public <C extends @Nullable Closeable> C register(@ParametricNullness C closeable) {
    if (closeable != null) {
      stack.addFirst(closeable);
    }

    return closeable;
  }

  /**
   * Stores the given throwable and rethrows it. It will be rethrown as is if it is an {@code
   * IOException}, {@code RuntimeException} or {@code Error}. Otherwise, it will be rethrown wrapped

      while (elements.hasNext()) {
        add(elements.next());
      }
      return this;
    }

    @CanIgnoreReturnValue
    @SuppressWarnings("unchecked") // ArrayBasedBuilder stores its elements as Object.
    Builder<E> combine(Builder<E> other) {
      if (hashTable != null) {
        for (int i = 0; i < other.size; ++i) {