HDFS-9596. Remove Shuffle Method From DFSUtil. Contributed by BELUGA BEHR.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSUtil.java

@@ -56,7 +56,6 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import java.util.concurrent.ThreadLocalRandom;
 
 import org.apache.commons.cli.CommandLine;
 import org.apache.commons.cli.CommandLineParser;
@@ -116,22 +115,6 @@ public class DFSUtil {
     return SECURE_RANDOM.get();
   }
 
-  /** Shuffle the elements in the given array. */
-  public static <T> T[] shuffle(final T[] array) {
-    if (array != null && array.length > 0) {
-      for (int n = array.length; n > 1; ) {
-        final int randomIndex = ThreadLocalRandom.current().nextInt(n);
-        n--;
-        if (n != randomIndex) {
-          final T tmp = array[randomIndex];
-          array[randomIndex] = array[n];
-          array[n] = tmp;
-        }
-      }
-    }
-    return array;
-  }
-
   /**
    * Comparator for sorting DataNodeInfo[] based on
    * decommissioned and entering_maintenance states.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/balancer/Dispatcher.java

@@ -29,7 +29,9 @@ import java.io.InputStream;
 import java.io.OutputStream;
 import java.net.Socket;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.EnumMap;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -50,7 +52,6 @@ import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.StorageType;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
-import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.DFSUtilClient;
 import org.apache.hadoop.hdfs.DistributedFileSystem;
 import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys;
@@ -1120,7 +1121,8 @@ public class Dispatcher {
     final List<DatanodeStorageReport> trimmed = new ArrayList<DatanodeStorageReport>(); 
     // create network topology and classify utilization collections:
     // over-utilized, above-average, below-average and under-utilized.
-    for (DatanodeStorageReport r : DFSUtil.shuffle(reports)) {
+    Collections.shuffle(Arrays.asList(reports));
+    for (DatanodeStorageReport r : reports) {
       final DatanodeInfo datanode = r.getDatanodeInfo();
       if (shouldIgnore(datanode)) {
         continue;

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestBlockPlacementPolicyRackFaultTolerant.java

@@ -22,7 +22,6 @@ import org.apache.hadoop.fs.CreateFlag;
 import org.apache.hadoop.fs.permission.FsPermission;
 import org.apache.hadoop.fs.permission.PermissionStatus;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
-import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
@@ -174,7 +173,7 @@ public class TestBlockPlacementPolicyRackFaultTolerant {
     for (int i = 0; i < length; i++) {
       pairs[i] = new Object[]{locs[i], storageIDs[i]};
     }
-    DFSUtil.shuffle(pairs);
+    Collections.shuffle(Arrays.asList(pairs));
     for (int i = 0; i < length; i++) {
       locs[i] = (DatanodeInfo) pairs[i][0];
       storageIDs[i] = (String) pairs[i][1];