class DownloadListener4 implements DownloadListener,
        Listener4Assist.Listener4Callback, ListenerAssist {

    @Override public void fetchEnd(@NonNull DownloadTask task, int blockIndex, long contentLength) {
        assist.fetchEnd(task, blockIndex);
    }

      DownloadListener4(Listener4Assist assist);
    public  DownloadListener4();

}