public class ShapeUtil {
    // 统一打印面积的静态方法：支持所有Shape子类
    public static void printArea(Shape shape) {
        if (shape == null) {
            System.out.println("图形不能为空！");
            return;
        }
        double area = shape.getArea();
        System.out.printf("图形面积为：%.2f%n", area);
    }
}