public interface Pair<T1,T2>
extends java.io.Serializable, java.lang.Comparable<Pair<T1,T2>>
A Pair is a container that holds two related objects. It is the equivalent of an Association in Smalltalk, or an
implementation of Map.Entry in the JDK.
An instance of this interface can be created by calling Tuples.pair(Object, Object) or Tuples.twin(Object, Object).