AP CSA Inheritance and Polymorphism 3

Question 1

What is a 'has-a' relationship in OOP (as opposed to 'is-a')?

Accepted Answer

Composition — one class contains a reference to another class

Answer

Inheritance — one class extends another

Answer

Overriding — one class replaces a method

Answer

Abstraction — hiding implementation details

Question 2

What does the `final` keyword do when applied to a method in Java?

Accepted Answer

Prevents the method from being overridden in subclasses

Answer

Makes the method run only once

Answer

Makes the method static

Answer

Prevents the method from being called externally

Question 3

Which of the following correctly performs a downcast from Animal to Dog?

Accepted Answer

Dog d = (Dog) a;

Answer

Dog d = a;

Answer

Dog d = new Dog(a);

Answer

Dog d = a.toDog();

Question 4

What is the role of an interface in Java's type system for AP CSA purposes?

Accepted Answer

It defines a contract of methods that implementing classes must provide

Answer

It is a class that cannot be instantiated

Answer

It provides a default implementation for all methods

Answer

It replaces the need for inheritance

Question 5

If a subclass constructor does not explicitly call `super()`, what happens in Java?

Accepted Answer

Java automatically inserts a call to the no-argument superclass constructor

Answer

A compile error occurs

Answer

The superclass fields are left uninitialized

Answer

The superclass constructor is never called

Question 6

What is the term for when a superclass method calls an overridden method that runs the subclass version?

Accepted Answer

Polymorphic dispatch

Answer

Static binding

Answer

Method hiding

Answer

Encapsulation