Can not run application on Windows

Question

What's wrong with my windows system.
I compile the java files in linux and put the class file to the windows system. But the class file can't run correctly. The error is following:
Exception in thread "main" java.lang.NullPointerException
at java.awt.Window.init(Unknown Source)
at java.awt.Window.<init>(Unknown Source)
at java.awt.Frame.<init>(Unknown Source)
at javax.swing.JFrame.<init>(Unknown Source)
at FrameTest.<init>(FrameTest.java:10)
at FrameTest.main(FrameTest.java:17)
the FrameTest.java is following:
import java.util.*;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class FrameTest extends JFrame
public FrameTest()
super( "test" );
add( new JPanel() );
public static void main( String[] argv )
JFrame f = new FrameTest();
f.setSize( 400, 400 );
f.setVisible( true );
the version of JDK is 1.6.0b2 on linux
the version of JRE is 1.6.0b2 on windows
But if I compile the java file in windows, then it run ok on windows and linux.
Also the class file can run onther windows system.
I want to know what wrong with my windows system and how to find the solution.
thanks

Answer 1

Well I can see a problem, though I don't know
why you should get the symptoms you are getting. You
shouldn't be adding components directly to a JFrame,
you should add them to the content pane
(getContentPane().add(..) )That was changed in JDK 1.5. It's now ok to add directly to the component.
Kaj