Java Swing TreeModelListener handle tree model event

import java.awt.BorderLayout;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.event.TreeModelEvent;
import javax.swing.event.TreeModelListener;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;

class MyTreeModelListener implements TreeModelListener {
   public void treeNodesChanged(TreeModelEvent e) {
      DefaultMutableTreeNode node;
      node = (DefaultMutableTreeNode) (e.getTreePath().getLastPathComponent());
      try {/*from  ww w.  j  ava2 s  . c om*/
         int index = e.getChildIndices()[0];
         node = (DefaultMutableTreeNode) (node.getChildAt(index));
      } catch (NullPointerException exc) {
      }
      System.out.println("New value: " + node.getUserObject());
   }

   public void treeNodesInserted(TreeModelEvent e) {
      System.out.println(e);
   }

   public void treeNodesRemoved(TreeModelEvent e) {
      System.out.println(e);
   }

   public void treeStructureChanged(TreeModelEvent e) {
      System.out.println(e);
   }
}

public class Main {
   public static void main(String args[]) {
      JFrame frame = new JFrame();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

      DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
      JTree tree = new JTree(root);

      DefaultTreeModel treeModel = new DefaultTreeModel(root);
      treeModel.addTreeModelListener(new MyTreeModelListener());

      treeModel.insertNodeInto(new DefaultMutableTreeNode("A"), root, 0);

      root.add(new DefaultMutableTreeNode("B"));
      root.add(new DefaultMutableTreeNode("C"));

      JScrollPane scrollPane = new JScrollPane(tree);
      frame.add(scrollPane, BorderLayout.CENTER);
      frame.setSize(300, 150);
      frame.setVisible(true);

   }
}