intallation problem in argouml

sir,

  while installing argouml i am getting an error
which i cannot solve, can u help me in sloving this error
i have downloaded ArgoUML-0.22.tar.gz and ArgoUML-0.24-src.tar.gz also but
iam unable to install in my linux system.
can i know why this error is comming.

the error which iam geting is


[integra@1FTSD9 ArgoUML-0.22.tar.gz_FILES]$ java -jar argouml.jar
Exception in thread "main" java.lang.NullPointerException
   at java.lang.Object.getClass (libgcj.so.7)
   at org.argouml.ui.DisplayTextTree.setModel (DisplayTextTree.java:316)
   at javax.swing.plaf.basic.BasicTreeUI.setModel (libgcj.so.7)
   at javax.swing.plaf.basic.BasicTreeUI.installUI (libgcj.so.7)
   at javax.swing.plaf.metal.MetalTreeUI.installUI (libgcj.so.7)
   at javax.swing.JComponent.setUI (libgcj.so.7)
   at javax.swing.JTree.setUI (libgcj.so.7)
   at javax.swing.JTree.updateUI (libgcj.so.7)
   at javax.swing.JTree.<init> (libgcj.so.7)
   at javax.swing.JTree.<init> (libgcj.so.7)
   at org.argouml.ui.DisplayTextTree.<init> (DisplayTextTree.java:91)
   at org.argouml.ui.explorer.ExplorerTree.<init> (ExplorerTree.java:91)
   at org.argouml.ui.explorer.DnDExplorerTree.<init>
(DnDExplorerTree.java:119)
   at org.argouml.ui.NavigatorPane.<init> (NavigatorPane.java:75)
   at org.argouml.ui.ProjectBrowser.createPanels (ProjectBrowser.java:342)
   at org.argouml.ui.ProjectBrowser.<init> (ProjectBrowser.java:248)
   at org.argouml.ui.ProjectBrowser.makeInstance (ProjectBrowser.java:315)
   at org.argouml.application.Main.initializeGUI (Main.java:646)
   at org.argouml.application.Main.main (Main.java:230)


please mail me the problem why the process is aborting and also the
aolution for that problem

please it is an urgent for me


Thanks & Regards

H.Santhosha