tjger - the java game & entertainment rt Code (Desktop)

* removed code smells
* corrected indentation
* corrected java doc

StringBuilder.isEmpty is only available in Java 15+.

getFieldSize() is now provided from the base class.

getFieldSize() is now provided from the base class.

Usage of configurable game panel.

Game panel which can be configured via the tjger xml file.

getPartsAtMousePosition: Usage of streams.

Method to get the position where a part was painted.
Set compliance level to Java 9.

Store the part itself instead of only the part id, because the part id is not independent from the current selected visualization.

When a part is painted, some information is now stored in the game panel. With this information is it possible to get the part id's of the parts which were painted at the current mouse position.
This can be used to find out which part was clicked and therefore which action has to be performed.