class Shape { }
class Triangle extends Shape { }
class Square extends Shape { }
class Circle extends Shape { }
    
class Canvas {
    public void draw(Shape s) {
        System.out.println("Drawing shape " + s);
    }
}
class SpecialCanvas extends Canvas {
    public void draw(Triangle t) {
        System.out.println("Special drawing triangle " + t);
    }
    public void draw(Square s) {
        System.out.println("Special drawing square " + s);
    }
}
    
class Dispatch {
    public static void main(String...args) {
	SpecialCanvas c = new SpecialCanvas();
	System.out.println("Try to draw some shapes:");
	for (Shape s : new Shape[] { new Circle(), new Triangle(), new Square() })
	    c.draw(s);
	System.out.println("Lets try a plain triangle instead");
	c.draw(new Triangle());
    }
}