Java Program to Find Factorial Using Recursion

Recursion is a powerful programming concept where a function calls itself to solve a problem. Factorial is one of the most common examples used to understand recursion in Java.

In this tutorial, we will create a Java program to calculate the factorial of a number using recursion.

By the end of this guide, you will understand how recursive functions work in Java.

Concept Overview

The factorial of a number n is defined as n × (n-1) × (n-2) × ... × 1.

In recursion, we define the problem in terms of a smaller version of itself.

Base case: factorial of 0 or 1 is 1.

Program

import java.util.Scanner;

public class FactorialRecursion {

    static long factorial(int n) {
        if (n == 0 || n == 1)
            return 1;
        else
            return n * factorial(n - 1);
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.print("Enter a number: ");
        int num = sc.nextInt();

        long result = factorial(num);

        System.out.println("Factorial of " + num + " is: " + result);
    }
}

Output

Enter a number: 5
Factorial of 5 is: 120

Detailed Explanation

The program defines a recursive function factorial() that calls itself with a smaller value each time.

The base condition ensures that the recursion stops when n becomes 0 or 1.

Each recursive call multiplies the current number with the result of factorial(n-1).

The main() method takes user input and calls the recursive function.

Example Walkthrough

Let us consider n = 5.

The recursion expands as: 5 × 4 × 3 × 2 × 1 = 120.

Applications

Recursion is widely used in tree traversal, searching algorithms, dynamic programming, and mathematical computations.

Advantages of This Approach

This program helps beginners understand recursion clearly.

It simplifies problems by breaking them into smaller subproblems.

Limitations

Recursion can lead to stack overflow for large inputs.

Improvements You Can Make

You can add memoization to optimize repeated calls.

You can also compare recursive and iterative approaches.

This Java program builds a strong understanding of recursion and problem decomposition, which are essential in advanced programming.