Factorial Number In Java

We are back to this Java questions and programming question series. In this blog post, we are going to cover a very important programming question: How will you find the factorial number? In mathematics, we have seen factorial numbers. So now we will find out:

• How will you find out the factorial number?
• What are the different ways to find out the factorial number?
• What are the different conditions you will handle?

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It’s an evergreen interview question whether you are going for a Java or an automation interview.

So, what do you mean by factorial number? The Factorial of a positive integer (number) is the sum of the multiplication of all the integers smaller than that positive integer.

A factorial number of 3 means I just need to write like this: 3 x 2 x 1 is equal to 6. Right? If I ask you what a factorial of 4 is, factorial 4 is like this: 4 x 3 x 2 x 1.

Note: The factorial of 1 is 1, and the Factorial of 0 (zero) is 1.

Factorials of Numbers 1 to 10 Table

Here is the List Of factorial numbers from 1 to 10.

Factorial of a Number!	Expansion	Value
1!	1	1
2!	2 × 1	2
3!	3 × 2 × 1	6
4!	4 × 3 × 2 × 1	24
5!	5 × 4 × 3 × 2 × 1	120
6!	6 × 5 × 4 × 3 × 2 × 1	720
7!	7 × 6 × 5 × 4 × 3 × 2 × 1	5,040
8!	8 × 7 × 6 × 5 × 4 × 3 × 2 × 1	40,320
9!	9 × 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1	362,880
10!	10 × 9 ×8 × 7 × 6 × 5 ×4 × 3 × 2 × 1	3,628,800

What are the different ways to find out the factorial number?

There are two ways to find the factorial of a number. We can find factorial with the help of recursive and non-recursive methods.

Factorial Number Without Using Recursive Method

package com.softwaretestingo.interviewprograms;
import java.util.Scanner;
public class FactorialNumberEx1 
{
	// Find Factorial Using Recursive Method
	public static int factoral(int num)
	{
		int fact=1;
		if(num==0)
			return 1;
		for(int i=1;i<=num;i++)
		{
			fact=fact*i;
		}
		return fact;
	}
	public static void main(String[] args) 
	{
		// fact (3)=3x2x1
		Scanner sc=new Scanner(System.in);
		System.out.println("Enter A Number To Find out Factorial: ");
		int number=sc.nextInt();
		System.out.println("The Factorial of "+number+ " is =  "+factoral(number));		
	}
}

Output:

Enter A Number To Find out Factorial: 5
The Factorial of 5 is =  120

Factorial Number Using Recursive Method

If you’re working with Java, you may come across situations where a method needs to call itself. In these cases, the method is known as a recursive method, and the process is called recursion.

package com.softwaretestingo.interviewprograms;
import java.util.Scanner;
public class FactorialNumberEx2 
{
	// Find Factorial Using Recursive Method
	public static int factoral(int num)
	{
		if (num==0)
			return 1;
		else
			return (num * factoral(num-1));		
	}
	public static void main(String[] args) 
	{
		// fact (3)=3x2x1
		Scanner sc=new Scanner(System.in);
		System.out.println("Enter A Number To Find out Factorial: ");
		int number=sc.nextInt();
		System.out.println("The Factorial of "+number+ " is =  "+factoral(number));		
	}
}

Output:

Enter A Number To Find out Factorial: 8
The Factorial of 8 is =  40320