Java Program to Find Factorial using For and While loop

We will write three java programs to find factorial of a number. 1) using for loop 2) using while loop 3) finding factorial of a number entered by user. Before going through the program, lets understand what is factorial: Factorial of a number n is denoted as n! and the value of n! is: 1 * 2 * 3 * … (n-1) * n

The same logic we have implemented in our programs using loops. To understand these programs you should have a basic knowledge of following topics of java tutorials:

• For loop in Java
• Java – while loop

Example: Finding factorial using for loop

public class JavaExample {

    public static void main(String[] args) {

    	//We will find the factorial of this number
        int number = 5;
        long fact = 1;
        for(int i = 1; i <= number; i++)
        {
            fact = fact * i;
        }
        System.out.println("Factorial of "+number+" is: "+fact);
    }
}

Output:

Factorial of 5 is: 120

Example 2: Finding Factorial using while loop

public class JavaExample {

    public static void main(String[] args) {

    	//We will find the factorial of this number
        int number = 5;
        long fact = 1;
        int i = 1;
        while(i<=number)
        {
            fact = fact * i;
            i++;
        }
        System.out.println("Factorial of "+number+" is: "+fact);
    }
}

Output:

Factorial of 5 is: 120

Example 3: Finding factorial of a number entered by user

Program finds the factorial of input number using while loop.

import java.util.Scanner;
public class JavaExample {

    public static void main(String[] args) {

    	//We will find the factorial of this number
        int number;
        System.out.println("Enter the number: ");
        Scanner scanner = new Scanner(System.in);
        number = scanner.nextInt();
        scanner.close();
        long fact = 1;
        int i = 1;
        while(i<=number)
        {
            fact = fact * i;
            i++;
        }
        System.out.println("Factorial of "+number+" is: "+fact);
    }
}

Output:

Enter the number: 
6
Factorial of 6 is: 720