Entry<E> result = wrapEntry(requireNonNull(current));
        prevEntry = result;
        if (current.succ() == header) {
          current = null;
        } else {
          current = current.succ();
        }
        return result;
      }

      @Override
      public void remove() {
        checkState(prevEntry != null, "no calls to next() since the last call to remove()");