RFR: 8340572: ConcurrentModificationException when sorting ArrayList sublists

[David Holmes]

On Sun, 29 Sep 2024 17:44:30 GMT, Attila Szegedi <attila at openjdk.org> wrote:

> Fixes a regression with #17818 where `ArrayList.subList(…).sort()` started incrementing `ArrayList.modCount` resulting in some cases throwing a `ConcurrentModificationException` where none was thrown before.
> 
> This change keeps the optimization from #17818 but restores the behavior where only sorting the `ArrayList` changes the mod count, but sorting its sublists does not.

I agree with just reverting the behaviour as discussed in JBS, but will leave the actual review for the libs folk. The more general question of when to trigger CME is a very thorny one.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/21250#issuecomment-2384699577