*/
  @CanIgnoreReturnValue
  public static <T extends @Nullable Object> boolean addAll(
      Collection<T> addTo, Iterator<? extends T> iterator) {
    checkNotNull(addTo);
    checkNotNull(iterator);
    boolean wasModified = false;
    while (iterator.hasNext()) {
      wasModified |= addTo.add(iterator.next());
    }
    return wasModified;
  }

  /**

                            stream(toAddresses).of(stream -> stream.map(String::trim).forEach(address -> {
                                postcard.addTo(address);
                            }));
                        } else {
                            postcard.addTo(fessConfig.getMailFromAddress());
                            postcard.dryrun();
                        }

                        stream(toAddresses).of(stream -> stream.map(String::trim).forEach(address -> {
                            postcard.addTo(address);
                        }));
                    } else {
                        postcard.addTo(fessConfig.getMailFromAddress());
                        postcard.dryrun();
                    }
                    postcard.setHostname(systemHelper.getHostname());

                        stream(toAddresses).of(stream -> stream.map(String::trim).forEach(address -> {
                            postcard.addTo(address);
                        }));
                    } else {
                        postcard.addTo(fessConfig.getMailFromAddress());
                        postcard.dryrun();
                    }

                postcard.addReplyTo(fessConfig.getMailReturnPath());
                stream(toAddresses).of(stream -> stream.forEach(address -> {
                    postcard.addTo(address);
                }));
                BeanUtil.copyMapToBean(dataMap, postcard);
            });
            saveInfo(messages -> messages.addSuccessSendTestmail(GLOBAL));

   */
  private static <E extends @Nullable Object> boolean addAllImpl(
      Multiset<E> self, AbstractMapBasedMultiset<? extends E> elements) {
    if (elements.isEmpty()) {
      return false;
    }
    elements.addTo(self);
    return true;
  }

  /** An implementation of {@link Multiset#removeAll}. */
  static boolean removeAllImpl(Multiset<?> self, Collection<?> elementsToRemove) {
    Collection<?> collection =