Adapter Design Pattern
Adapter pattern works as a bridge between two incompatible interfaces.
This type of design pattern comes under structural pattern.
This pattern involves a single class which is responsible to join functionalities of independent or incompatile interfaces.
A real life example could be a case of card reader which acts as an adapter between memory card and a laptop.
We plug in the memory card into card reader and card reader into the laptop so that the memory card can be read via laptop.
Below is the diagram of an example for Adapter Design Pattern.
Step 1. Create interfaces for Media Player and Advanced Media Player.
MediaPlayer.java
public interface MediaPlayer{ public void play(String audioType, String filename); }
AdvancedMedia.java
public interface AdvancedMediaPlayer{ public void playVlc(String filename); public void playMp4(String filename); }
Step 2. Create Concrete classes implementing AdvancedMediaPlayer.
VlcPlayer.java
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 } }
Mp4Player.java
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); } }
Step 3. Create Adapter Class implementing the MediaPlayer interface.
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); } } }
Step 4. Create concrete class implementing MediaPlayer interface.
AudioPlayer.java
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"); } } }
Step 5.
Use the AudioPlayer to play different types of audio formats.
AdapterPatternDemo.java
public class AdapterPatternDemo { 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"); } }