The Factorial of number is denoted by **n!** , is the product/multiplication of all positive integers less than or equal to **n.**

Where n is always a non-negative number and The value of **0!** is 1, according to the convention for an empty product.

## Example :

**0!**=1=**1**

**1!**=1=**1**

**5!**=5 * 4 * 3 * 2 * 1=**120**

**12!**=12 * 11 * 10 * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 * 1=**479001600**

Below are examples to calculate factorial of a Number. I have consider all the cases like calculation of big factorial number by loop and also through recursion.

## Factorial of a Number by using Java code loop.

class Factorial { public static void main(String args[]) { int n, c, fact = 1; System.out.println("Enter an integer to calculate it's factorial"); Scanner in = new Scanner(System.in); n = in.nextInt(); if (n < 0) System.out.println("Number should be non-negative."); else { for (c = 1; c <= n; c++) fact = fact * c; System.out.println("Factorial of " + n + " is = " + fact); } } }

## Factorial of a Big Integer Number by using loop

If calculation of number is too big which cross the Integer limit then use **BigInteger** instead if **Integer**.

class Factorial { public static void main(String args[]) { int n, c; BigInteger inc = new BigInteger("1"); BigInteger fact = new BigInteger("1"); Scanner input = new Scanner(System.in); System.out.println("Input an integer"); n = input.nextInt(); for (c = 1; c <= n; c++) { fact = fact.multiply(inc); inc = inc.add(BigInteger.ONE); } System.out.println(n + "! = " + fact); } }

## Factorial of Integer Number by using Java Recursion.

import java.util.Scanner; public class FactorialByRecursion { public static void main(String[] args) { int n; System.out.println("Enter an integer to calculate it's factorial"); Scanner in = new Scanner(System.in); n = in.nextInt(); if (n < 0) System.out.println("Number should be non-negative."); else { System.out.println("Factorial of " + n + " is = " + factorial(n)); } } private static int factorial(int num) { //Recursion Terminating condition if 0 terminate with value 1 if(num==0) return 1; else return num*factorial(num-1); } }

## More Info

For more Algorithms and Java Programing Test questions and sample code follow below links

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