void processShape(Shape s) {
        s.setColor(Color.red);
        // ... do stuff
        s.draw();
	}
	
	Circle c = new Circle(x, y, r);
	
	Point2D v1 = new Point2D(x1, y1);
	Point2D v2 = new Point2D(x2, y2);
	Point2D v3 = new Point2D(x3, y3);
	Triangle t = new Triangle(v1, v2, v3);
	
	Point2D c1 = new Point2D(u1, v1);
	Point2D c2 = new Point2D(u2, v2);
	Triangle r = new Rectangle(c1, c2);
	
	processShape(c);
	processShape(t);
	processShape(r);