计算器实现加减乘除

package com.baidu.www;

import java.util.Scanner;

public class JiShuanQi {
    public static void main(String[] args) {
        //实现用户输入
        Scanner scanner = new Scanner(System.in);

        while (true){
            double num1= scanner.nextDouble();
            String next = scanner.next();
            double num2= scanner.nextDouble();
            double num3=num1;//难点
          double num4=num2;
            double result =0;
            if(next.equals("+")){
                result = add(num1,num2);

            }
            if(next.equals("-")){
                result = jian(num1,num2);

            }
            if(next.equals("*")){
                result = cheng(num1,num2);

            }
            if(next.equals("/")){
                result = chu(num1,num2);

            }
            if(next.equals("!")){
                break;

            }
            System.out.println(result);
        }

    }
    public static  double add(double a, double b){
        return a+b;
    }

    public static double jian(double a,double b) {
        return a-b;
    }
    public static double cheng(double a,double b) {
        return a*b;
    }
    public static double chu(double a,double b) {
        return a/b;
    }
}