循环序列停止

Question

我将代码放入do，while循环中。它询问用户他们想要哪个菜单选项，并为其计算方程式。该代码应该一直继续下去，直到用户按下4（这是退出选项）为止，但是在他们打了一个序列之后它就停止了。我不知道我需要更改或添加什么，所以它一直在继续

import java.util.Scanner;
import java.text.DecimalFormat;
class Lab5

    public static void main(String[] args) //header of the main method
    
     Scanner in = new Scanner(System.in);

     int choice;
     int rem = 0;
     int num;

     do
   
         //user prompt
     System.out.print("Choose from the following menu\n1)   Calculate the sum of integers 1 to m\n2)    Factorial of a number\n3)   Repeat the first number\n4) Quit\n:");
     choice = in.nextInt();




     switch(choice)
     
         case 1:
         int m, sum =0;
         int i = 1;
         System.out.print("Enter the number:");
         m = in.nextInt();
         while (i <= m)
         
             sum=sum+i;
             i++;

            System.out.print("The sum of:" + m + ' ' + "is" + ' ' + sum);
         break;


         case 2:
         int number, fact =1;
         System.out.print("Enter the number:");
         number = in.nextInt();
         i=1;

         for (int factor = 2; factor <= number; factor++)
         
             fact = fact*factor;

         System.out.print("The Factorial of +:" + number + ' ' + "is" + ' ' + fact);
                 break;
         case 3:

         System.out.print("Enter the number:");
         num = in.nextInt();


        while(num!=0)
        
            rem = num%10;
            num = num/10;
        
     System.out.print("The leftmost digit is:" + rem);
                 break;

         default:
                 break;



     while (choice == '4');
    System.out.print(" ");