用Java写一个简易计算器

import java.util.Scanner;

public class Calculator {
    public static void main(String[] args) {
        System.out.println("欢迎使用计算器！");

        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入第一个数字：");

        while (scanner.hasNextDouble()){        //while语句循环
            double num1 = scanner.nextDouble();
            System.out.println("请输入运算符号：");
            String symbol = scanner.next();
            System.out.println("请输入第二个数字：");
            double num2 = scanner.nextDouble();

            switch (symbol){        //判断计算符号
                case "+":
                    add( num1 , num2 );
                    break;
                case "-":
                    sub( num1 , num2 );
                    break;
                case "*":
                    mul( num1 , num2 );
                    break;
                case "/":
                    divi( num1 , num2 );
                    break;
                default:
                    System.out.println("您的输入不规范！");
            }
            System.out.println("输入任意字母退出！");
        }
        scanner.close();        //关闭计算器
    }
    public static void add(double num1,double num2){
        System.out.println(num1 + num2);        //加法
    }
    public static void sub(double num1,double num2){
        System.out.println(num1 - num2);        //减法
    }
    public static void mul(double num1,double num2){
        System.out.println(num1 * num2);        //乘法
    }
    public static void divi(double num1,double num2){
        if (num2 == 0){
            System.out.println("除数不能为0！");
        }else{
            System.out.println(num1 / num2);    //除法
        }
    }
}