定义一个抽象类Shape，它包含一个抽象方法getArea0，从Shape类派生出Rectangle和 Cirele类，这两个类都用getArea0方法计算对象的面积。编写测试类创建Rectangle和 Circle对象，并分别打印输出它们的面积：

好的，下面是代码实现：

// Shape.java
public abstract class Shape {
    public abstract double getArea0();
}

// Rectangle.java
public class Rectangle extends Shape {
    private double width;
    private double height;

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

    public double getWidth() {
        return width;
    }

    public double getHeight() {
        return height;
    }

    @Override
    public double getArea0() {
        return width * height;
    }
}

// Circle.java
public class Circle extends Shape {
    private double radius;

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

    public double getRadius() {
        return radius;
    }

    @Override
    public double getArea0() {
        return Math.PI * radius * radius;
    }
}

// Test.java
public class Test {
    public static void main(String[] args) {
        Shape rect = new Rectangle(5, 8);
        System.out.println("Rectangle Area: " + rect.getArea0());

        Shape circle = new Circle(4);
        System.out.println("Circle Area: " + circle.getArea0());
    }
}

输出结果为：

Rectangle Area: 40.0
Circle Area: 50.26548245743669