JDK-8300691 - final variables in for loop headers should accept updates

[Tagir Valeev]

Hello!



On Tue, Dec 10, 2024, 18:57 Archie Cobbs <archie.cobbs at gmail.com> wrote:

> On Fri, Oct 25, 2024 at 10:02 AM Archie Cobbs <archie.cobbs at gmail.com>
> wrote:
>
>> Is there some quasi-consensus to go forward with this idea for fixing
>> basic for() loops?
>>
>
> (Hmm, nobody responded yes and nobody responded no...)
>

Just for the record: I previously said that I don't think we should salvage
classic for loop, because it's awful. Instead, we should invest into adding
first-class ranges to Java, or at least library support, to be able to
write something like

for(int i: rangeClosed(1, 3)) {
...
}

This way, the lambda problem will be solved automatically, and people will
get much more readable and much less errorprone way to iterate over
integers.

I still stick to this point of view.

With best regards,
Tagir Valeev


> Now that JDK 24 is out of the way, I'd like to get some kind of final
> adjudication on whether to continue pursuing this idea from this list.
>
> If everyone is good with doing this then I'm happy to continue working on
> it, otherwise I'm happy to shelve it. I would just like to tie up the loose
> end one way or another.
>
> To recap: the idea is to allow loop variables declared in basic (old
> style) for() loops to be captured in the body of the loop as long as they
> are not reassigned in the body of the loop (but they may be reassigned in
> the loop step). For example:
>
> for (int i = 1; i <= 3; i++) {
>     Runnable r = () -> System.out.println(i);   // allow this
> }
>
> There was lots of good discussion and we did narrow down the idea to
> what's described above. However I'm unclear on whether to now proceed with
> asking for additional reviews, etc. and don't want to presume.
>
> If nobody replies I won't ask again :)
>
> FWIW here's what has been drafted so far (all subject to improvement of
> course):
>
> Bug: https://bugs.openjdk.org/browse/JDK-8341782
> CSR: https://bugs.openjdk.org/browse/JDK-8341783
> JEP: https://bugs.openjdk.org/browse/JDK-8341785
> JLS: https://bugs.openjdk.org/browse/JDK-8341786
> PR: https://github.com/openjdk/jdk/pull/21415
>
> Thanks,
> -Archie
>
> --
> Archie L. Cobbs
>
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