public void registerSettingChangeListener(String key,SettingChangeListener listener){
  String realKey="config." + key;
  List<SettingChangeListener> list=listeners.get(realKey);
  if (list == null) {
    list=new ArrayList<SettingChangeListener>();
    listeners.put(realKey,list);
  }
  list.add(listener);
}

public void registerSettingChangeListener ( String key , SettingChangeListener listener ) { String realKey = "config." + key ; List < SettingChangeListener > list = listeners . get ( realKey ) ; if ( list == null ) { list = new ArrayList < SettingChangeListener > ( ) ; listeners . put ( realKey , list ) ; } list . add ( listener ) ; }
register a change listener for a specific configuration change .
