I know it might be something very easy but is just something that I don’t know.

In my code when I write "FirebaseInstanceId" or "getInstanceId()", they are crossed by a line in the middle and the code doesn’t work. If there is someone to explain me I’d be very thankful.

        FirebaseInstanceId.getInstance().getInstanceId().addOnCompleteListener(task -> {
        if (task.isSuccessful() && task.getResult() != null) {
        sendFCMTokenDatabase(task.getResult().getToken());
        }
    });

Source: Android Studio Questions