| This is an iterator that walks a pair of collections, returning
matching pairs from the set.
When an element is present in the left set but there is no equal object
in the right set, the pair (leftobj, null) is returned.
When an element is present in the right set but there is no equal object
in the left set, the pair (null, rightobj) is returned.
When an element in one set has an equal element in the other set, the
pair (leftobj, rightobj) is returned.
Note that the phrase "pair is returned" above actually means that the
getLeft and getRight methods on the iterator return those objects; the
pair is "conceptual" rather than a physical Pair instance. |