Prime Factorization Program in Java

Question

I am working on a prime factorization program implemented in Java. The goal is to find the largest prime factor of 600851475143 (Project Euler problem 3). I think I have most of it done, but I am getting a few errors. Also my logic seems to be off, in particular the method that I have set up for checking to see if a number is prime.

public class PrimeFactor {

    public static void main(String[] args) {
        int count = 0;
        for (int i = 0; i < Math.sqrt(600851475143L); i++) {
            if (Prime(i) && i % Math.sqrt(600851475143L) == 0) {
                count = i;
                System.out.println(count);
            }
        }
    }

    public static boolean Prime(int n) {
        boolean isPrime = false;
        // A number is prime iff it is divisible by 1 and itself only
        if (n % n == 0 && n % 1 == 0) {
            isPrime = true;
        }
        return isPrime;
    }
}

Edit

public class PrimeFactor {

    public static void main(String[] args) {
        for (int i = 2; i <= 600851475143L; i++) {
            if (isPrime(i) == true) {
                System.out.println(i);
            }
        }
    }

    public static boolean isPrime(int number) {
        if (number == 1) return false;
        if (number == 2) return true;
        if (number % 2 == 0) return false;
        for (int i = 3; i <= number; i++) {
            if (number % i == 0) return false;
        }
        return true;
    }
}

Answer 1

Why make it so complicated? You don't need do anything like isPrime(). Divide it's least divisor(prime) and do the loop from this prime. Here is my simple code :

public class PrimeFactor {

    public static int largestPrimeFactor(long number) {
        int i;

        for (i = 2; i <= number; i++) {
            if (number % i == 0) {
                number /= i;
                i--;
            }
        }

        return i;
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        System.out.println(largestPrimeFactor(13195));
        System.out.println(largestPrimeFactor(600851475143L));
    }
}