When setAlwaysOnTop is called on FileDialog or PrintDialog, it throws NPE from native code:

Exception in thread "main" java.lang.NullPointerException: null pData
         at sun.awt.windows.WWindowPeer.setAlwaysOnTop(Native Method)
         at java.awt.Window.addNotify(Window.java:471)
         at java.awt.Dialog.addNotify(Dialog.java:376)
         at java.awt.FileDialog.addNotify(FileDialog.java:266)
         at java.awt.Dialog.conditionalShow(Dialog.java:441)
         at java.awt.Dialog.show(Dialog.java:506)
         at java.awt.Component.show(Component.java:1303)
         at java.awt.Component.setVisible(Component.java:1256)
         at Crash.main(Crash.java:16)

This happens because these components (their peers) don't have a window associate with them all the time. The standard way to deal with this is to override the methods which may be called on these components and require such a window, to none.

setAlwaysOnTop is now called from addNotify, so this affects the behavior of all these dialogs even if they were not explicitly been made always-on-top.

Test to reproduce:

import java.awt.*;
public class Crash
{
     public static void main(String[] args)
     {
         Frame f = new Frame("F");
         f.setBounds(100, 100, 200, 100);
         f.setVisible(true);

        FileDialog fd = new FileDialog(f);
        fd.setVisible(true);
     }
}

###@###.### 2005-1-20 14:21:05 GMT