Java 8 streams maps with parameters

Question

I have this couple of functions and I would like to know if it is possible to pass the parameter deviceEvent.hasAlarm() to .map(this::sendSMS)

private void processAlarm (DeviceEvent deviceEvent)  {

        notificationsWithGuardians.stream()
                    .filter (notification -> notification.getLevels().contains(deviceEvent.getDeviceMessage().getLevel()))
                    .map(this::sendSMS)
                    .map(this::sendEmail);

    }

    private DeviceAlarmNotification sendSMS (DeviceAlarmNotification notification, DeviceEvent deviceEvent)  {

        if (deviceEvent.hasAlarm()) {       

        }

        return notification;

    }

Answer 1

Use a lambda instead of the method reference.

// ...
.map(n -> sendSMS(n, deviceEvent))
// ...

Answer 2

... I would like to know if it is possible to pass the parameter deviceEvent.hasAlarm() to this::sendSMS

No, is not possible. When using method reference you can pass only one argument ( docs ).

But from the code you provided there is no need for such thing. Why to check deviceEvent for every notification when it is not changing? Better way:

if(deviceEvent.hasAlarm()) {
  notificationsWithGuardians.stream().filter( ...
}

Anyway, if you really want, this can be a solution:

notificationsWithGuardians.stream()
                .filter (notification -> notification.getLevels().contains(deviceEvent.getDeviceMessage().getLevel()))
                .map(notification -> Pair.of(notification, deviceEvent))
                .peek(this::sendSMS)
                .forEach(this::sendEmail);

 private void sendSMS(Pair<DeviceAlarmNotification, DeviceEvent> pair)  { ... }

Answer 3

如果引用方法在同一类中，如何创建一个类或成员变量并为其赋值并在提供的引用方法中重用