Page 1338 - AP Computer Science A, 7th edition

28. (A) Statement I is false: An interface may not be instantiated, but a class that implements the interface can be instantiated, provided it is not an abstract class. Statement II is false: Any subclass of SomeClass will automatically implement the interface, but not necessarily the superclass. For example, suppose a superclass Animal has a subclass Bird. And suppose Bird implements CanFly, which is an interface with a single method, fly. Clearly, Animal shouldn’t implement CanFly—not all animals fly. Statement III appears to be true: This is what it means for a class to implement an interface— it’s a promise that the class will contain all methods of that interface. This is not true, however, if SomeClass is an abstract class. Any method of the interface that is not implemented in SomeClass then automatically becomes an abstract method of SomeClass and must be implemented by any nonabstract subclass of SomeClass.