RFR: 8258422: Cleanup unnecessary null comparison before instanceof check in java.base [v2]

[Andrey Turbanov]

> 8258422: Cleanup unnecessary null comparison before instanceof check in java.base

Andrey Turbanov has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - 8258422: Cleanup unnecessary null comparison before instanceof check in java.base
   use instanceof pattern matching
 - 8258422: Cleanup unnecessary null comparison before instanceof check in java.base

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/20/files
  - new: https://git.openjdk.java.net/jdk/pull/20/files/f09bbd24..603cd364

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=20&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=20&range=00-01

  Stats: 784681 lines in 7664 files changed: 596718 ins; 128884 del; 59079 mod
  Patch: https://git.openjdk.java.net/jdk/pull/20.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/20/head:pull/20

PR: https://git.openjdk.java.net/jdk/pull/20