custom filter for products

ProductosAdapter.java

 @NonNull
    @Override
    public Filter getFilter() {
        return new Filter() {
            @Override
            protected FilterResults performFiltering(CharSequence charSequence) {
                String filterString = charSequence.toString().toUpperCase();
                FilterResults filterResults = new FilterResults();

                if (filterString == null || filterString.length() == 0) {
                    filterResults.values = productos;
                    filterResults.count = productos.size();
                    return filterResults;
                }

                /*listar filtrado*/
                List<Producto> encontrados = new ArrayList<>();
                for (Producto p : productos) {
                    if (p.descripcion.toUpperCase().contains(filterString)) {
                        encontrados.add(p);
                    }
                }

                filterResults.values = encontrados;
                filterResults.count = encontrados.size();

                return filterResults;
            }

            @Override
            protected void publishResults(CharSequence charSequence, FilterResults filterResults) {
                notifyDataSetChanged();
                clear();
                addAll((Collection<? extends Producto>) filterResults.values);
                notifyDataSetInvalidated();
            }
        };
    }