doesn't make the construct any less
>> usable, as you don't have to mention AutoCloseable explicitly to use the
>> construct.
>>
>> Josh
>>
>
> I don't like the fact that the JDK will contains a package with only one
> interface
> just to avoid name clash that is hypothetical because classes of the
> current package are imported
> before java.lang ones and everybody should avoid to use import *.
>
> In my opinion, (which is biased) , I prefer sacrificing  source backward
> compatibility to having to take
> 15 minutes each year because I will have to explain to my students why the
> package
> java.lang.auto with one interface exists.
>
> Else what about renaming (yes again) AutoCloseable to ARMCloseable ?
>
> R?mi
>


From jjb at google.com  Mon Apr 20 07:22:44 2009
From: jjb at google.com (Joshua Bloch)
Date: Mon, 20 Apr 2009 07:22:44 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <1386C5FF-8568-439B-AA4C-2FCDF8663D00@zwitserloot.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<4b4f45e00904200231p9ce1625o84f7281ccc514b78@mail.gmail.com>
	<1386C5FF-8568-439B-AA4C-2FCDF8663D00@zwitserloot.com>
Message-ID: <17b2302a0904200722i58b261dav25f00d7c9466177f@mail.gmail.com>

Reinier,

These arguments are quite persuasive.  Let's see what (if anything) others
have to say, but I agree with you and R?mi at this point.

          Josh

On Mon, Apr 20, 2009 at 3:47 AM, Reinier Zwitserloot <
reinier at zwitserloot.com> wrote:

> The usage of package java.lang.auto isn't neccessary; classes in your own
> package always take precedence over java.lang classes, and any import
> statement that clashes with a java.lang class takes precedence over
> java.lang.
>
> In other words, if there is an interface named 'jboss.AutoCloseable', then
> all classes in the jboss package will automatically use that AutoCloseable.
> Any code not in the jboss package that includes the statement "import
> jboss.AutoCloseable", will also use jboss's AutoCloseable. Client code (that
> is, code that USES trywith blocks) never needs to know about the name
> 'AutoCloseable' to use them. Any code that wants to be an ARM-style closable
> that is in jboss code will need be explicit:
>
> public class IAmClosable implements java.lang.AutoCloseable {
>     private AutoCloseable jbossAutoCloseable;
>     public void close() {}
> }
>
> but such code has to be explicit even if AutoCloseable was moved to
> java.lang.auto as well, so I doubt thats relevant.
>
> A search through a lot of java libraries did not produce any (public API)
> results for 'AutoCloseable':
>
> http://myjavadoc.net/search/search-java.php/AutoCloseable
>
>
> http://www.google.com/codesearch?hl=en&lr=&q=AutoCloseable+lang%3Ajava&sbtn=Search
>
> So it seems that org.jboss.remoting.spi.AutoCloseable is the only one.
>
> So, the only remaining issues are the following:
>
> A) Confusion for jboss and whatever other library(ies) are lurking out
> there with an AutoCloseable. Forgetting to import the
> 'right' AutoCloseable gets you the 'wrong' one. However, this confusion is
> pretty much unavoidable; just like when Iterable was added, seeing the words
> 'AutoCloseable' in a sourcefile will instinctivly make a java programmer
> think it must be java.lang.(auto.)AutoCloseable. There's a java puzzler
> dedicated to this principle, which creates a local version of String. In
> other words, putting AutoCloseable in another package doesn't help all that
> much. So, I say: not important enough; not enough applicable classes and the
> alternative doesn't clear up enough confusion.
>
> B) trying to import "jboss.*" will NOT take precedence over the implicit
> java.lang.* import; instead javac emits a compiler error:
>
> bar/Bar.java:7: reference to Integer is ambiguous, both class bla.Integer
> in bla and class java.lang.Integer in java.lang match
> Integer y = new Integer(12);
>
> So, its technically true there could be a migration compatibility issue,
> but I wouldn't be surprised if there isn't a single line of java code in
> existence that actually would run into this problem. I say: Not important
> enough; star imports are rarely used, there aren't many packages where this
> conflict can occur, java.lang.Iterable had the same problem and I've never
> seen a complaint there either, and a compiler error that hints at the
> problem (as above) is the next-best-thing to just working normally.
>
>
> If I weigh these issues against creating a new package in the java.lang
> space, as well as putting only 1 type inside it, as well as being
> inconsistent with how java.lang.Iterable was handled (which could easily
> have been put in java.util if this had been any concern back then) I think
> its clear that just putting AutoCloseable in java.lang is preferable.
>
>
>
>  --Reinier Zwitserloot
> Like it? Tip it!
> http://tipit.to
>
>
>
> On Apr 20, 2009, at 11:31, Stephen Colebourne wrote:
>
> 2009/4/20 Joshua Bloch <jjb at google.com>:
>
> * 3. Does the construct work properly with ?decorated? resources?*
>
>    try (FileReader fr = new FileReader(path) {
>
>        try (BufferedReader br = new BufferedReader(fr) {
>
>            ... // Use buffered reader
>
>        }
>
>    }
>
>
> Would this section be better written:
>
>    try (FileReader fr = new FileReader(path); BufferedReader br = new
> BufferedReader(fr) {
>          ... // Use buffered reader
>    }
>
> ie. the second resource is derived from the first within one ARM block.
>
> (More generally, I think I'd prefer a single resource per ARM, as I
> think its a lot clearer overall and more consistent, but since you've
> allowed it in the proposal, I assume you'd want to keep to that
> style.)
>
> Stephen
>
>
>


From jjb at google.com  Mon Apr 20 07:34:21 2009
From: jjb at google.com (Joshua Bloch)
Date: Mon, 20 Apr 2009 07:34:21 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <49EC55D2.6010305@paradise.net.nz>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<49EC55D2.6010305@paradise.net.nz>
Message-ID: <17b2302a0904200734j31ef60afueb2eae2c95a44399@mail.gmail.com>

Bruce,

On Mon, Apr 20, 2009 at 4:00 AM, Bruce Chapman <brucechapman at paradise.net.nz
> wrote:

>
>>
>>    final *T**ype* #localVar = *Expression*;
>>
>>
> The type in the generated declaration above could simply be AutoClosable
> rather than the specific type of the expression?


Unfortunately it could not: if it were, the ARM statement could throw the
wrong exception type.  If Expression is of a subclass of AutoCloseable whose
close method throws a particular set of exceptions (or none at all), it's
important that the enclosing statement behaves as if #localVar.close()
throws exactly the same set of exceptions.  You are correct that it's not
possible to express this in declaration in the source language, but I
believe the compiler will have no trouble doing it.  I will confirm this.
 This issue does merit a note in the spec, and I will write one shortly.

              Thanks,

              Josh


From Ruslan at Shevchenko.Kiev.UA  Mon Apr 20 07:58:58 2009
From: Ruslan at Shevchenko.Kiev.UA (Ruslan Shevchenko)
Date: Mon, 20 Apr 2009 17:58:58 +0300 (EEST)
Subject: Syntax patterns: more statistics.
Message-ID: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>

Good day, community !

 I want to share some statistics about java usage patterns, related to
some of coin-dev proposals.

Main changes from previous post are:
  - added counts for 'if' syntax constructions, so we can say, hom many
 percents of if's can be eliminated by elvis operator ( [4-5]%)
  - added counts for 'catch' syntax constructions, so we can say that
multicath eliminate 6-8% of all catch clauses.
  - added count for big integers integers (where undescore can be
applicable, I guess this is x: x > 100000 || x < -10000) and for all
integer literals.
   (underscore can be applicable to near 1%)
  - added count for object-switch proposal by Ulf Zibis (refining, that
Left/Right part of expressions are first operand in equalirty expression
or object in method call)
  - added count for rethrow proposal by Mark Mahieu (near 50% of all
catches in some packages (!) ).
  - added count for catches inside finally block. (Is this is a real
problem [?]).

If anybody whant run checks on own dataset or/and add own check
definitions: all  procedure is the same as in my previous letter (see
http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001442.html)
except URL for last version
 is
http://datacenter.gradsoft.ua/public.repository/ua.gradsoft/javachecker/installations/JavaCheckerSourceInstaller-2.5.0p1.jar

Now summary statistics for some well-known packages:
jetty (web server)
all catchs      :       281
all ifs :       764
all integer literals    :       2903
big integer literals(undescores)        :       25
byte literal    :       52
catch in finally        :       3
elvis   :       43
instanceof switch       :       8
loop with remove        :       0
multi catch     :       22
object switch   :       31
rethrow clause  :       34
string in switch        :       19
Files:187

gwt-users (google java ajax client library)
all catchs      :       171
all ifs :       735
all integer literals    :       2282
big integer literals(undescores)        :       24
byte literal    :       2
catch in finally        :       2
elvis   :       30
instanceof switch       :       6
loop with remove        :       5
multi catch     :       9
object switch   :       27
rethrow clause  :       84
string in switch        :       10
Files:920

hibernate (ORM toolkit)
all catchs      :       650
all ifs :       2410
all integer literals    :       3240
big integer literals(undescores)        :       12
byte literal    :       1
catch in finally        :       27
elvis   :       182
instanceof switch       :       28
loop with remove        :       12
multi catch     :       25
object switch   :       94
rethrow clause  :       450
string in switch        :       86
Files:1372

openjdk7 (standard java library)
all catchs      :       8404
all ifs :       28494
all integer literals    :       124356
big integer literals(undescores)        :       4066
byte literal    :       1454
catch in finally        :       103
elvis   :       877
instanceof switch       :       318
loop with remove        :       62
multi catch     :       411
object switch   :       1363
rethrow clause  :       3264
string in switch        :       445
Files:9252

Hope, this data will be useful in some cases.
Regards !




From jjb at google.com  Mon Apr 20 08:14:36 2009
From: jjb at google.com (Joshua Bloch)
Date: Mon, 20 Apr 2009 08:14:36 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com>
Message-ID: <17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com>

Paul,
Thanks for the feedback.


> > /**
> >  * Returns an array containing all of the exceptions that were
> suppressed,
> >  * typically by the automatic resource management statement, in order to
> >  * deliver this exception.
> >  */
> > public Throwable[] getSuppressedExceptions().
>
> Why not return a List<Throwable> instead of an array (since
> Collections are generally nicer to use)?


I did think about this, but I opted to stick with the pattern in enum types'
values() method.  That decision was made for performance. Arguably the
performance issues are less important here, and the winds of change have
blown further away from arrays since then, so I'm definitely open to
switching this to a List if others think it's the right thing to do.


>  If an array is to be
> returned, is it a copy, or does changing its contents affect the
> Throwable?


A copy.  The spec should have made this explicit, and will do so.


>  Will an empty array or null be returned if there are no
> suppressed exceptions?


It goes without saying (literally) that an empty array will be returned (see
Effective Java Item 43).

>
>
> Would it be useful to distinguish exceptions suppressed by
> AutoCloseable and those suppressed by other mechanisms (e.g. with an
> associated enum or message, or even an EnumMap of <Cause, Exception>)?
>  Why exceptions were suppressed might be useful in future (unless it
> is expected that only AutoCloseable will suppress exceptions, or that
> it is unlikely that there will be multiple suppressors of exceptions).


This feels like overkill to me.

>
>
> > The printStackTrace method should be modified to append the stack traces
> for
> > any suppressed exceptions.
>
> This might be difficult, particularly where there are a number of
> "cause" and "suppressed" exceptions (each of which might have their
> own) - it might be hard to associate each exception with its parent in
> the output (whereas currently "cause" has only one immediate parent
> and so it is easy to follow such a stack trace).


I did think about this, and came to the conclusion that it wasn't so bad.
 The main problem is the "intermingling" of causes and suppressed
exceptions.  I will come up with a format and put an example in the spec.


>  This would also have
> an impact on the TESTING section (where "cause" exceptions should also
> be included).


True!  I'll fix this later today.


>
>
> > *DESIGN FAQ*
>
> It might be nice to answer "Why is the 'try' keyword used instead of
> alternatives such as 'using'?" (though maybe only once the change has
> been released - probably not important at this stage).


Yes.  I'm sure the DESIGN FAQ will grow over time.  As you can see, my
current focus was on code samples for how to achieve specific effects.

>
>
> > *2. Does the construct allow access to resources after an exception is
> > thrown from within the block, but before the resource is closed?*
>
> I didn't really understand why this had to be the case - was it
> because resource variables are final and initialised in order, so if
> one resource fails to initialise it will not be in scope at all, so we
> cannot guarantee that any will be in scope in explicit catch and
> finally clauses?


The only other reasonable rule that I could come up with was that the
finally block was executed before the close, but only if all the resource
declarations complete successfully, and that all resources were in scope,
but these semantics are far less desirable.  Perhaps this rates an FAQ.

 If so, couldn't they just be set to null if they
> were not initialised correctly?


It turns out that this is not an issue, as the catch/finally blocks won't
get executed if any declarations fail.


>  As you say, it is probably not a
> major issue in any case.


Yep.


> > * 3. Does the construct work properly with ?decorated? resources?*
> ...
> >     try (FileReader fr = new FileReader(path) {
> >         try (BufferedReader br = new BufferedReader(fr) {
> >             ... // Use buffered reader
> >         }
> >     }
>
> You are missing a closing ) on each of the try lines.


Yep.

>
>
> Could this be rewritten as the following?
>
> try (FileReader fr = new FileReader(path); BufferedReader br = new
> BufferedReader(fr)) {
>           ... // Use buffered reader
> }
>

Yep.  Done.

>
>
> > * 4. Does the construct support resource types whose termination method
> has
> ...
> > with an annotation. But this violates the rule that annotations cannot
> > change the semantics of a program (JLS ?9.7). The other is to use an
> actual
>
> I can't see such a rule in the JLS - the closest seems to be "The
> purpose of an annotation is simply to associate information with the
> annotated program element" - is that what is meant?


Yes.  That's how that prose has always been interpreted.

>
>
> > *5. Some failures of the **close** method can be safely ignored (e.g.,
> ...
> > these exceptions are ignored. If you feel you must ignore them, there is
> a
> > workaround, but it isn't pretty:
>
> Could you use a decorator to simplify the code a little, such as:
>
> public class HideAutoCloseableExceptionsAdapter implements AutoCloseable {
>        private final AutoCloseable delegate;
>        public HideAutoCloseableExceptionsAdapter(AutoCloseable delegate) {
>                this.delegate = delegate;
>        }
>        @Override
>        public void close() {
>                try {
>                        delegate.close();
>                } catch (Exception e) {
>                        // Do nothing
>                 }
>        }
> }
>
> static void copy(String src, String dest) throws IOException {
>       InputStream in = new FileInputStream(src);
>        try (new HideAutoCloseableExceptionsAdapter(in)) {
>            try(OutputStream out = new FileOutputStream(dest)) {
>               byte[] buf = new byte[8192];
>               int n;
>               while ((n = in.read(buf)) >= 0)
>                   out.write(buf, 0, n);
>           }
>       }
>   }
> }
>

Yes; you could do that.  Of course you'd have to write a separate decorator
for every such type.  But it's worth mentioning that in the FAQ, and I will
do so.

         Thanks again,

         Josh


From mthornton at optrak.co.uk  Mon Apr 20 08:25:27 2009
From: mthornton at optrak.co.uk (Mark Thornton)
Date: Mon, 20 Apr 2009 16:25:27 +0100
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>	<4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com>
	<17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com>
Message-ID: <49EC93E7.10909@optrak.co.uk>

Joshua Bloch wrote:
>
> I did think about this, but I opted to stick with the pattern in enum types'
> values() method.  That decision was made for performance. Arguably the
> performance issues are less important here, and the winds of change have
> blown further away from arrays since then, so I'm definitely open to
> switching this to a List if others think it's the right thing to do.
>
>   
Surely the VM is able to optimise away the trivial accessors in an 
immutable List backed by an array, and has been capable of this for 
quite a while? I really wonder if there was ever any significant 
performance gain obtained from this choice. In any case I vote for a List.

Mark Thornton



From neal at gafter.com  Mon Apr 20 08:30:48 2009
From: neal at gafter.com (Neal Gafter)
Date: Mon, 20 Apr 2009 08:30:48 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <1386C5FF-8568-439B-AA4C-2FCDF8663D00@zwitserloot.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com> 
	<4b4f45e00904200231p9ce1625o84f7281ccc514b78@mail.gmail.com> 
	<1386C5FF-8568-439B-AA4C-2FCDF8663D00@zwitserloot.com>
Message-ID: <15e8b9d20904200830x2063e5bftf67725cc816464d5@mail.gmail.com>

On Mon, Apr 20, 2009 at 3:47 AM, Reinier Zwitserloot <
reinier at zwitserloot.com> wrote:

> The usage of package java.lang.auto isn't neccessary; classes in your
> own package always take precedence over java.lang classes, and any
> import statement that clashes with a java.lang class takes precedence
> over java.lang.


Explicit *-imports do not take precedence over the implicit import of
java.lang.*.


From neal at gafter.com  Mon Apr 20 08:46:12 2009
From: neal at gafter.com (Neal Gafter)
Date: Mon, 20 Apr 2009 08:46:12 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
Message-ID: <15e8b9d20904200846v61dad02amdff38481dc91c0a0@mail.gmail.com>

On Sun, Apr 19, 2009 at 11:45 PM, Joshua Bloch <jjb at google.com> wrote:

> Thanks for all your feedback on the Automatic Resource Management proposal.
>  I have revised the proposal in light of these comments.


I am disappointed to see that this revision addresses none of the ergonomic
issues reported earlier, not even those that were identified in the previous
ARM proposal years ago and for which a solution was promised in the
revision.


From neal at gafter.com  Mon Apr 20 08:52:22 2009
From: neal at gafter.com (Neal Gafter)
Date: Mon, 20 Apr 2009 08:52:22 -0700
Subject: SUBMISSION : A second look on "named parameters" / Clarification 
	on the scope
In-Reply-To: <E807B68F-1621-4AD7-8052-146B0C45FB89@zwitserloot.com>
References: <2dc3bd00904200118s35e085fdk6f4ef3cac83cd6e9@mail.gmail.com> 
	<E807B68F-1621-4AD7-8052-146B0C45FB89@zwitserloot.com>
Message-ID: <15e8b9d20904200852q70bf48bcm2c9beb8685902488@mail.gmail.com>

Reiner-

This is a library proposal, not a language proposal, so it doesn't need to
be done inside project Coin.

-Neal

On Mon, Apr 20, 2009 at 3:16 AM, Reinier Zwitserloot <
reinier at zwitserloot.com> wrote:

> Ah, now I understand.
>
> I've got a much simpler proposal to address this issue.
>
> NB: Joe, I know coin's long gone, but perhaps consider this one anyway
> - it seems to me that some sort of named parameters proposal is likely
> to be accepted in the future, and adding names now should ease
> transition. As part of the effort I've listed all possibly
> complication I can come up with, at the end.
>
> Proposal:
>
>
> Starting from the new class file format introduced in java7 (due to
> module support, the class format is definitely getting a version
> bump), all compilers MUST put the names of the parameters in the class
> file (javac -g style), and obfuscators/compressors/whatever MUST NOT
> remove this; a class file with version v50 (or whatever number its
> going to end up being) won't even pass the verifier without the names
> in place.
>
> Add an API call on the java.lang.reflect.Method object to obtain the
> names of the parameters (returns a String[], or 'null' if they aren't
> there. Calling this on a param-less method returns an empty array, not
> null). Having the names is an all-or-nothing situation: Either the
> names are all there and this call works, or some/all are missing, and
> then this call does not work. I'm not sure if you can even have just a
> few names defined in the .class file format, but even if you can, that
> situation should be so extremely rare, its not worth writing up a
> complicated rule for). It is guaranteed that if the array exists (is
> not null), then each array element is not null.
>
> Voila. No need to turn in a proposal that's more complicated than most
> just to solve this simple problem.
>
> Complications:
>
> A) It would no longer be possible to rewrite a v49 and below class
> without debug info into a v50 and up class file without having the
> source file, but I don't actually know of any tools that attempt to do
> this.
>
> B) Code that generates class files on the fly (like proxy generators
> and the like) will need to consider the names of method parameters if/
> when they update the class file format they generate to v50+. A proxy
> generator has issues when it is trying to generate a v50+ proxy where
> its input object's class spec AND the input interface to proxy on are
> both v49- without debug info, for example.
>
> C) A (bad) quick-fix for either of the above issues is to just use
> 'arg0', 'arg1', 'arg2', analogous to what e.g. eclipse does when
> showing method signatures for methods in classes where there is no
> source, no debug info and no javadoc. This is not at all the right
> idea. A small risk that the class file format documentation should
> mention as not being appropriate unless there is absolutely no other
> option.
>
> D) Most code these days ships with source, or javadoc, or debug info,
> so that auto-complete shows the proper names for each parameter, but
> this certainly isn't true for /all/ java code out there. After this
> change, method param names become visible to all. This may not be a
> desired side-effect for programming shops that export libraries to
> clients where their method parameter names are inappropriate (swear
> words, or 'x', 'y', and 'z' and this creates deserved but nevertheless
> unexpected ridicule for sucking at programming style). I think this is
> an acceptable price to pay. Parameters are method-local which are
> extremely easy to rename with your friendly neighbourhood IDE's
> refactor tool.
>
> E) While technically the names are NOT part of API, and you CAN freely
> change names around without breaking any code, old or new, the names
> still do become a little more enshrined as at least almost part of the
> public API. This is already the case to some extent (param names show
> up in various tooling support such as javadoc and auto-completing
> IDEs) but this change would move parameter names a little more towards
> a complete member of public API. This is an issue, but its also the
> point of this proposal: Move towards a java world where parameter
> names are universally available and are meaningful. I don't think this
> is a serious problem, because A) names already have a flavour of
> importance right now, and B) While they become more important with
> this proposal, they still aren't true public API, and changing names
> even after this proposal is accepted is not backwards incompatible.
>
> F) Confusion may arise when these names are unintentionally taken as
> being either part of public API, or being hierarchical; they are in
> fact neither. For example, this proposal makes no attempt to harmonize
> name conflicts; if interface A has void foo(int bar), and interface B
> has void foo(int baz), you can still of course write a class that
> implements both of these. You can even name your foo's parameter
> 'floobargle', of course. The aim of this proposal does not involve
> making parameter names inherit sensibly.
>
>
>  --Reinier Zwitserloot
>
>
>
> On Apr 20, 2009, at 10:18, Jean-Baptiste Bugeaud wrote:
>
> > Hello Reinier, Hello Joe,
> >
> > Thanks for your feedback.
> >
> > 2009/4/19 Reinier Zwitserloot <reinier at zwitserloot.com>:
> >> Your proposal is very incomplete. Three major nits:
> >>
> >> A. Did I miss something, or did you totally forget to include an
> >> example of
> >> calling a method with named parameters? Something like:
> >>
> >> doLogin(user: "foobar", password: new char[] { 'a', 'b', 'c' })
> >
> > Reiner, I think my submission name is misleading everybody. This is
> > not the same thing you debate some times back. My mistake ... I should
> > have clarified from the start : I do not look at adding direct call by
> > parameter name into the language (say "? la" ObjectiveC). But simply a
> > reliable way access to parameter name and name a parameter's name in
> > static way thru time. See bug 6444738 for differences.
> >
> > Parameter names are very usefull information in most cases, and at
> > this time, either implementers use duplicate annotation (dummy
> > annotations storing again the same name) or they use tools such as ASM
> > to workaround the lack of API in the JDK.
> >
> > At the begining, I thought this requirement did not required a small
> > synthax language change : a new API would be enough. But soon I
> > realized that introducing name parameter that are static thru time,
> > introduce anyway a new paradigm in the language that developer should
> > be able to control directly : do I want this parameter name to be
> > static thu time ? or do I want to let the compiler decide as usual ?
> >
> > A compiler option is not the suitable tool for this.
> > If this is a global switch, it will not offer the fine grain required.
> > If this is a per class/per package option, it will clutter the
> > command line.
> > And in both cases, it will not offer paradigm separation with the
> > legacy. Thus you can not rely on the parameter name because you never
> > know if developper has stored the name accidentaly or for purpose.
> >
> >> B. Why static? You might as well have picked 'strictfp' - it's a
> >> total
> >> non-sequitur choice. Re-use of existing keywords is not really a
> >> panacea; it
> >> waters down the anchoring ability of a keyword to virtually
> >> nothing. I'm not
> >> sure if context-sensitive keywords are any better, but java7 is
> >> already
> >> going to have at least one ('module'), so don't beat around the
> >> bush and
> >> just call it 'named'). Could be just me, but introducing a change
> >> which is
> >> not backwards compatible IF you have a type that's called
> >> 'named' (written
> >> just like that, all-lower case), is not something I find
> >> troublesome in the
> >> least. That's very ugly code, and a migration tool can fix this
> >> easily.
> >
> > Because of the definition a dictionary gives of it : something like
> > "showing little change" is exactly what I meant for this paradigm. And
> > no "strictfp", as well as "const" and "goto" are not matching, you see
> > ;-)
> >
> > If you think that this worth integrating a new keywork, then there is
> > room for debate. I think static fits perfectly and is clear enough.
> > AFAIK, we already have final that is contextual? why not static too ?
> > final is already stretched between two things : do not overload member
> > and do not reasign variable.
> >
> > With the proposed language changed static modifier will be stretched
> > between static thru instances for members and static thru time for
> > variables.
> >
> >> C. You don't mention having default values for parameters, which is
> >> sort of
> >> the point of this exercise (otherwise you really still need
> >> builders  ; any
> >> method that has so many parameters that they need names probably
> >> needs a
> >> builder, and without defaults, not providing one and instead
> >> relying on
> >> named params is just an inferior bandaid to your ugly API; to get
> >> it right
> >> you STILL need to provide a builder. If, however, parameters can have
> >> defaults, then you no longer need to make builders at all).
> >
> > This is because I am not asking for named call of method ... simply
> > for a way to access name of parameter. Just a completely different
> > topic.
> > I don't see why a parameter on an EJB is not meanfull for the external
> > ? same for an webservice ? why a parameter name could not be meanfull
> > ? I don't get your point.
> >
> > My design decision is the kind of decision that led to erasure based
> > genericity : it has some drawback, loss of real parametrics instances
> > that could be usefull while reflection. But was the right decision at
> > the right time or either we would have lots binary compatibility or we
> > would still be debating wether or not implementing generics.
> >
> > My proposition on parameter name is analog, it is just meant to be
> > used ASAP but does it does not fully solve all the possible
> > expectations from this topic scope. Namely, should we call "by
> > parameter name" in the language ? and how ?
> >
> > Room is let for the coming decade ;-) But the propopsition does not
> > close doors to anything.
> >
> >> I suggest you look over the coin-dev mailing list; I entered a
> >> rough sketch
> >> of a named parameters proposal near the end of coin. I never wrote
> >> it up
> >> because I thought of it far too close to the deadline, and it's
> >> still of
> >> such high impact that I doubt it would pass muster for coin.
> >
> > Yes I've followed the debate :) But, again its my mistake "call by
> > parameter names" is a much more complex topic with lots of
> > performance/plaform impact. This is not a small language change IMHO.
> > Again, I do not look for calling a direct method call using named
> > parameters .... just a way to retreive them.
> >
> > -- --
> >
> > Joe, yes "late I am" ;-)
> >
> > FYI, I got this proposition cooking for several months I was not able
> > to find time to write & post it to you (pittyfull isn't it).
> >
> > If we remove the "language change" part (static named parameter) and
> > only keep the getParameterNames() API part (keep the regular parameter
> > name), do you think this can be pushed to JDK7 even if out of scope of
> > coin ? This is a very small change to the API and would solve lot of
> > time from lot of people.
> >
> > I mean, this API (along with the rest of the named parameter spec) was
> > removed from JDK6, skiping this in JDK7 means years again to wait for
> > it ? I think we are too much getting dependent on tools such as ASM in
> > lots of places (JavaEE implementation stacks for instance). And we
> > have a good opportunity to remove the dependency for a clean/simple
> > solution IMHO.
> >
> > Best Regards,
> > JB
>
>
>


From forax at univ-mlv.fr  Mon Apr 20 09:18:36 2009
From: forax at univ-mlv.fr (=?ISO-8859-1?Q?R=E9mi_Forax?=)
Date: Mon, 20 Apr 2009 18:18:36 +0200
Subject: Automatic Resource Management, V.2
In-Reply-To: <15e8b9d20904200846v61dad02amdff38481dc91c0a0@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<15e8b9d20904200846v61dad02amdff38481dc91c0a0@mail.gmail.com>
Message-ID: <49ECA05C.3030207@univ-mlv.fr>

Neal Gafter a ?crit :
> On Sun, Apr 19, 2009 at 11:45 PM, Joshua Bloch <jjb at google.com> wrote:
>
>   
>> Thanks for all your feedback on the Automatic Resource Management proposal.
>>  I have revised the proposal in light of these comments.
>>     
>
>
> I am disappointed to see that this revision addresses none of the ergonomic
> issues reported earlier, not even those that were identified in the previous
> ARM proposal years ago and for which a solution was promised in the
> revision.
>
>   
It's perhaps crystal clear for everyone but me :)
Could you be a little more specific about the issues your talking about ?

R?mi


From jjb at google.com  Mon Apr 20 09:19:47 2009
From: jjb at google.com (Joshua Bloch)
Date: Mon, 20 Apr 2009 09:19:47 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <15e8b9d20904200846v61dad02amdff38481dc91c0a0@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<15e8b9d20904200846v61dad02amdff38481dc91c0a0@mail.gmail.com>
Message-ID: <17b2302a0904200919l11b78994ueae9c9f146fe32a@mail.gmail.com>

Neal,


> I am disappointed to see that this revision addresses none of the ergonomic
> issues reported earlier, not even those that were identified in the previous
> ARM proposal years ago and for which a solution was promised in the
> revision.
>


I am sorry you're disappointed. I do believe I addressed all the substantive
issues that you raised:

(1) "try" is not a natural keyword for the intended semantics.


You didn't really back this one up.  Other people have commented on what a
great fit they think it is.  So we'll just have to consider it an issue of
taste, on which reasonable men may disagree.


> (2) Checked exceptions from close() should be discarded for some clients.


The revision says this:

*5. Some failures of the **close** method can be safely ignored (e.g.,
closing a file that was open for read). Does the construct provide for this?
*

No. While this functionality seems attractive, it is not clear that it's
worth the added complexity. As a practical matter these ?harmless
exceptions? rarely if ever occur, so a program will be no more robust if
these exceptions are ignored. If you feel you must ignore them, there is a
workaround, but it isn't pretty:

    static void copy(String src, String dest) throws IOException {
        boolean done = false;
        try (InputStream in = new FileInputStream(src)) {
            try(OutputStream out = new FileOutputStream(dest)) {
                byte[] buf = new byte[8192];
                int n;
                while ((n = in.read(buf)) >= 0)
                    out.write(buf, 0, n);
            }
            done = true;
        } catch(IOException e) {
            if (!done)
                throw e;
        }
    }



>
> (3) The nesting of new behavior with old behavior in the try statement
> is a poor fit for many clients. [Discussion of LineNumberReader snipped]


The revision says this:

2. Does the construct allow access to resources after an exception is thrown
from within the block, but before the resource is closed?

Not directly. The need for this functionality is rare. The workaround is to
nest a try-catch block inside the automatic resource management statement:

    try (LineNumberReader reader = getInput()) {
        try {
            parseInput(reader);
        } catch (CharacterCodingException ex) {
            report("Char encoding error at line " + reader.getLineNumber());
            throw ex;  // Rethrow the exception
        }
    }




>
> (4) The proposed construct doesn't retrofit onto many APIs in the
> profile of use-cases for which it was designed.


The revision says this:

* 4. Does the construct support resource types whose termination method has
a name other than **close**?*

Not directly. There are two obvious ways in which the construct could have
supported this functionality. One is to designate the termination method
with an annotation. But this violates the rule that annotations cannot
change the semantics of a program (JLS ?9.7). The other is to use an actual
modifier to denote the termination method (the finally keyword has been
proposed for this purpose). This would, however, require a class file format
change, and a mandate changes to tools such as JavaDoc. The resulting
construct would be more ?magical,? and wouldn't mesh as well with Java?s
type system.

The proposed construct is an ?80-20? solution. It is aimed squarely at
solving the serious problem of Closeables. Most resources can be retrofitted
to implement AutoCloseable, but a few can't (e.g., interface types that do
not already contain a parameterless close method and class types that
contain a parameterless close method with the wrong return type or
semantics). For such resources, we recommend the use of an adapter, such as
AutoLock above. The exact form of the adapter will differ depending on the
details of the resource.


      Regards,

      Josh


From neal at gafter.com  Mon Apr 20 09:39:21 2009
From: neal at gafter.com (Neal Gafter)
Date: Mon, 20 Apr 2009 09:39:21 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904200919l11b78994ueae9c9f146fe32a@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com> 
	<15e8b9d20904200846v61dad02amdff38481dc91c0a0@mail.gmail.com> 
	<17b2302a0904200919l11b78994ueae9c9f146fe32a@mail.gmail.com>
Message-ID: <15e8b9d20904200939n772b4d3fm7cfcb7ba18133511@mail.gmail.com>

On Mon, Apr 20, 2009 at 9:19 AM, Joshua Bloch <jjb at google.com> wrote:

>
>> I am disappointed to see that this revision addresses none of the
>> ergonomic issues reported earlier, not even those that were identified in
>> the previous ARM proposal years ago and for which a solution was promised in
>> the revision.
>>
>
>
> I am sorry you're disappointed. I do believe I addressed all the
> substantive issues that you raised:


By "addressed", you appear to mean the specification intentionally does
nothing about them, and the prose reinforces the point that those issues
have not been reflected in changes to the spec.  While each issue may be in
the excluded 20% of an 80-20 solution, .80*.80*.80*.80 = .41 (i.e. we have a
41% solution).


From scolebourne at joda.org  Mon Apr 20 10:24:11 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Mon, 20 Apr 2009 18:24:11 +0100
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com>
	<17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com>
Message-ID: <4b4f45e00904201024q7986a036q19a21293deba9435@mail.gmail.com>

2009/4/20 Joshua Bloch <jjb at google.com>:
>> Why not return a List<Throwable> instead of an array (since
>> Collections are generally nicer to use)?
>
> I did think about this, but I opted to stick with the pattern in enum types'
> values() method. ?That decision was made for performance. Arguably the
> performance issues are less important here, and the winds of change have
> blown further away from arrays since then, so I'm definitely open to
> switching this to a List if others think it's the right thing to do.

Definitely List. Arrays should be considered a deprecated type in all
JDK arrays at this point IMO. We need to move beyond thinking about
raw performance as a reason.

For example, I would have much preferred Enums to have had a Map of
name to enum as a generated method. I currently have to have a code
generator create this for every enum I write.

>> > The printStackTrace method should be modified to append the stack traces
>> for any suppressed exceptions.
>>
>> This might be difficult, particularly where there are a number of
>> "cause" and "suppressed" exceptions (each of which might have their
>> own) - it might be hard to associate each exception with its parent in
>> the output (whereas currently "cause" has only one immediate parent
>> and so it is easy to follow such a stack trace).
>
>
> I did think about this, and came to the conclusion that it wasn't so bad.
> ?The main problem is the "intermingling" of causes and suppressed
> exceptions. ?I will come up with a format and put an example in the spec.

The proposal should strive to include enhanced stack traces.


> >    (More generally, I think I'd prefer a single resource per ARM, as I
> >    think its a lot clearer overall and more consistent, but since you've
> >    allowed it in the proposal, I assume you'd want to keep to that
> >    style.)
> Yes.  May people really care about keeping the nesting depth low, and
> the ability to combine resources in a single ARM statement does that for them.

In my own work, I would probably choose to go with a code convention
requiring each ARM block to only have a single declaring variable.

Stephen


From Ruslan at Shevchenko.Kiev.UA  Mon Apr 20 11:23:55 2009
From: Ruslan at Shevchenko.Kiev.UA (Ruslan Shevchenko)
Date: Mon, 20 Apr 2009 21:23:55 +0300 (EEST)
Subject: Automatic Resource Management, V.2
In-Reply-To: <4b4f45e00904201024q7986a036q19a21293deba9435@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com>
	<17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com>
	<4b4f45e00904201024q7986a036q19a21293deba9435@mail.gmail.com>
Message-ID: <aa1967012b71745d761c7b039ce7b4c9.squirrel@wmail.gradsoft.ua>

> 2009/4/20 Joshua Bloch <jjb at google.com>:
>>> Why not return a List<Throwable> instead of an array (since
>>> Collections are generally nicer to use)?
>>
>> I did think about this, but I opted to stick with the pattern in enum
>> types'
>> values() method. ?That decision was made for performance. Arguably the
>> performance issues are less important here, and the winds of change have
>> blown further away from arrays since then, so I'm definitely open to
>> switching this to a List if others think it's the right thing to do.
>

 Hmm, all low-level Java API is build on arrays.

Exists (IMHO) two valuable options: or rewrite all (getStackTrace(),
reflection) use collections, or leave all (and getSupressedException()) in
arrays. Introiduce one method which return list, when all others still
arrays is wrong.

So, better now leave all in arrays, then may-be do special step to change
all arrays to collection interfaces in java low-level api, if this needed.








From forax at univ-mlv.fr  Mon Apr 20 11:33:40 2009
From: forax at univ-mlv.fr (=?ISO-8859-1?Q?R=E9mi_Forax?=)
Date: Mon, 20 Apr 2009 20:33:40 +0200
Subject: Enum.getConstants() Was: Automatic Resource Management, V.2
In-Reply-To: <4b4f45e00904201024q7986a036q19a21293deba9435@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>	<4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com>	<17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com>
	<4b4f45e00904201024q7986a036q19a21293deba9435@mail.gmail.com>
Message-ID: <49ECC004.9090502@univ-mlv.fr>

Stephen Colebourne a ?crit :
> 2009/4/20 Joshua Bloch <jjb at google.com>:
>   
>>> Why not return a List<Throwable> instead of an array (since
>>> Collections are generally nicer to use)?
>>>       
>> I did think about this, but I opted to stick with the pattern in enum types'
>> values() method.  That decision was made for performance. Arguably the
>> performance issues are less important here, and the winds of change have
>> blown further away from arrays since then, so I'm definitely open to
>> switching this to a List if others think it's the right thing to do.
>>     
>
> Definitely List. Arrays should be considered a deprecated type in all
> JDK arrays at this point IMO. We need to move beyond thinking about
> raw performance as a reason.
>
> For example, I would have much preferred Enums to have had a Map of
> name to enum as a generated method. I currently have to have a code
> generator create this for every enum I write.
>   
Hi Stephen,
Are you aware of Class.getEnumConstants() ?
I think that using this method you can write only one generic code for 
all enums.

Moreover, this map already exists in the class java.lang.Class, if you want
to expose it, you can vote for that RFE
http://bugs.sun.com/view_bug.do?bug_id=5034509

R?mi


From scolebourne at joda.org  Mon Apr 20 11:39:12 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Mon, 20 Apr 2009 19:39:12 +0100
Subject: Enum.getConstants() Was: Automatic Resource Management, V.2
In-Reply-To: <49ECC004.9090502@univ-mlv.fr>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com>
	<17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com>
	<4b4f45e00904201024q7986a036q19a21293deba9435@mail.gmail.com>
	<49ECC004.9090502@univ-mlv.fr>
Message-ID: <4b4f45e00904201139w358cf006y99f66e27aa69cd4e@mail.gmail.com>

2009/4/20 R?mi Forax <forax at univ-mlv.fr>:
> Stephen Colebourne a ?crit :
>> For example, I would have much preferred Enums to have had a Map of
>> name to enum as a generated method. I currently have to have a code
>> generator create this for every enum I write.
>>
>
> Hi Stephen,
> Are you aware of Class.getEnumConstants() ?
> I think that using this method you can write only one generic code for all
> enums.
>
> Moreover, this map already exists in the class java.lang.Class, if you want
> to expose it, you can vote for that RFE
> http://bugs.sun.com/view_bug.do?bug_id=5034509

Yes, I'm aware of that method. Like all APIs, its working out what
might be needed in advance, and I happen to think that the collections
API is much more flexible than arrays.
Stephen


From paul.martin at gmail.com  Mon Apr 20 12:59:04 2009
From: paul.martin at gmail.com (Paul Martin)
Date: Mon, 20 Apr 2009 20:59:04 +0100
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com>
	<17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com>
Message-ID: <4ce75f920904201259w13fc7ad2i8cd9007669ca9a2d@mail.gmail.com>

Hi,

>> > *5. Some failures of the **close** method can be safely ignored (e.g.,
>> ...
>> > these exceptions are ignored. If you feel you must ignore them, there is
>> > a
>> > workaround, but it isn't pretty:
>>
>> Could you use a decorator to simplify the code a little, such as:
>>
>> public class HideAutoCloseableExceptionsAdapter implements AutoCloseable {
>> ? ? ? ?private final AutoCloseable delegate;
>> ? ? ? ?public HideAutoCloseableExceptionsAdapter(AutoCloseable delegate) {
>> ? ? ? ? ? ? ? ?this.delegate = delegate;
>> ? ? ? ?}
>> ? ? ? ?@Override
>> ? ? ? ?public void close() {
>> ? ? ? ? ? ? ? ?try {
>> ? ? ? ? ? ? ? ? ? ? ? ?delegate.close();
>> ? ? ? ? ? ? ? ?} catch (Exception e) {
>> ? ? ? ? ? ? ? ? ? ? ? ?// Do nothing
>> ? ? ? ? ? ? ? ?}
>> ? ? ? ?}
>> }
>>
>> static void copy(String src, String dest) throws IOException {
>> ? ? ? InputStream in = new FileInputStream(src);
>> ? ? ? try (new HideAutoCloseableExceptionsAdapter(in)) {
>> ? ? ? ? ? try(OutputStream out = new FileOutputStream(dest)) {
>> ? ? ? ? ? ? ? byte[] buf = new byte[8192];
>> ? ? ? ? ? ? ? int n;
>> ? ? ? ? ? ? ? while ((n = in.read(buf)) >= 0)
>> ? ? ? ? ? ? ? ? ? out.write(buf, 0, n);
>> ? ? ? ? ? }
>> ? ? ? }
>> ? }
>> }
>
> Yes; you could do that. ?Of course you'd have to write a separate decorator
> for every such type. ?But it's worth mentioning that in the FAQ, and I will
> do so.

Just to clarify, I think that "HideAutoCloseableExceptionsAdapter"
should work with any AutoCloseable (as long as the decorated object is
declared before the try), so you could use that to address Neal
Gafter's point 5: "*5. Some failures of the **close** method can be
safely ignored (e.g.,closing a file that was open for read). Does the
construct provide for this?".  Simply using a standard decorator would
seem to be a reasonable solution (since ignoring close exceptions
would normally be done on a usage case-by-case basis).  Giving the
adapter a better name, such as "IgnoreCloseExceptionAdapter" might
help, or even a static factory method such as AutoCloseable
autocloseQuietly(AutoCloseable delegate).

Also, one question from: http://docs.google.com/Doc?id=ddv8ts74_1d7tz65fd

> java.util.Iterator&AutoDisposable:
> "We can learn from C# here, and avoid the same mistake that C# avoided.  The simple solution is to make the for-each loop dispose the iterator if it implements AutoDisposable, as C# does. The point, in part, is to make the proposed construct not just useful in code that already exists (criterion [2]), but useful in code yet to be written."

How can the compiler do this (determine whether an Iterable is also
AutoDisposable)?  An Iterable interface passed to the for-each loop
might not be defined as AutoDisposable, but its runtime implementation
might be.  I don't see how this can be statically determined by the
compiler, and I wouldn't think that we would want the type of each
Iterable to be checked at runtime to determine whether it also
implements AutoDisposable (in case some objects are AutoDisposable and
other objects are not).  The alternative of using the static type of
the interface to extend AutoDisposable would also seem to be fragile -
AutoDisposable objects would then sometimes not get closed by for-each
loops. ResourceSpecifications are known to be AutoDisposable for ARM,
so the problem doesn't exist there (the statically-determined
interface/class used must implement AutoDisposable).

One further comment about suppressed exceptions: I would suspect that
in many cases that the suppressed exception may indeed represent the
original error (for example out of space when writing to a file), but
the exception caused by the close represents later information (e.g.
none of the previous writes to the were actually flushed to the disk).
 Perhaps exceptions thrown by close should be structured so that
sufficient information is available in the exception itself to handle
the error, so that suppressed exceptions should not often need to be
consulted directly.

Also, I haven't seen much discussion comparing similar implementations
in other languages (but may have missed it).  From what I can see (but
I haven't actually used either), .Net ignores suppressed exceptions
and uses 'using (resource decls) { ... }' without optional catch and
finally blocks.  Python's 'with' statement seems to allow both
'__enter__' and '__exit__' methods (without a common interface), but
again without suppressed exceptions.  I can't see any advantages for
either over this ARM proposal.

Finally, have you considered a syntax such as:  using
(*ResourceDeclarations*) *statement*  ?

Then I think that you could access the variables in catch blocks
before the close method is called (though admittedly this really only
saves a single level of nesting):

using (MyResource var) try {
    ...
} catch (MyException e) {
   // caught before AutoCloseable.close();
   var.xxx();
}

as well as

try using (MyResource var) {
    ...
} catch (MyException e) {
   // caught after AutoCloseable.close();
   // so can't access var
}

Regards,

Paul


From neal at gafter.com  Mon Apr 20 13:07:42 2009
From: neal at gafter.com (Neal Gafter)
Date: Mon, 20 Apr 2009 13:07:42 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <4ce75f920904201259w13fc7ad2i8cd9007669ca9a2d@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com> 
	<4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com> 
	<17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com> 
	<4ce75f920904201259w13fc7ad2i8cd9007669ca9a2d@mail.gmail.com>
Message-ID: <15e8b9d20904201307s7049bda4i7f28fd5b94757ab8@mail.gmail.com>

On Mon, Apr 20, 2009 at 12:59 PM, Paul Martin <paul.martin at gmail.com> wrote:

> Also, one question from: http://docs.google.com/Doc?id=ddv8ts74_1d7tz65fd
>
> > java.util.Iterator&AutoDisposable:
> > "We can learn from C# here, and avoid the same mistake that C# avoided.
>  The simple solution is to make the for-each loop dispose the iterator if it
> implements AutoDisposable, as C# does. The point, in part, is to make the
> proposed construct not just useful in code that already exists (criterion
> [2]), but useful in code yet to be written."
>
> How can the compiler do this (determine whether an Iterable is also
> AutoDisposable)?  An Iterable interface passed to the for-each loop
> might not be defined as AutoDisposable, but its runtime implementation
> might be.  I don't see how this can be statically determined by the
> compiler, and I wouldn't think that we would want the type of each
> Iterable to be checked at runtime to determine whether it also
> implements AutoDisposable (in case some objects are AutoDisposable and
> other objects are not).


It's not the type of the Iterable that I suggest have special treatment, it
is the Iterator.  Since that iterator object is created by
compiler-generated code and never visible to the user program, it makes
quite a lot of sense for the generated code to arrange its disposal when
appropriate.


From jjb at google.com  Mon Apr 20 13:26:45 2009
From: jjb at google.com (Joshua Bloch)
Date: Mon, 20 Apr 2009 13:26:45 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <4ce75f920904201259w13fc7ad2i8cd9007669ca9a2d@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com>
	<17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com>
	<4ce75f920904201259w13fc7ad2i8cd9007669ca9a2d@mail.gmail.com>
Message-ID: <17b2302a0904201326x78707ebbt8cb0704c99486feb@mail.gmail.com>

Paul,

On Mon, Apr 20, 2009 at 12:59 PM, Paul Martin <paul.martin at gmail.com> wrote:

> Hi,
>
> >> > *5. Some failures of the **close** method can be safely ignored (e.g.,
> >
> > Yes; you could do that.  Of course you'd have to write a separate
> decorator
> > for every such type.  But it's worth mentioning that in the FAQ, and I
> will
> > do so.
>
> Just to clarify, I think that "HideAutoCloseableExceptionsAdapter"
> should work with any AutoCloseable (as long as the decorated object is
> declared before the try), so you could use that to address Neal
> Gafter's point 5: "*5. Some failures of the **close** method can be
> safely ignored (e.g.,closing a file that was open for read). Does the
> construct provide for this?".  Simply using a standard decorator would
> seem to be a reasonable solution (since ignoring close exceptions
> would normally be done on a usage case-by-case basis).  Giving the
> adapter a better name, such as "IgnoreCloseExceptionAdapter" might
> help, or even a static factory method such as AutoCloseable
> autocloseQuietly(AutoCloseable delegate).


Yes, you are correct.  I didn't read your example carefully.  You don't need
a separate adapter for each type if you're willing to declare the instance
outside the scope of the block.

As for the "AutoCloseableItertor" stuff, I think it can wait for a
subsequent release. I see it as scope-creep that distracts from the central
goals of the proposal and reduces the likelihood that it will be
successfully delivered into Java 7.

        Regards,

        Josh


From neal at gafter.com  Mon Apr 20 13:35:44 2009
From: neal at gafter.com (Neal Gafter)
Date: Mon, 20 Apr 2009 13:35:44 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904201326x78707ebbt8cb0704c99486feb@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com> 
	<4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com> 
	<17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com> 
	<4ce75f920904201259w13fc7ad2i8cd9007669ca9a2d@mail.gmail.com> 
	<17b2302a0904201326x78707ebbt8cb0704c99486feb@mail.gmail.com>
Message-ID: <15e8b9d20904201335p2b88665cva6feaa05eda6e12e@mail.gmail.com>

On Mon, Apr 20, 2009 at 1:26 PM, Joshua Bloch <jjb at google.com> wrote:

> As for the "AutoCloseableItertor" stuff, I think it can wait for a
> subsequent release. I see it as scope-creep that distracts from the central
> goals of the proposal and reduces the likelihood that it will be
> successfully delivered into Java 7.


If you don't design this now, you may well find it impossible to add later
without introducing a breaking change.


From jjb at google.com  Mon Apr 20 14:07:55 2009
From: jjb at google.com (Joshua Bloch)
Date: Mon, 20 Apr 2009 14:07:55 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <15e8b9d20904201335p2b88665cva6feaa05eda6e12e@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com>
	<17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com>
	<4ce75f920904201259w13fc7ad2i8cd9007669ca9a2d@mail.gmail.com>
	<17b2302a0904201326x78707ebbt8cb0704c99486feb@mail.gmail.com>
	<15e8b9d20904201335p2b88665cva6feaa05eda6e12e@mail.gmail.com>
Message-ID: <17b2302a0904201407l299398a6s88d9efcf806c6002@mail.gmail.com>

Neal,
On Mon, Apr 20, 2009 at 1:35 PM, Neal Gafter <neal at gafter.com> wrote:

> On Mon, Apr 20, 2009 at 1:26 PM, Joshua Bloch <jjb at google.com> wrote:
>
>> As for the "AutoCloseableItertor" stuff, I think it can wait for a
>> subsequent release. I see it as scope-creep that distracts from the
>> central
>> goals of the proposal and reduces the likelihood that it will be
>> successfully delivered into Java 7.
>
>
> If you don't design this now, you may well find it impossible to add later
> without introducing a breaking change.
>

That's always possible.  I'm not averse to thinking about it once the main
work is done.  I'd be especially interested in this functionality along with
some API changes to Scanner, which implements Iterator (not Iterable) and
has a close method but doesn't implement Closeable.  Right now, you can't
even use Scanner with a for-each loop, which is a shame.  If you could use
it (or some variant) with a for-each loop and the for-each loop
automatically closed the underlying character source, that would be nice; it
would eliminate a lot of boilerplate.

In C# (as you know) IEnumerator extends IDisposeable.  This is not an
unreasonable design if you're starting from a clean sheet.  We can't do
that, which means we'd need to add the notions of AutoCloseIterable, whose
iterator method returns an AutoCloseIterator, which extends both
AutoCloseable and Iterable.  The we'd have a for-each method whose behavior
differed depending on the static type of its iterable.  This is a bit scary,
in that it violates a fundamental API design guideline.  Is the result worth
this complexity?  Maybe.  I do like the idea of being able to say (roughly):

    for(String token : Scanner.fancyFactory(file)) {
       ... // Do something with the token
    }

Of course this would automatically close the underlying file, and there
would be different versions of the factory to read different types from the
file.  But we're a long way from that.

         Josh

            Josh


From neal at gafter.com  Mon Apr 20 14:32:20 2009
From: neal at gafter.com (Neal Gafter)
Date: Mon, 20 Apr 2009 14:32:20 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904201407l299398a6s88d9efcf806c6002@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com> 
	<4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com> 
	<17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com> 
	<4ce75f920904201259w13fc7ad2i8cd9007669ca9a2d@mail.gmail.com> 
	<17b2302a0904201326x78707ebbt8cb0704c99486feb@mail.gmail.com> 
	<15e8b9d20904201335p2b88665cva6feaa05eda6e12e@mail.gmail.com> 
	<17b2302a0904201407l299398a6s88d9efcf806c6002@mail.gmail.com>
Message-ID: <15e8b9d20904201432j350625e6md5c3b7c00f6c957c@mail.gmail.com>

On Mon, Apr 20, 2009 at 2:07 PM, Joshua Bloch <jjb at google.com> wrote:

> Neal,
> On Mon, Apr 20, 2009 at 1:35 PM, Neal Gafter <neal at gafter.com> wrote:
>
>> On Mon, Apr 20, 2009 at 1:26 PM, Joshua Bloch <jjb at google.com> wrote:
>>
>>> As for the "AutoCloseableItertor" stuff, I think it can wait for a
>>> subsequent release. I see it as scope-creep that distracts from the
>>> central
>>> goals of the proposal and reduces the likelihood that it will be
>>> successfully delivered into Java 7.
>>
>>
>> If you don't design this now, you may well find it impossible to add later
>> without introducing a breaking change.
>>
>
> That's always possible.  I'm not averse to thinking about it once the main
> work is done.
>

That's a reasonable approach, if you don't mind redoing the main work once
that thinking is done. The risk is that you'll have too much invested in the
design by that time to be flexible about addressing this.


