java/w4/ShapeUtil.java

public class ShapeUtil {
    /**
     * 统一打印任意图形的面积（多态调用）
     */
    public static void printArea(Shape shape) {
        System.out.printf("%s 的面积为：%.2f%n", shape.getName(), shape.getArea());
    }

    /**
     * 找出面积最大的图形
     */
    public static Shape findLargest(Shape[] shapes) {
        Shape largest = shapes[0];
        for (Shape s : shapes) {
            if (s.getArea() > largest.getArea()) {
                largest = s;
            }
        }
        return largest;
    }
}