设计模式- 适配器

场景

假设我们有一个旧的音频播放器类 AudioPlayer，它只能播放 .mp3 文件。现在我们需要让它也能播放 .mp4 和 .vlc 格式的文件。

1. 定义媒体播放器接口和高级媒体播放器接口

java

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// 普通媒体播放器接口 public interface MediaPlayer { void play(String audioType, String fileName); } // 高级媒体播放器接口 public interface AdvancedMediaPlayer { void playVlc(String fileName); void playMp4(String fileName); }

2. 实现高级媒体播放器接口

java

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// VLC播放器实现 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) { // 不做任何事 } } // MP4播放器实现 public class Mp4Player implements AdvancedMediaPlayer { @Override public void playVlc(String fileName) { // 不做任何事 } @Override public void playMp4(String fileName) { System.out.println("Playing mp4 file. Name: " + fileName); } }

3. 创建适配器类实现 MediaPlayer 接口

java

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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); } } }

4. 创建 AudioPlayer 实现 MediaPlayer 接口

java

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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); } // 适配器提供对vlc和mp4文件的支持 else if (audioType.equalsIgnoreCase("vlc") || audioType.equalsIgnoreCase("mp4")) { mediaAdapter = new MediaAdapter(audioType); mediaAdapter.play(audioType, fileName); } // 不支持的格式 else { System.out.println("Invalid media. " + audioType + " format not supported"); } } }

5. 使用 AudioPlayer

java

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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"); } }

输出结果

yaml

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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