diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
index 844b67ce1a877..8e547a475ada4 100755
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
@@ -1073,12 +1073,7 @@ public void start() {
           formatThreadName("lifeline", lifelineNnAddr));
       lifelineThread.setDaemon(true);
       lifelineThread.setUncaughtExceptionHandler(
-          new Thread.UncaughtExceptionHandler() {
-            @Override
-            public void uncaughtException(Thread thread, Throwable t) {
-              LOG.error(thread + " terminating on unexpected exception", t);
-            }
-          });
+          (thread, t) -> LOG.error("{} terminating on unexpected exception", thread, t));
       lifelineThread.start();
     }
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolManager.java
index 073576546c790..be4fa0fed54e8 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolManager.java
@@ -123,14 +123,11 @@ void shutDownAll(List<BPOfferService> bposList) throws InterruptedException {
   synchronized void startAll() throws IOException {
     try {
       UserGroupInformation.getLoginUser().doAs(
-          new PrivilegedExceptionAction<Object>() {
-            @Override
-            public Object run() throws Exception {
-              for (BPOfferService bpos : offerServices) {
-                bpos.start();
-              }
-              return null;
+          (PrivilegedExceptionAction<Object>) () -> {
+            for (BPOfferService bpos : offerServices) {
+              bpos.start();
             }
+            return null;
           });
     } catch (InterruptedException ex) {
       IOException ioe = new IOException();
@@ -274,13 +271,10 @@ private void doRefreshNamenodes(
           nnIds.add(nnId);
         }
         try {
-          UserGroupInformation.getLoginUser()
-              .doAs(new PrivilegedExceptionAction<Object>() {
-                @Override
-                public Object run() throws Exception {
-                  bpos.refreshNNList(nsToRefresh, nnIds, addrs, lifelineAddrs);
-                  return null;
-                }
+          UserGroupInformation.getLoginUser().doAs(
+              (PrivilegedExceptionAction<Object>) () -> {
+                bpos.refreshNNList(nsToRefresh, nnIds, addrs, lifelineAddrs);
+                return null;
               });
         } catch (InterruptedException ex) {
           IOException ioe = new IOException();
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolSliceStorage.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolSliceStorage.java
index a82ed0045a6a3..f019f64f383fd 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolSliceStorage.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolSliceStorage.java
@@ -489,13 +489,9 @@ private void doUpgrade(final StorageDirectory bpSd,
     if (callables == null) {
       doUpgrade(name, bpSd, nsInfo, bpPrevDir, bpTmpDir, bpCurDir, oldLV, conf);
     } else {
-      callables.add(new Callable<StorageDirectory>() {
-        @Override
-        public StorageDirectory call() throws Exception {
-          doUpgrade(name, bpSd, nsInfo, bpPrevDir, bpTmpDir, bpCurDir, oldLV,
-              conf);
-          return bpSd;
-        }
+      callables.add(() -> {
+        doUpgrade(name, bpSd, nsInfo, bpPrevDir, bpTmpDir, bpCurDir, oldLV, conf);
+        return bpSd;
       });
     }
   }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockRecoveryWorker.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockRecoveryWorker.java
index e4861f9774870..5ad85df9a4292 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockRecoveryWorker.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockRecoveryWorker.java
@@ -598,26 +598,23 @@ DatanodeProtocolClientSideTranslatorPB getActiveNamenodeForBP(
 
