@Override
      public T next() {
        if (++this.returned == 1) return getFirst();
        else if (this.returned == 2) return getSecond();
        else throw new IllegalAccessError("this.returned=" + this.returned);
      }
Return the second element stored in the pair.
hbase-common/src/main/java/org/apache/hadoop/hbase/util/PairOfSameType.java