Crossfadeで画像の切り替え

class Crossfade extends JComponent implements ActionListener {
  private final javax.swing.Timer animator;
  private final ImageIcon icon1;
  private final ImageIcon icon2;
  private int alpha = 10;
  private boolean direction = true;

  public Crossfade(ImageIcon icon1, ImageIcon icon2) {
    this.icon1 = icon1;
    this.icon2 = icon2;
    animator = new javax.swing.Timer(50, this);
  }

  public void animationStart() {
    direction = !direction;
    animator.start();
  }

  @Override protected void paintComponent(Graphics g) {
    Graphics2D g2 = (Graphics2D) g.create();
    g2.setPaint(getBackground());
    g2.fillRect(0, 0, getWidth(), getHeight());
    if (direction && alpha < 10) {
      alpha = alpha + 1;
    } else if (!direction && alpha > 0) {
      alpha = alpha - 1;
    } else {
      animator.stop();
    }
    g2.setComposite(AlphaComposite.getInstance(
        AlphaComposite.SRC_OVER, 1f - alpha * .1f));
    g2.drawImage(icon1.getImage(), 0, 0,
        (int) icon1.getIconWidth(), (int) icon1.getIconHeight(), this);
    g2.setComposite(AlphaComposite.getInstance(
        AlphaComposite.SRC_OVER, alpha * .1f));
    g2.drawImage(icon2.getImage(), 0, 0,
        (int) icon2.getIconWidth(), (int) icon2.getIconHeight(), this);
    g2.dispose();
  }

  @Override public void actionPerformed(ActionEvent e) {
    repaint();
  }
}