   public Daemon recoverBlocks(final String who,
       final Collection<RecoveringBlock> blocks) {
-    Daemon d = new Daemon(datanode.threadGroup, new Runnable() {
-      @Override
-      public void run() {
-        datanode.metrics.incrDataNodeBlockRecoveryWorkerCount();
-        try {
-          for (RecoveringBlock b : blocks) {
-            try {
-              logRecoverBlock(who, b);
-              if (b.isStriped()) {
-                new RecoveryTaskStriped((RecoveringStripedBlock) b).recover();
-              } else {
-                new RecoveryTaskContiguous(b).recover();
-              }
-            } catch (IOException e) {
-              LOG.warn("recover Block: {} FAILED: {}", b, e);
+    Daemon d = new Daemon(datanode.threadGroup, () -> {
+      datanode.metrics.incrDataNodeBlockRecoveryWorkerCount();
+      try {
+        for (RecoveringBlock b : blocks) {
+          try {
+            logRecoverBlock(who, b);
+            if (b.isStriped()) {
+              new RecoveryTaskStriped((RecoveringStripedBlock) b).recover();
+            } else {
+              new RecoveryTaskContiguous(b).recover();
             }
+          } catch (IOException e) {
+            LOG.warn("recover Block: {} FAILED: {}", b, e);
           }
-        } finally {
-          datanode.metrics.decrDataNodeBlockRecoveryWorkerCount();
         }
+      } finally {
+        datanode.metrics.decrDataNodeBlockRecoveryWorkerCount();
       }
     });
     d.start();
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
index d64502b6ddc86..6453d43c9966c 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
@@ -124,7 +124,6 @@
 import java.util.Map.Entry;
 import java.util.Set;
 import java.util.UUID;
-import java.util.concurrent.Callable;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorService;
@@ -202,7 +201,6 @@
 import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier;
 import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier.AccessMode;
 import org.apache.hadoop.hdfs.security.token.block.BlockTokenSecretManager;
-import org.apache.hadoop.hdfs.security.token.block.DataEncryptionKey;
 import org.apache.hadoop.hdfs.security.token.block.ExportedBlockKeys;
 import org.apache.hadoop.hdfs.security.token.block.InvalidBlockTokenException;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.NodeType;
@@ -1176,16 +1174,13 @@ private void refreshVolumes(String newVolumes) throws IOException {
 
           Preconditions.checkNotNull(data, "Storage not yet initialized");
           for (final StorageLocation location : changedVolumes.newLocations) {
-            exceptions.add(service.submit(new Callable<IOException>() {
-              @Override
-              public IOException call() {
-                try {
-                  data.addVolume(location, nsInfos);
-                } catch (IOException e) {
-                  return e;
-                }
-                return null;
+            exceptions.add(service.submit(() -> {
+              try {
+                data.addVolume(location, nsInfos);
+              } catch (IOException e) {
+                return e;
               }
+              return null;
             }));
           }
 
@@ -2242,14 +2237,10 @@ public static InterDatanodeProtocol createInterDataNodeProtocolProxy(
         dnAddr, addr);
     final UserGroupInformation loginUgi = UserGroupInformation.getLoginUser();
     try {
-      return loginUgi
-          .doAs(new PrivilegedExceptionAction<InterDatanodeProtocol>() {
-            @Override
-            public InterDatanodeProtocol run() throws IOException {
-              return new InterDatanodeProtocolTranslatorPB(addr, loginUgi,
-                  conf, NetUtils.getDefaultSocketFactory(conf), socketTimeout);
-            }
-          });
+      return loginUgi.doAs(
+          (PrivilegedExceptionAction<InterDatanodeProtocol>) () ->
+              new InterDatanodeProtocolTranslatorPB(addr, loginUgi, conf,
+                  NetUtils.getDefaultSocketFactory(conf), socketTimeout));
     } catch (InterruptedException ie) {
       throw new IOException(ie.getMessage());
     }
@@ -3029,14 +3020,8 @@ public Token<BlockTokenIdentifier> getBlockAccessToken(ExtendedBlock b,
    */
   public DataEncryptionKeyFactory getDataEncryptionKeyFactoryForBlock(
       final ExtendedBlock block) {
-    return new DataEncryptionKeyFactory() {
-      @Override
-      public DataEncryptionKey newDataEncryptionKey() {
-        return dnConf.encryptDataTransfer ?
-          blockPoolTokenSecretManager.generateDataEncryptionKey(
-            block.getBlockPoolId()) : null;
-      }
-    };
+    return () -> dnConf.encryptDataTransfer ?
+      blockPoolTokenSecretManager.generateDataEncryptionKey(block.getBlockPoolId()) : null;
   }
 
