return null; }
    private DefaultMutableTreeNode findNode(Object userObject) {      Enumeration nodes = root.depthFirstEnumeration();      while (nodes.hasMoreElements()) {	DefaultMutableTreeNode node = 	  (DefaultMutableTreeNode)nodes.nextElement();	if (node.isLeaf() &&	    node.getUserObject().equals(userObject))	  return node;      }      return null;    }