private static <T> int _lengthRecursive(List<T> list, int i) {
        if (list.isEmpty()) {
            return i;
        }
        return _lengthRecursive(list.subList(1, list.size()), ++i);
    }
Find the number of elements of a list
java8/src/main/java/com/shekhargulati/ninetynine_problems/_01_lists/P04.java