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When I'm trying to run a Java GUI application from the command line, I get:

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,"

I keep getting this error whenever I try to run code with java.swing GUI components.

$DISPLAY is set to :0 and java --version gives me openjdk 19.0.1.

edit: I tried to run java Main with either wayland or xorg but I get the same error.

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  • How do you start the binary? Is there some scripting or user-switching involved? Commented Jan 25, 2023 at 10:21
  • Sorry in advance, Im a linux beginner. To run the applicaton I compile with "javac" and run with "java". I hope this is what you meant. Commented Jan 25, 2023 at 10:31
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    So must importantly: Is an X-server installed? What kind of Linux do you use? You probably have only wayland? Commented Jan 25, 2023 at 10:53
  • Welcome to the site. When asked for clarifications, please don't respond in comments, but edit your post to include the requested information. Reading through the comments is rather painful, and comments are subject to removal without notice by moderators. Commented Jan 25, 2023 at 12:27
  • I am also experiencing this as well when using Worldographer that I packaged in a Flatpak. When I switch to GNOME (Xorg) it works, but GNOME (wayland) I get this error above. github.com/FilBot3/com.inkwellideas.Worldographer Commented Jun 17, 2023 at 16:39

2 Answers 2

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Rolling back to openjdk-17 worked for me, you might be able to get away with a more recent version. Openjdk 19 starts in headless by default, so therefore no display.

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I had a similar issue with OpenJDK 21. It was resolved by installing the java-21-openjdk-devel package, when previously just the java-21-openjdk package was installed.

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  • Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center. Commented Mar 27 at 5:10

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