RFR: JDK-8314194: Reusing CyclicBarrier, it should be possible to change the barrierCommand

[chenggwang]

eg:5 individuals in the first round of written exams,ending with a ranking based on everyone's score points; and a second round of interviews, with a ranking based on the average of the three interviewers' scores;The two rounds of ranking methods are the barrierCommand, and they are different

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Commit messages:
 - Set new barrierCommand under a new generation

Changes: https://git.openjdk.org/jdk/pull/15239/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15239&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314194
  Stats: 49 lines in 1 file changed: 47 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/15239.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15239/head:pull/15239

PR: https://git.openjdk.org/jdk/pull/15239