Java JTree is tree path expanded

import java.awt.Container;
import java.awt.FlowLayout;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreePath;

public class Main {
   public static void main(String args[]) {
      final JFrame f = new JFrame("JTree Demo");
      f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      Container c = f.getContentPane();
      c.setLayout(new FlowLayout());
      DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
      DefaultMutableTreeNode c1 = new DefaultMutableTreeNode("A");
      DefaultMutableTreeNode c2 = new DefaultMutableTreeNode("B");
      DefaultMutableTreeNode c3 = new DefaultMutableTreeNode("C");
      root.add(c1);//ww  w  .jav  a2 s.c o  m
      root.add(c2);
      root.add(c3);

      c1.add(new DefaultMutableTreeNode("1"));
      c1.add(new DefaultMutableTreeNode("2"));

      c2.add(new DefaultMutableTreeNode("3"));
      c2.add(new DefaultMutableTreeNode("4"));

      c3.add(new DefaultMutableTreeNode("5"));
      DefaultMutableTreeNode n6 = new DefaultMutableTreeNode("6");

      c3.add(n6);

      JTree t = new JTree(root);

      System.out.println(isNodeExpanded(t, root));

      c.add(new JScrollPane(t));
      f.pack();
      f.setVisible(true);
   }
   public static boolean isNodeExpanded(JTree tree,
         DefaultMutableTreeNode node) {
     if (tree == null) {
         throw new NullPointerException("tree == null");
     }
     if (node == null) {
         throw new NullPointerException("node == null");
     }
     return tree.isExpanded(new TreePath(node.getPath()));
 }
}