Java Programming for Complete Beginners - Java 16 - Step 15 - Java Abstract Class – Puzzles

The video tutorial explores abstract classes in programming, discussing their syntax and usage. It explains that abstract classes can exist without abstract methods and can contain variables and non-abstract methods. The tutorial also covers how to create and extend abstract classes, emphasizing that an abstract class can extend another abstract class without implementing its abstract methods. The video concludes with examples of non-abstract methods within abstract classes.

Is it syntactically correct to create an abstract class without any abstract methods?

• No, it will cause a compilation error.

• Yes, and it is a common practice.

• No, it is not allowed.

• Yes, but it is not practically useful.

What must a subclass do if it extends an abstract class with abstract methods?

• It must implement all abstract methods and cannot be abstract.

• It must implement all abstract methods or be declared abstract itself.

• It can ignore the abstract methods.

• It must override all methods, abstract or not.

How can a subclass remain abstract when extending an abstract class?

• By not implementing any methods.

• By declaring itself as abstract.

• By not having any methods.

• By implementing all methods.

Can an abstract class have member variables?

• No, it can only have abstract methods.

• Yes, it can have member variables.

• Yes, but only public variables.

• No, it cannot have any variables.

What type of methods can an abstract class contain?

• Only concrete methods.

• Both abstract and concrete methods.

• Only abstract methods.

• No methods at all.