private class ViewHolder extends RecyclerView.ViewHolder {    private TextView tv_name;     public ViewHolder(View itemView) {         super(itemView);         tv_name = itemView.findViewById(R.id.tv_name);     } }       @Override public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {     if (holder instanceof ViewHolder) {        Bean bean = mlist.get(position);         ((ViewHolder) holder).tv_name.setText(bean.getTdi_name());     } }     為什么我在ViewHolder類private聲明的控件 能直接被.調用，有點無法理解，還望指教。