Add node to a specific node in JTree

Question

I use the following TreePanel class to add node to the tree. My question is how to add a new node under
a specific node which has been created before. In other words, how to get the path and identify the node.
For e.g., I first loaded some raw data files and created the "raw data" node, later I need to load another file
and create a new node under the "raw data" node. Each node is created by using user object. Any help is greatly appreicated.
import java.awt.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.tree.*;
public class TreePanel extends JPanel {
  protected DefaultMutableTreeNode rootNode;
  protected DefaultTreeModel treeModel;
  protected JTree tree;
  public TreePanel() {
    super(new GridLayout(1,0));
    rootNode = new DefaultMutableTreeNode("Experiment");
    treeModel = new DefaultTreeModel(rootNode);
    tree = new JTree(treeModel);
    tree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
    tree.setShowsRootHandles(true);
    JScrollPane scrollPane = new JScrollPane(tree);
    add(scrollPane);
  public JTree getTree(){
    return tree;
  /* Add child to the currently selected node. */
  public DefaultMutableTreeNode addObject(Object child){
    DefaultMutableTreeNode parentNode = null;
    TreePath parentPath = tree.getSelectionPath();
    if(parentPath == null){
      parentNode = rootNode;
    else{
      parentNode = (DefaultMutableTreeNode)(parentPath.getLastPathComponent());
    return addObject(parentNode, child, true);
  /* Add child */
  public DefaultMutableTreeNode addObject(DefaultMutableTreeNode parent, Object child){
    return addObject(parent, child, false);
  /* Add child */
  public DefaultMutableTreeNode addObject(DefaultMutableTreeNode parent, Object child, boolean shouldBeVisible){
    DefaultMutableTreeNode childNode = new DefaultMutableTreeNode(child);
    if(parent == null){parent = rootNode;}
    treeModel.insertNodeInto(childNode, parent, parent.getChildCount());
    if(shouldBeVisible){
      tree.scrollPathToVisible(new TreePath(childNode.getPath()));
    return childNode;
  /* Add child */
  public DefaultMutableTreeNode addObject(DefaultMutableTreeNode parent, DefaultMutableTreeNode child){
   if(parent == null){parent = rootNode;}
   treeModel.insertNodeInto(child, parent, parent.getChildCount());
   return child;
}Thanks in advance!

Answer 1

public static DefaultMutableTreeNode findNode(DefaultMutableTreeNode from, Object userObject) {
          if (userObject == null && from.getUserObject() == null) {
               return from;
          } else if (userObject.equals(from.getUserObject())) {
               return from;
          DefaultMutableTreeNode node = null;
          for (int i = 0; i < from.getChildCount(); i ++) {
               node = (DefaultMutableTreeNode) from.getChildAt(i);
               if (userObject == null) {
                    if (userObject == node.getUserObject()) {
                         break;
               } else {
                    if (userObject.equals(node.getUserObject())) {
                         break;
               node = null;
          if (node != null) {
               return node;
          //Node not found
          //dig deeper
          for (int i = 0; i < from.getChildCount(); i ++) {
               node = (DefaultMutableTreeNode) from.getChildAt(i);
               if (!node.isLeaf()) {
                    node = findNode(node, userObject);
                    if (node != null) {
                         return node;
          //Not found
          return null;
     }