RFR: 8297519: Improve expressions and modernise code [v2]

[Per Minborg]

> During the work of another PR (https://github.com/openjdk/jdk/pull/11260), several improvement areas were identified. These are now adressed in this separate PR proposing the use of more modern Java constructs as well as simplifying a large number of logical expressions that were previously non-normative. 
> 
> 
> This branch has been tested and passed tier1-4 tests.

Per Minborg has updated the pull request incrementally with one additional commit since the last revision:

  Update from the first round of comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/11348/files
  - new: https://git.openjdk.org/jdk/pull/11348/files/9922ece1..8bfb4ad8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11348&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11348&range=00-01

  Stats: 31 lines in 5 files changed: 0 ins; 5 del; 26 mod
  Patch: https://git.openjdk.org/jdk/pull/11348.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11348/head:pull/11348

PR: https://git.openjdk.org/jdk/pull/11348