Android : Initiating a method only once

So this is probably a very basic question, but I couldn't find an answer for it that has worked for me. I have a method "notificationsetter()" which starts an alarm for displaying a notification and goes off every 24hrs. The problem is, I have to call the method only once, because if I use it at a time AFTER the alarm has gone off, the notification appears immediately (for example, alarm is set to 7AM, I use the method 10AM, the notification appears immediately at 10AM).

So I created this code in my MainActivity which is in onCreate():

boolean notificationtrue = false;
    if(notificationtrue==false) {
        notificationsetter();
        notificationtrue = false;

    }

So the code "should" call the method once, and then, as notificationtrue is always set to true, it is never called again. The problem here is, notificationtrue is displayed gray and android studio says:

"The value false assigned to notificationtrue is never used"

That means, my code won't work. Is there another way to call the method only once?