Java适配器模式

默认的MediaPlayer接口只能播放mp3格式的音乐，然而我们现在想播放vlc和mp4格式的音乐，

怎么做呢？

这里我们引入AdvancedMediaPlayer接口，AdvancedMediaPlayer接口可以播放vlc和mp4格式的音乐。

怎么将AdvancedMediaPlayer接口“适配”到MediaPlayer接口中呢？

这里引入MediaAdapter类，这个类用来适配vlc和mp4格式的音乐

最后用AudioPlayer类实现MediaPlayer接口,适配的工作交给MediaAdapter类

 类结构图如下：

VlcPlayer.java

package com.advance.adapter;

/**
 * @Auther: 谷天乐
 * @Date: 2018/9/20 22:58
 * @Description:
 */


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) {
        //什么也不做
    }
}

Mp4Player.java

package com.advance.adapter;

/**
 * @Auther: 谷天乐
 * @Date: 2018/9/20 22:58
 * @Description:
 */

public class Mp4Player implements AdvancedMediaPlayer{

    @Override
    public void playVlc(String fileName) {
        //什么也不做
    }

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

MediaPlayer.java

package com.advance.adapter;

/**
 * @Auther: 谷天乐
 * @Date: 2018/9/20 22:57
 * @Description:
 */
public interface MediaPlayer {
    public void play(String audioType, String fileName);
}

MediaAdapter.java

package com.advance.adapter;

/**
 * @Auther: 谷天乐
 * @Date: 2018/9/20 22:58
 * @Description:
 */


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);
        }
    }
}

AudioPlayer.java

package com.advance.adapter;

/**
 * @Auther: 谷天乐
 * @Date: 2018/9/20 22:59
 * @Description:
 */


public class AudioPlayer implements MediaPlayer {

    MediaAdapter mediaAdapter;

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

        //播放 mp3 音乐文件的内置支持
        if(audioType.equalsIgnoreCase("mp3")){
            System.out.println("Playing mp3 file. Name: "+ fileName);
        }
        //mediaAdapter 提供了播放其他文件格式的支持
        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");
        }
    }
}

AdvancedMediaPlayer.java

package com.advance.adapter;

/**
 * @Auther: 谷天乐
 * @Date: 2018/9/20 22:57
 * @Description:
 */

public interface AdvancedMediaPlayer {
    public void playVlc(String fileName);
    public void playMp4(String fileName);
}

AdapterPatternDemo.java

package com.advance.adapter;

/**
 * @Auther: 谷天乐
 * @Date: 2018/9/20 22:59
 * @Description:
 */

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");
    }
}

运行结果

Playing mp3 file. Name: beyond the horizon.mp3
Playing mp4 file. Name: alone.mp4
Playing vlc file. Name: far far away.vlc
Invalid media. avi format not supported