question: public boolean deregisterServiceProvider ( Object provider ) { Object oprovider = map . get ( provider . getClass ( ) ) ; if ( provider == oprovider ) { map . remove ( provider . getClass ( ) ) ; poset . remove ( provider ) ; if ( provider instanceof RegisterableService ) { RegisterableService rs = ( RegisterableService ) provider ; rs . onDeregistration ( registry , category ) ; } return true ; } return false ; }
target:  If the provider was not previously registered, do nothing.