HADOOP-2036. Fix a NullPointerException in JvmMetrics class. Contributed by Nigel.

git-svn-id: https://svn.apache.org/repos/asf/lucene/hadoop/trunk@584044 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -284,6 +284,8 @@ Trunk (unreleased changes)
     HADOOP-2023. Disable TestLocalDirAllocator on Windows.
     (Hairong Kuang via nigel)
 
+    HADOOP-2036. Fix a NullPointerException in JvmMetrics class. (nigel)
+
   IMPROVEMENTS
 
     HADOOP-1908. Restructure data node code so that block sending and 

src/java/org/apache/hadoop/metrics/jvm/JvmMetrics.java

@@ -126,6 +126,8 @@ public class JvmMetrics implements Updater {
         int threadsTerminated = 0;
         
         for (ThreadInfo threadInfo : threadInfos) {
+            // threadInfo is null if the thread is not alive or doesn't exist
+            if (threadInfo == null) continue;
             Thread.State state = threadInfo.getThreadState();
             if (state == NEW) {
                 threadsNew++;