利用Java计算圆的面积

import java.util.Scanner;

public class yuan {
    public static void main(String[] args) {
        double radius;
        double area;
        Scanner input = new Scanner(System.in);
        System.out.println("请输入半径值：");
        radius = input.nextDouble();
        area = Math.PI * radius *radius;
        System.out.println("圆的面积为：" + area);
    }
}