Index: /trunk/EventBenchCore/src/de/ugoe/cs/eventbench/data/Event.java
===================================================================
--- /trunk/EventBenchCore/src/de/ugoe/cs/eventbench/data/Event.java	(revision 335)
+++ /trunk/EventBenchCore/src/de/ugoe/cs/eventbench/data/Event.java	(revision 336)
@@ -96,14 +96,27 @@
 		if (other instanceof Event<?>) {
 			Event<?> otherEvent = (Event<?>) other;
-			if (target != null) {
-				return type.equals(otherEvent.type)
-						&& target.equals(otherEvent.target);
+			if (otherEvent.canEqual(this)) {
+				if (type != null && target != null) {
+					return type.equals(otherEvent.type)
+							&& target.equals(otherEvent.target);
+				} else if (type != null && target == null) {
+					return type.equals(otherEvent.type)
+							&& otherEvent.target == null;
+				} else if (type == null && target != null) {
+					return otherEvent.type == null
+							&& target.equals(otherEvent.target);
+				} else {
+					return otherEvent.type == null && otherEvent.target == null;
+				}
 			} else {
-				return type.equals(otherEvent.type)
-						&& otherEvent.target == null;
+				return false;
 			}
 		} else {
 			return false;
 		}
+	}
+
+	public boolean canEqual(Object other) {
+		return (other instanceof Event<?>);
 	}
 
@@ -216,5 +229,7 @@
 		int multiplier = 17;
 		int hash = 42;
-		hash = multiplier * hash + type.hashCode();
+		if (type != null) {
+			hash = multiplier * hash + type.hashCode();
+		}
 		if (target != null) {
 			hash = multiplier * hash + target.hashCode();
Index: /trunk/EventBenchCore/src/de/ugoe/cs/eventbench/data/ReplayableEvent.java
===================================================================
--- /trunk/EventBenchCore/src/de/ugoe/cs/eventbench/data/ReplayableEvent.java	(revision 335)
+++ /trunk/EventBenchCore/src/de/ugoe/cs/eventbench/data/ReplayableEvent.java	(revision 336)
@@ -1,4 +1,5 @@
 package de.ugoe.cs.eventbench.data;
 
+import java.security.InvalidParameterException;
 import java.util.LinkedList;
 import java.util.List;
@@ -73,6 +74,11 @@
 	 * @param replayable
 	 *            element that is added to the sequence
+	 * @throws InvalidParameterException
+	 *             thrown is replayable is null
 	 */
 	public void addReplayEvent(T replayable) {
+		if (replayable == null) {
+			throw new InvalidParameterException("replayble must not be null");
+		}
 		replayEvents.add(replayable);
 	}
@@ -85,6 +91,12 @@
 	 * @param generatedReplaySeq
 	 *            {@link List} that is added to the sequence
+	 * @throws InvalidParameterException
+	 *             thrown if generatedReplaySeq is null
 	 */
 	public void addReplaySequence(List<T> generatedReplaySeq) {
+		if (generatedReplaySeq == null) {
+			throw new InvalidParameterException(
+					"generatedReplaySeq must not be null");
+		}
 		replayEvents.addAll(generatedReplaySeq);
 	}
@@ -149,5 +161,7 @@
 	}
 
-	/* (non-Javadoc)
+	/*
+	 * (non-Javadoc)
+	 * 
 	 * @see de.ugoe.cs.eventbench.data.Event#equals(java.lang.Object)
 	 */
@@ -159,7 +173,13 @@
 		if (other instanceof ReplayableEvent<?>) {
 			ReplayableEvent<?> otherEvent = (ReplayableEvent<?>) other;
-			return super.equals(otherEvent)
-					&& replayEvents.equals(otherEvent.replayEvents)
-					&& replayValid == otherEvent.replayValid;
+			if (replayEvents != null) {
+				return super.equals(otherEvent)
+						&& replayEvents.equals(otherEvent.replayEvents)
+						&& replayValid == otherEvent.replayValid;
+			} else {
+				return super.equals(otherEvent)
+						&& otherEvent.replayEvents == null
+						&& replayValid == otherEvent.replayValid;
+			}
 
 		} else {
@@ -168,5 +188,12 @@
 	}
 	
-	/* (non-Javadoc)
+	@Override
+	public boolean canEqual(Object other) {
+		return (other instanceof ReplayableEvent<?>);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * 
 	 * @see de.ugoe.cs.eventbench.data.Event#hashCode()
 	 */
@@ -175,5 +202,7 @@
 		int multiplier = 17;
 		int hash = super.hashCode();
-		hash = multiplier * hash + replayEvents.hashCode();
+		if (replayEvents != null) {
+			hash = multiplier * hash + replayEvents.hashCode();
+		}
 		hash = multiplier * hash + (replayValid ? 1 : 0);