* if:
     *
     * {@snippet :
     * Objects.equals(a.getElement(), b.getElement())
     *     && a.getCount() == b.getCount()
     * }
     */
    @Override
    // TODO(kevinb): check this wrt TreeMultiset?
    boolean equals(@Nullable Object o);

    /**
     * {@inheritDoc}
     *
     * <p>The hash code of a multiset entry for element {@code element} and count {@code count} is

  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.
  public final Optional<@NonNull E> last() {
    // Iterables#getLast was inlined here so we don't have to throw/catch a NSEE

    // TODO(kevinb): Support a concurrently modified collection?
    Iterable<E> iterable = getDelegate();
    if (iterable instanceof List) {
      List<E> list = (List<E>) iterable;
      if (list.isEmpty()) {

   *     such index exists.
   */
  public static int indexOf(int[] array, int target) {
    return indexOf(array, target, 0, array.length);
  }

  // TODO(kevinb): consider making this public
  private static int indexOf(int[] array, int target, int start, int end) {
    for (int i = start; i < end; i++) {
      if (array[i] == target) {
        return i;
      }
    }

  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.
  public final Optional<@NonNull E> last() {
    // Iterables#getLast was inlined here so we don't have to throw/catch a NSEE

    // TODO(kevinb): Support a concurrently modified collection?
    Iterable<E> iterable = getDelegate();
    if (iterable instanceof List) {
      List<E> list = (List<E>) iterable;
      if (list.isEmpty()) {

     * if:
     *
     * {@snippet :
     * Objects.equals(a.getElement(), b.getElement())
     *     && a.getCount() == b.getCount()
     * }
     */
    @Override
    // TODO(kevinb): check this wrt TreeMultiset?
    boolean equals(@Nullable Object o);

    /**
     * {@inheritDoc}
     *
     * <p>The hash code of a multiset entry for element {@code element} and count {@code count} is

   *     such index exists.
   */
  public static int indexOf(long[] array, long target) {
    return indexOf(array, target, 0, array.length);
  }

  // TODO(kevinb): consider making this public
  private static int indexOf(long[] array, long target, int start, int end) {
    for (int i = start; i < end; i++) {
      if (array[i] == target) {
        return i;
      }
    }

   *     such index exists.
   */
  public static int indexOf(char[] array, char target) {
    return indexOf(array, target, 0, array.length);
  }

  // TODO(kevinb): consider making this public
  private static int indexOf(char[] array, char target, int start, int end) {
    for (int i = start; i < end; i++) {
      if (array[i] == target) {
        return i;
      }
    }

   *     such index exists.
   */
  public static int indexOf(float[] array, float target) {
    return indexOf(array, target, 0, array.length);
  }

  // TODO(kevinb): consider making this public
  private static int indexOf(float[] array, float target, int start, int end) {
    for (int i = start; i < end; i++) {
      if (array[i] == target) {
        return i;
      }
    }

   *     such index exists.
   */
  public static int indexOf(double[] array, double target) {
    return indexOf(array, target, 0, array.length);
  }

  // TODO(kevinb): consider making this public
  private static int indexOf(double[] array, double target, int start, int end) {
    for (int i = start; i < end; i++) {
      if (array[i] == target) {
        return i;
      }
    }

 *
 * @since 2.0
 */
@DoNotMock("Use ImmutableList.of or another implementation")
@GwtCompatible
@SuppressWarnings("serial") // we're overriding default serialization
// TODO(kevinb): I think we should push everything down to "BaseImmutableCollection" or something,
// just to do everything we can to emphasize the "practically an interface" nature of this class.