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

1package com.advance.adapter;
2
3/**
4 * @Auther: 谷天乐
5 * @Date: 2018/9/20 22:58
6 * @Description:
7 */
8
9
10public class VlcPlayer implements AdvancedMediaPlayer{
11    @Override
12    public void playVlc(String fileName) {
13        System.out.println("Playing vlc file. Name: "+ fileName);
14    }
15
16    @Override
17    public void playMp4(String fileName) {
18        //什么也不做
19    }
20}

Mp4Player.java

1package com.advance.adapter;
2
3/**
4 * @Auther: 谷天乐
5 * @Date: 2018/9/20 22:58
6 * @Description:
7 */
8
9public class Mp4Player implements AdvancedMediaPlayer{
10
11    @Override
12    public void playVlc(String fileName) {
13        //什么也不做
14    }
15
16    @Override
17    public void playMp4(String fileName) {
18        System.out.println("Playing mp4 file. Name: "+ fileName);
19    }
20}

MediaPlayer.java

1package com.advance.adapter;
2
3/**
4 * @Auther: 谷天乐
5 * @Date: 2018/9/20 22:57
6 * @Description:
7 */
8public interface MediaPlayer {
9    public void play(String audioType, String fileName);
10}

MediaAdapter.java

1package com.advance.adapter;
2
3/**
4 * @Auther: 谷天乐
5 * @Date: 2018/9/20 22:58
6 * @Description:
7 */
8
9
10public class MediaAdapter implements MediaPlayer {
11
12    AdvancedMediaPlayer advancedMusicPlayer;
13
14    public MediaAdapter(String audioType){
15        if(audioType.equalsIgnoreCase("vlc") ){
16            advancedMusicPlayer = new VlcPlayer();
17        } else if (audioType.equalsIgnoreCase("mp4")){
18            advancedMusicPlayer = new Mp4Player();
19        }
20    }
21
22    @Override
23    public void play(String audioType, String fileName) {
24        if(audioType.equalsIgnoreCase("vlc")){
25            advancedMusicPlayer.playVlc(fileName);
26        }else if(audioType.equalsIgnoreCase("mp4")){
27            advancedMusicPlayer.playMp4(fileName);
28        }
29    }
30}

AudioPlayer.java

1package com.advance.adapter;
2
3/**
4 * @Auther: 谷天乐
5 * @Date: 2018/9/20 22:59
6 * @Description:
7 */
8
9
10public class AudioPlayer implements MediaPlayer {
11
12    MediaAdapter mediaAdapter;
13
14    @Override
15    public void play(String audioType, String fileName) {
16
17        //播放 mp3 音乐文件的内置支持
18        if(audioType.equalsIgnoreCase("mp3")){
19            System.out.println("Playing mp3 file. Name: "+ fileName);
20        }
21        //mediaAdapter 提供了播放其他文件格式的支持
22        else if(audioType.equalsIgnoreCase("vlc")
23                || audioType.equalsIgnoreCase("mp4")){
24            mediaAdapter = new MediaAdapter(audioType);
25            mediaAdapter.play(audioType, fileName);
26        }else{
27            System.out.println("Invalid media. "+
28                    audioType + " format not supported");
29        }
30    }
31}

AdvancedMediaPlayer.java

1package com.advance.adapter;
2
3/**
4 * @Auther: 谷天乐
5 * @Date: 2018/9/20 22:57
6 * @Description:
7 */
8
9public interface AdvancedMediaPlayer {
10    public void playVlc(String fileName);
11    public void playMp4(String fileName);
12}

AdapterPatternDemo.java

1package com.advance.adapter;
2
3/**
4 * @Auther: 谷天乐
5 * @Date: 2018/9/20 22:59
6 * @Description:
7 */
8
9public class AdapterPatternDemo {
10    public static void main(String[] args) {
11        AudioPlayer audioPlayer = new AudioPlayer();
12
13        audioPlayer.play("mp3", "beyond the horizon.mp3");
14        audioPlayer.play("mp4", "alone.mp4");
15        audioPlayer.play("vlc", "far far away.vlc");
16        audioPlayer.play("avi", "mind me.avi");
17    }
18}

运行结果

1Playing mp3 file. Name: beyond the horizon.mp3
2Playing mp4 file. Name: alone.mp4
3Playing vlc file. Name: far far away.vlc
4Invalid media. avi format not supported