RFR: 8315999: Improve Date toString performance

[Chen Liang]

On Mon, 11 Sep 2023 13:45:43 GMT, 温绍锦 <duke at openjdk.org> wrote:

> After PR #15651 is merged, changes will be made based on the new API. Until then, you can help review other changes.

I mean, OpenJDK's GitHub bots has a special handling system that allows you to include code from #15651 in this PR:

1. Merge your local [reduce_duplicate](https://github.com/wenshao/jdk/tree/reduce_duplicate) branch into your optimization date to string branch
2. Edit PR title <img width="1237" alt="image" src="https://github.com/openjdk/jdk/assets/7806504/d8b65b6d-3d33-4dab-9b86-ba2f1601d82e">
3. Change PR branch <img width="1222" alt="image" src="https://github.com/openjdk/jdk/assets/7806504/6a2b5301-2316-4e6f-9251-0a745dfa0668">

Then OpenJDK bot will automatically add that you have a prerequisite in the issue body, and after merging #15651, this PR will automatically target against master again.

The main advantage is that PR's "File changed" on GitHub and webrevs will not include changes from #15651, so we can save review time and you don't have to update this PR after #15651 is merged.

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OpenJDK的GitHub机器人能自动处理有前置依赖的补丁：
1、先把 #15651 的[reduce_duplicate](https://github.com/wenshao/jdk/tree/reduce_duplicate)Git分支合并到你现在这个[optim_for_date_to_string_2](https://github.com/wenshao/jdk/tree/optim_for_date_to_string_2)分支里面，上传
2、按Pull Request的标题边上的"Edit"修改按钮，可以修改对应分支
3、把目标分支修改为`pr/15651`

这样下来OpenJDK机器人会自动标注你这个补丁的前置依赖，然后依赖合并（integrated）后会自动把目标分支重新改为master。

这个的优点是"Files changed"文件改动页面不会显示前置依赖的变动，review更方便，同时你也不用在前置合并后重新改代码。

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PR Comment: https://git.openjdk.org/jdk/pull/15658#issuecomment-1713964226