//package numeric;
/**
* This class calculates the Greatest Common
* Divisor of two numbers passed into the program
* through command line arguments.
*
* @author Alex Laird
* @version 1.0
* File: GCD.java
* Created: Sep 2008
*/
public class GCD
{
/**
* Returns the Greatest Common Divisor of two
* numbers that are passed into the method.
*
* @param a the first integer for comparison.
* @param b the second integer for comparison.
* @throws NegativeNumberException if the input given is negative.
* @returns the Greatest Common Divisor.
*/
public static int gcd(int a, int b) throws Exception
{
// throw an exception if the input is negative
if(a < 0 || b < 0)
{
throw new Exception("The user has entered a "
+ "negative number.");
}
if(b == 0)
return a;
else
return gcd(b, a % b);
}
/**
* The main method from which the program executes;
* it handles all I/O and method execution.
*
* @param args Arguments received from the command line (two numbers).
* @param gcd The calcuated Greatest Common Divisor of args[0] and args [1].
*/
public static void main(String[] args)
{
// ensure the user only enters two arguments
if(args.length == 2)
{
// ensure the users arguments are numbers
try
{
// calculate gcd
int gcd = gcd(Integer.parseInt(args[0]),
Integer.parseInt(args[1]));
System.out.println("The Greatest Common Divisor of "
+ args[0] + " and " + args[1] + " is "
+ gcd + ".");
}
catch(NumberFormatException c)
{
System.out.println("Your arguments must be in "
+ "the form of integers when "
+ "running the program (ex. "
+ "enter 'java numeric.GCD "
+ "50 30').");
}
catch(Exception c)
{
// used only in GUI
}
}
else
{
System.out.println("Enter two numbers as arguments "
+ "when running the program (ex. "
+ "enter 'java numeric.GCD 50 30').");
}
}
}