Java Program to Find Factorial of a Number Recursively

20 Jan, 2022
Factorial of a number n is defined as a product of all positive descending integers, Factorial of n is denoted by n!. Factorial can be calculated using the following recursive formula where the recursive call is made to a multiplicity of all the numbers lesser than the number for which the factorial is computed as the formula to calculate factorial is as follows:
n! = n * [(n-1)!] 
i.e factorial of n (n!) = n * (n-1) * ......* 3 * 2* 1
Note: Factorial of 0 is 1 
Illustration:
Input      : 5!
Processing : 5*4*3*2*1
Output     : 120  
Input      : 6!
Processing : 6*5*4*3*2*1
Output     : 720 
Example 1:
Java
// Java Program to Find Factorial of a Number// where N>=0 is currently N>1 // Importing input output classesimport java.io.*;// importing utility classesimport java.util.*; // Main classclass GFG {     // Method 1    // To calculate factorial    static int factorial(int n)    {         // Handling base case        // iIf value of n=1 or n=0, it returns 1        if (n == 0 || n == 1)            return 1;         // Generic case        // Otherwise we do n*(n-1)!        return n * factorial(n - 1);    }     // Method 2    // main driver method    public static void main(String[] args)    {         // Calling method 1 to compute factorial and        // storing the result into a variable        int ans = factorial(5);         // Print and display the factorial of number        // customly passed as an argument        System.out.println("Factorial of 5 is :" + ans);    }}
Factorial of 5 is :120
Output explanation:
Initially, the factorial() is called from the main method with 5 passed as an argument. Since 5 is greater than or equal to 1, 5 is multiplied to the result of factorial( ) where 4 (n -1) is passed. Since, it is called from the same method, it is a recursive call. In each recursive call, the value of argument n is decreased by 1 until n reaches less than 1. When the value of n is less than or equal to 1, then there is no recursive call and at last, it returns 1.
Example 2: 
Java
// Java Program to Find Factorial of a Number// where N>=0 is currently N=1 // Importing input output classesimport java.io.*;// Importing utility classesimport java.util.*; // Main classclass GFG {     // Method 1    // To calculate factorial    static int factorial(int n)    {         // Handling base case        // If value of n=1 or n=0 we return 1        if (n == 0 || n == 1)            return 1;         // Generic case computation math        // Otherwise we do n*(n-1)!        return n * factorial(n - 1);    }     // Method 2    // Main driver method    public static void main(String[] args)    {         // Calling Method 1 and        // storing the result into variable        int ans1 = factorial(0);        int ans2 = factorial(1);         // Print and display the factorial of 0        System.out.println("Factorial of 0 is : " + ans1);         // Similarly, Print and display the factorial of 1        System.out.println("Factorial of 1 is : " + ans2);    }}
Factorial of 0 is : 1
Factorial of 1 is : 1
Output explanation:
Initially, the factorial( ) is called from the main method with 6 passed as an argument. In each recursive call, the value of argument n is decreased by 1 until n reaches less than 1. For 1! decreased argument been passed is 0! as a small recursion call to be computed. As discussed above factorial of zero is 1. Hence, the small answer returned is 1, which later is multiplied to 1 itself so do result 1 as an output. Hence, it is stated when the value of n is less than or equal to 0 then no recursion call is computed as we will encounter negative integers over which factorial is not allowed to be computed.
 
gabaa406
anikaseth98
sumitgumber28
Picked
Java
Java Programs
Java
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.
List Interface in Java with Examples
Different ways of Reading a text file in Java
Constructors in Java
Strings in Java
HashMap containsKey() Method in Java
Java Programming Examples
Convert Double to Integer in Java
Implementing a Linked List in Java using Class
Factory method design pattern in Java
Java Program to Remove Duplicate Elements From the Array