public List<Integer> primeNumbersTill(int n) {
    return IntStream.rangeClosed(2, n)
      .filter(x -> isPrime(x))
      .boxed()
      .collect(Collectors.toList());
}

private boolean isPrime(int number) {
    return IntStream.rangeClosed(2, (int) (Math.sqrt(number)))
      .allMatch(n -> number % n != 0);
}