Frankly I'm shocked that deduplicateTree is two orders of magnitude slower than deduplicateGreybeard, despite having asymptotically better-or-equal performance (TreeSet runtime is O(output log output), whereas sorting an array is O(input log input)). I'd say that perhaps boxing the integers is slowing the algorithm down, but deduplicateGreybeardCollections has only a <3x performance hit rather than >100x. Is the problem due to allocating large amounts of internal memory and branching heavily (binary trees as opposed to B-trees), or less predictable/vectorizable code execution than array traversal, or virtual comparison dispatch slower than `items.sort(Comparator.naturalOrder())`, or some TreeSet-specific slowdown?