Adapter Class In Java

Adapter Class In Java

adapter class in java

Adapter Class In Java

Adapter Class In Java

Adapter Class In Java


Adapter Class In Java


In Java programming, event handling is a basic concept  of developing interactive applications. When developers are working with applications, they often find themselves implementing event listener interfaces to respond to various events like button clicks, mouse movements, or keyboard inputs. While this approach works well, it can result in lengthy code, especially when dealing with interfaces containing multiple methods.

Enter the “Adapter Class in Java”, the best solution to streamline event handling and improve code readability. The adapter class serves as a useful tool, offering an elegant way to tackle event listener interfaces effortlessly.

If you’re new to programming or unfamiliar with the concept of adapter class in Java, Don’t worry! This blog will guide you  from the basics. Also you can apply this concept in your projects.


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What is an Adapter Class?

An adapter class (wrapper class) acts as a mediator between two incompatible interfaces. It allows classes with different interfaces to work together seamlessly by converting the interface of one class into another, making them compatible. In simpler terms, an adapter class enables communication between two entities that would otherwise be unable to interact due to differences in their interfaces.

Types Of Adapter Class In Java

In Java, there are two commonly used types of adapter classes:

  1. Class adapters
  2. Object adapters

Let’s explore each type in detail:

Also Read: What Is Java Programming Language

Class Adapter

A class adapter uses inheritance to adapt the interfaces of two different classes. It extends the class that needs to be adapted and implements the interface expected by the client class. As a result, it inherits the functionality of the adapter class and makes it available through the interface required by the client.

In the example above, the “Target” interface defines the expected interface for the client class. The “Adaptee class” represents the existing functionality that needs to be adapted. The ClassAdapter class extends “Adaptee” and implements Target, providing the necessary adaptation by calling the specific method of the “Adaptee” within the request() method.

Object Adapter

An object adapter uses composition to adapt the interfaces of two different classes. It holds an instance of the “adaptee class” and implements the interface expected by the client class. By doing so, it delegates the method calls from the client to the “adaptee”, effectively adapting the functionality.

In this example, the “Target” interface defines the expected interface for the client class, while the “Adaptee class” represents the existing functionality. The ObjectAdapter class implements Target and holds an instance of “Adaptee”. By implementing the “request()” method and delegating the call to the “specificRequest()” method of the adaptee, the object adapter achieves the desired adaptation.

It’s worth noting that both class adapters and object adapters serve the same purpose of adapting the interfaces of two incompatible classes. The choice between them depends on the specific requirements and constraints of the project. Class adapters use inheritance and can only adapt a single class, while object adapters use composition and can adapt multiple classes by holding instances of the adaptees.

Also Read: What Is OOPS

The Need for Adapter Classes

Imagine you have a class “A”. “A” provides a specific set of methods. You want to use these methods in another class “B”, which expects a different set of methods. 

Here, an adapter class can bridge the gap by implementing the interface of class B while internally delegating the method calls to class A. By doing so, the adapter class allows class B to use class A’s functionality without modifying the existing code or interfaces.

Creating an Adapter Class

To create an adapter class in Java, follow these steps:

Step 1: Identify the incompatible interfaces:- Determine the interfaces of the classes that need to be connected.

Step 2: Create an adapter class:- Declare a new class that implements the interface expected by the client class (the class that requires the desired functionality).

Step 3: Implement the adapter class:- Implement the interface methods in the adapter class by calling the corresponding methods from the adapter class (the class that provides the existing functionality).

Step 4: Connect the classes:- Create an instance of the adapter class and pass it to the client class, enabling communication between the two interfaces.

Example Of Adapter Class

Let’s take an one example that demonstrates the usage of adapter classes. Suppose you have a legacy class, Square, which provides a method called “calculateArea()”. However, a new class, Circle, expects a different method called “computeArea()”. We can bridge this gap using an adapter class.

In the example above, we create an adapter class called “SquareToCircleAdapter” that implements the Circle interface. This adapter class takes an instance of the Square class as a constructor argument. By implementing the “computeArea()” method in the adapter class and delegating the call to the square’s “calculateArea()”  method, we establish compatibility between the two classes.

Benefits of Adapter Classes

1) Code reusability: Adapter classes enable the reuse of existing classes that have incompatible interfaces, saving development time and effort.

2) Seamless integration: Adapter classes facilitate the integration of legacy or third-party code into new systems, even when the interfaces differ.

3) Modularity: Adapter classes allow you to keep existing code intact while adapting it to new requirements, promoting modular and maintainable codebases.

4) Flexibility: Through adapters, you can extend the functionality of existing classes without modifying their original implementation.


Adapter classes are a powerful tool in Java that promote code reusability and seamless integration. By acting as a bridge between incompatible interfaces, adapter classes simplify the process of incorporating existing code into new projects. 

As a beginner, understanding and implementing adapter classes will significantly enhance your ability to leverage and build upon existing codebases. So, embrace adapter classes as a valuable asset in your journey as a Java developer and unlock the potential for efficient and maintainable software solutions.

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