Set interface and natural ordering [nonsensical interview test] [duplicate]

Question

By a chance it happened to me twice that I got the same Java question during a job interview Java test. For me it seems like a nonsense. It goes something like this:

Which of this collections would you use if you needed a collection with no duplicates and with natural ordering?

1. java.util.List
2. java.util.Map
3. java.util.Set
4. java.util.Collection

The closest answer would be Set. But as far as I know these interfaces, with exception of List do not define any ordering in their contract but it is the matter of the implementing classes to have or not to have defined ordering.

Was I right in pointing out in the test that the question is wrong?

Answer 1

The first major clue is "no duplicates." A mathematical set contains only unique items, which means no duplicates, so you are correct here.

In terms of ordering, perhaps the interviewer was looking for you to expand upon your answer. Just as a "Set" extends a "Collection" (in Java), there are more specific types of "Sets" possible in Java. See: HashSet, TreeSet, LinkedHashSet. For example, TreeSet is inherited from SortedSet interface.

However, it is most definitely true that a Java set does not provide any ordering. Frankly, I think this is a poorly worded question and you were right to point out the lack in precision.