Simplify EventHistoryManager
Change-Id: Ifefc68269e469883960359406d603e8c24b399df
diff --git a/core/api/src/main/java/org/onosproject/event/ListenerTracker.java b/core/api/src/main/java/org/onosproject/event/ListenerTracker.java
index 395d869..eafd249 100644
--- a/core/api/src/main/java/org/onosproject/event/ListenerTracker.java
+++ b/core/api/src/main/java/org/onosproject/event/ListenerTracker.java
@@ -15,13 +15,14 @@
*/
package org.onosproject.event;
+import static com.google.common.base.Preconditions.checkNotNull;
+
import java.util.ArrayList;
import java.util.List;
import javax.annotation.concurrent.NotThreadSafe;
import org.apache.commons.lang3.tuple.Pair;
-
import com.google.common.annotations.Beta;
import com.google.common.collect.Lists;
@@ -66,6 +67,9 @@
*/
public <E extends Event<?, ?>, L extends EventListener<E>>
ListenerTracker addListener(ListenerService<E, L> service, L listener) {
+
+ checkNotNull(service);
+ checkNotNull(listener);
service.addListener(listener);
listeners.add(Pair.of(service, listener));
return this;