   /**
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataStorage.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataStorage.java
index 782f2f36cc198..a1fe9e1230161 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataStorage.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataStorage.java
@@ -839,12 +839,9 @@ void doUpgradePreFederation(final StorageDirectory sd,
     if (callables == null) {
       doUpgrade(sd, nsInfo, prevDir, tmpDir, bbwDir, toDir, oldLV, conf);
     } else {
-      callables.add(new Callable<StorageDirectory>() {
-        @Override
-        public StorageDirectory call() throws Exception {
-          doUpgrade(sd, nsInfo, prevDir, tmpDir, bbwDir, toDir, oldLV, conf);
-          return sd;
-        }
+      callables.add(() -> {
+        doUpgrade(sd, nsInfo, prevDir, tmpDir, bbwDir, toDir, oldLV, conf);
+        return sd;
       });
     }
   }
@@ -1138,17 +1135,13 @@ private static void linkBlocks(File from, File to, int oldLV,
     List<Future<Void>> futures = Lists.newArrayList();
     for (int i = 0; i < idBasedLayoutSingleLinks.size(); i += step) {
       final int iCopy = i;
-      futures.add(linkWorkers.submit(new Callable<Void>() {
-        @Override
-        public Void call() throws IOException {
-          int upperBound = Math.min(iCopy + step,
-              idBasedLayoutSingleLinks.size());
-          for (int j = iCopy; j < upperBound; j++) {
-            LinkArgs cur = idBasedLayoutSingleLinks.get(j);
-            HardLink.createHardLink(cur.src(), cur.dst());
-          }
-          return null;
+      futures.add(linkWorkers.submit(() -> {
+        int upperBound = Math.min(iCopy + step, idBasedLayoutSingleLinks.size());
+        for (int j = iCopy; j < upperBound; j++) {
+          LinkArgs cur = idBasedLayoutSingleLinks.get(j);
+          HardLink.createHardLink(cur.src(), cur.dst());
         }
+        return null;
       }));
     }
     linkWorkers.shutdown();
@@ -1334,12 +1327,7 @@ static void linkBlocksHelper(File from, File to, HardLink hl,
     // from is a directory
     hl.linkStats.countDirs++;
     
-    String[] blockNames = from.list(new java.io.FilenameFilter() {
-      @Override
-      public boolean accept(File dir, String name) {
-        return name.startsWith(Block.BLOCK_FILE_PREFIX);
-      }
-    });
+    String[] blockNames = from.list((dir, name) -> name.startsWith(Block.BLOCK_FILE_PREFIX));
 
     // If we are upgrading to block ID-based layout, we don't want to recreate
     // any subdirs from the source that contain blocks, since we have a new
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataXceiverServer.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataXceiverServer.java
index 3a67b76e43467..c90797800e6ed 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataXceiverServer.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataXceiverServer.java
@@ -382,7 +382,7 @@ void restartNotifyPeers() {
     lock.lock();
     try {
       // interrupt each and every DataXceiver thread.
-      peers.values().forEach(t -> t.interrupt());
+      peers.values().forEach(Thread::interrupt);
     } finally {
       lock.unlock();
     }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DiskBalancer.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DiskBalancer.java
index 4126140678759..bc00962d5e8f9 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DiskBalancer.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DiskBalancer.java
@@ -527,17 +527,12 @@ private void executePlan() {
       this.scheduler = Executors.newSingleThreadExecutor();
     }
 
