The factorial of a positive number n is given by:
factorial of n (n!) = 1 * 2 * 3 * 4 * ... * n
The factorial of a negative number doesn't exist. And the factorial of 0 is 1.
You will learn to find the factorial of a number using recursion in this example. Visit this page to learn, how you can find the factorial of a number using loop.
Example: Factorial of a Number Using Recursion
public class Factorial {
public static void main(String[] args) {
int num = 6;
long factorial = multiplyNumbers(num);
System.out.println("Factorial of " + num + " = " + factorial);
}
public static long multiplyNumbers(int num)
{
if (num >= 1)
return num * multiplyNumbers(num - 1);
else
return 1;
}
}
Output
Factorial of 6 = 720
Initially, the multiplyNumbers() is called from the main() function with 6 passed as an argument.
Since 6 is greater than or equal to 1, 6 is multiplied to the result of multiplyNumbers() where 5 (num -1) is passed. Since, it is called from the same function, it is a recursive call.
In each recursive call, the value of argument num is decreased by 1 until num reaches less than 1.
When the value of num is less than 1, there is no recursive call.
And each recursive calls returns giving us:
6 * 5 * 4 * 3 * 2 * 1 * 1 (for 0) = 720