Iteration order of HashSet

Question

If every object added to a java.util.HashSet implements Object.equals() and Object.hashCode() in a deterministic fashion, is the iteration order over the HashSet guaranteed

Answer 1

Never ever make assumptions about the iteration order of anything you put into a HashSet because its contract explicitly says that you can't count on it in any way. Use LinkedHashSet if you want to maintain insertion order or TreeSet if you want to maintain a natural sorting order.