RFR: 8284637: Improve String.join performance

[XenoAmess]

On Mon, 11 Apr 2022 20:15:08 GMT, XenoAmess <duke at openjdk.java.net> wrote:

> Is there jmh test data to quantify the improvement?

@RogerRiggs added jmh now.

Is there any test suite to run it but not run other jmh tests? Or I must invoke the jmh jar using commandline myself to achieve it?

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PR: https://git.openjdk.java.net/jdk/pull/8169