import javax.swing.*;
import javax.swing.tree.*;
import java.io.*;
 
    private void displayDirectory (DefaultMutableTreeNode target, File dir)
    {
       File [] list = dir.listFiles();
       for (File item : list)
       {
          DefaultMutableTreeNode node = new DefaultMutableTreeNode (item.getName());
          target.add (node);
 
          if (item.isDirectory())
              displayDirectory (node, item);
       }
    }
 
    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
       String dir_name = "..";
       try 
       {
            File d0 = new File (dir_name);
            dir_name = d0.getCanonicalPath();
       } 
       catch (IOException ex) { }
       File d = new File (dir_name);
       DefaultMutableTreeNode root = new DefaultMutableTreeNode (d.getName());
       displayDirectory (root, d);
       DefaultTreeModel model = new DefaultTreeModel (root);
       jTree1.setModel (model);
   }