// called under "this" lock
 @Override
 public synchronized Alert getAlertByAlertUid(String alertUid) {
   for (AlertGroup alertGroup : alertGroupList) {
     for (Alert alert : alertGroup.alertsInGroupList) {
       if (alert.getAlertUid().equals(alertUid)) {
         return alert;
       }
     }
   }
   return null;
 }