code: package wprover;
  
  import javax.swing.*;
  import javax.swing.tree.DefaultMutableTreeNode;
  import javax.swing.tree.TreeSelectionModel;
  
  /**
   * Created by IntelliJ IDEA.
   * User: yezheng
   * Date: 2006-5-21
   * Time: 22:25:06
   * To change this template use File | Settings | File Templates.
   */
  public class provePopTree extends JPanel {
      private DefaultMutableTreeNode top;
      private JTree tree;
  
      public provePopTree() {
          top = new DefaultMutableTreeNode("", true);
          tree = new JTree(top);
          tree.putClientProperty("JTree.lineStyle", "Horizontal");
          tree.getSelectionModel().setSelectionMode
                  (TreeSelectionModel.SINGLE_TREE_SELECTION);
      }
  }
  