public void setRepeatingAlarm(){
    Intent intent = new Intent(this, TimeAlarm.class);
    PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0,intent, PendingIntent.FLAG_UPDATE_CURRENT);
    am.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), (5 * 1000), pendingIntent);
}

public void onReceive(Context context, Intent intent) {

    nm = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
    CharSequence from = "Homework";
    CharSequence message = "test"+ MainActivity.arraytest[x2]+ x2;
    x2 +=1;
    PendingIntent contentIntent = PendingIntent.getActivity(context, 0,new Intent(context,TimeAlarm.class), 0);
    Notification notif = new Notification(R.drawable.ic_launcher,"Update", System.currentTimeMillis());
    notif.setLatestEventInfo(context, from, message, contentIntent);
    nm.notify(notify_id, notif);
}