list literal gotcha and suggestion

[Rémi Forax]

Le 08/10/2009 00:13, Reinier Zwitserloot a écrit :
> The recent activity on this list consisted of Neal and I swapping one-
> liners. That doesn't really make the case for 'growing consensus of
> inadequacy'.
>
> You ask interesting questions, none of which have  been handled in
> this spinoff discussion on using {} syntax for all different forms of
> literals, together with pseudo target typing.
>
> My answers:
>
> Q: Should the syntax of initializing remain uniform in Java?
>
> A: Obviously not; I dont think anybody is considering "new Foo[]
> { foo1, foo2, foo3};" to be a decent syntax for a _list_ literal. I'm
> guessing that's not what you meant, though. Rephrase the question?
>
> Q: are new static methods a decent enhancement regardless of this
> proposal?
>
> A: Yes. [Note copious use of google collections API. Also, it's
> obvious that Collections.unmodifiableList(Arrays.asList(item1, item2,
> item3)); is idiotic, and yet commonly used. Clearly something that
> needs fixing.]
>
> Q: Are collection literals immutable or mutable?
>
> A: Immutable. Because immutables win.
>
> Q: Can operations be performed on the collection literal? 3.toString()
> is illegal -- why would { 1, 2 }.toSet() ?
>
> A: Unless you propose that "FooBar".toLowerCase(); is to be made
> illegal, I don't really get your point here. Of course {1, 2}.toSet()
> should be legal. The reason "3.toString()" is not legal is because
> autoboxing doesn't work that way. {1, 2} is a list. It's not a vague
> unspecified type I'll christen a "NealCollection" which has no methods
> until it converts to something. Neal's point that "3" is a special
> integer that is assign-type compatible to a byte has no relation
> whatsoever to the fact that "3.toString()" doesn't work. That's an
> autoboxing issue. Autoboxing was a complicated but neccessary evil.
> Let's not introduce them to list literals where they aren't neccessary.
>    

To rewrite what I have understand from Neal's mails:
If these lines are legals:
List<Integer> list = {1, 2};
Set<Integer> set = {1, 2};

then {1, 2}.toString() can be illegal because
{1, 2} is a an untyped collection litteral.


>    --Reinier Zwitserloot
>    

Rémi

>
>
> On 2009/07/10, at 22:55, Paul Benedict wrote:
>
>    
>> Reinier,
>>
>> I am glad serious opposition doesn't have a time limit. The recent
>> activity on the list indicates, at least to me, that there is growing
>> consensus that the current proposal is inadequate. Those raising
>> issues (definitely more than two) have made very good arguments on the
>> limitations and pit-falls of the current syntax. Regardless,
>> intentions are good. The discussion is driving towards enhancing and
>> correcting -- not torpedoing -- the proposal.
>>
>> As things stand, these are the issues:
>> * Should the syntax of initializing remain uniform in Java?
>> * Are new static methods a decent enhancement regardless of this
>> proposal?
>> * Are collection literals immutable or mutable?
>> * Can operations be performed on the collection literal? 3.toString()
>> is illegal -- why would { 1, 2 }.toSet() ?
>>
>> Paul
>>
>>      
>
>