code: public Object getItemXFromEnd(int distanceFromEnd) {
          if ((end - (distanceFromEnd)) < start) {
              throw new IllegalArgumentException(distanceFromEnd
                  + " extends before the start of this suffix: ");
          }
          return sequence.getItem(end - distanceFromEnd);
      }
docs: Retrieves the item the given distance from the end of the suffix.
  
  @param distanceFromEnd The distance from the end.
  @return The item the given distance from the end.
  @throws IllegalArgumentException if the distance from end is greater than the length of the
  suffix.