RFR: 8334015: Add Support for UUID Version 7 (UUIDv7) defined in RFC 9562 [v13]

[Kieran Farrell]

On Thu, 4 Sep 2025 21:17:32 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

>> Kieran Farrell has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   update <strong> note to @api note
>
> test/jdk/java/util/UUID/UUIDTest.java line 52:
> 
>> 50:         unixEpochTimeMillisTest();
>> 51:         unixEpochTimeMillisTest_Multi();
>> 52:         unixEpochTimeMillis_userInputTest();
> 
> Also rename the tests to use the `epochMillis` naming.

Thanks Roger, I have updated the name accordingly. WRT updating the implementation to use nextLong(), since we are no longer using the higher percision bits in the first half of the UUID, we are using random bits in their place, so we would need to call `nextLong` twice and overwrite with the timestamp etc. if I understand correctly. From what ive seen in the microbenchmarks, this results in a large perfomance dec.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25303#discussion_r2337765286