Differences between Interface and Class in Java

Differences Between Interface and Class in Java

In this video, we will explore the differences between interfaces and classes in Java. Understanding these differences is crucial for effective Java programming, especially in designing robust and flexible applications. This tutorial is perfect for students, professionals, or anyone interested in enhancing their Java programming skills.

Why Learn About Interfaces and Classes?

Understanding the differences between interfaces and classes helps to:

• Design better object-oriented programs.
• Implement polymorphism and abstraction effectively.
• Enhance code flexibility and maintainability.

Key Concepts

1. Class:

• A blueprint for creating objects (instances). A class encapsulates data for the object and methods to manipulate that data.

2. Interface:

• A reference type in Java, similar to a class, that can contain only constants, method signatures, default methods, static methods, and nested types. Interfaces cannot contain instance fields or constructors.

Main Differences Between Interface and Class

1. Declaration:

• Class: Declared using the class keyword.
• Interface: Declared using the interface keyword.

2. Implementation:

• Class: Can implement multiple interfaces but can inherit from only one superclass (single inheritance).
• Interface: Can be implemented by any class or extended by another interface.

3. Methods:

• Class: Can have fully implemented methods (with a method body).
• Interface: Can have abstract methods (without a method body) and default methods (with a method body). All methods are implicitly public and abstract unless declared as default or static.

4. Fields:

• Class: Can have instance variables (fields) with any access modifier.
• Interface: Can have only constants (public, static, final fields).

5. Inheritance:

• Class: Supports single inheritance (a class can inherit from one superclass only).
• Interface: Supports multiple inheritance (a class can implement multiple interfaces, and an interface can extend multiple interfaces).

6. Constructors:

• Class: Can have constructors to initialize the object.
• Interface: Cannot have constructors.

7. Accessibility:

• Class: Can have any access modifier (public, protected, private, default).
• Interface: Methods are implicitly public. Fields are implicitly public, static, and final.

Practical Examples

Example 1: Defining a Class

Class Declaration:

• Define a class with instance variables, methods, and a constructor.

Class Implementation:

• Create an object of the class and call its methods.

Example 2: Defining an Interface

Interface Declaration:

• Define an interface with abstract methods and default methods.

Interface Implementation:

• Implement the interface in a class and provide implementations for the abstract methods.

Example 3: Using Interfaces for Polymorphism

1. Multiple Implementations:
   • Implement multiple interfaces in a class and demonstrate polymorphic behavior.

Example 4: Extending Interfaces

1. Interface Inheritance:
   • Extend one interface with another and demonstrate multiple inheritance in interfaces.

Practical Applications

Design Patterns:

• Use interfaces to implement design patterns such as Strategy, Factory, and Observer.

Abstraction:

• Define abstract behaviors with interfaces to decouple the implementation from the definition.

Polymorphism:

• Use interfaces to achieve polymorphism, allowing objects to be accessed through references of their interface type.

Additional Resources

For more detailed information and a comprehensive guide on the differences between interfaces and classes in Java, check out the full article on GeeksforGeeks: https://www.geeksforgeeks.org/differences-between-interface-and-class-in-java/. This article provides in-depth explanations, examples, and further readings to help you master these concepts.

By the end of this video, you’ll have a solid understanding of the differences between interfaces and classes in Java, enhancing your ability to design and implement effective Java applications.

Read the full article for more details: https://www.geeksforgeeks.org/differences-between-interface-and-class-in-java/.

Thank you for watching!