public V putIfAbsent ( K putKey , V putValue ) { V existingValue = this . store . putIfAbsent ( putKey , putValue ) ; if ( existingValue == null ) { this . notificationExecutor . firePutNotification ( this . listeners . iterator ( ) , putKey , putValue ) ; } return existingValue ; }
Add the given entry into the registry under the specified key but only if the key is not already registered .