public synchronized void checkInGenerator(String serverId)
public synchronized void checkInGenerator(int serverId)
   public synchronized void checkInGenerator(String serverId)   {      Holder h = (Holder)holders.get(serverId);      if (h == null)      {         throw new IllegalArgumentException("Cannot find generator for serverid:" + serverId);      }      h.refCount--;      if (h.refCount == 0)      {         holders.remove(serverId);         log.debug("checked in and removed MessageIdGenerator for " + serverId);      }      else      {         log.debug("checked in MessageIdGenerator for " + serverId +                   ", reference count is " + h.refCount);      }   }