用java 写一个AudioFocusManager

以下是一个简单的Java类，用于模拟AudioFocusManager的基本功能：

import java.util.ArrayList;
import java.util.List;

public class AudioFocusManager {
    
    private List<AudioFocusChangeListener> listeners;
    private int focusState;
    public static final int AUDIOFOCUS_GAIN = 1;
    public static final int AUDIOFOCUS_LOSS = -1;
    
    public AudioFocusManager() {
        listeners = new ArrayList<>();
        focusState = 0;
    }
    
    public void requestAudioFocus(AudioFocusChangeListener listener) {
        if (listeners.contains(listener)) {
            return;
        }
        listeners.add(listener);
        if (focusState != AUDIOFOCUS_GAIN) {
            focusState = AUDIOFOCUS_GAIN;
            listener.onAudioFocusChange(focusState);
        }
    }
    
    public void abandonAudioFocus(AudioFocusChangeListener listener) {
        if (!listeners.contains(listener)) {
            return;
        }
        listeners.remove(listener);
        if (listeners.isEmpty() && focusState != AUDIOFOCUS_LOSS) {
            focusState = AUDIOFOCUS_LOSS;
            for (AudioFocusChangeListener l : listeners) {
                l.onAudioFocusChange(focusState);
            }
        }
    }
    
    public interface AudioFocusChangeListener {
        void onAudioFocusChange(int focusChange);
    }
}

这个AudioFocusManager类有一个listeners列表，用于存储已注册的AudioFocusChangeListener。requestAudioFocus方法用于注册一个新的监听器，如果当前没有其他监听器，则将焦点状态设置为AUDIOFOCUS_GAIN，并调用onAudioFocusChange方法通知监听器。abandonAudioFocus方法用于取消一个已注册的监听器，如果listeners列表为空，则将焦点状态设置为AUDIOFOCUS_LOSS，并通知其他监听器。接口AudioFocusChangeListener定义了一个onAudioFocusChange方法，用于接收焦点状态的更改。