-    this.future = scheduler.submit(new Runnable() {
-      @Override
-      public void run() {
-        Thread.currentThread().setName("DiskBalancerThread");
-        LOG.info("Executing Disk balancer plan. Plan File: {}, Plan ID: {}",
-            planFile, planID);
-        for (Map.Entry<VolumePair, DiskBalancerWorkItem> entry :
-            workMap.entrySet()) {
-          blockMover.setRunnable();
-          blockMover.copyBlocks(entry.getKey(), entry.getValue());
-        }
+    this.future = scheduler.submit(() -> {
+      Thread.currentThread().setName("DiskBalancerThread");
+      LOG.info("Executing Disk balancer plan. Plan File: {}, Plan ID: {}", planFile, planID);
+      for (Map.Entry<VolumePair, DiskBalancerWorkItem> entry : workMap.entrySet()) {
+        blockMover.setRunnable();
+        blockMover.copyBlocks(entry.getKey(), entry.getValue());
       }
     });
   }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/checker/DatasetVolumeChecker.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/checker/DatasetVolumeChecker.java
index da6ae95918d9f..79e0eef15a793 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/checker/DatasetVolumeChecker.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/checker/DatasetVolumeChecker.java
@@ -225,13 +225,8 @@ public Set<FsVolumeSpi> checkAllVolumes(
         allVolumes.add(reference.getVolume());
         Futures.addCallback(olf.get(),
             new ResultHandler(reference, healthyVolumes, failedVolumes,
-                numVolumes, new Callback() {
-                  @Override
-                  public void call(Set<FsVolumeSpi> ignored1,
-                                   Set<FsVolumeSpi> ignored2) {
-                    latch.countDown();
-                  }
-                }), MoreExecutors.directExecutor());
+                numVolumes, (ignored1, ignored2) -> latch.countDown()),
+            MoreExecutors.directExecutor());
       } else {
         IOUtils.cleanupWithLogger(null, reference);
         if (numVolumes.decrementAndGet() == 0) {
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/checker/ThrottledAsyncChecker.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/checker/ThrottledAsyncChecker.java
index f969c7ade288b..74d548cf7b3bb 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/checker/ThrottledAsyncChecker.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/checker/ThrottledAsyncChecker.java
@@ -36,7 +36,6 @@
 import java.util.Map;
 import java.util.Optional;
 import java.util.WeakHashMap;
-import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledThreadPoolExecutor;
@@ -135,13 +134,8 @@ public synchronized Optional<ListenableFuture<V>> schedule(
     }
 
     LOG.info("Scheduling a check for {}", target);
-    final ListenableFuture<V> lfWithoutTimeout = executorService.submit(
-        new Callable<V>() {
-          @Override
-          public V call() throws Exception {
-            return target.check(context);
-          }
-        });
+    final ListenableFuture<V> lfWithoutTimeout =
+        executorService.submit(() -> target.check(context));
     final ListenableFuture<V> lf;
 
     if (diskCheckTimeout > 0) {
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/erasurecode/StripedBlockReader.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/erasurecode/StripedBlockReader.java
index 54302e3c2561d..545790c7629ba 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/erasurecode/StripedBlockReader.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/erasurecode/StripedBlockReader.java
@@ -166,24 +166,19 @@ private Peer newConnectedPeer(ExtendedBlock b, InetSocketAddress addr,
 
   Callable<BlockReadStats> readFromBlock(final int length,
                                final CorruptedBlocks corruptedBlocks) {
-    return new Callable<BlockReadStats>() {
-
-      @Override
-      public BlockReadStats call() throws Exception {
-        try {
-          getReadBuffer().limit(length);
-          return actualReadFromBlock();
-        } catch (ChecksumException e) {
-          LOG.warn("Found Checksum error for {} from {} at {}", block,
-              source, e.getPos());
-          corruptedBlocks.addCorruptedBlock(block, source);
-          throw e;
-        } catch (IOException e) {
-          LOG.info(e.getMessage());
-          throw e;
-        } finally {
-          DataNodeFaultInjector.get().interceptBlockReader();
-        }
+    return () -> {
+      try {
+        getReadBuffer().limit(length);
+        return actualReadFromBlock();
+      } catch (ChecksumException e) {
+        LOG.warn("Found Checksum error for {} from {} at {}", block, source, e.getPos());
+        corruptedBlocks.addCorruptedBlock(block, source);
+        throw e;
+      } catch (IOException e) {
+        LOG.info(e.getMessage());
+        throw e;
+      } finally {
+        DataNodeFaultInjector.get().interceptBlockReader();
       }
     };
   }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/BlockPoolSlice.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/BlockPoolSlice.java
index 23f3602a456c8..425678c7ef2d8 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/BlockPoolSlice.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/BlockPoolSlice.java
@@ -126,13 +126,7 @@ public class BlockPoolSlice {
   private static ForkJoinPool addReplicaThreadPool = null;
   private static final int VOLUMES_REPLICA_ADD_THREADPOOL_SIZE = Runtime
       .getRuntime().availableProcessors();
-  private static final Comparator<File> FILE_COMPARATOR =
-      new Comparator<File>() {
-    @Override
-    public int compare(File f1, File f2) {
-      return f1.getName().compareTo(f2.getName());
-    }
-  };
+  private static final Comparator<File> FILE_COMPARATOR = Comparator.comparing(File::getName);
 
