适配器模式

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。

比如：
读卡器是作为内存卡和笔记本之间的适配器。您将内存卡插入读卡器，再将读卡器插入笔记本，这样就可以通过笔记本来读取内存卡。

示例图示

image.png

代码源于菜鸟教程

示例代码

/**
 * 适配器模式
 */
public class Test implements Cloneable {
    public static void main(String[] args) throws CloneNotSupportedException  {
        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");
    }

}

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("播放VLC文件： "+ fileName);
    }

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

class Mp4Player implements AdvancedMediaPlayer{

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

    @Override
    public void playMp4(String fileName) {
        System.out.println("播放MP4文件： "+ fileName);
    }
}

/**
 * 适配器
 */
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);
        }
    }
}

/**
 * 播放器
 */
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("播放MP3文件： "+ 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("未支持的音频格式： "+ audioType);
        }
    }
}