public class Main {
    public static void main(String[] args) {
        // 创建不同图形
        Shape circle = new Circle(5);
        Shape rectangle = new Rectangle(4, 6);
        Shape triangle = new Triangle(3, 4);

        // 统一打印面积
        ShapeUtil.printArea(circle);
        ShapeUtil.printArea(rectangle);
        ShapeUtil.printArea(triangle);
    }
}