Problem with JTree.isExpanded()

Question

Working with a JTree, I encountered into a strange behavior - I hope someone could explain me...
For exporting a tree I need the information whether nodes are expanded or not.
The first strange thing is that the root always seems to be collapsed - but this I can handle somehow.
The problem is, that a expanded node containing a leaf, is reported as collapsed - but it is not. Why?
Here the output of a expand-checking method, which prints the state of the node and its parents.
(the "+" indicates a expanded node, the "-" indicated a collapsed node)
+ - Abasdf
+ - EP/asdf
+ - - Prosadf
+ - - - Altasdf
+ - - - - V1sadf
+ - - - - - 059asdf
+ - - - - - - 059asdf
+ - - - - - - + 059asdf
+ - - - - - - + + this_is_a_leafWhy is the expanded node containing the leaf reported as collapsed?
I'm using the following for checking if a node is expanded:
view.isExpanded(node.getIndex())I also tried this - with the same wrong result:
view.isExpanded(view.getPathForRow(node.getIndex()))Any hint is highly appretiated.

Answer 1

I was not able to reproduce your problemimport javax.swing.*;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreePath;
import javax.swing.tree.TreeNode;
import java.util.Random;
import java.util.Enumeration;
import java.awt.*;
import java.awt.event.ActionEvent;
public class HamsterChipsyTest extends JPanel {
     private static final Random RANDOM = new Random(System.currentTimeMillis());
     private JTree theTree;
     private DefaultTreeModel theTreeModel;
     private DefaultMutableTreeNode theRoot;
     public HamsterChipsyTest() {
          super(new BorderLayout());
          theRoot = createRandomNode();
          addNodes(theRoot, 0, 2);
          theTreeModel = new DefaultTreeModel(theRoot);
          theTree = new JTree(theTreeModel);
          add(new JScrollPane(theTree), BorderLayout.CENTER);
          add(new JButton(new AbstractAction("dump nodes' extension state") {
               public void actionPerformed(ActionEvent e) {
                    dumpExtensionState(theRoot);
          }), BorderLayout.NORTH);
     private void dumpExtensionState(DefaultMutableTreeNode aTreeNode) {
          TreeNode[] path = aTreeNode.getPath();
          for (int i = 0; i < path.length; i++) {
               System.out.print('-');
          System.out.println(" " + aTreeNode.getUserObject().toString() + " " + theTree.isExpanded(new TreePath(path)));
          Enumeration children  = aTreeNode.children();
          while(children.hasMoreElements()) {
               DefaultMutableTreeNode child = (DefaultMutableTreeNode)children.nextElement();
               dumpExtensionState(child);
     private static void addNodes(DefaultMutableTreeNode aParent, int aCurrentDepth, int aMaxDepth) {
          if (aCurrentDepth >= aMaxDepth) return;
          int nodeCount = RANDOM.nextInt(3);
          for (int i = 0; i < nodeCount + 1; i++) {
               DefaultMutableTreeNode child = createRandomNode();
               aParent.add(child);
               addNodes(child, aCurrentDepth + 1, aMaxDepth);
     private static DefaultMutableTreeNode createRandomNode() {
          char[] chars = new char[5];
          for (int i = 0; i < chars.length; i++) {
               chars[i] = (char)('a' + RANDOM.nextInt(26));
          return new DefaultMutableTreeNode(new String(chars));
     public static void main(String[] args) {
          final JFrame frame = new JFrame(HamsterChipsyTest.class.getName());
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          frame.setContentPane(new HamsterChipsyTest());
          SwingUtilities.invokeLater(new Runnable() {
               public void run() {
                    frame.pack();
                    frame.show();
}