private String toStringHelper(Node<T> currentNode, String result) {
		if (currentNode.getHead() == null) {
			return result;
		} else if (currentNode.getTail() != null) {
			String r = currentNode.getHead().toString();
			r = result + r;
			return toStringHelper(currentNode.getTail(), r) + " ";
		}
		return result + currentNode.getHead().toString();
	}