RFR: JDK-8310502 : Optimization for j.l.Long.fastUUID() [v21]

[ExE Boss]

On Fri, 23 Jun 2023 11:24:23 GMT, 温绍锦 <duke at openjdk.org> wrote:

>> By optimizing the implementation of java.lang.Long#fastUUID, the performance of the java.util.UUID#toString method can be significantly improved.
>> 
>> The following are the test results of JMH: 
>> 
>> Benchmark                     Mode  Cnt      Score      Error   Units
>> UUIDUtilsBenchmark.new       thrpt    5  92676.550 ±  292.213  ops/ms
>> UUIDUtilsBenchmark.original  thrpt    5  37040.165 ± 1023.532  ops/ms
>
> 温绍锦 has updated the pull request incrementally with one additional commit since the last revision:
> 
>   format code

src/java.base/share/classes/java/lang/Long.java line 493:

> 491:                         | H256[((int) lsb) & 0xff]);
> 492: 
> 493:         return new String(buf, LATIN1);

Note that this isn’t correct when `COMPACT_STRINGS` is `false`, as then `buf` is always interpreted as having a `coder` of `UTF16`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14578#discussion_r1240231921