Java，scanner实现简易计算器

import java.util.Scanner;
 public class z1{
     public static void main(String args[]){
         Scanner scanner=new Scanner(System.in);

         System.out.println("请输入第一个数字:");
         double one=scanner.nextDouble();
         System.out.println("请输入第二个数字:");
         double two=scanner.nextDouble();
         System.out.println("请选择运算符:");
         System.out.println("1：加 2：减 3：乘 4：除");
         double operator=scanner.nextDouble();

         while(operator==4&&two<0){
             System.out.println("被除数不能为0,请重新输入:");
             two=scanner.nextDouble();
         }
         while(operator>4||operator<1){
             System.out.println("运算符不合理,请重新选择运算符:");
             System.out.println("1：加 2：减 3：乘 4：除");
             operator=scanner.nextDouble();
         }

         double result=0;
         double remainder=0;

         switch((int)operator){

             case 1:
                 result=one+two;
                 break;
             case 2:
                 result=one-two;
                 break;
             case 3:
                 result=one*two;
                 break;
             case 4:
                 result=one/two;
                 remainder=one%two;
                 break;
         }
         if (operator==4){
             System.out.println("结果为:"+result+"余数为:"+remainder);
         }else
             System.out.println("结果为:"+result);
         scanner.close();
     }
 }