In mathematics, the **factorial** of any non-negative number letâ€™s say X, is denoted by X! , which is equal to the product of all positive integers less than or equal to X. i.e.

Let the non-negative integer be 5, then **factorial** of 5 is denoted by 5! = 5 * 4 * 3 * 2 * 1

From the above example we can now introduce **factorial** general term as:

**N ! = N * ( N â€“ 1 ) !**

**Factorial **of zero (0!) is 1, it is considered as empty product.

Ready to make a **factorial program in java**? Hereâ€™s the code:

import java.util.Scanner; // Scanner class used to take input class Factorial { public static void main (String[] args) { Scanner n = new Scanner(System.in); //'n' as a Scanner class object with "System.in" as constructor argument System.out.print("Enter Number :"); int inputNumber = n.nextInt(); // n.nextInt() function takes integer input int factorialResult = 1; // initialize factorialResult with value 1 while (inputNumber>=0) { if (inputNumber==0) factorialResult = factorialResult * 1; else factorialResult = inputNumber * factorialResult; inputNumber--; } //end loop System.out.println("Factorial is : "+factorialResult); } // end main } // end Factorial class

This program calculates the **factorial** of the given number. Every time loop traverses, it assures that the given number is not less than zero, multiplies each number with its one decrement and store it for the next. Finally the main function ends with displaying the result calculated.

Output is: