User in RecyclerView

Hey,

I'm new to Android and love how in-depth these tutorials are compared to a lot of the other material online. However, I'm confused at where User and RecyclerViewSimpleTextViewHolder come from in the 'Heterogenous Layouts inside RecyclerView'.
```
private void configureDefaultViewHolder(RecyclerViewSimpleTextViewHolder vh, int position) {
vh.getLabel().setText((CharSequence) items. get(position));

private void configureViewHolder1(ViewHolder1 vh1, int position) {
User user = (User) items.get(position);
if (user != null) {
vh1.getLabel1().setText("Name: " + user.name);
vh1.getLabel2().setText("Hometown: " + user.hometown);
}
}`
```

Thanks!