code: public String next(String ignoreZone) {
          if (entry == null) return null;
          entry = entry.next;
          if (entry.element.equals(ignoreZone)) {
              return entry.next.element;
          } else {
              return entry.element;
          }
      }
docs: Returns the next zone from the set excluding the given zone which should
  get the request.
  
  @return - the next zone in the iterator. If there are none then null is
  returned.