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Adapter Pattern

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This pattern establishes a relationship between the two unrelated interfaces such that they work together.

Adapter Pattern

     

This pattern establishes a relationship between the two unrelated interfaces such that they work together. This is similar to the conversion of one interface of one class to the interface expected by the client. To understand clearly lets take an example:

Suppose there are several sockets of different sizes, and shapes in a house. Due to variation in sizes, all the sockets are not capable of plug-in a mobile charger. So we use an Adapter to make it portable across different sockets. Here Adapter works as a connector. This connector connects them together and meets the purpose of the client.

Benefits: It helps the developers to relate the unrelated class such that they may work together. It provides compatibility between the classes and increases the transparency. Additionally it provides a pluggable kit, delegates objects, makes the classes highly reusable and achieves the goal through inheritance or composition. 

It also tries to match the interfaces such as WindowAdapter, KeyAdapter, MouseAdapter, ContainerAdapter, ComponentAdapter, FocusAdapter and MouseMotionAdapter. 

Usage:  The adapter pattern is meant to use an existing class to fulfill the client's class requirements. For example, suppose a client specifies his requirement in an interface, and then to meet the purpose usually a class is created that implements the required interface and inherits the existing class into the subclasses. This approach creates a class known as the adapter class which translates the client's calls to the existing class methods. Adapter pattern also helps to make improvements in the new code and to make the code more manageable. It improves the performance while designing the system.

Now think all such things technically and try to resolve the problem. There are two ways of implementing the Adapter Pattern, either use the Inheritance or use the composition.

Let's do it with the approach of Inheritance.
First develop a socket interface as:

Switch.java

public interface Switch {

public void switchOn();
public void switchOff();

}

Implement Switch.java in a class say Fan class. The class is given below :

Fan. java

public class Fan implements Switch{

public void switchOn() {
System.out.println("FAN Switched ON");
}
public void switchOff() {
System.out.println("FAN Switched OFF");
}

public static void main(String arg[]){
Fan f = new Fan();
f.switchOn();
f.switchOff();
}

}

Here is the output of the above Fan.java program :

C:\>javac Fan.java
C:\>java Fan
Fan Switched ON
Fan Switched OFF

Finally, there will be an adapter class. This will inherit the Switch and give output for Fan.

Bulb.java:

public class Bulb implements Switch {
public void switchOn() {
System.out.println("BULB Switched ON");
}
public void switchOff() {
System.out.println("BULB Switched OFF");
}
}

Here is the output of the above Bulb.java program:

C:\>javac Bulb.java
C:\>java Bulb
Bulb Switched ON
Bulb Switched OFF

Similarly, let?s consider the Association and Composition of objects by which Adapter can be implemented.

The above example shows how Adapter pattern works. When one interface cannot be changed and needed to suit again a cannot-be-changed client, then an adapter is used so that both the interfaces work together.

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Posted on: December 13, 2008

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