Design Patterns

Design Patterns:
  Classified as :

Creational Pattern  :

                                 Singleton DesignPattern

package test.creational.designPattern;



class DatabaseConnection{
private static DatabaseConnection instance = new DatabaseConnection();
private DatabaseConnection(){

}
public static DatabaseConnection getDBConnection(){
return instance;
}
public void getConnection(){
System.out.println(" Established to Database successfully ");
}
}


public class SingletonExample {
public static void main(String args[]) {
DatabaseConnection.getDBConnection().getConnection();
}

}

                                 Factory Design Pattern

package test.creational.designPattern;

interface Shape {

void getShape();

}

class Circle implements Shape {

@Override

public void getShape() {

System.out.println(" Inside Circle ");

}

}

class Rectangle implements Shape {

@Override

public void getShape() {

System.out.println(" Inside Rectangle ");

}

}

class Square implements Shape {

@Override

public void getShape() {

System.out.println(" Inside Square ");

}

}

class Shapefactory {

public Shape getType(String shape) {

if (shape.equals("circle")) {

return new Circle();

}

if (shape.equals("rect")) {

return new Rectangle();

}

if (shape.equals("square")) {

return new Square();

}

return null;

}

}

public class FactoryExample {

public static void main(String args[]) {

Shapefactory shapefactory = new Shapefactory();

Shape shape1 = shapefactory.getType("rect");

shape1.getShape();

}

}

                                 Abstract Factory Pattern
                                     
Structural Patterns :

                                          Adapter:

package test.creational.designPattern;

interface MediaPlayer {

public void play(String audioType, String filename);
}

class MediaAdapter implements MediaPlayer {

AdvancedMediaPlayer advancedMusicPlayer;

public MediaAdapter(String audioType) {

if (audioType.equalsIgnoreCase("vlc")) {
advancedMusicPlayer = new VlcPlayer();

} else if (audioType.equalsIgnoreCase("mp4")) {
advancedMusicPlayer = new Mp4Player();
}

}

public void play(String audioType, String fileName) {

if (audioType.equalsIgnoreCase("vlc")) {
advancedMusicPlayer.playVlc(fileName);
} else if (audioType.equalsIgnoreCase("mp4")) {
advancedMusicPlayer.playMp4(fileName);
}
}

}

class AudioPlayer implements MediaPlayer {
MediaAdapter mediaAdapter;

@Override
public void play(String audioType, String fileName) {

// inbuilt support to play mp3 music files
if (audioType.equalsIgnoreCase("mp3")) {
System.out.println("Playing mp3 file. Name: " + fileName);
}

// mediaAdapter is providing support to play other file formats
else if (audioType.equalsIgnoreCase("vlc")
|| audioType.equalsIgnoreCase("mp4")) {
mediaAdapter = new MediaAdapter(audioType);
mediaAdapter.play(audioType, fileName);
}

else {
System.out.println("Invalid media. " + audioType
+ " format not supported");
}
}
}

interface AdvancedMediaPlayer {

public void playVlc(String fileName);

public void playMp4(String fileName);
}

class VlcPlayer implements AdvancedMediaPlayer {
@Override
public void playVlc(String fileName) {
System.out.println("Playing vlc file. Name: " + fileName);
}

@Override
public void playMp4(String fileName) {
// do nothing
}
}

class Mp4Player implements AdvancedMediaPlayer {

@Override
public void playVlc(String fileName) {
// do nothing
}

@Override
public void playMp4(String fileName) {
System.out.println("Playing mp4 file. Name: " + fileName);
}
}

public class AdapterSample {

public static void main(String[] args) {
AudioPlayer audioPlayer = new AudioPlayer();

audioPlayer.play("mp3", "beyond the horizon.mp3");
audioPlayer.play("mp4", "alone.mp4");
audioPlayer.play("vlc", "far far away.vlc");
audioPlayer.play("avi", "mind me.avi");
}

}

                         Proxy :
                                Protection , Remote
                         Bridge

                         Facade

package test.structural.designPattern;

interface Goods {

void getGoods();

