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Thread: Factorial program

  1. #1
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    Default Factorial program

    Hello everyone.

    I'm working on some exercises and I'm having some problems with a method. I want to create a method to calculate the Factorial of an int number. I already wrote code that asks the user to input an int number and it calculates the Factorial, and it works fine (ie: if I input 5 it outputs
    5! = 120
    , as it should. Here's the code:

    import java.util.Scanner;
     
    public class Factorial1
    {
        public static void main(String[] args)
        {
            Scanner input = new Scanner(System.in);
            int number;
            int total = 1;
     
            System.out.print("Enter positive int number: ");
                number = input.nextInt();
     
            while(number < 0)
            {
                System.out.print("Enter positive int number: ");
                number = input.nextInt();
            }
     
            for(int i = number; i > 0; i--)
                total *= i;
     
            System.out.printf("%d! = %d", number, total);
        }
    }

    Now I want to make a method to re-use this code in other programs and I wrote this program:

    public class TestClass
    {
        public static void main(String[] args)
        {
            System.out.print(factorial(5));
        }
     
        public static int factorial(int x)
        {
            int total = 0;
     
            for(int i = x; i > 0; i--)
                total *= i;
     
            return total;
        }
    }

    But when I run this program it outputs 0 instead of 120. I don't have the slightest idea of what is wrong with this code as it compiles just fine but doesn't work as intended.

    Any help will be very appreciated, and thanks in advance!

    Ricardo
    Last edited by rchirino; March 2nd, 2014 at 11:51 AM.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Factorial program

    it outputs 0
    What is the value of total when
    total *= i;
    is executed?
    If you don't understand my answer, don't ignore it, ask a question.

  3. The Following User Says Thank You to Norm For This Useful Post:

    rchirino (March 2nd, 2014)

  4. #3
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    Default Re: Factorial program

    Oh... Fixed. Thanks Norm. Gotta pay more attention.

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