A bug in the JTree(Missing some nodes)

Question

I have an application which implement a JTree & DnDTree. The left hand side is the original JTee, the right hand size is DnDTree which allows user to Drag and Drop some node from left JTree. The bug is: when I grag some node to right DnDTree, once I then click the left JTree, some nodes will be missing. I try my best for more than one week, but still couldn't fix it, could anybody take time to fina a way to fix it? The piece of code of creating JTree is as follow:
/*public void createTestTree()
DefaultMutableTreeNode rootRight = new DefaultMutableTreeNode("Root");
DefaultMutableTreeNode root = createTreeModel();
treeLeft = new DnDTree(root, true); //JTree(root, true);
treeLeft.putClientProperty("JTree.lineStyle", "Angled");
treeLeft.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
treeLeft.addTreeExpansionListener(new TreeExpansionListener(){
public void treeCollapsed(TreeExpansionEvent e) {
public void treeExpanded(TreeExpansionEvent e) {
UpdateStatus updateThread;
TreePath path = e.getPath();
FileNode node = (FileNode)
path.getLastPathComponent();
if( ! node.isExplored()) {
DefaultTreeModel model = (DefaultTreeModel)treeLeft.getModel();
UpdateStatus us = new UpdateStatus();
us.start();
node.explore();
model.nodeStructureChanged(node);
class UpdateStatus extends Thread {
public void run() {
try { Thread.currentThread().sleep(450); }
catch(InterruptedException e) { }
SwingUtilities.invokeLater(new Runnable() {
public void run() {
treeRight = new DnDTree(rootRight, true); treeRight.putClientProperty("JTree.lineStyle", "Angled");
treeRight.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
treeRight.addTreeExpansionListener(new TreeExpansionListener(){
public void treeCollapsed(TreeExpansionEvent e) {
public void treeExpanded(TreeExpansionEvent e) {
UpdateStatus updateThread;
TreePath path = e.getPath();
FileNode node = (FileNode)
                         path.getLastPathComponent();               
if( ! node.isExplored()) {
DefaultTreeModel model = (DefaultTreeModel)treeRight.getModel();
UpdateStatus us = new UpdateStatus();
us.start();
node.explore();
model.nodeStructureChanged(node);
class UpdateStatus extends Thread {
public void run() {
try { Thread.currentThread().sleep(450); }
catch(InterruptedException e) { }
SwingUtilities.invokeLater(new Runnable() {
public void run() {
My FileNode class is:
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.tree.*;
import java.awt.*;
import java.awt.event.*;
import java.io.File;
import java.util.EventObject;
public class GoodFileTree extends JPanel {
     public GoodFileTree() {
          final JTree tree = new JTree(createTreeModel());
          JScrollPane scrollPane = new JScrollPane(tree);
          this.add(scrollPane, BorderLayout.WEST);
          //getContentPane().add(scrollPane, BorderLayout.CENTER);
          this.add(GJApp.getStatusArea(),BorderLayout.SOUTH);
          //getContentPane().add(GJApp.getStatusArea(),BorderLayout.SOUTH);
          tree.addTreeExpansionListener(new TreeExpansionListener(){
               public void treeCollapsed(TreeExpansionEvent e) {
               public void treeExpanded(TreeExpansionEvent e) {
                    UpdateStatus updateThread;
                    TreePath path = e.getPath();
                    FileNode node = (FileNode)
                                        path.getLastPathComponent();
                    if( ! node.isExplored()) {
                         DefaultTreeModel model = (DefaultTreeModel)tree.getModel();
                         GJApp.updateStatus("exploring ...");
                         UpdateStatus us = new UpdateStatus();
                         us.start();
                         node.explore();
                         model.nodeStructureChanged(node);
               class UpdateStatus extends Thread {
                    public void run() {
                         try { Thread.currentThread().sleep(450); }
                         catch(InterruptedException e) { }
                         SwingUtilities.invokeLater(new Runnable() {
                              public void run() {
                                   GJApp.updateStatus(" ");
     private DefaultMutableTreeNode createTreeModel() {
          /*File root = new File("E:/");
          FileNode rootNode = new FileNode(root);
          rootNode.explore();
          return new DefaultTreeModel(rootNode);*/
          DefaultMutableTreeNode top = new DefaultMutableTreeNode("Root");
          File[] fArr = File.listRoots();
          File fDrive;
          FileNode driveNode;
          for(int i=0; i<fArr.length; ++i)
               fDrive = fArr;
               driveNode = new FileNode(fDrive);
               top.add(driveNode);
          return top;
     /*public static void main(String args[])
          try
               UIManager.setLookAndFeel(
               UIManager.getSystemLookAndFeelClassName()
               //UIManager.getCrossPlatformLookAndFeelClassName()
          catch (Exception e)
          GJApp.launch(new GoodFileTree(),"JTree File Explorer",
                                        300,300,450,400);
class FileNode extends DefaultMutableTreeNode {
     private boolean explored = false;
     public FileNode(File file)      {
          setUserObject(file);
     public boolean getAllowsChildren() { return isDirectory(); }
     public boolean isLeaf()      { return !isDirectory(); }
     public File getFile()          { return (File)getUserObject(); }
     public boolean isExplored() { return explored; }
     public boolean isDirectory() {
          File file = getFile();
          return file.isDirectory();
     public String toString() {
          File file = (File)getUserObject();
          String filename = file.toString();
          int index = filename.lastIndexOf(File.separator);
          return (index != -1 && index != filename.length()-1) ?
                                             filename.substring(index+1) :
                                             filename;
     public void explore() {
          if(!isDirectory())
               return;
          if(!isExplored()) {
               File file = getFile();
               File[] children = file.listFiles();
               for(int i=0; i < children.length; ++i)
                    add(new FileNode(children[i]));
               explored = true;
class GJApp extends WindowAdapter {
     static private JPanel statusArea = new JPanel();
     static private JLabel status = new JLabel(" ");
     public static void launch(final JFrame f, String title,
                                   final int x, final int y,
                                   final int w, int h) {
          f.setTitle(title);
          f.setBounds(x,y,w,h);
          f.setVisible(true);
          statusArea.setBorder(BorderFactory.createEtchedBorder());
          statusArea.setLayout(new FlowLayout(FlowLayout.LEFT,0,0));
          statusArea.add(status);
          status.setHorizontalAlignment(JLabel.LEFT);
          f.setDefaultCloseOperation(
                                   WindowConstants.DISPOSE_ON_CLOSE);
          f.addWindowListener(new WindowAdapter() {
               public void windowClosed(WindowEvent e) {
                    System.exit(0);
     static public JPanel getStatusArea() {
          return statusArea;
     static public void updateStatus(String s) {
          status.setText(s);
Thanks in advance.

