Problem 3 - Project Euler in Java by Jane Ullah

Problem3.java

/**
 * 
 * @author Jane Ullah
 * @purpose Problem 3 - Project Euler
 * @date   12/19/2011
 *	
 */

public static void main(String[] args) {

	long primeNumber = 600851475143L, divisor = 0L, primeDivisor = 0L;
	long controller = (long) Math.floor(Math.sqrt(primeNumber));
	
	for (long i = 2L; i <= controller; i++ )	{
		//Catching all divisors of the number
		if (primeNumber % i == 0)	{
			divisor = i;
			//Checking for prime divisors.
			if (divisorTest(divisor))	{
				primeDivisor = divisor;
			}
		}
	}
	System.out.println("Largest Prime Divisor: " + primeDivisor);
}

//Method to test the 'prime-ness' of the divisors
private static boolean divisorTest(long number){
	long j = 0;
	if (number == 2) { return true; }
	for (j = 0; (j <= number/2) && ( !((number % (j+2)) == 0 )) ; j++);
	return (j >= number/2);
}