The Sieve of Eratosthenes in Java

SieveOfEratosthenes.java

import java.util.List;
import static java.util.stream.Collectors.toList;
import java.util.stream.IntStream;
import static java.util.stream.IntStream.rangeClosed;

public class SieveOfEratosthenes {

    static boolean isPrime(final int candidate) {
	if (candidate < 2) {
	    return false;
	}
	final int sqrt = (int) Math.sqrt(candidate);
	for (int i = 2; i <= sqrt; i++) {
	    if (candidate % i == 0) {
		return false;
	    }
	}
	return true;
    }

    static int nextPrime(final int previous) {
	if (previous < 2) {
	    return 2;
	}
	for (int candidate = previous + 1; candidate > 0; candidate++) {
	    if (isPrime(candidate)) {
		return candidate;
	    }
	}
	throw new RuntimeException("failed to get a prime number greater than " + previous);
    }

    public static void main(final String[] args) {
	if (args.length == 0) {
	    return;
	}
	final int max = Integer.parseInt(args[0]);
	if (max < 2) {
	    return;
	}
	final List<Integer> candidates = rangeClosed(2, max).boxed().collect(toList());
	for (int current = 2; true; ) {
	    final int prime = current;
	    if (prime > candidates.get(candidates.size() - 1)) {
		break;
	    }
	    candidates.removeIf(n -> n > prime && n % prime == 0);
	    try {
		current = nextPrime(current);
	    } catch (final RuntimeException re) {
		break;
	    }
	}
	for (int n : candidates) {
	    if (!isPrime(n)) {
		System.out.println("not a prime numer: " + n);
	    }
	}
	System.out.println(candidates);
    }
}