public static interface CollectionsFactory.MarkedSet<E>
extends java.util.Set<E>
CollectionsFactory
.
The reason for this marker interface is that instances can represent a set of payloads,
and may be put into a heterogeneous collection together with single payload objects.
In that scenario, an instanceof check can always distinguish payload objects from marked sets of payload objects,
even if the payload objects happen to inherit from Set
.