"Human" interfaces with two implementation classes
A class is a blueprint or template or set of instructions to build a specific type of object. Every object is built from a class.
  An instance is a specific object built from a specific class. It is assigned to a reference variable that is used to access all of the instance's properties and methods.
  


Ryan and nate should both be an instance. They have the same properties. From the 2 classes you can extract one template and make it a Human class.

What you are doing now is hard coding their properties into the methods. Try to make it more dynamic by creating one class.


public void eat() {
    System.out.println("Nate has eaten");
}



Can then be tranformed into:

public void eat() {
    System.out.println(this.name + " has eaten");
}