Ubuntu Libgdx problem - No X11 DISPLAY variable was set

Question

My problem is with X11 variable - when Im trying to launch gdx-setup.jar i get output:

Exception in thread "main" java.awt.HeadlessException: 
No X11 DISPLAY variable was set,
or no headful library support was found,
but this program performed an operation which requires it,

    at java.desktop/java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:166)
    at java.desktop/java.awt.Window.<init>(Window.java:553)
    at java.desktop/java.awt.Frame.<init>(Frame.java:428)
    at java.desktop/java.awt.Frame.<init>(Frame.java:393)
    at java.desktop/javax.swing.JFrame.<init>(JFrame.java:180)
    at com.badlogic.gdx.setup.GdxSetupUI.<init>(GdxSetupUI.java:101)
    at com.badlogic.gdx.setup.GdxSetup.main(GdxSetup.java:620)

Im running ubuntu on my local laptop (NO SSH).
System details

I've tried commands:

sudo apt-get update --fix-missing sudo apt-get update sudo apt-get clean sudo apt-get autoremove sudo dpkg reconfigure -a sudo apt install -f

It didnt help at all...

When Im running AWT from intellij I can see GUI normally and there's no exception.

Ive followed there instructions while installing libgdx: https://tutorialforlinux.com/2022/11/14/step-by-step-libgdx-ubuntu-22-04-installation-guide/2/

echo $DISPLAY output:0

Installed: xorg-x11

Double clicking on jar causes with no response... Ive marked jar as executable

Answer 1

You can specify one of many installed java versions when running from intellij. When running from the command line its just a single one.I think your default java probably -actually truly is- headless. Follow this guide here to change your default command line java. I mean the error is specifically that if fails the headless check. Follow here to switch the default cmd line java version.

https://computingforgeeks.com/how-to-set-default-java-version-on-ubuntu-debian/

Its not unusual to have headless because thats all server side stuff needs.