AP CSA Interfaces and Abstract Classes

Question 1

Which keyword is used to declare an interface in Java?

Accepted Answer

interface

Answer

abstract

Answer

implements

Answer

extends

Question 2

Which keyword does a class use to adopt an interface?

Accepted Answer

implements

Answer

extends

Answer

inherits

Answer

interface

Question 3

By default, all methods declared inside an interface are:

Accepted Answer

public and abstract

Answer

private and abstract

Answer

protected and final

Answer

public and static

Question 4

What happens if a class implements an interface but does not override all of its abstract methods?

Accepted Answer

The class must be declared abstract

Answer

The class inherits empty implementations

Answer

A runtime exception is thrown

Answer

The compiler ignores unimplemented methods

Question 5

Can a single class in Java implement more than one interface?

Accepted Answer

Yes, by listing them separated by commas after implements

Answer

No, Java only allows one interface per class

Answer

Yes, but only if they share no method names

Answer

No, multiple interfaces require an abstract class

Question 6

Which of the following is TRUE about variables declared inside an interface?

Accepted Answer

They are public, static, and final by default

Answer

They are private by default

Answer

They can be instance variables

Answer

They can be reassigned by implementing classes

Question 7

Which of the following best describes the purpose of an interface in Java?

Accepted Answer

To define a contract specifying what methods a class must implement

Answer

To provide a partial implementation that subclasses extend

Answer

To prevent a class from being instantiated

Answer

To allow direct instantiation with default behaviors