@Override
  public int hashCode() {
    if (first == null) {
      return (second == null) ? 0 : second.hashCode() + 1;
    } else if (second == null) {
      return first.hashCode() + 2;
    } else {
      return first.hashCode() * 17 + second.hashCode();
    }
  }
Return the second element stored in the pair.
hbase-common/src/main/java/org/apache/hadoop/hbase/util/Pair.java