private void sendPoisonPills() {
        for (int i = 0; i < numWorkers; i++) {
            workUnits.add(new WorkUnitWrapper<T>(null));
        }
    }
private void sendPoisonPills ( ) { for ( int i = 0 ; i < numWorkers ; i ++ ) { workUnits . add ( new WorkUnitWrapper < T > ( null ) ) ; } }
Send poison pills to workers.