* current array, create a new array.
     */
    private void ensureRoomFor(int newElements) {
      @Nullable Object[] contents = this.contents;
      int newCapacity = expandedCapacity(contents.length, size + newElements);
      // expandedCapacity handles the overflow case
      if (newCapacity > contents.length || forceCopy) {

    Builder(int capacity) {
      this.contents = new @Nullable Object[capacity];
      this.size = 0;
    }

    private void ensureRoomFor(int newElements) {
      @Nullable Object[] contents = this.contents;
      int newCapacity = expandedCapacity(contents.length, size + newElements);
      // expandedCapacity handles the overflow case
      if (contents.length < newCapacity || copyOnWrite) {

  public boolean add(E element) {
    offer(element);
    return true;
  }

  @CanIgnoreReturnValue
  @Override
  public boolean addAll(Collection<? extends E> newElements) {
    boolean modified = false;
    for (E element : newElements) {
      offer(element);
      modified = true;
    }
    return modified;
  }

  /**

  public boolean add(E element) {
    offer(element);
    return true;
  }

  @CanIgnoreReturnValue
  @Override
  public boolean addAll(Collection<? extends E> newElements) {
    boolean modified = false;
    for (E element : newElements) {
      offer(element);
      modified = true;
    }
    return modified;
  }

  /**

   * @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.
   *
   * @throws UnsupportedOperationException always

     */
    @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.
     *
     * @throws UnsupportedOperationException always

     */
    @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.
     *
     * @throws UnsupportedOperationException always