HorizontalListSnippets.java

//....
private void setupAdapter(Bundle savedInstanceState) {
  adapter = createNewAdapter();
  dataset = createDataset(adapter);
  adapter.articleDataset(dataset);
  recyclerView.setAdapter(adapter);
  //...
}

@Override protected ArticleDataset createDataset(ArticlesAdapter adapter) {
  ArticleDataset dataset = new ArticleDataset(recyclerView, adapter);
  dataset.generateRandom();
  return dataset;
}

@Override protected ArticlesAdapter createNewAdapter() {
      return new ArticlesAdapter() {
        //...
   };
}