import java.io.File ;
import java.io.FileInputStream ;
import java.io.FileOutputStream ;
import java.io.ObjectInputStream ;
import java.io.ObjectOutputStream ;
import java.io.Serializable ;
import java.util.Hashtable ;

import java.awt.BorderLayout ;
import java.awt.Color ;
import java.awt.event.ActionEvent ;
import java.awt.event.ActionListener ;
import java.awt.event.WindowAdapter ;
import java.awt.event.WindowEvent ;
import javax.swing.JButton ;
import javax.swing.JFrame ;
import javax.swing.JLabel ;
import javax.swing.JOptionPane ;
import javax.swing.JPanel ;
import javax.swing.JScrollPane ;
import javax.swing.JTree ;
import javax.swing.event.TreeSelectionEvent ;
import javax.swing.event.TreeSelectionListener ;
import javax.swing.tree.DefaultMutableTreeNode ;

class Tree1
    extends JFrame
    implements Serializable
{
  JTree tree ;
  Hashtable h ;
  JPanel panel ;
  JScrollPane scroll ;
  JButton btnOpen , btnSave ;
  JLabel lblStatus ;
  int count = 0 ; //child tree node counts;
  String[] s1 = {"child" + count} ;
  static Tree1 treeApp ;

  TreeSelectionListener listener = new TreeSelectionListener()
  {
    public void valueChanged ( TreeSelectionEvent e )
    {
      DefaultMutableTreeNode node = ( DefaultMutableTreeNode ) tree.getLastSelectedPathComponent() ;
      if ( node == null )
        return ;
      Object nodeInfo = node.getUserObject() ;
      lblStatus.setForeground( Color.red ) ;
      lblStatus.setText( nodeInfo.toString() + "Selected" ) ;
      validate() ; //re-layout & repaint
      repaint() ;
    }
  };

  public Tree1 ()
  {
//initialize the tree which constructed with hashtable
    h = new Hashtable() ;
    h.put( "root" , s1 ) ;
    tree = new JTree() ;
    tree.setEditable( true ) ;
    panel = new JPanel() ;
    scroll = new JScrollPane( tree ) ;
    btnOpen = new JButton( "open" ) ;
    btnSave = new JButton( "save" ) ;
    lblStatus = new JLabel() ;

    tree.addTreeSelectionListener( listener);
    btnOpen.addActionListener( new ActionListener()
    {
      public void actionPerformed ( ActionEvent e )
      {
        scroll.remove( tree ) ;
        ObjectInputStream is = null ;
        try {
          is = new ObjectInputStream( new FileInputStream( new File( "os.txt" ) ) ) ;
          JTree treeB = ( JTree ) is.readObject() ;
          scroll.removeAll();
          scroll.add( treeB ) ;
          treeB.setRootVisible( true ) ;
          treeB.addTreeSelectionListener(listener);
          is.close() ;
          validate() ;
          repaint() ;
          JOptionPane.showConfirmDialog( null , "opened the previous' tree" , "open" , JOptionPane.PLAIN_MESSAGE ) ;
        }
        catch ( Exception et ) {
          et.printStackTrace();
        }
      }
    } ) ;
    btnSave.addActionListener( new ActionListener()
    {
      public void actionPerformed ( ActionEvent event )
      {
        ObjectOutputStream os = null ;
        try {
          os = new ObjectOutputStream( new FileOutputStream( new File( "os.txt" ) ) ) ;
          os.writeObject( tree ) ;
          JOptionPane.showConfirmDialog( null , "saved this tree" , "save" , JOptionPane.PLAIN_MESSAGE ) ;
        }
        catch ( Exception e ) {
          System.out.println( "error write object" ) ;
        }
        finally {
          try {
            os.close() ;
          }
          catch ( Exception e ) {
            System.out.println( "error on close" ) ;
          }
        }
      }
    } ) ;
    setContentPane( panel ) ;
    panel.setLayout( new BorderLayout() ) ;
    panel.add( scroll , BorderLayout.CENTER ) ;
    JPanel btnPanel = new JPanel() ;
    btnPanel.add( btnOpen ) ;
    btnPanel.add( btnSave ) ;
    panel.add( btnPanel , BorderLayout.NORTH ) ;
    panel.add( lblStatus , BorderLayout.SOUTH ) ;
    setSize( 300 , 400 ) ;
    show() ;
    this.addWindowListener( new WindowAdapter()
    {
      public void windowClosing ( WindowEvent e )
      {
        System.exit( 0 ) ;
      }
    } ) ;
  }

  public static void main ( String[] args )
  {
    treeApp = new Tree1() ;
  }
}