package abc;
 
import java.io.*;
 
public class Data {
 
    private String name;
    private String fullName;
 
    public Data (File f)
    {
        name = f.getName();
        fullName = f.getAbsolutePath();
    }
 
    public String toString ()
    {
        return name;
    }
 
    private String getFullName ()
    {
        return fullName;
    }
}

   import javax.swing.*;
   import javax.swing.tree.*;
   import java.io.*;
 
    private void display (DefaultMutableTreeNode branch, File dir)
    {
        if (dir.isDirectory())
        {
            File [] files = dir.listFiles();
            if (files != null)
               for (File file : files)
               {
                   DefaultMutableTreeNode node = 
                      new DefaultMutableTreeNode (new Data (file));
                   branch.add (node);
                   if (file.isDirectory())
                       display (node, file);
               }
        }
    }
 
    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        File dir = new File ("..");        
        DefaultMutableTreeNode branch = 
                new DefaultMutableTreeNode (new Data (dir));
        display (branch, dir);
        DefaultTreeModel model = new DefaultTreeModel (branch);
        jTree1.setModel (model);
    }                                        
 
    private void jTree1ValueChanged(javax.swing.event.TreeSelectionEvent evt) {                                    
        TreePath path = evt.getPath();
        Object comp = path.getLastPathComponent();
        if (comp instanceof DefaultMutableTreeNode)
        {
            DefaultMutableTreeNode node = (DefaultMutableTreeNode) comp;
            Object obj = node.getUserObject();
            if (obj instanceof Data)
            {
                Data data = (Data) obj;
                System.out.println ("click " + data.getFullName ());
            }
        }
    }                                   
    private void jTree1ValueChanged(javax.swing.event.TreeSelectionEvent evt) {                                    
        // TODO add your handling code here:
        TreePath path = evt.getPath();
        Object comp = path.getLastPathComponent();
        if (comp instanceof DefaultMutableTreeNode)
        {
            DefaultMutableTreeNode node = (DefaultMutableTreeNode) comp;
            Object obj = node.getUserObject();
            if (obj instanceof Data)
            {
                Data data = (Data) obj;
                String fileName = data.getFullName ();
 
                try 
                {
                    FileReader r = new FileReader (fileName);
                    BufferedReader b = new BufferedReader (r);
 
                    jTextArea1.setText("");
                    int cnt = 1;
                    while (b.ready() && cnt <= 100)
                    {
                       jTextArea1.append (b.readLine() + "\n");
                       cnt ++;
                    }
                } 
                catch (Exception ex) 
                {
                }
            }
        }
    }