@@ -3,6 +3,8 @@
 import java.util.*;
 import javaxt.utils.Value;
 import javaxt.express.utils.DateUtils;
+import java.util.concurrent.atomic.AtomicBoolean;
+
 
 //******************************************************************************
 //** NotificationService
@@ -14,8 +16,9 @@
 
 public class NotificationService {
 
-private static List events = null;
-private static List<Listener> listeners;
+private static List events = new LinkedList();
+private static List<Listener> listeners = new LinkedList();
+private static AtomicBoolean isRunning = new AtomicBoolean(false);
 
 
 //**************************************************************************
@@ -27,7 +30,7 @@ public class NotificationService {
 * @param data Additional information related to the event (e.g. User ID)
 */
 public static void notify(String event, String model, Value data){
-if (events==null) return;
+if (!isRunning.get()) return;
 
 if (data==null) data = new Value(null);
 
@@ -49,15 +52,14 @@ public static void start(){
 }
 
 public static void start(int numThreads){
-if (events!=null) return;
+if (isRunning.get()) return;
 
-listeners = new LinkedList();
 
-events = new LinkedList();
 for (int i=0; i<numThreads; i++){
 Thread thread = new Thread(new NotificationProcessor());
 thread.start();
 }
+isRunning.set(true);
 }
 
 
@@ -78,16 +80,22 @@ public static void stop(){
 events.add(0, null);
 events.notify();
 }
-events = null;
 }
 
 
 //**************************************************************************
 //** addListener
 //**************************************************************************
-/** Used to add an event listener that will consume events
+/** Used to add an event listener that will consume events. Example:
+<pre>
+NotificationService.addListener((
+String event, String model, javaxt.utils.Value data, long timestamp)->{
+console.log(event, model, data);
+});
+</pre>
 */
 public static void addListener(Listener listener){
+if (!isRunning.get()) return;
 synchronized(listeners){
 listeners.add(listener);
 listeners.notify();
@@ -139,6 +147,7 @@ public void run() {
 
 }
 else{
+isRunning.set(false);
 return;
 }
 }