From 24d38cdba4e6698dafc0c9e2e34cb017b8e51962 Mon Sep 17 00:00:00 2001
From: Mike Hearn <hearn@google.com>
Date: Wed, 11 Dec 2013 09:48:47 -0800
Subject: [PATCH] Check for and reject null event listeners.

---
 .../google/bitcoin/utils/ListenerRegistration.java   | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/core/src/main/java/com/google/bitcoin/utils/ListenerRegistration.java b/core/src/main/java/com/google/bitcoin/utils/ListenerRegistration.java
index dbe791cc..5ae792f7 100644
--- a/core/src/main/java/com/google/bitcoin/utils/ListenerRegistration.java
+++ b/core/src/main/java/com/google/bitcoin/utils/ListenerRegistration.java
@@ -19,19 +19,23 @@ package com.google.bitcoin.utils;
 import java.util.List;
 import java.util.concurrent.Executor;
 
+import static com.google.common.base.Preconditions.checkNotNull;
+
 /**
 * A simple wrapper around a listener and an executor, with some utility methods.
 */
 public class ListenerRegistration<T> {
-    public T listener;
-    public Executor executor;
+    public final T listener;
+    public final Executor executor;
 
     public ListenerRegistration(T listener, Executor executor) {
-        this.listener = listener;
-        this.executor = executor;
+        this.listener = checkNotNull(listener);
+        this.executor = checkNotNull(executor);
     }
 
     public static <T> boolean removeFromList(T listener, List<? extends ListenerRegistration<T>> list) {
+        checkNotNull(listener);
+
         ListenerRegistration<T> item = null;
         for (ListenerRegistration<T> registration : list) {
             if (registration.listener == listener) {