RFR: 8375561: Class NGGroup is in need of some cleanup [v3]

[Christopher Schnick]

> This should improve the code quality of the class while preserving its original workings

Christopher Schnick has updated the pull request incrementally with one additional commit since the last revision:

  Remove unused field and not reachable code

-------------

Changes:
  - all: https://git.openjdk.org/jfx/pull/2043/files
  - new: https://git.openjdk.org/jfx/pull/2043/files/898af0f9..d29fcc80

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=2043&range=02
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=2043&range=01-02

  Stats: 55 lines in 1 file changed: 0 ins; 50 del; 5 mod
  Patch: https://git.openjdk.org/jfx/pull/2043.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/2043/head:pull/2043

PR: https://git.openjdk.org/jfx/pull/2043