code: public Container xor(Container x) {
      if (x instanceof ArrayContainer) {
        return xor((ArrayContainer) x);
      } else if (x instanceof BitmapContainer) {
        return xor((BitmapContainer) x);
      }
      return xor((RunContainer) x);
    }
docs: Computes the bitwise OR of this container with another (symmetric difference). This container
  as well as the provided container are left unaffected.
  
  @param x other parameter
  @return aggregated container