Nth Prime
Prime number is an age old problem. I am trying to solve it via streams.
class PrimeCalculator { public int nth(int nth) { if (nth <= 0) throw new IllegalArgumentException(); // Will skip the nth - 1 // 2 to n-1 return IntStream.iterate(2, i -> i + 1).filter(PrimeCalculator::isPrime).skip(nth - 1).findFirst().getAsInt(); } public static boolean isPrime(int x) { // till half of x return IntStream.rangeClosed(2, (int) (x/2) ).dropWhile(i -> x % i != 0).findFirst().isEmpty(); } } Explanation # public int nth(int nth) { if (nth <= 0) throw new IllegalArgumentException(); // Will skip the nth - 1 // 2 to n-1 return IntStream.iterate(2, i -> i + 1).filter(PrimeCalculator::isPrime).skip(nth - 1).findFirst().getAsInt(); } The method nth(int) allows you to return the nth prime starting at 2, 3, 5....