Java sdk on ubuntu

Hi again.

I'm trying to run a java application so I can do my homework, but I keep getting exceptions. I'm not sure what's going on, since I know from using it on Windows that there is nothing wrong with the app and I'm pretty sure I have the sdk installed correctly. Does anyone know what might be going on? Here are the errors I get:

Exception in thread "main" java.lang.ExceptionInInitializerError
at java.lang.Class.initializeClass(libgcj.so.7)
at gui.action.NewAction$NewDialog.initMenu(NewAction.java:136)
at gui.action.NewAction$NewDialog.(NewAction.java:103)
at gui.action.NewAction.showNew(NewAction.java:70)
at JFLAP.main(JFLAP.java:96)
Caused by: java.lang.NullPointerException
at java.awt.Window.(libgcj.so.7)
at javax.swing.JWindow.(libgcj.so.7)
at gui.AboutBox.(AboutBox.java:50)
at gui.AboutBox.(AboutBox.java:87)
at gui.action.AboutAction.(AboutAction.java:54)
at java.lang.Class.initializeClass(libgcj.so.7)
...4 more


Thanks!

x-posted to linux