public class ShapeUtil {

    public void printArea(Shape shape) {
        System.out.println("图形的面积为：" + shape.getArea());
    }

    public static void main(String[] args) {
        ShapeUtil util = new ShapeUtil();
        util.printArea(new Circle(5));
        util.printArea(new Rectangle(4, 3));
        util.printArea(new Triangle(3, 4));
    }
}