圆的面积

本题考查的是实数的精度问题

问题描述

import java.text.DecimalFormat;import java.util.Scanner;public class Main {public static void main(String[] args) {	Scanner sc = new Scanner(System.in);	int r = sc.nextInt();	DecimalFormat re = new DecimalFormat("#.0000000");	double area = Math.PI*r*r;	System.out.PRint(re.format(area));}}