Java: Improve class name handling #23
Description
Current state:
- The widget requires the class to be named 'Main'.
- This is not specified anywhere, and the error message does not provide the correct name.
Solutions:
- Auto-detect the class name from the code and name the file accordingly.
- Support Java 21 unnamed classes if possible in TeaVM.
- Provide a template containing the class name and main method when inserting the widget.
- Improve the error message.