* Returns a fluent iterable whose iterators traverse first the elements of this fluent iterable,
   * followed by {@code elements}.
   *
   * <p><b>{@code Stream} equivalent:</b> {@code Stream.concat(thisStream, Stream.of(elements))}.
   *
   * @since 18.0
   */
  public final FluentIterable<E> append(E... elements) {
    return FluentIterable.concat(getDelegate(), Arrays.asList(elements));
  }

  /**

   * which the elements appear in the given collection.
   *
   * @param elements the elements, all of the same {@code enum} type, that the set should contain
   * @return an immutable set containing those elements, minus duplicates
   */
  public static <E extends Enum<E>> ImmutableSet<E> immutableEnumSet(Iterable<E> elements) {
    if (elements instanceof ImmutableEnumSet) {

        return elements;
    }

    /**
     * Returns an array of {@literal byte}.
     *
     * @param elements the elements of the array
     * @return the array
     */
    public static byte[] asByteArray(final byte... elements) {
        return elements;
    }

    /**
     * Returns an array of {@literal short}.
     *
     * @param elements the elements of the array
     * @return the array

    }

    @Override
    public List<Double> create(Object... elements) {
      Double[] array = new Double[elements.length];
      int i = 0;
      for (Object e : elements) {
        array[i++] = (Double) e;
      }
      return create(array);
    }

    /**
     * Creates a new collection containing the given elements; implement this method instead of
     * {@link #create(Object...)}.
     */

  }

  /**
   * Adds the given element to this queue. If this queue has a maximum size, after adding {@code
   * element} the queue will automatically evict its greatest element (according to its comparator),
   * which may be {@code element} itself.
   *
   * @return {@code true} always
   */
  @CanIgnoreReturnValue
  @Override
  public boolean add(E element) {
    offer(element);
    return true;
  }

    @Override
    protected List<Double> create(Double[] elements) {
      return asList(elements);
    }
  }

  public static final class DoublesAsListHeadSubListGenerator extends TestDoubleListGenerator {
    @Override
    protected List<Double> create(Double[] elements) {
      Double[] suffix = {Double.MIN_VALUE, Double.MAX_VALUE};
      Double[] all = concat(elements, suffix);
      return asList(all).subList(0, elements.length);

/**
 * 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"

  protected <E extends Comparable<? super E>> Set<E> copyOf(E[] elements) {
    return ImmutableSet.copyOf(elements);
  }

  @Override
  protected <E extends Comparable<? super E>> Set<E> copyOf(Collection<? extends E> elements) {
    return ImmutableSet.copyOf(elements);
  }

  @Override
  protected <E extends Comparable<? super E>> Set<E> copyOf(Iterable<? extends E> elements) {
    return ImmutableSet.copyOf(elements);
  }

    final BlockingQueue<Object> q;
    final int elements;
    final CountDownLatch beganProducing = new CountDownLatch(1);
    final CountDownLatch doneProducing = new CountDownLatch(1);

    Producer(BlockingQueue<Object> q, int elements) {
      this.q = q;
      this.elements = elements;
    }

    @Override
    public @Nullable Void call() throws InterruptedException {

    @Override
    protected List<String> create(String[] elements) {
      ImmutableSortedMap.Builder<String, Integer> builder = ImmutableSortedMap.naturalOrder();
      for (int i = 0; i < elements.length; i++) {
        builder.put(elements[i], i);
      }
      return builder.build().keySet().asList();
    }

    @Override