FAQ#14

How do I run a Java program?

Added by Christoph Kappel over 7 years ago. Updated by Christoph Kappel over 6 years ago.

Category: Programs Difficulty: Difficulty7
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Answer

Java expects a certain behaviour (reparenting of client windows) of a window manager which is not part of any standard, therefore some Java programs just show a white canvas.

If this happens just try to start your program like this:

1 AWT_TOOLKIT=MToolkit program

This changes the default tookit of Java to MToolkit, which is known to work with non-reparenting windows managers like subtle. Depending on your OpenJDK version and your architecture this may either lead to a segmentation fault or your OpenJDK just has no support for MToolkit. In this case check if your distribution has applied a patch for this issue which allows something like this to change the default behaviour:

1 _JAVA_AWT_WM_NONREPARENTING=1 program

In case both doesn't work there is a third option: Java seems to use an internally hardcoded list of window managers that are non-reparenting, the suckless guys made a tool (wmname) to change the name of the wm.

Since r2520 subtle can do that for you, just enable the :wmname option.

Generally this problem is really long lasting, see here:

http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6511454
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=508650

Note: Many problems only affect the JRE and can be avoided by using the OpenJDK.

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