throw PermittedMetaException.UOE;
        }
      } else if (stackWithLastReturnedElementAtTop == null) {
        throw PermittedMetaException.ISE;
      }
    }

    private List<E> getElements() {
      List<E> elements = new ArrayList<>();
      Helpers.addAll(elements, previousElements);
      Helpers.addAll(elements, Helpers.reverse(nextElements));
      return elements;
    }
  }

          throw PermittedMetaException.UOE;
        }
      } else if (stackWithLastReturnedElementAtTop == null) {
        throw PermittedMetaException.ISE;
      }
    }

    private List<E> getElements() {
      List<E> elements = new ArrayList<>();
      Helpers.addAll(elements, previousElements);
      Helpers.addAll(elements, Helpers.reverse(nextElements));
      return elements;
    }
  }

    return new Multisets.AbstractEntry<E>() {
      @Override
      @ParametricNullness
      public E getElement() {
        return baseEntry.getElement();
      }

      @Override
      public int getCount() {
        int result = baseEntry.getCount();
        if (result == 0) {
          return count(getElement());
        } else {
          return result;
        }
      }
    };
  }

          () -> new ToOptionalState<>(null),
          (state, o) -> state.add((o == null) ? NULL_PLACEHOLDER : o),
          ToOptionalState::combine,
          state -> {
            Object result = state.getElement();
            return (result == NULL_PLACEHOLDER) ? null : result;
          },
          Collector.Characteristics.UNORDERED);

  /**

          () -> new ToOptionalState<>(null),
          (state, o) -> state.add((o == null) ? NULL_PLACEHOLDER : o),
          ToOptionalState::combine,
          state -> {
            Object result = state.getElement();
            return (result == NULL_PLACEHOLDER) ? null : result;
          },
          Collector.Characteristics.UNORDERED);

  /**

     * represent the same element and count. That is, two entries {@code a} and {@code b} are equal
     * if:
     *
     * {@snippet :
     * Objects.equals(a.getElement(), b.getElement()) && a.getCount() == b.getCount()
     * }
     */
    @Override
    // TODO(kevinb): check this wrt TreeMultiset?
    boolean equals(@Nullable Object o);

    /**
     * {@inheritDoc}

     * represent the same element and count. That is, two entries {@code a} and {@code b} are equal
     * if:
     *
     * {@snippet :
     * Objects.equals(a.getElement(), b.getElement()) && a.getCount() == b.getCount()
     * }
     */
    @Override
    // TODO(kevinb): check this wrt TreeMultiset?
    boolean equals(@Nullable Object o);

    /**
     * {@inheritDoc}

    CollectorTester.of(
            ImmutableMultiset.<Multiset.Entry<String>, String>toImmutableMultiset(
                Multiset.Entry::getElement, Multiset.Entry::getCount),
            equivalence)
        .expectCollects(ImmutableMultiset.of())
        .expectCollects(
            ImmutableMultiset.of("a", "a", "b", "c", "c", "c"),

        Multiset.Entry<K> transform(Map.Entry<K, Collection<V>> backingEntry) {
          return new Multisets.AbstractEntry<K>() {
            @Override
            @ParametricNullness
            public K getElement() {
              return backingEntry.getKey();
            }

            @Override
            public int getCount() {
              return backingEntry.getValue().size();
            }

        Multiset.Entry<K> transform(Map.Entry<K, Collection<V>> backingEntry) {
          return new Multisets.AbstractEntry<K>() {
            @Override
            @ParametricNullness
            public K getElement() {
              return backingEntry.getKey();
            }

            @Override
            public int getCount() {
              return backingEntry.getValue().size();
            }