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

// AKS
public boolean isPrimeV3(int number) {
        switch (number) {
            case 1:
                return false;
            case 2:
            case 3:
                return true;
        }

        if ((number & 1) == 0) return false; // even numbers
        if ((number % 3) == 0) return false;

        int i = 5; // increases by j
        int j = 2; // alternating between 2 and 4
        while (i * i <= number) {
            if (number % i == 0)
                return false;
            i += j;
            j = 6 - j;
        }

        return true;
    }