class DownloadListener4 implements DownloadListener,
        Listener4Assist.Listener4Callback, ListenerAssist {

    @Override
    public final void taskEnd(@NonNull DownloadTask task, @NonNull EndCause cause,
                              @Nullable Exception realCause) {
        assist.taskEnd(task, cause, realCause);
    }

      DownloadListener4(Listener4Assist assist);
    public  DownloadListener4();

}