}

    @Override
    public boolean isEmpty() {
      synchronized (mutex) {
        return delegate().isEmpty();
      }
    }

    @Override
    public Iterator<E> iterator() {
      return delegate().iterator(); // manually synchronized
    }

    @Override
    public Spliterator<E> spliterator() {
      synchronized (mutex) {
        return delegate().spliterator();
      }
    }

 * elementsToInsert}, the elements to be passed to {@code set()} and {@code add()} calls; {@code
 * features}, the features supported by the iterator; and {@code expectedElements}, the elements the
 * iterator should return in order.
 *
 * <p>The items in {@code elementsToInsert} will be repeated if {@code steps} is larger than the
 * number of provided elements.
 *
 * @author Chris Povirk
 */

import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.Iterator;
import java.util.NoSuchElementException;
import org.jspecify.annotations.Nullable;

/**
 * Note this class is a copy of {@link com.google.common.collect.AbstractIterator} (for dependency
 * reasons).
 */
@GwtCompatible
abstract class AbstractIterator<T extends @Nullable Object> implements Iterator<T> {
  private State state = State.NOT_READY;

If you don't know, check the [Async: *"In a hurry?"*](../../async.md#in-a-hurry) section about `async` and `await` in the docs.

///

## Integrated with OpenAPI { #integrated-with-openapi }

All the request declarations, validations and requirements of your dependencies (and sub-dependencies) will be integrated in the same OpenAPI schema.

So, the interactive docs will have all the information from these dependencies too:

    Multiset<Multiset<?>> multiset = HashMultiset.create();
    multiset.add(multiset, 2);
    Multiset<Multiset<?>> copy = SerializableTester.reserialize(multiset);
    assertEquals(2, copy.size());
    assertThat(copy.iterator().next()).isSameInstanceAs(copy);
  }

  @J2ktIncompatible
  @GwtIncompatible // Only used by @GwtIncompatible code
  private static class MultisetHolder implements Serializable {

    int copyIntoArray(@Nullable Object[] dst, int offset) {
      return entries.copyIntoArray(dst, offset);
    }

    @Override
    public UnmodifiableIterator<Entry<K, V>> iterator() {
      return entries.iterator();
    }

    @Override
    @GwtIncompatible // Spliterator
    public Spliterator<Entry<K, V>> spliterator() {
      return entries.spliteratorWithCharacteristics(SPLITERATOR_CHARACTERISTICS);

    map.putInstance(String.class, "test");
    assertEquals(TypeToken.of(String.class), map.entrySet().iterator().next().getKey());
    assertEquals("test", map.entrySet().iterator().next().getValue());
    assertThrows(
        UnsupportedOperationException.class, () -> map.entrySet().iterator().next().setValue(1));
  }

  public void testEntrySetToArrayMutationThrows() {
    map.putInstance(String.class, "test");

TYPE java.lang.Runnable

FIELD com.google.common.base.Converter.reverse
FIELD com.google.common.collect.AbstractBiMap.EntrySet.iterator.$.entry com.google.common.collect.AbstractBiMap.EntrySet.iterator.$.next.$
FIELD com.google.common.collect.AbstractMapBasedMultimap.map
FIELD com.google.common.collect.AbstractMultimap.asMap com.google.common.collect.AbstractMapBasedMultimap.NavigableAsMap

  }

  protected K getKeyForNullValue() {
    return getEntryNullReplaces().getKey();
  }

  private Entry<K, V> getEntryNullReplaces() {
    Iterator<Entry<K, V>> entries = getSampleElements().iterator();
    for (int i = 0; i < getNullLocation(); i++) {
      entries.next();
    }
    return entries.next();
  }

  /**

   * half of that is more awkward to arrange...
   */
  private static <T> Iterable<T> iterable(Collection<T> collection) {
    // return collection::iterator;
    return new Iterable<T>() {
      @Override
      public Iterator<T> iterator() {
        return collection.iterator();
      }
    };
  }

  public void testEquals() {
    new EqualsTester()
        .addEqualityGroup(ImmutableDoubleArray.of())