Q:

What Java class can I extend to?

What Java class can I extend to so that I gain inheritance to treeTableView? How do I extend a class that is already extended?
I'm currently extending it using treeTableView.
The demo file shows this:
final TreeItem<User> root = new RecursiveTreeItem<User>(users, RecursiveTreeObject::getChildren);

This is what I tried working out, but it's not working: 
final TreeItem<Patient> root = new Patient(patients, Patient::getChildren);

What do I do?

A:

I extended the Person superclass to RecursiveTreeObject. Through inheritance it worked.

