private static void addNotificationDetail(Mail mail) { List<NotificationDetail> notificationDetails = null; if (mail.getNotification().getNotificationDetails() == null) { notificationDetails = new ArrayList<>(); mail.getNotification().setNotificationDetails(notificationDetails); } else { notificationDetails = mail.getNotification().getNotificationDetails(); } for (String recipient : mail.getReceipts()) { NotificationDetail notificationDetail = new NotificationDetail(); notificationDetail.setEmailAddress(recipient); notificationDetail.setId(System.currentTimeMillis()); notificationDetails.add(notificationDetail); mail.getNotification().setNotificationDetails(notificationDetails); } }