Java提问 你们加油

创建一个图形父类Shape,该类中有1个抽象方法Area()，两个派生类圆形类Cirle，矩形类Rectangle，在派生类中重写抽象方法Area()。创建一个测试类Test，输出圆和矩形的面积。

三个类的写法可以参考下：

    public abstract  class  Shape {
        public abstract double Area();
    }
    
    public class Circle extends Shape{
         int r;
         public Circle(int r) {
             this.r = r;
         }
         @Override
         public double Area() {
             return Math.PI*r*r;
         }
     }

    public class Rectangle extends Shape {
         int a;
         int b;
        public Rectangle(int a, int b) {
            this.a = a;
            this.b = b;
        }
        @Override
        public double Area() {
            return a*b;
        }
    }

你这都分析明白了啊，你是要代码吗

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public abstract  class  Shape {
    public abstract double Area();
}
public class Circle extends Shape{
    private int r;
     public Circle(int length) {
         this.r = length;
     }
     @Override
     public double Area() {
         return Math.PI*r*r;
     }
 }
public class Rectangle extends Shape {
    private double a;
    private double b;
    public Rectangle(double a, double b) {
        this.a = a;
        this.b = b;
    }
    @Override
    public double Area() {
        return a*b;
    }
}

public class ShapeTest {
    public static void main(String[] args) {
        Circle c=new Circle(3);
        Triangle t=new Triangle(3,4);
        System.out.println("圆的面积："+c.Area());
        System.out.println("矩形面积："+t.Area());
    }
}

package mianji;

public abstract class Shape {
public abstract void Area();

}//////
package mianji;

public class Cirle extends Shape {
int r = 2;
double l = 3.14;
@Override
public void Area() {
// TODO Auto-generated method stub
System.out.println("圆的面积："+lrr);
}
}
/////
package mianji;

public class Rectangle extends Shape {
int chang =2;
int kuan =2;
@Override
public void Area() {
// TODO Auto-generated method stub
System.out.println("矩形的面积"+chang*kuan);
}
}
///////////
package mianji;

public class Test {
public static void main(String[] args) {
Shape a =new Cirle();
Shape b =new Rectangle();
a.Area();
b.Area();
}
}