RFR: 8316493: Make immutable maps @ValueBased [v5]

[Per Minborg]

On Tue, 19 Sep 2023 23:48:07 GMT, Chen Liang <liach at openjdk.org> wrote:

>> src/java.base/share/classes/java/util/AbstractMap.java line 375:
>> 
>>> 373:      */
>>> 374:     public Collection<V> values() {
>>> 375:         return new AbstractCollection<>() {
>> 
>> Note that this causes `m.values().equals(m.values())` to no longer return `true`, as base `Collection::equals` is defined using reference equality.
>
> Looking at the specification above: 
>> No synchronization is performed, so there is a slight chance that multiple calls to this method will not all return the same collection.
> 
> This should be an acceptable change to behavior.

This is brought to attention in the CSR.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15614#discussion_r1364066788