设计模式探索——适配器模式

适配器模式（Adapter Pattern）是作为两个不兼容的接口之间的桥梁。这种类型的设计模式属于结构型模式，它结合了两个独立接口的功能。

UML图

MediaPlayer 接口和一个实现了 MediaPlayer 接口的实体类 AudioPlayer。默认情况下，AudioPlayer 可以播放 mp3 格式的音频文件。

接口 AdvancedMediaPlayer 和实现了 AdvancedMediaPlayer 接口的实体类。该类可以播放 vlc 和 mp4 格式的文件。

我们想要让 AudioPlayer 播放其他格式的音频文件。为了实现这个功能，我们需要创建一个实现了 MediaPlayer 接口的适配器类 MediaAdapter，并使用 AdvancedMediaPlayer 对象来播放所需的格式

1.创建接口

public interface MediaPalyer{
    public void play(String audoType,String fileName);
}


public interface AdvancedMediaPalyer{
    public void playVlc(String fileName);
    public void playMap4(String fileName);
}

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2.创建实现了AdvancedMediaPlayer接口的实体类

public VlcPlayer implements AdvancedMediaPlayer{
    @Override
    public void playVlc(String fileName){
        System.out.println("Playing vlc file Name:"+fielName);
    }

    @Override
    public void playMp4(String fileName){
        //不做什么
    }
}

public Mp4Player implements AdvancedMediaPlayer{
    @Override
    public void playVlc(String fileName){
        //不做什么
    }

    @Override 
    public void playMp4(String fileName){
        system.out.println("Palying mp4 fiel name:"+fileName);
    }
}
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3.创建实现了MediaPlayer接口的适配器

public class MediaAdapter implements MediaPlayer{
    AdvancedMediaPlayer advancedMusicPlayer;
    public MediaAdapter(String audioType){
        if(audioType.equalsIgnoreCase("vlc")){
            advancedMediaPlayer = 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);
        }

    }
}
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4.实现了MediaPlayer接口的实体类

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音乐支持
        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");
        }
    }
}
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5.实现操作

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");
    }

}
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