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

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");
    }
}

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

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