return ImmutableSet.copyOf(elements);
    }
  }

  public static class DegeneratedImmutableSetGenerator extends TestStringSetGenerator {
    @SuppressWarnings("DistinctVarargsChecker") // deliberately testing deduplication
    @Override
    protected Set<String> create(String[] elements) {
      return ImmutableSet.of(elements[0], elements[0]);
    }
  }

      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);
        }

        final Entry entry = getEntry(index);
        final E oldValue = entry.element;
        entry.element = element;
        return oldValue;
    }

    /**
     * Returns the position of the element.
     *
     * @param element the element
     * @return the position
     */
    public int indexOf(final E element) {
        int index = 0;
        if (element == null) {

    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();

    }

    /**
     * Adds an element to the beginning of a sequenced collection.
     *
     * @param <E> the element type
     * @param collection the sequenced collection
     * @param element the element to add
     * @since Java 21
     */
    public static <E> void addFirst(final SequencedCollection<E> collection, final E element) {
        collection.addFirst(element);
    }

    /**

   * Returns a fluent iterable containing the specified elements in order.
   *
   * <p><b>{@code Stream} equivalent:</b> {@link java.util.stream.Stream#of(Object[])
   * Stream.of(T...)}.
   *
   * @since 20.0
   */
  public static <E extends @Nullable Object> FluentIterable<E> of(
      @ParametricNullness E element, E... elements) {
    return from(Lists.asList(element, elements));
  }

  /**

   * Returns a fluent iterable containing the specified elements in order.
   *
   * <p><b>{@code Stream} equivalent:</b> {@link java.util.stream.Stream#of(Object[])
   * Stream.of(T...)}.
   *
   * @since 20.0
   */
  public static <E extends @Nullable Object> FluentIterable<E> of(
      @ParametricNullness E element, E... elements) {
    return from(Lists.asList(element, elements));
  }

  /**

 * elements FIFO (first-in-first-out). The head of the queue is that element that has been
 * on the queue the longest time. The tail of the queue is that element that has been on
 * the queue the shortest time. New elements are inserted at the tail of the queue, and the queue
 * retrieval operations obtain elements at the head of the queue.
 *

     * {@code list.size()} if there is no such element.
     *
     * <p>Note that the return value will be {@code >= 0} if and only if there is an element of the
     * list that compares as equal to the key.
     *
     * <p>This is equivalent to the behavior of {@link java.util.Collections#binarySearch(List,

  }

  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));
    }
  }

  /**