圆的面积方法之1

import java.util.Scanner;

public class AK47 {
public static void main(String[] args) {

 double r, s;
 final double PI = 3.1415926;
 Scanner sc = new Scanner(System.in);

 System.out.print("r = ");
 r = sc.nextDouble();

 s = PI * r * r;
  System.out.println("s =" + String.format("%.2f", s));

}

}

非常很有用