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Adapter Pattern in java

An adapter pattern helps two incompatible interfaces to work together. This is the real world definition for an adapter. The adapter design pattern is used when you want two different classes with incompatible interfaces to work together. Interfaces may be incompatible but the inner functionality should suit the need. The Adapter pattern allows otherwise incompatible classes to work together by converting the interface of one class into an interface expected by the clients.

There are many real world examples, the simplest example is power socket and plug. American plug would not fit to British socket, and viceversa. We use power adapter to fix this issue. The adapter design pattern works exactly similar to power adapter. Here is the UML structure for adapter pattern:

Lets take a simple example. In a factory, there is a automated furnance system. The furnance can be controlled only through temperature in fahrenheit format. But Furnance Regulatory systems gets tempareture in centigrade format. To fix this issue, we use adapter pattern.

FurnanceController class, which controls furnance temperature

package com.java2novice.dp.adapter;

public class FurnanceController {

	 * this method accepts heat in Fahrenheit format
	 * @param heatLevel
	public void changeFurnanceTemperature(int heatLevel){
		System.out.println("heat the furnance..");

Adapter class, which converts temperature from centigrade format to fahrenheit format.

package com.java2novice.dp.adapter;

public class FurnanceControllerAdapter extends FurnanceController{

	 * this method access temperature only in centigrade format
	 * @param heatLevel
	public void controlFurnance(int heatLevel){
		// convert temperature from centigrade to fahrenheit formate
		heatLevel = (heatLevel - 32)*5/9;

Regulatory system sample code:

package com.java2novice.dp.adapter;

public class FurnanceRegulatorySystem {

	public void regulateFurnanceTemperature(){
		 * here some lines of code gives temperature in centigrade format 
		FurnanceControllerAdapter fca = new FurnanceControllerAdapter();
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Java design pattern examples

  1. Factory Pattern
  2. Abstract Factory Pattern
  3. Builder Design Pattern
  4. Prototype Pattern
  5. Adapter Pattern
  6. Composite Pattern
  7. Proxy Pattern
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Can we call servlet destory() from service()?
As you know, destory() is part of servlet life cycle methods, it is used to kill the servlet instance. Servlet Engine is used to call destory(). In case, if you call destory method from service(), it just execute the code written in the destory(), but it wont kill the servlet instance. destroy() will be called before killing the servlet instance by servlet engine.
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I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected].

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java™ Platform Standard Ed. 8 - API Specification | Java is registered trademark of Oracle.
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