# Factorial program in Java using recursion

In this tutorial we are going to learn writing java program to calculate the Factorial of a given number using recursion.

You can also check : Factorial program in java using Iterative method.

## What is Recursion?

Recursion is a method that defines something in terms of itself, which means it is a process in which a function calls itself again and again till condition satisfy.

A complete function can be split down into various sub-parts in recursion. It makes code look simple and compact. It is also defined as the process of defining a program or problem in terms of itself. Let’s have a look at the simple diagram that explains the working of recursion.

## Our logic of Factorial program using recursion

• Our program will take an integer input from the user which should be a whole number.
• If the number input is negative then print ‘The factorial can’t be calculated’.
• Then use fact(num) user-defined recursive function that will return the factorial of the given number.

Let’s understand through a diagram how our recursive function will work on input 7.

## Algorithm to calculate factorial using recursion

Step 1: Start

Step 2: Create a user-define function ‘fact(num)’ which take an integer as an parameter and return num*fact(num-1).

Step 3: Create a variable num.

Step 4: Take an integer input from the user and store it into num variable.

Step 5: Pass the variable num as the parameter of user-defined function ‘func’ and print the result returned by the function.

Step 6: Stop

Output 1

Explanation

Output 2

Explanation