diff --git a/src/main/java/net/floodlightcontroller/debugcounter/IDebugCounterService.java b/src/main/java/net/floodlightcontroller/debugcounter/IDebugCounterService.java
index dc98f05b726eebca61d134ffa16eb2a39499a646..20586a5a4463f50da28cf18b930e76f37ef368e6 100644
--- a/src/main/java/net/floodlightcontroller/debugcounter/IDebugCounterService.java
+++ b/src/main/java/net/floodlightcontroller/debugcounter/IDebugCounterService.java
@@ -43,7 +43,7 @@ public interface IDebugCounterService extends IFloodlightService {
 
     /**
      *  maximum levels of hierarchy
-     *  Example: moduleName/counterHierarchy
+     *  Example of moduleName/counterHierarchy:
      *           switch/00:00:00:00:01:02:03:04/pktin/drops where
      *           moduleName ==> "switch"  and
      *           counterHierarchy of 3 ==> "00:00:00:00:01:02:03:04/pktin/drops"
diff --git a/src/main/java/net/floodlightcontroller/debugevent/DebugEvent.java b/src/main/java/net/floodlightcontroller/debugevent/DebugEvent.java
index acfbb11bf2868976cd0867d3c61d120e63d41699..54218d6ed92f34d859ced9e3e5ee82593f7c04bc 100644
--- a/src/main/java/net/floodlightcontroller/debugevent/DebugEvent.java
+++ b/src/main/java/net/floodlightcontroller/debugevent/DebugEvent.java
@@ -106,8 +106,8 @@ public class DebugEvent implements IFloodlightModule, IDebugEventService {
      * A particular event type is accessed by directly indexing into the array
      * with the corresponding event-id.
      */
-    protected static DebugEventHistory[] allEvents =
-                          new DebugEventHistory[MAX_EVENTS];
+    protected DebugEventHistory[] allEvents =
+                    new DebugEventHistory[MAX_EVENTS];
 
     /**
      * Global storage for all event ids registered for a module. The map is indexed
@@ -199,8 +199,7 @@ public class DebugEvent implements IFloodlightModule, IDebugEventService {
 
         private boolean validEventId() {
             if (eventId < 0 || eventId >= MAX_EVENTS) {
-                log.error("Invalid eventId invoked");
-                return false;
+                throw new IllegalStateException();
             }
             return true;
         }
@@ -381,7 +380,7 @@ public class DebugEvent implements IFloodlightModule, IDebugEventService {
 
     @Override
     public List<DebugEventInfo> getModuleEventHistory(String moduleName) {
-        if (!moduleEvents.containsKey(moduleName)) return null;
+        if (!moduleEvents.containsKey(moduleName)) return Collections.emptyList();
         ArrayList<DebugEventInfo> moduleEventList = new ArrayList<DebugEventInfo>();
         for (int eventId : moduleEvents.get(moduleName).values()) {
             DebugEventHistory de = allEvents[eventId];
diff --git a/src/main/java/net/floodlightcontroller/debugevent/IDebugEventService.java b/src/main/java/net/floodlightcontroller/debugevent/IDebugEventService.java
index d870ac56e3da588a5ed5b4407ff07b6c03733507..4cffffc04660853d17b6f73cdaf645e810c7e3b8 100644
--- a/src/main/java/net/floodlightcontroller/debugevent/IDebugEventService.java
+++ b/src/main/java/net/floodlightcontroller/debugevent/IDebugEventService.java
@@ -136,7 +136,7 @@ public interface IDebugEventService extends IFloodlightService {
      * Get event history for all events registered for a given moduleName
      *
      * @return  a list of all event histories for all events registered for the
-     *          the module or null if there are no events for this module
+     *          the module or an empty list if there are no events for this module
      */
     public List<DebugEventInfo> getModuleEventHistory(String moduleName);
 
diff --git a/src/main/java/net/floodlightcontroller/debugevent/NullDebugEvent.java b/src/main/java/net/floodlightcontroller/debugevent/NullDebugEvent.java
index 42bf939d2fa2e39a6e8f7efe1f25235a21c403c6..4df4a8d6ad80ff48043eccf5085748bf699ded72 100644
--- a/src/main/java/net/floodlightcontroller/debugevent/NullDebugEvent.java
+++ b/src/main/java/net/floodlightcontroller/debugevent/NullDebugEvent.java
@@ -2,6 +2,7 @@ package net.floodlightcontroller.debugevent;
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -60,56 +61,47 @@ public class NullDebugEvent implements IFloodlightModule, IDebugEventService {
 
