code: private RPCBatchRequestSender getBatchRequestSender()
  	{
  		RPCBatchRequestSender sender = null;
  
  		// test the last sender we have in the list
  		if( !batchRequestSenders.isEmpty() )
  		{
  			sender = batchRequestSenders.get( batchRequestSenders.size() - 1 );
  			if( sender.canAddRequest() )
  				return sender;
  		}
  
  		// otherwise, create a new one
  		sender = new RPCBatchRequestSender();
  		sender.init( baseUrl, batchSenderCallback );
  		batchRequestSenders.add( sender );
  
  		return sender;
  	}
docs: retrieve a batch request sender that is OK for adding requests