RFR: 8366178: Implement JEP 526: Lazy Constants (Second Preview) [v25]

[Maurizio Cimadamore]

On Wed, 12 Nov 2025 10:07:39 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> Implement JEP 526: Lazy Constants (Second Preview)
>> 
>> The lazy list/map implementations are broken out from `ImmutableCollections` to a separate class.
>> 
>> The old benchmarks are not moved/renamed to allow comparison with previous releases.
>> 
>> `java.util.Optional` is updated so that its field is annotated with `@Stable`.  This is to allow `Optional` instances to be held in lazy constants and still provide constant folding.
>
> Per Minborg has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 112 commits:
> 
>  - Clarify toString spec
>  - Merge branch 'master' into lazy-constants
>  - Add @AOTSafeClassInitializer
>  - Address comments in PR
>  - Fix merge mistake
>  - Merge master
>  - Rework toString implementations
>  - Update after doc comments
>  - Merge branch 'master' into lazy-constants
>  - Revert the AbstractMap.keySet @Stable annotation
>  - ... and 102 more: https://git.openjdk.org/jdk/compare/76a1109d...1f439bec

Looks great -- just a couple more javadoc tweaks ;-)

src/java.base/share/classes/java/util/List.java line 1233:

> 1231:      * The returned list's {@linkplain Object#equals(Object) equals()} and
> 1232:      * {@linkplain Object#hashCode() hashCode()} methods may trigger initialization of one
> 1233:      * or more lazy elements. The returned list's {@linkplain Object#toString() toString()}

I thought we have concluded that all Object methods should behave as those in any other list, to maximize migration opportunities.

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PR Review: https://git.openjdk.org/jdk/pull/27605#pullrequestreview-3464050345
PR Review Comment: https://git.openjdk.org/jdk/pull/27605#discussion_r2526787780