[PROPOSAL] Clean up code

[JohannesDaniel]

As of now, there are many

• Non-final class variables that could be final
• Usages if unmodifiableList instead of List.of
• Unused imports
• Deprecated API usage
• Commented out code
• Code style issues

... and many many more (running code inspection reveals a massive amount of issues).

Furthermore, there are many inner classes, including inner classes within inner classes, which makes the code difficult to read.

The code should be cleaned up, probably not all at once, but rather stepwise.

[sstults]

I agree with the step-wise approach. Maybe start with ones that have no chance of affecting the compiled code (commented out code, unused imports) and then take each next class of change in turn.