RFR: 8315585: Optimization for decimal to string [v7]

[Claes Redestad]

On Mon, 16 Oct 2023 15:00:42 GMT, Shaojin Wen <duke at openjdk.org> wrote:

>> I submitted PR #15555 before, and there were too many changes. I split it into multiple PRs with small changes. This one is one of them.
>> 
>> this PR removed the duplicate code for getChars in BigDecimal#StringBuilderHelper, i also make performance faster.
>> Please review and don't hesitate to critique my approach and patch.
>
> Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Use StringConcatFactory.makeConcatWithConstants

I think it would be better to consider this change to `String.getBytes` separately and evaluate it on more platforms and on more benchmarks. I don't think action on that should block this PR. In fact if you go with the simpler recipe (`"\1.\1\1"`) the `BigDecimals.testSmallToEng` becomes a good test case to verify such an optimization in a later RFE.

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PR Comment: https://git.openjdk.org/jdk/pull/16006#issuecomment-1766598900