   // TODO:FEDERATION scalability issue - a thread per DU is needed
   private volatile GetSpaceUsed dfsUsage;
@@ -228,13 +222,10 @@ public int compare(File f1, File f2) {
       initializeAddReplicaPool(conf, (FsDatasetImpl) volume.getDataset());
     }
     // Make the dfs usage to be saved during shutdown.
-    shutdownHook = new Runnable() {
-      @Override
-      public void run() {
-        if (!dfsUsedSaved) {
-          saveDfsUsed();
-          addReplicaThreadPool.shutdownNow();
-        }
+    shutdownHook = () -> {
+      if (!dfsUsedSaved) {
+        saveDfsUsed();
+        addReplicaThreadPool.shutdownNow();
       }
     };
     ShutdownHookManager.get().addShutdownHook(shutdownHook,
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetUtil.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetUtil.java
index b7686c512963a..bb11ccde4f997 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetUtil.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetUtil.java
@@ -22,7 +22,6 @@
 import java.io.File;
 import java.io.FileDescriptor;
 import java.io.FileNotFoundException;
-import java.io.FilenameFilter;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.RandomAccessFile;
@@ -90,13 +89,9 @@ static File getMetaFile(File f, long gs) {
   public static File findMetaFile(final File blockFile) throws IOException {
     final String prefix = blockFile.getName() + "_";
     final File parent = blockFile.getParentFile();
-    final File[] matches = parent.listFiles(new FilenameFilter() {
-      @Override
-      public boolean accept(File dir, String name) {
-        return dir.equals(parent) && name.startsWith(prefix)
-            && name.endsWith(Block.METADATA_EXTENSION);
-      }
-    });
+    final File[] matches = parent.listFiles(
+        (dir, name) -> dir.equals(parent) && name.startsWith(prefix)
+            && name.endsWith(Block.METADATA_EXTENSION));
 
