Learn Java from Scratch - A Beginner's Guide - Step 18 - Java Interface - Puzzles - Unimplemented methods, Abstract Clas

The video tutorial covers various aspects of Java interfaces, including how interfaces can extend other interfaces and the requirements for implementing them in classes. It explains the use of abstract classes to partially implement interfaces and the role of constants within interfaces. The tutorial also introduces default methods in interfaces, a feature available from Java 8, which allows providing default implementations to prevent compilation errors when extending interfaces. The video concludes with practical examples and scenarios where these concepts are applied.

What must a class do if it implements an interface that extends another interface?

• Implement only the methods in the extended interface

• No implementation is needed

• Implement methods from both the interface and its parent interface

• Implement methods from the parent interface only

How can you implement only some methods of an interface?

• By using a static class

• By using an abstract class

• By using a final class

• By using a sealed class

What is the nature of variables declared in an interface?

• They are local variables

• They are mutable variables

• They are constants

• They are instance variables

What keyword is used to define a default method in an interface?

• abstract

• default

• final

• static

What happens if a class implements an interface with a default method but does not override it?

• The class will not compile

• The class will ignore the method

• The class will use the default implementation

• The class will throw a runtime error

Why are default methods particularly useful when extending interfaces?

• They make interfaces immutable

• They allow interfaces to have constructors

• They prevent compilation errors when new methods are added

• They allow for multiple inheritance

What is a potential benefit of using default methods in interfaces?

• They simplify exception handling

• They allow interfaces to be instantiated

• They enforce strict type checking

• They enable backward compatibility