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

Check what your environment variable DISPLAY's value is. Try running a simple X application from the command line. If it works, check DISPLAY's value for the right value.

You can experiment with different values of and environment variable on a per invocation basis by doing the following on the command line:

DISPLAY=:0.0 <your-java-executable-here>

How are you calling your program?

Answer 2

Check your X Window environment variables using the "env" command.

Answer 3

I stopped getting this exception when I installed default-jdk using apt. I'm running Ubuntu 14.04 (Trusty Tahr), and the problem appears to have been the result of having a "headless" Java installed. All I did was:

sudo apt-get install default-jdk

Answer 4

Ubuntu has the option to install a headless Java -- this means without graphics libraries. This wasn't always the case, but I encountered this while trying to run a Java text editor on 10.10 the other day. Run the following command to install a JDK that has these libraries:

sudo apt-get install openjdk-6-jdk

EDIT: Actually, looking at my config, you might need the JRE. If that's the case, run:

sudo apt-get install openjdk-6-jre

Answer 5

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.

Answer 6

I would check with another Java implementation/vendor. Preferrably Oracle/Sun Java: http://www.java.com/en/ . The open-source implementations unfortunately differ in weird ways.