无法获得此“ Fatorial”程序的预期输出？

Question

My name is sam and i'm a beginner in java.I have actually tried this "factorial" program on my own and i can't see whats going wrong with logic....I'm not getting the expected output,can anyone tell me why? Thanks in advance,grt day to all the users :)

Factorial:

import java.util.*;

class factorial {

    public static void main(String[] args) {

        int i;

        System.out.println("enter a number");

        Scanner in=new Scanner(System.in);

        int n=in.nextInt();

        int x=n;

        while(x!=0) {
            x=x*(n-1);
            n--;
        }

        System.out.println(x);

    }

}

When I enter (for example) 5, I expect to get the factoial of 5 (120). Instead, I get zero. This happens for all inputs.

Answer 1

If you really want to learn, start running code in your head, line by line, such as with:

int n = 5;

int x = n;
while (x != 0) {
    x = x * (n - 1);
    n--;
}

Start with a sheet of paper thus:

  x  |  n
-----+-----
     |
     |
     |
     |

and, as you "execute" each line, write down the new values. Do that and it will be immediately obvious where your problem lies. It will also make you a better developer.

Please do not look at the rest of this answer until you have done that, and tried to fix it.

---

Once you've understood the problem and (hopefully) fixed it, compare what you have with the solution below:

int n = 5;          // input value.

int x = 1;          // initial accumulator set to identity (n * 1 = n).
while (n != 0) {    // use all values from n down to 1 (inclusive).
    x = x * n;      // multiply accumulator by that value.
    n--;            // get next value.
}

Answer 2

int x=n;

    while(x!=0) {
        x=x*(n-1);
        n--;
    }

The result will be 0 because your loop will work for ever until x=0, x get the value of 0 in your loop when n becomes 0, try n!=0 in while loop condition

Answer 3

You simply need to change the While loop condition to while(n!=1), because in your case when n becomes 1 then x=x*(n-1); will result in x being multiplied with 0.

Answer 4

Try out this code:

 public static void main(String[] args)

{

    int i;

    System.out.println("enter a number");

    Scanner in=new Scanner(System.in);

    int n=in.nextInt();

    int x=1;

    while(n!=0)

    {

        x*=(n);
        n--;

    }

    System.out.println(x);

}

Your while loop is multiplying your answer by 0 when n=1, and we all know what multiplying by 0 does.

EDIT: My bad, edited code.