Are these methods getNewId() & fetchIdsInReserve() thread safe ?

public final class IdManager {

    private static final int NO_OF_USERIDS_TO_KEEP_IN_RESERVE = 200;

    private static final AtomicInteger regstrdUserIdsCount_Cached = new AtomicInteger(100);
    private static int noOfUserIdsInReserveCurrently = 0;

    public static int getNewId(){                   
          synchronized(IdManager.class){
              if (noOfUserIdsInReserveCurrently <= 20)
                      fetchIdsInReserve();    

              noOfUserIdsInReserveCurrently--;
          }
          return regstrdUserIdsCount_Cached.incrementAndGet();
    }


    private static synchronized void fetchIdsInReserve(){
        int reservedInDBTill = DBCountersReader.readCounterFromDB(....); // read column from DB 

        if (noOfUserIdsInReserveCurrently + regstrdUserIdsCount_Cached.get() != reservedInDBTill) throw new Exception("Unreserved ids alloted by app before reserving from DB");

        if (DBUpdater.incrementCounter(....)) //if write back to DB is successful
              noOfUserIdsInReserveCurrently += NO_OF_USERIDS_TO_KEEP_IN_RESERVE;
    }

}