question: @ Override public void start ( ) { for ( int i = 0 ; i < threadCount ; ++ i ) { Set < SystemStreamPartition > threadSsps = new HashSet < SystemStreamPartition > ( ) ; for ( SystemStreamPartition ssp : ssps ) { if ( Math . abs ( ssp . hashCode ( ) ) % threadCount == i ) { threadSsps . add ( ssp ) ; } } Thread thread = new Thread ( new MockSystemConsumerRunnable ( threadSsps ) , "MockSystemConsumer-" + i ) ; thread . setDaemon ( true ) ; threads . add ( thread ) ; thread . start ( ) ; } }
target:  Assign SystemStreamPartitions to all of the threads, and start them up to begin simulating consuming messages.