};
      }

      @Override
      public Stream<E> stream() {
        return set1.stream().filter(set2::contains);
      }

      @Override
      public Stream<E> parallelStream() {
        return set1.parallelStream().filter(set2::contains);
      }

      @Override
      public int size() {
        int size = 0;
        for (E e : set1) {
          if (set2.contains(e)) {
            size++;