public class Main {
    public static void main(String[] args) {
        // 创建图形对象
        Shape circle = new Circle(3);
        Shape rectangle = new Rectangle(4, 5);
        Shape triangle = new Triangle(6, 8);

        // 统一计算并打印面积
        ShapeUtil.printArea(circle);
        ShapeUtil.printArea(rectangle);
        ShapeUtil.printArea(triangle);
    }
}