Transforming a while loop to a stream in Java 8

Question

As an exercise I'm converting some old code to functional streams. I don't know much about streams. It seems like it should be simple to convert this code, but I haven't had much luck. The method starts at a given integer, passes it to isPrime, which returns true if it's prime. and then hands off the new(next) prime number to be printed. If isPrime is false i is incremented and we check the next integer.

private static int nextPrime(final int number) {
    int i = number + 1;

    while (!isPrime(i)) {
        i++;
    }

    return i;
}

Answer 1

I see no reason to use a Stream for this other than to take advantage of parallelism (if the primes happen to be very far apart, but this won't be true within int bounds, so there's essentially no benefit).

You can iterate over an IntStream of ascending integers (starting from number + 1) and filter only the prime numbers. When one is inevitably found, you can return the first.

private static int nextPrime(final int number) {
    return IntStream.iterate(number + 1, i -> i + 1)
                    .filter(Test::isPrime)
                    .findFirst()
                    .getAsInt();
}

Note: The class that I used to test this is called Test, as seen by the method reference. You should change that to your class name.