RFR: 8315968: Consolidate java.util.Digits and StringLatin1::PACKED_DIGITS [v6]

[温绍锦]

On Mon, 11 Sep 2023 10:33:10 GMT, 温绍锦 <duke at openjdk.org> wrote:

>> These weren't in `java.util.DecimalDigits` but have been copied from `java.lang.StringLatin1` - part of an unfinished refactoring? There's no clear-cut answer where these best fits but it seems reasonable to keep them in `StringLatin1` and `StringUTF16` respectively.
>
>> It's unused now. Do we expect usages to be added in following PRs?
> 
> I plan to provide the getChars method in this PR and use it in my other PR #15555. I also plan to submit another PR to optimize java.time toString, and I will also use this method. https://github.com/wenshao/jdk/commit/cc82e8c11aeb27c0f8581363f7133c85f6022ca1

> These weren't in `java.util.DecimalDigits` but have been copied from `java.lang.StringLatin1` - part of an unfinished refactoring? There's no clear-cut answer where these best fits but it seems reasonable to keep them in `StringLatin1` and `StringUTF16` respectively.

StringLatin1.getChars has been moved to DecimalDigits.getCharsLatin1

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PR Review Comment: https://git.openjdk.org/jdk/pull/15651#discussion_r1321461917