From 6e6d8605d359316c5d527952408e412e29973531 Mon Sep 17 00:00:00 2001
From: "Timothy A. Bish" <tabish@apache.org>
Date: Tue, 6 Sep 2011 19:35:33 +0000
Subject: [PATCH] https://issues.apache.org/jira/browse/AMQ-3467

Handle a potential NPE case.

git-svn-id: https://svn.apache.org/repos/asf/activemq/trunk@1165797 13f79535-47bb-0310-9956-ffa450edef68
---
 .../main/java/org/apache/kahadb/util/SequenceSet.java  |  6 ++++--
 .../java/org/apache/kahadb/util/SequenceSetTest.java   | 10 ++++++++++
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/kahadb/src/main/java/org/apache/kahadb/util/SequenceSet.java b/kahadb/src/main/java/org/apache/kahadb/util/SequenceSet.java
index 87411b1380..a3bdeae925 100644
--- a/kahadb/src/main/java/org/apache/kahadb/util/SequenceSet.java
+++ b/kahadb/src/main/java/org/apache/kahadb/util/SequenceSet.java
@@ -369,11 +369,13 @@ public class SequenceSet extends LinkedNodeList<Sequence> implements Iterable<Lo
     private class SequenceIterator implements Iterator<Long> {
 
         private Sequence currentEntry;
-        private long lastReturned;
+        private long lastReturned = -1;
 
         public SequenceIterator() {
             currentEntry = getHead();
-            lastReturned = currentEntry.first - 1;
+            if (currentEntry != null) {
+                lastReturned = currentEntry.first - 1;
+            }
         }
 
         public boolean hasNext() {
diff --git a/kahadb/src/test/java/org/apache/kahadb/util/SequenceSetTest.java b/kahadb/src/test/java/org/apache/kahadb/util/SequenceSetTest.java
index ebc8043f4c..48c9e484f5 100644
--- a/kahadb/src/test/java/org/apache/kahadb/util/SequenceSetTest.java
+++ b/kahadb/src/test/java/org/apache/kahadb/util/SequenceSetTest.java
@@ -126,4 +126,14 @@ public class SequenceSetTest {
             assertEquals(expected[index++], iterator.next().longValue());
         }
     }
+
+    @Test
+    public void testIteratorEmptySequenceSet() {
+        SequenceSet set = new SequenceSet();
+
+        Iterator<Long> iterator = set.iterator();
+        while(iterator.hasNext()) {
+            fail("Should not have any elements");
+        }
+    }
 }