We start with this Pair class. import java.util.AbstractList; public class Pair public Pair first -null; second null; public Pair(T first, T second) { this.first first; this.second second; } public T get (int n) { return n ? ? first : n ? 1 ? second : null; } public void set(int n, T t) if (n = 0) first = t; else if (n ?: 1) second-t; private T first; private T second