Utilising more modern Java, simplifying code and formatting code and comments

[ham1]

Description

Three commits covering three types of change:

• Formatting and comment tidy up
• Use modern Java, streams, computeIfAbsent etc.
• Simplify code and reduce nesting

Feel free to take only some, I did this while trying to better understand the code.

Motivation and Context

Improve readability etc.

How Has This Been Tested?

Ant test, no functional changes.

Screenshots (if appropriate):

Types of changes

• Code improvement

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly.

[codecov-io]

Codecov Report

Merging #327 into trunk will increase coverage by 0.03%.
The diff coverage is 20.32%.

@@             Coverage Diff              @@
##              trunk     #327      +/-   ##
============================================
+ Coverage     57.83%   57.87%   +0.03%     
+ Complexity     9937     9935       -2     
============================================
  Files          1141     1141              
  Lines         73217    73166      -51     
  Branches       7305     7277      -28     
============================================
- Hits          42346    42342       -4     
+ Misses        28405    28356      -49     
- Partials       2466     2468       +2

Impacted Files	Coverage Δ	Complexity Δ
...ore/org/apache/jmeter/gui/action/AboutCommand.java	0% <ø> (ø)	0 <0> (ø)	⬇️
src/core/org/apache/jmeter/gui/GUIFactory.java	0% <ø> (ø)	0 <0> (ø)	⬇️
src/core/org/apache/jmeter/gui/action/Move.java	0% <ø> (ø)	0 <0> (ø)	⬇️
...core/org/apache/jmeter/gui/SimpleCompoundEdit.java	33.33% <ø> (ø)	1 <0> (ø)	⬇️
...core/org/apache/jmeter/gui/SavePropertyDialog.java	4% <ø> (ø)	1 <0> (ø)	⬇️
...core/org/apache/jmeter/gui/GlobalUndoableEdit.java	0% <ø> (ø)	0 <0> (ø)	⬇️
src/core/org/apache/jmeter/gui/CommentPanel.java	100% <ø> (ø)	5 <0> (ø)	⬇️
...rc/core/org/apache/jmeter/gui/UndoHistoryItem.java	57.14% <ø> (ø)	2 <0> (ø)	⬇️
...org/apache/jmeter/gui/action/SearchTreeDialog.java	1.86% <0%> (+0.02%)	1 <0> (ø)	⬇️
...e/org/apache/jmeter/gui/action/AbstractAction.java	21.27% <0%> (+0.86%)	2 <0> (ø)	⬇️
... and 23 more

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