MessageIdGenerator gen = (MessageIdGenerator)generators.get(serverId); if (gen == null)
Holder h = (Holder)holders.get(serverId);  if (h == null)
   public synchronized MessageIdGenerator getGenerator(String serverId, ConnectionFactoryDelegate cf) throws JMSException   {      MessageIdGenerator gen = (MessageIdGenerator)generators.get(serverId);      if (gen == null)      {         gen = new MessageIdGenerator(cf, BLOCK_SIZE);         generators.put(serverId, gen);      }      return gen;   }