Java Programming for Complete Beginners - Java 16 - Step 18 - Java Interface - Puzzles - Unimplemented methods, Abstract

The video tutorial covers various aspects of Java interfaces, including how interfaces can extend other interfaces and the requirements for implementing them. It explains the role of abstract classes in implementing interfaces and the use of constants within interfaces. The tutorial also introduces default methods in interfaces, a feature available from Java 8, and discusses how they can be used to prevent compilation errors when extending interfaces. The video concludes with examples demonstrating these concepts.

What must a class do to successfully implement an interface that extends another interface?

• Implement only the methods in the extended interface

• Implement all methods in the interface hierarchy

• Implement methods only if they are abstract

• Implement methods only if they are public

How can a class implement only some methods of an interface?

• By using a private class

• By creating an abstract class

• By declaring the class as final

• By using a static class

What is the nature of variables declared in an interface?

• They are instance variables

• They are local variables

• They are mutable variables

• They are constants

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

• abstract

• static

• final

• default

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

• The class will not compile

• The class will use the default implementation

• The class will throw a runtime error

• The class will ignore the method

Why are default methods useful when extending an interface?

• They allow interfaces to be instantiated

• They allow interfaces to have private methods

• They make all methods in the interface optional

• They prevent compilation errors in existing implementations

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

• They make interfaces faster

• They allow interfaces to have constructors

• They enable backward compatibility

• They allow for multiple inheritance