Java Program to find factorial of number in Java - Example Tutorial

How to find the factorial of a number in Java in both recursive and iterative ways is a common Java interview question mostly asked at the fresher level. It’s not just popular in Java interviews but also in other programming languages like C or C++. It's also famous  In our last article we have seen how to check if a number is prime or not and in this Java programming tutorial, we will see a simple Java program to find the factorial of a number in Java by using recursion and iteration. The same program can also be used to print factorial of any number or print a range of factorial as well.


Let’s talk about logic, the factorial of a number is calculated by formula number*(number -1) till zero and since the value of factorial zero is 1, it acts as a base case in the recursive version of the factorial method. 

The logic to find the factorial of a number is encapsulated inside the factorial(int number) and fact(int number) methods.

This Java programming tutorial is in next with my earlier tutorial for beginners like Java Program to reverse String in Java with recursion, Java program to free memory in java and recently how to read and write to a text file in Java, etc if you haven’t read them you may find them interesting and useful.

How to find factorial of a number in Java using recursion and iteration :

In this section, we will see a complete code example of a Java program to calculate the factorial of a number in both recursive and iterative ways. 

If you look closely you will find that the recursive solution of calculating factorial is much easier to write and pretty intuitive to read as it represents formula number*(number -1). 

Any way recursion should only be limited for educational purposes as it is always subject to stack overflow error if recursion is too deep. 

Calculating factorial of a number is also a good programming question to exercise for anyone who is just started learning to program. 

Anyway here is an example of Java program to find factorial of a number :

/**
 * Simple Java program to find the factorial of a number using recursion and iteration.
 * Iteration will use for loop while recursion will call method itself
 */
public class FactorialInJava{

    public static void main(String args[]) {
     
      //finding factorial of a number in Java using recursion - Example
      System.out.println("factorial of 5 using recursion in Java is: " + factorial(5));
     
      //finding factorial of a number in Java using Iteration - Example
       System.out.println("factorial of 6 using iteration in Java is: " + fact(6));
    }
 
 
    /*
     * Java program example to find factorial of a number using recursion
     * @return factorial of a number
     */
    public static int factorial(int number){      
        //base case
        if(number == 0){
            return 1;
        }
        return number*factorial(number -1); //is this tail-recursion?
    }
 
    /*
     * Java program example to calculate factorial using while loop or iteration
     * @return factorial of a number
     */
 
    public static int fact(int number){
        int result = 1;
        while(number != 0){
            result = result*number;
            number--;
        }
     
        return result;
    }
}

Output:
 factorial of 5 using recursion in Java is: 120
 factorial of 6 using iteration in Java is: 720

That's all on how to calculate or find the factorial of a number in Java. Both iterative and recursive versions of factorial can be used to calculate factorials but beware of StackOverFlowError if a larger number is passed to the recursive version of the factorial method in Java.

Now is the quiz time, what is the time and space complexity of this solution? how slow or fast your program become in order to calculate factorial of larger numbers and how can you solve that problem so that your program remains fast?