RFR: JDK-8310913 Move ReferencedKeyMap to jdk.internal so it may be shared [v8]

[Jim Laskey]

On Tue, 18 Jul 2023 14:56:53 GMT, Chen Liang <liach at openjdk.org> wrote:

>> Jim Laskey has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Update test to check for gc.
>
> src/java.base/share/classes/jdk/internal/util/ReferencedKeyMap.java line 354:
> 
>> 352:      */
>> 353:     @SuppressWarnings("unchecked")
>> 354:     K intern(K key) {
> 
> Should this be made static for type safety?
> 
> public static <E> E intern(ReferencedKeyMap<E, ReferenceKey<E>> m, E key)
> 
> which will save the 2 unchecked casts at `get` and `putIfAbsent`.
> 
> 
> In addition, it would be nice if we can compute a more proper key for interning than the query key, via a binary operator; for example, we want a `String` to go through `String::intern`, or a `BaseLocale` to format its language, script, region, and variant and intern them (see https://github.com/openjdk/jdk/pull/14404/files#diff-c0e20847ffb6e33bcf62ff52b1b5b4c8a85520ca101a6f54128d97289cd8c2f9R169-R172)

Changing.

> src/java.base/share/classes/jdk/internal/util/ReferencedKeySet.java line 71:
> 
>> 69:  * @param <T> the type of elements maintained by this set
>> 70:  */
>> 71: public class ReferencedKeySet<T> extends AbstractSet<T> {
> 
> Suggestion:
> 
> public final class ReferencedKeySet<T> extends AbstractSet<T> {
> 
> Make this class final.

Changing.

> src/java.base/share/classes/jdk/internal/util/ReferencedKeySet.java line 185:
> 
>> 183:      * @return the old element if present, otherwise, the new element
>> 184:      */
>> 185:     public T intern(T e) {
> 
> I would like to see an additional `T intern(T e, UnaryOperator<T> internFunction)`, where the `internFunction` behaves like `LocalObjectCache::normalizeKey`.

This was a bit tricky. Lambdas can't be used in phase1 so messed when MethodType kicked in. So I created two paths, one for normal and one for the UnaryOperator.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14684#discussion_r1268104420
PR Review Comment: https://git.openjdk.org/jdk/pull/14684#discussion_r1268104006
PR Review Comment: https://git.openjdk.org/jdk/pull/14684#discussion_r1268108150