}
      return this;
    }

    @CanIgnoreReturnValue
    public Builder<E> addAll(Iterable<? extends E> elements) {
      checkNotNull(elements); // for GWT
      for (E element : elements) {
        add(checkNotNull(element));
      }
      return this;
    }

    @CanIgnoreReturnValue
    public Builder<E> addAll(Iterator<? extends E> elements) {
      checkNotNull(elements); // for GWT

      contents[size++] = element;
      return this;
    }

    @CanIgnoreReturnValue
    @Override
    public Builder<E> add(E... elements) {
      addAll(elements, elements.length);
      return this;
    }

    final void addAll(@Nullable Object[] elements, int n) {
      checkElementsNotNull(elements, n);
      getReadyToExpandTo(size + n);
      /*

   * @deprecated Unsupported operation.
   */
  @CanIgnoreReturnValue
  @Deprecated
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  public final boolean addAll(Collection<? extends E> newElements) {
    throw new UnsupportedOperationException();
  }

  /**
   * Guaranteed to throw an exception and leave the collection unmodified.
   *