JTabbedPaneの余白にJCheckBoxを配置

class TabbedPaneWithCompBorder implements Border, MouseListener, SwingConstants {
  private final JComponent  dummy = new JPanel();
  private final JCheckBox   cbox;
  private final JTabbedPane tab;
  private Rectangle rect;
  public TabbedPaneWithCompBorder(JCheckBox cbox, JTabbedPane tab) {
    this.cbox = cbox;
    this.tab  = tab;
    tab.addMouseListener(this);
    cbox.setFocusPainted(false);
    cbox.addMouseListener(new MouseAdapter() {
      @Override public void mouseClicked(MouseEvent me) {
        ((AbstractButton) me.getComponent()).doClick();
      }
    });
  }

  @Override public void paintBorder(Component c, Graphics g, int x, int y, int w, int h) {
    Dimension size = cbox.getPreferredSize();
    int xx = tab.getSize().width - size.width;
    Rectangle lastTab = tab.getBoundsAt(tab.getTabCount() - 1);
    int tabEnd = lastTab.x + lastTab.width;
    if (xx < tabEnd) {
      xx = tabEnd;
    }
    rect = new Rectangle(xx, -2, size.width, size.height);
    SwingUtilities.paintComponent(g, cbox, dummy, rect);
  }

  @Override public Insets getBorderInsets(Component c) {
    return new Insets(0, 0, 0, 0);
  }

  @Override public boolean isBorderOpaque() {
    return true;
  }

  private void dispatchEvent(MouseEvent me) {
    if (rect == null || !rect.contains(me.getX(), me.getY())) {
      return;
    }
    cbox.setBounds(rect);
    cbox.dispatchEvent(SwingUtilities.convertMouseEvent(tab, me, cbox));
  }

  @Override public void mouseClicked(MouseEvent me) {
    dispatchEvent(me);
  }

  @Override public void mouseEntered(MouseEvent me) {
    dispatchEvent(me);
  }

  @Override public void mouseExited(MouseEvent me) {
    dispatchEvent(me);
  }

  @Override public void mousePressed(MouseEvent me) {
    dispatchEvent(me);
  }

  @Override public void mouseReleased(MouseEvent me) {
    dispatchEvent(me);
  }
}