Java - проблема с узлами JTree и JCheckBox

Question

Я работаю над Java и пытаюсь создать JTree с выбираемыми конечными узлами (узлами JCheckBox).

Я нашел этот пример, в котором простое JTree сделан. Затем я нашел здесь классы для средства визуализации и редактора ячеек.

После объединения всего этого я пришел к следующему коду:

import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.tree.*;
import java.awt.Component;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.MouseEvent;
import java.util.EventObject;

public class TestingJTree {
    public static void main(String[] args) {
        DefaultMutableTreeNode treeNode = new DefaultMutableTreeNode("GrandFather");
        DefaultMutableTreeNode padre = new DefaultMutableTreeNode("father");
        DefaultMutableTreeNode tio = new DefaultMutableTreeNode("uncle");
        DefaultTreeModel treeModel = new DefaultTreeModel(treeNode);
        treeModel.insertNodeInto(padre, treeNode, 0);
        treeModel.insertNodeInto(tio, treeNode, 1);
        DefaultMutableTreeNode hijo = new DefaultMutableTreeNode("son");
        treeModel.insertNodeInto(hijo, padre, 0);
        JTree tree = new JTree(treeModel);
        tree.setCellRenderer(new CheckBoxNodeRenderer());
        tree.setCellEditor(new CheckBoxNodeEditor(tree));
        JFrame v = new JFrame();
        JScrollPane scroll = new JScrollPane(tree);
        v.getContentPane().add(scroll);
        v.pack();
        v.setVisible(true);
        v.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    }
}

class CheckBoxNodeRenderer implements TreeCellRenderer {
    private JCheckBox leafRenderer = new JCheckBox();
    private DefaultTreeCellRenderer nonLeafRenderer = new DefaultTreeCellRenderer();

    public JCheckBox getLeafRenderer() {
        return leafRenderer;
    }

    public CheckBoxNodeRenderer() {
        super();
    }

    @Override
    public Component getTreeCellRendererComponent(JTree tree, Object value, boolean selected,
            boolean expanded, boolean leaf, int row, boolean hasFocus) {
        // TODO Auto-generated method stub
        Component returnValue;
        if (leaf) {
            String stringValue = tree.convertValueToText(value, selected, expanded, leaf, row,
                    false);
            leafRenderer.setText(stringValue);
            leafRenderer.setSelected(false);
            // leafRenderer.setEnabled(tree.isEnabled());
            leafRenderer.setEnabled(true);
            if ((value != null) && (value instanceof DefaultMutableTreeNode)) {
                Object userObject = ((DefaultMutableTreeNode) value).getUserObject();
                if (userObject instanceof CheckBoxNode) {
                    CheckBoxNode node = (CheckBoxNode) userObject;
                    leafRenderer.setText(node.getText());
                    leafRenderer.setSelected(node.isSelected());
                }
            }
            returnValue = leafRenderer;
        } else {
            returnValue = nonLeafRenderer.getTreeCellRendererComponent(tree, value, selected,
                    expanded, leaf, row, hasFocus);
        }
        return returnValue;
    }
}

class CheckBoxNode {
    private String text;
    private boolean selected;

    public CheckBoxNode(String text, boolean selected) {
        this.setText(text);
        this.selected = selected;
    }

    public boolean isSelected() {
        return selected;
    }

    public void setSelected(boolean newValue) {
        selected = newValue;
    }

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }
}

class CheckBoxNodeEditor extends AbstractCellEditor implements TreeCellEditor {
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private JTree tree;
    private CheckBoxNodeRenderer renderer = new CheckBoxNodeRenderer();
    private ChangeEvent changeEvent = null;

    public CheckBoxNodeEditor(JTree tree) {
        this.tree = tree;
    }

    @Override
    public Object getCellEditorValue() {
        // TODO Auto-generated method stub
        JCheckBox checkBox = renderer.getLeafRenderer();
        CheckBoxNode checkBoxNode = new CheckBoxNode(checkBox.getText(), checkBox.isSelected());
        return checkBoxNode;
    }

    public boolean isCellEditable(EventObject event) {
        boolean returnValue = false;
        if (event instanceof MouseEvent) {
            MouseEvent mouseEvent = (MouseEvent) event;
            TreePath path = tree.getPathForLocation(mouseEvent.getX(), mouseEvent.getY());
            if (path != null) {
                Object node = path.getLastPathComponent();
                if ((node != null) && (node instanceof DefaultMutableTreeNode)) {
                }
                DefaultMutableTreeNode treeNode = (DefaultMutableTreeNode) node;
                Object userObject = treeNode.getUserObject();
                returnValue = ((treeNode.isLeaf()) && (userObject instanceof CheckBoxNode));
            }
        }
        return returnValue;
    }

    @Override
    public Component getTreeCellEditorComponent(JTree tree, Object value, boolean isSelected,
            boolean expanded, boolean leaf, int row) {
        // TODO Auto-generated method stub
        Component editor = renderer.getTreeCellRendererComponent(tree, value, true, expanded, leaf,
                row, true);
        ItemListener itemListener = new ItemListener() {
            @Override
            public void itemStateChanged(ItemEvent e) {
                // TODO Auto-generated method stub
                if (stopCellEditing()) {
                    fireEditingStopped();
                }
            }
        };
        if (editor instanceof JCheckBox) {
            ((JCheckBox) editor).addItemListener(itemListener);
        }
        return editor;
    }
}

Проблема в том, что листовые узлы не могут быть выбраны:

Любая помощь будет оценена ... Спасибо!