Prime numbers

Prime.java

/**
 * Utility method for prime numbers.
 **/
public class Prime {
  public static boolean isPrime(long n) {
    return n > 1 && LongStream.rangeClosed(2, (long) Math.sqrt(n)).noneMatch(divisor -> n % divisor == 0);
  }
  public static long countPrimes(int max) {
    return LongStream.range(1, max).filter(Prime::isPrime).count();
  }
  
  public static long countPrimesInParallel(int max) {
    return LongStream.range(1, max).filter(Prime::isPrime).count();
  }
}