题解 | #根据周长求面积#

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextDouble()) {
            double s = scanner.nextDouble();
            // Circle和Square是需要你定义的类
            System.out.println(String.format("%.3f",new Circle(s).getArea()));
            System.out.println(String.format("%.3f", new Square(s).getArea()));
        }
    }

}
//1. 图形类Shape，该类中定义了图形的周长属性，以及返回周长的方法
class Shape {

    private double s; // 周长

    public Shape(double s) {
        this.s = s;
    }

    public double getS() {
        return s;
    }

}

interface Area {
    // Area接口，该接口中定义了返回面积的方法getArea()
    double getArea(); // 面积
}

// 圆形
class Circle extends Shape implements Area {

    //write your code here......
    public Circle(double s){
        super(s);//初始化属性
    }
    @Override
    public double getArea(){
        //获取r
        double r=super.getS()/(2*Math.PI);
        double area=Math.PI*(Math.pow(r,2));
        return area;
    }

}

// 方形
class Square extends Shape implements Area {

    //write your code here......
     public Square(double s){
        super(s);//初始化属性
    }
      @Override
    public double getArea(){
        double long1=super.getS()/4;
        double area=Math.pow(long1,2);
        return area;
    }
    

}