if (predecessors != null) {
      checkState(predecessors.remove(node));
    }
    return node;
  }

  @Override
  public N removeOutEdge(E edge) {
    N node = super.removeOutEdge(edge);
    Multiset<N> successors = getReference(successorsReference);
    if (successors != null) {
      checkState(successors.remove(node));
    }
    return node;
  }

      newDelegate.add(element(i));
    }
    this.table = newDelegate;
    this.entries = null;
    this.elements = null;
    incrementModCount();
    return newDelegate;
  }

  @VisibleForTesting
  boolean isUsingHashFloodingResistance() {
    return delegateOrNull() != null;
  }

  /** Stores the hash table mask as the number of bits needed to represent an index. */

   *
   * @throws NullPointerException if the element is null
   * @since 6.0 (source-compatible since 2.0)
   */
  public static <E> ImmutableMultiset<E> of(E e1) {
    return copyFromElements(e1);
  }

  /**
   * Returns an immutable multiset containing the given elements, in order.
   *
   * @throws NullPointerException if any element is null
   * @since 6.0 (source-compatible since 2.0)
   */

@GwtCompatible
final class CollectPreconditions {

  static void checkEntryNotNull(@Nullable Object key, @Nullable Object value) {
    if (key == null) {
      throw new NullPointerException("null key in entry: null=" + value);
    } else if (value == null) {
      throw new NullPointerException("null value in entry: " + key + "=null");
    }
  }

  @CanIgnoreReturnValue
  static int checkNonnegative(int value, String name) {
    if (value < 0) {

  public void testOffer_nullSupported() {
    assertTrue("offer(null) should return true", getQueue().offer(null));
    expectAdded((E) null);
  }

  @CollectionFeature.Require(value = SUPPORTS_ADD, absent = ALLOWS_NULL_VALUES)
  public void testOffer_nullUnsupported() {
    assertThrows(NullPointerException.class, () -> getQueue().offer(null));
    expectUnchanged();

   *
   * @return {@code first} if it is non-null; otherwise {@code second} if it is non-null
   * @throws NullPointerException if both {@code first} and {@code second} are null
   * @since 18.0 (since 3.0 as {@code Objects.firstNonNull}).
   */
  public static <T> T firstNonNull(@Nullable T first, @Nullable T second) {
    if (first != null) {
      return first;
    }
    if (second != null) {
      return second;
    }

        final Pair<T1, T2> other = (Pair<T1, T2>) obj;
        if (first == null) {
            if (other.first != null) {
                return false;
            }
        } else if (!first.equals(other.first)) {
            return false;
        }
        if (second == null) {
            if (other.second != null) {
                return false;
            }

                }));
    expectReplacement(entry(getKeyForNullValue(), v3()));
  }

  @MapFeature.Require({SUPPORTS_PUT, ALLOWS_NULL_KEYS})
  public void testMergeAbsentNullKey() {
    assertEquals(
        "Map.merge(null, value, function) should return value",
        v3(),
        getMap()
            .merge(
                null,
                v3(),

        assertEquals(0L, MemoryUtil.sizeOf(new Object[0]));

        // Array with null elements
        assertEquals(0L, MemoryUtil.sizeOf(new String[] { null, null }));

        // Mixed content array
        assertEquals(84L, MemoryUtil.sizeOf(new Object[] { "test", 123, null }));

        // Nested arrays

      Preconditions.checkNotNull(runnable, "Runnable was null.");
      Preconditions.checkNotNull(executor, "Executor was null.");

      synchronized (this) {
        if (!executed) {
          RunnableExecutorPair newTail = new RunnableExecutorPair(runnable, executor);
          if (head == null) {
            head = newTail;
            tail = newTail;
          } else {