RFR: 8288723: Avoid redundant ConcurrentHashMap.get call in java.time [v4]

[Andrey Turbanov]

> Instead of separate ConcurrentHashMap.get call, we can use result of previous putIfAbsent call.

Andrey Turbanov has updated the pull request incrementally with one additional commit since the last revision:

  8288723: Avoid redundant ConcurrentHashMap.get call in java.time
  
  revert 'computeIfAbsent' when it requires custom key class.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9208/files
  - new: https://git.openjdk.org/jdk/pull/9208/files/70223b4b..94f57445

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9208&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9208&range=02-03

  Stats: 11 lines in 1 file changed: 5 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/9208.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9208/head:pull/9208

PR: https://git.openjdk.org/jdk/pull/9208