Expand and Collapse two trees with same structure simultaneously

I want to modify the standard JTree in Swing example as given in this link -> Dynamic Tree Example A screenshot of the app is below: DynamicTreeDemo

I want to use this structure to maintain two trees, both having exactly the same structure. I should be able to collapse and expand both simultaneously when either is collapsed/expanded by a mouse click!
Also, when user selects a node from either tree, the corresponding node in the other tree should get highlighted too.
One tree might contain files/folders as nodes, and the other might have time of creation as nodes.

Can I get this to work using only one Jtree object in each DynamicTree object? (Please refer to the example to see what these objects are) Is there any way to get the Jtree to store only one object containing data from corresponding nodes of each tree but to display these data on separate trees?

Currently, I am using two Jtrees and can add nodes by taking two parents and two children as inputs to the add function, and adding corresponding child to the corresponding parent.
However, in the remove/expand/collapse function, I need to remove/expand/collapse two corresponding nodes from two trees. How do I do this?

I am new to java swing but not to java programming. So please elucidate the parts requiring knowledge of Jswing.

Thanks in advance.

So, the trick is to use a single TreeModel, link the tree's SelectionModels and two custom TreeCellRenderers and use a TreeExpansionListener capable of determine which tree expanded/collapsed and mirror the results.

Basically, each tree shares the same TreeModel and SelectionModel, this makes life so much simpler as they will both respond to changes that are made to both models.

Expansion/collapse is a little more difficult, as this needs to be handled via a custom TreeExpansionListener, which is detects who triggered the event and then notifies the opposite tree of the change.

Next, I use a common "data object" with, this contains basic information about the data that should be shown by the tree's...

Finally, I use two different TreeCellRenderers to render different aspects of the data maintained by the TreeModel

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.event.TreeExpansionEvent;
import javax.swing.event.TreeExpansionListener;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeCellRenderer;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.MutableTreeNode;
import javax.swing.tree.TreePath;

public class DynamicTreeDemo extends JPanel implements ActionListener {

    protected static final SimpleDateFormat SDF = new SimpleDateFormat("HH:mm:ss");

    private int newNodeSuffix = 1;
    private static String ADD_COMMAND = "add";
    private static String REMOVE_COMMAND = "remove";
    private static String CLEAR_COMMAND = "clear";

    private DefaultMutableTreeNode rootNode;
    private final DefaultTreeModel treeModel;

    private JTree left;
    private JTree right;

    public DynamicTreeDemo() {
        super(new BorderLayout());

        rootNode = new DefaultMutableTreeNode("Root Node");
        treeModel = new DefaultTreeModel(rootNode);

        left = new JTree(treeModel);
        left.setCellRenderer(new LeftTreeCellRenderer());
        right = new JTree(treeModel);
        right.setCellRenderer(new RightTreeCellRenderer());

        MyExpansionListener expansionListener = new MyExpansionListener(left, right);

        left.addTreeExpansionListener(expansionListener);
        right.addTreeExpansionListener(expansionListener);

        right.setSelectionModel(left.getSelectionModel());

        populateModel();

        JButton addButton = new JButton("Add");
        addButton.setActionCommand(ADD_COMMAND);
        addButton.addActionListener(this);

        JButton removeButton = new JButton("Remove");
        removeButton.setActionCommand(REMOVE_COMMAND);
        removeButton.addActionListener(this);

        JButton clearButton = new JButton("Clear");
        clearButton.setActionCommand(CLEAR_COMMAND);
        clearButton.addActionListener(this);

        JPanel panel = new JPanel(new GridLayout(1, 2));
        panel.add(new JScrollPane(left));
        panel.add(new JScrollPane(right));
        add(panel, BorderLayout.CENTER);

        JPanel buttons = new JPanel(new GridLayout(0, 3));
        buttons.add(addButton);
        buttons.add(removeButton);
        buttons.add(clearButton);
        add(buttons, BorderLayout.SOUTH);
    }

    protected TreeData createNodeData() {
        return new TreeData("New Node " + newNodeSuffix++, SDF.format(new Date()));
    }

    public void populateModel() {
        String p1Name = "Parent 1";
        String p2Name = "Parent 2";

        DefaultMutableTreeNode p1, p2;

        p1 = addObject(null, p1Name);
        p2 = addObject(null, p2Name);

        addObject(p1, createNodeData());
        addObject(p1, createNodeData());

        addObject(p2, createNodeData());
        addObject(p2, createNodeData());

    }

    @Override
    public void actionPerformed(ActionEvent e) {
        String command = e.getActionCommand();

        if (ADD_COMMAND.equals(command)) {
            // Add button clicked
            addObject(createNodeData());
        } else if (REMOVE_COMMAND.equals(command)) {
            // Remove button clicked
            removeCurrentNode();
        } else if (CLEAR_COMMAND.equals(command)) {
            // Clear button clicked.
            clear();
        }
    }

