RFR(m): 8177290 add copy factory methods for unmodifiable List, Set, Map

[Roger Riggs]

Hi Stuart,

I'm cautious about doing work piecemeal toward immutable collections.
The current unmodifiable approach only gives partial protection to the 
caller
and none to the callee. The assertions it makes are too weak to be useful.

I think more value can be achieved by creating concrete final immutable 
collections
that applications can use to be certain that the semantics of the collection
are immutable. They can implement the current interfaces but would be 
compile time
knowable of the complete semantics of mutability.  Then a good bridge 
between
the current streams (and collections) would be methods that return the 
concrete final collections.

BTW, I don't think many people are confused by 'immutable' collections 
appearing
to be mutated because one of the objects in the collection is mutable.

Thanks, Roger


On 9/21/2017 2:55 PM, Stuart Marks wrote:
>
>
> On 9/21/17 5:42 AM, Alan Bateman wrote:
>> On 21/09/2017 01:02, Stuart Marks wrote:
>>> http://cr.openjdk.java.net/~smarks/reviews/8177290/webrev.0/
>> I read through the updated/new definitions and they read well.
>
> Great.
>
>> For the copyOf methods then I can't immediately tell from the javadoc 
>> if the
>> given collection can contain null elements. Taking List.copyOf as an 
>> example
>> where coll may be null or it may contain null elements. The javadoc 
>> does link to
>> "Unmodifiable lists" where it specifies the characteristics of the lists
>> returned by the static factory methods - these include disallowing null
>> elements. So I think this needs to be clarified.
>
> Agreed, I'll work on some clarifications here, and also disallow null 
> for the argument itself.
>
>> Minimal implementation is okay to get started but what is the reason 
>> not to
>> include some basic tests?
>
> Sorry, I should have been more clear about this. The changeset is 
> clearly not ready to go in as it stands. I wanted to get an initial 
> review of the specifications going, then file a CSR request, etc. 
> while continuing to work on tests and better implementations. I'll 
> post a subsequent review when they're ready.
>
> Thanks.
>
> s'marks
>