Expression Tree : JTree Node « Swing « Java Tutorial

Expression Tree
import java.util.Enumeration;
import java.util.Stack;

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

public class ExpressionTree extends JFrame {

  public ExpressionTree() {

    DefaultMutableTreeNode root = new DefaultMutableTreeNode("+");
    root.add(new DefaultMutableTreeNode(new Integer(3)));
    DefaultMutableTreeNode node = new DefaultMutableTreeNode("*");
    node.add(new DefaultMutableTreeNode(new Integer(4)));
    node.add(new DefaultMutableTreeNode(new Integer(5)));

    JTree tree = new JTree(root);

    Stack stack = new Stack(); 
    Enumeration e = root.postorderEnumeration();
    while (e.hasMoreElements()) { 
      DefaultMutableTreeNode node1 = (DefaultMutableTreeNode) (e.nextElement());
      Object obj = node1.getUserObject();
      if (obj instanceof Integer) {
      } else {
        String operator = (String) obj;
        Integer v1 = (Integer) stack.pop();
        Integer v2 = (Integer) stack.pop();

        if (operator.equals("+")) {
          stack.push(new Integer(v2.intValue() + v1.intValue()));
        } else {
          stack.push(new Integer(v2.intValue() * v1.intValue()));

  public static void main(String[] args) {
    ExpressionTree t = new ExpressionTree();

14.67.JTree Node
14.67.1.Get child count, depth, leaf count
14.67.2.Adding a Node to a JTree Component
14.67.3.Delete tree node
14.67.4.Removing a Node to a JTree Component
14.67.5.Expression TreeExpression Tree
14.67.6.Swing TreeSwing Tree
14.67.7.JTree node mouse click event
14.67.8.A JTree subclass that displays the tree of AWT or Swing component that make up a GUI
14.67.9.Tree with custom icon
14.67.10.CheckBox Tree node
14.67.11.Get path for all expanded or not expanded tree pathes
14.67.12.Converting All Nodes in a JTree Component to a TreePath Array
14.67.13.Expanding or Collapsing All Nodes in a JTree Component
14.67.14.JTree root cannot be removed with removeNodeFromParent(), use DefaultTreeModel.setRoot() to remove the root
14.67.15.Searching node in a JTree