> In C# (as you know) IEnumerator extends IDisposeable.
>

I don't know that because it is not true.  IEnumerator does not extend
IDisposable (
http://msdn.microsoft.com/en-us/library/system.collections.ienumerator.aspx),
though IEnumerator<T> does (
http://msdn.microsoft.com/en-us/library/78dfe2yb.aspx).  So as you can see,
that's not necessary to get the desired behavior.


> we'd need to add the notions of AutoCloseIterable, whose iterator method
> returns an AutoCloseIterator, which extends both AutoCloseable and Iterable.
> The we'd have a for-each method whose behavior differed depending on the static
> type of its iterable.  This is a bit scary, in that it violates a
> fundamental API design guideline.
>

"need" is too strong a word; that is simply one design option, and I agree
that this may be a poor starting point.  However, if a solution isn't
included when the feature is introduced, you may end up forcing this design.


From jjb at google.com  Mon Apr 20 14:48:36 2009
From: jjb at google.com (Joshua Bloch)
Date: Mon, 20 Apr 2009 14:48:36 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <15e8b9d20904201432j350625e6md5c3b7c00f6c957c@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com>
	<17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com>
	<4ce75f920904201259w13fc7ad2i8cd9007669ca9a2d@mail.gmail.com>
	<17b2302a0904201326x78707ebbt8cb0704c99486feb@mail.gmail.com>
	<15e8b9d20904201335p2b88665cva6feaa05eda6e12e@mail.gmail.com>
	<17b2302a0904201407l299398a6s88d9efcf806c6002@mail.gmail.com>
	<15e8b9d20904201432j350625e6md5c3b7c00f6c957c@mail.gmail.com>
Message-ID: <17b2302a0904201448t12299eb4p253995511f9417f0@mail.gmail.com>

Neal,
If you have a nice design, feel free to share it with the rest of us.

        Josh

On Mon, Apr 20, 2009 at 2:32 PM, Neal Gafter <neal at gafter.com> wrote:

> On Mon, Apr 20, 2009 at 2:07 PM, Joshua Bloch <jjb at google.com> wrote:
>
>> Neal,
>> On Mon, Apr 20, 2009 at 1:35 PM, Neal Gafter <neal at gafter.com> wrote:
>>
>>> On Mon, Apr 20, 2009 at 1:26 PM, Joshua Bloch <jjb at google.com> wrote:
>>>
>>>> As for the "AutoCloseableItertor" stuff, I think it can wait for a
>>>> subsequent release. I see it as scope-creep that distracts from the
>>>> central
>>>> goals of the proposal and reduces the likelihood that it will be
>>>> successfully delivered into Java 7.
>>>
>>>
>>> If you don't design this now, you may well find it impossible to add
>>> later without introducing a breaking change.
>>>
>>
>> That's always possible.  I'm not averse to thinking about it once the main
>> work is done.
>>
>
> That's a reasonable approach, if you don't mind redoing the main work once
> that thinking is done. The risk is that you'll have too much invested in the
> design by that time to be flexible about addressing this.
>
>
>> In C# (as you know) IEnumerator extends IDisposeable.
>>
>
> I don't know that because it is not true.  IEnumerator does not extend
> IDisposable (
> http://msdn.microsoft.com/en-us/library/system.collections.ienumerator.aspx),
> though IEnumerator<T> does (
> http://msdn.microsoft.com/en-us/library/78dfe2yb.aspx).  So as you can
> see, that's not necessary to get the desired behavior.
>
>
>> we'd need to add the notions of AutoCloseIterable, whose iterator method
>> returns an AutoCloseIterator, which extends both AutoCloseable and Iterable.
>> The we'd have a for-each method whose behavior differed depending on the static
>> type of its iterable.  This is a bit scary, in that it violates a
>> fundamental API design guideline.
>>
>
> "need" is too strong a word; that is simply one design option, and I agree
> that this may be a poor starting point.  However, if a solution isn't
> included when the feature is introduced, you may end up forcing this design.
>


From markmahieu at googlemail.com  Mon Apr 20 14:48:51 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Mon, 20 Apr 2009 22:48:51 +0100
Subject: Syntax patterns: more statistics.
In-Reply-To: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
Message-ID: <cf90c1f10904201448k1f120c35jc2132d0333df685e@mail.gmail.com>

Hi Ruslan,

Very nice - it'll be interesting to see the results when run against some
other libraries I used for my own analysis.  Thanks for sharing it!

Regards,

Mark


2009/4/20 Ruslan Shevchenko <Ruslan at shevchenko.kiev.ua>

> Good day, community !
>
>  I want to share some statistics about java usage patterns, related to
> some of coin-dev proposals.
>
> Main changes from previous post are:
>  - added counts for 'if' syntax constructions, so we can say, hom many
>  percents of if's can be eliminated by elvis operator ( [4-5]%)
>  - added counts for 'catch' syntax constructions, so we can say that
> multicath eliminate 6-8% of all catch clauses.
>  - added count for big integers integers (where undescore can be
> applicable, I guess this is x: x > 100000 || x < -10000) and for all
> integer literals.
>   (underscore can be applicable to near 1%)
>  - added count for object-switch proposal by Ulf Zibis (refining, that
> Left/Right part of expressions are first operand in equalirty expression
> or object in method call)
>  - added count for rethrow proposal by Mark Mahieu (near 50% of all
> catches in some packages (!) ).
>  - added count for catches inside finally block. (Is this is a real
> problem [?]).
>
> If anybody whant run checks on own dataset or/and add own check
> definitions: all  procedure is the same as in my previous letter (see
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001442.html)
> except URL for last version
>  is
>
> http://datacenter.gradsoft.ua/public.repository/ua.gradsoft/javachecker/installations/JavaCheckerSourceInstaller-2.5.0p1.jar
>
> Now summary statistics for some well-known packages:
> jetty (web server)
> all catchs      :       281
> all ifs :       764
> all integer literals    :       2903
> big integer literals(undescores)        :       25
> byte literal    :       52
> catch in finally        :       3
> elvis   :       43
> instanceof switch       :       8
> loop with remove        :       0
> multi catch     :       22
> object switch   :       31
> rethrow clause  :       34
> string in switch        :       19
> Files:187
>
> gwt-users (google java ajax client library)
> all catchs      :       171
> all ifs :       735
> all integer literals    :       2282
> big integer literals(undescores)        :       24
> byte literal    :       2
> catch in finally        :       2
> elvis   :       30
> instanceof switch       :       6
> loop with remove        :       5
> multi catch     :       9
> object switch   :       27
> rethrow clause  :       84
> string in switch        :       10
> Files:920
>
> hibernate (ORM toolkit)
> all catchs      :       650
> all ifs :       2410
> all integer literals    :       3240
> big integer literals(undescores)        :       12
> byte literal    :       1
> catch in finally        :       27
> elvis   :       182
> instanceof switch       :       28
> loop with remove        :       12
> multi catch     :       25
> object switch   :       94
> rethrow clause  :       450
> string in switch        :       86
> Files:1372
>
> openjdk7 (standard java library)
> all catchs      :       8404
> all ifs :       28494
> all integer literals    :       124356
> big integer literals(undescores)        :       4066
> byte literal    :       1454
> catch in finally        :       103
> elvis   :       877
> instanceof switch       :       318
> loop with remove        :       62
> multi catch     :       411
> object switch   :       1363
> rethrow clause  :       3264
> string in switch        :       445
> Files:9252
>
> Hope, this data will be useful in some cases.
> Regards !
>
>
>
>


From i30817 at gmail.com  Mon Apr 20 14:49:32 2009
From: i30817 at gmail.com (Paulo Levi)
Date: Mon, 20 Apr 2009 22:49:32 +0100
Subject: Non-proposal: Final Interfaces
Message-ID: <212322090904201449u4e19e48apc93722035555a317@mail.gmail.com>

*I know this is much out of date for consideration, but i think that this is
a idea that would really help library evolution, and i did not see any of
this kind of strategy floating around in the other proposals.
*

*
*

*AUTHOR(S):* Paulo Levi Martins Faria, a student at FCUL, faculdade de
ciencias da universidade de lisboa at Lisbon, Portugal.

*OVERVIEW*

A way for interfaces to be used as references outside a package, but the
only implementations of them to exist on a package, to allow the evolution
(adding) of methods to interfaces and all their implementations.

FEATURE SUMMARY:

insted of declaring interfaces as:

package xyz;

public interface A{

} or

package xyz;

interface A{

}

declare them as :

package xyz;

public final interface A{

}

And all implementations or extensions of A must be in the package xyz


MAJOR ADVANTAGE: What makes the proposal a favorable change?

This would allow library authors to control the evolution of the
implementations of a common interface, deprecating old methods, while at the
same time allowing clients to program to the interfaces. The prohibition of
implementation/extension outside of package allows the library author to
control the package evolution completly. I have personally seen cases where
performance reasons lead to dangerous downcasts or using the raw type,
and/or subclassing of various classes, to implement something more
efficiently than the library core can, because of public interfaces.

MAJOR BENEFIT:

The jdk can decide if certain interfaces are not likely to be extended
outside of the library, and thus control api evolution more completly.

All methods that are deprecated can be deleted on the interface and all
implementations (since they are controlled completly.)

MAJOR DISADVANTAGE:

Can not be retrofitted to existing api's (easily).

Somewhat overlapping with abstract classes, but more powerfull.

Losses flexibility of extension for clients, a risk i am well disposed
towards.

ALTERNATIVES: Can the benefits and advantages be had some way without a
language change?

Can think of a way how.

*EXAMPLES*

Show us the code!

SIMPLE EXAMPLE: Show the simplest possible program utilizing the new
feature.

ADVANCED EXAMPLE: Show advanced usage(s) of the feature.

*DETAILS*

SPECIFICATION: Describe how the proposal affects the grammar, type system,
and meaning of expressions and statements in the Java Programming Language
as well as any other known impacts.

COMPILATION: How would the feature be compiled to class files? Show how the
simple and advanced examples would be compiled. Compilation can be expressed
as at least one of a desugaring to existing source constructs and a
translation down to bytecode. If a new bytecode is used or the semantics of
an existing bytecode are changed, describe those changes, including how they
impact verification. Also discuss any new class file attributes that are
introduced. Note that there are many downstream tools that consume class
files and that they may to be updated to support the proposal!

I don't think that this changes compilation beyond the type checj

TESTING: How can the feature be tested?

Try to implement extend a final interface outside its package.

LIBRARY SUPPORT: Are any supporting libraries needed for the feature?

No.

REFLECTIVE APIS: Do any of the various and sundry reflection APIs need to be
updated? This list of reflective APIs includes but is not limited to core
reflection (java.lang.Class and java.lang.reflect.*), javax.lang.model.*,
the doclet API, and JPDA.

Don't think so.

OTHER CHANGES: Do any other parts of the platform need be updated too?
Possibilities include but are not limited to JNI, serialization, and output
of the javadoc tool.

No.

MIGRATION:

Create a new final sub interface to public one on the api, deplicate methods
taking that interface to use the new one. Deprecate the old methods and
interfaces. Wait for the pichforks.

*COMPATIBILITY*

BREAKING CHANGES: Are any previously valid programs now invalid? If so, list
one.

None

EXISTING PROGRAMS: How do source and class files of earlier platform
versions interact with the feature? Can any new overloadings occur? Can any
new overriding occur?

No

*REFERENCES*


From neal at gafter.com  Mon Apr 20 15:13:56 2009
From: neal at gafter.com (Neal Gafter)
Date: Mon, 20 Apr 2009 15:13:56 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904201448t12299eb4p253995511f9417f0@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com> 
	<4ce75f920904200532g14eabb81qd26cbfc3116084ee@mail.gmail.com> 
	<17b2302a0904200814m24254707l20501fc5f8854290@mail.gmail.com> 
	<4ce75f920904201259w13fc7ad2i8cd9007669ca9a2d@mail.gmail.com> 
	<17b2302a0904201326x78707ebbt8cb0704c99486feb@mail.gmail.com> 
	<15e8b9d20904201335p2b88665cva6feaa05eda6e12e@mail.gmail.com> 
	<17b2302a0904201407l299398a6s88d9efcf806c6002@mail.gmail.com> 
	<15e8b9d20904201432j350625e6md5c3b7c00f6c957c@mail.gmail.com> 
	<17b2302a0904201448t12299eb4p253995511f9417f0@mail.gmail.com>
Message-ID: <15e8b9d20904201513o5eaedb52p72ada0520eea824a@mail.gmail.com>

On Mon, Apr 20, 2009 at 2:48 PM, Joshua Bloch <jjb at google.com> wrote:

> Neal,
> If you have a nice design, feel free to share it with the rest of us.
>

I think you know I believe this problem space is best addressed by APIs
rather than (less flexible) language features.  Still, I repeat my
suggestion that you look at the C# solution as a starting point.


>
>         Josh
>
>
> On Mon, Apr 20, 2009 at 2:32 PM, Neal Gafter <neal at gafter.com> wrote:
>
>> On Mon, Apr 20, 2009 at 2:07 PM, Joshua Bloch <jjb at google.com> wrote:
>>
>>> Neal,
>>> On Mon, Apr 20, 2009 at 1:35 PM, Neal Gafter <neal at gafter.com> wrote:
>>>
>>>> On Mon, Apr 20, 2009 at 1:26 PM, Joshua Bloch <jjb at google.com> wrote:
>>>>
>>>>> As for the "AutoCloseableItertor" stuff, I think it can wait for a
>>>>> subsequent release. I see it as scope-creep that distracts from the
>>>>> central
>>>>> goals of the proposal and reduces the likelihood that it will be
>>>>> successfully delivered into Java 7.
>>>>
>>>>
>>>> If you don't design this now, you may well find it impossible to add
>>>> later without introducing a breaking change.
>>>>
>>>
>>> That's always possible.  I'm not averse to thinking about it once the
>>> main work is done.
>>>
>>
>> That's a reasonable approach, if you don't mind redoing the main work once
>> that thinking is done. The risk is that you'll have too much invested in the
>> design by that time to be flexible about addressing this.
>>
>>
>>> In C# (as you know) IEnumerator extends IDisposeable.
>>>
>>
>> I don't know that because it is not true.  IEnumerator does not extend
>> IDisposable (
>> http://msdn.microsoft.com/en-us/library/system.collections.ienumerator.aspx),
>> though IEnumerator<T> does (
>> http://msdn.microsoft.com/en-us/library/78dfe2yb.aspx).  So as you can
>> see, that's not necessary to get the desired behavior.
>>
>>
>>> we'd need to add the notions of AutoCloseIterable, whose iterator method
>>> returns an AutoCloseIterator, which extends both AutoCloseable and Iterable.
>>> The we'd have a for-each method whose behavior differed depending on the static
>>> type of its iterable.  This is a bit scary, in that it violates a
>>> fundamental API design guideline.
>>>
>>
>> "need" is too strong a word; that is simply one design option, and I agree
>> that this may be a poor starting point.  However, if a solution isn't
>> included when the feature is introduced, you may end up forcing this design.
>>
>
>


From scolebourne at joda.org  Mon Apr 20 15:24:51 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Mon, 20 Apr 2009 23:24:51 +0100
Subject: Syntax patterns: more statistics.
In-Reply-To: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
Message-ID: <4b4f45e00904201524q3d1660e8l3d02ef7b07fe29fe@mail.gmail.com>

2009/4/20 Ruslan Shevchenko <Ruslan at shevchenko.kiev.ua>:
> Main changes from previous post are:
> ?- added counts for 'if' syntax constructions, so we can say, hom many
> ?percents of if's can be eliminated by elvis operator ( [4-5]%)
> ?- added counts for 'catch' syntax constructions, so we can say that
> multicath eliminate 6-8% of all catch clauses.
> ?- added count for big integers integers (where undescore can be
> applicable, I guess this is x: x > 100000 || x < -10000) and for all
> integer literals.
> ? (underscore can be applicable to near 1%)
> ?- added count for object-switch proposal by Ulf Zibis (refining, that
> Left/Right part of expressions are first operand in equalirty expression
> or object in method call)
> ?- added count for rethrow proposal by Mark Mahieu (near 50% of all
> catches in some packages (!) ).
> ?- added count for catches inside finally block. (Is this is a real
> problem [?]).

Good work, and some interesting figures - multi-catch and elvis are
both higher than I would have guessed.

Stephen


From paul.martin at gmail.com  Mon Apr 20 15:36:21 2009
From: paul.martin at gmail.com (paul.martin at gmail.com)
Date: Mon, 20 Apr 2009 22:36:21 +0000
Subject: Automatic Resource Management, V.2
In-Reply-To: <15e8b9d20904201432j350625e6md5c3b7c00f6c957c@mail.gmail.com>
Message-ID: <0016e6d7eaacdc64af0468042821@google.com>

Hi,

On Apr 20, 2009 10:32pm, Neal Gafter <neal at gafter.com> wrote:
> On Mon, Apr 20, 2009 at 2:07 PM, Joshua Bloch jjb at google.com> wrote:
...
>> In C# (as you know) IEnumerator extends IDisposeable.
> I don't know that because it is not true. IEnumerator does not extend  
> IDisposable  
> (http://msdn.microsoft.com/en-us/library/system.collections.ienumerator.aspx),  
> though IEnumerator does  
> (http://msdn.microsoft.com/en-us/library/78dfe2yb.aspx). So as you can  
> see, that's not necessary to get the desired behavior.

MSDN's foreach documentation actually describes C#'s expansion, which does  
seem to use reflection-style type casting to determine whether an  
enumerator implements IDisposable or not.

 From http://msdn.microsoft.com/en-us/library/aa664754.aspx

(start quote)

If the collection expression is of a type that implements the collection  
pattern (as defined above), the expansion of the foreach statement is:
Copy Code

E enumerator = (collection).GetEnumerator();
try {
while (enumerator.MoveNext()) {
ElementType element = (ElementType)enumerator.Current;
statement;
}
}
finally {
IDisposable disposable = enumerator as System.IDisposable;
if (disposable != null) disposable.Dispose();
}

Significant optimizations of the above are often easily available. If the  
type E implements System.IDisposable, then the expression (enumerator as  
System.IDisposable) will always be non-null and the implementation can  
safely substitute a simple conversion for a possibly more expensive type  
test. Conversely, if the type E is sealed and does not implement  
System.IDisposable, then the expression (enumerator as System.IDisposable)  
will always evaluate to null. In this case, the implementation can safely  
optimize away the entire finally clause.

(end quote)

I expect that a similar mechanism would be possible in Java, though there  
would always be a trade-off on performance (in particular, I don't see how  
the runtime check can be avoided if an interface/non-final class is used).

Another perspective may be to consider that with try (resource) { } (and  
C#'s using), the programmer is explicitly stating that automatic resource  
management is required; the purpose of this is mainly to simplify the error  
handling code - it is not to prevent the programmer from forgetting to take  
any action to close the resource. However, automatically closing the  
Iterator in a for-each loop seems different to that - it is now the  
compiler that is making the decision that a resource (may) need to be  
closed.

This perspective could suggest that a way of explicitly indicating to the  
for-each loop that the Iterator is in fact AutoDisposable might be useful  
(even if its interface would ordinarily suggest otherwise at compile-time).  
Candidate solutions could include:
- Casting the Iterable<T> to (a subtype of) AutoDisposableIterable<T> where  
necessary (which then returns AutoDisposableIterator<T>). This would  
probably mean that close() would be defined as throwing Exception however,  
unless a cast to a subtype was used.
- try for (T : myIterable) { } (though that specific syntax is probably  
ambiguous)
- for try (T : myIterable) { } (would be ok?)

Analysis tools such as FindBugs could potentially be extended to catch many  
(though not all) errors where AutoDisposable Iterators/Iterables are being  
used incorrectly (whatever the solution).

Another alternative might be to have the try use a factory method that  
returns decorating Iterable, which when closed by the ARM block also closes  
the associated Iterator. However that is probably nastier than using a  
normal for ( ; ;) loop instead.

Regards,

Paul


From tball at google.com  Mon Apr 20 15:39:34 2009
From: tball at google.com (Tom Ball)
Date: Mon, 20 Apr 2009 15:39:34 -0700
Subject: Syntax patterns: more statistics.
In-Reply-To: <4b4f45e00904201524q3d1660e8l3d02ef7b07fe29fe@mail.gmail.com>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua> 
	<4b4f45e00904201524q3d1660e8l3d02ef7b07fe29fe@mail.gmail.com>
Message-ID: <ecf3d2390904201539h493288b8q7a1b8d4d14c2eb48@mail.gmail.com>

It is indeed good work, but like all metrics, these measurements need
to be treated as rough indicators rather than firm values.  The
Jackpot project (an automated refactoring tool) had a rule to change
if statements to conditional expressions -- it found a lot of
candidates, but most were rejected by developers using the tool.  When
asked, developers gave readability as the primary concern, stating
that it was worth some verbiage to make the code easier to read.  My
hunch is that a lot of potential elvis uses will be rejected for
similar reasons.

Tom

On Mon, Apr 20, 2009 at 3:24 PM, Stephen Colebourne
<scolebourne at joda.org> wrote:
> 2009/4/20 Ruslan Shevchenko <Ruslan at shevchenko.kiev.ua>:
>> Main changes from previous post are:
>> ?- added counts for 'if' syntax constructions, so we can say, hom many
>> ?percents of if's can be eliminated by elvis operator ( [4-5]%)
>> ?- added counts for 'catch' syntax constructions, so we can say that
>> multicath eliminate 6-8% of all catch clauses.
>> ?- added count for big integers integers (where undescore can be
>> applicable, I guess this is x: x > 100000 || x < -10000) and for all
>> integer literals.
>> ? (underscore can be applicable to near 1%)
>> ?- added count for object-switch proposal by Ulf Zibis (refining, that
>> Left/Right part of expressions are first operand in equalirty expression
>> or object in method call)
>> ?- added count for rethrow proposal by Mark Mahieu (near 50% of all
>> catches in some packages (!) ).
>> ?- added count for catches inside finally block. (Is this is a real
>> problem [?]).
>
> Good work, and some interesting figures - multi-catch and elvis are
> both higher than I would have guessed.
>
> Stephen
>
>


From i30817 at gmail.com  Mon Apr 20 15:49:21 2009
From: i30817 at gmail.com (Paulo Levi)
Date: Mon, 20 Apr 2009 23:49:21 +0100
Subject: Non-proposal: Final Interfaces
In-Reply-To: <212322090904201449u4e19e48apc93722035555a317@mail.gmail.com>
References: <212322090904201449u4e19e48apc93722035555a317@mail.gmail.com>
Message-ID: <212322090904201549h73d23c82t728ef2f4b15a45ac@mail.gmail.com>

Actually the
"All methods that are deprecated can be deleted on the interface and all
implementations (since they are controlled completly.)"

Doesn't apply since clients use the methods, but methods can be added
"(since they are controlled completly.)".

On Mon, Apr 20, 2009 at 10:49 PM, Paulo Levi <i30817 at gmail.com> wrote:

> *I know this is much out of date for consideration, but i think that this
> is a idea that would really help library evolution, and i did not see any of
> this kind of strategy floating around in the other proposals.
> *
>
> *
> *
>
> *AUTHOR(S):* Paulo Levi Martins Faria, a student at FCUL, faculdade de
> ciencias da universidade de lisboa at Lisbon, Portugal.
>
> *OVERVIEW*
>
> A way for interfaces to be used as references outside a package, but the
> only implementations of them to exist on a package, to allow the evolution
> (adding) of methods to interfaces and all their implementations.
>
> FEATURE SUMMARY:
>
> insted of declaring interfaces as:
>
> package xyz;
>
> public interface A{
>
> } or
>
> package xyz;
>
> interface A{
>
> }
>
> declare them as :
>
> package xyz;
>
> public final interface A{
>
> }
>
> And all implementations or extensions of A must be in the package xyz
>
>
> MAJOR ADVANTAGE: What makes the proposal a favorable change?
>
> This would allow library authors to control the evolution of the
> implementations of a common interface, deprecating old methods, while at the
> same time allowing clients to program to the interfaces. The prohibition of
> implementation/extension outside of package allows the library author to
> control the package evolution completly. I have personally seen cases where
> performance reasons lead to dangerous downcasts or using the raw type,
> and/or subclassing of various classes, to implement something more
> efficiently than the library core can, because of public interfaces.
>
> MAJOR BENEFIT:
>
> The jdk can decide if certain interfaces are not likely to be extended
> outside of the library, and thus control api evolution more completly.
>
> All methods that are deprecated can be deleted on the interface and all
> implementations (since they are controlled completly.)
>
> MAJOR DISADVANTAGE:
>
> Can not be retrofitted to existing api's (easily).
>
> Somewhat overlapping with abstract classes, but more powerfull.
>
> Losses flexibility of extension for clients, a risk i am well disposed
> towards.
>
> ALTERNATIVES: Can the benefits and advantages be had some way without a
> language change?
>
> Can think of a way how.
>
> *EXAMPLES*
>
> Show us the code!
>
> SIMPLE EXAMPLE: Show the simplest possible program utilizing the new
> feature.
>
> ADVANCED EXAMPLE: Show advanced usage(s) of the feature.
>
> *DETAILS*
>
> SPECIFICATION: Describe how the proposal affects the grammar, type system,
> and meaning of expressions and statements in the Java Programming Language
> as well as any other known impacts.
>
> COMPILATION: How would the feature be compiled to class files? Show how the
> simple and advanced examples would be compiled. Compilation can be expressed
> as at least one of a desugaring to existing source constructs and a
> translation down to bytecode. If a new bytecode is used or the semantics of
> an existing bytecode are changed, describe those changes, including how they
> impact verification. Also discuss any new class file attributes that are
> introduced. Note that there are many downstream tools that consume class
> files and that they may to be updated to support the proposal!
>
> I don't think that this changes compilation beyond the type checj
>
> TESTING: How can the feature be tested?
>
> Try to implement extend a final interface outside its package.
>
> LIBRARY SUPPORT: Are any supporting libraries needed for the feature?
>
> No.
>
> REFLECTIVE APIS: Do any of the various and sundry reflection APIs need to
> be updated? This list of reflective APIs includes but is not limited to core
> reflection (java.lang.Class and java.lang.reflect.*), javax.lang.model.*,
> the doclet API, and JPDA.
>
> Don't think so.
>
> OTHER CHANGES: Do any other parts of the platform need be updated too?
> Possibilities include but are not limited to JNI, serialization, and output
> of the javadoc tool.
>
> No.
>
> MIGRATION:
>
> Create a new final sub interface to public one on the api, deplicate
> methods taking that interface to use the new one. Deprecate the old methods
> and interfaces. Wait for the pichforks.
>
> *COMPATIBILITY*
>
> BREAKING CHANGES: Are any previously valid programs now invalid? If so,
> list one.
>
> None
>
> EXISTING PROGRAMS: How do source and class files of earlier platform
> versions interact with the feature? Can any new overloadings occur? Can any
> new overriding occur?
>
> No
>
> *REFERENCES*
>
>


From vapor1 at teleport.com  Mon Apr 20 17:21:00 2009
From: vapor1 at teleport.com (Derek Foster)
Date: Mon, 20 Apr 2009 20:21:00 -0400 (EDT)
Subject: Automatic Resource Management, V.2 (wrt. 'finally')
Message-ID: <11173751.1240273260729.JavaMail.root@elwamui-muscovy.atl.sa.earthlink.net>



-----Original Message-----
>From: Joshua Bloch <jjb at google.com>
>Sent: Apr 20, 2009 9:19 AM
>To: coin-dev <coin-dev at openjdk.java.net>
>Subject: Re: Automatic Resource Management, V.2
>
>Neal,
>
>I do believe I addressed all the substantive issues that you raised:
>
>>(1) "try" is not a natural keyword for the intended semantics.
>
>> (3) The nesting of new behavior with old behavior in the try statement
>> is a poor fit for many clients. [Discussion of LineNumberReader snipped]
>
>You didn't really back this one up.  Other people have commented on what a
>great fit they think it is.  So we'll just have to consider it an issue of
>taste, on which reasonable men may disagree.

Hi, Josh.

As much as I agree with the general goals of the ARM proposal, I'd like to point out that Neal isn't the only one to hold this opinion. I had the same reaction as Neal did when I saw that "try" was being used for this purpose. The 'try..catch..finally' construct is already one of the more complicated constructs in Java. I hate to see it complicated further by adding new functionality to it that really has nothing to do with its primary purpose (that of attempting an operation and then providing places for someone to handle exceptions from it). Also, I hate to see a mechanism that is basically type-agnostic be expanded with something that is so specific to file-based I/O.

Your recent ARM proposal description, for instance, was complicated by the question of what to do with any other 'catch' or 'finally' clauses which might be present on the 'try'. The proposal was also somewhat unclear on whether or not a 'try' without any 'catches' or 'finally' clauses now becomes legal Java even if there are no initializers present. If another keyword had been chosen, these would not even have been issues that the proposal needed to address.

I rather liked the suggestion that various people put forth a while ago for using the 'protected' keyword instead. Since it seems that it is not going to be used for a lock-related proposal anymore, why not use it for this?

protected (FileReader in = new FileReader(whatever)) {
    doStuff(in.read());
}

This would provide a nice, orthogonal feature that would be unrelated to the 'try' keyword, thus making for two smaller simpler features (protected and try) rather than one big complicated one (protected+try, as in the current proposal). Its syntax would also then be more analogous to the 'synchronized' keyword, which this feature is (IMHO) MUCH more semantically similar to than it is to 'try'.

Like 'synchronized' (at least as far as closing/unlocking of resources go), ARM is a higher-level interface to a subset of functionality that is usually performed using try..finally. I don't think that the fact that closing of resources is usually IMPLEMENTED using 'try' is a good reason to make its INTERFACE syntactically similar to a try..catch..finally block, which has very different semantics.

>The revision says this:
>
>* 4. Does the construct support resource types whose termination method has
>a name other than **close**?*
>
>Not directly. There are two obvious ways in which the construct could have
>supported this functionality. One is to designate the termination method
>with an annotation. But this violates the rule that annotations cannot
>change the semantics of a program (JLS ?9.7). The other is to use an actual
>modifier to denote the termination method (the finally keyword has been
>proposed for this purpose). This would, however, require a class file format
>change, and a mandate changes to tools such as JavaDoc. The resulting
>construct would be more ?magical,? and wouldn't mesh as well with Java?s
>type system.

This is my number one gripe with the current proposal: It's not extensible due to its dependence on the AutoCloseable interface and the need for a method named "close()". It's too specific to files. If I want to use it for locks, for disposeable objects, or for other similar kinds of resources, I have to jump through weird hoops and use adapter classes and so forth, or settle for my 'unlock' method being called 'close' just to fit the interface. Not Good. This is true even if I am coding up my own lock objects (with a 'lock()' method that returns 'this') rather than using those provided by java.util.concurrent.

There is a better solution to this problem, which avoids the technical issues that have been raised above against annotations and the 'finally' keyword. It is possible to combine these approaches to get the desired behavior (a type-system-independent way to designate a closing method) without forcing a change to the class file format.

In fact there is already an existing precedent for doing this: Enums.

When the compiler compiles an 'enum' declaration, it generates a hidden annotation on the generated class, which identifies it as an enumerated type. This has implications for the compiler (such as the fact that another class can't extend such a type). Thus, the "annotations don't change program semantics" rule is being slightly bent in this case, but its spirit is preserved, since the annotation can't be used or even seen by ordinary users -- just by the compiler, and by JDK methods like "Class.isEnum".

In the ARM proposal, we could do the same thing with the 'finally' keyword. If the compiler notices that the 'finally' keyword is present on a method, it can supply a hidden annotation on that method which qualifies it within the class file, so that this:

public finally void dispose(); // or unlock(), or...

desugars to this:

@AutoClose public void dispose();

with the @AutoClose annotation being invisible to normal users of Java, in the same way as the annotation used to declare enum types currently is.

Some further restrictions would be needed:
1) It is a compile-time error if the 'finally' keyword appears on more than one method within a type declaration.
2) It is a compile-time error if a type extends multiple supertypes with 'finally' methods which have incompatible signatures, but does not designate one of its own methods with the "finally" keyword. (This guarantees uniqueness of finally methods).

With these rules in place, when attempting to compile an instance of the ARM construct, the compiler can then search up the inheritance tree for the first instance of a method with the @AutoClose annotation, and use that method it if it's present (or else provoke a compiler error: "this type has no finally method").

As far as I can see, the above approach is much less limiting than designating a magic interface (or pre-specified set of interfaces) such as AutoCloseable. It will make it much easier for existing classes and interfaces to be retrofitted to support ARM, since it won't affect their inheritance hierarchies.

Note that it is still possible to define a class like AutoCloseable in this scenario, should someone still want to do so:

interface AutoCloseable {
    finally void close() throws Exception;
}

Derek



From vapor1 at teleport.com  Mon Apr 20 21:37:52 2009
From: vapor1 at teleport.com (Derek Foster)
Date: Tue, 21 Apr 2009 00:37:52 -0400 (EDT)
Subject: PROTOTYPE:
Message-ID: <24411601.1240288672402.JavaMail.root@elwamui-muscovy.atl.sa.earthlink.net>

Hi, Bruce!

I just wanted to offer a huge "THANK YOU!!!" for following up on this and doing actual implementation work. I have had a product release at work, as well as some challenges in my personal life, that have pretty much occupied all of my free time and have made it all but impossible over the last few weeks for me to do any more with Project Coin than to try to read the emails as they come in. Doing compiler implementation work was pretty much out of the question. It has been tremendously helpful that you have been continuing to work on these proposals in my absence. (I am now trying to work through the backlog of Coin-related emails that I wanted to answer but did not have time to, and I will try to update my proposals with the results of various list conversations regarding them ASAP.)

Anyway, in reply to your earlier question about whether or not it was necessary to support underscores at the beginning or end of sequences of digits... I don't have a firm opinion on this. My proposal was written to allow it because I saw no particular reason to disallow it, but I must admit I can't think of any particularly compelling use cases for this behavior. I am considering rewriting my proposal to disallow it and instead go with your suggestion that underscores only be allowed within sequences of digits, instead of around them as well. (However, as I mentioned, I am somewhat short on time, although not as short as I was recently.)

Do others have opinions as to whether this feature (the ability to put underscores at the beginning or end of sequences of digits within a number, such as "0x_5", "0x5_" or "52_") is either desirable or problematic? It seems that Bruce is feeling that it's unnecessary and possibly confusing, and I am now finding myself leaning somewhat towards that opinion myself, although if someone were to present a good example of a case where it might be useful, I might change my mind.

Derek



-----Original Message-----
>From: Bruce Chapman <brucechapman at paradise.net.nz>
>Sent: Apr 20, 2009 6:37 AM
>To: coin-dev at openjdk.java.net
>Cc: Derek Foster <vapor1 at teleport.com>
>Subject: PROTOTYPE:
>
>A prototype compiler for the follow proposals
>
>Underscores in numbers
>Narrow Hexadecimal and Binary Integer Literals
>Byte and Short Integer Literal Suffixes
>
>is now available at
>https://kijaro.dev.java.net/servlets/ProjectDocumentList?folderID=11247&expandFolder=11247&folderID=8804
>
>I have bundled them altogether so that the interaction between 
>underscores and the others can be assessed and so that the two new 
>literal forms can be compared side by side.
>
>There is one fault in the test class, fix that and it should compile and 
>run.
>
>-- Joe, should we update the proposals with this information or is this 
>email sufficient?
>
>
>Bruce



From Ruslan at Shevchenko.Kiev.UA  Mon Apr 20 23:59:30 2009
From: Ruslan at Shevchenko.Kiev.UA (Ruslan Shevchenko)
Date: Tue, 21 Apr 2009 09:59:30 +0300 (EEST)
Subject: Syntax patterns: more statistics.
In-Reply-To: <cf90c1f10904201448k1f120c35jc2132d0333df685e@mail.gmail.com>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<cf90c1f10904201448k1f120c35jc2132d0333df685e@mail.gmail.com>
Message-ID: <c1c7da7f2d62e301534fab57ff542da5.squirrel@wmail.gradsoft.ua>

> Hi Ruslan,
>
> Very nice - it'll be interesting to see the results when run against some
> other libraries I used for my own analysis.  Thanks for sharing it!
>

Thanks. Results (about rethrow) was very surprising for me.

 Trying to analyze: I just see, that all this is 'system libraries'
which provide some layer, i. e.  may be have sence add some application
code  (open-source ERP, for example) to dataset.






From Ruslan at Shevchenko.Kiev.UA  Tue Apr 21 00:08:41 2009
From: Ruslan at Shevchenko.Kiev.UA (Ruslan Shevchenko)
Date: Tue, 21 Apr 2009 10:08:41 +0300 (EEST)
Subject: Syntax patterns: more statistics.
In-Reply-To: <4b4f45e00904201524q3d1660e8l3d02ef7b07fe29fe@mail.gmail.com>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904201524q3d1660e8l3d02ef7b07fe29fe@mail.gmail.com>
Message-ID: <e56de653021d9485ab8bad74e37f456f.squirrel@wmail.gradsoft.ua>


>
> Good work, and some interesting figures - multi-catch and elvis are
> both higher than I would have guessed.
>
Thanks. I also surprised by number of catches, which do only rethrow

 Trying to figure details, this is percents by packages:

	               Jetty    Gwt-user	hibernate	openjdk
elvis/ifs*100           5.63    4.08	         7.55            3.08
multicatch/cath*100     7.83    5.26             3.85            4.89
rethrow/cath*100        12.1    49.12            69.23           38.84

 Also (as I wrote in previous code) all libraries  (which I random get
from hard drive) are system libraries, so exists sense look at
application code.

Also some organizations does not like null-s in API (I read, that google
have such policy, but facts about gwt-user contradict this)


> Stephen
>
>




From Ruslan at Shevchenko.Kiev.UA  Tue Apr 21 00:15:09 2009
From: Ruslan at Shevchenko.Kiev.UA (Ruslan Shevchenko)
Date: Tue, 21 Apr 2009 10:15:09 +0300 (EEST)
Subject: Syntax patterns: more statistics.
In-Reply-To: <ecf3d2390904201539h493288b8q7a1b8d4d14c2eb48@mail.gmail.com>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904201524q3d1660e8l3d02ef7b07fe29fe@mail.gmail.com>
	<ecf3d2390904201539h493288b8q7a1b8d4d14c2eb48@mail.gmail.com>
Message-ID: <0d48edf00d3533cd9adab8ce7edc7fa6.squirrel@wmail.gradsoft.ua>

> It is indeed good work, but like all metrics, these measurements need
> to be treated as rough indicators rather than firm values.  The

 Yes.

> Jackpot project (an automated refactoring tool) had a rule to change
> if statements to conditional expressions -- it found a lot of
> candidates, but most were rejected by developers using the tool.  When
> asked, developers gave readability as the primary concern, stating
> that it was worth some verbiage to make the code easier to read.  My
> hunch is that a lot of potential elvis uses will be rejected for
> similar reasons.
>

Yes.
 How we can count this: look at languages where elvis implemented and
find percentage of applicability. What we need for this (?) - just parser.
So, in priniciple if exists publicy aviable groovy or C# parser (or
compiler/interpreter which provide access to AST), we can try hack one, to
count unused possibilities and expect that in java number would be near.


> Tom
>
> On Mon, Apr 20, 2009 at 3:24 PM, Stephen Colebourne
> <scolebourne at joda.org> wrote:
>> 2009/4/20 Ruslan Shevchenko <Ruslan at shevchenko.kiev.ua>:
>>> Main changes from previous post are:
>>> ?- added counts for 'if' syntax constructions, so we can say, hom many
>>> ?percents of if's can be eliminated by elvis operator ( [4-5]%)
>>> ?- added counts for 'catch' syntax constructions, so we can say that
>>> multicath eliminate 6-8% of all catch clauses.
>>> ?- added count for big integers integers (where undescore can be
>>> applicable, I guess this is x: x > 100000 || x < -10000) and for all
>>> integer literals.
>>> ? (underscore can be applicable to near 1%)
>>> ?- added count for object-switch proposal by Ulf Zibis (refining, that
>>> Left/Right part of expressions are first operand in equalirty
>>> expression
>>> or object in method call)
>>> ?- added count for rethrow proposal by Mark Mahieu (near 50% of all
>>> catches in some packages (!) ).
>>> ?- added count for catches inside finally block. (Is this is a real
>>> problem [?]).
>>
>> Good work, and some interesting figures - multi-catch and elvis are
>> both higher than I would have guessed.
>>
>> Stephen
>>
>>
>
>




From scolebourne at joda.org  Tue Apr 21 00:53:13 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Tue, 21 Apr 2009 08:53:13 +0100
Subject: PROTOTYPE:
In-Reply-To: <24411601.1240288672402.JavaMail.root@elwamui-muscovy.atl.sa.earthlink.net>
References: <24411601.1240288672402.JavaMail.root@elwamui-muscovy.atl.sa.earthlink.net>
Message-ID: <49ED7B69.7030704@joda.org>

Derek Foster wrote:
> Do others have opinions as to whether this feature (the ability to put underscores at the beginning or end of sequences of digits within a number, such as "0x_5", "0x5_" or "52_") is either desirable or problematic? It seems that Bruce is feeling that it's unnecessary and possibly confusing, and I am now finding myself leaning somewhat towards that opinion myself, although if someone were to present a good example of a case where it might be useful, I might change my mind.

I would have expected no underscores at start or end, and no adjacent 
underscores. That seems like the main case.

Stephen


From markmahieu at googlemail.com  Tue Apr 21 01:04:14 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Tue, 21 Apr 2009 09:04:14 +0100
Subject: Syntax patterns: more statistics.
In-Reply-To: <0d48edf00d3533cd9adab8ce7edc7fa6.squirrel@wmail.gradsoft.ua>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904201524q3d1660e8l3d02ef7b07fe29fe@mail.gmail.com>
	<ecf3d2390904201539h493288b8q7a1b8d4d14c2eb48@mail.gmail.com>
	<0d48edf00d3533cd9adab8ce7edc7fa6.squirrel@wmail.gradsoft.ua>
Message-ID: <cf90c1f10904210104i6eb347c1k9f4de9b496b852e5@mail.gmail.com>

That's a good idea, although again we'd need to be very careful about
interpreting the results.  For example, if we look at uses of both ?: and ?.
in Groovy code, we should note that the Elvis operator is a relatively
recent addition to the language, whereas the safe-navigation operator has
been supported for much longer.  In addition, much of the Groovy code I've
seen uses the safe-navigation operator in ways that are not supported by the
coin proposal.
Mark


2009/4/21 Ruslan Shevchenko <Ruslan at shevchenko.kiev.ua>

> > It is indeed good work, but like all metrics, these measurements need
> > to be treated as rough indicators rather than firm values.  The
>
>  Yes.
>
> > Jackpot project (an automated refactoring tool) had a rule to change
> > if statements to conditional expressions -- it found a lot of
> > candidates, but most were rejected by developers using the tool.  When
> > asked, developers gave readability as the primary concern, stating
> > that it was worth some verbiage to make the code easier to read.  My
> > hunch is that a lot of potential elvis uses will be rejected for
> > similar reasons.
> >
>
> Yes.
>  How we can count this: look at languages where elvis implemented and
> find percentage of applicability. What we need for this (?) - just parser.
> So, in priniciple if exists publicy aviable groovy or C# parser (or
> compiler/interpreter which provide access to AST), we can try hack one, to
> count unused possibilities and expect that in java number would be near.
>
>
> > Tom
>


From brucechapman at paradise.net.nz  Tue Apr 21 01:58:41 2009
From: brucechapman at paradise.net.nz (Bruce Chapman)
Date: Tue, 21 Apr 2009 20:58:41 +1200
Subject: PROTOTYPE:
In-Reply-To: <24411601.1240288672402.JavaMail.root@elwamui-muscovy.atl.sa.earthlink.net>
References: <24411601.1240288672402.JavaMail.root@elwamui-muscovy.atl.sa.earthlink.net>
Message-ID: <49ED8AC1.6080209@paradise.net.nz>

Derek Foster wrote:
> Hi, Bruce!
>
> I just wanted to offer a huge "THANK YOU!!!" for following up on this and doing actual implementation work.
Yeah, but you saved me from having to write the proposal, and to be 
honest ( 
https://kijaro.dev.java.net/servlets/ReadMsg?list=commits&msgNo=172 ), I 
think I got the easier half of the job, and half of that was just 
copying and pasting your tests from the spec. So thank YOU.


Bruce




From neal at gafter.com  Tue Apr 21 08:00:10 2009
From: neal at gafter.com (Neal Gafter)
Date: Tue, 21 Apr 2009 08:00:10 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
Message-ID: <15e8b9d20904210800v762e39a4t5ba75d660780e2@mail.gmail.com>

On Sun, Apr 19, 2009 at 11:45 PM, Joshua Bloch <jjb at google.com> wrote:

> The variable #localVar is a compiler-generated identifier distinct from any
> other identifiers (compiler-generated or otherwise) that are in scope (JLS
> ?6.3) at the point where the automatic resource management statement
> occurs.
> The *Type *in the above desugaring is replaced by the static type of *
> Expression*.
>

This introduces the possibility of local variables with intersection and
recursive types.  Such variables could not have occurred previously because
they are not denotable.  I believe there are three tables in the class file
format that may be affected.  Can you please include in the specification a
description of how you want them handled?


From jjb at google.com  Tue Apr 21 08:34:40 2009
From: jjb at google.com (Joshua Bloch)
Date: Tue, 21 Apr 2009 08:34:40 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <15e8b9d20904210800v762e39a4t5ba75d660780e2@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<15e8b9d20904210800v762e39a4t5ba75d660780e2@mail.gmail.com>
Message-ID: <17b2302a0904210834l55f665d9w52613c792989abb0@mail.gmail.com>

Neal,
Yes, this is the situation that Bruce Chapman pointed out earlier.  As a
practical matter, I suspect that resources will have rather simple types,
but still the spec does have to cover this situation.  If you have a good
solution, feel free to share.  Otherwise, hang on, and we'll see what we can
come up with.

             Josh

On Tue, Apr 21, 2009 at 8:00 AM, Neal Gafter <neal at gafter.com> wrote:

> On Sun, Apr 19, 2009 at 11:45 PM, Joshua Bloch <jjb at google.com> wrote:
>
>> The variable #localVar is a compiler-generated identifier distinct from
>> any
>> other identifiers (compiler-generated or otherwise) that are in scope (JLS
>> ?6.3) at the point where the automatic resource management statement
>> occurs.
>> The *Type *in the above desugaring is replaced by the static type of *
>> Expression*.
>>
>
> This introduces the possibility of local variables with intersection and
> recursive types.  Such variables could not have occurred previously because
> they are not denotable.  I believe there are three tables in the class file
> format that may be affected.  Can you please include in the specification a
> description of how you want them handled?
>


From Joe.Darcy at Sun.COM  Tue Apr 21 08:35:16 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Tue, 21 Apr 2009 08:35:16 -0700
Subject: PROPOSAL: Enhanced for each loop iteration control
In-Reply-To: <49C56020.2070207@joda.org>
References: <49C56020.2070207@joda.org>
Message-ID: <49EDE7B4.2090006@sun.com>

Catching up on proposal commenting, while I find the design generally 
acceptable, I remain unconvinced that the inability to replace all 
pre-JDK 5 for loops with some newer, improved for loop is a serious 
enough problem to justify further language changes beyond the enhanced 
for loop in JDK 5.

Some data on how often such a new construct would be applicable would 
help here.

-Joe

Stephen Colebourne wrote:
> Enhanced for each loop iteration control
>
> (re-sent with correct subject line)
>
> This proposal extends the for each loop to allow access to meta data
> including the index and the remove method.
>
> (This proposal doesn't really go into enough detail - with JSR-310 my
> time here is limited. I'd hope that there is just about enough though....)
>
> -----------------------------------------------------------------------------------
> Enhanced for each loop iteration control
>
> AUTHOR(S):
> Stephen Colebourne
>
> *OVERVIEW*
>
> FEATURE SUMMARY:
> Extends the Java 5 for-each loop to allow access to the loop index,
> whether this is the first or last iteration, and to remove the current item.
>
> MAJOR ADVANTAGE:
> The for-each loop is almost certainly the most new popular feature from
> Java 5. It works because it increases the abstraction level - instead of
> having to express the low-level details of how to loop around a list or
> array (with an index or iterator), the developer simply states that they
> want to loop and the language takes care of the rest. However, all the
> benefit is lost as soon as the developer needs to access the index or to
> remove an item.
>
> The original Java 5 for each work took a relatively conservative stance
> on a number of issues aiming to tackle the 80% case. However, loops are
> such a common form in coding that the remaining 20% that was not tackled
> represents a significant body of code.
>
> The process of converting the loop back from the for each to be index or
> iterator based is painful. This is because the old loop style if
> significantly lower-level, more verbose and less clear. It is also
> painful as most IDEs don't support this kind of 'de-refactoring'.
>
> MAJOR BENEFIT:
> A common coding idiom is expressed at a higher abstraction than at
> present. This aids readability and clarity.
>
> Accessing the index currently requires using an int based loop, or
> placing a separate int counter outside the loop (which then remains in
> scope after the loop). The proposed solution doesn't result in manual
> manipulation of the index.
>
> Accessing the iterator remove requires using an iterator based loop.
> With generics this is remarkably verbose. The proposed solution is
> significantly shorter and cleaner.
>
> MAJOR DISADVANTAGE:
> The enhanced for each loop is complicated with additional functionality.
> (This is mitigated by being easy and obvious to use)
>
> More code is generated magically by the compiler. (This is mitigated by
> a simple desugaring)
>
> ALTERNATIVES:
> Use the existing language constructs, typically the standard for loop.
>
> Use BGGA/JCA style closures, with control statements. It should be noted
> that these are consistently the most controversial parts of the closure
> debate, making the 'let's wait for closures' argument against this
> proposal weaker (as any final closures implementation may not include
> control statements).
>
>
> *EXAMPLES*
>
> SIMPLE EXAMPLE:
>
>     StringBuilder buf = new StringBuilder();
>     for (String str : list : it) {
>       if (str == null) {
>         it.remove();
>       }
>     }
>
> whereas, today we write:
>
>     StringBuilder buf = new StringBuilder();
>     for (Iterator<String> it = list.iterator(); it.hasNext();) {
>       String str = it.next();
>       if (str == null) {
>         it.remove();
>       }
>     }
>
> ADVANCED EXAMPLE:
>
> Example1:
>
>     for (String str : list : it) {
>       System.out.println("Row " + it.index() + " has the value " + str);
>     }
>
> whereas, today we might write:
>
>     int index = 0;
>     for (String str : list) {
>       System.out.println("Row " + index + " has the value " + str);
>       index++;
>     }
>
> or
>
>     for (int i = 0; i < list.size(); i++) {
>       String str = list.get(i);
>       System.out.println("Row " + index + " has the value " + str);
>     }
>
> Example 2:
>
>     StringBuilder buf = new StringBuilder();
>     for (String str : list : it) {
>       if (it.isFirst()) {
>         buf.append(str);
>       } else {
>         buf.append(", ").append(str);
>       }
>     }
>
>     StringBuilder buf = new StringBuilder();
>     for (String str : list : it) {
>       if (it.isLast()) {
>         buf.append(str);
>       } else {
>         buf.append(str).append(", ");
>       }
>     }
>
>
> *DETAILS*
>
> SPECIFICATION:
>
> Lexical:
> No new tokens are added. The colon token is reused in the extended
> enhanced for each statement.
>
> Syntax:
>
>    EnhancedForStatement:
>      for ( VariableModifiersopt Type Identifier : Expression) Statement
>      for ( VariableModifiersopt Type Identifier : Expression : Ident)
> Statement
>
> Semantics:
>
> The first enhanced for each statement (the current form) will compile as
> it does today.
>
> The extended enhanced for each statement will operate as follows.
> The iterator control variable is a standard variable declared to be
> final. It will never be null. The type is dependent on whether the
> expression is an array or an Iterable. It will either be
> ArrayIterationControl<T> or IterableIterationControl<T>. The type is not
> specified as it is redundent information, ie. the type is inferred. It
> is scoped for the life of the loop.
>
> public final class IterableIterationControlIterator<T> {
>     public IterableIterationControlIterator(Iterable<T> iterable) {
>       this.control = new IterableIterationControl(iterable.iterator());
>     }
>     public boolean hasNext() { return control.hasNext() }
>     public T next() { return control.next() }
>     public IterableIterationControl<T> control() { return control }
> }
> public final class IterableIterationControl<T> {
>     public IterableIterationControl(Iterator<T> iteratorToWrap) {
>       this.it = iteratorToWrap;
>     }
>     boolean hasNext() { return it.hasNext() }
>     T next() { originalIndex++; if (lastWasRemoved) { lastWasRemoved =
> false } else { index++ } return it.next() }
>     public T remove() { removed++; lastWasRemoved = true; return
> it.remove() }
>     public int index() { return index }
>     public int originalIndex() { return originalIndex }
>     public boolean isFirst() { return index == 1 }
>     public boolean isLast() { return it.hasNext() == false }
> }
>
> public final class ArrayIterationControlIterator<T> {
>     public ArrayIterationControlIterator(T[] array) {
>       this.control = new ArrayIterationControl(array);
>     }
>     public boolean hasNext() { return control.hasNext() }
>     public T next() { return control.next() }
>     public ArrayIterationControl<T> control() { return control }
> }
> public final class ArrayIterationControl<T> {
>     public ArrayIterationControl(T[] array) { this.array = array; }
>     boolean hasNext() { return index < array.length; }
>     T next() { return array[++index]; }
>     public int index() { return index - 1; }
>     public boolean isFirst() { return index == 1; }
>     public boolean isLast() { return index == array.length; }
> }
>
> Exception analysis:
> The method remove() on the iteration control variable can throw an
> UnsuportedOperationException. However, this is no different from any
> other method call.
>
> Definite assignment:
> The new variable iteration control variable is a final variable that is
> definitely assigned from creation.
>
> COMPILATION:
> The extended enhanced for each loop is implemented by wrapping the two
> control classes around the Iterable or the array.
>
> The Iterable design is desugared from:
>
>     for (T item : iterable : control) { ... }
>
> to:
>     {
>       IterableIterationControlIterator<T> $it = new
> IterableIterationControlIterator(iterable);
>       IterableIterationControl<T> control = $it.control();
>       while ($it.hasNext()) {
>         T item = $it.next();
>         ...
>       }
>     }
>
> The array design is desugared similarly:
>
>     {
>       ArrayIterationControlIterator<T> $it = new
> ArrayIterationControlIterator(iterable);
>       ArrayIterationControl<T> control = $it.control();
>       while ($it.hasNext()) {
>         T item = $it.next();
>         ...
>       }
>     }
>
> There is the option to optimise this if the iteration control variable
> is not assigned to any other variable or passed to any other method.
> However, that is out of scope for now.
>
> TESTING:
> Testing will be similar to the enhanced for loop. Arrays and Iterables
> of various types and sizes will be used. The null expression will also
> be tested.
>
> LIBRARY SUPPORT:
> Yes, as detailed above.
>
> REFLECTIVE APIS:
> No.
>
> OTHER CHANGES:
> The javac tree API would need to be updated to model the change.
>
> MIGRATION:
> Migration is not required. However, an IDE refactoring could now convert
> more int and Iterator based for loops than it does at present.
>
>
> *COMPATIBILITY*
>
> BREAKING CHANGES:
> No breaking changes are known using this conversion scheme.
>
> EXISTING PROGRAMS:
> This conversion is pure syntax sugar, so there are no known interactions
> with existing programs.
>
>
> *REFERENCES*
>
> EXISTING BUGS:
> I searched the bug database, but nothing came up (which is surprising).
>
> URL FOR PROTOTYPE:
> None
>
> DOCUMENTS:
> [1] Stephen Colebourne's blog:
> http://www.jroller.com/scolebourne/entry/java_7_for_each_loop
> [2] Stephen Colebourne's original writeup:
> http://docs.google.com/Edit?docID=dfn5297z_15ck7x5ghr
>
>
> *DESIGN ISSUES*
> There are numerous alternative ways in which this feature can be added.
> These include:
> - using the keyword:
>     for (String str : list) {
>       for.remove();  // problem is nested for loops
>     }
> - using a label as a psuedo-variable:
>     it: for (String str : list) {
>       it:remove();  // note colon and not dot
>     }
> - using an additional clause before the for each colon:
>     for (String str, int index : list) {
>       // no access to remove, and conflicts for for each for maps
>     }
>
> The chosen solution involves simple Java classes, and a simple desugar.
> The downside of the chosen solution is performance, as it involves
> creating two wrapping objects and routing hasNext() and next() via
> additional layers of method calls. A possible extension would be for the
> compiler to identify if the iteration control variable is not passed to
> another method. If so, then the code could be all be generated inline.
>
>
>
>
>
>   



From Joe.Darcy at Sun.COM  Tue Apr 21 08:36:07 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Tue, 21 Apr 2009 08:36:07 -0700
Subject: PROPOSAL: Named method parameters
In-Reply-To: <4ce75f920903210915pa2b27b3g38841e342a78de77@mail.gmail.com>
References: <4ce75f920903210915pa2b27b3g38841e342a78de77@mail.gmail.com>
Message-ID: <49EDE7E7.7040907@sun.com>

Catching up on responses, as has been further discussed on the list 
recently, requests in this general vein have been considered before in 
JDK 6.  While there are certainly use-cases this facility could clarify, 
I remain unconvinced of the cost/benefit ratio of this proposal.

