code: @Override
      public boolean addAll(Collection<? extends E> c) {
          for (E e : c) {
              discardingOffer(e);
          }
          return !c.isEmpty();
      }
docs: Offer the given elements to the {@linkplain java.util.concurrent.BlockingQueue}
  removing elements if necessary (ie if the queue is full).
  
  @param c the element to add to the queue
  @return {$code true} if the given elements collection is not empty