In this program, you’ll learn to find and display the factorial of a number using a recursive function in Java.
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.
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