    /**
     * Create the GUI and show it. For thread safety, this method should be
     * invoked from the event-dispatching thread.
     */
    private static void createAndShowGUI() {
        // Create and set up the window.
        JFrame frame = new JFrame("DynamicTreeDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        // Create and set up the content pane.
        DynamicTreeDemo newContentPane = new DynamicTreeDemo();
        newContentPane.setOpaque(true); // content panes must be opaque
        frame.setContentPane(newContentPane);

        // Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        // Schedule a job for the event-dispatching thread:
        // creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }

    /**
     * Remove all nodes except the root node.
     */
    public void clear() {
        rootNode.removeAllChildren();
        treeModel.reload();
    }

    /**
     * Add child to the currently selected node.
     */
    public DefaultMutableTreeNode addObject(Object child) {
        DefaultMutableTreeNode parentNode = null;
        TreePath parentPath = left.getSelectionPath();

        if (parentPath == null) {
            parentNode = rootNode;
        } else {
            parentNode = (DefaultMutableTreeNode) (parentPath.getLastPathComponent());
        }

        return addObject(parentNode, child, true);
    }

    public DefaultMutableTreeNode addObject(DefaultMutableTreeNode parent,
            Object child) {
        return addObject(parent, child, false);
    }

    public DefaultMutableTreeNode addObject(DefaultMutableTreeNode parent,
            Object child, boolean shouldBeVisible) {
        DefaultMutableTreeNode childNode = new DefaultMutableTreeNode(child);

        if (parent == null) {
            parent = rootNode;
        }

        // It is key to invoke this on the TreeModel, and NOT DefaultMutableTreeNode
        treeModel.insertNodeInto(childNode, parent, parent.getChildCount());

        // Make sure the user can see the lovely new node.
        if (shouldBeVisible) {
            left.scrollPathToVisible(new TreePath(childNode.getPath()));
            right.scrollPathToVisible(new TreePath(childNode.getPath()));
        }
        return childNode;
    }

    /**
     * Remove the currently selected node.
     */
    public void removeCurrentNode() {
        TreePath currentSelection = left.getSelectionPath();
        if (currentSelection != null) {
            DefaultMutableTreeNode currentNode = (DefaultMutableTreeNode) (currentSelection
                    .getLastPathComponent());
            MutableTreeNode parent = (MutableTreeNode) (currentNode.getParent());
            if (parent != null) {
                treeModel.removeNodeFromParent(currentNode);
                return;
            }
        }

    }

    public class TreeData {

        private String left;
        private String right;

        public TreeData(String left, String right) {
            this.left = left;
            this.right = right;
        }

        public String getLeft() {
            return left;
        }

        public String getRight() {
            return right;
        }

    }

    public class LeftTreeCellRenderer extends DefaultTreeCellRenderer {

        @Override
        public Component getTreeCellRendererComponent(JTree tree, Object value, boolean sel, boolean expanded, boolean leaf, int row, boolean hasFocus) {
            if (value instanceof DefaultMutableTreeNode) {
                DefaultMutableTreeNode node = (DefaultMutableTreeNode) value;
                Object userData = node.getUserObject();
                if (userData instanceof TreeData) {
                    value = ((TreeData) userData).getLeft();
                }
            }
            return super.getTreeCellRendererComponent(tree, value, sel, expanded, leaf, row, hasFocus);
        }

    }

    public class RightTreeCellRenderer extends DefaultTreeCellRenderer {

        @Override
        public Component getTreeCellRendererComponent(JTree tree, Object value, boolean sel, boolean expanded, boolean leaf, int row, boolean hasFocus) {
            if (value instanceof DefaultMutableTreeNode) {
                DefaultMutableTreeNode node = (DefaultMutableTreeNode) value;
                Object userData = node.getUserObject();
                if (userData instanceof TreeData) {
                    value = ((TreeData) userData).getRight();
                }
            }
            return super.getTreeCellRendererComponent(tree, value, sel, expanded, leaf, row, hasFocus);
        }

    }

    public class MyExpansionListener implements TreeExpansionListener {

        private JTree left;
        private JTree right;

        public MyExpansionListener(JTree left, JTree right) {
            this.left = left;
            this.right = right;
        }

        @Override
        public void treeExpanded(TreeExpansionEvent event) {
            TreePath path = event.getPath();
            if (event.getSource() == left) {
                right.expandPath(path);
            } else {
                left.expandPath(path);
            }
        }

        @Override
        public void treeCollapsed(TreeExpansionEvent event) {
            TreePath path = event.getPath();
            if (event.getSource() == left) {
                right.collapsePath(path);
            } else {
                left.collapsePath(path);
            }
        }

    }
}

See How to Use Trees for more details