class DownloadOkHttp3Connection implements DownloadConnection, DownloadConnection.Connected {

    @Override public int getResponseCode() throws IOException {
        if (response == null) throw new IOException("Please invoke execute first!");
        return response.code();
    }

      DownloadOkHttp3Connection(@NonNull OkHttpClient client,
                              @NonNull Request.Builder requestBuilder);
      DownloadOkHttp3Connection(@NonNull OkHttpClient client, @NonNull String url);

}