A few design notes, a single @PublicParameterNames annotation with a 
boolean member could be used instead of a pair of "do it/don't do it" 
annotations.

A full proposal for this facility would need to deal with the cases 
where the number of parameters in the class file differs from the number 
of parameters in the source code, a situation already mildly exposed 
when calling toGenericString on some Method and Constructor objects.

Not supporting parameter reordering greatly simplifies the proposal by 
leaving method selection largely unaffected, but also seems to limit the 
usefulness of the proposal.  If the main benefit is just seeing the 
parameter name in the program text; can't the IDE do that?

I'd isn't clear to me how @PublicParameterNames would interact with 
overridden methods in class hierarchies.  Presumably the names of the 
static type of the call site would need be match, even though the 
runtime type could differ.  If a subclass overrode a method and changed 
its parameter names (which currently has no affect on compatibility), 
the subclass would no longer be substitutable for the parent class, 
which would break a fundamental design principle.

At least there is no binary compatibility impact since the names would 
only be checked at compile time and binary compatibility is about 
preserving the ability to link.

-Joe

Paul Martin wrote:
> I'd like to propose the implementation of optionally named method
> parameters, and suggest that they are particularly useful when creating
> immutable objects (which are important in our increasingly concurrent
> world).
>
> Note that this is a topic that seems to have been considered before (see the
> note in http://paulhammant.com/blog/announcing_paranamer.html which suggests
> that it was even considered for Java 6), but I can't see it in the current
> list of Java 7 changes or in the Project Coin mailing list archives (though
> others have also discussed it in relation to Java 7, such as Alex Miller in
> http://tech.puredanger.com/2007/08/15/dr-java7/ and
> http://tech.puredanger.com/2007/10/11/java7-roundup-32/).  Therefore I am
> proposing it here - I think that it is an important change (unless anyone
> can suggest how I can reasonably create an immutable object with four or
> more properties without using a Builder or a list of unnamed parameters).
>
> Also note that other relevant references include:
> http://blogs.sun.com/abuckley/entry/named_parameters (which discusses why
> parameter reordering might be difficult),
> http://beust.com/weblog/archives/000096.html (which suggests that we do not
> need named parameters, but really just shows the use of the Builder pattern
> which has limitations).
>
>
> Named method parameters
>
> AUTHOR(S):
>
> Paul Martin
>
> OVERVIEW
>
> FEATURE SUMMARY:
>
> Named parameters allow a method or constructor caller to explicitly state
> the parameter name of each parameter value passed to the method or
> constructor.  Without named parameters, only the order of the parameter
> values is significant (and it may not be clear what each value represents).
>
> MAJOR ADVANTAGE:
>
> This is a relatively simple way of introducing named parameters to the Java
> platform.
>
> MAJOR BENEFIT:
>
> Named parameters allow method calls with relatively long lists of parameters
> (greater than 3) to be understood by developers.  This can also facilitate
> the direct use of constructors and factory methods to create immutable
> objects, where otherwise Builders or mutable JavaBeans would be required.
>
> MAJOR DISADVANTAGE:
>
> The syntax for method calls would change to allow both named and unnamed
> parameters to be used.
>
> Named parameters might be used too often, which could unnecessarily clutter
> source files.
>
> Metadata to store the names of the parameters must be added to classfiles
> (for example as annotations).
>
> The use of annotations to describe named parameters would mean that no
> metadata would be stored about the parameter names used by the method
> caller, and so no runtime checks to match the parameter names being used
> could be made (only compile-time).  If the parameter names change (but
> otherwise the method signature does not), then the method caller would not
> be aware of the changes until it was recompiled.  Note that this is existing
> behaviour for unnamed parameters, and would only be a problem if the meaning
> of the parameters also changes (which should indicate that the caller would
> need to change anyway, but this would not be detected automatically at
> runtime).
>
> ALTERNATIVES:
>
> Unnamed parameters can make the same method calls as named parameters, but
> if there are many parameters they are harder to understand and prone to
> ordering-related bugs (particularly for primitive types or Strings).
>
> The Builder pattern can be used to simulate named parameters in
> constructors/factory methods.  For example the following class uses a
> Builder to initialise itself (note that only two properties are used to
> simplify the example):
>
>     public final class MyClass {
>
>         private final String name;
>         private final int age;
>
>         private MyClass(Builder b) {
>             this.name = b.name;
>             this.age = b.age;
>         }
>
>         public static class Builder {
>
>             private String name;
>             private int age;
>
>             /**
>              * Name to set.
>              */
>             public Builder setName(String name) {
>                this.name = name;
>                return this;
>             }
>
>             /**
>              * Age to set
>             */
>             public Builder setAge(int age) {
>                 this.age = age;
>                 return this;
>             }
>
>             public MyClass build() {
>                return new MyClass(this);
>             }
>         }
>     }
>
> Objects can then be constructed in the following manner:
>
>     MyClass obj = new MyClass.Builder().setName("Fred").setAge(53).build();
>
> However, the use of a builder requires additional code, and all parameters
> are effectively optional from the perspective of the compiler (it cannot
> easily check that all of the required setter methods have been called), so
> bugs may occur where parameter values are not set.  Note that runtime checks
> can be made to ensure that all property values are set, but they involve
> additional work and cannot be used by the compiler (though static analysis
> of the code in conjunction with annotations might be able to repeat many of
> these checks).
>
> There are also many ways to implement named parameters that are different to
> the solution proposed here.  These include:
>
> Implement optional named parameters on all methods:  This avoids the need
> for the @PublicParameterNames annotation, but may mean inconsistent usage of
> named parameters - the annotation is also a suggestion for the use of named
> parameters by the caller (which IDEs can also make use of).  This will also
> highlight the difference to classfiles compiled with earlier versions of
> Java, where named parameters cannot be used at all (since it will then not
> be obvious when named parameters can and cannot be used).
>
> Add parameter names to the classfile as 'fundamental' method metadata rather
> than as annotations: This may allow closer integration of the named
> parameters with the rest of the language, but its impact on the rest of the
> language (and JVM) is much greater.  The same inconsistencies and
> incompatibilities described in the previous alternative would also apply.
> In addition, the use of annotations should not preclude the subsequent
> modification of classfiles in a later release - the annotations could still
> remain (at a potential cost of some duplication).
>
> EXAMPLES
>
> SIMPLE EXAMPLE:
>
> Constructor declaration:
>
>     @PublicParameterNames
>     public MyClass(String name, int age) { ....
>
> Constructor use:
>
>     MyClass obj = new MyClass(name: "Fred", age: 53);
>
> ADVANCED EXAMPLE: Show advanced usage(s) of the feature.
>
> The full class definition from the simple example is shown below, as a
> contrast to that provided in the Builder example.
>
>     public final class MyClass {
>
>         private final String name;
>         private final int age;
>
>         /**
>          * @param name Name to set
>          * @param age Age to set
>          */
>
>         @PublicParameterNames
>         public MyClass(String name, int age) {
>             this.name = name;
>             this.age = age;
>         }
>     }
>
> DETAILS
>
> SPECIFICATION:
>
> The @PublicParameterNames annotation is used on a constructor or method to
> allow named parameters to be used when calling it.  It can also be applied
> to a class or package to apply to all methods within.  Similarly, a
> @NoParameterNames annotation can be used on a constructor, method, or class
> to override the use of @PublicParameterNames at a higher level.
>
> The compiler can then automatically generate a
> @PublicParameterName(value="parameter-name") annotation for each affected
> method.  These can then be used by the compiler (and IDE) to validate the
> parameter names used by callers of the method or constructor.
>
> The use of parameter names by callers is always optional (primarily for
> backwards compatibility).  However, parameter names cannot be used for some
> parameters and not others (this would make the code harder to read).
>
> Parameters must always be specified in the same order regardless of whether
> parameter names are used - parameter reordering by callers is not allowed
> (reordering would make overloading difficult, and is not really necessary).
>
> Inheritance: Neither the @PublicParameterNames annotation (and
> @NoParameterNames annotation), or the names of the parameters themselves,
> need to be inherited.  This is because only static evaluation of a caller's
> parameter names will be applied (rather than at runtime), so the callers
> parameter names only need to match those of the declared type of the
> target.  However, it would still be advisable to reuse the same parameter
> names and annotations when overriding a method (IDEs could help with this).
>
> COMPILATION:
>
> The compiler must automatically generate a
> @PublicParameterName(value="parameter-name") annotation for each method and
> constructor annotated with @PublicParameterNames (or whose the parent class
> or package is annotated with @PublicParameterNames and the child class or
> method does not override it with @NoParameterNames).
>
> For example:
>
>     int myMethod(int param1, String param2)
>
> Would effectively become:
>
>     int myMethod(@PublicParameterName("param1") int param1,
> @PublicParameterName("param2") String param2)
>
> Method-calling syntax would need to change, using a colon to separate the
> parameter name and value where the are used.  For example:
>
>    MyClass obj = new MyClass(name: "Fred", age: 53);
>
> When a method caller uses parameter names, the compiler must check that
> those parameter names exactly match the value of generated
> @PublicParameterName annotations of the target method or constructor.  It is
> a compilation error if they do not match or the target method or constructor
> does not have named parameters.
>
> IDEs can use the @PublicParameterNames and @NoParameterNames annotations (or
> @PublicParameterName directly) to automatically insert the relevant
> parameter names as part of code-completion.  Additional refactoring support
> would also be required to enable parameter names to be renamed, or added and
> removed completely.
>
> Frameworks such as Spring can use the same annotations to allow objects to
> be created from their configuration files using named parameters to
> constructors and factory methods.  Currently they only allow objects to be
> created from configuration files as JavaBeans (with setter methods) or with
> ordered (and unnamed) parameters.
>
> TESTING:
>
> The feature can be tested by compiling and running programs that exercise
> the feature.
>
> LIBRARY SUPPORT:
>
> No.
>
> REFLECTIVE APIS:
>
> java.lang.reflect.Method and java.lang.reflect.Constructor could be enhanced
> with new methods that return parameter names.  However, that is not required
> to successfully implement the proposal.
>
> OTHER CHANGES:
>
> No.  The use of named parameters is always optional.  The javadoc tool
> already documents parameter names.  Other tools/libraries might benefit from
> these changes, but their use is not required.
>
> MIGRATION:
>
> The @PublicParameterNames annotation (and @NoParameterNames annotation)
> simply needs to be added to the appropriate methods.  IDEs could then
> suggest the use of parameter names for the method's callers, and apply the
> changes automatically.
>
> COMPATIBILITY
>
> BREAKING CHANGES:
>
> No.
>
> EXISTING PROGRAMS:
>
> The changes required by this feature should be transparent to existing
> source and class files if annotations are used internally to describe the
> named parameters.  I am not sure what the impact would be otherwise.
>
> REFERENCES
>
> EXISTING BUGS:
>
> 4124331 (though it is set to 11-Closed, Will Not Fix, request for
> enhancement, and from 1998)
>
>   



From Joe.Darcy at Sun.COM  Tue Apr 21 08:36:56 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Tue, 21 Apr 2009 08:36:56 -0700
Subject: SUBMISSION : A second look on "named parameters" / Clarification
	on the scope
In-Reply-To: <E807B68F-1621-4AD7-8052-146B0C45FB89@zwitserloot.com>
References: <2dc3bd00904200118s35e085fdk6f4ef3cac83cd6e9@mail.gmail.com>
	<E807B68F-1621-4AD7-8052-146B0C45FB89@zwitserloot.com>
Message-ID: <49EDE818.3060101@sun.com>

A few notes on this topic.

Support for retrieving parameter names was removed from the feature list 
of JDK 6; there was never any working code to implement this feature.

Implementing this functionality would be nontrivial, for coordination 
reasons if no others.  Names are stored in the class file at certain 
debugging levels.  However, there is no Java-level API to return that 
information.  A new (small) VM interface would need to be written to 
retrieve and pass on this information to the libraries.  Unconditionally 
storing parameter names all the time is unattractive because the names 
would take up space.  Yes, some people do care about the sizes of their 
jar files, (like rt.jar :-), and adding such information that in many 
cases would be little used or ignore is not desirable.  A further 
technical wrinkle, the number of parameters in the source code and the 
number of parameters in the class file sometimes disagree, with the 
class file having more (outer this parameter for some nested class 
constructors, implicit ordinal parameters for enum constructors) and 
there is currently no reliable data in the class file to determine 
whether or not a parameter is synthetic.  For example, constructors for 
anonymous classes appearing in a static context, like a static 
initializer block, do not need to have an enclosing instance parameter.  
These are certainly solvable technical problems, but someone needs to 
solve them.

The parameter names are useful when interfacing Java to other language 
environments that like sql use nominal rather than position parameter 
passing.  However, in terms of the overall Java elephant, I don't 
perceive this as a prevalent pattern.

Additionally, exposing the parameters names introduces a de facto new 
behavioral compatibility constraint; that is, you can no long change the 
parameter names of your methods and constructors without regard for the 
compatibility consequences because users can be relying on the names.

I encourage people interested in this feature to develop a prototype.

-Joe

Reinier Zwitserloot wrote:
> Ah, now I understand.
>
> I've got a much simpler proposal to address this issue.
>
> NB: Joe, I know coin's long gone, but perhaps consider this one anyway 
> - it seems to me that some sort of named parameters proposal is likely 
> to be accepted in the future, and adding names now should ease 
> transition. As part of the effort I've listed all possibly 
> complication I can come up with, at the end.
>
> Proposal:
>
>
> Starting from the new class file format introduced in java7 (due to 
> module support, the class format is definitely getting a version 
> bump), all compilers MUST put the names of the parameters in the class 
> file (javac -g style), and obfuscators/compressors/whatever MUST NOT 
> remove this; a class file with version v50 (or whatever number its 
> going to end up being) won't even pass the verifier without the names 
> in place.
>
> Add an API call on the java.lang.reflect.Method object to obtain the 
> names of the parameters (returns a String[], or 'null' if they aren't 
> there. Calling this on a param-less method returns an empty array, not 
> null). Having the names is an all-or-nothing situation: Either the 
> names are all there and this call works, or some/all are missing, and 
> then this call does not work. I'm not sure if you can even have just a 
> few names defined in the .class file format, but even if you can, that 
> situation should be so extremely rare, its not worth writing up a 
> complicated rule for). It is guaranteed that if the array exists (is 
> not null), then each array element is not null.
>
> Voila. No need to turn in a proposal that's more complicated than most 
> just to solve this simple problem.
>
> Complications:
>
> A) It would no longer be possible to rewrite a v49 and below class 
> without debug info into a v50 and up class file without having the 
> source file, but I don't actually know of any tools that attempt to do 
> this.
>
> B) Code that generates class files on the fly (like proxy generators 
> and the like) will need to consider the names of method parameters 
> if/when they update the class file format they generate to v50+. A 
> proxy generator has issues when it is trying to generate a v50+ proxy 
> where its input object's class spec AND the input interface to proxy 
> on are both v49- without debug info, for example.
>
> C) A (bad) quick-fix for either of the above issues is to just use 
> 'arg0', 'arg1', 'arg2', analogous to what e.g. eclipse does when 
> showing method signatures for methods in classes where there is no 
> source, no debug info and no javadoc. This is not at all the right 
> idea. A small risk that the class file format documentation should 
> mention as not being appropriate unless there is absolutely no other 
> option.
>
> D) Most code these days ships with source, or javadoc, or debug info, 
> so that auto-complete shows the proper names for each parameter, but 
> this certainly isn't true for /all/ java code out there. After this 
> change, method param names become visible to all. This may not be a 
> desired side-effect for programming shops that export libraries to 
> clients where their method parameter names are inappropriate (swear 
> words, or 'x', 'y', and 'z' and this creates deserved but nevertheless 
> unexpected ridicule for sucking at programming style). I think this is 
> an acceptable price to pay. Parameters are method-local which are 
> extremely easy to rename with your friendly neighbourhood IDE's 
> refactor tool.
>
> E) While technically the names are NOT part of API, and you CAN freely 
> change names around without breaking any code, old or new, the names 
> still do become a little more enshrined as at least almost part of the 
> public API. This is already the case to some extent (param names show 
> up in various tooling support such as javadoc and auto-completing 
> IDEs) but this change would move parameter names a little more towards 
> a complete member of public API. This is an issue, but its also the 
> point of this proposal: Move towards a java world where parameter 
> names are universally available and are meaningful. I don't think this 
> is a serious problem, because A) names already have a flavour of 
> importance right now, and B) While they become more important with 
> this proposal, they still aren't true public API, and changing names 
> even after this proposal is accepted is not backwards incompatible.
>
> F) Confusion may arise when these names are unintentionally taken as 
> being either part of public API, or being hierarchical; they are in 
> fact neither. For example, this proposal makes no attempt to harmonize 
> name conflicts; if interface A has void foo(int bar), and interface B 
> has void foo(int baz), you can still of course write a class that 
> implements both of these. You can even name your foo's parameter 
> 'floobargle', of course. The aim of this proposal does not involve 
> making parameter names inherit sensibly.
>
>
>  --Reinier Zwitserloot
>
>
>
> On Apr 20, 2009, at 10:18, Jean-Baptiste Bugeaud wrote:
>
>> Hello Reinier, Hello Joe,
>>
>> Thanks for your feedback.
>>
>> 2009/4/19 Reinier Zwitserloot <reinier at zwitserloot.com>:
>>> Your proposal is very incomplete. Three major nits:
>>>
>>> A. Did I miss something, or did you totally forget to include an 
>>> example of
>>> calling a method with named parameters? Something like:
>>>
>>> doLogin(user: "foobar", password: new char[] { 'a', 'b', 'c' })
>>
>> Reiner, I think my submission name is misleading everybody. This is
>> not the same thing you debate some times back. My mistake ... I should
>> have clarified from the start : I do not look at adding direct call by
>> parameter name into the language (say "? la" ObjectiveC). But simply a
>> reliable way access to parameter name and name a parameter's name in
>> static way thru time. See bug 6444738 for differences.
>>
>> Parameter names are very usefull information in most cases, and at
>> this time, either implementers use duplicate annotation (dummy
>> annotations storing again the same name) or they use tools such as ASM
>> to workaround the lack of API in the JDK.
>>
>> At the begining, I thought this requirement did not required a small
>> synthax language change : a new API would be enough. But soon I
>> realized that introducing name parameter that are static thru time,
>> introduce anyway a new paradigm in the language that developer should
>> be able to control directly : do I want this parameter name to be
>> static thu time ? or do I want to let the compiler decide as usual ?
>>
>> A compiler option is not the suitable tool for this.
>> If this is a global switch, it will not offer the fine grain required.
>> If this is a per class/per package option, it will clutter the 
>> command line.
>> And in both cases, it will not offer paradigm separation with the
>> legacy. Thus you can not rely on the parameter name because you never
>> know if developper has stored the name accidentaly or for purpose.
>>
>>> B. Why static? You might as well have picked 'strictfp' - it's a total
>>> non-sequitur choice. Re-use of existing keywords is not really a 
>>> panacea; it
>>> waters down the anchoring ability of a keyword to virtually nothing. 
>>> I'm not
>>> sure if context-sensitive keywords are any better, but java7 is already
>>> going to have at least one ('module'), so don't beat around the bush 
>>> and
>>> just call it 'named'). Could be just me, but introducing a change 
>>> which is
>>> not backwards compatible IF you have a type that's called 'named' 
>>> (written
>>> just like that, all-lower case), is not something I find troublesome 
>>> in the
>>> least. That's very ugly code, and a migration tool can fix this easily.
>>
>> Because of the definition a dictionary gives of it : something like
>> "showing little change" is exactly what I meant for this paradigm. And
>> no "strictfp", as well as "const" and "goto" are not matching, you see
>> ;-)
>>
>> If you think that this worth integrating a new keywork, then there is
>> room for debate. I think static fits perfectly and is clear enough.
>> AFAIK, we already have final that is contextual? why not static too ?
>> final is already stretched between two things : do not overload member
>> and do not reasign variable.
>>
>> With the proposed language changed static modifier will be stretched
>> between static thru instances for members and static thru time for
>> variables.
>>
>>> C. You don't mention having default values for parameters, which is 
>>> sort of
>>> the point of this exercise (otherwise you really still need 
>>> builders  ; any
>>> method that has so many parameters that they need names probably 
>>> needs a
>>> builder, and without defaults, not providing one and instead relying on
>>> named params is just an inferior bandaid to your ugly API; to get it 
>>> right
>>> you STILL need to provide a builder. If, however, parameters can have
>>> defaults, then you no longer need to make builders at all).
>>
>> This is because I am not asking for named call of method ... simply
>> for a way to access name of parameter. Just a completely different
>> topic.
>> I don't see why a parameter on an EJB is not meanfull for the external
>> ? same for an webservice ? why a parameter name could not be meanfull
>> ? I don't get your point.
>>
>> My design decision is the kind of decision that led to erasure based
>> genericity : it has some drawback, loss of real parametrics instances
>> that could be usefull while reflection. But was the right decision at
>> the right time or either we would have lots binary compatibility or we
>> would still be debating wether or not implementing generics.
>>     
>> My proposition on parameter name is analog, it is just meant to be
>> used ASAP but does it does not fully solve all the possible
>> expectations from this topic scope. Namely, should we call "by
>> parameter name" in the language ? and how ?
>>
>> Room is let for the coming decade ;-) But the propopsition does not
>> close doors to anything.
>>
>>> I suggest you look over the coin-dev mailing list; I entered a rough 
>>> sketch
>>> of a named parameters proposal near the end of coin. I never wrote 
>>> it up
>>> because I thought of it far too close to the deadline, and it's 
>>> still of
>>> such high impact that I doubt it would pass muster for coin.
>>
>> Yes I've followed the debate :) But, again its my mistake "call by
>> parameter names" is a much more complex topic with lots of
>> performance/plaform impact. This is not a small language change IMHO.
>> Again, I do not look for calling a direct method call using named
>> parameters .... just a way to retreive them.
>>
>> -- --
>>
>> Joe, yes "late I am" ;-)
>>
>> FYI, I got this proposition cooking for several months I was not able
>> to find time to write & post it to you (pittyfull isn't it).
>>
>> If we remove the "language change" part (static named parameter) and
>> only keep the getParameterNames() API part (keep the regular parameter
>> name), do you think this can be pushed to JDK7 even if out of scope of
>> coin ? This is a very small change to the API and would solve lot of
>> time from lot of people.
>>
>> I mean, this API (along with the rest of the named parameter spec) was
>> removed from JDK6, skiping this in JDK7 means years again to wait for
>> it ? I think we are too much getting dependent on tools such as ASM in
>> lots of places (JavaEE implementation stacks for instance). And we
>> have a good opportunity to remove the dependency for a clean/simple
>> solution IMHO.
>>
>> Best Regards,
>> JB
>



From Ulf.Zibis at gmx.de  Tue Apr 21 08:47:56 2009
From: Ulf.Zibis at gmx.de (Ulf Zibis)
Date: Tue, 21 Apr 2009 17:47:56 +0200
Subject: scripts and results (was Helping to find the usefulness of a
	proposal)
In-Reply-To: <114ad93adfd2eb30f7ecd1388b69b1be.squirrel@wmail.gradsoft.ua>
References: <60287e9e1530b3e1ae49976316e8dc57.squirrel@wmail.gradsoft.ua>
	<49E5F020.7060508@gmx.de>
	<114ad93adfd2eb30f7ecd1388b69b1be.squirrel@wmail.gradsoft.ua>
Message-ID: <49EDEAAC.2040100@gmx.de>

Am 16.04.2009 08:27, Ruslan Shevchenko schrieb:
>> Hi Ruslan,
>>
>> I would like to see the results for
>>
>>      "objects and expressions in switch"
>>
>> which includes:
>> - string in switch
>> - instanceof switch
>>
>> I guess a very big chunk of all if-else if-structures would be covered by:
>> http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001182.html
>>
>>     
>
> Ok, I will alloc some time during next week-end for more patterns and
> statistics and will try include this one.  This will some 'near' refinemed
> of proposal, becouse original proposal does not define what is 'leftPart'
> and 'rightPart' of Java expression in formal way [this is not so trivial,
> as expected. For example what left part will be in function expressions:
> 'this' or nothing ?. How we split chained expressions on left and right ?]
>  For this reasons, I guess probability that this proposal will seen
> seriously is very low.
>
>
> (Second change which I plan: add statistics about relative number of
> chainged construction/number of  all such constructions).
>
>
>   

Hi Ruslan,

as I see, your didn't have time for more patterns. :-(

Hopfully you will find time next days. :-)

Regards,

Ulf




From neal at gafter.com  Tue Apr 21 08:52:38 2009
From: neal at gafter.com (Neal Gafter)
Date: Tue, 21 Apr 2009 08:52:38 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904210834l55f665d9w52613c792989abb0@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com> 
	<15e8b9d20904210800v762e39a4t5ba75d660780e2@mail.gmail.com> 
	<17b2302a0904210834l55f665d9w52613c792989abb0@mail.gmail.com>
Message-ID: <15e8b9d20904210852t2b8aa5f7n77012ae7397b6eb1@mail.gmail.com>

On Tue, Apr 21, 2009 at 8:34 AM, Joshua Bloch <jjb at google.com> wrote:

> Yes, this is the situation that Bruce Chapman pointed out earlier.  As a
> practical matter, I suspect that resources will have rather simple types,
> but still the spec does have to cover this situation.  If you have a good
> solution, feel free to share.  Otherwise, hang on, and we'll see what we can
> come up with.
>

In the LocalVariableTypeTable, conjunctive types should be simple to add.
Recursive types can be handled by introducing backreferences.

You can probably avoid this mess by being explicit about the specification
rather than attempting the "as-if" rewriting.  If a construct like this is
to be integrated into the JLS that would probably be required anyway, and a
new set of issues is likely to be exposed by the attempt.  It would be
better to get the specification wrung out earlier rather than later (I don't
think Alex will be eager to do it himself).


From forax at univ-mlv.fr  Tue Apr 21 09:12:07 2009
From: forax at univ-mlv.fr (=?ISO-8859-1?Q?R=E9mi_Forax?=)
Date: Tue, 21 Apr 2009 18:12:07 +0200
Subject: Automatic Resource Management, V.2
In-Reply-To: <15e8b9d20904210852t2b8aa5f7n77012ae7397b6eb1@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<15e8b9d20904210800v762e39a4t5ba75d660780e2@mail.gmail.com>
	<17b2302a0904210834l55f665d9w52613c792989abb0@mail.gmail.com>
	<15e8b9d20904210852t2b8aa5f7n77012ae7397b6eb1@mail.gmail.com>
Message-ID: <49EDF057.3080906@univ-mlv.fr>

Neal Gafter a ?crit :
> On Tue, Apr 21, 2009 at 8:34 AM, Joshua Bloch <jjb at google.com> wrote:
>
>   
>> Yes, this is the situation that Bruce Chapman pointed out earlier.  As a
>> practical matter, I suspect that resources will have rather simple types,
>> but still the spec does have to cover this situation.  If you have a good
>> solution, feel free to share.  Otherwise, hang on, and we'll see what we can
>> come up with.
>>
>>     
>
> In the LocalVariableTypeTable, conjunctive types should be simple to add.
> Recursive types can be handled by introducing backreferences.
>
> You can probably avoid this mess by being explicit about the specification
> rather than attempting the "as-if" rewriting.  If a construct like this is
> to be integrated into the JLS that would probably be required anyway, and a
> new set of issues is likely to be exposed by the attempt.  It would be
> better to get the specification wrung out earlier rather than later (I don't
> think Alex will be eager to do it himself).
>
>   
Why the local var need to be visible in these tables ?

The compiler already introduced new local var , by example, in case of 
++/-- and
compound assignments on boxed type (using the hidden instruction LetExpr).
In that case the local var is flagged SYNTHETIC and doesn't appear in 
local vars tables.

R?mi


From neal at gafter.com  Tue Apr 21 09:48:06 2009
From: neal at gafter.com (Neal Gafter)
Date: Tue, 21 Apr 2009 09:48:06 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <49EDF057.3080906@univ-mlv.fr>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com> 
	<15e8b9d20904210800v762e39a4t5ba75d660780e2@mail.gmail.com> 
	<17b2302a0904210834l55f665d9w52613c792989abb0@mail.gmail.com> 
	<15e8b9d20904210852t2b8aa5f7n77012ae7397b6eb1@mail.gmail.com> 
	<49EDF057.3080906@univ-mlv.fr>
Message-ID: <15e8b9d20904210948s58366d7as4bcbd1cea653bc6@mail.gmail.com>

On Tue, Apr 21, 2009 at 9:12 AM, R?mi Forax <forax at univ-mlv.fr> wrote:

>
>> You can probably avoid this mess by being explicit about the specification
>> rather than attempting the "as-if" rewriting.  If a construct like this is
>> to be integrated into the JLS that would probably be required anyway, and
>> a
>> new set of issues is likely to be exposed by the attempt.  It would be
>> better to get the specification wrung out earlier rather than later (I
>> don't
>> think Alex will be eager to do it himself).
>>
>>
>>
> Why the local var need to be visible in these tables ?
>
> The compiler already introduced new local var , by example, in case of
> ++/-- and
> compound assignments on boxed type (using the hidden instruction LetExpr).
> In that case the local var is flagged SYNTHETIC and doesn't appear in local
> vars tables.


Right: if the specification is spelled out, one can decide on a case-by-case
basis how to handle the mapping to the class file. However, you can't avoid
these variables appearing in the verifier tables at the very least.  In that
case the natural type based on the current spec is its erasure, which is not
necessarily AutoCloseable.


From tball at google.com  Tue Apr 21 10:24:07 2009
From: tball at google.com (Tom Ball)
Date: Tue, 21 Apr 2009 10:24:07 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <15e8b9d20904210948s58366d7as4bcbd1cea653bc6@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com> 
	<15e8b9d20904210800v762e39a4t5ba75d660780e2@mail.gmail.com> 
	<17b2302a0904210834l55f665d9w52613c792989abb0@mail.gmail.com> 
	<15e8b9d20904210852t2b8aa5f7n77012ae7397b6eb1@mail.gmail.com> 
	<49EDF057.3080906@univ-mlv.fr>
	<15e8b9d20904210948s58366d7as4bcbd1cea653bc6@mail.gmail.com>
Message-ID: <ecf3d2390904211024g6802b61dk7ac056391ea3fbef@mail.gmail.com>

My "vote" (I realize this isn't a democracy :-) is to avoid adding any new
rules, but instead keep it simple:  resources in source code go into all
tables like any other local variable currently does, while any
compiler-generated temporary variables get flagged as synthetic and are
included in any tables that include synthetic variables.  In other words, a
resource should be treated exactly like a local variable already is,
synthetic or not.  A resource is a local variable, after all, just one that
has some automatic cleanup as it leaves scope.

BTW, I like Bruce Chapman's suggestion that the type of a temporary variable
be AutoCloseable.  Since the only thing the compiler generated code will do
with that object is call its close() method, there's no advantage to it
having additional type information.

Tom

On Tue, Apr 21, 2009 at 9:48 AM, Neal Gafter <neal at gafter.com> wrote:

> On Tue, Apr 21, 2009 at 9:12 AM, R?mi Forax <forax at univ-mlv.fr> wrote:
>
> >
> >> You can probably avoid this mess by being explicit about the
> specification
> >> rather than attempting the "as-if" rewriting.  If a construct like this
> is
> >> to be integrated into the JLS that would probably be required anyway,
> and
> >> a
> >> new set of issues is likely to be exposed by the attempt.  It would be
> >> better to get the specification wrung out earlier rather than later (I
> >> don't
> >> think Alex will be eager to do it himself).
> >>
> >>
> >>
> > Why the local var need to be visible in these tables ?
> >
> > The compiler already introduced new local var , by example, in case of
> > ++/-- and
> > compound assignments on boxed type (using the hidden instruction
> LetExpr).
> > In that case the local var is flagged SYNTHETIC and doesn't appear in
> local
> > vars tables.
>
>
> Right: if the specification is spelled out, one can decide on a
> case-by-case
> basis how to handle the mapping to the class file. However, you can't avoid
> these variables appearing in the verifier tables at the very least.  In
> that
> case the natural type based on the current spec is its erasure, which is
> not
> necessarily AutoCloseable.
>
>


From forax at univ-mlv.fr  Tue Apr 21 10:30:38 2009
From: forax at univ-mlv.fr (=?ISO-8859-1?Q?R=E9mi_Forax?=)
Date: Tue, 21 Apr 2009 19:30:38 +0200
Subject: Automatic Resource Management, V.2
In-Reply-To: <15e8b9d20904210948s58366d7as4bcbd1cea653bc6@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<15e8b9d20904210800v762e39a4t5ba75d660780e2@mail.gmail.com>
	<17b2302a0904210834l55f665d9w52613c792989abb0@mail.gmail.com>
	<15e8b9d20904210852t2b8aa5f7n77012ae7397b6eb1@mail.gmail.com>
	<49EDF057.3080906@univ-mlv.fr>
	<15e8b9d20904210948s58366d7as4bcbd1cea653bc6@mail.gmail.com>
Message-ID: <49EE02BE.1010908@univ-mlv.fr>

Neal Gafter a ?crit :
> On Tue, Apr 21, 2009 at 9:12 AM, R?mi Forax <forax at univ-mlv.fr 
> <mailto:forax at univ-mlv.fr>> wrote:
>
>
>         You can probably avoid this mess by being explicit about the
>         specification
>         rather than attempting the "as-if" rewriting.  If a construct
>         like this is
>         to be integrated into the JLS that would probably be required
>         anyway, and a
>         new set of issues is likely to be exposed by the attempt.  It
>         would be
>         better to get the specification wrung out earlier rather than
>         later (I don't
>         think Alex will be eager to do it himself).
>
>          
>
>     Why the local var need to be visible in these tables ?
>
>     The compiler already introduced new local var , by example, in
>     case of ++/-- and
>     compound assignments on boxed type (using the hidden instruction
>     LetExpr).
>     In that case the local var is flagged SYNTHETIC and doesn't appear
>     in local vars tables.
>
>
> Right: if the specification is spelled out, one can decide on a 
> case-by-case basis how to handle the mapping to the class file. 
> However, you can't avoid these variables appearing in the verifier 
> tables at the very least.  In that case the natural type based on the 
> current spec is its erasure, which is not necessarily AutoCloseable.
If the type is not AutoCloseable, the compile emit a checkcast before 
calling close(),
so it will work even if i agree that this checkcast can be avoided.

R?mi




From jjb at google.com  Tue Apr 21 11:17:19 2009
From: jjb at google.com (Joshua Bloch)
Date: Tue, 21 Apr 2009 11:17:19 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <ecf3d2390904211024g6802b61dk7ac056391ea3fbef@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<15e8b9d20904210800v762e39a4t5ba75d660780e2@mail.gmail.com>
	<17b2302a0904210834l55f665d9w52613c792989abb0@mail.gmail.com>
	<15e8b9d20904210852t2b8aa5f7n77012ae7397b6eb1@mail.gmail.com>
	<49EDF057.3080906@univ-mlv.fr>
	<15e8b9d20904210948s58366d7as4bcbd1cea653bc6@mail.gmail.com>
	<ecf3d2390904211024g6802b61dk7ac056391ea3fbef@mail.gmail.com>
Message-ID: <17b2302a0904211117s71f2c748p712898e5b0346796@mail.gmail.com>

Tom,

Thanks!  This seems like the obvious correct solution.  I feel like a fool
for not having done it that way in the first place.

           Josh

On Tue, Apr 21, 2009 at 10:24 AM, Tom Ball <tball at google.com> wrote:

> My "vote" (I realize this isn't a democracy :-) is to avoid adding any new
> rules, but instead keep it simple:  resources in source code go into all
> tables like any other local variable currently does, while any
> compiler-generated temporary variables get flagged as synthetic and are
> included in any tables that include synthetic variables.  In other words, a
> resource should be treated exactly like a local variable already is,
> synthetic or not.  A resource is a local variable, after all, just one that
> has some automatic cleanup as it leaves scope.
>
> BTW, I like Bruce Chapman's suggestion that the type of a temporary
> variable
> be AutoCloseable.  Since the only thing the compiler generated code will do
> with that object is call its close() method, there's no advantage to it
> having additional type information.
>
> Tom
>
> On Tue, Apr 21, 2009 at 9:48 AM, Neal Gafter <neal at gafter.com> wrote:
>
> > On Tue, Apr 21, 2009 at 9:12 AM, R?mi Forax <forax at univ-mlv.fr> wrote:
> >
> > >
> > >> You can probably avoid this mess by being explicit about the
> > specification
> > >> rather than attempting the "as-if" rewriting.  If a construct like
> this
> > is
> > >> to be integrated into the JLS that would probably be required anyway,
> > and
> > >> a
> > >> new set of issues is likely to be exposed by the attempt.  It would be
> > >> better to get the specification wrung out earlier rather than later (I
> > >> don't
> > >> think Alex will be eager to do it himself).
> > >>
> > >>
> > >>
> > > Why the local var need to be visible in these tables ?
> > >
> > > The compiler already introduced new local var , by example, in case of
> > > ++/-- and
> > > compound assignments on boxed type (using the hidden instruction
> > LetExpr).
> > > In that case the local var is flagged SYNTHETIC and doesn't appear in
> > local
> > > vars tables.
> >
> >
> > Right: if the specification is spelled out, one can decide on a
> > case-by-case
> > basis how to handle the mapping to the class file. However, you can't
> avoid
> > these variables appearing in the verifier tables at the very least.  In
> > that
> > case the natural type based on the current spec is its erasure, which is
> > not
> > necessarily AutoCloseable.
> >
> >
>
>


From tball at google.com  Tue Apr 21 11:19:20 2009
From: tball at google.com (Tom Ball)
Date: Tue, 21 Apr 2009 11:19:20 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904211117s71f2c748p712898e5b0346796@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com> 
	<15e8b9d20904210800v762e39a4t5ba75d660780e2@mail.gmail.com> 
	<17b2302a0904210834l55f665d9w52613c792989abb0@mail.gmail.com> 
	<15e8b9d20904210852t2b8aa5f7n77012ae7397b6eb1@mail.gmail.com> 
	<49EDF057.3080906@univ-mlv.fr>
	<15e8b9d20904210948s58366d7as4bcbd1cea653bc6@mail.gmail.com> 
	<ecf3d2390904211024g6802b61dk7ac056391ea3fbef@mail.gmail.com> 
	<17b2302a0904211117s71f2c748p712898e5b0346796@mail.gmail.com>
Message-ID: <ecf3d2390904211119j4481bc31wa9449f3fd0cc1f81@mail.gmail.com>

Things language and compiler-related are only ever obvious in hindsight. :-)

On Tue, Apr 21, 2009 at 11:17 AM, Joshua Bloch <jjb at google.com> wrote:

> Tom,
>
> Thanks!  This seems like the obvious correct solution.  I feel like a fool
> for not having done it that way in the first place.
>
>            Josh
>
>
> On Tue, Apr 21, 2009 at 10:24 AM, Tom Ball <tball at google.com> wrote:
>
>> My "vote" (I realize this isn't a democracy :-) is to avoid adding any new
>> rules, but instead keep it simple:  resources in source code go into all
>> tables like any other local variable currently does, while any
>> compiler-generated temporary variables get flagged as synthetic and are
>> included in any tables that include synthetic variables.  In other words,
>> a
>> resource should be treated exactly like a local variable already is,
>> synthetic or not.  A resource is a local variable, after all, just one
>> that
>> has some automatic cleanup as it leaves scope.
>>
>> BTW, I like Bruce Chapman's suggestion that the type of a temporary
>> variable
>> be AutoCloseable.  Since the only thing the compiler generated code will
>> do
>> with that object is call its close() method, there's no advantage to it
>> having additional type information.
>>
>> Tom
>>
>> On Tue, Apr 21, 2009 at 9:48 AM, Neal Gafter <neal at gafter.com> wrote:
>>
>> > On Tue, Apr 21, 2009 at 9:12 AM, R?mi Forax <forax at univ-mlv.fr> wrote:
>> >
>> > >
>> > >> You can probably avoid this mess by being explicit about the
>> > specification
>> > >> rather than attempting the "as-if" rewriting.  If a construct like
>> this
>> > is
>> > >> to be integrated into the JLS that would probably be required anyway,
>> > and
>> > >> a
>> > >> new set of issues is likely to be exposed by the attempt.  It would
>> be
>> > >> better to get the specification wrung out earlier rather than later
>> (I
>> > >> don't
>> > >> think Alex will be eager to do it himself).
>> > >>
>> > >>
>> > >>
>> > > Why the local var need to be visible in these tables ?
>> > >
>> > > The compiler already introduced new local var , by example, in case of
>> > > ++/-- and
>> > > compound assignments on boxed type (using the hidden instruction
>> > LetExpr).
>> > > In that case the local var is flagged SYNTHETIC and doesn't appear in
>> > local
>> > > vars tables.
>> >
>> >
>> > Right: if the specification is spelled out, one can decide on a
>> > case-by-case
>> > basis how to handle the mapping to the class file. However, you can't
>> avoid
>> > these variables appearing in the verifier tables at the very least.  In
>> > that
>> > case the natural type based on the current spec is its erasure, which is
>> > not
>> > necessarily AutoCloseable.
>> >
>> >
>>
>>
>


From paul.martin at gmail.com  Tue Apr 21 11:32:13 2009
From: paul.martin at gmail.com (Paul Martin)
Date: Tue, 21 Apr 2009 19:32:13 +0100
Subject: PROPOSAL: Named method parameters
In-Reply-To: <49EDE7E7.7040907@sun.com>
References: <4ce75f920903210915pa2b27b3g38841e342a78de77@mail.gmail.com>
	<49EDE7E7.7040907@sun.com>
Message-ID: <4ce75f920904211132n49386c7aj72ac044e82f6e0a2@mail.gmail.com>

Hi,

Thanks for your reply.

(I've repeated the following request here, as well as at the end of my
reply, since I would really appreciate any suggestions!)

It would be very helpful/interesting to me if anyone could suggest
workable alternatives to solve my immediate problem of creating
immutable objects with required (and named) parameters (in Java code
and/or Spring-style config).

On Tue, Apr 21, 2009 at 4:36 PM, Joseph D. Darcy <Joe.Darcy at sun.com> wrote:
> Catching up on responses, as has been further discussed on the list
> recently, requests in this general vein have been considered before in JDK
> 6. ?While there are certainly use-cases this facility could clarify, I
> remain unconvinced of the cost/benefit ratio of this proposal.

I'm currently using Spring to write a threaded application, and
believe that named method parameters could help in the following ways:

1. Creation of immutable objects by allowing parameter names to be
specified in Java method calls

It is good practice to have immutable objects where possible (or at
least to reduce the mutability of objects) in concurrent applications
(which avoids many publication and synchronization issues, as well as
reducing the program state space).  This means that member variables
of Immutable objects must be marked as final, and so can only be
assigned by the constructor.  There are a number of alternatives:

a. Pass parameter values to the constructor without parameter names.
This is ok when there are very few parameters or they have very
distinct and meaningful types, but not so good otherwise.  It is true
that the IDE can highlight the parameter names (usually as a pop-up or
mouse-over-hover), but I think that it would be easy to miss errors.
Comments after each value could help, but there would be no guarantee
that they are ever correct or that they stay in sync with code
refactoring.

b. Use the Builder pattern (as in Effective Java item #2), which does
allow immutable objects to be created with (effectively) named
parameters, but has the following disadvantages:

- It is more verbose (even in the simplified version that sets builder
members directly in a subclass without using setters)

- More importantly: there is no guarantee that all of the members are
set (without a lot of additional validation code in the Builder) -
effectively all of the members become optional.  If a developer
forgets to set a property in the builder, then the built object will
just get the default value (though conversely, builders are therefore
a reasonable way of getting default parameters).

This also affects refactoring - if a member is added, then it would be
difficult to ensure that all builders were updated to set a value.

Note that it may be possible to enhance analysis tools (such as
Findbugs) to detect cases where not all of a Builder's methods have
been called (perhaps in conjunction with an annotation), but that may
also be impossible in many cases (such as where the Builder is passed
between methods).

c. I also think that this use of the Builder pattern is not really in
the spirit of the GoF book, which states (in its Applicability
section):

(begin quote)
Use the Builder pattern when

    * the algorithm for creating a complex object should be
independent of the parts that make up the object and how they're
assembled.

    * the construction process must allow different representations
for the object that's constructed.
(end quote)

Neither of these are involved in the case where a Builder is just
being used to simulate named parameters (to aid
comprehension/documentation).


To summarise, my requirement for named parameters in Java code is
motivated by the fact that I don't think that there is currently a
nice way to create immutable objects such that the parameter/property
names can be easily seen in the code and that ensures that all
required parameters/properties are specified.

2. Adding parameter names to the classfiles/reflection system for
dynamic object creation

(This section is similar to Jean-Baptiste Bugeaud's proposal, and is
effectively the same as bug 6444738)

This is motivated by my use of Spring, but I think that it is
applicable to other technologies (and maybe even other JVM languages).

Currently in Spring you can define beans by specifying constructor
argument values (anonymously), using and/or property values (via named
setters).  This has the same disadvantages to that shown in section 1:
- Use anonymous constructor parameters, but then the code is harder to
understand and maintain.
- Use properties, which means that your bean cannot be immutable.
- Use a Builder, which involves additional code.  Note that Spring can
check that @Required properties have been set (and also doesn't have
first-class support for Builders, but could be extended to do so).

The same kind of problems occur as in 1, though in this case the
parameter names would need to be available at runtime, for Spring to
interrogate.

The result of this is that (from my experience) most Spring beans are
unnecessarily mutable, since it is unnecessarily difficult to do
otherwise.


There are probably other benefits, but those are the ones that
motivated my proposal; I just feel that the alternatives are
unnecessarily difficult.  What do you do in similar situations?

> A few design notes, a single @PublicParameterNames annotation with a boolean
> member could be used instead of a pair of "do it/don't do it" annotations.

That is a better idea!  How would this sit with the rule against
annotations affecting program flow?  Would it count here, because the
annotation is only causing additional metadata to be generated by the
compiler?

> A full proposal for this facility would need to deal with the cases where
> the number of parameters in the class file differs from the number of
> parameters in the source code, a situation already mildly exposed when
> calling toGenericString on some Method and Constructor objects.

Yes, my proposal didn't have the required level of detail.  If it were
to proceed, then experience from projects such as Paranamer might
help.

> Not supporting parameter reordering greatly simplifies the proposal by
> leaving method selection largely unaffected, but also seems to limit the
> usefulness of the proposal. ?If the main benefit is just seeing the
> parameter name in the program text; can't the IDE do that?
>

The goal of my proposal was just to get the simplest implementation of
named parameters that I thought would work and be useful.  Therefore I
explicitly discounted:
- Parameter reordering - I could only see disadvantages (from the
references at the start of my proposal), without a major benefit.
- Default parameters - This would be a large change to method
resolution, and I thought that it could be addressed independently of
named parameters.  I also think that it is something that can be
already achieved with overloaded methods and/or Builders, whereas
named parameters let us do something new (readable creation of
immutable objects).

> I'd isn't clear to me how @PublicParameterNames would interact with
> overridden methods in class hierarchies.  Presumably the names of the static
> type of the call site would need be match, even though the runtime type
> could differ.  If a subclass overrode a method and changed its parameter
> names (which currently has no affect on compatibility), the subclass would
> no longer be substitutable for the parent class, which would break a
> fundamental design principle.

I guess that could be argued either way:

- Specifying @PublicParameterNames means that overridden methods must
keep the same parameter names, or

- overridden methods can change the parameter names (with the static
type of the call site used as you suggested).

I think that at least the first alternative could be argued for
(though that would limit applicability to only new classes), since
changing the names of getters and setters will break callers, and
named parameters could be considered to be similar to those.

> At least there is no binary compatibility impact since the names would only
> be checked at compile time and binary compatibility is about preserving the
> ability to link.

Yes, that was one of my main goals.


Is that helpful?

It seems that there wasn't a lot of enthusiasm for my proposal (or
Reinier's and Jean-Battiste's alternatives), but I think that there is
some elsewhere (as shown by the blogs that I referenced, and the fact
that it was at least considered for JDK 6).

It would be very helpful/interesting to me if anyone could suggest
workable alternatives to solve my immediate problem of creating
immutable objects with required (and named) parameters (in Java code
and/or Spring-style config).

