RFR: 8276186: Require getAvailableLocales() methods to include Locale.ROOT [v2]

[Stuart Marks]

On Wed, 10 Nov 2021 19:05:17 GMT, Naoto Sato <naoto at openjdk.org> wrote:

>> This fix is to require to include `Locale.ROOT` in the returned arrays/set from `getAvailableLocales()` methods in various locale-sensitive classes. The implementation has been including `Locale.ROOT` since its inception, it is simply a doc clarification (+ a test case verifying it). Corresponding CSR has also been drafted: https://bugs.openjdk.java.net/browse/JDK-8276249
>
> Naoto Sato has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Using @code tag for `Set`.

Nice use of MethodHandles.lookup() in the test.

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Marked as reviewed by smarks (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/6258