Interface Inheritance 

An interface is a class that declares features but provides no implementation.  It is a specification that any implementing class must conform to.  Any variables contained within an interface are implicitly defined as public, static, and final, and any methods are implicitly abstract and public.

Classes that implement an interface must provide an implementation for all of the methods declared in the interface.  A class implements zero or more interfaces, and an interface can extend zero or more other interfaces. Classes, however, can extend only one other class, even if it implements one or more interfaces.

Implementing classes implement the methods contained in the interface by overriding them.  This is done by declaring methods with the same type signature.  If the class is implementing more than one interface, all methods contained in all interfaces should be overridden.

An example interface is defined as follows:

public interface Driveable {

        boolean hasWheels()        …

}