Regards,

Paul

>
> -Joe
>
> Paul Martin wrote:
>>
>> I'd like to propose the implementation of optionally named method
>> parameters, and suggest that they are particularly useful when creating
>> immutable objects (which are important in our increasingly concurrent
>> world).
>>
>> Note that this is a topic that seems to have been considered before (see
>> the
>> note in http://paulhammant.com/blog/announcing_paranamer.html which
>> suggests
>> that it was even considered for Java 6), but I can't see it in the current
>> list of Java 7 changes or in the Project Coin mailing list archives
>> (though
>> others have also discussed it in relation to Java 7, such as Alex Miller
>> in
>> http://tech.puredanger.com/2007/08/15/dr-java7/ and
>> http://tech.puredanger.com/2007/10/11/java7-roundup-32/). ?Therefore I am
>> proposing it here - I think that it is an important change (unless anyone
>> can suggest how I can reasonably create an immutable object with four or
>> more properties without using a Builder or a list of unnamed parameters).
>>
>> Also note that other relevant references include:
>> http://blogs.sun.com/abuckley/entry/named_parameters (which discusses why
>> parameter reordering might be difficult),
>> http://beust.com/weblog/archives/000096.html (which suggests that we do
>> not
>> need named parameters, but really just shows the use of the Builder
>> pattern
>> which has limitations).
>>
>>
>> Named method parameters
>>
>> AUTHOR(S):
>>
>> Paul Martin
>>
>> OVERVIEW
>>
>> FEATURE SUMMARY:
>>
>> Named parameters allow a method or constructor caller to explicitly state
>> the parameter name of each parameter value passed to the method or
>> constructor. ?Without named parameters, only the order of the parameter
>> values is significant (and it may not be clear what each value
>> represents).
>>
>> MAJOR ADVANTAGE:
>>
>> This is a relatively simple way of introducing named parameters to the
>> Java
>> platform.
>>
>> MAJOR BENEFIT:
>>
>> Named parameters allow method calls with relatively long lists of
>> parameters
>> (greater than 3) to be understood by developers. ?This can also facilitate
>> the direct use of constructors and factory methods to create immutable
>> objects, where otherwise Builders or mutable JavaBeans would be required.
>>
>> MAJOR DISADVANTAGE:
>>
>> The syntax for method calls would change to allow both named and unnamed
>> parameters to be used.
>>
>> Named parameters might be used too often, which could unnecessarily
>> clutter
>> source files.
>>
>> Metadata to store the names of the parameters must be added to classfiles
>> (for example as annotations).
>>
>> The use of annotations to describe named parameters would mean that no
>> metadata would be stored about the parameter names used by the method
>> caller, and so no runtime checks to match the parameter names being used
>> could be made (only compile-time). ?If the parameter names change (but
>> otherwise the method signature does not), then the method caller would not
>> be aware of the changes until it was recompiled. ?Note that this is
>> existing
>> behaviour for unnamed parameters, and would only be a problem if the
>> meaning
>> of the parameters also changes (which should indicate that the caller
>> would
>> need to change anyway, but this would not be detected automatically at
>> runtime).
>>
>> ALTERNATIVES:
>>
>> Unnamed parameters can make the same method calls as named parameters, but
>> if there are many parameters they are harder to understand and prone to
>> ordering-related bugs (particularly for primitive types or Strings).
>>
>> The Builder pattern can be used to simulate named parameters in
>> constructors/factory methods. ?For example the following class uses a
>> Builder to initialise itself (note that only two properties are used to
>> simplify the example):
>>
>> ? ?public final class MyClass {
>>
>> ? ? ? ?private final String name;
>> ? ? ? ?private final int age;
>>
>> ? ? ? ?private MyClass(Builder b) {
>> ? ? ? ? ? ?this.name = b.name;
>> ? ? ? ? ? ?this.age = b.age;
>> ? ? ? ?}
>>
>> ? ? ? ?public static class Builder {
>>
>> ? ? ? ? ? ?private String name;
>> ? ? ? ? ? ?private int age;
>>
>> ? ? ? ? ? ?/**
>> ? ? ? ? ? ? * Name to set.
>> ? ? ? ? ? ? */
>> ? ? ? ? ? ?public Builder setName(String name) {
>> ? ? ? ? ? ? ? this.name = name;
>> ? ? ? ? ? ? ? return this;
>> ? ? ? ? ? ?}
>>
>> ? ? ? ? ? ?/**
>> ? ? ? ? ? ? * Age to set
>> ? ? ? ? ? ?*/
>> ? ? ? ? ? ?public Builder setAge(int age) {
>> ? ? ? ? ? ? ? ?this.age = age;
>> ? ? ? ? ? ? ? ?return this;
>> ? ? ? ? ? ?}
>>
>> ? ? ? ? ? ?public MyClass build() {
>> ? ? ? ? ? ? ? return new MyClass(this);
>> ? ? ? ? ? ?}
>> ? ? ? ?}
>> ? ?}
>>
>> Objects can then be constructed in the following manner:
>>
>> ? ?MyClass obj = new MyClass.Builder().setName("Fred").setAge(53).build();
>>
>> However, the use of a builder requires additional code, and all parameters
>> are effectively optional from the perspective of the compiler (it cannot
>> easily check that all of the required setter methods have been called), so
>> bugs may occur where parameter values are not set. ?Note that runtime
>> checks
>> can be made to ensure that all property values are set, but they involve
>> additional work and cannot be used by the compiler (though static analysis
>> of the code in conjunction with annotations might be able to repeat many
>> of
>> these checks).
>>
>> There are also many ways to implement named parameters that are different
>> to
>> the solution proposed here. ?These include:
>>
>> Implement optional named parameters on all methods: ?This avoids the need
>> for the @PublicParameterNames annotation, but may mean inconsistent usage
>> of
>> named parameters - the annotation is also a suggestion for the use of
>> named
>> parameters by the caller (which IDEs can also make use of). ?This will
>> also
>> highlight the difference to classfiles compiled with earlier versions of
>> Java, where named parameters cannot be used at all (since it will then not
>> be obvious when named parameters can and cannot be used).
>>
>> Add parameter names to the classfile as 'fundamental' method metadata
>> rather
>> than as annotations: This may allow closer integration of the named
>> parameters with the rest of the language, but its impact on the rest of
>> the
>> language (and JVM) is much greater. ?The same inconsistencies and
>> incompatibilities described in the previous alternative would also apply.
>> In addition, the use of annotations should not preclude the subsequent
>> modification of classfiles in a later release - the annotations could
>> still
>> remain (at a potential cost of some duplication).
>>
>> EXAMPLES
>>
>> SIMPLE EXAMPLE:
>>
>> Constructor declaration:
>>
>> ? ?@PublicParameterNames
>> ? ?public MyClass(String name, int age) { ....
>>
>> Constructor use:
>>
>> ? ?MyClass obj = new MyClass(name: "Fred", age: 53);
>>
>> ADVANCED EXAMPLE: Show advanced usage(s) of the feature.
>>
>> The full class definition from the simple example is shown below, as a
>> contrast to that provided in the Builder example.
>>
>> ? ?public final class MyClass {
>>
>> ? ? ? ?private final String name;
>> ? ? ? ?private final int age;
>>
>> ? ? ? ?/**
>> ? ? ? ? * @param name Name to set
>> ? ? ? ? * @param age Age to set
>> ? ? ? ? */
>>
>> ? ? ? ?@PublicParameterNames
>> ? ? ? ?public MyClass(String name, int age) {
>> ? ? ? ? ? ?this.name = name;
>> ? ? ? ? ? ?this.age = age;
>> ? ? ? ?}
>> ? ?}
>>
>> DETAILS
>>
>> SPECIFICATION:
>>
>> The @PublicParameterNames annotation is used on a constructor or method to
>> allow named parameters to be used when calling it. ?It can also be applied
>> to a class or package to apply to all methods within. ?Similarly, a
>> @NoParameterNames annotation can be used on a constructor, method, or
>> class
>> to override the use of @PublicParameterNames at a higher level.
>>
>> The compiler can then automatically generate a
>> @PublicParameterName(value="parameter-name") annotation for each affected
>> method. ?These can then be used by the compiler (and IDE) to validate the
>> parameter names used by callers of the method or constructor.
>>
>> The use of parameter names by callers is always optional (primarily for
>> backwards compatibility). ?However, parameter names cannot be used for
>> some
>> parameters and not others (this would make the code harder to read).
>>
>> Parameters must always be specified in the same order regardless of
>> whether
>> parameter names are used - parameter reordering by callers is not allowed
>> (reordering would make overloading difficult, and is not really
>> necessary).
>>
>> Inheritance: Neither the @PublicParameterNames annotation (and
>> @NoParameterNames annotation), or the names of the parameters themselves,
>> need to be inherited. ?This is because only static evaluation of a
>> caller's
>> parameter names will be applied (rather than at runtime), so the callers
>> parameter names only need to match those of the declared type of the
>> target. ?However, it would still be advisable to reuse the same parameter
>> names and annotations when overriding a method (IDEs could help with
>> this).
>>
>> COMPILATION:
>>
>> The compiler must automatically generate a
>> @PublicParameterName(value="parameter-name") annotation for each method
>> and
>> constructor annotated with @PublicParameterNames (or whose the parent
>> class
>> or package is annotated with @PublicParameterNames and the child class or
>> method does not override it with @NoParameterNames).
>>
>> For example:
>>
>> ? ?int myMethod(int param1, String param2)
>>
>> Would effectively become:
>>
>> ? ?int myMethod(@PublicParameterName("param1") int param1,
>> @PublicParameterName("param2") String param2)
>>
>> Method-calling syntax would need to change, using a colon to separate the
>> parameter name and value where the are used. ?For example:
>>
>> ? MyClass obj = new MyClass(name: "Fred", age: 53);
>>
>> When a method caller uses parameter names, the compiler must check that
>> those parameter names exactly match the value of generated
>> @PublicParameterName annotations of the target method or constructor. ?It
>> is
>> a compilation error if they do not match or the target method or
>> constructor
>> does not have named parameters.
>>
>> IDEs can use the @PublicParameterNames and @NoParameterNames annotations
>> (or
>> @PublicParameterName directly) to automatically insert the relevant
>> parameter names as part of code-completion. ?Additional refactoring
>> support
>> would also be required to enable parameter names to be renamed, or added
>> and
>> removed completely.
>>
>> Frameworks such as Spring can use the same annotations to allow objects to
>> be created from their configuration files using named parameters to
>> constructors and factory methods. ?Currently they only allow objects to be
>> created from configuration files as JavaBeans (with setter methods) or
>> with
>> ordered (and unnamed) parameters.
>>
>> TESTING:
>>
>> The feature can be tested by compiling and running programs that exercise
>> the feature.
>>
>> LIBRARY SUPPORT:
>>
>> No.
>>
>> REFLECTIVE APIS:
>>
>> java.lang.reflect.Method and java.lang.reflect.Constructor could be
>> enhanced
>> with new methods that return parameter names. ?However, that is not
>> required
>> to successfully implement the proposal.
>>
>> OTHER CHANGES:
>>
>> No. ?The use of named parameters is always optional. ?The javadoc tool
>> already documents parameter names. ?Other tools/libraries might benefit
>> from
>> these changes, but their use is not required.
>>
>> MIGRATION:
>>
>> The @PublicParameterNames annotation (and @NoParameterNames annotation)
>> simply needs to be added to the appropriate methods. ?IDEs could then
>> suggest the use of parameter names for the method's callers, and apply the
>> changes automatically.
>>
>> COMPATIBILITY
>>
>> BREAKING CHANGES:
>>
>> No.
>>
>> EXISTING PROGRAMS:
>>
>> The changes required by this feature should be transparent to existing
>> source and class files if annotations are used internally to describe the
>> named parameters. ?I am not sure what the impact would be otherwise.
>>
>> REFERENCES
>>
>> EXISTING BUGS:
>>
>> 4124331 (though it is set to 11-Closed, Will Not Fix, request for
>> enhancement, and from 1998)
>>
>>
>
>


From howard.lovatt at gmail.com  Mon Apr 20 20:22:51 2009
From: howard.lovatt at gmail.com (howard.lovatt at gmail.com)
Date: Tue, 21 Apr 2009 03:22:51 +0000
Subject: Automatic Resource Management, V.2
Message-ID: <0016364574ac6f02420468082926@google.com>

I have a couple of reservations:

1. The use of try does not seem natural; it is too tied in my mind to  
Exceptions, can another keyword be used?

2. If we are using the specific block approach, eg try (...) {...}, then it  
does not seem natural that for each or similar closes the resource. If the  
approach used automatic closure of a resource at the end of the block that  
the resource was declared in, then for each etc. closing the resource would  
seem natural. I prefer that the resource is automatically closed at the end  
of the block and therefore for each etc. would naturally close at the end  
of their block also; but if the majority thinks a dedicated block structure  
is better, then I suggest that for each etc. are left out.

Having stated my reservations I would rather see the proposal, as is,  
included, rather than nothing at all.

Also thanks to Josh for putting so much effort into this.

-- Howard.


From jjb at google.com  Tue Apr 21 12:44:56 2009
From: jjb at google.com (Joshua Bloch)
Date: Tue, 21 Apr 2009 12:44:56 -0700
Subject: Automatic Resource Management, V.2
In-Reply-To: <0016364574ac6f02420468082926@google.com>
References: <0016364574ac6f02420468082926@google.com>
Message-ID: <17b2302a0904211244h5bf95c6by597996827d4c80e2@mail.gmail.com>

Howard,

On Mon, Apr 20, 2009 at 8:22 PM, <howard.lovatt at gmail.com> wrote:

> I have a couple of reservations:
>
> 1. The use of try does not seem natural; it is too tied in my mind to
> Exceptions,


But there are exceptions involved here!  A main point of the construct is
that it closes resources, even in the presence of exceptions.  I think
that's why others find it so natural.



> can another keyword be used?


There's no technical reason not to, but we have to decide what's best from a
language-design standpoint.


>
>
> 2. If we are using the specific block approach, eg try (...) {...}, then it
> does not seem natural that for each or similar closes the resource. If the
> approach used automatic closure of a resource at the end of the block that
> the resource was declared in, then for each etc. closing the resource would
> seem natural. I prefer that the resource is automatically closed at the end
> of the block and therefore for each etc. would naturally close at the end
> of their block also; but if the majority thinks a dedicated block structure
> is better, then I suggest that for each etc. are left out.


Yeah, this could go either way.


>
> Having stated my reservations I would rather see the proposal, as is,
> included, rather than nothing at all.
>
> Also thanks to Josh for putting so much effort into this.


And thanks so much for your encouragement!

        Josh


From Joe.Darcy at Sun.COM  Tue Apr 21 13:55:26 2009
From: Joe.Darcy at Sun.COM (Joe Darcy)
Date: Tue, 21 Apr 2009 13:55:26 -0700
Subject: Non-proposal: Final Interfaces
In-Reply-To: <212322090904201549h73d23c82t728ef2f4b15a45ac@mail.gmail.com>
References: <212322090904201449u4e19e48apc93722035555a317@mail.gmail.com>
	<212322090904201549h73d23c82t728ef2f4b15a45ac@mail.gmail.com>
Message-ID: <49EE32BE.6060906@sun.com>

Yes, the proposal is out of date for consideration and the modularity 
language features for JSR 294 may support this kind of capability.

-Joe

On 04/20/09 03:49 PM, Paulo Levi wrote:
> Actually the
> "All methods that are deprecated can be deleted on the interface and all
> implementations (since they are controlled completly.)"
>
> Doesn't apply since clients use the methods, but methods can be added
> "(since they are controlled completly.)".
>
> On Mon, Apr 20, 2009 at 10:49 PM, Paulo Levi <i30817 at gmail.com> wrote:
>
>   
>> *I know this is much out of date for consideration, but i think that this
>> is a idea that would really help library evolution, and i did not see any of
>> this kind of strategy floating around in the other proposals.
>> *
>>
>> *
>> *
>>
>> *AUTHOR(S):* Paulo Levi Martins Faria, a student at FCUL, faculdade de
>> ciencias da universidade de lisboa at Lisbon, Portugal.
>>
>> *OVERVIEW*
>>
>> A way for interfaces to be used as references outside a package, but the
>> only implementations of them to exist on a package, to allow the evolution
>> (adding) of methods to interfaces and all their implementations.
>>
>> FEATURE SUMMARY:
>>
>> insted of declaring interfaces as:
>>
>> package xyz;
>>
>> public interface A{
>>
>> } or
>>
>> package xyz;
>>
>> interface A{
>>
>> }
>>
>> declare them as :
>>
>> package xyz;
>>
>> public final interface A{
>>
>> }
>>
>> And all implementations or extensions of A must be in the package xyz
>>
>>
>> MAJOR ADVANTAGE: What makes the proposal a favorable change?
>>
>> This would allow library authors to control the evolution of the
>> implementations of a common interface, deprecating old methods, while at the
>> same time allowing clients to program to the interfaces. The prohibition of
>> implementation/extension outside of package allows the library author to
>> control the package evolution completly. I have personally seen cases where
>> performance reasons lead to dangerous downcasts or using the raw type,
>> and/or subclassing of various classes, to implement something more
>> efficiently than the library core can, because of public interfaces.
>>
>> MAJOR BENEFIT:
>>
>> The jdk can decide if certain interfaces are not likely to be extended
>> outside of the library, and thus control api evolution more completly.
>>
>> All methods that are deprecated can be deleted on the interface and all
>> implementations (since they are controlled completly.)
>>
>> MAJOR DISADVANTAGE:
>>
>> Can not be retrofitted to existing api's (easily).
>>
>> Somewhat overlapping with abstract classes, but more powerfull.
>>
>> Losses flexibility of extension for clients, a risk i am well disposed
>> towards.
>>
>> ALTERNATIVES: Can the benefits and advantages be had some way without a
>> language change?
>>
>> Can think of a way how.
>>
>> *EXAMPLES*
>>
>> Show us the code!
>>
>> SIMPLE EXAMPLE: Show the simplest possible program utilizing the new
>> feature.
>>
>> ADVANCED EXAMPLE: Show advanced usage(s) of the feature.
>>
>> *DETAILS*
>>
>> SPECIFICATION: Describe how the proposal affects the grammar, type system,
>> and meaning of expressions and statements in the Java Programming Language
>> as well as any other known impacts.
>>
>> COMPILATION: How would the feature be compiled to class files? Show how the
>> simple and advanced examples would be compiled. Compilation can be expressed
>> as at least one of a desugaring to existing source constructs and a
>> translation down to bytecode. If a new bytecode is used or the semantics of
>> an existing bytecode are changed, describe those changes, including how they
>> impact verification. Also discuss any new class file attributes that are
>> introduced. Note that there are many downstream tools that consume class
>> files and that they may to be updated to support the proposal!
>>
>> I don't think that this changes compilation beyond the type checj
>>
>> TESTING: How can the feature be tested?
>>
>> Try to implement extend a final interface outside its package.
>>
>> LIBRARY SUPPORT: Are any supporting libraries needed for the feature?
>>
>> No.
>>
>> REFLECTIVE APIS: Do any of the various and sundry reflection APIs need to
>> be updated? This list of reflective APIs includes but is not limited to core
>> reflection (java.lang.Class and java.lang.reflect.*), javax.lang.model.*,
>> the doclet API, and JPDA.
>>
>> Don't think so.
>>
>> OTHER CHANGES: Do any other parts of the platform need be updated too?
>> Possibilities include but are not limited to JNI, serialization, and output
>> of the javadoc tool.
>>
>> No.
>>
>> MIGRATION:
>>
>> Create a new final sub interface to public one on the api, deplicate
>> methods taking that interface to use the new one. Deprecate the old methods
>> and interfaces. Wait for the pichforks.
>>
>> *COMPATIBILITY*
>>
>> BREAKING CHANGES: Are any previously valid programs now invalid? If so,
>> list one.
>>
>> None
>>
>> EXISTING PROGRAMS: How do source and class files of earlier platform
>> versions interact with the feature? Can any new overloadings occur? Can any
>> new overriding occur?
>>
>> No
>>
>> *REFERENCES*
>>
>>
>>     
>
>   



From i30817 at gmail.com  Tue Apr 21 16:40:16 2009
From: i30817 at gmail.com (Paulo Levi)
Date: Wed, 22 Apr 2009 00:40:16 +0100
Subject: Non-proposal: Final Interfaces
In-Reply-To: <49EE32BE.6060906@sun.com>
References: <212322090904201449u4e19e48apc93722035555a317@mail.gmail.com>
	<212322090904201549h73d23c82t728ef2f4b15a45ac@mail.gmail.com>
	<49EE32BE.6060906@sun.com>
Message-ID: <212322090904211640r1e534c57l66dd983d19980548@mail.gmail.com>

On Tue, Apr 21, 2009 at 9:55 PM, Joe Darcy <Joe.Darcy at sun.com> wrote:

>  Yes, the proposal is out of date for consideration and the modularity
> language features for JSR 294 may support this kind of capability.
>
> -Joe
>

How? I've not been following the super packages debate. Notice that unlike
Abstract classes (that can add methods too) this would forbid extensions.
Besides i like that it is the topmost abstraction in the type system that
does this, so reference values can be nicely generic.


From howard.lovatt at gmail.com  Tue Apr 21 17:27:44 2009
From: howard.lovatt at gmail.com (howard.lovatt at gmail.com)
Date: Wed, 22 Apr 2009 00:27:44 +0000
Subject: Automatic Resource Management, V.2
In-Reply-To: <17b2302a0904211244h5bf95c6by597996827d4c80e2@mail.gmail.com>
Message-ID: <0016e64aeb44094311046819d57b@google.com>

Hi Josh,

On Apr 22, 2009 5:44am, Joshua Bloch <jjb at google.com> wrote:

[snip]

> 1. The use of try does not seem natural; it is too tied in my mind to

> Exceptions,
> But there are exceptions involved here! A main point of the construct is  
> that it closes resources,
> even in the presence of exceptions. I think that's why others find it so  
> natural.

None of these decisions are ever easy, if they were we wouldn't be  
discussing them! I can see the exception argument; but on balance I would  
find another approach better, ie either a different keyword or better still  
closing based on variable scope. At the end of the day I find all of these  
three solutions, try, other keyword, or scope, better than what we  
currently have and therefore support any of the variations.

-- Howard.


From howard.lovatt at gmail.com  Tue Apr 21 17:52:59 2009
From: howard.lovatt at gmail.com (howard.lovatt at gmail.com)
Date: Wed, 22 Apr 2009 00:52:59 +0000
Subject: PROPOSAL: Named method parameters
Message-ID: <001636458a864f71e304681a2fb7@google.com>

I use the builder pattern successfully via my enhanced compiler ( pet  
project :) ):

https://pec.dev.java.net/nonav/compile/index.html

and in particular:

https://pec.dev.java.net/nonav/compile/javadoc/pec/compile/immutable/ImmutableValueConversions.html

The enhanced compiler enforces the pattern, ie if you get it wrong the  
compiler gives you an error message.

You can also use a simple structure like class, eg:

class Point {

static class Args {
int x = 0;
int y = 0;
}

final int x;

final iny y;

Point( Args args ) {
x = args.x;
y = args.y;
}

...

}

Which is used like:

Point p = new Point( new Point.Args() {{ x = 1; }} );

As the original post said you would only use this if there were a lot of  
arguments, therefore the overhead of typing "new Point.Args() {{ }}" is  
negligible.

-- Howard.


From brucechapman at paradise.net.nz  Tue Apr 21 19:51:40 2009
From: brucechapman at paradise.net.nz (brucechapman at paradise.net.nz)
Date: Wed, 22 Apr 2009 14:51:40 +1200 (NZST)
Subject: Automatic Resource Management, V.2
In-Reply-To: <ecf3d2390904211024g6802b61dk7ac056391ea3fbef@mail.gmail.com>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<15e8b9d20904210800v762e39a4t5ba75d660780e2@mail.gmail.com>
	<17b2302a0904210834l55f665d9w52613c792989abb0@mail.gmail.com>
	<15e8b9d20904210852t2b8aa5f7n77012ae7397b6eb1@mail.gmail.com>
	<49EDF057.3080906@univ-mlv.fr>
	<15e8b9d20904210948s58366d7as4bcbd1cea653bc6@mail.gmail.com>
	<ecf3d2390904211024g6802b61dk7ac056391ea3fbef@mail.gmail.com>
Message-ID: <1240368700.49ee863cac96e@www.paradise.net.nz>

Quoting Tom Ball <tball at google.com>:

> My "vote" (I realize this isn't a democracy :-) is to avoid adding any
> new
> rules, but instead keep it simple: resources in source code go into all
> tables like any other local variable currently does, while any
> compiler-generated temporary variables get flagged as synthetic and are
> included in any tables that include synthetic variables. In other words,
> a
> resource should be treated exactly like a local variable already is,
> synthetic or not. A resource is a local variable, after all, just one
> that
> has some automatic cleanup as it leaves scope.
> 
> BTW, I like Bruce Chapman's suggestion that the type of a temporary
> variable
> be AutoCloseable. Since the only thing the compiler generated code will
> do
> with that object is call its close() method, there's no advantage to it
> having additional type information.

And I think (despite Josh's explanation for why the source code desugaring can't
be AutoClosable) that the fact that AutoClosable.close() throws Exception
instead of something specific (or nothing), doesn't matter in the class file
format because the compiler will have already dealt with the specific (if any)
possible exceptions on the actual (possible intersection or recursive) type of
the resource expression by either ensuring that they are caught, or declared
thrown in the enclosing method. The only nit here would be if the verifier did
Exception checking and complained that Exception was not caught, but I don't
think that is the case (from a quick browse of the verifier spec, tho I am in NO
WAY AT ALL knowledgable about such things). 

-anyone know for sure??

Bruce

> 
> Tom
> 
> On Tue, Apr 21, 2009 at 9:48 AM, Neal Gafter <neal at gafter.com> wrote:
> 
> > On Tue, Apr 21, 2009 at 9:12 AM, R?mi Forax <forax at univ-mlv.fr>
> wrote:
> >
> > >
> > >> You can probably avoid this mess by being explicit about the
> > specification
> > >> rather than attempting the "as-if" rewriting. If a construct like
> this
> > is
> > >> to be integrated into the JLS that would probably be required
> anyway,
> > and
> > >> a
> > >> new set of issues is likely to be exposed by the attempt. It would
> be
> > >> better to get the specification wrung out earlier rather than later
> (I
> > >> don't
> > >> think Alex will be eager to do it himself).
> > >>
> > >>
> > >>
> > > Why the local var need to be visible in these tables ?
> > >
> > > The compiler already introduced new local var , by example, in case
> of
> > > ++/-- and
> > > compound assignments on boxed type (using the hidden instruction
> > LetExpr).
> > > In that case the local var is flagged SYNTHETIC and doesn't appear
> in
> > local
> > > vars tables.
> >
> >
> > Right: if the specification is spelled out, one can decide on a
> > case-by-case
> > basis how to handle the mapping to the class file. However, you can't
> avoid
> > these variables appearing in the verifier tables at the very least.
> In
> > that
> > case the natural type based on the current spec is its erasure, which
> is
> > not
> > necessarily AutoCloseable.
> >
> >
>  



From markmahieu at googlemail.com  Tue Apr 21 20:44:42 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Wed, 22 Apr 2009 04:44:42 +0100
Subject: Automatic Resource Management, V.2
In-Reply-To: <1240368700.49ee863cac96e@www.paradise.net.nz>
References: <17b2302a0904192345t29997036oc08a81068e7b5829@mail.gmail.com>
	<15e8b9d20904210800v762e39a4t5ba75d660780e2@mail.gmail.com>
	<17b2302a0904210834l55f665d9w52613c792989abb0@mail.gmail.com>
	<15e8b9d20904210852t2b8aa5f7n77012ae7397b6eb1@mail.gmail.com>
	<49EDF057.3080906@univ-mlv.fr>
	<15e8b9d20904210948s58366d7as4bcbd1cea653bc6@mail.gmail.com>
	<ecf3d2390904211024g6802b61dk7ac056391ea3fbef@mail.gmail.com>
	<1240368700.49ee863cac96e@www.paradise.net.nz>
Message-ID: <cf90c1f10904212044y264eb6f8h52f6ef2d789ccb65@mail.gmail.com>

2009/4/22 <brucechapman at paradise.net.nz>
>
> The only nit here would be if the verifier did
> Exception checking and complained that Exception was not caught, but I
> don't
> think that is the case (from a quick browse of the verifier spec, tho I am
> in NO
> WAY AT ALL knowledgable about such things).
>
> -anyone know for sure??
>
> Bruce
>

If I understand you correctly then no, the verifier wouldn't care; checked
exceptions are a language-level feature.

Mark


From brucechapman at paradise.net.nz  Tue Apr 21 20:54:25 2009
From: brucechapman at paradise.net.nz (brucechapman at paradise.net.nz)
Date: Wed, 22 Apr 2009 15:54:25 +1200 (NZST)
Subject: Automatic Resource Management, V.2
In-Reply-To: <0016e64aeb44094311046819d57b@google.com>
References: <0016e64aeb44094311046819d57b@google.com>
Message-ID: <1240372465.49ee94f1976fc@www.paradise.net.nz>

> At the end of the day I find all of
> these 
> three solutions, try, other keyword, or scope, better than what we 
> currently have and therefore support any of the variations.
> 
> -- Howard.
>  

If language design decisions were based on accepting anything that was better
rather than best, then you'd incrementally get way off course, because you
cannot rework previous errors of judgement. As we all know, its hard enough to
keep roughly on course when all practical effort is made to be "best" at each
increment.

It's called entropy and it never decreases, and the more you have, the harder it
is to do more work. The wise thing to do is minimise the entropy of every change
in order to maximise the opportunities for future change.


Bruce


From markmahieu at googlemail.com  Tue Apr 21 21:16:52 2009
From: markmahieu at googlemail.com (Mark Mahieu)
Date: Wed, 22 Apr 2009 05:16:52 +0100
Subject: Automatic Resource Management, V.2
In-Reply-To: <1240372465.49ee94f1976fc@www.paradise.net.nz>
References: <0016e64aeb44094311046819d57b@google.com>
	<1240372465.49ee94f1976fc@www.paradise.net.nz>
Message-ID: <cf90c1f10904212116x5aedc7a4g10d87cd4b740423c@mail.gmail.com>

2009/4/22 <brucechapman at paradise.net.nz>

> > At the end of the day I find all of
> > these
> > three solutions, try, other keyword, or scope, better than what we
> > currently have and therefore support any of the variations.
> >
> > -- Howard.
> >
>
> If language design decisions were based on accepting anything that was
> better
> rather than best, then you'd incrementally get way off course, because you
> cannot rework previous errors of judgement. As we all know, its hard enough
> to
> keep roughly on course when all practical effort is made to be "best" at
> each
> increment.
>
> It's called entropy and it never decreases, and the more you have, the
> harder it
> is to do more work. The wise thing to do is minimise the entropy of every
> change
> in order to maximise the opportunities for future change.
>
>
> Bruce
>
>
Indeed.

There are clearly many factors, but I think much of the debate around ARM
(and some of the other proposals) is interesting to look at from the
perspective of one particular hypothetical question:

"If the aim of Project Coin had been to identify just *one* proposal, but to
then allocate the same resources to it as are currently earmarked for the
entire project (in order to 'do that one thing right', so to speak), would
the proposal still be the same?"

Or, "just how big is this elephant anyway?" ;)

Mark


From Ruslan at Shevchenko.Kiev.UA  Tue Apr 21 21:40:58 2009
From: Ruslan at Shevchenko.Kiev.UA (Ruslan Shevchenko)
Date: Wed, 22 Apr 2009 07:40:58 +0300 (EEST)
Subject: object switch: Re: scripts and results (was Helping to find the 
	usefulness of a      proposal)
In-Reply-To: <49EDEAAC.2040100@gmx.de>
References: <60287e9e1530b3e1ae49976316e8dc57.squirrel@wmail.gradsoft.ua>
	<49E5F020.7060508@gmx.de>
	<114ad93adfd2eb30f7ecd1388b69b1be.squirrel@wmail.gradsoft.ua>
	<49EDEAAC.2040100@gmx.de>
Message-ID: <45f61be4417d9d2c8b24f3a2257c87c6.squirrel@wmail.gradsoft.ua>


>

Hi, Ulf

 You pattern was included in statistics as 'object switch'.

P.S.
  1) Looking now: I forgot add splitting of 'RelationExpression' in it -
this will be added, sorry.

  2) May be you overseen mention of 'object switch' because all switch
patterns (string, instanceof, object) where not in list of patterns, for
which is possible count percentage among simular language constructs.
It's because such pattern change 'if' to 'switch' and I have not idea
how to find simple one-number metric to show effects of such change.

> Hopfully you will find time next days. :-)
>
> Regards,
>
> Ulf
>
>
>




From vapor1 at teleport.com  Tue Apr 21 21:47:06 2009
From: vapor1 at teleport.com (Derek Foster)
Date: Tue, 21 Apr 2009 21:47:06 -0700 (GMT-07:00)
Subject: Proposal: Indexing access syntax for Lists and Maps
Message-ID: <22913460.1240375626476.JavaMail.root@elwamui-karabash.atl.sa.earthlink.net>

I like your idea of including Set as well. I think it makes intuitive sense with regards to a set as a quality of its members. (e.g. the set "blue" has members which are blue, and thus "blue[x]" represents "is x blue?"

However, if we were to do so, I think that "bool foo = (set[y] = bar)" should always result in 'foo' being equal to 'bar', not in it getting the assigned the return value of set.add() or set.remove() as your desugaring implies.

Derek



-----Original Message-----
>From: Tim Keith <tim.keith at gmail.com>
>Sent: Mar 29, 2009 10:40 PM
>To: coin-dev at openjdk.java.net
>Subject: Re: Proposal: Indexing access syntax for Lists and Maps
>
>Is it possible to include Set as well?
>
>E.g.  "bool = set[x]"  meaning  "bool = set.contains(x)"
>and "set[x] = bool"  meaning  "bool ? set.add(x) : set.remove(x)"
>
>-- Tim
>
>On Sun, Mar 29, 2009 at 5:12 PM, Shams Mahmood <shams.mahmood at gmail.com>wrote:
>
>> Indexing access syntax for Lists and Maps
>>
>> VERSION
>> This is version 1.0.
>>
>> AUTHOR(S):
>> Shams Mahmood Imam
>>
>> OVERVIEW
>>
>> FEATURE SUMMARY:
>> Collection classes are among the most frequently used in the Java SDK.
>> Currently Lists and Maps do not provide any additional language
>> feature to access individual elements unlike Arrays. This proposal
>> aims to provide these Collection citizens of java additional
>> language support to access elements like Arrays have currently.
>>
>> MAJOR ADVANTAGE:
>> Will provide a consistent syntax for accessing elements of Arrays,
>> Lists and Maps. In addition, the language grammar will not change
>> much since the subscript operator is already supported for Arrays.
>>
>> MAJOR BENEFIT:
>> Apart from the consistency mentioned above, implementation fo this
>> feature will result in fewer characters needed to be typed to achieve
>> simple access to elements in Maps/Lists.
>>
>> MAJOR DISADVANTAGE:
>> Like the for-each loop construct, it will expose the client to
>> NullPointerException(NPE)s when used with a null List/Map. However,
>> this shouldn't be such a major issue as NPEs are also generated
>> by arrays when the operator is used in a null array.
>>
>> ALTERNATIVES:
>> The comparatively more verbose get/set methods for Lists and get/put
>> methods for Maps.
>>
>> EXAMPLES
>>
>> SIMPLE EXAMPLE:
>>
>> public class Main {
>>  public static void main(String[] arguments) {
>>    List<String> l1 = Arrays.asList(new String[] {"a", "b", "c"});
>>    String firstElement = l1[0];
>>    Map<Integer, String> m1 = new HashMap<Integer, String>(4);
>>    m1[Integer.valueOf(1)] = "One";
>>  }
>> }
>>
>> ADVANCED EXAMPLE:
>>
>> public class Main {
>>  public static void main(String[] arguments) {
>>    List<String> l1 = Arrays.asList(new String[] {"a", "b", "c"});
>>    Map<Integer, String> m1 = new HashMap<Integer, String>(4);
>>    Map<String, Integer> m2 = new HashMap<String, Integer>(4);
>>
>>    m2[l1[2]] = m2[m1[1]] = 4; // same as m2.put(l1.get(2),
>> m2.put(m1.get(1), 4));
>>  }
>> }
>>
>> DETAILS
>>
>> SPECIFICATION:
>> Java Language Specification changes:
>>
>> 15.29 (NEW CHAPTER): Collection Access Expressions
>> A collection access expression contains two subexpressions, the List/Map
>> reference expression (before the left bracket) and the index expression
>> (within the brackets). Note that the List/Map reference expression may be a
>> name or any expression that evaluates to a List/Map. The index experssion is
>> expected to evaluate to an int for Lists and a valid key type for Maps.
>>
>> CollectionAccess:
>>  Expression [ Expression ]
>>
>> 15.8 Primary Expressions
>> original:
>> ---------
>> PrimaryNoNewArray:
>>  Literal
>>  Type . class
>>  void . class
>>  this
>>  ClassName.this
>>  ( Expression )
>>  ClassInstanceCreationExpression
>>  FieldAccess
>>  MethodInvocation
>>  ArrayAccess
>>
>> replaced with:
>> --------------
>> PrimaryNoNewArray:
>>  Literal
>>  Type . class
>>  void . class
>>  this
>>  ClassName.this
>>  ( Expression )
>>  ClassInstanceCreationExpression
>>  FieldAccess
>>  MethodInvocation
>>  ArrayAccess
>>  CollectionAccess
>>
>> 15.26 Assignment Operators
>> original:
>> ---------
>> LeftHandSide:
>>  ExpressionName
>>  FieldAccess
>>  ArrayAccess
>>
>> replaced with:
>> --------------
>> LeftHandSide:
>>  ExpressionName
>>  FieldAccess
>>  ArrayAccess
>>  CollectionAccess
>>
>>
>> COMPILATION:
>>
>> After successful creation of the AST handling the additional grammar for
>> Collection Access expressions, the syntactic sugar will be replaced by
>> JDK1.4 compatible code during the Code Generation phase. This is consistent
>> with how JDK5.0 constructs like the for-each loop is handled by the
>> compiler.
>>
>> e.g.
>> public class TestConcise {
>>  public static void main(String[] args) {
>>    java.util.Map<Integer, String> m1 = new java.util.HashMap<Integer,
>> String>();
>>    m1[2] = "two";
>>
>>    java.util.LinkedList<String> l1 = java.util.Arrays.asList( new String[]
>> {"a", "b", "c" });
>>    m1[3] = l1[2];
>>    l1[0] = m1[0];
>>    l1[1] = "one";
>>  }
>> }
>>
>> is converted to
>> public class TestConcise {
>>  public TestConcise() {
>>    super();
>>  }
>>
>>  public static void main(String[] args) {
>>    java.util.Map<Integer, String> m1 = new java.util.HashMap<Integer,
>> String>();
>>    m1.put(Integer.valueOf(2), "two");
>>
>>    java.util.LinkedList<String> l1 = java.util.Arrays.asList( new String[]
>> {"a", "b", "c" });
>>    m1.put(Integer.valueOf(3), l1.get(2));
>>    l1.set(0, m1.get(Integer.valueOf(0)));
>>    l1.set(1, "one");
>>  }
>> }
>>
>>
>> TESTING:
>>
>> LIBRARY SUPPORT:
>> No additional library support is needed.
>>
>> REFLECTIVE APIS:
>> This proposal does not require any reflective API changes.
>>
>> OTHER CHANGES:
>> No changes required.
>>
>> MIGRATION:
>> No migration is needed.
>>
>> COMPATIBILITY
>>
>> BREAKING CHANGES:
>> No breaking changes.
>>
>> EXISTING PROGRAMS:
>> Existing programs are not affected by this change.
>>
>> REFERENCES
>> My Java7 Wishlist regarding Collections,
>> http://shamsmi.blogspot.com/2008/04/my-java7-wishlist-regarding-collections.html
>> Implementation of My Java7 Wishlist,
>> http://shamsmi.blogspot.com/2008/05/implementation-of-my-java7-wishlist.html
>>
>> EXISTING BUGS:
>> None.
>>
>> URL FOR PROTOTYPE (optional):
>> Projects kijaro's concisecollections branch:
>> https://kijaro.dev.java.net/source/browse/kijaro/branches/concisecollections/
>>
>>
>>
>>
>>
>



From vapor1 at teleport.com  Tue Apr 21 21:55:11 2009
From: vapor1 at teleport.com (Derek Foster)
Date: Tue, 21 Apr 2009 21:55:11 -0700 (GMT-07:00)
Subject: Submission: switch (...) instanceof feature
Message-ID: <11471303.1240376112054.JavaMail.root@elwamui-karabash.atl.sa.earthlink.net>

Like Gabriel, I have severe reservations about this proposal. I am concerned that it will encourage people to avoid the common OOP "best practice" of using virtual method dispatch in favor of doing an explicit "switch" on each subtype of a type, in cases where doing so is not necessary.

I concede that there are a few (FEW!) places where doing the equivalent of a switch on instances of a type is necessary (for instance, if the type is in a library you don't have the ability to change). I can see some value in this proposal for that purpose. However, I would very much not like to see use of this construct become commonplace. I already see too many instances of people doing the equivalent of "if (object.type == FOO) {doThis(); } else if (object.type == BAR) { doThat(); }" instead of writing "object.doSomething();"

Derek

-----Original Message-----
>From: Gabriel Belingueres <belingueres at gmail.com>
>Sent: Mar 30, 2009 7:31 AM
>To: Jeroen van Maanen <jeroen at entreact.com>
>Cc: coin-dev at openjdk.java.net
>Subject: Re: Submission: switch (...) instanceof feature
>
>IMO I'm against this.
>
>First, it is against current best practices for the design of
>object-oriented software to make easier to code something with a case
>statement on types/classes.
>
>Second:
> void log(Object object) {
>   switch (object) instanceof {
>   case String:
>     logger.debug("'" + object + "'");
>   case Date:
>     logger.debug(object.getTime());
>   case void:
>     logger.debug("null");
>   default:
>     logger.debug("<" + object.toString() + ">");
>   }
> }
>
>It think it is clearer (when possible) writing it with several
>overloaded methods and double dispatching.
>
>Third:
>   } catch (Exception exception) {
>     switch (exception.getCause()) instanceof {
>     case ParseException:
>       log.warn("Could not get status for '" + id + ": " +
>exception.getCause());
>     default:
>       log.warn("Could not get status for '" + id + ", exception);
>     }
>}
>
>in the case you intentionally left out the break statement, then the
>switch statement is not any clearer than doing an if.
>in the case that you wanted the break statement on the ParseException
>case, it is even clearer to use two catch blocks (one for
>ParseException and other for Throwable.
>
>
>2009/3/29 Jeroen van Maanen <jeroen at entreact.com>:
>> I'd like to coin a switch (...) instanceof statement as a new feature of the
>> Java language. Please accept the attached proposal for review.
>>
>> Regards, Jeroen
>>
>> PROJECT COIN SMALL LANGUAGE CHANGE PROPOSAL FORM v1.0
>>
>> AUTHOR(S): Jeroen van Maanen <http://lexau.org/contact.html>
>>
>> OVERVIEW
>>
>> FEATURE SUMMARY: The instanceof switch statement allows for clear and
>> concise
>> handling of alternatives that depend on the type of a given object.
>>
>> MAJOR ADVANTAGE: The instanceof switch statement removes the need for
>> different
>> names for the same object with different types and the extra declarations
>> and
>> casts to define those names.
>>
>> MAJOR BENEFIT: Why is the platform better if the proposal is adopted?
>>
>> MAJOR DISADVANTAGE: Coders, reviewers, and IDE's need to be able to read the
>> new statement and interpret and treat it correclty.
>>
>> ALTERNATIVES: There are no alternatives.
>>
>> EXAMPLES
>>
>> SIMPLE EXAMPLE:
>>
>> ?void log(Object object) {
>> ? ?switch (object) instanceof {
>> ? ?case String:
>> ? ? ?logger.debug("'" + object + "'");
>> ? ?case Date:
>> ? ? ?logger.debug(object.getTime());
>> ? ?case void:
>> ? ? ?logger.debug("null");
>> ? ?default:
>> ? ? ?logger.debug("<" + object.toString() + ">");
>> ? ?}
>> ?}
>>
>> ADVANCED EXAMPLE:
>>
>> ?public StatusEnum getStatus(String id) {
>> ? ?StatusEnum result;
>> ? ?try {
>> ? ? ?result = internalGetStatus(id);
>> ? ?} catch (Exception exception) {
>> ? ? ?switch (exception.getCause()) instanceof {
>> ? ? ?case ParseException:
>> ? ? ? ?log.warn("Could not get status for '" + id + ": " +
>> exception.getCause());
>> ? ? ?default:
>> ? ? ? ?log.warn("Could not get status for '" + id + ", exception);
>> ? ? ?}
>> ? ?}
>> ?}
>>
>> public class PrettyPrinter {
>> ?private Writer writer;
>>
>> ?public PrettyPrinter(Writer writer) {
>> ? ?this.writer = writer;
>> ?}
>>
>> ?public write(Object object) {
>> ? ?switch (object) instanceof {
>> ? ? ?case String:
>> ? ? ? ?writer.write(stringDenotation(object));
>> ? ? ?case Collection:
>> ? ? ? ?writer.write(object.getClass().getSimpleName() + ": [");
>> ? ? ? ?for (Object element : object) {
>> ? ? ? ? ?write(element);
>> ? ? ? ? ?writer.write(",");
>> ? ? ? ?}
>> ? ? ? ?writer.write("]");
>> ? ? ?case Map:
>> ? ? ? ?write(object.entrySet());
>> ? ? ?case Map.Entry:
>> ? ? ? ?write(object.getKey());
>> ? ? ? ?writer.write(":");
>> ? ? ? ?write(object.getValue());
>> ? ? ?case void:
>> ? ? ? ?writer.write("null");
>> ? ? ?default:
>> ? ? ? ?// TODO: deal with arrays of unknown base type
>> ? ? ? ?writer.write("<" + object.toString() + ">");
>> ? ?}
>> ?}
>>
>> ?private stringDenotation(String str) {
>> ? ?...
>> ?}
>>
>> }
>>
>> DETAILS
>>
>> SPECIFICATION: The switch instanceof feature adds an alternative to the
>> switch
>> statement to the grammar.
>>
>> ?SwitchStatement:
>> ? ?switch ( Expression ) SwitchBlock
>> ? ?switch ( Identifier ) instanceof TypeSwitchBlock
>>
>> ?TypeSwitchBlock:
>> ? ?{ TypeSwitchBlockStatementGroups? TypeSwitchLabels? }
>>
>> ?TypeSwitchBlockStatementGroups:
>> ? ?TypeSwitchBlockStatementGroup
>> ? ?TypeSwitchBlockStatementGroups TypeSwitchBlockStatementGroup
>>
>> ?TypeSwitchBlockStatementGroup:
>> ? ?TypeSwitchLabel BlockStatements
>>
>> ?TypeSwitchLabel:
>> ? ?case Type :
>> ? ?case void :
>> ? ?default :
>>
>> COMPILATION: The statement
>>
>> ?switch (<<identifier>>) instanceof {
>> ?case <<type1>>:
>> ? ?<<statements1 using identifier>>
>> ?case <<type2>>:
>> ? ?<<statements2>>
>> ?...
>> ?case void:
>> ? ?<<statementsVoid>>
>> ?...
>> ?default:
>> ? ?<<statementsDefault>>
>> ?}
>>
>> Would be compiled by desugaring it to
>>
>> ?if (<<identifier>> instanceof <<type1>>) {
>> ? ?<<type1>> <<identifier + "$1">> = (<<type1>>) <<identifier>>;
>> ? ?<<statements1 with identifier replaced by identifier$1>>
>> ?}
>> ?else if (<<identifier>> instanceof <<type2>>) {
>> ? ?<<type2>> <<identifier + "$2">> = (<<type2>>) <<identifier>>;
>> ? ?<<statements2 with identifier replaced by identifier + "$2">>
>> ?}
>> ?...
>> ?else if (<<identifier>> == null) {
>> ? ?<<statementsVoid>>
>> ?}
>> ?...
>> ?else {
>> ? ?<<statementsDefault>>
>> ?}
>>
>> TESTING: The feature can be tested by compiling and running the examples and
>> comparing the results with the had coded expected desugared versions.
>>
>> LIBRARY SUPPORT: The feature needs no additional library support.
>>
>> REFLECTIVE APIS: The feature does not affect reflective api's.
>>
>> OTHER CHANGES: The feature does not need other changes.
>>
>> MIGRATION: This feature does not invalidate existing code. An existing code
>> base could be scanned for type casts. Occurrences of type casts should be
>> manually evaluated and, if desired, recoded using the new feature.
>>
>> COMPATIBILITY
>>
>> BREAKING CHANGES: This feature does not invalidate existing code.
>>
>> EXISTING PROGRAMS: This feature has no impact on existing code.
>>
>> REFERENCES
>>
>> EXISTING BUGS: There are no existing Sun bug ids related to this proposal.
>>
>> URL FOR PROTOTYPE: Not available.
>>
>>
>>
>>
>



From vapor1 at teleport.com  Tue Apr 21 22:07:23 2009
From: vapor1 at teleport.com (Derek Foster)
Date: Tue, 21 Apr 2009 22:07:23 -0700 (GMT-07:00)
Subject: DISCUSSION: Bean/Data classes
Message-ID: <15002000.1240376843205.JavaMail.root@elwamui-karabash.atl.sa.earthlink.net>

I just wanted to voice some agreement to this sentiment. (And I REALLY want closures, so saying that some form of property support is more important is saying something!). Mostly, I want to never have to write a simple getter again. The are just clutter, and wasted time to maintain. (Setters, I can generally do without, since I prefer immutable classes.) I am amazed that after six revisions of the Java language that we still don't have support for some form of automatic generation of getters for simple properties.

Derek

-----Original Message-----
>From: Stephen Colebourne <scolebourne at joda.org>
>Sent: Mar 25, 2009 3:33 PM
>To: coin-dev at openjdk.java.net
>Subject: DISCUSSION: Bean/Data classes
>
>Finally, I should say that of all the things Java lacks, I think 
>properties is the biggest - bigger than closures. The sheer amount of 
>wasted effort, lines of code, lack of consistency and sheer focus on the 
>low level detail rather than the high level abstraction is staggering. 
>It is IMO a far bigger hole in writing good Java apps today than 
>closures (or any other language proposal).
>
>Stephen




From Ruslan at Shevchenko.Kiev.UA  Tue Apr 21 22:23:22 2009
From: Ruslan at Shevchenko.Kiev.UA (Ruslan Shevchenko)
Date: Wed, 22 Apr 2009 08:23:22 +0300 (EEST)
Subject: PROPOSAL: Enhanced for each loop iteration control
In-Reply-To: <49EDE7B4.2090006@sun.com>
References: <49C56020.2070207@joda.org> <49EDE7B4.2090006@sun.com>
Message-ID: <a59e8c49584f89cce6a89cd28e07dca1.squirrel@wmail.gradsoft.ua>

> Catching up on proposal commenting, while I find the design generally
> acceptable, I remain unconvinced that the inability to replace all
> pre-JDK 5 for loops with some newer, improved for loop is a serious
> enough problem to justify further language changes beyond the enhanced
> for loop in JDK 5.
>
> Some data on how often such a new construct would be applicable would
> help here.
>

 Partially it was RemoveInLoop (which count access to remove within while
operator) in
http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001496.html
Number was quite low (for example 62 in JDK)

I will try to add count for remove-in-for and index-access during next
iteration in my set of coin syntax-patterns. (during next week-end if we
have no time constraints)


> -Joe
>
> Stephen Colebourne wrote:
>> Enhanced for each loop iteration control
>>
>> (re-sent with correct subject line)
>>
>> This proposal extends the for each loop to allow access to meta data
>> including the index and the remove method.
>>
>> (This proposal doesn't really go into enough detail - with JSR-310 my
>> time here is limited. I'd hope that there is just about enough
>> though....)
>>
>> -----------------------------------------------------------------------------------
>> Enhanced for each loop iteration control
>>
>> AUTHOR(S):
>> Stephen Colebourne
>>
>> *OVERVIEW*
>>
>> FEATURE SUMMARY:
>> Extends the Java 5 for-each loop to allow access to the loop index,
>> whether this is the first or last iteration, and to remove the current
>> item.
>>
>> MAJOR ADVANTAGE:
>> The for-each loop is almost certainly the most new popular feature from
>> Java 5. It works because it increases the abstraction level - instead of
>> having to express the low-level details of how to loop around a list or
>> array (with an index or iterator), the developer simply states that they
>> want to loop and the language takes care of the rest. However, all the
>> benefit is lost as soon as the developer needs to access the index or to
>> remove an item.
>>
>> The original Java 5 for each work took a relatively conservative stance
>> on a number of issues aiming to tackle the 80% case. However, loops are
>> such a common form in coding that the remaining 20% that was not tackled
>> represents a significant body of code.
>>
>> The process of converting the loop back from the for each to be index or
>> iterator based is painful. This is because the old loop style if
>> significantly lower-level, more verbose and less clear. It is also
>> painful as most IDEs don't support this kind of 'de-refactoring'.
>>
>> MAJOR BENEFIT:
>> A common coding idiom is expressed at a higher abstraction than at
>> present. This aids readability and clarity.
>>
>> Accessing the index currently requires using an int based loop, or
>> placing a separate int counter outside the loop (which then remains in
>> scope after the loop). The proposed solution doesn't result in manual
>> manipulation of the index.
>>
>> Accessing the iterator remove requires using an iterator based loop.
>> With generics this is remarkably verbose. The proposed solution is
>> significantly shorter and cleaner.
>>
>> MAJOR DISADVANTAGE:
>> The enhanced for each loop is complicated with additional functionality.
>> (This is mitigated by being easy and obvious to use)
>>
>> More code is generated magically by the compiler. (This is mitigated by
>> a simple desugaring)
>>
>> ALTERNATIVES:
>> Use the existing language constructs, typically the standard for loop.
>>
>> Use BGGA/JCA style closures, with control statements. It should be noted
>> that these are consistently the most controversial parts of the closure
>> debate, making the 'let's wait for closures' argument against this
>> proposal weaker (as any final closures implementation may not include
>> control statements).
>>
>>
>> *EXAMPLES*
>>
>> SIMPLE EXAMPLE:
>>
>>     StringBuilder buf = new StringBuilder();
>>     for (String str : list : it) {
>>       if (str == null) {
>>         it.remove();
>>       }
>>     }
>>
>> whereas, today we write:
>>
>>     StringBuilder buf = new StringBuilder();
>>     for (Iterator<String> it = list.iterator(); it.hasNext();) {
>>       String str = it.next();
>>       if (str == null) {
>>         it.remove();
>>       }
>>     }
>>
>> ADVANCED EXAMPLE:
>>
>> Example1:
>>
>>     for (String str : list : it) {
>>       System.out.println("Row " + it.index() + " has the value " + str);
>>     }
>>
>> whereas, today we might write:
>>
>>     int index = 0;
>>     for (String str : list) {
>>       System.out.println("Row " + index + " has the value " + str);
>>       index++;
>>     }
>>
>> or
>>
>>     for (int i = 0; i < list.size(); i++) {
>>       String str = list.get(i);
>>       System.out.println("Row " + index + " has the value " + str);
>>     }
>>
>> Example 2:
>>
>>     StringBuilder buf = new StringBuilder();
>>     for (String str : list : it) {
>>       if (it.isFirst()) {
>>         buf.append(str);
>>       } else {
>>         buf.append(", ").append(str);
>>       }
>>     }
>>
>>     StringBuilder buf = new StringBuilder();
>>     for (String str : list : it) {
>>       if (it.isLast()) {
>>         buf.append(str);
>>       } else {
>>         buf.append(str).append(", ");
>>       }
>>     }
>>
>>
>> *DETAILS*
>>
>> SPECIFICATION:
>>
>> Lexical:
>> No new tokens are added. The colon token is reused in the extended
>> enhanced for each statement.
>>
>> Syntax:
>>
>>    EnhancedForStatement:
>>      for ( VariableModifiersopt Type Identifier : Expression) Statement
>>      for ( VariableModifiersopt Type Identifier : Expression : Ident)
>> Statement
>>
>> Semantics:
>>
>> The first enhanced for each statement (the current form) will compile as
>> it does today.
>>
>> The extended enhanced for each statement will operate as follows.
>> The iterator control variable is a standard variable declared to be
>> final. It will never be null. The type is dependent on whether the
>> expression is an array or an Iterable. It will either be
>> ArrayIterationControl<T> or IterableIterationControl<T>. The type is not
>> specified as it is redundent information, ie. the type is inferred. It
>> is scoped for the life of the loop.
>>
>> public final class IterableIterationControlIterator<T> {
>>     public IterableIterationControlIterator(Iterable<T> iterable) {
>>       this.control = new IterableIterationControl(iterable.iterator());
>>     }
>>     public boolean hasNext() { return control.hasNext() }
>>     public T next() { return control.next() }
>>     public IterableIterationControl<T> control() { return control }
>> }
>> public final class IterableIterationControl<T> {
>>     public IterableIterationControl(Iterator<T> iteratorToWrap) {
>>       this.it = iteratorToWrap;
>>     }
>>     boolean hasNext() { return it.hasNext() }
>>     T next() { originalIndex++; if (lastWasRemoved) { lastWasRemoved =
>> false } else { index++ } return it.next() }
>>     public T remove() { removed++; lastWasRemoved = true; return
>> it.remove() }
>>     public int index() { return index }
>>     public int originalIndex() { return originalIndex }
>>     public boolean isFirst() { return index == 1 }
>>     public boolean isLast() { return it.hasNext() == false }
>> }
>>
>> public final class ArrayIterationControlIterator<T> {
>>     public ArrayIterationControlIterator(T[] array) {
>>       this.control = new ArrayIterationControl(array);
>>     }
>>     public boolean hasNext() { return control.hasNext() }
>>     public T next() { return control.next() }
>>     public ArrayIterationControl<T> control() { return control }
>> }
>> public final class ArrayIterationControl<T> {
>>     public ArrayIterationControl(T[] array) { this.array = array; }
>>     boolean hasNext() { return index < array.length; }
>>     T next() { return array[++index]; }
>>     public int index() { return index - 1; }
>>     public boolean isFirst() { return index == 1; }
>>     public boolean isLast() { return index == array.length; }
>> }
>>
>> Exception analysis:
>> The method remove() on the iteration control variable can throw an
>> UnsuportedOperationException. However, this is no different from any
>> other method call.
>>
>> Definite assignment:
>> The new variable iteration control variable is a final variable that is
>> definitely assigned from creation.
>>
>> COMPILATION:
>> The extended enhanced for each loop is implemented by wrapping the two
>> control classes around the Iterable or the array.
>>
>> The Iterable design is desugared from:
>>
>>     for (T item : iterable : control) { ... }
>>
>> to:
>>     {
>>       IterableIterationControlIterator<T> $it = new
>> IterableIterationControlIterator(iterable);
>>       IterableIterationControl<T> control = $it.control();
>>       while ($it.hasNext()) {
>>         T item = $it.next();
>>         ...
>>       }
>>     }
>>
>> The array design is desugared similarly:
>>
>>     {
>>       ArrayIterationControlIterator<T> $it = new
>> ArrayIterationControlIterator(iterable);
>>       ArrayIterationControl<T> control = $it.control();
>>       while ($it.hasNext()) {
>>         T item = $it.next();
>>         ...
>>       }
>>     }
>>
>> There is the option to optimise this if the iteration control variable
>> is not assigned to any other variable or passed to any other method.
>> However, that is out of scope for now.
>>
>> TESTING:
>> Testing will be similar to the enhanced for loop. Arrays and Iterables
>> of various types and sizes will be used. The null expression will also
>> be tested.
>>
>> LIBRARY SUPPORT:
>> Yes, as detailed above.
>>
>> REFLECTIVE APIS:
>> No.
>>
>> OTHER CHANGES:
>> The javac tree API would need to be updated to model the change.
>>
>> MIGRATION:
>> Migration is not required. However, an IDE refactoring could now convert
>> more int and Iterator based for loops than it does at present.
>>
>>
>> *COMPATIBILITY*
>>
>> BREAKING CHANGES:
>> No breaking changes are known using this conversion scheme.
>>
>> EXISTING PROGRAMS:
>> This conversion is pure syntax sugar, so there are no known interactions
>> with existing programs.
>>
>>
>> *REFERENCES*
>>
>> EXISTING BUGS:
>> I searched the bug database, but nothing came up (which is surprising).
>>
>> URL FOR PROTOTYPE:
>> None
>>
>> DOCUMENTS:
>> [1] Stephen Colebourne's blog:
>> http://www.jroller.com/scolebourne/entry/java_7_for_each_loop
>> [2] Stephen Colebourne's original writeup:
>> http://docs.google.com/Edit?docID=dfn5297z_15ck7x5ghr
>>
>>
>> *DESIGN ISSUES*
>> There are numerous alternative ways in which this feature can be added.
>> These include:
>> - using the keyword:
>>     for (String str : list) {
>>       for.remove();  // problem is nested for loops
>>     }
>> - using a label as a psuedo-variable:
>>     it: for (String str : list) {
>>       it:remove();  // note colon and not dot
>>     }
>> - using an additional clause before the for each colon:
>>     for (String str, int index : list) {
>>       // no access to remove, and conflicts for for each for maps
>>     }
>>
>> The chosen solution involves simple Java classes, and a simple desugar.
>> The downside of the chosen solution is performance, as it involves
>> creating two wrapping objects and routing hasNext() and next() via
>> additional layers of method calls. A possible extension would be for the
>> compiler to identify if the iteration control variable is not passed to
>> another method. If so, then the code could be all be generated inline.
>>
>>
>>
>>
>>
>>
>
>
>




From rssh at gradsoft.com.ua  Tue Apr 21 22:29:35 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Wed, 22 Apr 2009 08:29:35 +0300 (EEST)
Subject: [Fwd: object switch: Re: scripts and results (was Helping to find 
	the      usefulness of a      proposal)]
Message-ID: <a2d878a3dd9c278d951fc0331c88c2c2.squirrel@wmail.gradsoft.ua>

// look's like we have bug in mail-list software: replies from email-
//address other, than given during registrations, sometimes come to
// /dev/null.  So this is second attempt.

