import org.jspecify.annotations.Nullable;

/**
 * Implementation of {@link ImmutableMultiset} with zero or more elements.
 *
 * @author Jared Levy
 * @author Louis Wasserman
 */
@GwtCompatible
@SuppressWarnings("serial") // uses writeReplace(), not default serialization
final class RegularImmutableMultiset<E> extends ImmutableMultiset<E> {
  static final RegularImmutableMultiset<Object> EMPTY =

          multiset2.add(elements[i], i + 1);
        }
        return difference(multiset1, multiset2);
      }
    };
  }

  private static final ImmutableMultiset<String> ELEMENTS_TO_FILTER_OUT =
      ImmutableMultiset.of("foobar", "bazfoo", "foobar", "foobar");

  private static final Predicate<String> PREDICATE = not(Predicates.in(ELEMENTS_TO_FILTER_OUT));

    assertEquals(ImmutableSortedMap.of(), ArbitraryInstances.get(ImmutableSortedMap.class));
    assertEquals(ImmutableMultiset.of(), ArbitraryInstances.get(Multiset.class));
    assertEquals(ImmutableMultiset.of(), ArbitraryInstances.get(ImmutableMultiset.class));
    assertTrue(ArbitraryInstances.get(SortedMultiset.class).isEmpty());
    assertEquals(ImmutableMultimap.of(), ArbitraryInstances.get(Multimap.class));

  static <E> Multiset<E> reserializeAndAssertLenient(Multiset<E> original) {
    Multiset<E> copy = reserialize(original);
    assertEquals(original, copy);
    assertTrue(copy instanceof ImmutableMultiset);
    return copy;
  }

  @CanIgnoreReturnValue
  @GwtIncompatible // SerializableTester
  static <E> Collection<E> reserializeAndAssertElementsEqual(Collection<E> original) {

  }

  /**
   * Returns an {@code ImmutableMultiset} containing all of the elements from this fluent iterable.
   *
   * <p><b>{@code Stream} equivalent:</b> {@code ImmutableMultiset.copyOf(stream.iterator())}, or
   * pass {@link ImmutableMultiset#toImmutableMultiset} to {@code stream.collect()}.
   *
   * @throws NullPointerException if any element is null

 * @since 12.0
 */
@GwtIncompatible // hasn't been tested yet
public abstract class ImmutableSortedMultiset<E> extends ImmutableMultiset<E>
    implements SortedMultiset<E> {
  // TODO(lowasser): GWT compatibility

  /**
   * Returns a {@code Collector} that accumulates the input elements into a new {@code
   * ImmutableMultiset}. Elements are sorted by the specified comparator.
   *

          public int add(String element, int occurrences) {
            addCalls.incrementAndGet();
            return super.add(element, occurrences);
          }
        };
    ImmutableMultiset<String> adds =
        new ImmutableMultiset.Builder<String>().addCopies("x", 10).build();
    multiset.addAll(adds);
    assertEquals(1, addCalls.get());
  }

  public void testRemoveUnsupported() {

FIELD com.google.common.collect.AbstractMultiset.entrySet com.google.common.collect.FilteredEntryMultimap.Keys.entrySet.$
FIELD com.google.common.collect.ConcurrentHashMultiset.countMap
FIELD com.google.common.collect.ImmutableMultiset.asList
FIELD com.google.common.collect.ImmutableRangeMap.ranges
FIELD com.google.common.collect.ImmutableRangeSet.ranges
FIELD com.google.common.collect.ImmutableSet.asList

      Collector<Range<E>, ?, ImmutableRangeSet<E>> toImmutableRangeSet() {
    return (Collector) TO_IMMUTABLE_RANGE_SET;
  }

  // Multisets

  static <T extends @Nullable Object, E> Collector<T, ?, ImmutableMultiset<E>> toImmutableMultiset(
      Function<? super T, ? extends E> elementFunction, ToIntFunction<? super T> countFunction) {
    checkNotNull(elementFunction);
    checkNotNull(countFunction);
    return Collector.of(

      Collector<Range<E>, ?, ImmutableRangeSet<E>> toImmutableRangeSet() {
    return (Collector) TO_IMMUTABLE_RANGE_SET;
  }

  // Multisets

  static <T extends @Nullable Object, E> Collector<T, ?, ImmutableMultiset<E>> toImmutableMultiset(
      Function<? super T, ? extends E> elementFunction, ToIntFunction<? super T> countFunction) {
    checkNotNull(elementFunction);
    checkNotNull(countFunction);
    return Collector.of(