Validate a user's integer input?

Question

I need to ensure that a user enters a number between 10 and 100. If they do not, I want them to enter a new number. In between the asterisks is where my problem is (I think). Thanks in advance.

import java.util.Scanner;

public class Duplicate 

{

  public static void main(String[] args)

  {

    Scanner input = new Scanner(System.in);

    int[] array = new int[5];

    System.out.println("Enter 5 integers between 10 and 100 (inclusive):");

    for (int i = 0; i < array.length; i++)   

    ****if ((input.nextInt() <= 100) || (input.nextInt() >= 10))

    {

      array[i] = input.nextInt();

    }

    ****else { System.out.print("Please enter a number greater than 9 and less than 101."); }

    for (int i = 0; i < array.length; i++)

      System.out.print(array[i] + ", ");

    System.out.println();

    System.out.println("Unique values are: ");

    for (int i = 0; i < array.length; i++) {

      boolean show = true;

      for (int j = 0; j < i; j++)

        if (array[j] == array[i]) {

          show = false;

          break;

        }

      if (show)

        System.out.print(array[i] + ", ");

    }

  }

}

Please learn how to indent your code. Failing to follow standard guidelines isn't clever. — Chris Dennett
– Chris Dennett, Commented Oct 9, 2011 at 0:40

Mike Samuel · Accepted Answer · 2011-10-09 00:38:36Z

2

if ((input.nextInt() <= 100) || (input.nextInt() >= 10))
  array[i] = input.nextInt();

You are calling nextInt three times which reads the next three integers. So if the user enters 5 then 150, then -1, this will be the same as

if (5 <= 100 || 150 >= 10)
  array[i] = -1;

which succeeds when it should not.

You are also using || (or) instead of && (and) so if the user entered 1 after the problem above is fixed, it would look like

if (1 <= 100 ||/* or */ 1 >= 10)
  array[i] = 1;

which succeeds because 1 <= 100.

Instead, just read one int and use &&.

int userEnteredInt = input.nextInt();
if (10 <= userEnteredInt && userEnteredInt <= 100)
  array[i] = userEnteredInt;

edited Oct 9, 2011 at 0:38

answered Oct 9, 2011 at 0:32

Mike Samuel

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1 Comment

David Over a year ago

Thank you. I had a feeling the or statement might be an issue. I guess I also did not understand how nextInt() was being read. Thanks again.

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