     if (matches == null || matches.length == 0) {
       throw new FileNotFoundException(
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeList.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeList.java
index 262a24bd3aa45..711c0671cfc7f 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeList.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeList.java
@@ -260,23 +260,22 @@ void getAllVolumesMap(final String bpid,
         new ConcurrentHashMap<FsVolumeSpi, IOException>();
     List<Thread> replicaAddingThreads = new ArrayList<Thread>();
     for (final FsVolumeImpl v : volumes) {
-      Thread t = new Thread() {
-        public void run() {
-          try (FsVolumeReference ref = v.obtainReference()) {
-            FsDatasetImpl.LOG.info("Adding replicas to map for block pool " +
-                bpid + " on volume " + v + "...");
-            long startTime = Time.monotonicNow();
-            v.getVolumeMap(bpid, volumeMap, ramDiskReplicaMap);
-            long timeTaken = Time.monotonicNow() - startTime;
-            FsDatasetImpl.LOG.info("Time to add replicas to map for block pool"
-                + " " + bpid + " on volume " + v + ": " + timeTaken + "ms");
-          } catch (IOException ioe) {
-            FsDatasetImpl.LOG.info("Caught exception while adding replicas " +
-                "from " + v + ". Will throw later.", ioe);
-            unhealthyDataDirs.put(v, ioe);
-          }
+      Thread t = new Thread(() -> {
+        try (FsVolumeReference ref = v.obtainReference()) {
+          FsDatasetImpl.LOG.info("Adding replicas to map for block pool {} on volume {}...",
+              bpid, v);
+          long startTime = Time.monotonicNow();
+          v.getVolumeMap(bpid, volumeMap, ramDiskReplicaMap);
+          long timeTaken = Time.monotonicNow() - startTime;
+          FsDatasetImpl.LOG.info(
+              "Time to add replicas to map for block pool {} on volume {}: {}ms.",
+              bpid, v, timeTaken);
+        } catch (IOException ioe) {
+          FsDatasetImpl.LOG.info(
+              "Caught exception while adding replicas from {}. Will throw later.", v, ioe);
+          unhealthyDataDirs.put(v, ioe);
         }
-      };
+      });
       replicaAddingThreads.add(t);
       t.start();
     }
@@ -507,23 +506,19 @@ void addBlockPool(final String bpid, final Configuration conf) throws IOExceptio
         new ConcurrentHashMap<FsVolumeSpi, IOException>();
     List<Thread> blockPoolAddingThreads = new ArrayList<Thread>();
     for (final FsVolumeImpl v : volumes) {
-      Thread t = new Thread() {
-        public void run() {
-          try (FsVolumeReference ref = v.obtainReference()) {
-            FsDatasetImpl.LOG.info("Scanning block pool " + bpid +
-                " on volume " + v + "...");
-            long startTime = Time.monotonicNow();
-            v.addBlockPool(bpid, conf);
-            long timeTaken = Time.monotonicNow() - startTime;
-            FsDatasetImpl.LOG.info("Time taken to scan block pool " + bpid +
-                " on " + v + ": " + timeTaken + "ms");
-          } catch (IOException ioe) {
-            FsDatasetImpl.LOG.info("Caught exception while scanning " + v +
-                ". Will throw later.", ioe);
-            unhealthyDataDirs.put(v, ioe);
-          }
+      Thread t = new Thread(() -> {
+        try (FsVolumeReference ref = v.obtainReference()) {
+          FsDatasetImpl.LOG.info("Scanning block pool {} on volume {}...", bpid, v);
+          long startTime = Time.monotonicNow();
+          v.addBlockPool(bpid, conf);
+          long timeTaken = Time.monotonicNow() - startTime;
+          FsDatasetImpl.LOG.info("Time taken to scan block pool {} on {}: {}ms",
+              bpid, v, timeTaken);
+        } catch (IOException ioe) {
+          FsDatasetImpl.LOG.info("Caught exception while scanning {}. Will throw later.", v, ioe);
+          unhealthyDataDirs.put(v, ioe);
         }
-      };
+      });
       blockPoolAddingThreads.add(t);
       t.start();
     }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/RamDiskAsyncLazyPersistService.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/RamDiskAsyncLazyPersistService.java
index 0d42ae99e358e..a78905f126e92 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/RamDiskAsyncLazyPersistService.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/RamDiskAsyncLazyPersistService.java
@@ -78,15 +78,10 @@ class RamDiskAsyncLazyPersistService {
   }
 
   private void addExecutorForVolume(final String storageId) {
-    ThreadFactory threadFactory = new ThreadFactory() {
-
-      @Override
-      public Thread newThread(Runnable r) {
-        Thread t = new Thread(threadGroup, r);
-        t.setName("Async RamDisk lazy persist worker " +
-            " for volume with id " + storageId);
-        return t;
-      }
+    ThreadFactory threadFactory = r -> {
+      Thread t = new Thread(threadGroup, r);
+      t.setName("Async RamDisk lazy persist worker for volume with id " + storageId);
+      return t;
     };
 
     ThreadPoolExecutor executor = new ThreadPoolExecutor(
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/metrics/DataNodeDiskMetrics.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/metrics/DataNodeDiskMetrics.java
index 409084cfe8be8..fcd45e4d05239 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/metrics/DataNodeDiskMetrics.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/metrics/DataNodeDiskMetrics.java
@@ -36,9 +36,7 @@
 
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
-import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
@@ -106,69 +104,57 @@ public DataNodeDiskMetrics(DataNode dn, long diskOutlierDetectionIntervalMs,
   }
 
