TwoPrimes

public class TwoPrimes {

    public static void main(String[] args) {
        int N = 10000000;

        boolean[] isprime = new boolean[N];

        for (int i = 2; i < N; i++)
            isprime[i] = true;

        // determine primes < N using Sieve of Eratosthenes
        for (int i = 2; i * i < N; i++) {
            if (isprime[i]) {
                for (int j = i; i * j < N; j++)
                    isprime[i * j] = false;
            }
        }

        // count primes
        int primes = 0;
        for (int i = 2; i < N; i++)
            if (isprime[i])
                primes++;

        // store primes in list
        int[] list = new int[primes];
        int n = 0;
        for (int i = 0; i < N; i++)
            if (isprime[i])
                list[n++] = i;

        // check if N can be expressed as sum of two primes

        for (int i = 4; i <= 10000000; i += 2) {
            int currNum = i;
            int left = 0, right = list.length - 1;
            while (left <= right && right > 0) {
                if (list[left] + list[right] == currNum)
                    break;
                else if (list[left] + list[right] < currNum)
                    left++;
                else
                    right--;
            }
            if (list[left] + list[right] == currNum)
                System.out.println(currNum + " = " + list[left] + " + "
                        + list[right]);
            else
                System.out.println(currNum
                        + " not expressible as sum of two primes");
        }
    }
}