Quiz: Abstract Classes and Interfaces

5 questionsNo time limitPass: 60%+10 XP on first pass

Abstraction hides "how" and shows "what". Learn abstract classes and methods, interfaces with default and static methods, multiple interfaces, and how to choose.

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Question 1
Can you create an object of an abstract class with new?
Yes, alwaysNoOnly if it has a constructorOnly inside main
Question 2
How many interfaces can a class implement?
OneTwoManyNone
Question 3
Fields declared in an interface are automatically:
privateprotected and mutablepublic static final (constants)instance variables

Question 4

What does this print?

interface Greeter { default String hi() { return "hi"; } }
class Friend implements Greeter { }
public class Main {
    public static void main(String[] args) {
        System.out.println(new Friend().hi());
    }
}

hinullError: hi() not implementedFriend

Question 5
Which is a functional interface?
An interface with no methodsAn interface with exactly one abstract methodAny abstract classAn interface with only default methods