Added Adapter Pattern

Author: sourabhvarshney111

Design Patterns/Adapter Pattern/AdapterPattern.java

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+/*
+Reference: https://www.tutorialspoint.com/design_pattern/adapter_pattern.htm
+ */
+
+interface MediaPlayer {
+   public void play(String audioType, String fileName);
+}
+
+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);      
+   }
+}
+
+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);
+      }
+   }
+}
+
+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 AdapterPattern {
+   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");
+   }
+}

Design Patterns/Adapter Pattern/README.md

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+### Adapter Pattern
+
+### Introduction
+
+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.
+
+### Advantages
+
+- The code is reusable and flexible.
+- Clean code — because the client/context does not use a different interface in each concrete class and can use polymorphism to swap between different adapters.
+
+### Disadvantages
+
+- Cannot override methods in Adaptee.
+- Cannot reuse Adapter with subclasses of Target.
+- Adapter and Adaptee are different objects (Need to maintain relation between Adaptee and his Adapter).
+
+### Programming
+
+- Here, we have a MediaPlayer interface and a concrete class AudioPlayer implementing the MediaPlayer interface. AudioPlayer can play mp3 format audio files by default.
+
+- We are having another interface AdvancedMediaPlayer and concrete classes implementing the AdvancedMediaPlayer interface. These classes can play vlc and mp4 format files.
+
+- We want to make AudioPlayer to play other formats as well. To attain this, we have created an adapter class MediaAdapter which implements the MediaPlayer interface and uses AdvancedMediaPlayer objects to play the required format.
+
+- AudioPlayer uses the adapter class MediaAdapter passing it the desired audio type without knowing the actual class which can play the desired format. AdapterPattern, our demo class will use AudioPlayer class to play various formats.