>

Hi, Ulf

 You pattern was included in statistics as 'object switch'.

P.S.
  1) Looking now: I forgot add splitting of 'RelationExpression' in it -
this will be added, sorry.

  2) May be you overseen mention of 'object switch' because all switch
patterns (string, instanceof, object) where not in list of patterns, for
which is possible count percentage among simular language constructs.
It's because such pattern change 'if' to 'switch' and I have not idea
how to find simple one-number metric to show effects of such change.

> Hopfully you will find time next days. :-)
>
> Regards,
>
> Ulf
>
>
>





From Ulf.Zibis at gmx.de  Wed Apr 22 02:17:12 2009
From: Ulf.Zibis at gmx.de (Ulf Zibis)
Date: Wed, 22 Apr 2009 11:17:12 +0200
Subject: Submission: switch (...) instanceof feature
In-Reply-To: <11471303.1240376112054.JavaMail.root@elwamui-karabash.atl.sa.earthlink.net>
References: <11471303.1240376112054.JavaMail.root@elwamui-karabash.atl.sa.earthlink.net>
Message-ID: <49EEE098.3050302@gmx.de>

Am 22.04.2009 06:55, Derek Foster schrieb:
> Like Gabriel, I have severe reservations about this proposal. I am concerned that it will encourage people to avoid the common OOP "best practice" of using virtual method dispatch in favor of doing an explicit "switch" on each subtype of a type, in cases where doing so is not necessary.
>
> I concede that there are a few (FEW!) places where doing the equivalent of a switch on instances of a type is necessary (for instance, if the type is in a library you don't have the ability to change). I can see some value in this proposal for that purpose. However, I would very much not like to see use of this construct become commonplace. I already see too many instances of people doing the equivalent of "if (object.type == FOO) {doThis(); } else if (object.type == BAR) { doThat(); }" instead of writing "object.doSomething();"
>
>   

I like to provide an example where

 "object.doSomething();"

  doesn't work:

    synchronized Charset lookup(String lowCanonical) {
        // cache is initialized with available Charset classes names
        Object o = cache.get(lowCanonical);
        // Check cache first
        if (o instanceof String) {
            // Instantiate new charset
            Charset cs = newCharset((String)o, lowCanonical);
            // Cache it
            if (cs != null)
                cache.put(lowCanonical, cs);
            return cs;
        }
        return (Charset)o;
    }


  This would look much nicer, as it avoids casting:

    synchronized Charset lookup(String lowCanonical) {
        // cache is initialized with available Charset classes names
        switch (Object o = cache.get(lowCanonical) instanceof ?) {
            case String :
                // Instantiate new charset
                Charset cs = newCharset(o, lowCanonical);
                // Cache it
                if (cs != null)
                    cache.put(lowCanonical, cs);
                return cs;
            case Charset :
                return o;
        }
    }


Refer:
https://java-nio-charset-enhanced.dev.java.net/source/browse/java-nio-charset-enhanced/tags/milestone4/src/sun/nio/cs/FastCharsetProvider.java?rev=684&view=markup
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6790402
http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001182.html
http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001328.html

- My example could also be smartly coded without switch..case statement, 
if we would enhance if statement accordingly
- I also would like to have possibility to declare variables in if 
clause, like it's possible in for clause:

        if ((Object o = cache.get(lowCanonical)) instanceof String)
            ... ;
        else if (o instanceof Charset)
            ... ; 


-Ulf


> Derek
>
> -----Original Message-----
>   
>> From: Gabriel Belingueres <belingueres at gmail.com>
>> Sent: Mar 30, 2009 7:31 AM
>> To: Jeroen van Maanen <jeroen at entreact.com>
>> Cc: coin-dev at openjdk.java.net
>> Subject: Re: Submission: switch (...) instanceof feature
>>
>> IMO I'm against this.
>>
>> First, it is against current best practices for the design of
>> object-oriented software to make easier to code something with a case
>> statement on types/classes.
>>
>> Second:
>> void log(Object object) {
>>   switch (object) instanceof {
>>   case String:
>>     logger.debug("'" + object + "'");
>>   case Date:
>>     logger.debug(object.getTime());
>>   case void:
>>     logger.debug("null");
>>   default:
>>     logger.debug("<" + object.toString() + ">");
>>   }
>> }
>>
>> It think it is clearer (when possible) writing it with several
>> overloaded methods and double dispatching.
>>
>> ....
>>     



From howard.lovatt at gmail.com  Wed Apr 22 02:54:28 2009
From: howard.lovatt at gmail.com (howard.lovatt at gmail.com)
Date: Wed, 22 Apr 2009 09:54:28 +0000
Subject: Submission: switch (...) instanceof feature
Message-ID: <001636458a86d99996046821bf78@google.com>

Another example would be:

class MyClass {

private int x;

public boolean equals( final Object other ) {
if ( other == null ) { return false; }
switch ( other ) instanceof {
case MyClass: return x == other.x;
}
return false;
}

}

You can also use the construct like case statements in functional  
languages, eg how Scala uses its case classes. If this, switch on  
instanceof, is done for switch it should probably be done for if as well,  
ie:

public boolean equals( final Object other ) {
if ( other == null ) { return false; }
if ( other instanceof MyClass ) { return x == other.x; }
return false;
}

and probably, but might be too hard, on equality tests of class as well as  
instanceof test, eg:

public boolean equals( final Object other ) {
if ( other == null ) { return false; }
if ( other.getClass() == MyClass.class ) { return x == other.x; } //  
equality, rather than instanceof
return false;
}

and:

public boolean equals( final Object other ) {
if ( other == null ) { return false; }
switch ( other.getClass() ) { // equality, rather than instanceof
case MyClass: return x == other.x;
}
return false;
}

These features, as described above, are in the language Nice where it was  
claimed they eliminated the need for casts completely. Eliminating casts  
would be a good result!


From brucechapman at paradise.net.nz  Wed Apr 22 03:04:06 2009
From: brucechapman at paradise.net.nz (Bruce Chapman)
Date: Wed, 22 Apr 2009 22:04:06 +1200
Subject: Syntax patterns: more statistics.
In-Reply-To: <0d48edf00d3533cd9adab8ce7edc7fa6.squirrel@wmail.gradsoft.ua>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904201524q3d1660e8l3d02ef7b07fe29fe@mail.gmail.com>
	<ecf3d2390904201539h493288b8q7a1b8d4d14c2eb48@mail.gmail.com>
	<0d48edf00d3533cd9adab8ce7edc7fa6.squirrel@wmail.gradsoft.ua>
Message-ID: <49EEEB96.2050801@paradise.net.nz>

Ruslan,

I downloaded your tool and read through the documentation but it was not 
obvious to me how to look for my pattern, can I add one more request 
since you seem to be planning another "run" for coin please?

For the "PROPOSAL: Unsigned Integer Widening Operator"  
http://docs.google.com/Doc?id=dcvp3mkv_2k39wt5gf&hl

could you please look for these patterns (bitwise integer and expressions)

$x & 0xff

and

0xFF & $x


where $x is an expression of type byte. (I would expect around 90% or 
more of the matches to be where $x is a byte array access expression, 
and most of the remainder to be byte variables, with most also being 
with the int literal on right hand side. I would not expecting you to 
distinguish 0xff from 255, but the pattern definately ONLY matches when 
anding with this value.

thanks

Bruce


From rssh at gradsoft.com.ua  Wed Apr 22 04:16:43 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Wed, 22 Apr 2009 14:16:43 +0300 (EEST)
Subject: Syntax patterns: more statistics.
In-Reply-To: <49EEEB96.2050801@paradise.net.nz>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904201524q3d1660e8l3d02ef7b07fe29fe@mail.gmail.com>
	<ecf3d2390904201539h493288b8q7a1b8d4d14c2eb48@mail.gmail.com>
	<0d48edf00d3533cd9adab8ce7edc7fa6.squirrel@wmail.gradsoft.ua>
	<49EEEB96.2050801@paradise.net.nz>
Message-ID: <64614c327c243a5dafaf74f4377f63e9.squirrel@wmail.gradsoft.ua>

> Ruslan,
>
> I downloaded your tool and read through the documentation but it was not
> obvious to me how to look for my pattern, can I add one more request
> since you seem to be planning another "run" for coin please?
>

Hi, Bruce.  Will be included in result of next run.

Sorry for providing such 'row' matherial: I will plan to write description
of AST anf Model representation, but this is quite slow process.
For now, too see how language construct is represented in AST or Model the
best way is:
 - write some test java example (in subdirectory testdata)
 - add test to CoinTest (see
http://redmine.gradsoft.ua/repositories/entry/javachecker/trunk/JavaChecker/jtests/ua/gradsoft/javachecker/CoinTest.java),
  call main.setDump(true) and look at test output.





From Ulf.Zibis at gmx.de  Wed Apr 22 04:44:41 2009
From: Ulf.Zibis at gmx.de (Ulf Zibis)
Date: Wed, 22 Apr 2009 13:44:41 +0200
Subject: [Fwd: object switch: Re: scripts and results (was Helping to
	find 	the      usefulness of a      proposal)]
In-Reply-To: <a2d878a3dd9c278d951fc0331c88c2c2.squirrel@wmail.gradsoft.ua>
References: <a2d878a3dd9c278d951fc0331c88c2c2.squirrel@wmail.gradsoft.ua>
Message-ID: <49EF0329.3010604@gmx.de>

Ruslan,

indeed I've overseen your post, as you had changed the subject line. :-(

-Ulf


Am 22.04.2009 07:29, Ruslan Shevchenko schrieb:
>
> Hi, Ulf
>
>  You pattern was included in statistics as 'object switch'.
>
> P.S.
>   1) Looking now: I forgot add splitting of 'RelationExpression' in it -
> this will be added, sorry.
>
>   2) May be you overseen mention of 'object switch' because all switch
> patterns (string, instanceof, object) where not in list of patterns, for
> which is possible count percentage among simular language constructs.
> It's because such pattern change 'if' to 'switch' and I have not idea
> how to find simple one-number metric to show effects of such change.
>
>   



From Ulf.Zibis at gmx.de  Wed Apr 22 05:19:07 2009
From: Ulf.Zibis at gmx.de (Ulf Zibis)
Date: Wed, 22 Apr 2009 14:19:07 +0200
Subject: Syntax patterns: more statistics.
In-Reply-To: <49EEEB96.2050801@paradise.net.nz>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>	<4b4f45e00904201524q3d1660e8l3d02ef7b07fe29fe@mail.gmail.com>	<ecf3d2390904201539h493288b8q7a1b8d4d14c2eb48@mail.gmail.com>	<0d48edf00d3533cd9adab8ce7edc7fa6.squirrel@wmail.gradsoft.ua>
	<49EEEB96.2050801@paradise.net.nz>
Message-ID: <49EF0B3B.2020805@gmx.de>

These cases are just resolved by HotSpot compiler.

See:
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6797305
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6814842
http://mail.openjdk.java.net/pipermail/hotspot-dev/2009-January/001100.html
http://mail.openjdk.java.net/pipermail/hotspot-dev/2009-January/001025.html
http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2009-February/000725.html
http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2009-March/000769.html


-Ulf


Am 22.04.2009 12:04, Bruce Chapman schrieb:
> Ruslan,
>
> I downloaded your tool and read through the documentation but it was not 
> obvious to me how to look for my pattern, can I add one more request 
> since you seem to be planning another "run" for coin please?
>
> For the "PROPOSAL: Unsigned Integer Widening Operator"  
> http://docs.google.com/Doc?id=dcvp3mkv_2k39wt5gf&hl
>
> could you please look for these patterns (bitwise integer and expressions)
>
> $x & 0xff
>
> and
>
> 0xFF & $x
>
>
> where $x is an expression of type byte. (I would expect around 90% or 
> more of the matches to be where $x is a byte array access expression, 
> and most of the remainder to be byte variables, with most also being 
> with the int literal on right hand side. I would not expecting you to 
> distinguish 0xff from 255, but the pattern definately ONLY matches when 
> anding with this value.
>
> thanks
>
> Bruce
>
>
>   



From Ulf.Zibis at gmx.de  Wed Apr 22 05:40:06 2009
From: Ulf.Zibis at gmx.de (Ulf Zibis)
Date: Wed, 22 Apr 2009 14:40:06 +0200
Subject: Syntax patterns: more statistics.
In-Reply-To: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
Message-ID: <49EF1026.4000105@gmx.de>

Am 20.04.2009 16:58, Ruslan Shevchenko schrieb:
> openjdk7 (standard java library)
> all catchs      :       8404
> all ifs :       28494
> all integer literals    :       124356
> big integer literals(undescores)        :       4066
> byte literal    :       1454
> catch in finally        :       103
> elvis   :       877
> instanceof switch       :       318
> loop with remove        :       62
> multi catch     :       411
> object switch   :       1363
> rethrow clause  :       3264
> string in switch        :       445
> Files:9252
>
> Hope, this data will be useful in some cases.
> Regards !
>   

Yes, it definitely is. Great to see the results for "object switch". 3 
times more matches than "string in switch".
This is why I'm against widening switch statement to equals-semantics, see:
http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001328.html

I guess, widening to "expressioned object switch" would increase the 
statistics even more.

Ruslan, thanks for including my proposal.

BTW: Have you also parsed JDK's private sun.* classes? I guess, there 
are plenty of byte literals.

-Ulf




From belingueres at gmail.com  Wed Apr 22 06:39:09 2009
From: belingueres at gmail.com (Gabriel Belingueres)
Date: Wed, 22 Apr 2009 10:39:09 -0300
Subject: Submission: switch (...) instanceof feature
In-Reply-To: <49EEE098.3050302@gmx.de>
References: <11471303.1240376112054.JavaMail.root@elwamui-karabash.atl.sa.earthlink.net>
	<49EEE098.3050302@gmx.de>
Message-ID: <cf66e280904220639n13dc4772gf6eba93657303022@mail.gmail.com>

You may try to get rid of the instanceof by using "another level of
indirection". For example in this case, with a Strategy as the cache
value:

interface ValueStrategy {
  CharSet lookup();
}

class CharSetContentStrategy implements ValueStrategy {
  CharSet value;
  public Charset lookup() {
    ....
  }
}

class StringContentStrategy implements ValueStrategy {
  String value;
  public Charset lookup() {
    ....
  }
}

declare:
final Map<String, ValueStrategy> cache;

then the lookup method would be:

synchronized Charset lookup(String lowCanonical) {
  ValueStrategy v = cache.get(lowCanonical);
  return v.lookup();
}

Please note that in some point the above code may require that you
make an instanceof to know which strategy to create, but this code can
be isolated in a unique method, instead of in many methods as you have
now. (For example, creating a factory class of strategies.)

(Of course, another different question is if this will perform faster
than using instanceof everywhere.)

2009/4/22, Ulf Zibis <Ulf.Zibis at gmx.de>:
> Am 22.04.2009 06:55, Derek Foster schrieb:
> > Like Gabriel, I have severe reservations about this proposal. I am
> concerned that it will encourage people to avoid the common OOP "best
> practice" of using virtual method dispatch in favor of doing an explicit
> "switch" on each subtype of a type, in cases where doing so is not
> necessary.
> >
> > I concede that there are a few (FEW!) places where doing the equivalent of
> a switch on instances of a type is necessary (for instance, if the type is
> in a library you don't have the ability to change). I can see some value in
> this proposal for that purpose. However, I would very much not like to see
> use of this construct become commonplace. I already see too many instances
> of people doing the equivalent of "if (object.type == FOO) {doThis(); } else
> if (object.type == BAR) { doThat(); }" instead of writing
> "object.doSomething();"
> >
> >
> >
>
> I like to provide an example where
>
> "object.doSomething();"
>
>  doesn't work:
>
>   synchronized Charset lookup(String lowCanonical) {
>       // cache is initialized with available Charset classes names
>       Object o = cache.get(lowCanonical);
>       // Check cache first
>       if (o instanceof String) {
>           // Instantiate new charset
>           Charset cs = newCharset((String)o, lowCanonical);
>           // Cache it
>           if (cs != null)
>               cache.put(lowCanonical, cs);
>           return cs;
>       }
>       return (Charset)o;
>   }
>
>
>  This would look much nicer, as it avoids casting:
>
>   synchronized Charset lookup(String lowCanonical) {
>       // cache is initialized with available Charset classes names
>       switch (Object o = cache.get(lowCanonical) instanceof ?) {
>           case String :
>               // Instantiate new charset
>               Charset cs = newCharset(o, lowCanonical);
>               // Cache it
>               if (cs != null)
>                   cache.put(lowCanonical, cs);
>               return cs;
>           case Charset :
>               return o;
>       }
>   }
>
>
> Refer:
> https://java-nio-charset-enhanced.dev.java.net/source/browse/java-nio-charset-enhanced/tags/milestone4/src/sun/nio/cs/FastCharsetProvider.java?rev=684&view=markup
> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6790402
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001182.html
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001328.html
>
> - My example could also be smartly coded without switch..case statement, if
> we would enhance if statement accordingly
> - I also would like to have possibility to declare variables in if clause,
> like it's possible in for clause:
>
>       if ((Object o = cache.get(lowCanonical)) instanceof String)
>           ... ;
>       else if (o instanceof Charset)
>           ... ;
>
> -Ulf
>
>
> > Derek
> >
> > -----Original Message-----
> >
> >
> > > From: Gabriel Belingueres <belingueres at gmail.com>
> > > Sent: Mar 30, 2009 7:31 AM
> > > To: Jeroen van Maanen <jeroen at entreact.com>
> > > Cc: coin-dev at openjdk.java.net
> > > Subject: Re: Submission: switch (...) instanceof feature
> > >
> > > IMO I'm against this.
> > >
> > > First, it is against current best practices for the design of
> > > object-oriented software to make easier to code something with a case
> > > statement on types/classes.
> > >
> > > Second:
> > > void log(Object object) {
> > >  switch (object) instanceof {
> > >  case String:
> > >    logger.debug("'" + object + "'");
> > >  case Date:
> > >    logger.debug(object.getTime());
> > >  case void:
> > >    logger.debug("null");
> > >  default:
> > >    logger.debug("<" + object.toString() + ">");
> > >  }
> > > }
> > >
> > > It think it is clearer (when possible) writing it with several
> > > overloaded methods and double dispatching.
> > >
> > > ....
> > >
> > >
> >
>
>


From rssh at gradsoft.com.ua  Wed Apr 22 07:03:27 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Wed, 22 Apr 2009 17:03:27 +0300 (EEST)
Subject: Syntax patterns: more statistics.
In-Reply-To: <49EF1026.4000105@gmx.de>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<49EF1026.4000105@gmx.de>
Message-ID: <2de340aaf6f07fd7c6ddfda939f1b487.squirrel@wmail.gradsoft.ua>


>
> BTW: Have you also parsed JDK's private sun.* classes? I guess, there
> are plenty of byte literals.
>

 Yes. Most of byte literals are in encoding-handling classes, like
src/share/classes/sun/io/ByteToCharISO2022JP.java

Note, that counter shows not number of byte literals, but number of byte
literals on distinct source lines. (i. e. all byte literals in one line
counted once).


> -Ulf
>
>
>




From Ulf.Zibis at gmx.de  Wed Apr 22 07:07:09 2009
From: Ulf.Zibis at gmx.de (Ulf Zibis)
Date: Wed, 22 Apr 2009 16:07:09 +0200
Subject: Submission: switch (...) instanceof feature
In-Reply-To: <cf66e280904220639n13dc4772gf6eba93657303022@mail.gmail.com>
References: <11471303.1240376112054.JavaMail.root@elwamui-karabash.atl.sa.earthlink.net>	
	<49EEE098.3050302@gmx.de>
	<cf66e280904220639n13dc4772gf6eba93657303022@mail.gmail.com>
Message-ID: <49EF248D.3010904@gmx.de>

Interesting recipe! Thanks.
See my comment below...

Am 22.04.2009 15:39, Gabriel Belingueres schrieb:
> You may try to get rid of the instanceof by using "another level of
> indirection". For example in this case, with a Strategy as the cache
> value:
>
> interface ValueStrategy {
>   CharSet lookup();
> }
>
> class CharSetContentStrategy implements ValueStrategy {
>   CharSet value;
>   public Charset lookup() {
>     ....
>   }
> }
>
> class StringContentStrategy implements ValueStrategy {
>   String value;
>   public Charset lookup() {
>     ....
>   }
> }
>
> declare:
> final Map<String, ValueStrategy> cache;
>
> then the lookup method would be:
>
> synchronized Charset lookup(String lowCanonical) {
>   ValueStrategy v = cache.get(lowCanonical);
>   return v.lookup();
> }
>
> Please note that in some point the above code may require that you
> make an instanceof to know which strategy to create, but this code can
> be isolated in a unique method, instead of in many methods as you have
> now. (For example, creating a factory class of strategies.)
>
> (Of course, another different question is if this will perform faster
> than using instanceof everywhere.)
>
>   

.. another different questions:
- if strategies like this will be reasonable regarding footprint of 
whole application.
- readability of code for externals
- isolating the instanceof code to *additional* unique method will not 
really solve the issue. In my case, the lookup method *is* the unique 
method.

-Ulf




From belingueres at gmail.com  Wed Apr 22 09:06:44 2009
From: belingueres at gmail.com (Gabriel Belingueres)
Date: Wed, 22 Apr 2009 13:06:44 -0300
Subject: Submission: switch (...) instanceof feature
In-Reply-To: <49EF248D.3010904@gmx.de>
References: <11471303.1240376112054.JavaMail.root@elwamui-karabash.atl.sa.earthlink.net>
	<49EEE098.3050302@gmx.de>
	<cf66e280904220639n13dc4772gf6eba93657303022@mail.gmail.com>
	<49EF248D.3010904@gmx.de>
Message-ID: <cf66e280904220906v3e23e618t34a37bd9823f64b0@mail.gmail.com>

> .. another different questions:
> - if strategies like this will be reasonable regarding footprint of whole
> application.

Do you mean memory footprint? You may implement those Strategies as
Singletons if you know they do not store any state, or even as a
Flyweights if the different instances are limited. I would keep it as
simple as possible.

> - readability of code for externals

IMO, readability is not important very important if the application
life cycle will be short. I would apply the KISS principle again.

> - isolating the instanceof code to *additional* unique method will not
> really solve the issue. In my case, the lookup method *is* the unique
> method.

If the lookup method is the only place you do the instanceof test,
then it seems reasonable to keep it that way, instead of creating all
that strategy pattern code.
However, I can not see how changing the instanceof by a switch
statement would improve the code, UNLESS the switch statement adds
some value, for example that it would perform far better than an
if-elseif-else chain AND do some checks, like throwing a compiler
error when I write something like this:

class A {}
class B extends A {}

...
switch(o) instanceof {
case A:
  // do something with this A instance
  break;
case B:
  // never enter this branch if it's a B because it is always catched by the
  // previous case
  break;
...
}


From Ulf.Zibis at gmx.de  Wed Apr 22 09:27:10 2009
From: Ulf.Zibis at gmx.de (Ulf Zibis)
Date: Wed, 22 Apr 2009 18:27:10 +0200
Subject: Submission: switch (...) instanceof feature
In-Reply-To: <cf66e280904220906v3e23e618t34a37bd9823f64b0@mail.gmail.com>
References: <11471303.1240376112054.JavaMail.root@elwamui-karabash.atl.sa.earthlink.net>	
	<49EEE098.3050302@gmx.de>	
	<cf66e280904220639n13dc4772gf6eba93657303022@mail.gmail.com>	
	<49EF248D.3010904@gmx.de>
	<cf66e280904220906v3e23e618t34a37bd9823f64b0@mail.gmail.com>
Message-ID: <49EF455E.9060507@gmx.de>



Am 22.04.2009 18:06, Gabriel Belingueres schrieb:
>
> Do you mean memory footprint? You may implement those Strategies as
> Singletons if you know they do not store any state, or even as a
> Flyweights if the different instances are limited. I would keep it as
> simple as possible.
>   

1st I mean jar-footprint, but 2nd I also mean memory footprint and not 
to forget class loading, object initialization and indirection time.

>
> IMO, readability is not important very important if the application
> life cycle will be short. I would apply the KISS principle again.
>   

Do you think, sun.nio.cs.FastCharsetProvider is kind of short life cycle 
? ;-)

>
> If the lookup method is the only place you do the instanceof test,
> then it seems reasonable to keep it that way, instead of creating all
> that strategy pattern code.
> However, I can not see how changing the instanceof by a switch
> statement would improve the code,

Think about READABILITY, READABILITY and READABILITY.

if..else is good for 2-way fork, but IMHO switch..case is better for 
n-way fork.
See: http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001182.html

In case of instanceof additionally casting could be omitted.

>  UNLESS the switch statement adds
> some value, for example that it would perform far better than an
> if-elseif-else chain AND do some checks, like throwing a compiler
> error when I write something like this:
>   

+1

> class A {}
> class B extends A {}
>
> ...
> switch(o) instanceof {
> case A:
>   // do something with this A instance
>   break;
> case B:
>   // never enter this branch if it's a B because it is always catched by the
>   // previous case
>   break;
> ...
> }
>
>
>   



From tball at google.com  Wed Apr 22 09:36:45 2009
From: tball at google.com (Tom Ball)
Date: Wed, 22 Apr 2009 09:36:45 -0700
Subject: Submission: switch (...) instanceof feature
In-Reply-To: <11471303.1240376112054.JavaMail.root@elwamui-karabash.atl.sa.earthlink.net>
References: <11471303.1240376112054.JavaMail.root@elwamui-karabash.atl.sa.earthlink.net>
Message-ID: <ecf3d2390904220936n65c448cfh14386e292fe8b377@mail.gmail.com>

In general I agree with your concern, but remember that those of us on this
alias have the ability to modify most of the code we use.  That's not true
in the Java community at large, where using existing code, such as
frameworks or libraries, is much more prevalent.  It's often not practical
to "write object.doSomething()" when working with external code, and that's
where this proposal helps.

Tom

On Tue, Apr 21, 2009 at 9:55 PM, Derek Foster <vapor1 at teleport.com> wrote:

> Like Gabriel, I have severe reservations about this proposal. I am
> concerned that it will encourage people to avoid the common OOP "best
> practice" of using virtual method dispatch in favor of doing an explicit
> "switch" on each subtype of a type, in cases where doing so is not
> necessary.
>
> I concede that there are a few (FEW!) places where doing the equivalent of
> a switch on instances of a type is necessary (for instance, if the type is
> in a library you don't have the ability to change). I can see some value in
> this proposal for that purpose. However, I would very much not like to see
> use of this construct become commonplace. I already see too many instances
> of people doing the equivalent of "if (object.type == FOO) {doThis(); } else
> if (object.type == BAR) { doThat(); }" instead of writing
> "object.doSomething();"
>
> Derek
>
> -----Original Message-----
> >From: Gabriel Belingueres <belingueres at gmail.com>
> >Sent: Mar 30, 2009 7:31 AM
> >To: Jeroen van Maanen <jeroen at entreact.com>
> >Cc: coin-dev at openjdk.java.net
> >Subject: Re: Submission: switch (...) instanceof feature
> >
> >IMO I'm against this.
> >
> >First, it is against current best practices for the design of
> >object-oriented software to make easier to code something with a case
> >statement on types/classes.
> >
> >Second:
> > void log(Object object) {
> >   switch (object) instanceof {
> >   case String:
> >     logger.debug("'" + object + "'");
> >   case Date:
> >     logger.debug(object.getTime());
> >   case void:
> >     logger.debug("null");
> >   default:
> >     logger.debug("<" + object.toString() + ">");
> >   }
> > }
> >
> >It think it is clearer (when possible) writing it with several
> >overloaded methods and double dispatching.
> >
> >Third:
> >   } catch (Exception exception) {
> >     switch (exception.getCause()) instanceof {
> >     case ParseException:
> >       log.warn("Could not get status for '" + id + ": " +
> >exception.getCause());
> >     default:
> >       log.warn("Could not get status for '" + id + ", exception);
> >     }
> >}
> >
> >in the case you intentionally left out the break statement, then the
> >switch statement is not any clearer than doing an if.
> >in the case that you wanted the break statement on the ParseException
> >case, it is even clearer to use two catch blocks (one for
> >ParseException and other for Throwable.
> >
> >
> >2009/3/29 Jeroen van Maanen <jeroen at entreact.com>:
> >> I'd like to coin a switch (...) instanceof statement as a new feature of
> the
> >> Java language. Please accept the attached proposal for review.
> >>
> >> Regards, Jeroen
> >>
> >> PROJECT COIN SMALL LANGUAGE CHANGE PROPOSAL FORM v1.0
> >>
> >> AUTHOR(S): Jeroen van Maanen <http://lexau.org/contact.html>
> >>
> >> OVERVIEW
> >>
> >> FEATURE SUMMARY: The instanceof switch statement allows for clear and
> >> concise
> >> handling of alternatives that depend on the type of a given object.
> >>
> >> MAJOR ADVANTAGE: The instanceof switch statement removes the need for
> >> different
> >> names for the same object with different types and the extra
> declarations
> >> and
> >> casts to define those names.
> >>
> >> MAJOR BENEFIT: Why is the platform better if the proposal is adopted?
> >>
> >> MAJOR DISADVANTAGE: Coders, reviewers, and IDE's need to be able to read
> the
> >> new statement and interpret and treat it correclty.
> >>
> >> ALTERNATIVES: There are no alternatives.
> >>
> >> EXAMPLES
> >>
> >> SIMPLE EXAMPLE:
> >>
> >>  void log(Object object) {
> >>    switch (object) instanceof {
> >>    case String:
> >>      logger.debug("'" + object + "'");
> >>    case Date:
> >>      logger.debug(object.getTime());
> >>    case void:
> >>      logger.debug("null");
> >>    default:
> >>      logger.debug("<" + object.toString() + ">");
> >>    }
> >>  }
> >>
> >> ADVANCED EXAMPLE:
> >>
> >>  public StatusEnum getStatus(String id) {
> >>    StatusEnum result;
> >>    try {
> >>      result = internalGetStatus(id);
> >>    } catch (Exception exception) {
> >>      switch (exception.getCause()) instanceof {
> >>      case ParseException:
> >>        log.warn("Could not get status for '" + id + ": " +
> >> exception.getCause());
> >>      default:
> >>        log.warn("Could not get status for '" + id + ", exception);
> >>      }
> >>    }
> >>  }
> >>
> >> public class PrettyPrinter {
> >>  private Writer writer;
> >>
> >>  public PrettyPrinter(Writer writer) {
> >>    this.writer = writer;
> >>  }
> >>
> >>  public write(Object object) {
> >>    switch (object) instanceof {
> >>      case String:
> >>        writer.write(stringDenotation(object));
> >>      case Collection:
> >>        writer.write(object.getClass().getSimpleName() + ": [");
> >>        for (Object element : object) {
> >>          write(element);
> >>          writer.write(",");
> >>        }
> >>        writer.write("]");
> >>      case Map:
> >>        write(object.entrySet());
> >>      case Map.Entry:
> >>        write(object.getKey());
> >>        writer.write(":");
> >>        write(object.getValue());
> >>      case void:
> >>        writer.write("null");
> >>      default:
> >>        // TODO: deal with arrays of unknown base type
> >>        writer.write("<" + object.toString() + ">");
> >>    }
> >>  }
> >>
> >>  private stringDenotation(String str) {
> >>    ...
> >>  }
> >>
> >> }
> >>
> >> DETAILS
> >>
> >> SPECIFICATION: The switch instanceof feature adds an alternative to the
> >> switch
> >> statement to the grammar.
> >>
> >>  SwitchStatement:
> >>    switch ( Expression ) SwitchBlock
> >>    switch ( Identifier ) instanceof TypeSwitchBlock
> >>
> >>  TypeSwitchBlock:
> >>    { TypeSwitchBlockStatementGroups? TypeSwitchLabels? }
> >>
> >>  TypeSwitchBlockStatementGroups:
> >>    TypeSwitchBlockStatementGroup
> >>    TypeSwitchBlockStatementGroups TypeSwitchBlockStatementGroup
> >>
> >>  TypeSwitchBlockStatementGroup:
> >>    TypeSwitchLabel BlockStatements
> >>
> >>  TypeSwitchLabel:
> >>    case Type :
> >>    case void :
> >>    default :
> >>
> >> COMPILATION: The statement
> >>
> >>  switch (<<identifier>>) instanceof {
> >>  case <<type1>>:
> >>    <<statements1 using identifier>>
> >>  case <<type2>>:
> >>    <<statements2>>
> >>  ...
> >>  case void:
> >>    <<statementsVoid>>
> >>  ...
> >>  default:
> >>    <<statementsDefault>>
> >>  }
> >>
> >> Would be compiled by desugaring it to
> >>
> >>  if (<<identifier>> instanceof <<type1>>) {
> >>    <<type1>> <<identifier + "$1">> = (<<type1>>) <<identifier>>;
> >>    <<statements1 with identifier replaced by identifier$1>>
> >>  }
> >>  else if (<<identifier>> instanceof <<type2>>) {
> >>    <<type2>> <<identifier + "$2">> = (<<type2>>) <<identifier>>;
> >>    <<statements2 with identifier replaced by identifier + "$2">>
> >>  }
> >>  ...
> >>  else if (<<identifier>> == null) {
> >>    <<statementsVoid>>
> >>  }
> >>  ...
> >>  else {
> >>    <<statementsDefault>>
> >>  }
> >>
> >> TESTING: The feature can be tested by compiling and running the examples
> and
> >> comparing the results with the had coded expected desugared versions.
> >>
> >> LIBRARY SUPPORT: The feature needs no additional library support.
> >>
> >> REFLECTIVE APIS: The feature does not affect reflective api's.
> >>
> >> OTHER CHANGES: The feature does not need other changes.
> >>
> >> MIGRATION: This feature does not invalidate existing code. An existing
> code
> >> base could be scanned for type casts. Occurrences of type casts should
> be
> >> manually evaluated and, if desired, recoded using the new feature.
> >>
> >> COMPATIBILITY
> >>
> >> BREAKING CHANGES: This feature does not invalidate existing code.
> >>
> >> EXISTING PROGRAMS: This feature has no impact on existing code.
> >>
> >> REFERENCES
> >>
> >> EXISTING BUGS: There are no existing Sun bug ids related to this
> proposal.
> >>
> >> URL FOR PROTOTYPE: Not available.
> >>
> >>
> >>
> >>
> >
>
>
>


From reinier at zwitserloot.com  Wed Apr 22 16:57:00 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Thu, 23 Apr 2009 01:57:00 +0200
Subject: Proposal: Indexing access syntax for Lists and Maps
In-Reply-To: <22913460.1240375626476.JavaMail.root@elwamui-karabash.atl.sa.earthlink.net>
References: <22913460.1240375626476.JavaMail.root@elwamui-karabash.atl.sa.earthlink.net>
Message-ID: <C5DF171B-4290-4069-A9A9-CFBDB3398718@zwitserloot.com>

Letting 'foo[x]', where foo is a set, have the asribed specification  
is exactly the kind of circus trick I expect some well-intended bad  
library to use, in languages that support operator overloading.

Hard-coding it into the JLS: Please, don't do that.

Here's the golden rule for doing ANYTHING at all with operators:

If it's not crystal clear for everybody who is going to read your  
code, then, don't do it. Also,

someList[10] = true;

someMap[10] = true;

someSet[10] = true;

would all have entirely different meanings. Overloading [] for lists  
and maps is an acceptable evil because people in general are quite  
used to it (e.g. due to javascript, python, and many other languages).



This list is certainly reinforcing the idea that operator overloading  
accessible to library builders is a bad idea.


  --Reinier Zwitserloot
Like it? Tip it!
http://tipit.to



On Apr 22, 2009, at 06:47, Derek Foster wrote:

> I like your idea of including Set as well. I think it makes  
> intuitive sense with regards to a set as a quality of its members.  
> (e.g. the set "blue" has members which are blue, and thus "blue[x]"  
> represents "is x blue?"
>
> However, if we were to do so, I think that "bool foo = (set[y] =  
> bar)" should always result in 'foo' being equal to 'bar', not in it  
> getting the assigned the return value of set.add() or set.remove()  
> as your desugaring implies.
>
> Derek
>
>
>
> -----Original Message-----
>> From: Tim Keith <tim.keith at gmail.com>
>> Sent: Mar 29, 2009 10:40 PM
>> To: coin-dev at openjdk.java.net
>> Subject: Re: Proposal: Indexing access syntax for Lists and Maps
>>
>> Is it possible to include Set as well?
>>
>> E.g.  "bool = set[x]"  meaning  "bool = set.contains(x)"
>> and "set[x] = bool"  meaning  "bool ? set.add(x) : set.remove(x)"
>>
>> -- Tim
>>
>> On Sun, Mar 29, 2009 at 5:12 PM, Shams Mahmood <shams.mahmood at gmail.com 
>> >wrote:
>>
>>> Indexing access syntax for Lists and Maps
>>>
>>> VERSION
>>> This is version 1.0.
>>>
>>> AUTHOR(S):
>>> Shams Mahmood Imam
>>>
>>> OVERVIEW
>>>
>>> FEATURE SUMMARY:
>>> Collection classes are among the most frequently used in the Java  
>>> SDK.
>>> Currently Lists and Maps do not provide any additional language
>>> feature to access individual elements unlike Arrays. This proposal
>>> aims to provide these Collection citizens of java additional
>>> language support to access elements like Arrays have currently.
>>>
>>> MAJOR ADVANTAGE:
>>> Will provide a consistent syntax for accessing elements of Arrays,
>>> Lists and Maps. In addition, the language grammar will not change
>>> much since the subscript operator is already supported for Arrays.
>>>
>>> MAJOR BENEFIT:
>>> Apart from the consistency mentioned above, implementation fo this
>>> feature will result in fewer characters needed to be typed to  
>>> achieve
>>> simple access to elements in Maps/Lists.
>>>
>>> MAJOR DISADVANTAGE:
>>> Like the for-each loop construct, it will expose the client to
>>> NullPointerException(NPE)s when used with a null List/Map. However,
>>> this shouldn't be such a major issue as NPEs are also generated
>>> by arrays when the operator is used in a null array.
>>>
>>> ALTERNATIVES:
>>> The comparatively more verbose get/set methods for Lists and get/put
>>> methods for Maps.
>>>
>>> EXAMPLES
>>>
>>> SIMPLE EXAMPLE:
>>>
>>> public class Main {
>>> public static void main(String[] arguments) {
>>>   List<String> l1 = Arrays.asList(new String[] {"a", "b", "c"});
>>>   String firstElement = l1[0];
>>>   Map<Integer, String> m1 = new HashMap<Integer, String>(4);
>>>   m1[Integer.valueOf(1)] = "One";
>>> }
>>> }
>>>
>>> ADVANCED EXAMPLE:
>>>
>>> public class Main {
>>> public static void main(String[] arguments) {
>>>   List<String> l1 = Arrays.asList(new String[] {"a", "b", "c"});
>>>   Map<Integer, String> m1 = new HashMap<Integer, String>(4);
>>>   Map<String, Integer> m2 = new HashMap<String, Integer>(4);
>>>
>>>   m2[l1[2]] = m2[m1[1]] = 4; // same as m2.put(l1.get(2),
>>> m2.put(m1.get(1), 4));
>>> }
>>> }
>>>
>>> DETAILS
>>>
>>> SPECIFICATION:
>>> Java Language Specification changes:
>>>
>>> 15.29 (NEW CHAPTER): Collection Access Expressions
>>> A collection access expression contains two subexpressions, the  
>>> List/Map
>>> reference expression (before the left bracket) and the index  
>>> expression
>>> (within the brackets). Note that the List/Map reference expression  
>>> may be a
>>> name or any expression that evaluates to a List/Map. The index  
>>> experssion is
>>> expected to evaluate to an int for Lists and a valid key type for  
>>> Maps.
>>>
>>> CollectionAccess:
>>> Expression [ Expression ]
>>>
>>> 15.8 Primary Expressions
>>> original:
>>> ---------
>>> PrimaryNoNewArray:
>>> Literal
>>> Type . class
>>> void . class
>>> this
>>> ClassName.this
>>> ( Expression )
>>> ClassInstanceCreationExpression
>>> FieldAccess
>>> MethodInvocation
>>> ArrayAccess
>>>
>>> replaced with:
>>> --------------
>>> PrimaryNoNewArray:
>>> Literal
>>> Type . class
>>> void . class
>>> this
>>> ClassName.this
>>> ( Expression )
>>> ClassInstanceCreationExpression
>>> FieldAccess
>>> MethodInvocation
>>> ArrayAccess
>>> CollectionAccess
>>>
>>> 15.26 Assignment Operators
>>> original:
>>> ---------
>>> LeftHandSide:
>>> ExpressionName
>>> FieldAccess
>>> ArrayAccess
>>>
>>> replaced with:
>>> --------------
>>> LeftHandSide:
>>> ExpressionName
>>> FieldAccess
>>> ArrayAccess
>>> CollectionAccess
>>>
>>>
>>> COMPILATION:
>>>
>>> After successful creation of the AST handling the additional  
>>> grammar for
>>> Collection Access expressions, the syntactic sugar will be  
>>> replaced by
>>> JDK1.4 compatible code during the Code Generation phase. This is  
>>> consistent
>>> with how JDK5.0 constructs like the for-each loop is handled by the
>>> compiler.
>>>
>>> e.g.
>>> public class TestConcise {
>>> public static void main(String[] args) {
>>>   java.util.Map<Integer, String> m1 = new java.util.HashMap<Integer,
>>> String>();
>>>   m1[2] = "two";
>>>
>>>   java.util.LinkedList<String> l1 = java.util.Arrays.asList( new  
>>> String[]
>>> {"a", "b", "c" });
>>>   m1[3] = l1[2];
>>>   l1[0] = m1[0];
>>>   l1[1] = "one";
>>> }
>>> }
>>>
>>> is converted to
>>> public class TestConcise {
>>> public TestConcise() {
>>>   super();
>>> }
>>>
>>> public static void main(String[] args) {
>>>   java.util.Map<Integer, String> m1 = new java.util.HashMap<Integer,
>>> String>();
>>>   m1.put(Integer.valueOf(2), "two");
>>>
>>>   java.util.LinkedList<String> l1 = java.util.Arrays.asList( new  
>>> String[]
>>> {"a", "b", "c" });
>>>   m1.put(Integer.valueOf(3), l1.get(2));
>>>   l1.set(0, m1.get(Integer.valueOf(0)));
>>>   l1.set(1, "one");
>>> }
>>> }
>>>
>>>
>>> TESTING:
>>>
>>> LIBRARY SUPPORT:
>>> No additional library support is needed.
>>>
>>> REFLECTIVE APIS:
>>> This proposal does not require any reflective API changes.
>>>
>>> OTHER CHANGES:
>>> No changes required.
>>>
>>> MIGRATION:
>>> No migration is needed.
>>>
>>> COMPATIBILITY
>>>
>>> BREAKING CHANGES:
>>> No breaking changes.
>>>
>>> EXISTING PROGRAMS:
>>> Existing programs are not affected by this change.
>>>
>>> REFERENCES
>>> My Java7 Wishlist regarding Collections,
>>> http://shamsmi.blogspot.com/2008/04/my-java7-wishlist-regarding-collections.html
>>> Implementation of My Java7 Wishlist,
>>> http://shamsmi.blogspot.com/2008/05/implementation-of-my-java7-wishlist.html
>>>
>>> EXISTING BUGS:
>>> None.
>>>
>>> URL FOR PROTOTYPE (optional):
>>> Projects kijaro's concisecollections branch:
>>> https://kijaro.dev.java.net/source/browse/kijaro/branches/concisecollections/
>>>
>>>
>>>
>>>
>>>
>>
>
>



From reinier at zwitserloot.com  Wed Apr 22 16:58:07 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Thu, 23 Apr 2009 01:58:07 +0200
Subject: PROPOSAL: Enhanced for each loop iteration control
In-Reply-To: <49EDE7B4.2090006@sun.com>
References: <49C56020.2070207@joda.org> <49EDE7B4.2090006@sun.com>
Message-ID: <3BBAA5CF-247E-430F-A271-A10C79642FF7@zwitserloot.com>

If the proposal was just about making the iterator available, I'd  
agree with you, but the proposal adds methods like .first(), which  
are /very/ useful indeed. It's right up there with ARM, and easily  
beats string switching, in how applicable that would be.

Adding a .join() method to String or List (depending on taste) would  
solve over half of the use-cases for the extended forloop, though.

