Implementation of two approaches to calculate N prime numbers using Java 8 Streams (based on Chapter 6 proposal of Java 8 in Action)

Primes.java

package primes;

import org.openjdk.jmh.annotations.Benchmark;

import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.Properties;
import java.util.stream.IntStream;

/**
 * Based on Chapter 6 of Java 8 in Action
 * @author Miguel Gamboa
 *         created on 16-05-2016
 */
public class Primes {
    /*==================================================
      ==================================================*/
    private static boolean isPrime(int n) {
        int root = (int) Math.sqrt(n);
        return IntStream
                .rangeClosed(2, root)
                .noneMatch(div -> n%div == 0);
    }
    private static List<Integer> primes(int max) {
        return IntStream
                .range(2, max)
                .filter(Primes::isPrime)
                .collect(ArrayList::new, ArrayList::add, ArrayList::addAll);
    }

    /*==================================================
      ==================================================*/

    private static boolean isPrimeOpt(List<Integer> primes, int n) {
        int root = (int) Math.sqrt(n);
        return takeWhile(primes, root)
                .stream()
                .noneMatch(div -> n%div == 0);
    }

    private static List<Integer> takeWhile(List<Integer> src, int max) {
        int i;
        for(i = 0; i < src.size() && src.get(i) <= max; i++) {}
        return src.subList(0, i);
    }

    private static List<Integer> primesOpt(int max) {
        ArrayList<Integer> res = new ArrayList<>();
        return IntStream
                .range(2, max)
                .filter(n -> Primes.isPrimeOpt(res, n))
                .collect(() -> res, ArrayList::add, (l1, l2) -> {});
    }

    @Benchmark
    public int testPrimes() {
        return primes(10_000).size();
    }

    @Benchmark    
    public int testPrimesOpt() {
        return primesOpt(10_000).size();
    }
}