public static StorageListener useDBServer() {
   // assume in memory with some initial state
   if (singleton != null) {
     return (singleton);
   }
   try {
     singleton = (StorageListener) DBServer.initInMemory();
   } catch (Exception e) {
     ExceptionWindow.getExceptionWindow(e);
   }
   return (singleton);
 }
 public static StorageListener useDBServer(String dbName) {
   // assumed persistent
   if (singleton != null) {
     return (singleton);
   }
   try {
     singleton = (StorageListener) DBServer.init(dbName);
   } catch (Exception e) {
     ExceptionWindow.getExceptionWindow(e);
   }
   return (singleton);
 }