RFR: 8351565: Implement JEP 502: Stable Values (Preview)

[Per Minborg]

On Tue, 11 Mar 2025 00:40:31 GMT, Johannes Graham <duke at openjdk.org> wrote:

>> Indeed, a bit set predicate can be used to check input validity if it is necessary - I think for enums, using a `StableFunction.ofEnum` dedicated API might be better just because `StableValue` can access `Class.getEnumConstantsShared` easily.
>
> What if instead you had a `@Stable` array of Object of the appropriate size, and populated each cell with a StableValue if the corresponding index was in the set, otherwise used a sentinel value. Then on the lookup, if it was the sentinel you throw, else you use the the SV.
> 
> Also there is an awful lot of similarity between the enum function and the int function. Could one possibly be implemented using the other?

Thanks for spotting this glitch. I have fixed the issue and added a test for member sets with "holes".

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PR Review Comment: https://git.openjdk.org/jdk/pull/23972#discussion_r1988707099