六、结构型 适配器模式（Adapter Pattern）

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。

1. 高级媒体播放器

/**
 * 高级媒体播放器接口
 *
 * @author 吴尚慧
 * @since 2022/6/21 11:43
 */
public interface AdvancedMediaPlayer {

    public void playVlc(String fileName);

    public void playMp4(String fileName);
}
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/**
 * Mp4 播放器
 * 
 * @author 吴尚慧
 * @since 2022/6/21 11:44
 */
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);
    }
}
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/**
 * Vlc 播放器
 * 
 * @author 吴尚慧
 * @since 2022/6/21 11:44
 */
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
    }
}
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播放器统一的入口

/**
 * 媒体播放器接口
 *
 * @author 吴尚慧
 * @since 2022/6/21 11:41
 */
public interface MediaPlayer {

    /**
     * 播放
     *
     * @param audioType 音频格式
     * @param fileName 文件名
     */
    public void play(String audioType, String fileName);
}
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写一个适配器类，来适配高级媒体播放器

/**
 * 高级媒体适配器类
 * 
 * @author 吴尚慧
 * @since 2022/6/21 11:45
 */
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);
        }
    }
}
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播放器入口

/**
 * 声音播放器
 * 
 * @author 吴尚慧
 * @since 2022/6/21 11:46
 */
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");
        }
    }
}
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测试类

/**
 * 测试类
 *
 * @author 吴尚慧
 * @since 2022/6/21 11:46
 */
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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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
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参考：
https://www.runoob.com/design-pattern/design-pattern-intro.html