     @Override
     public boolean containsModuleEventName(String moduleName, String eventName) {
-        // TODO Auto-generated method stub
         return false;
     }
 
     @Override
     public boolean containsModuleName(String moduleName) {
-        // TODO Auto-generated method stub
         return false;
     }
 
     @Override
     public List<DebugEventInfo> getAllEventHistory() {
-        // TODO Auto-generated method stub
-        return null;
+        return Collections.emptyList();
     }
 
     @Override
     public List<DebugEventInfo> getModuleEventHistory(String param) {
-        // TODO Auto-generated method stub
-        return null;
+        return Collections.emptyList();
     }
 
     @Override
     public DebugEventInfo getSingleEventHistory(String moduleName, String eventName) {
-        // TODO Auto-generated method stub
         return null;
     }
 
     @Override
     public void resetAllEvents() {
-        // TODO Auto-generated method stub
 
     }
 
     @Override
     public void resetAllModuleEvents(String moduleName) {
-        // TODO Auto-generated method stub
 
     }
 
     @Override
     public void resetSingleEvent(String moduleName, String eventName) {
-        // TODO Auto-generated method stub
 
     }
 
     @Override
     public ArrayList<EventInfo> getEventList() {
-        // TODO Auto-generated method stub
-        return null;
+        return new ArrayList<EventInfo>();
     }
 
     @Override
@@ -125,13 +117,11 @@ public class NullDebugEvent implements IFloodlightModule, IDebugEventService {
 
         @Override
         public void updateEventNoFlush(Object event) {
-            // TODO Auto-generated method stub
 
         }
 
         @Override
         public void updateEventWithFlush(Object event) {
-            // TODO Auto-generated method stub
 
         }
 
diff --git a/src/test/java/net/floodlightcontroller/debugevent/DebugEventTest.java b/src/test/java/net/floodlightcontroller/debugevent/DebugEventTest.java
index a3ef8d91e0ec2d35b9e18506022615408efdff8b..1ceb278118a0f817093ebb7cb31093c82bd47cc0 100644
--- a/src/test/java/net/floodlightcontroller/debugevent/DebugEventTest.java
+++ b/src/test/java/net/floodlightcontroller/debugevent/DebugEventTest.java
@@ -53,20 +53,20 @@ public class DebugEventTest extends FloodlightTestCase {
         assertEquals(true, debugEvent.containsModuleEventName("dbgevtest","switchevent"));
         assertEquals(true, debugEvent.containsModuleEventName("dbgevtest","pktinevent"));
 
-        assertEquals(0, DebugEvent.allEvents[eventId1].eventBuffer.size());
-        assertEquals(0, DebugEvent.allEvents[eventId2].eventBuffer.size());
+        assertEquals(0, debugEvent.allEvents[eventId1].eventBuffer.size());
+        assertEquals(0, debugEvent.allEvents[eventId2].eventBuffer.size());
 
         // update is immediately flushed to global store
         event1.updateEventWithFlush(new SwitchyEvent(1L, "connected"));
-        assertEquals(1, DebugEvent.allEvents[eventId1].eventBuffer.size());
+        assertEquals(1, debugEvent.allEvents[eventId1].eventBuffer.size());
 
         // update is flushed only when flush is explicitly called
         event2.updateEventNoFlush(new PacketyEvent(1L, 24L));
-        assertEquals(0, DebugEvent.allEvents[eventId2].eventBuffer.size());
+        assertEquals(0, debugEvent.allEvents[eventId2].eventBuffer.size());
 
         debugEvent.flushEvents();
-        assertEquals(1, DebugEvent.allEvents[eventId1].eventBuffer.size());
-        assertEquals(1, DebugEvent.allEvents[eventId2].eventBuffer.size());
+        assertEquals(1, debugEvent.allEvents[eventId1].eventBuffer.size());
+        assertEquals(1, debugEvent.allEvents[eventId2].eventBuffer.size());
 
         DebugEventInfo de = debugEvent.getSingleEventHistory("dbgevtest","switchevent");
         assertEquals(1, de.events.size());