  --Reinier Zwitserloot
Like it? Tip it!
http://tipit.to



On Apr 21, 2009, at 17:35, Joseph D. Darcy wrote:

> Catching up on proposal commenting, while I find the design generally
> acceptable, I remain unconvinced that the inability to replace all
> pre-JDK 5 for loops with some newer, improved for loop is a serious
> enough problem to justify further language changes beyond the enhanced
> for loop in JDK 5.
>
> Some data on how often such a new construct would be applicable would
> help here.
>
> -Joe
>
> Stephen Colebourne wrote:
>> Enhanced for each loop iteration control
>>
>> (re-sent with correct subject line)
>>
>> This proposal extends the for each loop to allow access to meta data
>> including the index and the remove method.
>>
>> (This proposal doesn't really go into enough detail - with JSR-310 my
>> time here is limited. I'd hope that there is just about enough  
>> though....)
>>
>> -----------------------------------------------------------------------------------
>> Enhanced for each loop iteration control
>>
>> AUTHOR(S):
>> Stephen Colebourne
>>
>> *OVERVIEW*
>>
>> FEATURE SUMMARY:
>> Extends the Java 5 for-each loop to allow access to the loop index,
>> whether this is the first or last iteration, and to remove the  
>> current item.
>>
>> MAJOR ADVANTAGE:
>> The for-each loop is almost certainly the most new popular feature  
>> from
>> Java 5. It works because it increases the abstraction level -  
>> instead of
>> having to express the low-level details of how to loop around a  
>> list or
>> array (with an index or iterator), the developer simply states that  
>> they
>> want to loop and the language takes care of the rest. However, all  
>> the
>> benefit is lost as soon as the developer needs to access the index  
>> or to
>> remove an item.
>>
>> The original Java 5 for each work took a relatively conservative  
>> stance
>> on a number of issues aiming to tackle the 80% case. However, loops  
>> are
>> such a common form in coding that the remaining 20% that was not  
>> tackled
>> represents a significant body of code.
>>
>> The process of converting the loop back from the for each to be  
>> index or
>> iterator based is painful. This is because the old loop style if
>> significantly lower-level, more verbose and less clear. It is also
>> painful as most IDEs don't support this kind of 'de-refactoring'.
>>
>> MAJOR BENEFIT:
>> A common coding idiom is expressed at a higher abstraction than at
>> present. This aids readability and clarity.
>>
>> Accessing the index currently requires using an int based loop, or
>> placing a separate int counter outside the loop (which then remains  
>> in
>> scope after the loop). The proposed solution doesn't result in manual
>> manipulation of the index.
>>
>> Accessing the iterator remove requires using an iterator based loop.
>> With generics this is remarkably verbose. The proposed solution is
>> significantly shorter and cleaner.
>>
>> MAJOR DISADVANTAGE:
>> The enhanced for each loop is complicated with additional  
>> functionality.
>> (This is mitigated by being easy and obvious to use)
>>
>> More code is generated magically by the compiler. (This is  
>> mitigated by
>> a simple desugaring)
>>
>> ALTERNATIVES:
>> Use the existing language constructs, typically the standard for  
>> loop.
>>
>> Use BGGA/JCA style closures, with control statements. It should be  
>> noted
>> that these are consistently the most controversial parts of the  
>> closure
>> debate, making the 'let's wait for closures' argument against this
>> proposal weaker (as any final closures implementation may not include
>> control statements).
>>
>>
>> *EXAMPLES*
>>
>> SIMPLE EXAMPLE:
>>
>>    StringBuilder buf = new StringBuilder();
>>    for (String str : list : it) {
>>      if (str == null) {
>>        it.remove();
>>      }
>>    }
>>
>> whereas, today we write:
>>
>>    StringBuilder buf = new StringBuilder();
>>    for (Iterator<String> it = list.iterator(); it.hasNext();) {
>>      String str = it.next();
>>      if (str == null) {
>>        it.remove();
>>      }
>>    }
>>
>> ADVANCED EXAMPLE:
>>
>> Example1:
>>
>>    for (String str : list : it) {
>>      System.out.println("Row " + it.index() + " has the value " +  
>> str);
>>    }
>>
>> whereas, today we might write:
>>
>>    int index = 0;
>>    for (String str : list) {
>>      System.out.println("Row " + index + " has the value " + str);
>>      index++;
>>    }
>>
>> or
>>
>>    for (int i = 0; i < list.size(); i++) {
>>      String str = list.get(i);
>>      System.out.println("Row " + index + " has the value " + str);
>>    }
>>
>> Example 2:
>>
>>    StringBuilder buf = new StringBuilder();
>>    for (String str : list : it) {
>>      if (it.isFirst()) {
>>        buf.append(str);
>>      } else {
>>        buf.append(", ").append(str);
>>      }
>>    }
>>
>>    StringBuilder buf = new StringBuilder();
>>    for (String str : list : it) {
>>      if (it.isLast()) {
>>        buf.append(str);
>>      } else {
>>        buf.append(str).append(", ");
>>      }
>>    }
>>
>>
>> *DETAILS*
>>
>> SPECIFICATION:
>>
>> Lexical:
>> No new tokens are added. The colon token is reused in the extended
>> enhanced for each statement.
>>
>> Syntax:
>>
>>   EnhancedForStatement:
>>     for ( VariableModifiersopt Type Identifier : Expression)  
>> Statement
>>     for ( VariableModifiersopt Type Identifier : Expression : Ident)
>> Statement
>>
>> Semantics:
>>
>> The first enhanced for each statement (the current form) will  
>> compile as
>> it does today.
>>
>> The extended enhanced for each statement will operate as follows.
>> The iterator control variable is a standard variable declared to be
>> final. It will never be null. The type is dependent on whether the
>> expression is an array or an Iterable. It will either be
>> ArrayIterationControl<T> or IterableIterationControl<T>. The type  
>> is not
>> specified as it is redundent information, ie. the type is inferred.  
>> It
>> is scoped for the life of the loop.
>>
>> public final class IterableIterationControlIterator<T> {
>>    public IterableIterationControlIterator(Iterable<T> iterable) {
>>      this.control = new  
>> IterableIterationControl(iterable.iterator());
>>    }
>>    public boolean hasNext() { return control.hasNext() }
>>    public T next() { return control.next() }
>>    public IterableIterationControl<T> control() { return control }
>> }
>> public final class IterableIterationControl<T> {
>>    public IterableIterationControl(Iterator<T> iteratorToWrap) {
>>      this.it = iteratorToWrap;
>>    }
>>    boolean hasNext() { return it.hasNext() }
>>    T next() { originalIndex++; if (lastWasRemoved) { lastWasRemoved =
>> false } else { index++ } return it.next() }
>>    public T remove() { removed++; lastWasRemoved = true; return
>> it.remove() }
>>    public int index() { return index }
>>    public int originalIndex() { return originalIndex }
>>    public boolean isFirst() { return index == 1 }
>>    public boolean isLast() { return it.hasNext() == false }
>> }
>>
>> public final class ArrayIterationControlIterator<T> {
>>    public ArrayIterationControlIterator(T[] array) {
>>      this.control = new ArrayIterationControl(array);
>>    }
>>    public boolean hasNext() { return control.hasNext() }
>>    public T next() { return control.next() }
>>    public ArrayIterationControl<T> control() { return control }
>> }
>> public final class ArrayIterationControl<T> {
>>    public ArrayIterationControl(T[] array) { this.array = array; }
>>    boolean hasNext() { return index < array.length; }
>>    T next() { return array[++index]; }
>>    public int index() { return index - 1; }
>>    public boolean isFirst() { return index == 1; }
>>    public boolean isLast() { return index == array.length; }
>> }
>>
>> Exception analysis:
>> The method remove() on the iteration control variable can throw an
>> UnsuportedOperationException. However, this is no different from any
>> other method call.
>>
>> Definite assignment:
>> The new variable iteration control variable is a final variable  
>> that is
>> definitely assigned from creation.
>>
>> COMPILATION:
>> The extended enhanced for each loop is implemented by wrapping the  
>> two
>> control classes around the Iterable or the array.
>>
>> The Iterable design is desugared from:
>>
>>    for (T item : iterable : control) { ... }
>>
>> to:
>>    {
>>      IterableIterationControlIterator<T> $it = new
>> IterableIterationControlIterator(iterable);
>>      IterableIterationControl<T> control = $it.control();
>>      while ($it.hasNext()) {
>>        T item = $it.next();
>>        ...
>>      }
>>    }
>>
>> The array design is desugared similarly:
>>
>>    {
>>      ArrayIterationControlIterator<T> $it = new
>> ArrayIterationControlIterator(iterable);
>>      ArrayIterationControl<T> control = $it.control();
>>      while ($it.hasNext()) {
>>        T item = $it.next();
>>        ...
>>      }
>>    }
>>
>> There is the option to optimise this if the iteration control  
>> variable
>> is not assigned to any other variable or passed to any other method.
>> However, that is out of scope for now.
>>
>> TESTING:
>> Testing will be similar to the enhanced for loop. Arrays and  
>> Iterables
>> of various types and sizes will be used. The null expression will  
>> also
>> be tested.
>>
>> LIBRARY SUPPORT:
>> Yes, as detailed above.
>>
>> REFLECTIVE APIS:
>> No.
>>
>> OTHER CHANGES:
>> The javac tree API would need to be updated to model the change.
>>
>> MIGRATION:
>> Migration is not required. However, an IDE refactoring could now  
>> convert
>> more int and Iterator based for loops than it does at present.
>>
>>
>> *COMPATIBILITY*
>>
>> BREAKING CHANGES:
>> No breaking changes are known using this conversion scheme.
>>
>> EXISTING PROGRAMS:
>> This conversion is pure syntax sugar, so there are no known  
>> interactions
>> with existing programs.
>>
>>
>> *REFERENCES*
>>
>> EXISTING BUGS:
>> I searched the bug database, but nothing came up (which is  
>> surprising).
>>
>> URL FOR PROTOTYPE:
>> None
>>
>> DOCUMENTS:
>> [1] Stephen Colebourne's blog:
>> http://www.jroller.com/scolebourne/entry/java_7_for_each_loop
>> [2] Stephen Colebourne's original writeup:
>> http://docs.google.com/Edit?docID=dfn5297z_15ck7x5ghr
>>
>>
>> *DESIGN ISSUES*
>> There are numerous alternative ways in which this feature can be  
>> added.
>> These include:
>> - using the keyword:
>>    for (String str : list) {
>>      for.remove();  // problem is nested for loops
>>    }
>> - using a label as a psuedo-variable:
>>    it: for (String str : list) {
>>      it:remove();  // note colon and not dot
>>    }
>> - using an additional clause before the for each colon:
>>    for (String str, int index : list) {
>>      // no access to remove, and conflicts for for each for maps
>>    }
>>
>> The chosen solution involves simple Java classes, and a simple  
>> desugar.
>> The downside of the chosen solution is performance, as it involves
>> creating two wrapping objects and routing hasNext() and next() via
>> additional layers of method calls. A possible extension would be  
>> for the
>> compiler to identify if the iteration control variable is not  
>> passed to
>> another method. If so, then the code could be all be generated  
>> inline.
>>
>>
>>
>>
>>
>>
>
>



From reinier at zwitserloot.com  Wed Apr 22 17:39:51 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Thu, 23 Apr 2009 02:39:51 +0200
Subject: PROPOSAL: Named method parameters
In-Reply-To: <49EDE7E7.7040907@sun.com>
References: <4ce75f920903210915pa2b27b3g38841e342a78de77@mail.gmail.com>
	<49EDE7E7.7040907@sun.com>
Message-ID: <4CEAFE97-F979-4B3D-9688-2DFE570E4D93@zwitserloot.com>

rt.jar indeed does not include paramnames.

Compiling and jarring all of it gives you 13MB without any debug info,  
and 15MB when including all local variables (there's no easy way to  
compile with just argnames (or, better yet, argnames for non-private  
methods), stil, that's quite a change, so consider the semi-proposal  
revoked. (Though, it does help support my earlier pre-proposal where  
source files explicitly declare a method to be accessible via named  
parameter call).

  --Reinier Zwitserloot
Like it? Tip it!
http://tipit.to



On Apr 21, 2009, at 17:36, Joseph D. Darcy wrote:

> Catching up on responses, as has been further discussed on the list
> recently, requests in this general vein have been considered before in
> JDK 6.  While there are certainly use-cases this facility could  
> clarify,
> I remain unconvinced of the cost/benefit ratio of this proposal.
>
> A few design notes, a single @PublicParameterNames annotation with a
> boolean member could be used instead of a pair of "do it/don't do it"
> annotations.
>
> A full proposal for this facility would need to deal with the cases
> where the number of parameters in the class file differs from the  
> number
> of parameters in the source code, a situation already mildly exposed
> when calling toGenericString on some Method and Constructor objects.
>
> Not supporting parameter reordering greatly simplifies the proposal by
> leaving method selection largely unaffected, but also seems to limit  
> the
> usefulness of the proposal.  If the main benefit is just seeing the
> parameter name in the program text; can't the IDE do that?
>
> I'd isn't clear to me how @PublicParameterNames would interact with
> overridden methods in class hierarchies.  Presumably the names of the
> static type of the call site would need be match, even though the
> runtime type could differ.  If a subclass overrode a method and  
> changed
> its parameter names (which currently has no affect on compatibility),
> the subclass would no longer be substitutable for the parent class,
> which would break a fundamental design principle.
>
> At least there is no binary compatibility impact since the names would
> only be checked at compile time and binary compatibility is about
> preserving the ability to link.
>
> -Joe
>
> Paul Martin wrote:
>> I'd like to propose the implementation of optionally named method
>> parameters, and suggest that they are particularly useful when  
>> creating
>> immutable objects (which are important in our increasingly concurrent
>> world).
>>
>> Note that this is a topic that seems to have been considered before  
>> (see the
>> note in http://paulhammant.com/blog/announcing_paranamer.html which  
>> suggests
>> that it was even considered for Java 6), but I can't see it in the  
>> current
>> list of Java 7 changes or in the Project Coin mailing list archives  
>> (though
>> others have also discussed it in relation to Java 7, such as Alex  
>> Miller in
>> http://tech.puredanger.com/2007/08/15/dr-java7/ and
>> http://tech.puredanger.com/2007/10/11/java7-roundup-32/).   
>> Therefore I am
>> proposing it here - I think that it is an important change (unless  
>> anyone
>> can suggest how I can reasonably create an immutable object with  
>> four or
>> more properties without using a Builder or a list of unnamed  
>> parameters).
>>
>> Also note that other relevant references include:
>> http://blogs.sun.com/abuckley/entry/named_parameters (which  
>> discusses why
>> parameter reordering might be difficult),
>> http://beust.com/weblog/archives/000096.html (which suggests that  
>> we do not
>> need named parameters, but really just shows the use of the Builder  
>> pattern
>> which has limitations).
>>
>>
>> Named method parameters
>>
>> AUTHOR(S):
>>
>> Paul Martin
>>
>> OVERVIEW
>>
>> FEATURE SUMMARY:
>>
>> Named parameters allow a method or constructor caller to explicitly  
>> state
>> the parameter name of each parameter value passed to the method or
>> constructor.  Without named parameters, only the order of the  
>> parameter
>> values is significant (and it may not be clear what each value  
>> represents).
>>
>> MAJOR ADVANTAGE:
>>
>> This is a relatively simple way of introducing named parameters to  
>> the Java
>> platform.
>>
>> MAJOR BENEFIT:
>>
>> Named parameters allow method calls with relatively long lists of  
>> parameters
>> (greater than 3) to be understood by developers.  This can also  
>> facilitate
>> the direct use of constructors and factory methods to create  
>> immutable
>> objects, where otherwise Builders or mutable JavaBeans would be  
>> required.
>>
>> MAJOR DISADVANTAGE:
>>
>> The syntax for method calls would change to allow both named and  
>> unnamed
>> parameters to be used.
>>
>> Named parameters might be used too often, which could unnecessarily  
>> clutter
>> source files.
>>
>> Metadata to store the names of the parameters must be added to  
>> classfiles
>> (for example as annotations).
>>
>> The use of annotations to describe named parameters would mean that  
>> no
>> metadata would be stored about the parameter names used by the method
>> caller, and so no runtime checks to match the parameter names being  
>> used
>> could be made (only compile-time).  If the parameter names change  
>> (but
>> otherwise the method signature does not), then the method caller  
>> would not
>> be aware of the changes until it was recompiled.  Note that this is  
>> existing
>> behaviour for unnamed parameters, and would only be a problem if  
>> the meaning
>> of the parameters also changes (which should indicate that the  
>> caller would
>> need to change anyway, but this would not be detected automatically  
>> at
>> runtime).
>>
>> ALTERNATIVES:
>>
>> Unnamed parameters can make the same method calls as named  
>> parameters, but
>> if there are many parameters they are harder to understand and  
>> prone to
>> ordering-related bugs (particularly for primitive types or Strings).
>>
>> The Builder pattern can be used to simulate named parameters in
>> constructors/factory methods.  For example the following class uses a
>> Builder to initialise itself (note that only two properties are  
>> used to
>> simplify the example):
>>
>>    public final class MyClass {
>>
>>        private final String name;
>>        private final int age;
>>
>>        private MyClass(Builder b) {
>>            this.name = b.name;
>>            this.age = b.age;
>>        }
>>
>>        public static class Builder {
>>
>>            private String name;
>>            private int age;
>>
>>            /**
>>             * Name to set.
>>             */
>>            public Builder setName(String name) {
>>               this.name = name;
>>               return this;
>>            }
>>
>>            /**
>>             * Age to set
>>            */
>>            public Builder setAge(int age) {
>>                this.age = age;
>>                return this;
>>            }
>>
>>            public MyClass build() {
>>               return new MyClass(this);
>>            }
>>        }
>>    }
>>
>> Objects can then be constructed in the following manner:
>>
>>    MyClass obj = new  
>> MyClass.Builder().setName("Fred").setAge(53).build();
>>
>> However, the use of a builder requires additional code, and all  
>> parameters
>> are effectively optional from the perspective of the compiler (it  
>> cannot
>> easily check that all of the required setter methods have been  
>> called), so
>> bugs may occur where parameter values are not set.  Note that  
>> runtime checks
>> can be made to ensure that all property values are set, but they  
>> involve
>> additional work and cannot be used by the compiler (though static  
>> analysis
>> of the code in conjunction with annotations might be able to repeat  
>> many of
>> these checks).
>>
>> There are also many ways to implement named parameters that are  
>> different to
>> the solution proposed here.  These include:
>>
>> Implement optional named parameters on all methods:  This avoids  
>> the need
>> for the @PublicParameterNames annotation, but may mean inconsistent  
>> usage of
>> named parameters - the annotation is also a suggestion for the use  
>> of named
>> parameters by the caller (which IDEs can also make use of).  This  
>> will also
>> highlight the difference to classfiles compiled with earlier  
>> versions of
>> Java, where named parameters cannot be used at all (since it will  
>> then not
>> be obvious when named parameters can and cannot be used).
>>
>> Add parameter names to the classfile as 'fundamental' method  
>> metadata rather
>> than as annotations: This may allow closer integration of the named
>> parameters with the rest of the language, but its impact on the  
>> rest of the
>> language (and JVM) is much greater.  The same inconsistencies and
>> incompatibilities described in the previous alternative would also  
>> apply.
>> In addition, the use of annotations should not preclude the  
>> subsequent
>> modification of classfiles in a later release - the annotations  
>> could still
>> remain (at a potential cost of some duplication).
>>
>> EXAMPLES
>>
>> SIMPLE EXAMPLE:
>>
>> Constructor declaration:
>>
>>    @PublicParameterNames
>>    public MyClass(String name, int age) { ....
>>
>> Constructor use:
>>
>>    MyClass obj = new MyClass(name: "Fred", age: 53);
>>
>> ADVANCED EXAMPLE: Show advanced usage(s) of the feature.
>>
>> The full class definition from the simple example is shown below,  
>> as a
>> contrast to that provided in the Builder example.
>>
>>    public final class MyClass {
>>
>>        private final String name;
>>        private final int age;
>>
>>        /**
>>         * @param name Name to set
>>         * @param age Age to set
>>         */
>>
>>        @PublicParameterNames
>>        public MyClass(String name, int age) {
>>            this.name = name;
>>            this.age = age;
>>        }
>>    }
>>
>> DETAILS
>>
>> SPECIFICATION:
>>
>> The @PublicParameterNames annotation is used on a constructor or  
>> method to
>> allow named parameters to be used when calling it.  It can also be  
>> applied
>> to a class or package to apply to all methods within.  Similarly, a
>> @NoParameterNames annotation can be used on a constructor, method,  
>> or class
>> to override the use of @PublicParameterNames at a higher level.
>>
>> The compiler can then automatically generate a
>> @PublicParameterName(value="parameter-name") annotation for each  
>> affected
>> method.  These can then be used by the compiler (and IDE) to  
>> validate the
>> parameter names used by callers of the method or constructor.
>>
>> The use of parameter names by callers is always optional (primarily  
>> for
>> backwards compatibility).  However, parameter names cannot be used  
>> for some
>> parameters and not others (this would make the code harder to read).
>>
>> Parameters must always be specified in the same order regardless of  
>> whether
>> parameter names are used - parameter reordering by callers is not  
>> allowed
>> (reordering would make overloading difficult, and is not really  
>> necessary).
>>
>> Inheritance: Neither the @PublicParameterNames annotation (and
>> @NoParameterNames annotation), or the names of the parameters  
>> themselves,
>> need to be inherited.  This is because only static evaluation of a  
>> caller's
>> parameter names will be applied (rather than at runtime), so the  
>> callers
>> parameter names only need to match those of the declared type of the
>> target.  However, it would still be advisable to reuse the same  
>> parameter
>> names and annotations when overriding a method (IDEs could help  
>> with this).
>>
>> COMPILATION:
>>
>> The compiler must automatically generate a
>> @PublicParameterName(value="parameter-name") annotation for each  
>> method and
>> constructor annotated with @PublicParameterNames (or whose the  
>> parent class
>> or package is annotated with @PublicParameterNames and the child  
>> class or
>> method does not override it with @NoParameterNames).
>>
>> For example:
>>
>>    int myMethod(int param1, String param2)
>>
>> Would effectively become:
>>
>>    int myMethod(@PublicParameterName("param1") int param1,
>> @PublicParameterName("param2") String param2)
>>
>> Method-calling syntax would need to change, using a colon to  
>> separate the
>> parameter name and value where the are used.  For example:
>>
>>   MyClass obj = new MyClass(name: "Fred", age: 53);
>>
>> When a method caller uses parameter names, the compiler must check  
>> that
>> those parameter names exactly match the value of generated
>> @PublicParameterName annotations of the target method or  
>> constructor.  It is
>> a compilation error if they do not match or the target method or  
>> constructor
>> does not have named parameters.
>>
>> IDEs can use the @PublicParameterNames and @NoParameterNames  
>> annotations (or
>> @PublicParameterName directly) to automatically insert the relevant
>> parameter names as part of code-completion.  Additional refactoring  
>> support
>> would also be required to enable parameter names to be renamed, or  
>> added and
>> removed completely.
>>
>> Frameworks such as Spring can use the same annotations to allow  
>> objects to
>> be created from their configuration files using named parameters to
>> constructors and factory methods.  Currently they only allow  
>> objects to be
>> created from configuration files as JavaBeans (with setter methods)  
>> or with
>> ordered (and unnamed) parameters.
>>
>> TESTING:
>>
>> The feature can be tested by compiling and running programs that  
>> exercise
>> the feature.
>>
>> LIBRARY SUPPORT:
>>
>> No.
>>
>> REFLECTIVE APIS:
>>
>> java.lang.reflect.Method and java.lang.reflect.Constructor could be  
>> enhanced
>> with new methods that return parameter names.  However, that is not  
>> required
>> to successfully implement the proposal.
>>
>> OTHER CHANGES:
>>
>> No.  The use of named parameters is always optional.  The javadoc  
>> tool
>> already documents parameter names.  Other tools/libraries might  
>> benefit from
>> these changes, but their use is not required.
>>
>> MIGRATION:
>>
>> The @PublicParameterNames annotation (and @NoParameterNames  
>> annotation)
>> simply needs to be added to the appropriate methods.  IDEs could then
>> suggest the use of parameter names for the method's callers, and  
>> apply the
>> changes automatically.
>>
>> COMPATIBILITY
>>
>> BREAKING CHANGES:
>>
>> No.
>>
>> EXISTING PROGRAMS:
>>
>> The changes required by this feature should be transparent to  
>> existing
>> source and class files if annotations are used internally to  
>> describe the
>> named parameters.  I am not sure what the impact would be otherwise.
>>
>> REFERENCES
>>
>> EXISTING BUGS:
>>
>> 4124331 (though it is set to 11-Closed, Will Not Fix, request for
>> enhancement, and from 1998)
>>
>>
>
>



From reinier at zwitserloot.com  Wed Apr 22 17:41:31 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Thu, 23 Apr 2009 02:41:31 +0200
Subject: SUBMISSION : A second look on "named parameters" / Clarification
	on the scope
In-Reply-To: <15e8b9d20904200852q70bf48bcm2c9beb8685902488@mail.gmail.com>
References: <2dc3bd00904200118s35e085fdk6f4ef3cac83cd6e9@mail.gmail.com>
	<E807B68F-1621-4AD7-8052-146B0C45FB89@zwitserloot.com>
	<15e8b9d20904200852q70bf48bcm2c9beb8685902488@mail.gmail.com>
Message-ID: <F2A1B839-BBF0-4657-B606-4775CA114ECD@zwitserloot.com>

Neal: No, this is not an API change. It's a change to the JVM spec  
(specifically, the section about class files). If it doesn't fit  
project coin, then what would it fit? Most certainly not the coin-but- 
for-API-updates. Where else would 'class files MUST include the names  
of method parameters' fit?

Adding the ability to get this information via reflection would be an  
API change, but many coin proposals have a matching change to the  
reflection API.

  --Reinier Zwitserloot
Like it? Tip it!
http://tipit.to


On Apr 20, 2009, at 17:52, Neal Gafter wrote:

> Reiner-
>
> This is a library proposal, not a language proposal, so it doesn't  
> need to be done inside project Coin.
>
> -Neal
>
> On Mon, Apr 20, 2009 at 3:16 AM, Reinier Zwitserloot <reinier at zwitserloot.com 
> > wrote:
> Ah, now I understand.
>
> I've got a much simpler proposal to address this issue.
>
> NB: Joe, I know coin's long gone, but perhaps consider this one anyway
> - it seems to me that some sort of named parameters proposal is likely
> to be accepted in the future, and adding names now should ease
> transition. As part of the effort I've listed all possibly
> complication I can come up with, at the end.
>
> Proposal:
>
>
> Starting from the new class file format introduced in java7 (due to
> module support, the class format is definitely getting a version
> bump), all compilers MUST put the names of the parameters in the class
> file (javac -g style), and obfuscators/compressors/whatever MUST NOT
> remove this; a class file with version v50 (or whatever number its
> going to end up being) won't even pass the verifier without the names
> in place.
>
> Add an API call on the java.lang.reflect.Method object to obtain the
> names of the parameters (returns a String[], or 'null' if they aren't
> there. Calling this on a param-less method returns an empty array, not
> null). Having the names is an all-or-nothing situation: Either the
> names are all there and this call works, or some/all are missing, and
> then this call does not work. I'm not sure if you can even have just a
> few names defined in the .class file format, but even if you can, that
> situation should be so extremely rare, its not worth writing up a
> complicated rule for). It is guaranteed that if the array exists (is
> not null), then each array element is not null.
>
> Voila. No need to turn in a proposal that's more complicated than most
> just to solve this simple problem.
>
> Complications:
>
> A) It would no longer be possible to rewrite a v49 and below class
> without debug info into a v50 and up class file without having the
> source file, but I don't actually know of any tools that attempt to do
> this.
>
> B) Code that generates class files on the fly (like proxy generators
> and the like) will need to consider the names of method parameters if/
> when they update the class file format they generate to v50+. A proxy
> generator has issues when it is trying to generate a v50+ proxy where
> its input object's class spec AND the input interface to proxy on are
> both v49- without debug info, for example.
>
> C) A (bad) quick-fix for either of the above issues is to just use
> 'arg0', 'arg1', 'arg2', analogous to what e.g. eclipse does when
> showing method signatures for methods in classes where there is no
> source, no debug info and no javadoc. This is not at all the right
> idea. A small risk that the class file format documentation should
> mention as not being appropriate unless there is absolutely no other
> option.
>
> D) Most code these days ships with source, or javadoc, or debug info,
> so that auto-complete shows the proper names for each parameter, but
> this certainly isn't true for /all/ java code out there. After this
> change, method param names become visible to all. This may not be a
> desired side-effect for programming shops that export libraries to
> clients where their method parameter names are inappropriate (swear
> words, or 'x', 'y', and 'z' and this creates deserved but nevertheless
> unexpected ridicule for sucking at programming style). I think this is
> an acceptable price to pay. Parameters are method-local which are
> extremely easy to rename with your friendly neighbourhood IDE's
> refactor tool.
>
> E) While technically the names are NOT part of API, and you CAN freely
> change names around without breaking any code, old or new, the names
> still do become a little more enshrined as at least almost part of the
> public API. This is already the case to some extent (param names show
> up in various tooling support such as javadoc and auto-completing
> IDEs) but this change would move parameter names a little more towards
> a complete member of public API. This is an issue, but its also the
> point of this proposal: Move towards a java world where parameter
> names are universally available and are meaningful. I don't think this
> is a serious problem, because A) names already have a flavour of
> importance right now, and B) While they become more important with
> this proposal, they still aren't true public API, and changing names
> even after this proposal is accepted is not backwards incompatible.
>
> F) Confusion may arise when these names are unintentionally taken as
> being either part of public API, or being hierarchical; they are in
> fact neither. For example, this proposal makes no attempt to harmonize
> name conflicts; if interface A has void foo(int bar), and interface B
> has void foo(int baz), you can still of course write a class that
> implements both of these. You can even name your foo's parameter
> 'floobargle', of course. The aim of this proposal does not involve
> making parameter names inherit sensibly.
>
>
>  --Reinier Zwitserloot
>
>
>
> On Apr 20, 2009, at 10:18, Jean-Baptiste Bugeaud wrote:
>
> > Hello Reinier, Hello Joe,
> >
> > Thanks for your feedback.
> >
> > 2009/4/19 Reinier Zwitserloot <reinier at zwitserloot.com>:
> >> Your proposal is very incomplete. Three major nits:
> >>
> >> A. Did I miss something, or did you totally forget to include an
> >> example of
> >> calling a method with named parameters? Something like:
> >>
> >> doLogin(user: "foobar", password: new char[] { 'a', 'b', 'c' })
> >
> > Reiner, I think my submission name is misleading everybody. This is
> > not the same thing you debate some times back. My mistake ... I  
> should
> > have clarified from the start : I do not look at adding direct  
> call by
> > parameter name into the language (say "? la" ObjectiveC). But  
> simply a
> > reliable way access to parameter name and name a parameter's name in
> > static way thru time. See bug 6444738 for differences.
> >
> > Parameter names are very usefull information in most cases, and at
> > this time, either implementers use duplicate annotation (dummy
> > annotations storing again the same name) or they use tools such as  
> ASM
> > to workaround the lack of API in the JDK.
> >
> > At the begining, I thought this requirement did not required a small
> > synthax language change : a new API would be enough. But soon I
> > realized that introducing name parameter that are static thru time,
> > introduce anyway a new paradigm in the language that developer  
> should
> > be able to control directly : do I want this parameter name to be
> > static thu time ? or do I want to let the compiler decide as usual ?
> >
> > A compiler option is not the suitable tool for this.
> > If this is a global switch, it will not offer the fine grain  
> required.
> > If this is a per class/per package option, it will clutter the
> > command line.
> > And in both cases, it will not offer paradigm separation with the
> > legacy. Thus you can not rely on the parameter name because you  
> never
> > know if developper has stored the name accidentaly or for purpose.
> >
> >> B. Why static? You might as well have picked 'strictfp' - it's a
> >> total
> >> non-sequitur choice. Re-use of existing keywords is not really a
> >> panacea; it
> >> waters down the anchoring ability of a keyword to virtually
> >> nothing. I'm not
> >> sure if context-sensitive keywords are any better, but java7 is
> >> already
> >> going to have at least one ('module'), so don't beat around the
> >> bush and
> >> just call it 'named'). Could be just me, but introducing a change
> >> which is
> >> not backwards compatible IF you have a type that's called
> >> 'named' (written
> >> just like that, all-lower case), is not something I find
> >> troublesome in the
> >> least. That's very ugly code, and a migration tool can fix this
> >> easily.
> >
> > Because of the definition a dictionary gives of it : something like
> > "showing little change" is exactly what I meant for this paradigm.  
> And
> > no "strictfp", as well as "const" and "goto" are not matching, you  
> see
> > ;-)
> >
> > If you think that this worth integrating a new keywork, then there  
> is
> > room for debate. I think static fits perfectly and is clear enough.
> > AFAIK, we already have final that is contextual? why not static  
> too ?
> > final is already stretched between two things : do not overload  
> member
> > and do not reasign variable.
> >
> > With the proposed language changed static modifier will be stretched
> > between static thru instances for members and static thru time for
> > variables.
> >
> >> C. You don't mention having default values for parameters, which is
> >> sort of
> >> the point of this exercise (otherwise you really still need
> >> builders  ; any
> >> method that has so many parameters that they need names probably
> >> needs a
> >> builder, and without defaults, not providing one and instead
> >> relying on
> >> named params is just an inferior bandaid to your ugly API; to get
> >> it right
> >> you STILL need to provide a builder. If, however, parameters can  
> have
> >> defaults, then you no longer need to make builders at all).
> >
> > This is because I am not asking for named call of method ... simply
> > for a way to access name of parameter. Just a completely different
> > topic.
> > I don't see why a parameter on an EJB is not meanfull for the  
> external
> > ? same for an webservice ? why a parameter name could not be  
> meanfull
> > ? I don't get your point.
> >
> > My design decision is the kind of decision that led to erasure based
> > genericity : it has some drawback, loss of real parametrics  
> instances
> > that could be usefull while reflection. But was the right decision  
> at
> > the right time or either we would have lots binary compatibility  
> or we
> > would still be debating wether or not implementing generics.
> >
> > My proposition on parameter name is analog, it is just meant to be
> > used ASAP but does it does not fully solve all the possible
> > expectations from this topic scope. Namely, should we call "by
> > parameter name" in the language ? and how ?
> >
> > Room is let for the coming decade ;-) But the propopsition does not
> > close doors to anything.
> >
> >> I suggest you look over the coin-dev mailing list; I entered a
> >> rough sketch
> >> of a named parameters proposal near the end of coin. I never wrote
> >> it up
> >> because I thought of it far too close to the deadline, and it's
> >> still of
> >> such high impact that I doubt it would pass muster for coin.
> >
> > Yes I've followed the debate :) But, again its my mistake "call by
> > parameter names" is a much more complex topic with lots of
> > performance/plaform impact. This is not a small language change  
> IMHO.
> > Again, I do not look for calling a direct method call using named
> > parameters .... just a way to retreive them.
> >
> > -- --
> >
> > Joe, yes "late I am" ;-)
> >
> > FYI, I got this proposition cooking for several months I was not  
> able
> > to find time to write & post it to you (pittyfull isn't it).
> >
> > If we remove the "language change" part (static named parameter) and
> > only keep the getParameterNames() API part (keep the regular  
> parameter
> > name), do you think this can be pushed to JDK7 even if out of  
> scope of
> > coin ? This is a very small change to the API and would solve lot of
> > time from lot of people.
> >
> > I mean, this API (along with the rest of the named parameter spec)  
> was
> > removed from JDK6, skiping this in JDK7 means years again to wait  
> for
> > it ? I think we are too much getting dependent on tools such as  
> ASM in
> > lots of places (JavaEE implementation stacks for instance). And we
> > have a good opportunity to remove the dependency for a clean/simple
> > solution IMHO.
> >
> > Best Regards,
> > JB
>
>
>



From neal at gafter.com  Wed Apr 22 17:47:38 2009
From: neal at gafter.com (Neal Gafter)
Date: Wed, 22 Apr 2009 17:47:38 -0700
Subject: SUBMISSION : A second look on "named parameters" / Clarification 
	on the scope
In-Reply-To: <F2A1B839-BBF0-4657-B606-4775CA114ECD@zwitserloot.com>
References: <2dc3bd00904200118s35e085fdk6f4ef3cac83cd6e9@mail.gmail.com> 
	<E807B68F-1621-4AD7-8052-146B0C45FB89@zwitserloot.com>
	<15e8b9d20904200852q70bf48bcm2c9beb8685902488@mail.gmail.com> 
	<F2A1B839-BBF0-4657-B606-4775CA114ECD@zwitserloot.com>
Message-ID: <15e8b9d20904221747y6d113ad3s5ed4dd380edbfe8c@mail.gmail.com>

I'd suggest either jsr292 or a separate change fed into the underlying java
7 platform jsr (through the openjdk)

On Wed, Apr 22, 2009 at 5:41 PM, Reinier Zwitserloot <
reinier at zwitserloot.com> wrote:

> Neal: No, this is not an API change. It's a change to the JVM spec
> (specifically, the section about class files). If it doesn't fit project
> coin, then what would it fit? Most certainly not the
> coin-but-for-API-updates. Where else would 'class files MUST include the
> names of method parameters' fit?
>
> Adding the ability to get this information via reflection would be an API
> change, but many coin proposals have a matching change to the reflection
> API.
>
>   --Reinier Zwitserloot
> Like it? Tip it!
> http://tipit.to
>
>
> On Apr 20, 2009, at 17:52, Neal Gafter wrote:
>
> Reiner-
>
> This is a library proposal, not a language proposal, so it doesn't need to
> be done inside project Coin.
>
> -Neal
>
> On Mon, Apr 20, 2009 at 3:16 AM, Reinier Zwitserloot <
> reinier at zwitserloot.com> wrote:
>
>> Ah, now I understand.
>>
>> I've got a much simpler proposal to address this issue.
>>
>> NB: Joe, I know coin's long gone, but perhaps consider this one anyway
>> - it seems to me that some sort of named parameters proposal is likely
>> to be accepted in the future, and adding names now should ease
>> transition. As part of the effort I've listed all possibly
>> complication I can come up with, at the end.
>>
>> Proposal:
>>
>>
>> Starting from the new class file format introduced in java7 (due to
>> module support, the class format is definitely getting a version
>> bump), all compilers MUST put the names of the parameters in the class
>> file (javac -g style), and obfuscators/compressors/whatever MUST NOT
>> remove this; a class file with version v50 (or whatever number its
>> going to end up being) won't even pass the verifier without the names
>> in place.
>>
>> Add an API call on the java.lang.reflect.Method object to obtain the
>> names of the parameters (returns a String[], or 'null' if they aren't
>> there. Calling this on a param-less method returns an empty array, not
>> null). Having the names is an all-or-nothing situation: Either the
>> names are all there and this call works, or some/all are missing, and
>> then this call does not work. I'm not sure if you can even have just a
>> few names defined in the .class file format, but even if you can, that
>> situation should be so extremely rare, its not worth writing up a
>> complicated rule for). It is guaranteed that if the array exists (is
>> not null), then each array element is not null.
>>
>> Voila. No need to turn in a proposal that's more complicated than most
>> just to solve this simple problem.
>>
>> Complications:
>>
>> A) It would no longer be possible to rewrite a v49 and below class
>> without debug info into a v50 and up class file without having the
>> source file, but I don't actually know of any tools that attempt to do
>> this.
>>
>> B) Code that generates class files on the fly (like proxy generators
>> and the like) will need to consider the names of method parameters if/
>> when they update the class file format they generate to v50+. A proxy
>> generator has issues when it is trying to generate a v50+ proxy where
>> its input object's class spec AND the input interface to proxy on are
>> both v49- without debug info, for example.
>>
>> C) A (bad) quick-fix for either of the above issues is to just use
>> 'arg0', 'arg1', 'arg2', analogous to what e.g. eclipse does when
>> showing method signatures for methods in classes where there is no
>> source, no debug info and no javadoc. This is not at all the right
>> idea. A small risk that the class file format documentation should
>> mention as not being appropriate unless there is absolutely no other
>> option.
>>
>> D) Most code these days ships with source, or javadoc, or debug info,
>> so that auto-complete shows the proper names for each parameter, but
>> this certainly isn't true for /all/ java code out there. After this
>> change, method param names become visible to all. This may not be a
>> desired side-effect for programming shops that export libraries to
>> clients where their method parameter names are inappropriate (swear
>> words, or 'x', 'y', and 'z' and this creates deserved but nevertheless
>> unexpected ridicule for sucking at programming style). I think this is
>> an acceptable price to pay. Parameters are method-local which are
>> extremely easy to rename with your friendly neighbourhood IDE's
>> refactor tool.
>>
>> E) While technically the names are NOT part of API, and you CAN freely
>> change names around without breaking any code, old or new, the names
>> still do become a little more enshrined as at least almost part of the
>> public API. This is already the case to some extent (param names show
>> up in various tooling support such as javadoc and auto-completing
>> IDEs) but this change would move parameter names a little more towards
>> a complete member of public API. This is an issue, but its also the
>> point of this proposal: Move towards a java world where parameter
>> names are universally available and are meaningful. I don't think this
>> is a serious problem, because A) names already have a flavour of
>> importance right now, and B) While they become more important with
>> this proposal, they still aren't true public API, and changing names
>> even after this proposal is accepted is not backwards incompatible.
>>
>> F) Confusion may arise when these names are unintentionally taken as
>> being either part of public API, or being hierarchical; they are in
>> fact neither. For example, this proposal makes no attempt to harmonize
>> name conflicts; if interface A has void foo(int bar), and interface B
>> has void foo(int baz), you can still of course write a class that
>> implements both of these. You can even name your foo's parameter
>> 'floobargle', of course. The aim of this proposal does not involve
>> making parameter names inherit sensibly.
>>
>>
>>  --Reinier Zwitserloot
>>
>>
>>
>> On Apr 20, 2009, at 10:18, Jean-Baptiste Bugeaud wrote:
>>
>> > Hello Reinier, Hello Joe,
>> >
>> > Thanks for your feedback.
>> >
>> > 2009/4/19 Reinier Zwitserloot <reinier at zwitserloot.com>:
>> >> Your proposal is very incomplete. Three major nits:
>> >>
>> >> A. Did I miss something, or did you totally forget to include an
>> >> example of
>> >> calling a method with named parameters? Something like:
>> >>
>> >> doLogin(user: "foobar", password: new char[] { 'a', 'b', 'c' })
>> >
>> > Reiner, I think my submission name is misleading everybody. This is
>> > not the same thing you debate some times back. My mistake ... I should
>> > have clarified from the start : I do not look at adding direct call by
>> > parameter name into the language (say "? la" ObjectiveC). But simply a
>> > reliable way access to parameter name and name a parameter's name in
>> > static way thru time. See bug 6444738 for differences.
>> >
>> > Parameter names are very usefull information in most cases, and at
>> > this time, either implementers use duplicate annotation (dummy
>> > annotations storing again the same name) or they use tools such as ASM
>> > to workaround the lack of API in the JDK.
>> >
>> > At the begining, I thought this requirement did not required a small
>> > synthax language change : a new API would be enough. But soon I
>> > realized that introducing name parameter that are static thru time,
>> > introduce anyway a new paradigm in the language that developer should
>> > be able to control directly : do I want this parameter name to be
>> > static thu time ? or do I want to let the compiler decide as usual ?
>> >
>> > A compiler option is not the suitable tool for this.
>> > If this is a global switch, it will not offer the fine grain required.
>> > If this is a per class/per package option, it will clutter the
>> > command line.
>> > And in both cases, it will not offer paradigm separation with the
>> > legacy. Thus you can not rely on the parameter name because you never
>> > know if developper has stored the name accidentaly or for purpose.
>> >
>> >> B. Why static? You might as well have picked 'strictfp' - it's a
>> >> total
>> >> non-sequitur choice. Re-use of existing keywords is not really a
>> >> panacea; it
>> >> waters down the anchoring ability of a keyword to virtually
>> >> nothing. I'm not
>> >> sure if context-sensitive keywords are any better, but java7 is
>> >> already
>> >> going to have at least one ('module'), so don't beat around the
>> >> bush and
>> >> just call it 'named'). Could be just me, but introducing a change
>> >> which is
>> >> not backwards compatible IF you have a type that's called
>> >> 'named' (written
>> >> just like that, all-lower case), is not something I find
>> >> troublesome in the
>> >> least. That's very ugly code, and a migration tool can fix this
>> >> easily.
>> >
>> > Because of the definition a dictionary gives of it : something like
>> > "showing little change" is exactly what I meant for this paradigm. And
>> > no "strictfp", as well as "const" and "goto" are not matching, you see
>> > ;-)
>> >
>> > If you think that this worth integrating a new keywork, then there is
>> > room for debate. I think static fits perfectly and is clear enough.
>> > AFAIK, we already have final that is contextual? why not static too ?
>> > final is already stretched between two things : do not overload member
>> > and do not reasign variable.
>> >
>> > With the proposed language changed static modifier will be stretched
>> > between static thru instances for members and static thru time for
>> > variables.
>> >
>> >> C. You don't mention having default values for parameters, which is
>> >> sort of
>> >> the point of this exercise (otherwise you really still need
>> >> builders  ; any
>> >> method that has so many parameters that they need names probably
>> >> needs a
>> >> builder, and without defaults, not providing one and instead
>> >> relying on
>> >> named params is just an inferior bandaid to your ugly API; to get
>> >> it right
>> >> you STILL need to provide a builder. If, however, parameters can have
>> >> defaults, then you no longer need to make builders at all).
>> >
>> > This is because I am not asking for named call of method ... simply
>> > for a way to access name of parameter. Just a completely different
>> > topic.
>> > I don't see why a parameter on an EJB is not meanfull for the external
>> > ? same for an webservice ? why a parameter name could not be meanfull
>> > ? I don't get your point.
>> >
>> > My design decision is the kind of decision that led to erasure based
>> > genericity : it has some drawback, loss of real parametrics instances
>> > that could be usefull while reflection. But was the right decision at
>> > the right time or either we would have lots binary compatibility or we
>> > would still be debating wether or not implementing generics.
>> >
>> > My proposition on parameter name is analog, it is just meant to be
>> > used ASAP but does it does not fully solve all the possible
>> > expectations from this topic scope. Namely, should we call "by
>> > parameter name" in the language ? and how ?
>> >
>> > Room is let for the coming decade ;-) But the propopsition does not
>> > close doors to anything.
>> >
>> >> I suggest you look over the coin-dev mailing list; I entered a
>> >> rough sketch
>> >> of a named parameters proposal near the end of coin. I never wrote
>> >> it up
>> >> because I thought of it far too close to the deadline, and it's
>> >> still of
>> >> such high impact that I doubt it would pass muster for coin.
>> >
>> > Yes I've followed the debate :) But, again its my mistake "call by
>> > parameter names" is a much more complex topic with lots of
>> > performance/plaform impact. This is not a small language change IMHO.
>> > Again, I do not look for calling a direct method call using named
>> > parameters .... just a way to retreive them.
>> >
>> > -- --
>> >
>> > Joe, yes "late I am" ;-)
>> >
>> > FYI, I got this proposition cooking for several months I was not able
>> > to find time to write & post it to you (pittyfull isn't it).
>> >
>> > If we remove the "language change" part (static named parameter) and
>> > only keep the getParameterNames() API part (keep the regular parameter
>> > name), do you think this can be pushed to JDK7 even if out of scope of
>> > coin ? This is a very small change to the API and would solve lot of
>> > time from lot of people.
>> >
>> > I mean, this API (along with the rest of the named parameter spec) was
>> > removed from JDK6, skiping this in JDK7 means years again to wait for
>> > it ? I think we are too much getting dependent on tools such as ASM in
>> > lots of places (JavaEE implementation stacks for instance). And we
>> > have a good opportunity to remove the dependency for a clean/simple
>> > solution IMHO.
>> >
>> > Best Regards,
>> > JB
>>
>>
>>
>
>


From Joe.Darcy at Sun.COM  Wed Apr 22 21:08:15 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Wed, 22 Apr 2009 21:08:15 -0700
Subject: PROPOSAL: Enhanced for each loop iteration control
In-Reply-To: <3BBAA5CF-247E-430F-A271-A10C79642FF7@zwitserloot.com>
References: <49C56020.2070207@joda.org> <49EDE7B4.2090006@sun.com>
	<3BBAA5CF-247E-430F-A271-A10C79642FF7@zwitserloot.com>
Message-ID: <49EFE9AF.90909@sun.com>

Reinier Zwitserloot wrote:
> If the proposal was just about making the iterator available, I'd 
> agree with you, but the proposal adds methods like .first(), which are 
> /very/ useful indeed. It's right up there with ARM, and easily beats 
> string switching, in how applicable that would be.

A library to implement the utility wrapper around an Iterator could be 
added without the language change.

>
> Adding a .join() method to String or List (depending on taste) would 
> solve over half of the use-cases for the extended forloop, though.

Adding one method to string is preferable to a language change!

-Joe



From genman at noderunner.net  Thu Apr 23 10:44:46 2009
From: genman at noderunner.net (Elias Ross)
Date: Thu, 23 Apr 2009 10:44:46 -0700
Subject: Proposal: Allow a single-parameter method to be used as an infix 
	operator
Message-ID: <b517768e0904231044o2c3c8966q5abbd605657232e7@mail.gmail.com>

AUTHOR(S): Elias Ross

OVERVIEW

FEATURE SUMMARY: Allow a single-parameter method to be used as an
infix operator. Expressions like "object1.method(object2)" could be
replaced with an easier-to-read expression "object1 method object2".
This allows for easier to read code such as "a equals b" instead of
"a.equals(b)". This idea borrows from Scala, although this proposal
limits the complexity.

MAJOR ADVANTAGE: Since Java does not allow for operators or operator
overloading, all idiomatic expressions, such as "a.equals(b)", or
"a.contains(b)" must be written using dots and parenthesis.

MAJOR BENEFIT: Improvement in clarity for many idioms.

MAJOR DISADVANTAGE: Obviously, code with this feature would look quite
different than code without. Thus, I imagine it would look quite
inconsistent to have both used in the same codebase. Also, it's not
clear why, in the case of "object1 equals object2", when "object1" was
null, a NullPointerException should be thrown. It also may seemingly
collide with the "instanceof" operator.

It would potentially encourage increased use of single parameter methods.

ALTERNATIVES: None.

EXAMPLES

SIMPLE EXAMPLE:

boolean eq = "a" equals "b";

ADVANCED EXAMPLE: Show advanced usage(s) of the feature.

"abc" substring 1 matches "b."; // true
(new BigInteger(10) divide new BigDecimal(2)).longValue(); // 5

// The following would not compile
"abc" substring(1,2) equals "b";

DETAILS

SPECIFICATION:

Modification to
http://java.sun.com/docs/books/jls/second_edition/html/syntax.doc.html

Expression2Rest:
	{Infixop Expression3}
+	{Identifier Expression}
	Expression3 instanceof Type

The "Identifier" refers to a single parameter method belonging to a
class or instance, and "Expression" here evaluates to the argument
passed to this method.

COMPILATION: The compiler would treat the expression as a method call.

TESTING: Testing would be done to validate the grammar and conflict
with the "instanceof" operator.

LIBRARY SUPPORT: None.

REFLECTIVE APIS: None.

OTHER CHANGES: None.

MIGRATION: Code needs no migration. However, it might be nice to have
a tool to "clean up" existing code.

COMPATIBILITY

BREAKING CHANGES: None.

EXISTING PROGRAMS: Should continue to work.

REFERENCES

EXISTING BUGS: Unknown.

URL FOR PROTOTYPE (optional):


From Joe.Darcy at Sun.COM  Thu Apr 23 10:55:44 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Thu, 23 Apr 2009 10:55:44 -0700
Subject: Proposal: Allow a single-parameter method to be used as an infix
	operator
In-Reply-To: <b517768e0904231044o2c3c8966q5abbd605657232e7@mail.gmail.com>
References: <b517768e0904231044o2c3c8966q5abbd605657232e7@mail.gmail.com>
Message-ID: <49F0ABA0.2020400@sun.com>

The call for proposals period ended several weeks ago; this proposal is 
thus overdue and will not be considered.

-Joe

Elias Ross wrote:
> AUTHOR(S): Elias Ross
>
> OVERVIEW
>
> FEATURE SUMMARY: Allow a single-parameter method to be used as an
> infix operator. Expressions like "object1.method(object2)" could be
> replaced with an easier-to-read expression "object1 method object2".
> This allows for easier to read code such as "a equals b" instead of
> "a.equals(b)". This idea borrows from Scala, although this proposal
> limits the complexity.
>
> MAJOR ADVANTAGE: Since Java does not allow for operators or operator
> overloading, all idiomatic expressions, such as "a.equals(b)", or
> "a.contains(b)" must be written using dots and parenthesis.
>
> MAJOR BENEFIT: Improvement in clarity for many idioms.
>
> MAJOR DISADVANTAGE: Obviously, code with this feature would look quite
> different than code without. Thus, I imagine it would look quite
> inconsistent to have both used in the same codebase. Also, it's not
> clear why, in the case of "object1 equals object2", when "object1" was
> null, a NullPointerException should be thrown. It also may seemingly
> collide with the "instanceof" operator.
>
> It would potentially encourage increased use of single parameter methods.
>
> ALTERNATIVES: None.
>
> EXAMPLES
>
> SIMPLE EXAMPLE:
>
> boolean eq = "a" equals "b";
>
> ADVANCED EXAMPLE: Show advanced usage(s) of the feature.
>
> "abc" substring 1 matches "b."; // true
> (new BigInteger(10) divide new BigDecimal(2)).longValue(); // 5
>
> // The following would not compile
> "abc" substring(1,2) equals "b";
>
> DETAILS
>
> SPECIFICATION:
>
> Modification to
> http://java.sun.com/docs/books/jls/second_edition/html/syntax.doc.html
>
> Expression2Rest:
> 	{Infixop Expression3}
> +	{Identifier Expression}
> 	Expression3 instanceof Type
>
> The "Identifier" refers to a single parameter method belonging to a
> class or instance, and "Expression" here evaluates to the argument
> passed to this method.
>
> COMPILATION: The compiler would treat the expression as a method call.
>
> TESTING: Testing would be done to validate the grammar and conflict
> with the "instanceof" operator.
>
> LIBRARY SUPPORT: None.
>
> REFLECTIVE APIS: None.
>
> OTHER CHANGES: None.
>
> MIGRATION: Code needs no migration. However, it might be nice to have
> a tool to "clean up" existing code.
>
> COMPATIBILITY
>
> BREAKING CHANGES: None.
>
> EXISTING PROGRAMS: Should continue to work.
>
> REFERENCES
>
> EXISTING BUGS: Unknown.
>
> URL FOR PROTOTYPE (optional):
>
>   



From rssh at gradsoft.com.ua  Thu Apr 23 15:34:37 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Fri, 24 Apr 2009 01:34:37 +0300 (EEST)
Subject: Integer widening operators: some preliminary statistics.
Message-ID: <4f30e61b8c0c456c06ca18996e3299e9.squirrel@wmail.gradsoft.ua>


Good day, Bruce.

Some data about integer widening operator:
http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000906.html

3 checks was implemented:
 1. model check for expression like  ($x && 0xff) or (0xff &  $x) where $x
must have a type byte (original request). This check named as "widening
operator (semantics)"

2. syntax check for expression like  ($x && 0xff) or (0xff &  $x) where $x
can have any type. This check named as "widening operator (syntax)"

 Example of second but not first:
<pre>
  public static short reverseBytes(short s) {
    return (short) (((s & 0xff) << 8) | ((s & 0xff00) >> 8));
  }
</pre>
<pre>
       byte[] nounce = new byte[24];
        for (int i=0;i<8;i++)
        {
            nounce[i]=(byte)(ts&0xff);
            ts=ts>>8;
            nounce[8+i]=(byte)(sk&0xff);
            sk=sk>>8;
        }
</pre>

3. count of all expressions with bitwise and. (names as all bit ands)

Than, results for jetty was:

all bit ands    :       121
widening operator (semantics)   :       10
widening operator (syntax)      :       20

// some other counts, to compare with:
rethrow clause  :       34
string in switch        :       19

hibernate does not use bitwise and at all.
gwt-users have 2 entries of syntax pattern (actually this is reverseBytes
function).

Result for jdk I will publish tomorrow, when ones will be ready.

It was preliminary data (one from 3 packages use 'bitwise and') more
statistics and some analysis will be available throught few days (with
data about for-s and ERP in dataset).

 Best Regards !







From j16sdiz at gmail.com  Thu Apr 23 18:18:00 2009
From: j16sdiz at gmail.com (Daniel Cheng)
Date: Fri, 24 Apr 2009 09:18:00 +0800
Subject: Integer widening operators: some preliminary statistics.
In-Reply-To: <4f30e61b8c0c456c06ca18996e3299e9.squirrel@wmail.gradsoft.ua>
References: <4f30e61b8c0c456c06ca18996e3299e9.squirrel@wmail.gradsoft.ua>
Message-ID: <ff6a9c820904231818s523b7a27h88992944f2551fd4@mail.gmail.com>

On Fri, Apr 24, 2009 at 6:34 AM, Ruslan Shevchenko <rssh at gradsoft.com.ua> wrote:
>
> Good day, Bruce.
>
> Some data about integer widening operator:
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000906.html
>
> 3 checks was implemented:
> ?1. model check for expression like ?($x && 0xff) or (0xff & ?$x) where $x
> must have a type byte (original request). This check named as "widening
> operator (semantics)"
>
> 2. syntax check for expression like ?($x && 0xff) or (0xff & ?$x) where $x
> can have any type. This check named as "widening operator (syntax)"
>
> ?Example of second but not first:
> <pre>
> ?public static short reverseBytes(short s) {
> ? ?return (short) (((s & 0xff) << 8) | ((s & 0xff00) >> 8));
> ?}
> </pre>
> <pre>
> ? ? ? byte[] nounce = new byte[24];
> ? ? ? ?for (int i=0;i<8;i++)
> ? ? ? ?{
> ? ? ? ? ? ?nounce[i]=(byte)(ts&0xff);
> ? ? ? ? ? ?ts=ts>>8;
> ? ? ? ? ? ?nounce[8+i]=(byte)(sk&0xff);
> ? ? ? ? ? ?sk=sk>>8;
> ? ? ? ?}
> </pre>
>
> 3. count of all expressions with bitwise and. (names as all bit ands)
>
> Than, results for jetty was:
>
> all bit ands ? ?: ? ? ? 121
> widening operator (semantics) ? : ? ? ? 10
> widening operator (syntax) ? ? ?: ? ? ? 20
>
> // some other counts, to compare with:
> rethrow clause ?: ? ? ? 34
> string in switch ? ? ? ?: ? ? ? 19
>
> hibernate does not use bitwise and at all.
> gwt-users have 2 entries of syntax pattern (actually this is reverseBytes
> function).
>
> Result for jdk I will publish tomorrow, when ones will be ready.

