[lworld] RFR: 8346307: [lworld] Clarify identity vs value in Class, Objects, and document limitations of value objects [v4]

[Roger Riggs]

On Sun, 16 Feb 2025 15:15:14 GMT, Chen Liang <liach at openjdk.org> wrote:

>> src/java.base/share/classes/java/lang/Class.java line 713:
>> 
>>> 711:     @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS, reflective=true)
>>> 712:     public boolean isValue() {
>>> 713:         return PreviewFeatures.isEnabled() ? !isIdentity() : false;
>> 
>> Is there a reason this isn't just `PreviewFeatures.isEnabled() && !isIdentity()`?
>
> Indeed, this API is returning `false` for interfaces and primitive types if preview features are not enabled, which is wrong. Making it simply return `!isIdentity()` may be better and conforms to the javadoc specification here. See https://github.com/openjdk/valhalla/blob/991ec927a2a111e5021b12be3413dfc96efbc74a/src/hotspot/share/prims/jvm.cpp#L1333-L1337

Corrected in 68dd3fb675d0f87da8de2bc7525d5bcc2a87dac1

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1327#discussion_r1962271307