question: @ Override public void accept ( Object source , Throwable t ) { if ( t != null ) { Executable . this . setLastError ( t ) ; cleanup ( ) ; } else if ( job . getCurrentState ( ) == Job . State . RUNNING && ( source == userScheduler || source == userThreads ) && ! hasActiveTasks ( ) ) { } notifyCompleter ( ) ; }
target:  Handler invoked by userThreads, userScheduler, and controlScheduler, upon handling an uncaught exception from a user task or when they  have completed all the tasks.