FULL PRODUCT VERSION :
JDK 1.5.0_10

ADDITIONAL OS VERSION INFORMATION :
WinXP 5.1.2600, Solaris 5.10

A DESCRIPTION OF THE PROBLEM :
When setting a JFileChooser to an instance of a FileView subclass that restricts traversing outside of a specified directory tree, and I use the pulldown list to select a directory outside of the tree, and then do it again to select a directory inside the tree, a NullPointerException is thrown from inside JFileChooser.

A toy program and stack trace are included below wbjch demonstrate this (with the path changed for Solaris).

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Execute the toy program below on Windows (make sure C:\temp exists) - in the JFileChooser, use the pulldown list to choose the C:\ drive or some other directory; then, use the pulldown again to choose C:\temp. Verify the NullPointerException at the console.


ERROR MESSAGES/STACK TRACES THAT OCCUR :
Exception occurred during event dispatching:
java.lang.NullPointerException
at javax.swing.plaf.metal.MetalFileChooserUI$DirectoryComboBoxAction.actionPerformed(Unknown Source)
at javax.swing.JComboBox.fireActionEvent(Unknown Source)
at javax.swing.JComboBox.setSelectedItem(Unknown Source)
at javax.swing.JComboBox.setSelectedIndex(Unknown Source)
at javax.swing.plaf.basic.BasicComboPopup$Handler.mouseReleased(Unknown Source)
at java.awt.AWTEventMulticaster.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at javax.swing.plaf.basic.BasicComboPopup$1.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.Dialog$1.run(Unknown Source)
at java.awt.Dialog$2.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.awt.Dialog.show(Unknown Source)
at javax.swing.JFileChooser.showDialog(Unknown Source)
at javax.swing.JFileChooser.showOpenDialog(Unknown Source)
at FileChooserTest$1.actionPerformed(FileChooserTest.java:28)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.BorderLayout;
import java.awt.event.*;
import java.io.File;
import javax.swing.*;
import javax.swing.filechooser.FileView;
 
public class FileChooserTest extends JFrame {
 
   private JButton button = null;
 
   public static void main(String [] args) {
      FileChooserTest application = new FileChooserTest();
      application.setVisible(true);
   }
 
   public FileChooserTest() {
      this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      this.setSize(200, 200);
      
      button = new JButton("Show Chooser");
      button.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            JFileChooser openChooser = new JFileChooser();
            String path = "C:" + File.separator + "temp";
            openChooser.setCurrentDirectory(new File(path));
            openChooser.setFileView(new MyFileView(path));
            
            int result = openChooser.showOpenDialog(FileChooserTest.this);
            
            if (result == JFileChooser.APPROVE_OPTION)
               System.out.println(openChooser.getSelectedFile().getAbsolutePath());
            else
               System.out.println("cancelled");
         }
      });
      
      getContentPane().setLayout(new BorderLayout());
      getContentPane().add(button, BorderLayout.CENTER);
   }
}
 
class MyFileView extends FileView {
   private String basePath;
   
   public MyFileView(String path) {
      basePath = path;
   }
   
   public Boolean isTraversable(File f) {
      if ((f != null) && (f.isDirectory()))
         return f.getAbsolutePath().startsWith(basePath);
      else
         return false;
   }
}
---------- END SOURCE ----------