class Shape {
    public void draw() {
        System.out.println("绘制一个形状");
    }
}

class Circle extends Shape {
    @Override
    public void draw() {
        System.out.println("绘制一个圆形 ○");
    }
}

class Rectangle extends Shape {
    @Override
    public void draw() {
        System.out.println("绘制一个矩形 ▭");
    }
}