RFR: 8359936: StableValues can release the underlying function after complete computation [v6]

[Viktor Klang]

On Wed, 13 Aug 2025 11:51:29 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> This PR proposes to release the underlying function if a stable function or collection has invoked its underlying supplier exhaustively so that it can be collected.
>> 
>> This PR passes tier1, tier2, and tier3 testing on multiple platforms.
>
> Per Minborg has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Update src/java.base/share/classes/jdk/internal/lang/stable/StableFunction.java
>    
>    Co-authored-by: Viktor Klang <viktor.klang at oracle.com>
>  - Update src/java.base/share/classes/jdk/internal/lang/stable/StableEnumFunction.java
>    
>    Co-authored-by: Viktor Klang <viktor.klang at oracle.com>

src/java.base/share/classes/java/util/ImmutableCollections.java line 140:

> 138:                 public <E> List<E> stableList(int size, IntFunction<? extends E> mapper) {
> 139:                     // A stable list is not Serializable, so we cannot return `List.of()` if `size == 0`
> 140:                     return new StableList<>(size, new UnderlyingHolder<>(mapper, size));

I personally think it's better (if possible) that the constructor instantiates the UnderlyingHolder, it also makes it much more tractable to ensure that there's consistency between what's in the class and what goes into the UnderlyingHolder.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25878#discussion_r2273312209