Iterator<E> iterator = collection.iterator();
    Object element = iterator.next();
    // If it's an Entry, it may become invalid once it's removed from the Map. Copy it.
    if (element instanceof Entry) {
      Entry<?, ?> entry = (Entry<?, ?>) element;
      element = mapEntry(entry.getKey(), entry.getValue());
    }
    assertTrue(collection.contains(element)); // sanity check
    iterator.remove();

      Comparator<? super E> comparator, E... elements) {
    checkNotNull(elements);
    switch (elements.length) {
      case 0:
        return emptySet(comparator);
      default:
        SortedSet<E> delegate = new TreeSet<E>(comparator);
        for (E element : elements) {
          checkNotNull(element);
          delegate.add(element);
        }

/**
 * Split a list of elements into nearly even sublist. If an element is too large, largeElementSplitFunction will be used to split the large element into several smaller pieces;
 * if some elements are too small, they will be aggregated by smallElementAggregateFunction.
 *
 * @param list the list to split, must be ordered by size desc
 * @param toIntFunction the function used to map the element to its "size"

   *
   * @param length the length of the array
   */
  public AtomicDoubleArray(int length) {
    this.longs = new AtomicLongArray(length);
  }

  /**
   * Creates a new {@code AtomicDoubleArray} with the same length as, and all elements copied from,
   * the given array.
   *
   * @param array the array to copy elements from

  /**
   * A collector that converts a stream of zero or one elements to an {@code Optional}.
   *
   * @throws IllegalArgumentException if the stream consists of two or more elements.
   * @throws NullPointerException if any element in the stream is {@code null}.
   * @return {@code Optional.of(onlyElement)} if the stream has exactly one element (must not be
   *     {@code null}) and returns {@code Optional.empty()} if it has none.

    Iterator<E> iterator = collection.iterator();
    Object element = iterator.next();
    // If it's an Entry, it may become invalid once it's removed from the Map. Copy it.
    if (element instanceof Entry) {
      Entry<?, ?> entry = (Entry<?, ?>) element;
      element = mapEntry(entry.getKey(), entry.getValue());
    }
    assertTrue(collection.contains(element)); // sanity check
    iterator.remove();

  }

  protected void expectMissingKeys(K... elements) {
    for (K element : elements) {
      assertFalse("Should not contain key " + element, getMap().containsKey(element));
    }
  }

  protected void expectMissingValues(V... elements) {
    for (V element : elements) {
      assertFalse("Should not contain value " + element, getMap().containsValue(element));
    }
  }

  /**

    @DisplayName("Should handle various element counts")
    @ValueSource(ints = { 1, 2, 5, 10, 20, 50, 100 })
    void testJoinWithVariousElementCounts(int count) {
        CharSequence[] elements = new CharSequence[count];
        for (int i = 0; i < count; i++) {
            elements[i] = String.valueOf(i);
        }
        String result = StringUtil.join(",", elements);

        // Verify result contains all elements

    multimap.put(2, "foo");
    for (String element : elements) {
      multimap.put(3, element);
    }
  }

  static void populateMultimapForKeySet(Multimap<String, Integer> multimap, String[] elements) {
    for (String element : elements) {
      multimap.put(element, 2);
      multimap.put(element, 3);
    }
  }

  /**
   * Indicates that a collection disallows certain elements (other than {@code null}, whose validity
   * as an element is indicated by the presence or absence of {@link #ALLOWS_NULL_VALUES}). From the
   * documentation for {@link Collection}:
   *
   * <blockquote>
   *
   * "Some collection implementations have restrictions on the elements that they may contain. For