I expect this kind of usage are more common in low level formats.
Try MINA SSH, OpenDS, etc..

> It was preliminary data (one from 3 packages use 'bitwise and') more
> statistics and some analysis will be available throught few days (with
> data about for-s and ERP in dataset).
>
> ?Best Regards !
>
>
>
>
>
>
>


From rssh at gradsoft.com.ua  Thu Apr 23 22:42:56 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Fri, 24 Apr 2009 08:42:56 +0300 (EEST)
Subject: Integer widening operators: some preliminary statistics.
In-Reply-To: <4f30e61b8c0c456c06ca18996e3299e9.squirrel@wmail.gradsoft.ua>
References: <4f30e61b8c0c456c06ca18996e3299e9.squirrel@wmail.gradsoft.ua>
Message-ID: <e26afcc9a14273b567743c210ec26ae5.squirrel@wmail.gradsoft.ua>

>

 Results for open JDK:

all bit ands    :       6853
widening operator (semantics)   :       1098
widening operator (syntax)      :       1959

 (i.e. near 1/6 or 1/7 of all bit-ands)

all catchs      :       8404
all ifs :       28494
all integer literals    :       124355
big integer literals(undescores)        :       4066
byte literal    :       1454
catch in finally        :       103
elvis   :       877
instanceof switch       :       318
loop with remove        :       62
multi catch     :       411
object switch   :       1363
rethrow clause  :       3264
string in switch        :       445



> Good day, Bruce.
>
> Some data about integer widening operator:
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000906.html
>
> 3 checks was implemented:
>  1. model check for expression like  ($x && 0xff) or (0xff &  $x) where $x
> must have a type byte (original request). This check named as "widening
> operator (semantics)"
>
> 2. syntax check for expression like  ($x && 0xff) or (0xff &  $x) where $x
> can have any type. This check named as "widening operator (syntax)"
>
>  Example of second but not first:
> <pre>
>   public static short reverseBytes(short s) {
>     return (short) (((s & 0xff) << 8) | ((s & 0xff00) >> 8));
>   }
> </pre>
> <pre>
>        byte[] nounce = new byte[24];
>         for (int i=0;i<8;i++)
>         {
>             nounce[i]=(byte)(ts&0xff);
>             ts=ts>>8;
>             nounce[8+i]=(byte)(sk&0xff);
>             sk=sk>>8;
>         }
> </pre>
>
> 3. count of all expressions with bitwise and. (names as all bit ands)
>
> Than, results for jetty was:
>
> all bit ands    :       121
> widening operator (semantics)   :       10
> widening operator (syntax)      :       20
>
> // some other counts, to compare with:
> rethrow clause  :       34
> string in switch        :       19
>
> hibernate does not use bitwise and at all.
> gwt-users have 2 entries of syntax pattern (actually this is reverseBytes
> function).
>
> Result for jdk I will publish tomorrow, when ones will be ready.
>
> It was preliminary data (one from 3 packages use 'bitwise and') more
> statistics and some analysis will be available throught few days (with
> data about for-s and ERP in dataset).
>
>  Best Regards !
>
>
>
>
>
>
>




From rssh at gradsoft.com.ua  Thu Apr 23 22:44:35 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Fri, 24 Apr 2009 08:44:35 +0300 (EEST)
Subject: Integer widening operators: some preliminary statistics.
In-Reply-To: <ff6a9c820904231818s523b7a27h88992944f2551fd4@mail.gmail.com>
References: <4f30e61b8c0c456c06ca18996e3299e9.squirrel@wmail.gradsoft.ua>
	<ff6a9c820904231818s523b7a27h88992944f2551fd4@mail.gmail.com>
Message-ID: <074c557a3206ff6565d1ed857c4c4491.squirrel@wmail.gradsoft.ua>


> I expect this kind of usage are more common in low level formats.
> Try MINA SSH, OpenDS, etc..
>

 Or, adding ME ssh is a good idea: it small and more or less representative.
Thanks.





From scolebourne at joda.org  Fri Apr 24 07:39:02 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Fri, 24 Apr 2009 15:39:02 +0100
Subject: Syntax patterns: more statistics.
In-Reply-To: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
Message-ID: <4b4f45e00904240739g5b313489x162a005c16cc4ff7@mail.gmail.com>

Ruslan,
I believe that the Elvis check isn't checking for the right thing

          ConditionalExpression(
           EqualityExpression($x,"==",NullLiteral()),
                 $ifNull,  MethodCall($x,$method,$args)) -> true
                 [ violationDiscovered(Elvis, "elvis", $method) ],

This would at first glance appear to match:

 (a == null ? null : a.xxx())

which isn't Elvis.

Elvis is:

 (a == null ? b : a)
 (a != null ? a : b)
 (null == a ? b : a)
 (null != a ? a : b)

Unfortunately, my attempts to encode this failed:
          ConditionalExpression(
           EqualityExpression($x,"==",NullLiteral()),
                 $y, $x) -> true
                 [ violationDiscovered(Elvis, "elvis", $x) ],


On a separate item, the following finds all conditionals:
 define(AllConditionals,coin,"all conditionals",
        BT_TYPE_RULESET,
        ruleset(
          ConditionalExpression($x,$y,$z)
                -> true [ violationDiscovered(AllConditionals, "all
conditionals",$x) ]
         ),
         true
 ),

Stephen


2009/4/20 Ruslan Shevchenko <Ruslan at shevchenko.kiev.ua>:
> Good day, community !
>
> ?I want to share some statistics about java usage patterns, related to
> some of coin-dev proposals.
>
> Main changes from previous post are:
> ?- added counts for 'if' syntax constructions, so we can say, hom many
> ?percents of if's can be eliminated by elvis operator ( [4-5]%)
> ?- added counts for 'catch' syntax constructions, so we can say that
> multicath eliminate 6-8% of all catch clauses.
> ?- added count for big integers integers (where undescore can be
> applicable, I guess this is x: x > 100000 || x < -10000) and for all
> integer literals.
> ? (underscore can be applicable to near 1%)
> ?- added count for object-switch proposal by Ulf Zibis (refining, that
> Left/Right part of expressions are first operand in equalirty expression
> or object in method call)
> ?- added count for rethrow proposal by Mark Mahieu (near 50% of all
> catches in some packages (!) ).
> ?- added count for catches inside finally block. (Is this is a real
> problem [?]).
>
> If anybody whant run checks on own dataset or/and add own check
> definitions: all ?procedure is the same as in my previous letter (see
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001442.html)
> except URL for last version
> ?is
> http://datacenter.gradsoft.ua/public.repository/ua.gradsoft/javachecker/installations/JavaCheckerSourceInstaller-2.5.0p1.jar
>
> Now summary statistics for some well-known packages:
> jetty (web server)
> all catchs ? ? ?: ? ? ? 281
> all ifs : ? ? ? 764
> all integer literals ? ?: ? ? ? 2903
> big integer literals(undescores) ? ? ? ?: ? ? ? 25
> byte literal ? ?: ? ? ? 52
> catch in finally ? ? ? ?: ? ? ? 3
> elvis ? : ? ? ? 43
> instanceof switch ? ? ? : ? ? ? 8
> loop with remove ? ? ? ?: ? ? ? 0
> multi catch ? ? : ? ? ? 22
> object switch ? : ? ? ? 31
> rethrow clause ?: ? ? ? 34
> string in switch ? ? ? ?: ? ? ? 19
> Files:187
>
> gwt-users (google java ajax client library)
> all catchs ? ? ?: ? ? ? 171
> all ifs : ? ? ? 735
> all integer literals ? ?: ? ? ? 2282
> big integer literals(undescores) ? ? ? ?: ? ? ? 24
> byte literal ? ?: ? ? ? 2
> catch in finally ? ? ? ?: ? ? ? 2
> elvis ? : ? ? ? 30
> instanceof switch ? ? ? : ? ? ? 6
> loop with remove ? ? ? ?: ? ? ? 5
> multi catch ? ? : ? ? ? 9
> object switch ? : ? ? ? 27
> rethrow clause ?: ? ? ? 84
> string in switch ? ? ? ?: ? ? ? 10
> Files:920
>
> hibernate (ORM toolkit)
> all catchs ? ? ?: ? ? ? 650
> all ifs : ? ? ? 2410
> all integer literals ? ?: ? ? ? 3240
> big integer literals(undescores) ? ? ? ?: ? ? ? 12
> byte literal ? ?: ? ? ? 1
> catch in finally ? ? ? ?: ? ? ? 27
> elvis ? : ? ? ? 182
> instanceof switch ? ? ? : ? ? ? 28
> loop with remove ? ? ? ?: ? ? ? 12
> multi catch ? ? : ? ? ? 25
> object switch ? : ? ? ? 94
> rethrow clause ?: ? ? ? 450
> string in switch ? ? ? ?: ? ? ? 86
> Files:1372
>
> openjdk7 (standard java library)
> all catchs ? ? ?: ? ? ? 8404
> all ifs : ? ? ? 28494
> all integer literals ? ?: ? ? ? 124356
> big integer literals(undescores) ? ? ? ?: ? ? ? 4066
> byte literal ? ?: ? ? ? 1454
> catch in finally ? ? ? ?: ? ? ? 103
> elvis ? : ? ? ? 877
> instanceof switch ? ? ? : ? ? ? 318
> loop with remove ? ? ? ?: ? ? ? 62
> multi catch ? ? : ? ? ? 411
> object switch ? : ? ? ? 1363
> rethrow clause ?: ? ? ? 3264
> string in switch ? ? ? ?: ? ? ? 445
> Files:9252
>
> Hope, this data will be useful in some cases.
> Regards !
>
>
>
>


From rssh at gradsoft.com.ua  Fri Apr 24 08:20:17 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Fri, 24 Apr 2009 18:20:17 +0300 (EEST)
Subject: Syntax patterns: more statistics.
In-Reply-To: <4b4f45e00904240739g5b313489x162a005c16cc4ff7@mail.gmail.com>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240739g5b313489x162a005c16cc4ff7@mail.gmail.com>
Message-ID: <90e12e623b34e8bdd2b9dc8c54ed6e3b.squirrel@wmail.gradsoft.ua>

> Ruslan,
> I believe that the Elvis check isn't checking for the right thing
>
>           ConditionalExpression(
>            EqualityExpression($x,"==",NullLiteral()),
>                  $ifNull,  MethodCall($x,$method,$args)) -> true
>                  [ violationDiscovered(Elvis, "elvis", $method) ],
>

> This would at first glance appear to match:
>
>  (a == null ? null : a.xxx())
>

 This is (a==null ?  b : a.xxx())

Also note, that check elvis contains 4 rules
(starting fromn line 112, end from line 131 in )
http://redmine.gradsoft.ua/repositories/entry/javachecker/trunk/JavaChecker/etc/checkers_coin.def

You cite only one.

(Under elvis I understand
http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000047.html)
where the most generic is conditional expression.

What you guess:
(a == null ? null : a.xxx()) is
           ConditionalExpression(
              EqualityExpression($x,"==",NullLiteral()),
                 NullLiteral(),  MethodCall($x,$method,$args)) -> true
                  [ violationDiscovered(Elvis, "elvis", $method) ],


> which isn't Elvis.
>
> Elvis is:
>
>  (a == null ? b : a)
>  (a != null ? a : b)
>  (null == a ? b : a)
>  (null != a ? a : b)
>

 //
 Let's create this version.

> Unfortunately, my attempts to encode this failed:
>           ConditionalExpression(
>            EqualityExpression($x,"==",NullLiteral()),
>                  $y, $x) -> true
>                  [ violationDiscovered(Elvis, "elvis", $x) ],
>
>
> On a separate item, the following finds all conditionals:
>  define(AllConditionals,coin,"all conditionals",
>         BT_TYPE_RULESET,
>         ruleset(
>           ConditionalExpression($x,$y,$z)
>                 -> true [ violationDiscovered(AllConditionals, "all
> conditionals",$x) ]
>          ),
>          true
>  ),
>

 Sorry, can you attach modified checkers_coin.def  ?
(or diff)

>           ConditionalExpression(
>            EqualityExpression($x,"==",NullLiteral()),
>                  $y, $x) -> true
>                  [ violationDiscovered(Elvis, "elvis", $x) ],

 is correct (in first look), but not complete

//Probably, you can place rule inside ruleset of AllConditional to achieve
such effect, or may be write AllConditionals instead Elvis in violation
discovered

To say something concrete, I need to see full define term.
I. e. starts from define( ....  and up to ,)

//btw, If you agree, I can give you write access to svn, create file
checkers_elvis.def, than will  able see you changes and point on errors
automatically after commits.



> Stephen
>
>
> 2009/4/20 Ruslan Shevchenko <Ruslan at shevchenko.kiev.ua>:
>> Good day, community !
>>
>> ?I want to share some statistics about java usage patterns, related to
>> some of coin-dev proposals.
>>
>> Main changes from previous post are:
>> ?- added counts for 'if' syntax constructions, so we can say, hom many
>> ?percents of if's can be eliminated by elvis operator ( [4-5]%)
>> ?- added counts for 'catch' syntax constructions, so we can say that
>> multicath eliminate 6-8% of all catch clauses.
>> ?- added count for big integers integers (where undescore can be
>> applicable, I guess this is x: x > 100000 || x < -10000) and for all
>> integer literals.
>> ? (underscore can be applicable to near 1%)
>> ?- added count for object-switch proposal by Ulf Zibis (refining, that
>> Left/Right part of expressions are first operand in equalirty expression
>> or object in method call)
>> ?- added count for rethrow proposal by Mark Mahieu (near 50% of all
>> catches in some packages (!) ).
>> ?- added count for catches inside finally block. (Is this is a real
>> problem [?]).
>>
>> If anybody whant run checks on own dataset or/and add own check
>> definitions: all ?procedure is the same as in my previous letter (see
>> http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001442.html)
>> except URL for last version
>> ?is
>> http://datacenter.gradsoft.ua/public.repository/ua.gradsoft/javachecker/installations/JavaCheckerSourceInstaller-2.5.0p1.jar
>>
>> Now summary statistics for some well-known packages:
>> jetty (web server)
>> all catchs ? ? ?: ? ? ? 281
>> all ifs : ? ? ? 764
>> all integer literals ? ?: ? ? ? 2903
>> big integer literals(undescores) ? ? ? ?: ? ? ? 25
>> byte literal ? ?: ? ? ? 52
>> catch in finally ? ? ? ?: ? ? ? 3
>> elvis ? : ? ? ? 43
>> instanceof switch ? ? ? : ? ? ? 8
>> loop with remove ? ? ? ?: ? ? ? 0
>> multi catch ? ? : ? ? ? 22
>> object switch ? : ? ? ? 31
>> rethrow clause ?: ? ? ? 34
>> string in switch ? ? ? ?: ? ? ? 19
>> Files:187
>>
>> gwt-users (google java ajax client library)
>> all catchs ? ? ?: ? ? ? 171
>> all ifs : ? ? ? 735
>> all integer literals ? ?: ? ? ? 2282
>> big integer literals(undescores) ? ? ? ?: ? ? ? 24
>> byte literal ? ?: ? ? ? 2
>> catch in finally ? ? ? ?: ? ? ? 2
>> elvis ? : ? ? ? 30
>> instanceof switch ? ? ? : ? ? ? 6
>> loop with remove ? ? ? ?: ? ? ? 5
>> multi catch ? ? : ? ? ? 9
>> object switch ? : ? ? ? 27
>> rethrow clause ?: ? ? ? 84
>> string in switch ? ? ? ?: ? ? ? 10
>> Files:920
>>
>> hibernate (ORM toolkit)
>> all catchs ? ? ?: ? ? ? 650
>> all ifs : ? ? ? 2410
>> all integer literals ? ?: ? ? ? 3240
>> big integer literals(undescores) ? ? ? ?: ? ? ? 12
>> byte literal ? ?: ? ? ? 1
>> catch in finally ? ? ? ?: ? ? ? 27
>> elvis ? : ? ? ? 182
>> instanceof switch ? ? ? : ? ? ? 28
>> loop with remove ? ? ? ?: ? ? ? 12
>> multi catch ? ? : ? ? ? 25
>> object switch ? : ? ? ? 94
>> rethrow clause ?: ? ? ? 450
>> string in switch ? ? ? ?: ? ? ? 86
>> Files:1372
>>
>> openjdk7 (standard java library)
>> all catchs ? ? ?: ? ? ? 8404
>> all ifs : ? ? ? 28494
>> all integer literals ? ?: ? ? ? 124356
>> big integer literals(undescores) ? ? ? ?: ? ? ? 4066
>> byte literal ? ?: ? ? ? 1454
>> catch in finally ? ? ? ?: ? ? ? 103
>> elvis ? : ? ? ? 877
>> instanceof switch ? ? ? : ? ? ? 318
>> loop with remove ? ? ? ?: ? ? ? 62
>> multi catch ? ? : ? ? ? 411
>> object switch ? : ? ? ? 1363
>> rethrow clause ?: ? ? ? 3264
>> string in switch ? ? ? ?: ? ? ? 445
>> Files:9252
>>
>> Hope, this data will be useful in some cases.
>> Regards !
>>
>>
>>
>>
>
>




From rssh at gradsoft.com.ua  Fri Apr 24 08:58:58 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Fri, 24 Apr 2009 18:58:58 +0300 (EEST)
Subject: elvis pattern refinement (was Syntax patterns)
In-Reply-To: <90e12e623b34e8bdd2b9dc8c54ed6e3b.squirrel@wmail.gradsoft.ua>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240739g5b313489x162a005c16cc4ff7@mail.gmail.com>
	<90e12e623b34e8bdd2b9dc8c54ed6e3b.squirrel@wmail.gradsoft.ua>
Message-ID: <cac212df65add79bf0ec412bb05348d5.squirrel@wmail.gradsoft.ua>

Hi, Stephen

//At first - in previous letter I forgott to say thanks for refinement.

I just commited elvis1 definition, which is exaclty what you write.

http://redmine.gradsoft.ua/repositories/entry/javachecker/trunk/JavaChecker/etc/checkers_elvis.def

But I mean this is incorrect, becouse it does not cover case of
'null-safe method call' (which is often used for describing elvis).
So, for example, in jetty we see only one matching for four patterns.

More - rereading  proposal, I see that I implement check for 'safe method
call' but in proposal we have 'safe index; safe field access, .. etc)

So, let's explicit define all aviable patterns.

First question: is 'safe-method call': i. e.
(a==null ? b : a.method(...)) pattern is correct ?
// Which can be rewritten as    a?.method() ?: b








From scolebourne at joda.org  Fri Apr 24 09:15:11 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Fri, 24 Apr 2009 17:15:11 +0100
Subject: Syntax patterns: more statistics.
In-Reply-To: <90e12e623b34e8bdd2b9dc8c54ed6e3b.squirrel@wmail.gradsoft.ua>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240739g5b313489x162a005c16cc4ff7@mail.gmail.com>
	<90e12e623b34e8bdd2b9dc8c54ed6e3b.squirrel@wmail.gradsoft.ua>
Message-ID: <4b4f45e00904240915p1ef7337h154ad887610f1108@mail.gmail.com>

2009/4/24 Ruslan Shevchenko <rssh at gradsoft.com.ua>:
> To say something concrete, I need to see full define term.
> I. e. starts from define( .... ?and up to ,)

This is what I tried:

 define(Elvis,coin,"elvis",
        BT_TYPE_RULESET,
        ruleset(
          ConditionalExpression(
           EqualityExpression($x,"==",NullLiteral()),
                 $y,  $x) -> true
                 [ violationDiscovered(Elvis, "elvis", $method) ],
... similar for the other three
        ),true),

But it didn't work.


The second one was to find all conditionals - aiming to find any and
all conditional statements:

 define(AllConditionals,coin,"all conditionals",
        BT_TYPE_RULESET,
        ruleset(
          ConditionalExpression($x,$y,$z)
                -> true [ violationDiscovered(AllConditionals, "all
conditionals",$x) ]
         ),
         true
 ),

That is working fine.


I should also note that the iterator remove() only catches remove()
within a while-statement, and not within an iterator-driven
for-statement.

Stephen


From rssh at gradsoft.com.ua  Fri Apr 24 09:33:01 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Fri, 24 Apr 2009 19:33:01 +0300 (EEST)
Subject: Syntax patterns: more statistics.
In-Reply-To: <4b4f45e00904240915p1ef7337h154ad887610f1108@mail.gmail.com>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240739g5b313489x162a005c16cc4ff7@mail.gmail.com>
	<90e12e623b34e8bdd2b9dc8c54ed6e3b.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240915p1ef7337h154ad887610f1108@mail.gmail.com>
Message-ID: <8a12b3c18bc0298cd3ca3521b5244462.squirrel@wmail.gradsoft.ua>

> 2009/4/24 Ruslan Shevchenko <rssh at gradsoft.com.ua>:
>> To say something concrete, I need to see full define term.
>> I. e. starts from define( .... ?and up to ,)
>
> This is what I tried:
>
>  define(Elvis,coin,"elvis",
>         BT_TYPE_RULESET,
>         ruleset(
>           ConditionalExpression(
>            EqualityExpression($x,"==",NullLiteral()),
>                  $y,  $x) -> true
>                  [ violationDiscovered(Elvis, "elvis", $method) ],
> ... similar for the other three
>         ),true),
>
> But it didn't work.
>
>

 $method in violationDiscovered now is free variable, which have no line and
number information.

// how this work inside -- javachecker retrieve location information from
first identifier, found inside term in third parameter.
So, better write something in style
>  define(Elvis,coin,"elvis",
>         BT_TYPE_RULESET,
>         ruleset(
>           ConditionalExpression(
>            EqualityExpression($x,"==",NullLiteral()),
>                  $y,  $x) -> true
>                  [ violationDiscovered(Elvis, "elvis", $x) ],
> ... similar for the other three
>         ),true),

And what mean 'does not work' ?
Let's define some common small dataset.



> The second one was to find all conditionals - aiming to find any and
> all conditional statements:
>
>  define(AllConditionals,coin,"all conditionals",
>         BT_TYPE_RULESET,
>         ruleset(
>           ConditionalExpression($x,$y,$z)
>                 -> true [ violationDiscovered(AllConditionals, "all
> conditionals",$x) ]
>          ),
>          true
>  ),
>
> That is working fine.
>
>
> I should also note that the iterator remove() only catches remove()
> within a while-statement, and not within an iterator-driven
> for-statement.

Yes. Will be fixed.  (I guess iterator-driven for statement does not exist
in life and usually written as while, but better check all, of course.)

>
> Stephen
>
>




From scolebourne at joda.org  Fri Apr 24 09:40:36 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Fri, 24 Apr 2009 17:40:36 +0100
Subject: Syntax patterns: more statistics.
In-Reply-To: <8a12b3c18bc0298cd3ca3521b5244462.squirrel@wmail.gradsoft.ua>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240739g5b313489x162a005c16cc4ff7@mail.gmail.com>
	<90e12e623b34e8bdd2b9dc8c54ed6e3b.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240915p1ef7337h154ad887610f1108@mail.gmail.com>
	<8a12b3c18bc0298cd3ca3521b5244462.squirrel@wmail.gradsoft.ua>
Message-ID: <4b4f45e00904240940i254c310chb2eaebee63f53bfe@mail.gmail.com>

2009/4/24 Ruslan Shevchenko <rssh at gradsoft.com.ua>:
> And what mean 'does not work' ?
> Let's define some common small dataset.

These are the patterns that need to be identified for Elvis:
  (a == null ? b : a)
  (a != null ? a : b)
  (null == a ? b : a)
  (null != a ? a : b)

where a is any expression (occurs twice and is exactly the same in
both cases), and b is any expression. Ideally, these same patterns
should also be matched as if-statements, but that will be a lot
harder/impossible.

The null-safe operator patterns are more complex.

>> I should also note that the iterator remove() only catches remove()
>> within a while-statement, and not within an iterator-driven
>> for-statement.
>
> Yes. Will be fixed.
Thanks

> ?(I guess iterator-driven for statement does not exist
> in life and usually written as while, but better check all, of course.)

Not so. About 50% of the remove() are in while-statement and 50% in
for-statement in the sourcebase I'm evaluating.

Stephen


From scolebourne at joda.org  Fri Apr 24 09:45:21 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Fri, 24 Apr 2009 17:45:21 +0100
Subject: elvis pattern refinement (was Syntax patterns)
In-Reply-To: <cac212df65add79bf0ec412bb05348d5.squirrel@wmail.gradsoft.ua>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240739g5b313489x162a005c16cc4ff7@mail.gmail.com>
	<90e12e623b34e8bdd2b9dc8c54ed6e3b.squirrel@wmail.gradsoft.ua>
	<cac212df65add79bf0ec412bb05348d5.squirrel@wmail.gradsoft.ua>
Message-ID: <4b4f45e00904240945o4630227rc75996cad3d7fba4@mail.gmail.com>

2009/4/24 Ruslan Shevchenko <rssh at gradsoft.com.ua>:
> But I mean this is incorrect, becouse it does not cover case of
> 'null-safe method call' (which is often used for describing elvis).

Officially, 'Elvis' just refers to the 'default if null' pattern. The
other operators are the 'null-safe' operators.

> So, for example, in jetty we see only one matching for four patterns.
> More - rereading ?proposal, I see that I implement check for 'safe method
> call' but in proposal we have 'safe index; safe field access, .. etc)
>
> So, let's explicit define all aviable patterns.
>
> First question: is 'safe-method call': i. e.
> (a==null ? b : a.method(...)) pattern is correct ?
> // Which can be rewritten as ? ?a?.method() ?: b

If I were writing Java today without the null-safe operators, then I
would typically use an if-statement:

if (foo != null) {
  foo.process();
}

Bar bar = null;
if (foo != null) {
  bar = foo.process();
}

Stephen


From rssh at gradsoft.com.ua  Fri Apr 24 09:57:28 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Fri, 24 Apr 2009 19:57:28 +0300 (EEST)
Subject: Syntax patterns: more statistics.
In-Reply-To: <4b4f45e00904240940i254c310chb2eaebee63f53bfe@mail.gmail.com>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240739g5b313489x162a005c16cc4ff7@mail.gmail.com>
	<90e12e623b34e8bdd2b9dc8c54ed6e3b.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240915p1ef7337h154ad887610f1108@mail.gmail.com>
	<8a12b3c18bc0298cd3ca3521b5244462.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240940i254c310chb2eaebee63f53bfe@mail.gmail.com>
Message-ID: <604e8bb368364a76e8df1e7865f91527.squirrel@wmail.gradsoft.ua>

> 2009/4/24 Ruslan Shevchenko <rssh at gradsoft.com.ua>:
>> And what mean 'does not work' ?
>> Let's define some common small dataset.
>
> These are the patterns that need to be identified for Elvis:
>   (a == null ? b : a)
>   (a != null ? a : b)
>   (null == a ? b : a)
>   (null != a ? a : b)
>
> where a is any expression (occurs twice and is exactly the same in
> both cases), and b is any expression. Ideally, these same patterns
> should also be matched as if-statements, but that will be a lot
> harder/impossible.
>

 Under common small dataset I mean sourcebase.
I. e. while you think that such patterns does not works ?
May be they absent in you sourcebase. (I just scan jetty sources for such
patterns - only one matching per 187 files ). So 'clear elvis' is
extremely rare.

So, let's define some common sources (well-known packet or just archive). 
Show me, where this patterns is skipped and I will be able to debug this.



> The null-safe operator patterns are more complex.
>
>>> I should also note that the iterator remove() only catches remove()
>>> within a while-statement, and not within an iterator-driven
>>> for-statement.
>>
>> Yes. Will be fixed.
> Thanks
>
>> ?(I guess iterator-driven for statement does not exist
>> in life and usually written as while, but better check all, of course.)
>
> Not so. About 50% of the remove() are in while-statement and 50% in
> for-statement in the sourcebase I'm evaluating.
>

surprised ;)

> Stephen
>
>




From ali.ebrahimi1781 at gmail.com  Fri Apr 24 10:02:25 2009
From: ali.ebrahimi1781 at gmail.com (Ali Ebrahimi)
Date: Fri, 24 Apr 2009 21:32:25 +0430
Subject: My wishlist and Ideas for java 7 as java developer
Message-ID: <5ab441490904241002r3ac43f59g327ffe88bd63b7b8@mail.gmail.com>

Hi All,
java needs cool features.

My wishlist and ideas for java 7:

1) switch on objects.

switch(obj){
      case *String str:* println("obj instance of String and *str* result of
cast (String)obj"); break;  *// instanceof case*
      case *obj2 :* println("obj  equals obj2"); break;     // *equals case*
     ....
}

a few rules for this statement.
1) subclasses must be apears after superclass
class Base{}
clase SubClass extends Base{}

switch(obj){
  case  Base b:  dowithBase(b); ....     // Compile error or Warning
  case SubClasss s: dowithSub(s);
}
this rule anagulus to rules for catch clauses
....

I very like this switch statement compared with all proposed proposals to
list in this case. I want to see this in java 7.

2) function types(method references) base on Method Handles(Thanks john rose
for your great work).
In other words, add language support for Method Handles.
sample:

  public static void each(Collection<?> c, *MethodHandle mh*) {
      for(Object element:c) {
          *mh.invoke(element);*
      }
  }
  public static void sayHello(Object message) {
      System.out.println("hello "+message);
  }
  public static void main(String[] args) {
*      MethodType methodType=MethodType.make(void.class, Object.class);
      MethodHandle
**myFunc**=MethodHandles.findStatic(MethodHandleTest.class,
"sayHello", methodType);
*
      List list=Arrays.asList("item1", "item2");
      each(list, *myFunc*);
  }

with language support for Method Handles(function types) code would be as
below :

  public static void each(Collection<?> c, *(Object)=>void* method) {
// or  void(Object)
      for(Object element:c) {
          method.invoke(element);  or method(element)
      }
  }
  public static void sayHello(Object message) {
      System.out.println("hello "+message);
  }

  public static void main(String[] args) {
      *(Object)=>void myFunc = MyClass#sayHello(Object);*
      List list=Arrays.asList("item1", "item2");
      each(list, *myFunc*);
  }

3) *Property support with Automatic Binding Support*
sample:
class Person{
   //form1: with Compiler aware Annotation(As Override)
   *private @**Property** String name;*
   // Or
   // form2:
   *property **String name;*

}

Translated to:
class Person{
*public final Property<String> Name = Property.<String>make();*

public String getName(){
   return this.name.getValue();
}

public void setName(String name){
   this.name.setValue(name);
}
}

how to use:
Person person = new Person();
person*.name = "Ali";*  //Translated to person.setName("Ali");
*String PName = *person*.name;* //Translated to String PName = person.getName();

*Property<String> nameProperty = *person*.Name;* // access property object


   - *Adding auto binding support:*


With only one bind method in Property class

*public void bind(Propery<T> dest){ bind(dest,false)}

**public void bind(Propery<T> dest, boolean inverse){ .....} *

usage :
//UI class
class TextFieldUI extends ...{
     property String text;
}

Person person = new Person();
person.name = "Ali";

TextFieldUI nameUI = new TextFieldUI();
*// Uni-directional binding
nameUI.Text.bind(person.Name); // Or bind(nameUI.Text,person.Name);

// bi-directional binding
nameUI.Text.bind(person.Name,true); // bind(nameUI.Text,person.Name,true**);*


   - *Validation support:*

By adding one method to Property class

*public void addValidator(Validator validator){ ...}*


   - *Triger or Change Listener support*

By adding one method to Property class

*public void addTriger(ChangeListener changeListener){ ...} // or
add**ChangeListener*


Propery class thing like as below:

class Property<T>{

private T value;

public T getValue(){
   return value;
}
public void setValue(T newVal){
   T old = this.value;
   if( !old.equals(newVal)){
      if(validate(newVal)){
          this.value = newVal;
          valueChanged(old,newVal);
      }
   }
}

private Set<Property<T>> dependents;
private Set<Validator> validators;
private Set<ChangeListener> trigers;

private valueChanged(K oldV, K newV){
   fireTrigers(oldV,newV);
   propagateToDependencies();
}
private void fireTrigers(K oldV, K newV){
   if(trigers == null || trigers.size() == 0) return;
   for(ChangeListener triger:trigers){
      triger.onChange(oldV,newV);
   }
}
private void propagateToDependendts(){
   if(dependents == null || dependents.size() == 0) return;
   for(Property dependentP:dependents){
      depedentP.setValue(this.value);
   }
}
public void addTriger(ChangeListener changeListener){
   if(trigers == null) trigers=new HashSet<ChangeListener>();
   trigers.add(changeListener);
}
public void removeTriger(ChangeListener changeListener){
   if(trigers != null) trigers.remove(changeListener);
}
public void bind(Property<T> dest){ bind(dest,false);}
public void bind(Property<T> dest, boolean inverse){
    dest.addDependency(this);
    if(inverse) this.addDependency(dest)
}

public void addDependent(Property<T> dependentProperty){
   if(dependents == null) dependets = new HashSet<Property>();
   dependencts.add(dependentProperty);
}
public void removeDependent(Property<T> dependentProperty){
   if(dependents != null) dependents.remove(dependentProperty);
}

public void unBind(Property<T> dest){
    dest.removeDependet(this);
}
...

}

Advantages
1) comprehensive property support
2) Non-Reflection base: do'nt use reflection therefore high perfomance
3) Minimum language change;
....

And many other ideas.

Best Regards
Ali Ebrahimi


From ali.ebrahimi1781 at gmail.com  Fri Apr 24 10:08:04 2009
From: ali.ebrahimi1781 at gmail.com (Ali Ebrahimi)
Date: Fri, 24 Apr 2009 21:38:04 +0430
Subject: My wishlist and Ideas for java 7 as java developer
In-Reply-To: <5ab441490904241002r3ac43f59g327ffe88bd63b7b8@mail.gmail.com>
References: <5ab441490904241002r3ac43f59g327ffe88bd63b7b8@mail.gmail.com>
Message-ID: <5ab441490904241008l54a8746bi8154b86fc1344cde@mail.gmail.com>

Hi All,
java needs cool features.

My wishlist and ideas for java 7:

1) switch on objects.

switch(obj){
      case String str: println("obj instance of String and str result of
cast (String)obj"); break;  // instanceof case
      case obj2 : println("obj  equals obj2"); break;     // equals case
     ....
}

a few rules for this statement.
1) subclasses must be apears after superclass
class Base{}
clase SubClass extends Base{}

switch(obj){
  case  Base b:  dowithBase(b); ....     // Compile error or Warning
  case SubClasss s: dowithSub(s);
}
this rule anagulus to rules for catch clauses
....

I very like this switch statement compared with all proposed proposals to
list in this case. I want to see this in java 7.

2) function types(method references) base on Method Handles(Thanks john rose
for your great work).
In other words, add language support for Method Handles.
sample:

  public static void each(Collection<?> c, MethodHandle mh) {
      for(Object element:c) {

          mh.invoke(element);
      }
  }
  public static void sayHello(Object message) {
      System.out.println("hello "+message);
  }
  public static void main(String[] args) {
      MethodType methodType=MethodType.make(void.class, Object.class);

      MethodHandle
myFunc=MethodHandles.findStatic(MethodHandleTest.class, "sayHello",
methodType);

      List list=Arrays.asList("item1", "item2");

      each(list, myFunc);
  }

with language support for Method Handles(function types) code would be as
below :

  public static void each(Collection<?> c, (Object)=>void method) { //
or  void(Object)
      for(Object element:c) {
          method.invoke(element);  or method(element)

      }
  }
  public static void sayHello(Object message) {
      System.out.println("hello "+message);
  }

  public static void main(String[] args) {
      (Object)=>void myFunc = MyClass#sayHello(Object);

      List list=Arrays.asList("item1", "item2");
      each(list, myFunc);
  }

3) Property support with Automatic Binding Support
sample:
class Person{
   //form1: with Compiler aware Annotation(As Override)
   private @Property String name;
   // Or

   // form2:
   property String name;

}

Translated to:
class Person{

public final Property<String> Name = Property.<String>make();

public String getName(){
   return this.name.getValue();
}

public void setName(String name){
   this.name.setValue(name);
}
}

how to use:
Person person = new Person();

person.name = "Ali";  //Translated to person.setName("Ali");

String PName = person.name; //Translated to String PName = person.getName();


Property<String> nameProperty = person.Name; // access property object


   - Adding auto binding support:



With only one bind method in Property class

public void bind(Propery<T> dest){ bind(dest,false)}

public void bind(Propery<T> dest, boolean inverse){ .....}

usage :
//UI class
class TextFieldUI extends ...{
     property String text;
}

Person person = new Person();
person.name = "Ali";

TextFieldUI nameUI = new TextFieldUI();

// Uni-directional binding
nameUI.Text.bind(person.Name); // Or bind(nameUI.Text,person.Name);

// bi-directional binding
nameUI.Text.bind(person.Name,true); // bind(nameUI.Text,person.Name,true);



   - Validation support:

By adding one method to Property class

public void addValidator(Validator validator){ ...}



   - Triger or Change Listener support

By adding one method to Property class

public void addTriger(ChangeListener changeListener){ ...} // or
addChangeListener



Propery class thing like as below:

class Property<T>{

private T value;

public T getValue(){
   return value;
}
public void setValue(T newVal){

   T old = this.value;
   if( !old.equals(newVal)){

      if(validate(newVal)){
          this.value = newVal;

          valueChanged(old,newVal);
      }
   }
}

private Set<Property<T>> dependents;
private Set<Validator> validators;
private Set<ChangeListener> trigers;


private valueChanged(K oldV, K newV){
   fireTrigers(oldV,newV);
   propagateToDependencies();
}
private void fireTrigers(K oldV, K newV){

   if(trigers == null || trigers.size() == 0) return;
   for(ChangeListener triger:trigers){
      triger.onChange(oldV,newV);
   }
}
private void propagateToDependendts(){
   if(dependents == null || dependents.size() == 0) return;
   for(Property dependentP:dependents){

      depedentP.setValue(this.value);
   }
}
public void addTriger(ChangeListener changeListener){

   if(trigers == null) trigers=new HashSet<ChangeListener>();

   trigers.add(changeListener);
}
public void removeTriger(ChangeListener changeListener){

   if(trigers != null) trigers.remove(changeListener);

}
public void bind(Property<T> dest){ bind(dest,false);}
public void bind(Property<T> dest, boolean inverse){
    dest.addDependency(this);
    if(inverse) this.addDependency(dest)

}

public void addDependent(Property<T> dependentProperty){

   if(dependents == null) dependets = new HashSet<Property>();

   dependencts.add(dependentProperty);

}
public void removeDependent(Property<T> dependentProperty){

   if(dependents != null) dependents.remove(dependentProperty);

}

public void unBind(Property<T> dest){
    dest.removeDependet(this);

}
...

}

Advantages
1) comprehensive property support
2) Non-Reflection base: do'nt use reflection therefore high perfomance

3) Minimum language change;
....

And many other ideas.

Best Regards
Ali Ebrahimi


From rssh at gradsoft.com.ua  Fri Apr 24 10:08:19 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Fri, 24 Apr 2009 20:08:19 +0300 (EEST)
Subject: elvis pattern refinement (was Syntax patterns)
In-Reply-To: <4b4f45e00904240945o4630227rc75996cad3d7fba4@mail.gmail.com>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240739g5b313489x162a005c16cc4ff7@mail.gmail.com>
	<90e12e623b34e8bdd2b9dc8c54ed6e3b.squirrel@wmail.gradsoft.ua>
	<cac212df65add79bf0ec412bb05348d5.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240945o4630227rc75996cad3d7fba4@mail.gmail.com>
Message-ID: <152e5a7a9f1cc3e929fe730e7913e36b.squirrel@wmail.gradsoft.ua>

> 2009/4/24 Ruslan Shevchenko <rssh at gradsoft.com.ua>:
>> But I mean this is incorrect, becouse it does not cover case of
>> 'null-safe method call' (which is often used for describing elvis).
>
> Officially, 'Elvis' just refers to the 'default if null' pattern. The
> other operators are the 'null-safe' operators.
>

In such case we need rename one. What I count was 'optimization of method
calls, via operators defined in elvis proposal', not occurences of elvis.


>> So, for example, in jetty we see only one matching for four patterns.
>> More - rereading ?proposal, I see that I implement check for 'safe
>> method
>> call' but in proposal we have 'safe index; safe field access, .. etc)
>>
>> So, let's explicit define all aviable patterns.
>>
>> First question: is 'safe-method call': i. e.
>> (a==null ? b : a.method(...)) pattern is correct ?
>> // Which can be rewritten as ? ?a?.method() ?: b
>


> If I were writing Java today without the null-safe operators, then I
> would typically use an if-statement:
>
> if (foo != null) {
>   foo.process();
> }
>
> Bar bar = null;
> if (foo != null) {
>   bar = foo.process();
> }
>
> Stephen
>

 Great - you found hole, I just forgot, that IfStatement already can be
optimized.
// will start write such pattern in Elvis1 now.

But let's return to original question:

is 'safe-method call': i. e. optimization of pattern
  (a==null ? b : a.method(...))
  // Which can be rewritten as
    a?.method() ?: b
  using operators, defined in elvis, can be counted as entry for
optimization as result of elvis proposal, or not ?


>




From scolebourne at joda.org  Fri Apr 24 10:25:48 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Fri, 24 Apr 2009 18:25:48 +0100
Subject: Statistics for E-Commerce system
Message-ID: <4b4f45e00904241025k6ccd948i5b0d646a0cc2c63b@mail.gmail.com>

1.3 million LOC
Old sourcebase, lots of refactoring down the years
Java EE, Servlets but not EJB
Two parts - low level utilities, and main E-commerce codebase

Low level utilities
-------------------------
all catchs             : 549
all conditionals       : 297
all ifs                : 1521
all integer literals   : 4863
big integer literals(undescores): 326
byte literal           : 0
catch in finally       : 14
elvis                  : 86  --> correct value 36
instanceof switch      : 27
loop with remove       : 5  --> correct value 33
multi catch            : 31
object switch          : 81
rethrow clause         : 271
string in switch       : 23
Files:564

 while \(.+?\.hasNext\(\)\)
all hasNext() while    : 39
 for \(Iterator
all iterator() for     : 68
 for \(int
all int for            : 375
 for \(
all for                : 631

Elvis-conditional = 36/297 = 12.1%
Loop-remove       = 33/631 =  5.2%
Multi-catch         = 31/549 = 5.6%


Main E-Commerce system
---------------------------------------
(counted in three parts to avoid out of memory in the tool, and to
demonstrate how different types of code affect the results)
Main code (most of the business logic:
all catchs             : 2592
all conditionals       : 2185
all ifs                : 7431
all integer literals   : 45473
big integer literals(undescores): 5738
byte literal           : 0
catch in finally       : 35
elvis                  : 600  --> correct value ?
instanceof switch      : 159
loop with remove       : 88  --> correct value 430
multi catch            : 39
object switch          : 379
rethrow clause         : 859
string in switch       : 117
Files:5822

Sub part 1 (code generated beans):
all catchs             : 753
all conditionals       : 10244
all ifs                : 4955
all integer literals   : 145405
big integer literals(undescores) : 25957
byte literal           : 0
catch in finally       : 0
elvis                  : 4058  --> correct value, probably 0
instanceof switch      : 9
loop with remove       : 0  --> correct value 0
multi catch            : 0
object switch          : 15
rethrow clause         : 1
string in switch       : 0
Files:1553

Sub part 2 (presentation layer):
all catchs             : 370
all conditionals       : 366
all ifs                : 1622
all integer literals   : 2632
big integer literals(undescores) : 39
byte literal           : 0
catch in finally       : 6
elvis                  : 33
instanceof switch      : 47
loop with remove       : 8  --> correct value 20
multi catch            : 0
object switch          : 112
rethrow clause         : 61
string in switch       : 35
Files:1160

 while \(.+?\.hasNext\(\)\)
all hasNext() while    : 256
 for \(Iterator
all iterator() for     : 536
 for \(int
all int for            : 4530 *not all loops around lists
 for \(
all for                : 8248 *not all loops around lists

Elvis-conditional = ?/2185 =
Loop-with-remove  = 450/8248 = 5.5%
Multi-catch  = 39/3715 = 1.0%


The Elvis number currently needs manual work to calculate, so I passed
for the size of the main sourcebase. However, 12% of all conditionals
in the low level library is a reasonable number of hits.

The loop-with-remove is between 5 and 5.5% (of all loops, which
includes loops around things other than lists, like strings). I can't
easily determine how often the loop index is needed, or whether it is
the first/last loop, each of which would push up the %age.

Multi-catch has about 1% of all catch statements in the main
E-Commerce, but 5.6% in the low level libraries. This perhaps
indicates where the sweet spot for the feature is - libraries and
frameworks.

Stephen


From scolebourne at joda.org  Fri Apr 24 10:28:33 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Fri, 24 Apr 2009 18:28:33 +0100
Subject: elvis pattern refinement (was Syntax patterns)
In-Reply-To: <152e5a7a9f1cc3e929fe730e7913e36b.squirrel@wmail.gradsoft.ua>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240739g5b313489x162a005c16cc4ff7@mail.gmail.com>
	<90e12e623b34e8bdd2b9dc8c54ed6e3b.squirrel@wmail.gradsoft.ua>
	<cac212df65add79bf0ec412bb05348d5.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240945o4630227rc75996cad3d7fba4@mail.gmail.com>
	<152e5a7a9f1cc3e929fe730e7913e36b.squirrel@wmail.gradsoft.ua>
Message-ID: <4b4f45e00904241028t140786bfr53ccf0c3e2ed99ff@mail.gmail.com>

2009/4/24 Ruslan Shevchenko <rssh at gradsoft.com.ua>:
> But let's return to original question:
>
> is 'safe-method call': i. e. optimization of pattern
> ?(a==null ? b : a.method(...))
> ?// Which can be rewritten as
> ? ?a?.method() ?: b
> ?using operators, defined in elvis, can be counted as entry for
> optimization as result of elvis proposal, or not ?

This could be coded as

  a?.method() ?: b

however, that would be semantically different in meaning (as now b is
returned if method() returns null, which wasn't originally the case)

Thus, this construct is invalid for Elvis, Null-safe and the
combination of the two.

Stephen


From ali.ebrahimi1781 at gmail.com  Fri Apr 24 10:44:55 2009
From: ali.ebrahimi1781 at gmail.com (Ali Ebrahimi)
Date: Fri, 24 Apr 2009 22:14:55 +0430
Subject: elvis pattern refinement (was Syntax patterns)
Message-ID: <5ab441490904241044p1b51bd3ag5e653da20af68378@mail.gmail.com>

My Idea for this proposal:

result = a!.method():b;

Null-Safe Call Operator: !.
return type a.method() and type of var b is assignable to result.

equivalents with :

if( a!= null){
    result = a.method();
} else{
    result =b;
}

*Or

result = a != null? a.method(): b;


Best Regards
Ali Ebrahimi
*


From reinier at zwitserloot.com  Fri Apr 24 10:49:58 2009
From: reinier at zwitserloot.com (Reinier Zwitserloot)
Date: Fri, 24 Apr 2009 19:49:58 +0200
Subject: elvis pattern refinement (was Syntax patterns)
In-Reply-To: <5ab441490904241044p1b51bd3ag5e653da20af68378@mail.gmail.com>
References: <5ab441490904241044p1b51bd3ag5e653da20af68378@mail.gmail.com>
Message-ID: <32B3A77A-F2D9-4647-8E34-8D3E2C9D5641@zwitserloot.com>

Ali, the proposal phase is long gone. These discussions about the  
elvis pattern are about which of 2 already submitted proposals to take  
(just the elvis operator, or also ?. and others) - that's why Ruslan  
and Stephen are sorting out how useful they would be in code bases.  
The other statistics Ruslan is reporting are also in regards to  
completely specified proposals submitted before the deadline of March  
30th.

  --Reinier Zwitserloot
Like it? Tip it!
http://tipit.to



On Apr 24, 2009, at 19:44, Ali Ebrahimi wrote:

> My Idea for this proposal:
>
> result = a!.method():b;
>
> Null-Safe Call Operator: !.
> return type a.method() and type of var b is assignable to result.
>
> equivalents with :
>
> if( a!= null){
>    result = a.method();
> } else{
>    result =b;
> }
>
> *Or
>
> result = a != null? a.method(): b;
>
>
> Best Regards
> Ali Ebrahimi
> *
>



From rssh at gradsoft.com.ua  Fri Apr 24 10:54:35 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Fri, 24 Apr 2009 20:54:35 +0300 (EEST)
Subject: elvis pattern refinement (was Syntax patterns)
In-Reply-To: <4b4f45e00904241028t140786bfr53ccf0c3e2ed99ff@mail.gmail.com>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240739g5b313489x162a005c16cc4ff7@mail.gmail.com>
	<90e12e623b34e8bdd2b9dc8c54ed6e3b.squirrel@wmail.gradsoft.ua>
	<cac212df65add79bf0ec412bb05348d5.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240945o4630227rc75996cad3d7fba4@mail.gmail.com>
	<152e5a7a9f1cc3e929fe730e7913e36b.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904241028t140786bfr53ccf0c3e2ed99ff@mail.gmail.com>
Message-ID: <0bbda97b46febc7962911b1c82616624.squirrel@wmail.gradsoft.ua>


> a!=null ? a.method() : b

>   a?.method() ?: b
>
> however, that would be semantically different in meaning (as now b is
> returned if method() returns null, which wasn't originally the case)
>
> Thus, this construct is invalid for Elvis, Null-safe and the
> combination of the two.
>

Ok, so will exclude one.

next question:
 a!=null ? a.method() : null
must be counted or not ?

(i.e. it's clean safe method call)




> Stephen
>
>




From rssh at gradsoft.com.ua  Fri Apr 24 11:06:31 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Fri, 24 Apr 2009 21:06:31 +0300 (EEST)
Subject: [if-s done]Re: elvis pattern refinement (was Syntax patterns)
In-Reply-To: <152e5a7a9f1cc3e929fe730e7913e36b.squirrel@wmail.gradsoft.ua>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240739g5b313489x162a005c16cc4ff7@mail.gmail.com>
	<90e12e623b34e8bdd2b9dc8c54ed6e3b.squirrel@wmail.gradsoft.ua>
	<cac212df65add79bf0ec412bb05348d5.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240945o4630227rc75996cad3d7fba4@mail.gmail.com>
	<152e5a7a9f1cc3e929fe730e7913e36b.squirrel@wmail.gradsoft.ua>
Message-ID: <ebf34c0b4599c608219f72707a0979ff.squirrel@wmail.gradsoft.ua>

>
>> If I were writing Java today without the null-safe operators, then I
>> would typically use an if-statement:
>>
>> if (foo != null) {
>>   foo.process();
>> }
>>
>> Bar bar = null;
>> if (foo != null) {
>>   bar = foo.process();
>> }
>>
>> Stephen
>>

Just added, see
http://redmine.gradsoft.ua/repositories/entry/javachecker/trunk/JavaChecker/etc/checkers_elvis.def
starting from line 24

So, in next version will be correct elvis and loops.





From Joe.Darcy at Sun.COM  Fri Apr 24 11:12:22 2009
From: Joe.Darcy at Sun.COM (Joseph D. Darcy)
Date: Fri, 24 Apr 2009 11:12:22 -0700
Subject: My wishlist and Ideas for java 7 as java developer
In-Reply-To: <5ab441490904241002r3ac43f59g327ffe88bd63b7b8@mail.gmail.com>
References: <5ab441490904241002r3ac43f59g327ffe88bd63b7b8@mail.gmail.com>
Message-ID: <49F20106.6060000@sun.com>

Ali Ebrahimi wrote:
> Hi All,
> java needs cool features.
>
> My wishlist and ideas for java 7:
>   

The items on your list have generally been covered by submitted 
proposals and it is long past the time to submit any new proposals.

[snip]
> And many other ideas.
>   

Ideas alone are worth very little.

Merely saying "I want this" without any reasoning or rationale makes at 
most a negligible contribution to the discussion.

-Joe


From rssh at gradsoft.com.ua  Fri Apr 24 11:20:04 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Fri, 24 Apr 2009 21:20:04 +0300 (EEST)
Subject: Statistics for E-Commerce system
In-Reply-To: <4b4f45e00904241025k6ccd948i5b0d646a0cc2c63b@mail.gmail.com>
References: <4b4f45e00904241025k6ccd948i5b0d646a0cc2c63b@mail.gmail.com>
Message-ID: <e8ff18e293061771aff16090bb86d0a2.squirrel@wmail.gradsoft.ua>


Great !
 Also interesting that rethrows/all catchs also vary a lot.

And how many time require processing of all of this ?

// I will try to fix elvis, loop and add loop-indexes tomorrow.


