Hashset vs Treeset?

Question

I've always loved trees, that nice `O(n*log(n))` and the tidiness of them. However, every software engineer I've ever known has asked me pointedly why I would use a `TreeSet`. From a CS background, I don't think it matters all that much which you use, and I don't care to mess around with hash functions and buckets (in the case of `Java`). In which cases should I use a `HashSet` over a `TreeSet`?

Answer 1

Elements in a TreeSet are ordered according to their natural ordering (see java.lang.Comparable interface). Optionally, they can be ordered with a java.util.Comparator provided to the TreeSet. Elements in a HashSet are unordered. Checkout the Javadoc for the iterator() methods on both classes to learn more.