   private void startDiskOutlierDetectionThread() {
-    slowDiskDetectionDaemon = new Daemon(new Runnable() {
-      @Override
-      public void run() {
-        while (shouldRun) {
-          if (dn.getFSDataset() != null) {
-            Map<String, Double> metadataOpStats = Maps.newHashMap();
-            Map<String, Double> readIoStats = Maps.newHashMap();
-            Map<String, Double> writeIoStats = Maps.newHashMap();
-            FsDatasetSpi.FsVolumeReferences fsVolumeReferences = null;
-            try {
-              fsVolumeReferences = dn.getFSDataset().getFsVolumeReferences();
-              Iterator<FsVolumeSpi> volumeIterator = fsVolumeReferences
-                  .iterator();
-              while (volumeIterator.hasNext()) {
-                FsVolumeSpi volume = volumeIterator.next();
-                DataNodeVolumeMetrics metrics = volume.getMetrics();
-                String volumeName = volume.getBaseURI().getPath();
-
-                metadataOpStats.put(volumeName,
-                    metrics.getMetadataOperationMean());
-                readIoStats.put(volumeName, metrics.getReadIoMean());
-                writeIoStats.put(volumeName, metrics.getWriteIoMean());
-              }
-            } finally {
-              if (fsVolumeReferences != null) {
-                try {
-                  fsVolumeReferences.close();
-                } catch (IOException e) {
-                  LOG.error("Error in releasing FS Volume references", e);
-                }
-              }
+    slowDiskDetectionDaemon = new Daemon(() -> {
+      while (shouldRun) {
+        if (dn.getFSDataset() != null) {
+          Map<String, Double> metadataOpStats = Maps.newHashMap();
+          Map<String, Double> readIoStats = Maps.newHashMap();
+          Map<String, Double> writeIoStats = Maps.newHashMap();
+          FsDatasetSpi.FsVolumeReferences fsVolumeReferences = null;
+          try {
+            fsVolumeReferences = dn.getFSDataset().getFsVolumeReferences();
+            for (FsVolumeSpi volume : fsVolumeReferences) {
+              DataNodeVolumeMetrics metrics = volume.getMetrics();
+              String volumeName = volume.getBaseURI().getPath();
+              metadataOpStats.put(volumeName, metrics.getMetadataOperationMean());
+              readIoStats.put(volumeName, metrics.getReadIoMean());
+              writeIoStats.put(volumeName, metrics.getWriteIoMean());
             }
-            if (metadataOpStats.isEmpty() && readIoStats.isEmpty()
-                && writeIoStats.isEmpty()) {
-              LOG.debug("No disk stats available for detecting outliers.");
-              continue;
+          } finally {
+            if (fsVolumeReferences != null) {
+              try {
+                fsVolumeReferences.close();
+              } catch (IOException e) {
+                LOG.error("Error in releasing FS Volume references", e);
+              }
             }
+          }
+          if (metadataOpStats.isEmpty() && readIoStats.isEmpty() && writeIoStats.isEmpty()) {
+            LOG.debug("No disk stats available for detecting outliers.");
+            continue;
+          }
 
-            detectAndUpdateDiskOutliers(metadataOpStats, readIoStats,
-                writeIoStats);
+          detectAndUpdateDiskOutliers(metadataOpStats, readIoStats, writeIoStats);
 
-            // Sort the slow disks by latency and extract the top n by maxSlowDisksToExclude.
-            if (maxSlowDisksToExclude > 0) {
-              ArrayList<DiskLatency> diskLatencies = new ArrayList<>();
-              for (Map.Entry<String, Map<DiskOp, Double>> diskStats :
-                  diskOutliersStats.entrySet()) {
-                diskLatencies.add(new DiskLatency(diskStats.getKey(), diskStats.getValue()));
-              }
+          // Sort the slow disks by latency and extract the top n by maxSlowDisksToExclude.
+          if (maxSlowDisksToExclude > 0) {
+            ArrayList<DiskLatency> diskLatencies = new ArrayList<>();
+            for (Map.Entry<String, Map<DiskOp, Double>> diskStats : diskOutliersStats.entrySet()) {
+              diskLatencies.add(new DiskLatency(diskStats.getKey(), diskStats.getValue()));
+            }
 
-              Collections.sort(diskLatencies, (o1, o2)
-                  -> Double.compare(o2.getMaxLatency(), o1.getMaxLatency()));
+            diskLatencies.sort((o1, o2) -> Double.compare(o2.getMaxLatency(), o1.getMaxLatency()));
 