> 1.3 million LOC
> Old sourcebase, lots of refactoring down the years
> Java EE, Servlets but not EJB
> Two parts - low level utilities, and main E-commerce codebase
>
> Low level utilities
> -------------------------
> all catchs             : 549
> all conditionals       : 297
> all ifs                : 1521
> all integer literals   : 4863
> big integer literals(undescores): 326
> byte literal           : 0
> catch in finally       : 14
> elvis                  : 86  --> correct value 36
> instanceof switch      : 27
> loop with remove       : 5  --> correct value 33
> multi catch            : 31
> object switch          : 81
> rethrow clause         : 271
> string in switch       : 23
> Files:564
>
>  while \(.+?\.hasNext\(\)\)
> all hasNext() while    : 39
>  for \(Iterator
> all iterator() for     : 68
>  for \(int
> all int for            : 375
>  for \(
> all for                : 631
>
> Elvis-conditional = 36/297 = 12.1%
> Loop-remove       = 33/631 =  5.2%
> Multi-catch         = 31/549 = 5.6%
>
>
> Main E-Commerce system
> ---------------------------------------
> (counted in three parts to avoid out of memory in the tool, and to
> demonstrate how different types of code affect the results)
> Main code (most of the business logic:
> all catchs             : 2592
> all conditionals       : 2185
> all ifs                : 7431
> all integer literals   : 45473
> big integer literals(undescores): 5738
> byte literal           : 0
> catch in finally       : 35
> elvis                  : 600  --> correct value ?
> instanceof switch      : 159
> loop with remove       : 88  --> correct value 430
> multi catch            : 39
> object switch          : 379
> rethrow clause         : 859
> string in switch       : 117
> Files:5822
>
> Sub part 1 (code generated beans):
> all catchs             : 753
> all conditionals       : 10244
> all ifs                : 4955
> all integer literals   : 145405
> big integer literals(undescores) : 25957
> byte literal           : 0
> catch in finally       : 0
> elvis                  : 4058  --> correct value, probably 0
> instanceof switch      : 9
> loop with remove       : 0  --> correct value 0
> multi catch            : 0
> object switch          : 15
> rethrow clause         : 1
> string in switch       : 0
> Files:1553
>
> Sub part 2 (presentation layer):
> all catchs             : 370
> all conditionals       : 366
> all ifs                : 1622
> all integer literals   : 2632
> big integer literals(undescores) : 39
> byte literal           : 0
> catch in finally       : 6
> elvis                  : 33
> instanceof switch      : 47
> loop with remove       : 8  --> correct value 20
> multi catch            : 0
> object switch          : 112
> rethrow clause         : 61
> string in switch       : 35
> Files:1160
>
>  while \(.+?\.hasNext\(\)\)
> all hasNext() while    : 256
>  for \(Iterator
> all iterator() for     : 536
>  for \(int
> all int for            : 4530 *not all loops around lists
>  for \(
> all for                : 8248 *not all loops around lists
>
> Elvis-conditional = ?/2185 =
> Loop-with-remove  = 450/8248 = 5.5%
> Multi-catch  = 39/3715 = 1.0%
>
>
> The Elvis number currently needs manual work to calculate, so I passed
> for the size of the main sourcebase. However, 12% of all conditionals
> in the low level library is a reasonable number of hits.
>
> The loop-with-remove is between 5 and 5.5% (of all loops, which
> includes loops around things other than lists, like strings). I can't
> easily determine how often the loop index is needed, or whether it is
> the first/last loop, each of which would push up the %age.
>
> Multi-catch has about 1% of all catch statements in the main
> E-Commerce, but 5.6% in the low level libraries. This perhaps
> indicates where the sweet spot for the feature is - libraries and
> frameworks.
>
> Stephen
>
>




From pdoubleya at gmail.com  Fri Apr 24 14:11:02 2009
From: pdoubleya at gmail.com (Patrick Wright)
Date: Fri, 24 Apr 2009 23:11:02 +0200
Subject: Statistics for E-Commerce system
In-Reply-To: <4b4f45e00904241025k6ccd948i5b0d646a0cc2c63b@mail.gmail.com>
References: <4b4f45e00904241025k6ccd948i5b0d646a0cc2c63b@mail.gmail.com>
Message-ID: <64efa1ba0904241411u26e5a7beu4fb533b49bd22514@mail.gmail.com>

Since you didn't name the project, I assume this is closed-source?
It's certainly useful to run this tool across all sorts of codebases,
on the other hand, it's probably more useful for the group to run this
against open source projects where any of us can open up the codebase
and take a peek inside.


Regards
Patrick

On Fri, Apr 24, 2009 at 7:25 PM, Stephen Colebourne
<scolebourne at joda.org> wrote:
> 1.3 million LOC
> Old sourcebase, lots of refactoring down the years
> Java EE, Servlets but not EJB
> Two parts - low level utilities, and main E-commerce codebase


From ali.ebrahimi1781 at gmail.com  Fri Apr 24 15:52:00 2009
From: ali.ebrahimi1781 at gmail.com (Ali Ebrahimi)
Date: Sat, 25 Apr 2009 03:22:00 +0430
Subject: My wishlist and Ideas for java 7 as java developer
In-Reply-To: <5ab441490904241545g6e74682rb6ffd9c44f9d274@mail.gmail.com>
References: <5ab441490904241002r3ac43f59g327ffe88bd63b7b8@mail.gmail.com>
	<49F20106.6060000@sun.com>
	<5ab441490904241545g6e74682rb6ffd9c44f9d274@mail.gmail.com>
Message-ID: <5ab441490904241552w288935c9y62e2678576eabbe5@mail.gmail.com>

Hi Joe,
I'm not proposing new proposal for coin.

I just want to share My Ideas regards to submitted proposals. And I very
like to supported this Ideas by submitted proposals(in final revision), if
them are nice and acceptable.

I have followed all discussions on list from first(27 February) and the
submitted proposals for me As one java developer is not *sufficient* and
acceptable and satisfying(from viewpoint of quality Not quantity and Title).
So I decided to register to list (today) and share My Ideas for java 7 not
coin.

I (not only I *perhaps All developers*) need for this features And every day
deal with them In My code.

I just want to java to be every day better than yesterday.

Also I want to see feedback of All members on list for My Ideas in details
not generally.


Best regards
Ali ebrahimi


On Fri, Apr 24, 2009 at 10:42 PM, Joseph D. Darcy <Joe.Darcy at sun.com> wrote:

> Ali Ebrahimi wrote:
>
>> Hi All,
>> java needs cool features.
>>
>> My wishlist and ideas for java 7:
>>
>>
>
> The items on your list have generally been covered by submitted proposals
> and it is long past the time to submit any new proposals.
>
> [snip]
>
>> And many other ideas.
>>
>>
>
> Ideas alone are worth very little.
>
> Merely saying "I want this" without any reasoning or rationale makes at
> most a negligible contribution to the discussion.
>
> -Joe
>


From scolebourne at joda.org  Fri Apr 24 16:25:33 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Sat, 25 Apr 2009 00:25:33 +0100
Subject: elvis pattern refinement (was Syntax patterns)
In-Reply-To: <0bbda97b46febc7962911b1c82616624.squirrel@wmail.gradsoft.ua>
References: <3708a46a63059d8b1a46a3b7fc56036e.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240739g5b313489x162a005c16cc4ff7@mail.gmail.com>
	<90e12e623b34e8bdd2b9dc8c54ed6e3b.squirrel@wmail.gradsoft.ua>
	<cac212df65add79bf0ec412bb05348d5.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904240945o4630227rc75996cad3d7fba4@mail.gmail.com>
	<152e5a7a9f1cc3e929fe730e7913e36b.squirrel@wmail.gradsoft.ua>
	<4b4f45e00904241028t140786bfr53ccf0c3e2ed99ff@mail.gmail.com>
	<0bbda97b46febc7962911b1c82616624.squirrel@wmail.gradsoft.ua>
Message-ID: <4b4f45e00904241625n71e6cab5kbd0ada460a74c542@mail.gmail.com>

2009/4/24 Ruslan Shevchenko <rssh at gradsoft.com.ua>:
> next question:
> ?a!=null ? a.method() : null
> must be counted or not ?

Yes, that would be another pattern.

But so would multiple tests:

if (a != null && a.b() != null) {
  a.b().c();
}

if (a != null && a.b() != null) {
  result = a.b().c();
}


BTW, I'd prefer to see separate figures for Elvis and Null-Safe
operators. Thus that means two 'define's in the def file.

Stephen


From scolebourne at joda.org  Fri Apr 24 16:36:10 2009
From: scolebourne at joda.org (Stephen Colebourne)
Date: Sat, 25 Apr 2009 00:36:10 +0100
Subject: Statistics for E-Commerce system
In-Reply-To: <64efa1ba0904241411u26e5a7beu4fb533b49bd22514@mail.gmail.com>
References: <4b4f45e00904241025k6ccd948i5b0d646a0cc2c63b@mail.gmail.com>
	<64efa1ba0904241411u26e5a7beu4fb533b49bd22514@mail.gmail.com>
Message-ID: <4b4f45e00904241636w6fdb1833gdf905fd556da22c3@mail.gmail.com>

2009/4/24 Patrick Wright <pdoubleya at gmail.com>:
> Since you didn't name the project, I assume this is closed-source?
Yes, its closed. One point I didn't mention, is that it is Java 5 based source.

> It's certainly useful to run this tool across all sorts of codebases,
> on the other hand, it's probably more useful for the group to run this
> against open source projects where any of us can open up the codebase
> and take a peek inside.
While being able to look at the source and see why particular pieces
of code are triggering particular language change proposals, its worth
pointing out that OSS is very different code.

OSS is typically library/framework code, closed source is typically
business logic. As shown in my figures, that can greatly affect the
kind of results you get. I'd also note that there is vastly more
closed source than open source. So, its the closed source code that
needs to be tackled by language changes.

(I'm not arguing that we shouldn't run it against OSS either! But I do
believe that closed source is in the end the primary interesting case)

BTW, I understand that James Gosling did similar analysis when
evaluating accessing lists/maps by array-like syntax.

The key is to obtain data points, which help Joe/Sun make decisions.

> And how many time require processing of all of this ?
The tool took less than an hour total, but split over the four runs.
The other figures required some Eclipse searches, so the whole effort
took a little longer.

Stephen


From paul.martin at gmail.com  Sat Apr 25 04:12:38 2009
From: paul.martin at gmail.com (Paul Martin)
Date: Sat, 25 Apr 2009 12:12:38 +0100
Subject: PROPOSAL: Named method parameters
In-Reply-To: <001636458a864f71e304681a2fb7@google.com>
References: <001636458a864f71e304681a2fb7@google.com>
Message-ID: <4ce75f920904250412k48fe11f9p3cc3b0f8c52bcc03@mail.gmail.com>

Hi,

Thanks for your suggestions.

PEC does seem interesting, and seems to be covering a different space
to that covered by analysis tools such as Findbugs (that I am familiar
with).  I'll take a closer look.  Will you extend it to include
support for the @Immutable (and similar) annotations that are
hopefully coming with Java7?

Simple structures are a reasonable alternative to named parameters,
particularly based on your assumption that "you would only use this if
there were a lot of arguments", which would not be the common case.
Other than the (slightly) more complex syntax, the only real
disadvantage that I can see is:
- It is hard to ensure that all of the fields are explicitly set (to
avoid errors where we forget to set a value, or refactor to add a
field and then forget to update a caller)

However, this does seem to be solvable using static analysis tools
such as Findbugs (or PEC?), particularly if there is an annotation
such as @SubclassMustSet on the class or each required field, which
could indicate that such checks are required.  Tools such as Spring
should be able to use simple structures directly (and maybe additional
support could simplify their use).  Maybe I'll give that a go.

I still think that adding support for named parameters to Java would
be worthwhile (both because the intention is perhaps clearer, and they
may be even more valuable in other JVM languages), and don't think
that it necessarily has to be too contentious to implement them.

Regards,

Paul


On Wed, Apr 22, 2009 at 1:52 AM,  <howard.lovatt at gmail.com> wrote:
> I use the builder pattern successfully via my enhanced compiler ( pet
> project :) ):
>
> https://pec.dev.java.net/nonav/compile/index.html
>
> and in particular:
>
> https://pec.dev.java.net/nonav/compile/javadoc/pec/compile/immutable/ImmutableValueConversions.html
>
> The enhanced compiler enforces the pattern, ie if you get it wrong the
> compiler gives you an error message.
>
> You can also use a simple structure like class, eg:
>
> class Point {
>
> static class Args {
> int x = 0;
> int y = 0;
> }
>
> final int x;
>
> final iny y;
>
> Point( Args args ) {
> x = args.x;
> y = args.y;
> }
>
> ...
>
> }
>
> Which is used like:
>
> Point p = new Point( new Point.Args() {{ x = 1; }} );
>
> As the original post said you would only use this if there were a lot of
> arguments, therefore the overhead of typing "new Point.Args() {{ }}" is
> negligible.
>
> -- Howard.
>
>


From rssh at gradsoft.com.ua  Sat Apr 25 07:36:47 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Sat, 25 Apr 2009 17:36:47 +0300 (EEST)
Subject: Elvis and NullSafe:  description of patterns
Message-ID: <cfb29ebcc4598f34eac499c9e28095a4.squirrel@wmail.gradsoft.ua>


It;s about patterns for applicability of elvis Proposal in
http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000047.html


First naive approach was to count all condition expressions, which looks
like  (a != null ? a.method(..) : b).
  This approach is criticized, because semantics of substitution with
elvis operators _<code>a?method() ?: b</code>_ is differ from original:
when _a.method()_ will return _null_, than result of expression will be
_b_, not _null_.
<IMHO>
  From other side, when people will write software with elvis operator, I
believe they will slightly change semantics of their functions to use
elvis, so this approach still can be used as estimation.
</IMHO>

 After helper discussion with Stephen in this list, I want to describe
patterns which will used for counting of number of applicability for
elvis proposal in next 'release or run' of javachecker coin rules, to
ensure, that they are more or less correct.

rules can be reviewed now: (see
http://redmine.gradsoft.ua/repositories/entry/javachecker/trunk/JavaChecker/etc/checkers_elvis.def)

So, patterns are:

Elvis itself, i. e.
  a==null ? a : b
  a!=null ? b : a
  null==a ? b : a
  null!=a ? a : b

NullSafe method call (as condition statement)

if (a==null) {
  a.process();
}

and

if (a==null) {
  x=a.process();
}


NullSafe method call (as condition expression)
  a!=null ? a.method(...) : null
  a==null ? null: a.method(...)
  null==a ? null: a.method(...)
  null!=a ? a.method(...) : null

 NullSafe field access. (as method calls, but with field access expression
instead method call)

  NullSafe array index access (as method calls, but with array index
expression instead method call)

 Complex null-safe expression. example is

 public static Integer qqq(Z[] z, int i)
 {
   if ( z!=null && z[i]!=null && z[i].y!=null) {
     return z[i].y.a;
   } else {
     return null;
   }
 }


We use some approximation, i. e. count all if patterns, where
* if condition expression is ConditionAnd of conditions all of which are
check for nulls.
* argument of first elementary condition from condition expression is
contained in block, which evaluated when if condition experssion is
evaluated to true.

Hope, this is more close to reality, than first naive proposal.

Below of run for jetty, main results and javachecker custom version  will
be available later (hope tomorrow) after adding loop index. handling
issues.


*       :       0
all bit ands    :       121
all conditional expressions     :       277
all catchs      :       281
all ifs :       764
all integer literals    :       2903
big integer literals(undescores)        :       25
byte literal    :       52
catch in finally        :       3
elvis   :       43
elvis1  :       33
instanceof switch       :       8
loop with remove        :       0
multi catch     :       22
nullsafe call of fields and methods     :       44
object switch   :       31
rethrow clause  :       34
string in switch        :       19
widening operator (semantics)   :       10
widening operator (syntax)      :       20
Files:187






From howard.lovatt at iee.org  Sat Apr 25 18:59:24 2009
From: howard.lovatt at iee.org (Howard Lovatt)
Date: Sun, 26 Apr 2009 11:59:24 +1000
Subject: PROPOSAL: Named method parameters
In-Reply-To: <4ce75f920904250412k48fe11f9p3cc3b0f8c52bcc03@mail.gmail.com>
References: <001636458a864f71e304681a2fb7@google.com>
	<4ce75f920904250412k48fe11f9p3cc3b0f8c52bcc03@mail.gmail.com>
Message-ID: <3dd3f56a0904251859y595c59e4pd664f1005ab5350b@mail.gmail.com>

Hi Paul,
I am working on including annotations, but there are a few problem with
annotations in this context at the moment. Namely if I annotate an
interface, then a class that implements that interface does not get the
annotation even if the annotation is annotated as
Inherited<http://java.sun.com/javase/6/docs/api/java/lang/annotation/Inherited.html>.
I think there was discussion of this problem as part of JSR 308, but I am
unsure how far a solution progressed. A second problem, less serious if the
first was fixed, is that you can't add a method to an annotation, so for
example with Immutable Value
Conversions<http://pec.dev.java.net/nonav/compile/javadoc/pec/compile/immutable/ImmutableValueConversions.html>
I
want standardly named conversion methods but with annotations you can't do
this. Thirdly it is generally frowned upon to use Annotations to
change behavior, with the advice to use a marker interface (e.g.
Serialization).

As a result I currently plan to use a mixture of annotations and interfaces.

 -- Howard.

2009/4/25 Paul Martin <paul.martin at gmail.com>

> Hi,
>
> Thanks for your suggestions.
>
> PEC does seem interesting, and seems to be covering a different space
> to that covered by analysis tools such as Findbugs (that I am familiar
> with).  I'll take a closer look.  Will you extend it to include
> support for the @Immutable (and similar) annotations that are
> hopefully coming with Java7?
>
> Simple structures are a reasonable alternative to named parameters,
> particularly based on your assumption that "you would only use this if
> there were a lot of arguments", which would not be the common case.
> Other than the (slightly) more complex syntax, the only real
> disadvantage that I can see is:
> - It is hard to ensure that all of the fields are explicitly set (to
> avoid errors where we forget to set a value, or refactor to add a
> field and then forget to update a caller)
>
> However, this does seem to be solvable using static analysis tools
> such as Findbugs (or PEC?), particularly if there is an annotation
> such as @SubclassMustSet on the class or each required field, which
> could indicate that such checks are required.  Tools such as Spring
> should be able to use simple structures directly (and maybe additional
> support could simplify their use).  Maybe I'll give that a go.
>
> I still think that adding support for named parameters to Java would
> be worthwhile (both because the intention is perhaps clearer, and they
> may be even more valuable in other JVM languages), and don't think
> that it necessarily has to be too contentious to implement them.
>
> Regards,
>
> Paul
>
>
> On Wed, Apr 22, 2009 at 1:52 AM,  <howard.lovatt at gmail.com> wrote:
> > I use the builder pattern successfully via my enhanced compiler ( pet
> > project :) ):
> >
> > https://pec.dev.java.net/nonav/compile/index.html
> >
> > and in particular:
> >
> >
> https://pec.dev.java.net/nonav/compile/javadoc/pec/compile/immutable/ImmutableValueConversions.html
> >
> > The enhanced compiler enforces the pattern, ie if you get it wrong the
> > compiler gives you an error message.
> >
> > You can also use a simple structure like class, eg:
> >
> > class Point {
> >
> > static class Args {
> > int x = 0;
> > int y = 0;
> > }
> >
> > final int x;
> >
> > final iny y;
> >
> > Point( Args args ) {
> > x = args.x;
> > y = args.y;
> > }
> >
> > ...
> >
> > }
> >
> > Which is used like:
> >
> > Point p = new Point( new Point.Args() {{ x = 1; }} );
> >
> > As the original post said you would only use this if there were a lot of
> > arguments, therefore the overhead of typing "new Point.Args() {{ }}" is
> > negligible.
> >
> > -- Howard.
> >
> >
>



-- 
 -- Howard.


From paul.martin at gmail.com  Sun Apr 26 02:11:02 2009
From: paul.martin at gmail.com (paul.martin at gmail.com)
Date: Sun, 26 Apr 2009 09:11:02 +0000
Subject: PROPOSAL: Named method parameters
In-Reply-To: <3dd3f56a0904251859y595c59e4pd664f1005ab5350b@mail.gmail.com>
Message-ID: <0016e6d7eaacd9af3c0468719bd0@google.com>

Hi,

That all sounds sensible. It would be good to integrate with JSR 308, but  
your idea of using standard methods to highlight the design pattern sounds  
nice and would need an interface.

Regards,

Paul

On Apr 26, 2009 2:59am, Howard Lovatt <howard.lovatt at iee.org> wrote:
> Hi Paul,

> I am working on including annotations, but there are a few problem with  
> annotations in this context at the moment. Namely if I annotate an  
> interface, then a class that implements that interface does not get the  
> annotation even if the annotation is annotated as Inherited. I think  
> there was discussion of this problem as part of JSR 308, but I am unsure  
> how far a solution progressed. A second problem, less serious if the  
> first was fixed, is that you can't add a method to an annotation, so for  
> example with Immutable Value Conversions I want standardly named  
> conversion methods but with annotations you can't do this. Thirdly it is  
> generally frowned upon to use Annotations to change behavior, with the  
> advice to use a marker interface (eg Serialization).



> As a result I currently plan to use a mixture of annotations and  
> interfaces.


> -- Howard.

> 2009/4/25 Paul Martin paul.martin at gmail.com>

> Hi,



> Thanks for your suggestions.



> PEC does seem interesting, and seems to be covering a different space

> to that covered by analysis tools such as Findbugs (that I am familiar

> with). I'll take a closer look. Will you extend it to include

> support for the @Immutable (and similar) annotations that are

> hopefully coming with Java7?



> Simple structures are a reasonable alternative to named parameters,

> particularly based on your assumption that "you would only use this if

> there were a lot of arguments", which would not be the common case.

> Other than the (slightly) more complex syntax, the only real

> disadvantage that I can see is:

> - It is hard to ensure that all of the fields are explicitly set (to

> avoid errors where we forget to set a value, or refactor to add a

> field and then forget to update a caller)



> However, this does seem to be solvable using static analysis tools

> such as Findbugs (or PEC?), particularly if there is an annotation

> such as @SubclassMustSet on the class or each required field, which

> could indicate that such checks are required. Tools such as Spring

> should be able to use simple structures directly (and maybe additional

> support could simplify their use). Maybe I'll give that a go.



> I still think that adding support for named parameters to Java would

> be worthwhile (both because the intention is perhaps clearer, and they

> may be even more valuable in other JVM languages), and don't think

> that it necessarily has to be too contentious to implement them.



> Regards,



> Paul





> On Wed, Apr 22, 2009 at 1:52 AM, howard.lovatt at gmail.com> wrote:

> > I use the builder pattern successfully via my enhanced compiler ( pet

> > project :) ):

> >

> > https://pec.dev.java.net/nonav/compile/index.html

> >

> > and in particular:

> >

> >  
> https://pec.dev.java.net/nonav/compile/javadoc/pec/compile/immutable/ImmutableValueConversions.html


> >


> > The enhanced compiler enforces the pattern, ie if you get it wrong the

> > compiler gives you an error message.

> >


> > You can also use a simple structure like class, eg:


> >

> > class Point {

> >

> > static class Args {

> > int x = 0;

> > int y = 0;

> > }

> >

> > final int x;

> >

> > final iny y;

> >

> > Point( Args args ) {

> > x = args.x;

> > y = args.y;

> > }

> >

> > ...

> >

> > }

> >

> > Which is used like:

> >

> > Point p = new Point( new Point.Args() {{ x = 1; }} );

> >

> > As the original post said you would only use this if there were a lot of

> > arguments, therefore the overhead of typing "new Point.Args() {{ }}" is

> > negligible.

> >

> > -- Howard.

> >

> >






> --
> -- Howard.





From rssh at gradsoft.com.ua  Sun Apr 26 08:03:58 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Sun, 26 Apr 2009 18:03:58 +0300 (EEST)
Subject: traditional for loop, which use indexes: pattern description
Message-ID: <72841246c7ee7bf566925c08146a41c8.squirrel@wmail.gradsoft.ua>


 Good day, community.

It's about proposal about adding for of loop with access for index value.
http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000737.html

Patterns can be reviewed at
http://redmine.gradsoft.ua/repositories/entry/javachecker/trunk/JavaChecker/etc/checkers_coin.def

So, what statistics we need:
 1) How many for traditional loops we have at all.
 2) How many for loops have form:

 for(int i=0; i<x.length; ++i)
 or
 for(int i=0; i<x.size(); ++i)
 or
 i++ instead ++i
 or
 i=0 instead int i=0
in all combinations.
 All of those loops we
So, how many such loops we have ? -- near 1/3 of all traditional loops.

 3) for, where condition is like it.next()
 4) for and while, where condition like it.next and which call remove.

Sum of 2 and 4 will give us number of optimizations for index loop proposal

I guess this is cover, but correct me If I wrong.

Regards !







From rssh at gradsoft.com.ua  Sun Apr 26 08:21:10 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Sun, 26 Apr 2009 18:21:10 +0300 (EEST)
Subject: Syntax patterns:  more more statistics.
Message-ID: <28a181896c1bc05e2777cb6bcb166fec.squirrel@wmail.gradsoft.ua>


 Good day, community.

 Next 'release' for syntax pattern and check tool.

Main changes:
  - added set of patterns, which more correctly describe elvis proposal
   Approriative names: elvis1 and NullSafe
   (see
http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001610.html
for details)
  - added checking for it.remove() inside for loop.
  - added set of patterns for widening integer proposal
    (see
http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001582.html
for details)
  - added set of patterns for counting loops with index access
   (see
http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001613.html
for details)
   - added count for all condition expressions.

Modofied JavaChecker installation which include new patterns can be
downloaded from
http://datacenter.gradsoft.ua/public.repository/ua.gradsoft/javachecker/installations/JavaCheckerSourceInstaller-2.5.0p3.jar

If anybody whant run checks on own dataset or/and add own check
definitions: all  procedure is the same as in my previous letter (see
http://mail.openjdk.java.net/pipermail/coin-dev/2009-April/001442.html)
except URL for last version

Note, that with all checks users quite run slow, so may be have sense to
run only checks you needed, not all.

Some results:

coin-jetty:
all bit ands    :       121
all conditional expressions     :       277
all catchs      :       281
all ifs :       764
all integer literals    :       2903
all traditional fors    :       315
big integer literals(undescores)        :       25
byte literal    :       52
catch in finally        :       3
elvis   :       43
elvis1  :       33
for loop from 0 to size or length       :       100
for with limit like it.next()   :       4
instanceof switch       :       8
invalid checker comments        :       0
loop with remove        :       0
multi catch     :       22
nullsafe call of fields and methods     :       35
object switch   :       31
rethrow clause  :       34
string in switch        :       19
widening operator (semantics)   :       10
widening operator (syntax)      :       20


hibernate:
all bit ands    :       2
all conditional expressions     :       792
all catchs      :       650
all ifs :       2410
all integer literals    :       3240
all traditional fors    :       708
big integer literals(undescores)        :       12
byte literal    :       1
catch in finally        :       27
elvis   :       182
elvis1  :       77
for loop from 0 to size or length       :       385
for with limit like it.next()   :       16
instanceof switch       :       28
loop with remove        :       12
multi catch     :       25
nullsafe call of fields and methods     :       175
object switch   :       94
rethrow clause  :       450
string in switch        :       86
widening operator (semantics)   :       0
widening operator (syntax)      :       0
Files:1372

openjdk:
all bit ands    :       6822
all conditional expressions     :       6770
all catchs      :       8411
all ifs :       28464
all integer literals    :       121919
all traditional fors    :       11530
big integer literals(undescores)        :       4589
byte literal    :       1452
catch in finally        :       103
elvis   :       880
elvis1  :       437
for loop from 0 to size or length       :       3137
for with limit like it.next()   :       235
instanceof switch       :       317
loop with remove        :       94
multi catch     :       412
nullsafe call of fields and methods     :       384
object switch   :       1360
rethrow clause  :       3267
string in switch        :       444
widening operator (semantics)   :       1090
widening operator (syntax)      :       1955
Files:9278

all bit ands    :       58
all conditional expressions     :       208
all catchs      :       171
all ifs :       735
all integer literals    :       2282
all traditional fors    :       271
big integer literals(undescores)        :       24
byte literal    :       2
catch in finally        :       2
elvis   :       30
elvis1  :       18
for loop from 0 to size or length       :       71
for with limit like it.next()   :       20
instanceof switch       :       6
loop with remove        :       7
multi catch     :       9
nullsafe call of fields and methods     :       66
object switch   :       27
rethrow clause  :       84
string in switch        :       10
widening operator (semantics)   :       0
widening operator (syntax)      :       2
Files:920

(btw, I plan to add result for compiere ERP, when understand their
building process)




From brucechapman at paradise.net.nz  Sun Apr 26 16:07:47 2009
From: brucechapman at paradise.net.nz (brucechapman at paradise.net.nz)
Date: Mon, 27 Apr 2009 11:07:47 +1200 (NZST)
Subject: Syntax patterns:  more more statistics.
In-Reply-To: <28a181896c1bc05e2777cb6bcb166fec.squirrel@wmail.gradsoft.ua>
References: <28a181896c1bc05e2777cb6bcb166fec.squirrel@wmail.gradsoft.ua>
Message-ID: <1240787267.49f4e9432c4f9@www.paradise.net.nz>

Quoting Ruslan Shevchenko <rssh at gradsoft.com.ua>:

> Note, that with all checks users quite run slow, so may be have sense
> to
> run only checks you needed, not all.
> 
> Some results:
> 
> widening operator (semantics) : 10
> widening operator (syntax) : 20
> 
>

Ruslan,

The "widening operator (syntax)" check is not really helpful for the widening
conversion stuff. The "semantic" one seems to be correct. I suspect the "syntax"
one is also picking up a corresponding "encoding" operation corresponding to the
"decoding" operation which is normally being detected by the "semantics" check
(which is why the syntax value is very close to double the number for the
semantic check). To save processing time, please drop the "syntax" check.

Oh,

And thanks very much for all your effort on this.

Bruce



From rssh at gradsoft.com.ua  Mon Apr 27 09:23:51 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Mon, 27 Apr 2009 19:23:51 +0300 (EEST)
Subject: Syntax patterns:  more more statistics.
In-Reply-To: <1240787267.49f4e9432c4f9@www.paradise.net.nz>
References: <28a181896c1bc05e2777cb6bcb166fec.squirrel@wmail.gradsoft.ua>
	<1240787267.49f4e9432c4f9@www.paradise.net.nz>
Message-ID: <7ed018835d415448739477c8349958ae.squirrel@wmail.gradsoft.ua>

>
> The "widening operator (syntax)" check is not really helpful for the
> widening
> conversion stuff. The "semantic" one seems to be correct. I suspect the
> "syntax"
> one is also picking up a corresponding "encoding" operation corresponding
> to the
> "decoding" operation which is normally being detected by the "semantics"
> check
> (which is why the syntax value is very close to double the number for the
> semantic check). To save processing time, please drop the "syntax" check.
>

Ok. thanks, will be dropped. (for now to disable possible comment out
lines 214-221 in checkers_coin.def)

Also I forgot to drop old incorrect elvis check. (lines 124-143)

> Oh,
>
> And thanks very much for all your effort on this.
>

 Thanks for good words.  Problems are quite funny to justify scheduled time.

// Interesting that near 50% of my a priory assumptions about
frequency of constructions in Java code was wrong ;)




From John.Rose at Sun.COM  Wed Apr 29 19:37:01 2009
From: John.Rose at Sun.COM (John Rose)
Date: Wed, 29 Apr 2009 19:37:01 -0700
Subject: PROPOSAL: language support for JSR 292
In-Reply-To: <8D7F16CE-69EB-4742-97E4-2B1E88A222BF@Sun.COM>
References: <80FFB064-577D-4CEA-A93A-73C424AAE21B@sun.com>
	<15e8b9d20903290055p399a724al786f34b8188a62d2@mail.gmail.com>
	<49D013A3.60505@univ-mlv.fr>
	<8D7F16CE-69EB-4742-97E4-2B1E88A222BF@Sun.COM>
Message-ID: <24E47781-3822-49BE-B147-AA231B1FBA82@sun.com>

I have factored out the Dynamic type from the proposal, leaving a  
static-only type called InvokeDynamic in its place.  Here is the  
updated spec (also enclosed FTR):
   http://wikis.sun.com/display/mlvm/ProjectCoinProposal

The type java.dyn.InvokeDynamic is a uninstatiable class (like  
Collections or Arrays) with no apparent methods. However, the compiler  
treats it has if it had an infinite supply of static methods of all  
names and signatures, for which it generates invokedynamic  
instructions instead of invokestatic instructions.

By removing the value type Dynamic from the base proposal, we serve  
the immediate need for system programming on top of JSR 292, while  
deferring the question (a truly absorbing and important question) of  
integrating dynamic values with Java's type system.

-- John

P.S.  The factored-out parts, about interface Dynamic and its  
interesting rules for conversion and method invocation, are placed here:
   http://wikis.sun.com/display/mlvm/InterfaceDynamic

And, should you have an appetite for even more of the same, some rough  
notes a fuller integration of Java with dynamic types is here:
   http://wikis.sun.com/display/mlvm/DynamicJava

P.P.S. Here is a text-only copy of the basic proposal:

-------------- next part --------------


From John.Rose at Sun.COM  Wed Apr 29 19:41:41 2009
From: John.Rose at Sun.COM (John Rose)
Date: Wed, 29 Apr 2009 19:41:41 -0700
Subject: PROPOSAL: language support for JSR 292
In-Reply-To: <49D5C7E3.50801@sun.com>
References: <80FFB064-577D-4CEA-A93A-73C424AAE21B@sun.com>
	<6F835C91-A2F2-4050-BD03-DB1B462C2B4F@sun.com> <49D5C7E3.50801@sun.com>
Message-ID: <2B41E202-273B-4876-BEB4-2C1BADA1A22E@Sun.COM>

On Apr 3, 2009, at 1:25 AM, Joseph D. Darcy wrote:

> Reiterating a point Neal raised, if Dynamic is not related to Object,
> what does that mean when Dynamic is used as the format type argument  
> to
> a type parameter?  What do "? extends Dynamic" and "? super Dynamic"
> mean to the type system?

It means something limited like ? extends String or ? super Object.   
I.e., there aren't any interesting types other than Dynamic itself  
that match the wildcard.

> Actually there is a special rule that catching Exception is always  
> okay
> per JLS 11.2.3; this program is legal and compiles fine:
>
> public class Test {
>    public static void main(String... args){
>    try {
>        ;
>    } catch (Exception e) {
>        ;
>    }
>    }
> }
>

Thanks.  Amending the example to IOError.

>
> So what are the notions of identity and equality for method handles?

Inherited from Object. Nothing special.

> [snip]
>> 4.1 As specified above, the interface java.dyn.Dynamic has no
>> supertypes or members.  As such, it is a bare reference type.  (As an
>> arbitrary relation, the superclass of Dynamic[] is Object[].)  We
>>
>
> Are there any other type building operations besides arrays we need to
> worry about?

I don't think so.

List<Dynamic> is impossible for interesting reasons.  The (erased)  
implementation of List internally makes use of Object.toString,  
Object.equals, and perhaps other such methods.  These calls are wrong  
for Dynamic values, since Dynamic (not being a subtype) does not  
inherit Object.equals and the rest.  This allows a Dynamic object to  
cleanly model another language, without holes in its method namespace.

(Consider a process-oriented capability for which the name "wait" is  
significant, or some knowledge representation language that has  
different notions about "equals".  The MOP doesn't need to special- 
case those names.  It's a small point but worth defending, I think.)

(In C#, with reified types, they can customize their List<Dynamic> to  
make a MOP-mediated call to equals, I suppose.)

>> But, the Java operators "==" "!=" "+" "+=" on reference types are
>> clarified to apply only to reference types which are java.lang.Object
>> or one of its subtypes; they do not have a predefined meaning if
>> either operand is dynamic.  The "synchronized" and "throw" statements
>> cannot be applied to dynamic expressions.
>>
>
> So if there is no predefined meaning, are those operations illegal?

Yes.  More specifically, they are reserved for future use, in case we  
want to do something with dynamic operator overloading.

(There's a half-baked sketch of what this could mean someday, on the  
mlvm wiki.  It's not ready to discuss yet.)

>> Facilities which compute type relations (such as
>> javax.lang.model.util.Types) may need to be updated to take Dynamic
>> into account.  Generally speaking, the new Dynamic conversions  
>> operate
>> in parallel to the implicit boxing conversions.  That is, they add no
>> new subtype or supertype relations, but they provide a few more ways
>> for values to be implicitly converted or casted.
>>
>
> Yes, I would expect a few changes to the type-related APIs.  They may
> also need to be changes to programs that assume Object is the root of
> the reference type hierarchy.  I know I've written annotation  
> processing
> code like that and Dynamic would need to be special cased in there.

Thanks.

As noted in the previous message, I have updated the proposal.

-- John


From neal at gafter.com  Wed Apr 29 20:14:44 2009
From: neal at gafter.com (Neal Gafter)
Date: Wed, 29 Apr 2009 20:14:44 -0700
Subject: PROPOSAL: language support for JSR 292
In-Reply-To: <24E47781-3822-49BE-B147-AA231B1FBA82@sun.com>
References: <80FFB064-577D-4CEA-A93A-73C424AAE21B@sun.com> 
	<15e8b9d20903290055p399a724al786f34b8188a62d2@mail.gmail.com> 
	<49D013A3.60505@univ-mlv.fr>
	<8D7F16CE-69EB-4742-97E4-2B1E88A222BF@Sun.COM> 
	<24E47781-3822-49BE-B147-AA231B1FBA82@sun.com>
Message-ID: <15e8b9d20904292014r39b881f2r993bca0d62f8c377@mail.gmail.com>

These proposals appears to allow primitives and "void" to be used as generic
type arguments for this special class.  This use of the syntax has nothing
to do with generics.  Therefore, I believe it is an abuse of syntax.

If you're going to extend the language to support this special InvokeDynamic
class, you might as well just define language support for dynamic
invocations directly without the magic class and generic extensions.  I
don't think the current spec for Dynamic fits with the current type system.
If you are adding special types like InvokeDynamic, I think they must be
reference types (i.e. a subtype of Object).  You should try to get some
information about what C# has done in this area for "dynamic", as I believe
it could be applied to Java and result in a clean solution.

By the way, now is a good time to add the boxed "Null" type, which has no
instances, referring to the type of null.  I don't think this purpose is
well served by using java.lang.Void.

On Wed, Apr 29, 2009 at 7:37 PM, John Rose <John.Rose at sun.com> wrote:

> I have factored out the Dynamic type from the proposal, leaving a
> static-only type called InvokeDynamic in its place.  Here is the updated
> spec (also enclosed FTR):
>  http://wikis.sun.com/display/mlvm/ProjectCoinProposal
>
> The type java.dyn.InvokeDynamic is a uninstatiable class (like Collections
> or Arrays) with no apparent methods. However, the compiler treats it has if
> it had an infinite supply of static methods of all names and signatures, for
> which it generates invokedynamic instructions instead of invokestatic
> instructions.
>
> By removing the value type Dynamic from the base proposal, we serve the
> immediate need for system programming on top of JSR 292, while deferring the
> question (a truly absorbing and important question) of integrating dynamic
> values with Java's type system.
>
> -- John
>
> P.S.  The factored-out parts, about interface Dynamic and its interesting
> rules for conversion and method invocation, are placed here:
>  http://wikis.sun.com/display/mlvm/InterfaceDynamic
>
> And, should you have an appetite for even more of the same, some rough
> notes a fuller integration of Java with dynamic types is here:
>  http://wikis.sun.com/display/mlvm/DynamicJava
>
> P.P.S. Here is a text-only copy of the basic proposal:
>
>
>
>
>
>
>


From rssh at gradsoft.com.ua  Wed Apr 29 23:39:01 2009
From: rssh at gradsoft.com.ua (Ruslan Shevchenko)
Date: Thu, 30 Apr 2009 09:39:01 +0300 (EEST)
Subject: PROPOSAL: language support for JSR 292
In-Reply-To: <24E47781-3822-49BE-B147-AA231B1FBA82@sun.com>
References: <80FFB064-577D-4CEA-A93A-73C424AAE21B@sun.com>
	<15e8b9d20903290055p399a724al786f34b8188a62d2@mail.gmail.com>
	<49D013A3.60505@univ-mlv.fr>
	<8D7F16CE-69EB-4742-97E4-2B1E88A222BF@Sun.COM>
	<24E47781-3822-49BE-B147-AA231B1FBA82@sun.com>
Message-ID: <0a78e808aead077cd9f7cb5c7934fdd9.squirrel@wmail.gradsoft.ua>

>    http://wikis.sun.com/display/mlvm/ProjectCoinProposal
>

2.7 If a class extends MethodHandle, it does not inherit any of the
implicitly defined invoke methods...

 Why not make MethodHandle final ?






From Maurizio.Cimadamore at Sun.COM  Thu Apr 30 02:55:03 2009
From: Maurizio.Cimadamore at Sun.COM (Maurizio Cimadamore)
Date: Thu, 30 Apr 2009 10:55:03 +0100
Subject: PROPOSAL: language support for JSR 292
In-Reply-To: <2B41E202-273B-4876-BEB4-2C1BADA1A22E@Sun.COM>
References: <80FFB064-577D-4CEA-A93A-73C424AAE21B@sun.com>
	<6F835C91-A2F2-4050-BD03-DB1B462C2B4F@sun.com> <49D5C7E3.50801@sun.com>
	<2B41E202-273B-4876-BEB4-2C1BADA1A22E@Sun.COM>
Message-ID: <49F97577.4090002@sun.com>

John Rose wrote:
> On Apr 3, 2009, at 1:25 AM, Joseph D. Darcy wrote:
>
>   
>> Reiterating a point Neal raised, if Dynamic is not related to Object,
>> what does that mean when Dynamic is used as the format type argument  
>> to
>> a type parameter?  What do "? extends Dynamic" and "? super Dynamic"
>> mean to the type system?
>>     
>
> It means something limited like ? extends String or ? super Object.   
> I.e., there aren't any interesting types other than Dynamic itself  
> that match the wildcard.
>
>   
1) I'd strongly recommend to forbid usage of InvokeDynamic type in the 
following contexts:

(i) extends clause (e.g. class MyDynamic extends InvokeDynamic)
(ii) type-parameter bound (e.g. class Foo<X extends InvokeDynamic & 
Comparable<?>>)
(iii) wildcard type-argument (e.g. Foo<? extends InvokeDynamic)

While generics/wildcards are essentially a way to refine static 
type-checking, InvokeDynamic provides a way to disable static checking 
completely. For this reason I don't see the two features going side by 
side in any meaningful way. It is true that now that InvokeDynamic has 
become an abstract holder of static methods, it probably makes less 
sense to write code like the above (apart from (i) which users might be 
tempted to write) - nevertheless the compiler should detect such invalid 
usages and flag them as errors.

My point is that a Java class shouldn't ever need to be parameterized on 
something that is bound by InvokeDynamic (or Dynamic) - as those types 
do not provide the type-system with any info.

2) I agree with Neal that the usage of Void feels a bit hacky. If you 
need null values to be typed differently then I agree that probably 
adding java.lang.Null would be the best thing to do, rather than 
overriding the semantics of Void.

3) InvokeDynamic and type-inference. It seems like you can optionally 
provide a type-parameter denoting the dynamic call's expected return 
type. This is fine, as long as it is consistent with JLS 15.12.2.7 and 
15.12.2.8. In your examples it seems like the usage of such type 
argument is completely optional. If specified, it provides additional 
info about the dynamic call site such that, e.g. the following code will 
be rejected:

int i = InvokeDynamic.<String>myDynMethod("Hello!"); // type (String) -> 
String

Can this optional type argument be inferred so that the following method 
call will behave identically?

int i = InvokeDynamic.myDynMethod("Hello!"); // type (String) -> String

[I did some testing and it seems like inference is not supported - the 
above line will give an incompatible types error, found Object, expecetd 
int]

If so, you are mimicking an under-constrained type-variable (a method 
type variable that cannot be inferred from actual arguments passed to 
the method). This raises a question: what happens when the dynamic call 
site does not appear within an assignment context, e.g.

InvokeDynamic.myDynMethod("Hello!");

or

int i = (Integer)InvokeDynamic.myDynMethod("Hello!");

In those cases, following 15.12.2.8, the under-constrained type variable 
should be inferred to be its declared bound. What does it mean in this 
case? Object ? Null ? Reading from your examples it seems like if no 
optional type-argument for the return type is provided, no info about 
the return type is included in the MethodHandle type generated by javac. 
Which means that this behavior cannot be explained in terms of generic 
method call/type inference (and thus 15.12.2.7/15.12.2.8).

An alternative would be to pass to InvokeDynamic the return type Class 
object corresponding the to expected return type as the first parameter 
of the dynamic call:

InvokeDynamic.myDynMethod(int.class, "Hello!"); // type (String) -> int

This has the advantage of not requiring a separate language extension in 
order to allow primitive type (and void) to be specified as parameter types.

Maurizio
>> Actually there is a special rule that catching Exception is always  
>> okay
>> per JLS 11.2.3; this program is legal and compiles fine:
>>
>> public class Test {
>>    public static void main(String... args){
>>    try {
>>        ;
>>    } catch (Exception e) {
>>        ;
>>    }
>>    }
>> }
>>
>>     
>
> Thanks.  Amending the example to IOError.
>
>   
>> So what are the notions of identity and equality for method handles?
>>     
>
> Inherited from Object. Nothing special.
>
>   
>> [snip]
>>     
>>> 4.1 As specified above, the interface java.dyn.Dynamic has no
>>> supertypes or members.  As such, it is a bare reference type.  (As an
>>> arbitrary relation, the superclass of Dynamic[] is Object[].)  We
>>>
>>>       
>> Are there any other type building operations besides arrays we need to
>> worry about?
>>     
>
> I don't think so.
>
> List<Dynamic> is impossible for interesting reasons.  The (erased)  
> implementation of List internally makes use of Object.toString,  
> Object.equals, and perhaps other such methods.  These calls are wrong  
> for Dynamic values, since Dynamic (not being a subtype) does not  
> inherit Object.equals and the rest.  This allows a Dynamic object to  
> cleanly model another language, without holes in its method namespace.
>
> (Consider a process-oriented capability for which the name "wait" is  
> significant, or some knowledge representation language that has  
> different notions about "equals".  The MOP doesn't need to special- 
> case those names.  It's a small point but worth defending, I think.)
>
> (In C#, with reified types, they can customize their List<Dynamic> to  
> make a MOP-mediated call to equals, I suppose.)
>
>   
>>> But, the Java operators "==" "!=" "+" "+=" on reference types are
>>> clarified to apply only to reference types which are java.lang.Object
>>> or one of its subtypes; they do not have a predefined meaning if
>>> either operand is dynamic.  The "synchronized" and "throw" statements
>>> cannot be applied to dynamic expressions.
>>>
>>>       
>> So if there is no predefined meaning, are those operations illegal?
>>     
>
> Yes.  More specifically, they are reserved for future use, in case we  
> want to do something with dynamic operator overloading.
>
> (There's a half-baked sketch of what this could mean someday, on the  
> mlvm wiki.  It's not ready to discuss yet.)
>
>   
>>> Facilities which compute type relations (such as
>>> javax.lang.model.util.Types) may need to be updated to take Dynamic
>>> into account.  Generally speaking, the new Dynamic conversions  
>>> operate
>>> in parallel to the implicit boxing conversions.  That is, they add no
>>> new subtype or supertype relations, but they provide a few more ways
>>> for values to be implicitly converted or casted.
>>>
>>>       
>> Yes, I would expect a few changes to the type-related APIs.  They may
>> also need to be changes to programs that assume Object is the root of
>> the reference type hierarchy.  I know I've written annotation  
>> processing
>> code like that and Dynamic would need to be special cased in there.
>>     
>
> Thanks.
>
> As noted in the previous message, I have updated the proposal.
>
> -- John
>
>   



From forax at univ-mlv.fr  Thu Apr 30 12:07:50 2009
From: forax at univ-mlv.fr (=?ISO-8859-1?Q?R=E9mi_Forax?=)
Date: Thu, 30 Apr 2009 21:07:50 +0200
Subject: PROPOSAL: language support for JSR 292
In-Reply-To: <49F97577.4090002@sun.com>
References: <80FFB064-577D-4CEA-A93A-73C424AAE21B@sun.com>	<6F835C91-A2F2-4050-BD03-DB1B462C2B4F@sun.com>
	<49D5C7E3.50801@sun.com>	<2B41E202-273B-4876-BEB4-2C1BADA1A22E@Sun.COM>
	<49F97577.4090002@sun.com>
Message-ID: <49F9F706.3030909@univ-mlv.fr>

The first question is what is the goal of such construct.

If the goal is to be able to call any dynamic languages from Java,
this is in my opinion a nice dream but that means
mixing different language semantics.

If the goal is to help dynamic language developers,
the question is why a language developer code in Java
and not in its own language.

If the goal is to simplify reflection or dynamic invocation
in Java, the dynamic type of C# is what we want.

R?mi

Maurizio Cimadamore a ?crit :
> John Rose wrote:
>   
>> On Apr 3, 2009, at 1:25 AM, Joseph D. Darcy wrote:
>>
>>   
>>     
>>> Reiterating a point Neal raised, if Dynamic is not related to Object,
>>> what does that mean when Dynamic is used as the format type argument  
>>> to
>>> a type parameter?  What do "? extends Dynamic" and "? super Dynamic"
>>> mean to the type system?
>>>     
>>>       
>> It means something limited like ? extends String or ? super Object.   
>> I.e., there aren't any interesting types other than Dynamic itself  
>> that match the wildcard.
>>
>>   
>>     
> 1) I'd strongly recommend to forbid usage of InvokeDynamic type in the 
> following contexts:
>
> (i) extends clause (e.g. class MyDynamic extends InvokeDynamic)
> (ii) type-parameter bound (e.g. class Foo<X extends InvokeDynamic & 
> Comparable<?>>)
> (iii) wildcard type-argument (e.g. Foo<? extends InvokeDynamic)
>
> While generics/wildcards are essentially a way to refine static 
> type-checking, InvokeDynamic provides a way to disable static checking 
> completely. For this reason I don't see the two features going side by 
> side in any meaningful way. It is true that now that InvokeDynamic has 
> become an abstract holder of static methods, it probably makes less 
> sense to write code like the above (apart from (i) which users might be 
> tempted to write) - nevertheless the compiler should detect such invalid 
> usages and flag them as errors.
>
> My point is that a Java class shouldn't ever need to be parameterized on 
> something that is bound by InvokeDynamic (or Dynamic) - as those types 
> do not provide the type-system with any info.
>
> 2) I agree with Neal that the usage of Void feels a bit hacky. If you 
> need null values to be typed differently then I agree that probably 
> adding java.lang.Null would be the best thing to do, rather than 
> overriding the semantics of Void.
>
> 3) InvokeDynamic and type-inference. It seems like you can optionally 
> provide a type-parameter denoting the dynamic call's expected return 
> type. This is fine, as long as it is consistent with JLS 15.12.2.7 and 
> 15.12.2.8. In your examples it seems like the usage of such type 
> argument is completely optional. If specified, it provides additional 
> info about the dynamic call site such that, e.g. the following code will 
> be rejected:
>
> int i = InvokeDynamic.<String>myDynMethod("Hello!"); // type (String) -> 
> String
>
> Can this optional type argument be inferred so that the following method 
> call will behave identically?
>
> int i = InvokeDynamic.myDynMethod("Hello!"); // type (String) -> String
>
> [I did some testing and it seems like inference is not supported - the 
> above line will give an incompatible types error, found Object, expecetd 
> int]
>
> If so, you are mimicking an under-constrained type-variable (a method 
> type variable that cannot be inferred from actual arguments passed to 
> the method). This raises a question: what happens when the dynamic call 
> site does not appear within an assignment context, e.g.
>
> InvokeDynamic.myDynMethod("Hello!");
>
> or
>
> int i = (Integer)InvokeDynamic.myDynMethod("Hello!");
>
> In those cases, following 15.12.2.8, the under-constrained type variable 
> should be inferred to be its declared bound. What does it mean in this 
> case? Object ? Null ? Reading from your examples it seems like if no 
> optional type-argument for the return type is provided, no info about 
> the return type is included in the MethodHandle type generated by javac. 
> Which means that this behavior cannot be explained in terms of generic 
> method call/type inference (and thus 15.12.2.7/15.12.2.8).
>
> An alternative would be to pass to InvokeDynamic the return type Class 
> object corresponding the to expected return type as the first parameter 
> of the dynamic call:
>
> InvokeDynamic.myDynMethod(int.class, "Hello!"); // type (String) -> int
>
> This has the advantage of not requiring a separate language extension in 
> order to allow primitive type (and void) to be specified as parameter types.
>
> Maurizio
>   
>>> Actually there is a special rule that catching Exception is always  
>>> okay
>>> per JLS 11.2.3; this program is legal and compiles fine:
>>>
>>> public class Test {
>>>    public static void main(String... args){
>>>    try {
>>>        ;
>>>    } catch (Exception e) {
>>>        ;
>>>    }
>>>    }
>>> }
>>>
>>>     
>>>       
>> Thanks.  Amending the example to IOError.
>>
>>   
>>     
>>> So what are the notions of identity and equality for method handles?
>>>     
>>>       
>> Inherited from Object. Nothing special.
>>
>>   
>>     
>>> [snip]
>>>     
>>>       
>>>> 4.1 As specified above, the interface java.dyn.Dynamic has no
>>>> supertypes or members.  As such, it is a bare reference type.  (As an
>>>> arbitrary relation, the superclass of Dynamic[] is Object[].)  We
>>>>
>>>>       
>>>>         
>>> Are there any other type building operations besides arrays we need to
>>> worry about?
>>>     
>>>       
>> I don't think so.
>>
>> List<Dynamic> is impossible for interesting reasons.  The (erased)  
>> implementation of List internally makes use of Object.toString,  
>> Object.equals, and perhaps other such methods.  These calls are wrong  
>> for Dynamic values, since Dynamic (not being a subtype) does not  
>> inherit Object.equals and the rest.  This allows a Dynamic object to  
>> cleanly model another language, without holes in its method namespace.
>>
>> (Consider a process-oriented capability for which the name "wait" is  
>> significant, or some knowledge representation language that has  
>> different notions about "equals".  The MOP doesn't need to special- 
>> case those names.  It's a small point but worth defending, I think.)
>>
>> (In C#, with reified types, they can customize their List<Dynamic> to  
>> make a MOP-mediated call to equals, I suppose.)
>>
>>   
>>     
>>>> But, the Java operators "==" "!=" "+" "+=" on reference types are
>>>> clarified to apply only to reference types which are java.lang.Object
>>>> or one of its subtypes; they do not have a predefined meaning if
>>>> either operand is dynamic.  The "synchronized" and "throw" statements
>>>> cannot be applied to dynamic expressions.
>>>>
>>>>       
>>>>         
>>> So if there is no predefined meaning, are those operations illegal?
>>>     
>>>       
>> Yes.  More specifically, they are reserved for future use, in case we  
>> want to do something with dynamic operator overloading.
>>
>> (There's a half-baked sketch of what this could mean someday, on the  
>> mlvm wiki.  It's not ready to discuss yet.)
>>
>>   
>>     
>>>> Facilities which compute type relations (such as
>>>