RFR: 8254782: Fix benchmark issues in java/lang/StringIndexOfChar.java benchmark [v2]

[Jason Tatton]

> Please review the improvements which I have made to the java/lang/StringIndexOfChar.java jmh benchmark. Please let me know if any further improvements are required.
> 
> Thanks,
> Jason

Jason Tatton has updated the pull request incrementally with one additional commit since the last revision:

  Adjusted benchmark to use BlackHole and improved String array syntax as advised

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/918/files
  - new: https://git.openjdk.java.net/jdk/pull/918/files/5f3a1ce7..07485356

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=918&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=918&range=00-01

  Stats: 73 lines in 1 file changed: 1 ins; 32 del; 40 mod
  Patch: https://git.openjdk.java.net/jdk/pull/918.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/918/head:pull/918

PR: https://git.openjdk.java.net/jdk/pull/918