[lworld] RFR: 8294312: [lworld] Add java.util.Objects.isIdentityObject [v2]

[Mandy Chung]

On Thu, 29 Sep 2022 19:44:16 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

>> Add `java.util.Objects.isIdentityObject(obj)` and update tests.
>> 
>> Correct j.l.Class.isIdentity() and .isValue() to correctly identify all arrays as identity objects.
>> (The modifiers for array classes do have not reliable ACC_IDENTITY or ACC_VALUE bits).
>> 
>> Updated ValhallaFeaturesTest to use junit.
>
> Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Review comment updates related to ValhallaFeatures.isEnabled().
>   And javadoc cleanup

Looks okay in general.   A couple minor comments.

src/java.base/share/classes/java/lang/Class.java line 645:

> 643:      * @since Valhalla
> 644:      */
> 645:     public boolean isIdentity() {

The javadoc for `isIdentity` should specify if this Class is an array class, primitive type or `void`.

src/java.base/share/classes/java/lang/Class.java line 657:

> 655:      */
> 656:     public boolean isValue() {
> 657:         return ValhallaFeatures.isEnabled() &&  // Before Valhalla no classes are value classes

`isValue` does not need to check `-XX:+EnableVahalla` since the new `VALUE` flag can only be set in a value class and if the feature is enabled.

src/java.base/share/classes/java/lang/Object.java line 39:

> 37:  * including arrays, implement the methods of this class.
> 38:  * <p>
> 39:  * Subclasses of {@code java.lang.Object} can be either identity classes or value classes.

suggest to add a link to `Class::isIdentity` and `Class::isValue`

src/java.base/share/classes/java/util/Objects.java line 194:

> 192: 
> 193:    /**
> 194:     * {@return {@code true} if the object is an identity object, otherwise {@code false}}

nit: s/the object/the specified object/

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PR: https://git.openjdk.org/valhalla/pull/770