JTreeの葉ノードをJCheckBoxにする

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

  @Override public String toString() {
    return text;
  }
}

JTree tree = new JTree() {
  @Override public void updateUI() {
    setCellRenderer(null);
    setCellEditor(null);
    super.updateUI();
    // ???: JDK 1.6.0 LnF bug???
    setCellRenderer(new CheckBoxNodeRenderer());
    setCellEditor(new CheckBoxNodeEditor());
  }
};

class CheckBoxNodeRenderer extends JCheckBox implements TreeCellRenderer {
  private JTree tree = null;
  private DefaultTreeCellRenderer renderer = new DefaultTreeCellRenderer();
  @Override public Component getTreeCellRendererComponent(JTree tree,
      Object value, boolean selected, boolean expanded,
      boolean leaf, int row, boolean hasFocus) {
    this.tree = tree;
    if (leaf && value instanceof DefaultMutableTreeNode) {
      this.setEnabled(tree.isEnabled());
      this.setFont(tree.getFont());
      this.setOpaque(false);
      Object userObject = ((DefaultMutableTreeNode) value).getUserObject();
      if (userObject instanceof CheckBoxNode) {
        CheckBoxNode node = (CheckBoxNode) userObject;
        this.setText(node.text);
        this.setSelected(node.selected);
      }
      return this;
    }
    return renderer.getTreeCellRendererComponent(
        tree, value, selected, expanded, leaf, row, hasFocus);
  }

  @Override public void updateUI() {
    super.updateUI();
    setName("Tree.cellRenderer");
  }
}

class CheckBoxNodeEditor extends JCheckBox implements TreeCellEditor {
  private final JTree tree;
  public CheckBoxNodeEditor(JTree tree) {
    super();
    this.tree = tree;
    setFocusable(false);
    setRequestFocusEnabled(false);
    setOpaque(false);
    addActionListener(new ActionListener() {
      @Override public void actionPerformed(ActionEvent e) {
        stopCellEditing();
      }
    });
  }

  @Override public Component getTreeCellEditorComponent(JTree tree,
      Object value, boolean isSelected, boolean expanded, boolean leaf, int row) {
    if (leaf && value instanceof DefaultMutableTreeNode) {
      Object userObject = ((DefaultMutableTreeNode) value).getUserObject();
      if (userObject instanceof CheckBoxNode) {
        this.setSelected(((CheckBoxNode) userObject).selected);
      } else {
        this.setSelected(false);
      }
      this.setText(value.toString());
    }
    return this;
  }

  @Override public Object getCellEditorValue() {
    return new CheckBoxNode(getText(), isSelected());
  }

  @Override public boolean isCellEditable(EventObject e) {
    if (e instanceof MouseEvent) {
      TreePath path = tree.getPathForLocation(
          ((MouseEvent) e).getX(), ((MouseEvent) e).getY());
      Object o = path.getLastPathComponent();
      if (o instanceof TreeNode) {
        return ((TreeNode) o).isLeaf();
      }
    }
    return false;
  }
// ...