Two java.util.Iterators to the same collection: do they have to return elements in the same order?
api, collections, contract, iterator, java
Solution
No they are not.
"There are no guarantees concerning the order in which the elements are returned (unless this collection is an instance of some class that provides a guarantee)."
See the Collection#iterator api contract.
That includes from one iterator to the next (as it doesn't say anything about requiring that).
Also consider that something could have changed in the underlying collection between getting those two iterators! Something added or removed.
Problem
This is more of a theoretical question. If I have an arbitrary collection `c` that isn't ordered and I obtain two `java.util.Iterator`s by calling `c.iterator()` twice, do both iterators have to return `c`'s elements in the same order? I mean, in practice they probably always will, but are they forced to do so by contract? Thanks, Jan