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()));
    }
}

}

class Shape {

private double s; // 周长

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

public double getS() {
    return s;
}

}

interface Area { double getArea(); // 面积 }

// 圆形 class Circle extends Shape implements Area {

//write your code here......
public Circle(double s){
    super(s);
}

@Override
public double getArea(){
    double r = this.getS()/(2 * Math.PI);
    return (Math.PI)*r*r;
}

}

// 方形 class Square extends Shape implements Area {

//write your code here......
public Square(double s){
    super(s);
}

@Override
public double getArea(){
    double r = this.getS()/4;
    return r*r;
}

}