Core Java Programming Course- Interface

This video tutorial explains the concept of interfaces in Java, highlighting their role as collections of abstract methods. It covers how to create and implement interfaces, the differences between interfaces and abstract classes, and the concept of interface inheritance, including multiple inheritance. The tutorial also discusses the features and limitations of interfaces, such as the inability to instantiate them or have data members, and the inclusion of static and default methods.

What is the primary characteristic of methods within a Java interface?

• They are abstract by default.

• They are always public and final.

• They are private by default.

• They must be static.

How does a class inherit from an interface in Java?

• By using the 'adopts' keyword.

• By using the 'implements' keyword.

• By using the 'inherits' keyword.

• By using the 'extends' keyword.

What happens when a class implements an interface?

• It must provide implementations for all abstract methods.

• It automatically inherits the methods.

• It can only implement one interface.

• It can ignore the methods in the interface.

Can an interface extend another interface in Java?

• No, interfaces cannot extend each other.

• Yes, using the 'implements' keyword.

• Yes, using the 'extends' keyword.

• No, interfaces can only implement classes.

What is a key difference between classes and interfaces regarding inheritance?

• Classes can implement multiple interfaces.

• Interfaces can extend multiple interfaces.

• Interfaces cannot extend other interfaces.

• Classes can extend multiple classes.

What must a non-abstract class do when it implements an interface?

• It cannot implement more than one interface.

• It must be declared as final.

• It can choose which methods to implement.

• It must implement all abstract methods from the interface.

Why can't interfaces be instantiated in Java?

• Because they have no constructors.

• Because they are always abstract.

• Because they are static by default.

• Because they are private.

What is a unique feature of interfaces introduced in Java 8?

• Interfaces can have protected methods.

• Interfaces can have constructors.

• Interfaces can have private methods.

• Interfaces can have static and default methods.

What is true about variables declared in an interface?

• They can be changed in implementing classes.

• They can be private.

• They are protected by default.

• They are public, static, and final by default.

What is the default access level for methods in an interface?

• Protected

• Public

• Package-private

• Private