public class ShapeTest{
    // 统一绘制方法
    public static void drawShape(Shape s) {
        s.draw();
    }

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

        drawShape(circle);    // 输出：绘制一个圆形 🟡
        drawShape(rectangle); // 输出：绘制一个矩形 🟦
    }
}