code: public static <E> Optional<E> maybeOne(E[] array) {
          return new MaybeOneElement<E>().apply(new ArrayIterator<>(array));
      }
docs: Yields the only element if found, nothing otherwise.
  
  @param <E> the array element type
  @param array the array that will be consumed
  @throws IllegalStateException if the iterator contains more than one
  element
  @return just the element or nothing