AP CSA Inheritance and Polymorphism 2

Question 1

What is dynamic dispatch (dynamic method lookup) in Java?

Accepted Answer

The JVM determines which overridden method to call based on the actual runtime type of the object

Answer

The compiler selects the method at compile time based on the declared type

Answer

A method that dispatches multiple threads

Answer

A way to call methods using reflection

Question 2

If class Dog extends Animal and both have a `speak()` method, what does `Animal a = new Dog(); a.speak();` call?

Accepted Answer

Dog's speak() method

Answer

Animal's speak() method

Answer

Both methods in sequence

Answer

A compile error

Question 3

What does it mean for a class to be `abstract`?

Accepted Answer

It cannot be instantiated and may contain abstract methods

Answer

It has no fields

Answer

It cannot have any methods

Answer

It is the superclass of all classes

Question 4

What must a concrete (non-abstract) subclass do with abstract methods it inherits?

Accepted Answer

Implement (override) all of them

Answer

Ignore them

Answer

Declare them abstract again

Answer

Delete them

Question 5

Can a subclass inherit from multiple superclasses in Java?

Accepted Answer

No, Java only supports single inheritance for classes

Answer

Yes, using the extends keyword multiple times

Answer

Yes, using the implements keyword for classes

Answer

No, and interfaces also don't support multiple inheritance

Question 6

What is a common use of the `instanceof` operator in polymorphism?

Accepted Answer

To check the actual runtime type of an object before a downcast

Answer

To check if two objects are equal

Answer

To create a new object of a given type

Answer

To call a superclass method