RFR: 8351565: Implement JEP 502: Stable Values (Preview) [v56]

[Per Minborg]

On Thu, 17 Apr 2025 09:24:13 GMT, Viktor Klang <vklang at openjdk.org> wrote:

>> Per Minborg has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Address comments on original vs underlying
>
> src/java.base/share/classes/java/lang/StableValue.java line 204:
> 
>> 202:  *         Set.of(1, 2, 4, 8, 16, 32);
>> 203:  *     private static final UnaryOperator<Integer> UNDERLYING_LOG2 =
>> 204:  *         i -> 31 - Integer.numberOfLeadingZeros(i);
> 
> Would boxing be necessary—i.e. what would be needed to use java.util.function.IntUnaryOperator?

Boxing would be required in this example.  It would have been possible to provide a lambda that invoked an underlying `IntUnaryOperator`.


            private static final IntUnaryOperator LOG2_ORIGINAL =
                    i -> 31 - Integer.numberOfLeadingZeros(i);

            private static final Function<Integer, Integer> LOG2_CACHED =
                    // @link substring="function" target="#function(Set,Function)" :
                    StableValue.function(CACHED_KEYS, LOG2_ORIGINAL::applyAsInt);


Writing a custom stable `IntUnaryOperator` is out of scope. At least in the first preview. I am planning on writing an article about that.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23972#discussion_r2053750795