Hello Jetto Net followers!

Welcome to our Java Object-Oriented Programming (OOP) series. In our previous article, we explored encapsulation, which protects the internal structure of objects and ensures data security. In this article, we will discover an important structure that enhances the flexibility and extensibility of OOP: "interfaces." Interfaces act as a kind of contract between classes, allowing different classes to exhibit common behaviors.

What is an Interface?

In Java, an interface is a construct that defines methods that must be implemented by the classes that derive from it. To make it more memorable, you can think of an interface as a guide, a set of instructions, or a list of tasks that classes derived from it need to perform.
Interfaces specify what a class should do, not how it should do it. This allows different classes to implement the same interface in various ways.

Defining an Interface in Java

To define a class as an interface in Java, we use the interface keyword. The interface name should start with a capital letter and is usually set as an adjective (e.g., Flyable, Swimmable, Edible). Inside the interface, we define method signatures.

public interface Flyable { 
    void fly(); 
    void land();
}

In the example above, we defined an interface named Flyable. This interface contains two method signatures: fly() and land().

Implementing an Interface

A class must use the implements keyword to implement an interface. When a class implements an interface, it must provide implementations for all the methods declared in that interface.

public class Bird implements Flyable {
    @Override
    public void fly() {
        System.out.println("The bird is flying!");
    }
    @Override
    public void land() {
        System.out.println("The bird is landing!");
    }
}

In the example above, the Bird class implements the Flyable interface. Therefore, the Bird class is required to provide implementations for the fly() and land() methods.

Benefits of Interfaces

• Multiple Inheritance: Although Java does not support multiple inheritance for classes, a class can implement multiple interfaces. This allows a class to combine methods from different interfaces into a single class.
• Flexibility: Interfaces allow classes to evolve independently of one another. If a class that implements an interface changes, other classes are not affected.
• Contract: Interfaces can be thought of as a type of contract that specifies what behaviors a class should support. This results in more understandable and organized code.

Interfaces are an essential part of object-oriented programming in Java. By using interfaces, we can make our code more flexible, extensible, and comprehensible. In our next article, we will continue exploring other important OOP concepts. Feel free to share your questions or comments in the comments section.

Happy Coding!