MAPREDUCE-6881. Fix warnings from Spotbugs in hadoop-mapreduce. Contributed by Weiwei Yang.

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapred/LocalContainerLauncher.java

@@ -27,6 +27,8 @@
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
+import java.util.Collections;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutorService;
@@ -81,7 +83,7 @@ public class LocalContainerLauncher extends AbstractService implements
   private static final Log LOG = LogFactory.getLog(LocalContainerLauncher.class);
 
   private FileContext curFC = null;
-  private final HashSet<File> localizedFiles;
+  private Set<File> localizedFiles = new HashSet<File>();
   private final AppContext context;
   private final TaskUmbilicalProtocol umbilical;
   private final ClassLoader jobClassLoader;
@@ -121,9 +123,12 @@ public LocalContainerLauncher(AppContext context,
     // users who do that get what they deserve (and will have to disable
     // uberization in order to run correctly).
     File[] curLocalFiles = curDir.listFiles();
-    localizedFiles = new HashSet<File>(curLocalFiles.length);
-    for (int j = 0; j < curLocalFiles.length; ++j) {
-      localizedFiles.add(curLocalFiles[j]);
+    if (curLocalFiles != null) {
+      HashSet<File> lf = new HashSet<File>(curLocalFiles.length);
+      for (int j = 0; j < curLocalFiles.length; ++j) {
+        lf.add(curLocalFiles[j]);
+      }
+      localizedFiles = Collections.unmodifiableSet(lf);
     }
 
     // Relocalization note/future FIXME (per chrisdo, 20110315):  At moment,
@@ -521,26 +526,29 @@ private void runSubtask(org.apache.hadoop.mapred.Task task,
      */
     private void relocalize() {
       File[] curLocalFiles = curDir.listFiles();
-      for (int j = 0; j < curLocalFiles.length; ++j) {
-        if (!localizedFiles.contains(curLocalFiles[j])) {
-          // found one that wasn't there before:  delete it
-          boolean deleted = false;
-          try {
-            if (curFC != null) {
-              // this is recursive, unlike File delete():
-              deleted = curFC.delete(new Path(curLocalFiles[j].getName()),true);
+      if (curLocalFiles != null) {
+        for (int j = 0; j < curLocalFiles.length; ++j) {
+          if (!localizedFiles.contains(curLocalFiles[j])) {
+            // found one that wasn't there before:  delete it
+            boolean deleted = false;
+            try {
+              if (curFC != null) {
+                // this is recursive, unlike File delete():
+                deleted =
+                    curFC.delete(new Path(curLocalFiles[j].getName()), true);
+              }
+            } catch (IOException e) {
+              deleted = false;
+            }
+            if (!deleted) {
+              LOG.warn("Unable to delete unexpected local file/dir "
+                  + curLocalFiles[j].getName()
+                  + ": insufficient permissions?");
             }
-          } catch (IOException e) {
-            deleted = false;
-          }
-          if (!deleted) {
-            LOG.warn("Unable to delete unexpected local file/dir "
-                + curLocalFiles[j].getName() + ": insufficient permissions?");
           }
         }
       }
     }
-
   } // end EventHandler
 
   /**

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/MRAppMaster.java

@@ -572,13 +572,15 @@ protected AMPreemptionPolicy createPreemptionPolicy(Configuration conf) {
   private boolean isJobNamePatternMatch(JobConf conf, String jobTempDir) {
     // Matched staging files should be preserved after job is finished.
     if (conf.getKeepTaskFilesPattern() != null && jobTempDir != null) {
-      String jobFileName = Paths.get(jobTempDir).getFileName().toString();
-      Pattern pattern = Pattern.compile(conf.getKeepTaskFilesPattern());
-      Matcher matcher = pattern.matcher(jobFileName);
-      return matcher.find();
-    } else {
-      return false;
+      java.nio.file.Path pathName = Paths.get(jobTempDir).getFileName();
+      if (pathName != null) {
+        String jobFileName = pathName.toString();
+        Pattern pattern = Pattern.compile(conf.getKeepTaskFilesPattern());
+        Matcher matcher = pattern.matcher(jobFileName);
+        return matcher.find();
+      }
     }
+    return false;
   }
 
   private boolean isKeepFailedTaskFiles(JobConf conf) {

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/JVMId.java

@@ -98,7 +98,7 @@ public int compareTo(JVMId that) {
     int jobComp = this.jobId.compareTo(that.jobId);
     if(jobComp == 0) {
       if(this.isMap == that.isMap) {
-        return Long.valueOf(this.jvmId).compareTo(that.jvmId);
+        return Long.compare(this.jvmId, that.jvmId);
       } else {
         return this.isMap ? -1 : 1;
       }

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/Operation.java

@@ -35,11 +35,19 @@ public enum Operation {
   SET_JOB_PRIORITY(QueueACL.ADMINISTER_JOBS, JobACL.MODIFY_JOB),
   SUBMIT_JOB(QueueACL.SUBMIT_JOB, null);
 
-  public QueueACL qACLNeeded;
-  public JobACL jobACLNeeded;
+  private final QueueACL qACLNeeded;
+  private final JobACL jobACLNeeded;
   
   Operation(QueueACL qACL, JobACL jobACL) {
     this.qACLNeeded = qACL;
     this.jobACLNeeded = jobACL;
   }
+
+  public QueueACL getqACLNeeded() {
+    return qACLNeeded;
+  }
+
+  public JobACL getJobACLNeeded() {
+    return jobACLNeeded;
+  }
 }

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-hs/src/main/java/org/apache/hadoop/mapreduce/v2/hs/HistoryFileManager.java

@@ -407,17 +407,12 @@ synchronized void moveToDone() throws IOException {
         }
         JobId jobId = jobIndexInfo.getJobId();
 
-        List<Path> paths = new ArrayList<Path>(2);
         if (historyFile == null) {
           LOG.info("No file for job-history with " + jobId + " found in cache!");
-        } else {
-          paths.add(historyFile);
         }
 
         if (confFile == null) {
           LOG.info("No file for jobConf with " + jobId + " found in cache!");
-        } else {
-          paths.add(confFile);
         }
 
         if (summaryFile == null || !intermediateDoneDirFc.util().exists(

hadoop-mapreduce-project/hadoop-mapreduce-examples/src/main/java/org/apache/hadoop/examples/pi/Parser.java

@@ -67,8 +67,12 @@ private static void parseLine(final String line, Map<Parameter, List<TaskResult>
   private void parse(File f, Map<Parameter, List<TaskResult>> sums) throws IOException {
     if (f.isDirectory()) {
       println("Process directory " + f);
-      for(File child : f.listFiles())
-        parse(child, sums);
+      File[] files = f.listFiles();
+      if (files != null) {
+        for(File child : files) {
+          parse(child, sums);
+        }
+      }
     } else if (f.getName().endsWith(".txt")) {
       println("Parse file " + f);
       final Map<Parameter, List<TaskResult>> m = new TreeMap<Parameter, List<TaskResult>>();