RFR: 8337168: Optimize LocalDateTime.toString

[Shaojin Wen]

On Thu, 25 Jul 2024 05:06:17 GMT, Shaojin Wen <duke at openjdk.org> wrote:

> The current LocalDateTime.toString implementation concatenates the toString results of date and time, which can be passed to StringBuilder to reduce additional object allocation and improve performance.

Below are the performance numbers running on a MacBook M1 Max, which increased speed by +179.88%


-# master 05d88de05e9b7814ecd5517aacd17f0feafdff3c
-Benchmark                             Mode  Cnt  Score   Error   Units
-ToStringBench.localDateTimeToString  thrpt   15  4.896 ? 1.414  ops/ms

+# current c03ed26ffdf2cebcc9074c2aeae27fbb1f49c025
+Benchmark                             Mode  Cnt   Score   Error   Units
+ToStringBench.localDateTimeToString  thrpt   15  13.703 ? 1.960  ops/ms +179.88%

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PR Comment: https://git.openjdk.org/jdk/pull/20321#issuecomment-2249546065