RFR: 8351565: Implement JEP 502: Stable Values (Preview) [v33]

[Chen Liang]

On Wed, 2 Apr 2025 14:31:46 GMT, Viktor Klang <vklang at openjdk.org> wrote:

>> src/java.base/share/classes/java/lang/StableValue.java line 455:
>> 
>>> 453:      *         provided to the {@link #orElseSet(Supplier)} method.
>>> 454:      */
>>> 455:     boolean trySet(T content);
>> 
>> I assume the intent is that trySet can only return at most true once but the current wording suggests that two threads racing to set the same content would return true, or sequential calls to trySet to set the same content would return true. Does this need to be clarified?
>
> I second this

So maybe "was set to the provided content" -> "was set by this call"

>> src/java.base/share/classes/java/lang/StableValue.java line 494:
>> 
>>> 492:      * <p>
>>> 493:      * The provided {@code supplier} will only be invoked once even if invoked from
>>> 494:      * several threads unless the {@code supplier} throws an exception.
>> 
>> Is this the supplier instance or any supplier? Just wondering about the case where two threads are invoke it with different instances (for whatever reason), I can't tell from the javadoc.
>
> Seconded

I personally think this is more of an implementation artifact for `StableValue::supplier` and doesn't merit its own API (as no other StableValue API utilizes the object monitor of a StableValue), but maybe we can adjust this in a later preview...

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PR Review Comment: https://git.openjdk.org/jdk/pull/23972#discussion_r2025846922
PR Review Comment: https://git.openjdk.org/jdk/pull/23972#discussion_r2025850569