package factorial;

import java.util.Scanner;

/**

* This program will print out the factorial of any non-negative

* number that you input into it.

*

* @author Marcus

*

*/

public class Factorial{

/**

* The main method

*

* @param args Command line arguments

*/

public static void main(String[] args){

Scanner input = new Scanner(System.in);

System.out.print("Enter a non-negative integer: ");

//If user does not enter an Integer, we want program to fail gracefully, letting the user know why it terminated

try{

int number = input.nextInt();

//We keep prompting the user until they enter a positive number

while(number < 0){

System.out.println("Your input must be non-negative. Please enter a positive number: ");

number = input.nextInt();

}

//Display the result

System.out.println("The factorial of " + number + " will yield: " + factorial(number));

}catch(Exception e){

System.out.println("Error: You did not enter an integer. Program has terminated.");

}

input.close();

}

/**

* Recursive Factorial Method

*

* @param n The number to factorial

* @return The factorial of the number

*/

public static long factorial(int n){

if(n == 0 || n == 1) return 1;

return n * factorial(n - 1);

}

}