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:
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