Swing/PaintPanel のバックアップ(No.16)

class PaintPanel extends JPanel
                 implements MouseMotionListener, MouseListener {
  private Point startPoint = new Point(-10, -10);
  private Point p = new Point(-10, -10);
  public PaintPanel() {
    super();
    addMouseMotionListener(this);
    addMouseListener(this);
  }
  @Override public void paintComponent(Graphics g) {
    //super.paintComponent(g);
    Graphics2D g2d = (Graphics2D) g.create();
    g2d.setStroke(new BasicStroke(3f));
    g2d.setPaint(Color.BLACK);
    g2d.drawLine(startPoint.x, startPoint.y, p.x, p.y);
    g2d.dispose();
    startPoint = p;
  }
  @Override public void mouseDragged(MouseEvent e) {
    p = e.getPoint();
    repaint();
  }
  @Override public void mouseMoved(MouseEvent e)    {}
  @Override public void mouseExited(MouseEvent e)   {}
  @Override public void mouseEntered(MouseEvent e)  {}
  @Override public void mouseReleased(MouseEvent e) {}
  @Override public void mouseClicked(MouseEvent e)  {}
}