public static function getInstance()
 {
     if (self::$Instance === null) {
         self::$Instance = new SharedFileListener();
     }
     return self::$Instance;
 }
 public function notifySharingStopped(IShareable $object)
 {
     if (!$object instanceof IShareableFile) {
         throw new EyeInvalidClassException('$object must be an instance of IShareableFile.');
     }
     $object->removeFileListener(SharedFileListener::getInstance());
 }