RFR: 8311207: Cleanup for Optimization for UUID.toString [v14]

[Claes Redestad]

On Sat, 9 Sep 2023 07:59:30 GMT, 温绍锦 <duke at openjdk.org> wrote:

>> Perhaps you could extract the `digitPair` method you're adding in #15555 to a separate PR and use that to remove `HexDigits::DIGITS`?
>
> Please help me create an issue, and I will submit a new PR to modify it.

Filed https://bugs.openjdk.org/browse/JDK-8315968 - we should also get @JimLaskey to weigh in here (who's recently authored the `java.util.Digits` code). Tl;dr: I think it'd be good to consolidate and share the code to produce these packed digit pairs.

Also note that there might be some issues on big-endian systems with recent changes, so let's figure that out first: https://bugs.openjdk.org/browse/JDK-8310929

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PR Review Comment: https://git.openjdk.org/jdk/pull/14745#discussion_r1320788026