question: @ SuppressWarnings ( "unchecked" ) void addMaster ( final AbstractMasterTask master ) { if ( master == null ) throw new IllegalArgumentException ( ) ; if ( masters . putIfAbsent ( master . hashCode ( ) , master ) == null ) { masterCreateCount . incrementAndGet ( ) ; } }
target:  A new master task declares itself to this statistics object using this method. This allows the statistics object to report on the #of master tasks, their queue sizes, and the sizes of their sink queues.