รบกวนผู้รู้หน่อยครับ android studio alarmmanager แก้การแจ้งเตือน

public void setAlarm() {
            alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
            alarmIntent = new Intent(MainActivity.this, AlarmReceiver.class);
            pendingIntent = PendingIntent.getBroadcast(MainActivity.this, 0, alarmIntent, 0);

            Calendar alarmStartTime = Calendar.getInstance();
            alarmStartTime.set(Calendar.HOUR_OF_DAY, 10);
            alarmStartTime.set(Calendar.MINUTE, 0);
            alarmStartTime.set(Calendar.SECOND, 0);
            alarmManager.set(AlarmManager.RTC_WAKEUP, alarmStartTime.getTimeInMillis(), pendingIntent);
    }