/* Java doesn't allow you to inherit from more than one

* class. So, what do you do when you want do you do

* when you want to add additional functionality?

* You create an interface. Interfaces are empty

* classes. They provide all of the methods you must

* use, but none of the code.

*/

// This is how you define an interface. They normally

// have a name that is an adjective. Adjectives modify

// nouns. Most objects have noun names

public interface Drivable {

// You can put fields in an interface, but understand

// that their values are final and can't be changed

double PI = 3.14159265;

// All methods in an interface must be implemented

// They are public and abstract by default

// An abstract method must be defined by any class

// that uses the interface

int getWheels();

// You can't define a method as final and abstract

// final means the method can't be changed and

// abstract means it must be changed

void setWheels(int numWheels);

double getSpeed();

void setSpeed(double speed);

}