Unable to run Java GUI programs with Ubuntu

Question

I am learning GUI in Java, and for that I have created a demo program:

import java.awt.*;

public class FrameDemo extends Frame {

    public FrameDemo(){
           


        

Answer 1

In my case

-Djava.awt.headless=true

was set (indirectly by a Maven configuration). I had to actively use

-Djava.awt.headless=false

to override this.