（2）在Shape 类基础上设计圆形、矩形子类，要求根据实际形状重写getArea()方法，并设计一个TestShape 类，通过调用countArea方法把两个对象面积累加到area中，最后输出area.

首先，我们基于`Shape`类创建`Circle`和`Rectangle`子类，这两个类都重写了`gctArea()`方法并将其命名为`getArea()`以保持命名一致性：

public class Circle extends Shape {
    private double radius;

    public Circle(double radius) {
        this.radius = radius;
    }

    @Override
    public double getArea() {
        return Math.PI * radius * radius;
    }
}

public class Rectangle extends Shape {
    private double width;
    private double height;

    public Rectangle(double width, double height) {
        this.width = width;
        this.height = height;
    }

    @Override
    public double getArea() {
        return width * height;
    }
}

接下来，我们设计一个`TestShape`类，它有一个方法`countArea`用于统计两个形状的总面积：

public class TestShape {
    private double area;

    public void countArea(Shape shape1, Shape shape2) {
        area += shape1.getArea();
        area += shape2.getArea();
    }

    public void displayArea() {
        System.out.println("Total area: " + area);
    }
}

现在，你可以实例化`Circle`和`Rectangle`，并将它们传递给`TestShape`来测试面积累加：

public static void main(String[] args) {
    Circle circle = new Circle(5.0);
    Rectangle rectangle = new Rectangle(4.0, 6.0);

    TestShape test = new TestShape();
    test.countArea(circle, rectangle);
    test.displayArea();
}