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

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

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

public class ShapeTest {
    public static void drawShape(Shape s) {
        s.draw(); 
    }

    public static void main(String[] args) {
        Shape circle = new Circle();
        Shape rect = new Rectangle();
        drawShape(circle);
        drawShape(rect);
    }
}