ParallelTest Java

ParallelTest

import java.util.stream.IntStream;

public class ParallelTest {

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


        long startTime = System.currentTimeMillis();

        ParallelTest pt = new ParallelTest();
        long primes = pt.countPrimes(max);
        System.out.println(primes);

        long stopTime = System.currentTimeMillis();

        System.out.println(stopTime - startTime);
    }

    private long countPrimes(final int max) {

        return IntStream
                .range(1, max)
                .parallel()
                .filter(this::isPrime)
                .count();

    }

    private boolean isPrime(final long n) {
        if (n < 2) return false;
        if (n == 2 || n == 3) return true;
        if (n % 2 == 0 || n % 3 == 0) return false;
        long sqrtN = (long) Math.sqrt(n) + 1;
        for (long i = 6L; i <= sqrtN; i += 6) {
            if (n % (i - 1) == 0 || n % (i + 1) == 0) return false;
        }
        return true;
    }

}