为什么我的代码无法运行？

Question

I have this code:

import java.util.Scanner;  

public class PositiveNegative   {    public static void main(String[] args)    {
      int numbers, plus = 0, minus = 0;
      int count = 0;
      double total = 0;

      Scanner scan = new Scanner(System.in);
      System.out.print("Enter an integer (0 to quit): ");
      numbers = scan.nextInt();

      while(numbers != 0)
      {
         total += numbers;
         if(numbers > 0)
            plus++;
         if(numbers < 0)
            minus++;   
      }
      System.out.println("The number of positives is: " +plus);
      System.out.println("The number of negatives is: " +minus);
      System.out.println("The number of total is: " +total);    
    }
}

The problem with is that I try to run it and type the numbers but it does nothing. I want it so that when you type 0 it stops taking numbers and starts processing the code. What should I do?

Answer 1

You need to update numbers or your loop will run for ever. And I recommend using braces (and an else ). Something like,

System.out.print("Enter an integer (0 to quit): ");
numbers = scan.nextInt();
while (numbers != 0) {
    total += numbers;
    if (numbers > 0) {
        plus++;
    } else if (numbers < 0) {
        minus++;   
    }
    System.out.print("Enter an integer (0 to quit): ");
    numbers = scan.nextInt();
}

Alternatively, you could use a do-while loop. Then you only need one copy of the prompt. Like,

do {
    System.out.print("Enter an integer (0 to quit): ");
    numbers = scan.nextInt();
    total += numbers;
    if (numbers > 0) {
        plus++;
    } else if (numbers < 0) {
        minus++;   
    }
} while (numbers != 0);

Answer 2

Try this:

    import java.util.Scanner;

public class PositiveNegative {
    public static void main(String[] args) {
        int numbers = 0, plus = 0, minus = 0;
        double total = 0;
        do{
            Scanner scan = new Scanner(System.in);
            System.out.print("Enter an integer (0 to quit): ");
            numbers = Integer.valueOf(scan.nextLine());
            total += numbers;
            if (numbers > 0)
                plus++;
            if (numbers < 0)
                minus++;
        }
        while (numbers != 0);
        System.out.println("The number of positives is: " + plus);
        System.out.println("The number of negatives is: " + minus);
        System.out.println("The number of total is: " + total);
    }
}

Put your Scanner in the while loop so that everytime loop start it will ask for User input.

Answer 3

You have to modify numbers each time to make it work in your while .

So, in your existing code, just comment out numbers = scan.nextInt(); and use below--

// numbers = scan.nextInt();  //comment out this call

    while ((numbers = scan.nextInt()) != 0) {
    ....

this will give you desired output--

Enter an integer (0 to quit): 9
4
-9
1
0
The number of positives is: 3
The number of negatives is: 1
The number of total is: 5.0