In Appendix A, answers to Chapter 3, question 2, the answer is D but at the end of the explanation it says it's E.
2. D. The answer needs to implement Map because you are dealing with key/value pairs per the unique string text. You can eliminate A, C, E, and F immediately. ArrayList and Vector are Lists. HashSet and TreeSet are Sets. Now it is between HashMap and TreeMap. Since the question talks about ordering, you need the TreeMap. Therefore, the answer is E.