使用While循环计算平均问题

import java.util.Scanner; // program uses class Scanner
/* 
 来自 
*时代Java公众号*/


public class Main 

{

   public static void main(String[] args)

   {

      // create Scanner to obtain input from command window

      Scanner input = new Scanner(System.in);


      // initialization phase

      int total = 0; // initialize sum of grades

      int gradeCounter = 0; // initialize # of grades entered so far

      

      System.out.print("Enter grade or -1 to quit: "); 

      int grade = input.nextInt(); 


      // loop until sentinel value read from user

      while (grade != -1) 

      {

         total = total + grade; // add grade to total
         /** 
          来自 N o w J a v a . c o m**/

         gradeCounter = gradeCounter + 1; // increment counter 


         // prompt for input and read next grade from user

         System.out.print("Enter grade or -1 to quit: "); 

         grade = input.nextInt(); 

      }


      // if user entered at least one grade...

      if (gradeCounter != 0) 

      {

         // use number with decimal point to calculate average of grades

         double average = (double) total / gradeCounter;  


         // display total and average (with two digits of precision)

         System.out.printf(