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Editorial Team
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Asked: 2026-06-17T12:10:16+00:00

I have a Java SE 7 application that needs to have the JTree nodes

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I have a Java SE 7 application that needs to have the JTree nodes updated. From the tutorial given by Oracle using this thread, there’s no given hint on how I could update the label (displayed text of the node on the Tree) on code. Currently I am using DefaultTreeModel as the model of my JTree and DefaultMutableTreeNode as the nodes of the said Tree.

To further detail about the application I am working on, I am developing a chat facility having the contact(s) displayed with their availability status (whether Online, Offline, etc.) per account.

The question is, how can I update the displayed text of a particular node without (at most) removing it from it’s parent and adding it on it’s designated index. Like a DefaultMutableTreeNode.setText("<new label>")?

UPDATE : January 20, 2013

Redefined the question for clarifications.

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1 Answer

  1. Editorial Team

    May this simple and executable program help you to resolve your issue.

    public class JTreeDemo  extends JPanel
    implements Runnable {

private JTree tree;
private DefaultTreeModel treeModel ;
private Random rnd = new Random();
private List<User> userList;
public JTreeDemo() {
    super( );

    //Create the nodes.
    DefaultMutableTreeNode top =
        new DefaultMutableTreeNode("Users");
    treeModel = new DefaultTreeModel(top);
    createNodes(top);

    //Create a tree that allows one selection at a time.
    tree = new JTree(treeModel);
    tree.getSelectionModel().setSelectionMode
            (TreeSelectionModel.SINGLE_TREE_SELECTION);

    //Create the scroll pane and add the tree to it. 
    JScrollPane treeView = new JScrollPane(tree);


    //Add the split pane to this panel.
    add(treeView);
}

public String getRandomStatus() {
    int nextInt = rnd.nextInt(100);
    if( nextInt%2==0) {
        return "Online";
    } else {
        return "Offline";
    }
}
@Override
public void run() {
     while(true) {
        try {   
          Thread.sleep(1000);
          int nextInt = rnd.nextInt(10);
          User user = userList.get(nextInt);
          user.setStatus(getRandomStatus());
          treeModel.nodeChanged(user);
        } catch (InterruptedException ex) {
            // handle it if necessary
        }
     }
}

private class User extends DefaultMutableTreeNode {
    public String userName;
    public String status;

    public User(String name) {
        userName = name;

    }

    public void setStatus(String status) {
        this.status = status;
    }

    public String getStatus() {
        return status;
    }

    @Override
    public String toString() {
        String color = status.equals("Online") ? "Green" : "Red";
        return "<html><b color='"+color+"'>"+
                userName +"-"+status +"</b></html>";
    }

}


private void createNodes(DefaultMutableTreeNode top) {
    userList = new ArrayList() ;
    for(int i=0;i<10;i++) {
        User u1 = new User("User " + (i+1));
        u1.setStatus("Online");
         top.add(u1);
         userList.add(u1);
    }
}

private static void createAndShowGUI() {

    JFrame frame = new JFrame("TreeDemo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    //Add content to the window.
    JTreeDemo jTreeDemo = new JTreeDemo();
    frame.add(jTreeDemo);
    frame.pack();
    frame.setVisible(true);
    // update status randomly
    Thread thread = new Thread(jTreeDemo);
    thread.start();
}

 public static void main(String[] args) {
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            createAndShowGUI();
        }
    });
 }
}

    I’ve added a Thread to update Status randomly, hope you can modify base on your need.

    Output :
    enter image description here

    Edit:
    1. Based on suggestion I’ve removed reload(node) and added tree model reload.

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