public class Sieve {

    public static void main(String[] args) {
//         assume here is a check of command line arg
        long bound = 10_000_000;
        Set<Long> primes = new LinkedHashSet<>();
        long startTime = System.currentTimeMillis();
        for (long start = 3; start <= bound; start += 2) {

            long root = (long) Math.sqrt(start);

            boolean isPrime = true;
            for (Long l : primes) {
                if (l > root) break;
                if (start % l == 0) {
                    isPrime = false;
                    break;
                }
            }
            if (isPrime)
                primes.add(start);

        }

        primes.add(2L);

        System.out.println(primes);
        System.out.println("Duration: " + (System.currentTimeMillis() - startTime) / 1000.0 + " seconds");
        System.out.println("Primes found: " + primes.size());
    }

}