Java Integer.parseInt（）中断程序

Question

I have a question to do in my Java class, and it asks me to write a program that takes in n numbers from the user and outputs the average of them. I know I could do it a much simpler way, just by asking the user to enter the amount of values (s)he needs to enter at the beginning, but I want to create the program so the user doesn't necessarily have to know the number of values at the beginning. So for this, I create an array of 100 length (which hopefully covers the amount the user needs to enter) inside a for loop (rendering that 100 length array null after the loop, so the program doesn't become too memory heavy) and running a counter trough each iteration. Once the user enters stop, the loop ends, and the values entered into the 100 length array gets transferred to an array the size of the count. Here is the code:

import java.util.*;
import java.lang.*;

public class main
{
   public static void main(String args[])
   {
      Scanner input = new Scanner(System.in);
      //Question 1
      System.out.println("Enter your numbers. (Enter 'Stop' when you're done)");
      int temp = 0;
      String uInput = "";
      char stopper;
      int count = 0;
      double total = 0;
      int a = 0;
      boolean inStop = true;
      for (boolean stop = false; stop != true;)
      {
         int array [] = new int [100];
         if (inStop == true)
         {
            System.out.println("point 5");
            System.out.print("Input: ");
            uInput = input.nextLine(); //reads user input
         }
         try //empty input repeater
         {
            System.out.println("point 1");
            try   //dealing with letters in string instead of numbers
            {
               System.out.println("point 2");

               temp = Integer.parseInt(uInput); //converts string to int
               array[count] = temp;
               count++;
               System.out.println(inStop);
               if (inStop == false) //executes when stop has been reached
               {
                  System.out.println("point 3");
                  int numberArray [] = new int [count]; //fills final array
                  for (int i = 0; i < count; i++)
                  {
                     numberArray[i] = array[i];
                  }
                  for (a = 0; a < numberArray.length; a++)
                  {
                     total = total + numberArray[a];
                  }
                  total = total / a;
                  stop = true; //ends parent loop
               }
            }
            catch (NumberFormatException e) //catches letters in string and checks for stop
            {
               System.out.println("point 4");
               stopper = uInput.charAt(0);
               stopper = Character.toUpperCase(stopper);
               if (stopper == 'S')
               {
                  inStop = false;

                  System.out.println("point 6");
               }
            }
         }
         catch (StringIndexOutOfBoundsException e)
         {
         }
      }
      System.out.println("The average of the values entered is: " + total + ".");
   }
}

The problem is, as you can see there are numerous numbered printouts that indicate (to me) where the program is at the moment. All runs fine, except for point 3. Point 3 for some reason doesn't execute whatsoever. No matter what I do. Now, the problem lies on line 34, temp = Integer.valueOf(uInput); //converts string to int temp = Integer.valueOf(uInput); //converts string to int If I put in a print function directly after that line, that position doesn't print onto the screen. I believe there are no syntax or logic errors with that part, and so does my lecturer, however the code still doesn't execute and the program loops infinitely afterwards. Something is breaking either temp or uInput in that line and we cannot figure out what. I have compiled and ran the code through a different compiler to what I initially used and even tried in the Command Prompt with the same results (so it is not the IDE causing the issue).

Any insight we may have missed would be appreciated. Thanks.

ps: don't knock my lecturer, he didn't write the code, and it isn't that easily readable. He could easily know what the problem is, if not for any error in my explanations or his interpretations of how my program is meant to run.

Answer 1

I think that the reason you are having a problem identifying the issue is because of your code structure.

You have mixed the logic for informing the use, with the logic for reading the inputs, and calculating.

If your main method only deal with informing the user, and relies on another method to calculate the average,and another to read the user's input everything will be easier to read, follow and see that you are parsing "stop" as an int.

public static void main(String[] args) {
    System.out.println("instructions");
    int[] all = readUserInputs();
    double ave = calculateAverage(all);
    System.out.println("message " + ave);
}

private static double calculateAverage(int[] numbers) {
    // I will leave it to you to fill this out
    return yourValue;
}

private static String readUserInputs() {
    Scanner input;// as above
    int[] values; // is an array best? What about a List?
    for (int i = 0; ; i++) {
        String line = input.nextLine();
        if ("stop".equals(line) {
            break;
        }
        //try to parse and put into array/list
    }
    return values;
}

Hopefully you will find this easier to read and work with,I have left a few gaps for you to fill in.