(multiset1, multiset2) -> {
          multiset1.addAll(multiset2);
          return multiset1;
        },
        (Multiset<E> multiset) -> ImmutableMultiset.copyFromEntries(multiset.entrySet()));
  }

  static <T extends @Nullable Object, E extends @Nullable Object, M extends Multiset<E>>
      Collector<T, ?, M> toMultiset(
          Function<? super T, E> elementFunction,

    Entry<E>[] entries = (Entry<E>[]) multiset.entrySet().toArray((Entry<E>[]) new Entry<?>[0]);
    Arrays.sort(entries, DecreasingCount.INSTANCE);
    return ImmutableMultiset.copyFromEntries(asList(entries));
  }

  private static final class DecreasingCount implements Comparator<Entry<?>> {
    static final Comparator<Entry<?>> INSTANCE = new DecreasingCount();

    @Override

    Entry<E>[] entries = (Entry<E>[]) multiset.entrySet().toArray((Entry<E>[]) new Entry<?>[0]);
    Arrays.sort(entries, DecreasingCount.INSTANCE);
    return ImmutableMultiset.copyFromEntries(asList(entries));
  }

  private static final class DecreasingCount implements Comparator<Entry<?>> {
    static final Comparator<Entry<?>> INSTANCE = new DecreasingCount();

    @Override