Insert tree node to JTree model in Java

import java.awt.BorderLayout;
/*from   w  ww. j a va2 s  .co  m*/
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.MutableTreeNode;
import javax.swing.tree.TreePath;

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

    DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
    DefaultMutableTreeNode mercury = new DefaultMutableTreeNode("Mercury");
    root.add(mercury);
    DefaultMutableTreeNode venus = new DefaultMutableTreeNode("b");
    root.add(venus);
    DefaultMutableTreeNode mars = new DefaultMutableTreeNode("java2s.com");
    root.add(mars);
    JTree tree = new JTree(root);

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


    DefaultTreeModel model = (DefaultTreeModel) tree.getModel();
    tree.setSelectionRow(2);
    TreePath path = tree.getSelectionPath();
    MutableTreeNode node = (MutableTreeNode) path.getLastPathComponent();

    MutableTreeNode newNode = new DefaultMutableTreeNode("green");

    model.insertNodeInto(newNode, node, node.getChildCount());
  }
}