Answer 1

Hi Paul,
sorry for my late reply, but I usually don't work on weekends (this time it was an exception).
OK, then, to your problem:
- at the first look I thought you did NOT follow all the instruction (namely, the constructor of your trees has no info that you want to use model, or whatsoever), but later I realized that your approach: create the tree first and then assign a model to it (or in fact, get the model from the tree via: tree.getModel()) might work as well
- having no debugger I am not able to have much clue about your program / and it seems that you coding suffers from your being in a hurry:
- no comments - don't know which method is expected to do what
- misleading names (createTreeModel does nothing with the model, but creates some new nodes??)
therefore, I'm sorry, but I'm not able to detect exactly where the error is.
- anyway, having a quick glance on your code I have some suspections:
- you have 2 trees (treeLeft, treeRight), but just one model (model)
( it seems that you assign it dynamically when needed - either you take the model of the left or of the right tree)
- however, when this assignment takes place (in createTestTree()), you DO NOT ASSIGN IT to the class' protected attribute model, but to a local variable model (of the same type, however - since you introduce it as:
DefaultTreeModel model you override the model from class' attributes) - therefore, your assignment is no valid when the block in which ot is located is finished
- note, that you NEED the model when you add/delete nodes of the tree (somewhere in DnDTree? - then quite probably your local assignment of model is not valid any longer)
My suggestion, therefore, is:
somehow try to encapsulate the model to your tree (note that I only created the model outside the tree, because I needed it for running the constructor, but all other usages of the model are made WITHIN the class of the tree) - the best, do it the same way - through the constructor
then, in the place when you insert/remove nodes you will have no problem at all
I will e-mail you my whole "project" so that you may observe all parts - how it's written. I trust if you can't figure it out from my writings here (maybe I missed the point) you may get it from that example.
Hope it helps - GOOD LUCK