code: public ServiceReference<T> getHighestRankedReference() {
          Iterator<ConcurrentServiceReferenceElement<T>> iterator = elementSet.iterator();
          return iterator.hasNext() ? iterator.next().getReference() : null;
      }
docs: The ConcurrentReferenceSet is ordered by the usual service ranking rules:
  highest service.ranking then lowest (first) service.id.
  
  @return The "first" service reference according to the ranking