}

class PackagedGoods implements Goods {

public void getGoods() {

System.out.println(" Allow to get the Packaged Foods");

}

}

class LooseGoods implements Goods {

public void getGoods() {

System.out.println(" Allow to get the Loose Food items");

}

}

class StoreOwner {

private Goods looseGoods;

private Goods packagedGoods;

public StoreOwner() {

this.looseGoods = new LooseGoods();

this.packagedGoods = new PackagedGoods();

}

public void getPackagedGoods() {

packagedGoods.getGoods();

}

public void getLooseGoods() {

looseGoods.getGoods();

}

}

public class FacadeSample {

public static void main(String[] args) {

StoreOwner storeOwner = new StoreOwner();

storeOwner.getPackagedGoods();

storeOwner.getLooseGoods();

}

}

                         FlyWeight

Behavioural Patterns

                         State

package test.behavioural.designPattern;

interface CompressionType {

void compressionType(CompressionContext context);

}

class ZipCompression implements CompressionType {

public void compressionType(CompressionContext context) {

System.out.println(" Compression Strategy is : ZIP");

}

}

class WinrarCompression implements CompressionType {

public void compressionType(CompressionContext context) {

System.out.println(" Compression Strategy is : WINRAR");

}

}

class CompressionContext {

CompressionType compressionType = new ZipCompression();

public void setCompressionType(CompressionType compressionType) {

this.compressionType = compressionType;

}

void getCompression() {

compressionType.compressionType(this);

}

}

public class StateDPDSample {

public static void main(String args[]) {

CompressionContext compressionContext = new CompressionContext();

compressionContext.getCompression();

compressionContext.setCompressionType(new WinrarCompression());

compressionContext.getCompression();

}

}

                         Strategy  

package test.behavioural.designPattern;
interface Country {
void currency();
}
class Asian implements Country {
@Override
public void currency() {
System.out.println(" Currncy is INR");
}
}
class European implements Country {
@Override
public void currency() {
System.out.println(" Currency is EURO");
}
}
class CountryContext {
Country country;
public void setCountry(Country country) {
this.country = country;
}
public void currency() {
country.currency();
}
}
public class StrategyDesignPattern {
public static void main(String args[]) {
CountryContext countryContext = new CountryContext();
countryContext.setCountry(new Asian());
countryContext.currency();
countryContext.setCountry(new European());
countryContext.currency();
}
}
  

                         Observer

package test.behavioural.designPattern;

import java.util.ArrayList;

import java.util.List;

class NasdaqStock {

private int stockPrice;

List<StockExchange> stockExchangeList = new ArrayList<StockExchange>();

public void setStockPrice(int stockPrice) {

this.stockPrice = stockPrice;

notifyOtherExchanges();

}

public int getStockPrice() {

return stockPrice;

}

void notifyOtherExchanges() {

for (StockExchange s : stockExchangeList) {

s.getStockValue();

}

}

public void attach(StockExchange stockExchange) {

stockExchangeList.add(stockExchange);

}

}

abstract class StockExchange {

NasdaqStock nasdaqStock;

abstract void getStockValue();

}

class NSE extends StockExchange {

NSE(NasdaqStock nasdaqStock) {

this.nasdaqStock = nasdaqStock;

this.nasdaqStock.attach(this);

}

@Override

void getStockValue() {

System.out.println(" Value  at NSE after change at Nasdaq is "

+ this.nasdaqStock.getStockPrice());

}

}

class BSE extends StockExchange {

BSE(NasdaqStock nasdaqStock) {

this.nasdaqStock = nasdaqStock;

this.nasdaqStock.attach(this);

}

@Override

void getStockValue() {

System.out.println(" Value at BSE after change at Nasdaq is "

+ this.nasdaqStock.getStockPrice());

}

}

public class ObserverPatternSample {

public static void main(String args[]) {

NasdaqStock nasdaqStock = new NasdaqStock();

new BSE(nasdaqStock);

new NSE(nasdaqStock);

nasdaqStock.setStockPrice(100);

nasdaqStock.setStockPrice(5000);

}

}

                         Chain of Responsibility