FACADE PATTERNS AND ADAPTER PATTERN

FACADE PATTERN

Facade pattern hides the complexities of the system and provides an interface to the client using which the client can access the system. This type of design pattern comes under structural pattern as this pattern adds an interface to existing system to hide its complexities.

This pattern involves a single class which provides simplified methods required by client and delegates calls to methods of existing system classes.

public interface Shape {
   void draw();
}
public class Rectangle implements Shape {

   @Override
   public void draw() {
      System.out.println("Rectangle::draw()");
   }
}
public class Square implements Shape {

   @Override
   public void draw() {
      System.out.println("Square::draw()");
   }
}
public class Circle implements Shape {

   @Override
   public void draw() {
      System.out.println("Circle::draw()");
   }
}
public class ShapeMaker {
   private Shape circle;
   private Shape rectangle;
   private Shape square;

   public ShapeMaker() {
      circle = new Circle();
      rectangle = new Rectangle();
      square = new Square();
   }

   public void drawCircle(){
      circle.draw();
   }
   public void drawRectangle(){
      rectangle.draw();
   }
   public void drawSquare(){
      square.draw();
   }
}
public class FacadePatternDemo {
   public static void main(String[] args) {
      ShapeMaker shapeMaker = new ShapeMaker();

      shapeMaker.drawCircle();
      shapeMaker.drawRectangle();
      shapeMaker.drawSquare();		
   }
}

THE OUTPUT

Circle::draw()
Rectangle::draw()
Square::draw()

ADAPTER PATTERN

Adapter pattern works as a bridge between two incompatible interfaces. This type of design pattern comes under structural pattern as this pattern combines the capability of two independent interfaces.

This pattern involves a single class which is responsible to join functionalities of independent or incompatible interfaces. A real life example could be a case of card reader which acts as an adapter between memory card and a laptop. You plugin the memory card into card reader and card reader into the laptop so that memory card can be read via laptop.

Let’s take an example:
You are working in an office with an old coffee machine that dispenses two different coffee flavours. However, the new boss wants to add a new coffee machine with a touchscreen that can also connect to the old coffee machine. Complete the provided code to add an adapter so that the new touchscreen will to work with the old coffee machine.

the code will be as follows

//CoffeeMachineInterface.java
public interface CoffeeMachineInterface {
 public void chooseFirstSelection();
 public void chooseSecondSelection();
}
//OldCoffeeMachine.java
public class OldCoffeeMachine {
public void selectA() {
  System.out.println(“A - Selected”);
 }
 Public void selectB() {
  System.out.println(“B - Selected”);
 }
}
//CoffeeTouchscreenAdapter.java
public class CoffeeTouchscreenAdapter implements CoffeeMachineInterface {
OldCofffeeMachine theMachine;
public CoffeeTouchscreenAdapter(OldCoffeeMachine newMachine) {
  theMachine = newMachine;
 }
 
 public void chooseFirstSelection() {
  theMachine.selectA();
 }
 
 public void chooseSecondSelection() {
  theMachine.selectB();
}
}

you can also refer this great tutorial on adapter pattern by tutorialspoint

Design Patterns - Adapter Pattern

the code used here is

public interface MediaPlayer {
   public void play(String audioType, String fileName);
}
public interface AdvancedMediaPlayer { 
   public void playVlc(String fileName);
   public void playMp4(String fileName);
}

public 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
   }
}

public 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 MediaAdapter implements MediaPlayer {
AdvancedMediaPlayer advancedMusicPlayer;
public MediaAdapter(String audioType){
   
      if(audioType.equalsIgnoreCase("vlc") ){
         advancedMusicPlayer = new VlcPlayer();   
         
      }else if (audioType.equalsIgnoreCase("mp4")){
         advancedMusicPlayer = new Mp4Player();
      } 
   }
@Override
   public void play(String audioType, String fileName) {
   
      if(audioType.equalsIgnoreCase("vlc")){
         advancedMusicPlayer.playVlc(fileName);
      }
      else if(audioType.equalsIgnoreCase("mp4")){
         advancedMusicPlayer.playMp4(fileName);
      }
   }
}
public 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");
      }
   }   
}
public class adapterpat {
   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");
   }
}
//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");
      }
   }   
}
public class adapterpat {
   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");
   }
}