Learn Java from Scratch - A Beginner's Guide - Step 19 - Java Interface Versus Abstract Class - a Comparison

The video explores the differences between abstract classes and interfaces, emphasizing that while their syntax may appear similar, they serve different purposes. Interfaces are used to establish communication patterns between systems, while abstract classes provide a high-level structure for subclasses. The video highlights that interfaces cannot have private methods or variables, whereas abstract classes can. Additionally, a class can implement multiple interfaces but cannot extend multiple abstract classes. The video concludes by summarizing these syntactical differences.

What is the primary reason for using an interface?

• To provide a high-level structure for subclasses

• To establish a communication pattern between systems or components

• To ensure all subclasses meet a specific structure

• To allow multiple inheritance

What is the main purpose of an abstract class?

• To define a communication pattern

• To provide a high-level structure and leave implementation to subclasses

• To allow multiple inheritance

• To ensure all methods are public

How does an abstract class differ from an interface in terms of inheritance?

• An interface can be extended by multiple classes

• An abstract class can be extended by multiple classes

• An interface allows multiple inheritance

• An abstract class allows multiple inheritance

Which of the following is true about methods in an interface?

• They are always public

• They can be protected

• They can be private

• They can have a concrete implementation

What is a key difference in variable usage between an abstract class and an interface?

• Interfaces can have variables with changing values

• Abstract classes cannot have variables

• Abstract classes can only have constant variables

• Variables in interfaces are constants