Abstract classes and interfaces o Don't provide implementation for some/all methods o Can not be instantiated o Subclasses that wish to be instantiable must implement all abstract/interface methods ●Allows us to provide a“contract”without a default implementation o Can have references to abstract classes and interfaces o Can implement as many interface as we wantAbstract classes and interfaces l Don’t provide implementation for some/all methods l Can not be instantiated l Subclasses that wish to be instantiable must implement all abstract/interface methods l Allows us to provide a “contract” without a default implementation l Can have references to abstract classes and interfaces l Can implement as many interface as we want