I haven't personally used it, but the org.openntf.domino.helpers.DocumentSorter
class looks like what you're talking about. You'd use it like:
DocumentSorter sorter = new DocumentSorter(docColl, Arrays.asList("LastName"));
DocumentCollection sorted = sorter.sort();
You could probably then get reverse ordering by using:
List<Document> docs = new ArrayList<>(sorted);
Collections.reverse(docs);
That said, I think it's likely that performance wouldn't necessarily be better than what you're seeing without it - the sorting loads each document in the collection to read the fields and has no special acceleration from Domino.