public void testAddAtIndexConcurrentWithIteration() {
    assertThrows(
        ConcurrentModificationException.class,
        () -> {
          Iterator<E> iterator = collection.iterator();
          getList().add(0, e3());
          iterator.next();
        });
  }

  @ListFeature.Require(absent = SUPPORTS_ADD_WITH_INDEX)
  public void testAddAtIndex_unsupportedNotPresent() {

  private Dispatcher dispatcher;

  public void testPerThreadQueuedDispatcher() {
    dispatcher = Dispatcher.perThreadDispatchQueue();
    dispatcher.dispatch(1, integerSubscribers.iterator());

    assertThat(dispatchedSubscribers)
        .containsExactly(
            i1,
            i2,
            i3, // Integer subscribers are dispatched to first.
            s1,

  }

  final Set<K> unmodifiableKeySet() {
    return new AbstractSet<K>() {
      @Override
      public UnmodifiableIterator<K> iterator() {
        Iterator<Entry<K, V>> entryIterator = backingMap.entrySet().iterator();

        return new UnmodifiableIterator<K>() {
          @Override
          public boolean hasNext() {
            return entryIterator.hasNext();
          }

import org.jspecify.annotations.Nullable;

/**
 * This class provides a skeletal implementation of the {@code Iterator} interface for sequences
 * whose next element can always be derived from the previous element. Null elements are not
 * supported, nor is the {@link #remove()} method.
 *
 * <p>Example:
 *
 * {@snippet :
 * Iterator<Integer> powersOfTwo =
 *     new AbstractSequentialIterator<Integer>(1) {

import java.util.ListIterator;
import org.jspecify.annotations.Nullable;

/**
 * A list iterator which forwards all its method calls to another list iterator. Subclasses should
 * override one or more methods to modify the behavior of the backing iterator as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *

interface GraphConnections<N, V> {

  Set<N> adjacentNodes();

  Set<N> predecessors();

  Set<N> successors();

  /**
   * Returns an iterator over the incident edges.
   *
   * @param thisNode The node that this all of the connections in this class are connected to.
   */
  Iterator<EndpointPair<N>> incidentEdgeIterator(N thisNode);

  /**

                // care performance for List that the most frequent pattern
                final Object first = coll instanceof List<?> ? ((List<?>) coll).get(0) : coll.iterator().next();
                if (first instanceof Entity) {
                    data.register(key, coll.stream().map(BeanUtil::copyBeanToNewMap).collect(Collectors.toList()));
                    return;
                }

    TreeMultimap<@Nullable String, @Nullable Integer> multimap = createPopulate();
    Iterator<Entry<String, Collection<Integer>>> iterator = multimap.asMap().entrySet().iterator();
    Entry<String, Collection<Integer>> entry = iterator.next();
    assertEquals(null, entry.getKey());
    assertThat(entry.getValue()).containsExactly(7, 3, 1);
    entry = iterator.next();
    assertEquals("tree", entry.getKey());

          queue.remove();
        }
      }
    }

    private static final class Event {
      private final Object event;
      private final Iterator<Subscriber> subscribers;

      private Event(Object event, Iterator<Subscriber> subscribers) {
        this.event = event;
        this.subscribers = subscribers;
      }
    }
  }

  }

  public void testIteratorPastEndException() {
    MinMaxPriorityQueue<Integer> mmHeap = MinMaxPriorityQueue.create();
    mmHeap.addAll(Lists.newArrayList(1, 2));
    Iterator<Integer> it = mmHeap.iterator();
    assertTrue("Iterator has reached end prematurely", it.hasNext());
    it.next();
    it.next();
    assertThrows(NoSuchElementException.class, () -> it.next());
  }