蓝桥官网练习系统-BEGIN-003-圆的面积

点击查看：蓝桥官网练习系统题解目录

题目003 – 圆的面积

题解代码

import java.util.Scanner;
public class Main{
    public static void main(String[] args) {
	  // TODO Auto-generated method stub
	  Scanner in = new Scanner(System.in);
	  int r = in.nextInt();
	  double m = Math.atan(1.0)*4*r*r;
	  System.out.printf("%.7f",m); 
   }
}