Question

/*
* Author :
* Purpose: This program calculates the factorial of an input number.
(Factorial.java)
*/
import java.util.Scanner;
public class Factorial
{
public static void main(String[] args)
{
Scanner input=new Scanner(System.in);
int number;
Factorial factObj=new Factorial();
//1. Input a positive integer number
do
{
System.out.print("Enter a positive integer number: ");
number=input.nextInt();
if (number<0)
System.out.println("Error: Invalid number.");
}while (number<0);

Answer 1

//2. Calculate and print the factorial of the previous input number
System.out.println(number + "! = " + factObj.findFactorial(number));
}//end of main
public int findFactorial(int number)
{//Purpose: this method uses recursion to compute the factorial of a
positive integer number.
if (number<=1)
return 1;
else
return number*findFactorial(number-1);
}//end of findFactorial method
}//end of Factorial class

Answer 2

a- Explain briefly why it is illegal, in the example above, to call the findFactorial method inside the main method without creating an object of the class Factorial? How can you avoid this step?
b- How many times the findFactorial method will be called if the user input number was 4? And what is the return value of each time it is invoked?

Answer 3

Well a. You cannot call a class within a class(at least I haven't tried it nor do I think it's a good idea) YOu would avoid it by creating the main class public void main(string[] args)
{
factorial f = new factorial();
}

I would assume 4 since that's what you input right? It goes 0 1 1 2 or 1 1 2 3..... Soo depends where you start, didn't check over all fo the code.