Let’s learn factorial program in java.

## Factorial program in java

Find the factorial of a number is one of the common java interview question.

Factorial is nothing but the product of all numbers less than or equal to given number. Denoted as n! For example,

Also read – write a java program to check armstrong number

6! = 6 * 5 * 4 * 3 * 2 * 1 = 720 (6! means 6 factorial)

4! = 4 * 3 * 2 * 1 = 24 (4! means 4 factorial)

In finding factorial of a number in java there are many ways. Below are few ways to write factorial program in java.

- factorial program using loop.
- factorial program using recursion.
- factorial program using while loop.
- factorial program using do-while loop.

Now let’s learn to find the factorial of a number using loop in java. Here’s the java program,

public class FactorialDemo { public static void main(String[] args) { int number = 6, factorial = 1; for(int a = 1; a <= number; a++) { factorial = factorial * a; } System.out.println("Factorial of " + number + " is : " + factorial); } }

**Output:**

Factorial of 6 is : 720

**Factorial program using recursion**

Similarly let’s learn to find the factorial of a number using recursion in java. Here’s the java program,

public class FactorialRecursion { public static void main(String[] args) { int factorial = 1; int number = 6; factorial =factorialFunction(number); System.out.println("Factorial of " + number + " is : " + factorial); } static int factorialFunction(int num) { if(num == 0) { return 1; } else { return(num *factorialFunction(num - 1)); } } }

**Output:**

Factorial of 6 is : 720

**Factorial program using while loop**

Also read – fibonacci program in java

Let’s learn to find the factorial of a number using while loop in java. Here’s the java program,

import java.util.Scanner; public class FactorialWhile { public static void main(String[] args) { int number, factorial = 1; Scanner sc = new Scanner(System.in); System.out.println("Please enter a number : "); number = sc.nextInt(); int a = 1; while(a <= number) { factorial = factorial * a; a++; } System.out.println("Factorial of " + number + " is : " + factorial); sc.close(); } }

**Output:**

Please enter a number : 5

Factorial of 6 is : 120

**Factorial program using do while loop**

Meanwhile let’s learn to find the factorial of a number using do-while loop in java. Here’s the java program to find factorial of a number,

import java.util.Scanner; public class FactorialDoWhile { public static void main(String[] args) { int number, factorial = 1; Scanner sc = new Scanner(System.in); System.out.println("Please enter a number : "); number = sc.nextInt(); int a = 1; do { factorial = factorial * a; a++; } while(a <= number); System.out.println("Factorial of " + number + " is : " + factorial); sc.close(); } }

**Output:**

Please enter a number : 7

Factorial of 7 is : 5040