AdapterExample.java

package com.javaexperiments;

/**
 * An illustration of adapter design pattern
 */
public class AdapterExample {

    public static void main(String[] args) {

        /**
         * Using AudioPlayer for playing different audio formats
         */
        AudioPlayer audioPlayer = new AudioPlayer();

        audioPlayer.play("mp3", "Waiting For Love.mp3");
        audioPlayer.play("vlc", "Wake Me Up.vlc");
        audioPlayer.play("mp4", "Summer of 69.mp4");
        audioPlayer.play("wma", "Lady.wma");
    }
}

interface MediaPlayer {
    void play(String audioType, String fileName);
}

interface AdvancedMediaPlayer {
    void playVlc(String fileName);
    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);
    }
}

/**
 * The Adapter will be named MediaAdapter and it must implement
 * the MediaPlayer interface. The FormatAdapter class must have a
 * reference to AdvancedMediaPlayer, the incompatible interface.
 */
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");
        }
    }
}