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When I run the program in eclipse, I cannot break out of the while loop after the user enters a certain integer to move on and actually calculate the number of divisors it has and print it out with counts.

   /*
 * This program reads a positive integer from the user. 
 * It counts how many divisors that number has, and then it prints the result.
 * Also prints out a ' . ' for every 1000000 numbers it tests. 
 */

import java.util.Scanner;

public class forloopTEST1 {


public static void main(String[] args) {

    Scanner input = new Scanner(System.in);

    int N; //A positive integer entered by the user.
           //  Divisor of this number will be counted.

    int testDivisor;    // A number between 1 and N that is a possible divisor of N.

    int divisorCount;   // A number of divisors between 1 to N that have been found.

    int numberTested;   // Used to count how many possible divisors of N have been tested, When # reached 1000000
                        //a period is output and the value of numberTested is reset to 0.

    /* Get a positive integer from the user */

    while (true) {
        System.out.println("Enter a positive integer: ");
        N = input.nextInt();

        if (N < 0)
            break;
        System.out.println("That number is not positive. Please try again.: ");

    }

    /* Count divisor, printing ' . ' after every 1000000 tests. */

    divisorCount = 0;
    numberTested = 0;

    for (testDivisor = 1; testDivisor <= N; testDivisor++) {
    if ( N % testDivisor == 0 );
        divisorCount++;
        numberTested++;

    if (numberTested == 1000000) {
        System.out.println(".");
        numberTested = 0;

    }


    }

}

}
Shaz
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1 Answers1

10

Look at your if statement:

if (N < 0)
    break;

You're breaking out of the loop if the user enters a negative number - but you want to break out if they enter a positive number:

if (N > 0)
    break;

(I haven't looked at the rest of the code, but that's what's wrong with the while loop.)

Alternatively, you could use:

int N = input.nextInt();
while (N < 0) {
    System.out.println("That number is not positive. Please try again.: ");
    N = input.nextInt();
}

Additionally, I'd recommend:

  • Always using braces for if statements etc, even if the body is a single statement
  • Declaring local variables at the point of first use, rather than declaring the all at the top of the method
  • Following Java naming conventions (N should either be n, or ideally a more descriptive name)
Jon Skeet
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  • Sorry, it doesn't work! I mean it does break from the while loop but it doesn't go on to calculate the divisors in the next section after the while loop. I would really appreciated a lot if you could take a quick scan at the rest of the code and help me identify what I'm doing wrong. Thanks p.s still learning :) – Shaz Dec 28 '13 at 10:34
  • @Shaz: Your question was about the `while` loop - it's best to ask one thing per post. Now that you've got past that bit, I suggest you ask a new question about the division part - and for that, you can get rid of the user input, and just pick an example which doesn't work. – Jon Skeet Dec 28 '13 at 10:42