Method paintComponent

patterns/BoxObserver.java:57–62

(Graphics g)

      e -> notifier.notifyObservers(Box.this));
  }
  @Override public void paintComponent(Graphics g) {
    super.paintComponent(g);
    g.setColor(color);
    Dimension s = getSize();
    g.fillRect(0, 0, s.width, s.height);
  }
  @Override
  public void update(Observable o, Object arg) {
    Box clicked = (Box)arg;