JSliderのノブをドラッグ中にToolTipで値を表示

class SliderPopupListener extends MouseAdapter {
  private final JWindow toolTip = new JWindow();
  private final JLabel label = new JLabel("", SwingConstants.CENTER);
  private final Dimension size = new Dimension(30, 20);
  private int prevValue = -1;

  public SliderPopupListener() {
    label.setOpaque(false);
    label.setBackground(UIManager.getColor("ToolTip.background"));
    label.setBorder(UIManager.getBorder("ToolTip.border"));
    toolTip.add(label);
    toolTip.setSize(size);
  }

  protected void updateToolTip(MouseEvent me) {
    JSlider slider = (JSlider) me.getSource();
    int intValue = (int) slider.getValue();
    if (prevValue != intValue) {
      label.setText(String.format("%03d", slider.getValue()));
      Point pt = me.getPoint();
      pt.y = -size.height;
      SwingUtilities.convertPointToScreen(pt, (Component) me.getSource());
      pt.translate(-size.width / 2, 0);
      toolTip.setLocation(pt);
    }
    prevValue = intValue;
  }

  @Override public void mouseDragged(MouseEvent me) {
    updateToolTip(me);
  }

  @Override public void mousePressed(MouseEvent me) {
    toolTip.setVisible(true);
    updateToolTip(me);
  }

  @Override public void mouseReleased(MouseEvent me) {
    toolTip.setVisible(false);
  }
}