-              slowDisksToExclude = diskLatencies.stream().limit(maxSlowDisksToExclude)
-                  .map(DiskLatency::getSlowDisk).collect(Collectors.toList());
-            }
+            slowDisksToExclude = diskLatencies.stream().limit(maxSlowDisksToExclude)
+                .map(DiskLatency::getSlowDisk).collect(Collectors.toList());
           }
+        }
 
-          try {
-            Thread.sleep(detectionInterval);
-          } catch (InterruptedException e) {
-            LOG.error("Disk Outlier Detection thread interrupted", e);
-            Thread.currentThread().interrupt();
-          }
+        try {
+          Thread.sleep(detectionInterval);
+        } catch (InterruptedException e) {
+          LOG.error("Disk Outlier Detection thread interrupted", e);
+          Thread.currentThread().interrupt();
         }
       }
     });
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/DatanodeHttpServer.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/DatanodeHttpServer.java
index bb2757287fbe0..dc06ea6dfea79 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/DatanodeHttpServer.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/DatanodeHttpServer.java
@@ -180,19 +180,15 @@ protected void initChannel(SocketChannel ch) throws Exception {
       if (externalHttpChannel == null) {
         httpServer.channel(NioServerSocketChannel.class);
       } else {
-        httpServer.channelFactory(new ChannelFactory<NioServerSocketChannel>() {
-          @Override
-          public NioServerSocketChannel newChannel() {
-            return new NioServerSocketChannel(externalHttpChannel) {
+        httpServer.channelFactory((ChannelFactory<NioServerSocketChannel>) ()
+            -> new NioServerSocketChannel(externalHttpChannel) {
               // The channel has been bounded externally via JSVC,
               // thus bind() becomes a no-op.
               @Override
-              protected void doBind(SocketAddress localAddress)
-                  throws Exception {
+              protected void doBind(SocketAddress localAddress) {
+
               }
-            };
-          }
-        });
+            });
       }
     } else {
       this.httpServer = null;
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/SimpleHttpProxyHandler.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/SimpleHttpProxyHandler.java
index ef8d90a4c4e6c..8c873d91865a8 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/SimpleHttpProxyHandler.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/SimpleHttpProxyHandler.java
@@ -75,17 +75,15 @@ public void channelInactive(ChannelHandlerContext ctx) {
 
     @Override
     public void channelRead(final ChannelHandlerContext ctx, Object msg) {
-      client.writeAndFlush(msg).addListener(new ChannelFutureListener() {
-        @Override
-        public void operationComplete(ChannelFuture future) {
-          if (future.isSuccess()) {
-            ctx.channel().read();
-          } else {
-            LOG.debug("Proxy failed. Cause: ", future.cause());
-            future.channel().close();
-          }
-        }
-      });
+      client.writeAndFlush(msg).addListener(
+          (ChannelFutureListener) future -> {
+            if (future.isSuccess()) {
+              ctx.channel().read();
+            } else {
+              LOG.debug("Proxy failed. Cause: ", future.cause());
+              future.channel().close();
+            }
+          });
     }
 
     @Override
@@ -112,23 +110,19 @@ protected void initChannel(SocketChannel ch) throws Exception {
       });
     ChannelFuture f = proxiedServer.connect(host);
     proxiedChannel = f.channel();
-    f.addListener(new ChannelFutureListener() {
-      @Override
-      public void operationComplete(ChannelFuture future) throws Exception {
-        if (future.isSuccess()) {
-          ctx.channel().pipeline().remove(HttpResponseEncoder.class);
-          HttpRequest newReq = new DefaultFullHttpRequest(HTTP_1_1, req.method(), req.uri());
-          newReq.headers().add(req.headers());
-          newReq.headers().set(CONNECTION, HttpHeaderValues.CLOSE);
-          future.channel().writeAndFlush(newReq);
-        } else {
-          DefaultHttpResponse resp = new DefaultHttpResponse(HTTP_1_1,
-            INTERNAL_SERVER_ERROR);
-          resp.headers().set(CONNECTION, HttpHeaderValues.CLOSE);
-          LOG.info("Proxy " + uri + " failed. Cause: ", future.cause());
-          ctx.writeAndFlush(resp).addListener(ChannelFutureListener.CLOSE);
-          client.close();
-        }
+    f.addListener((ChannelFutureListener) future -> {
+      if (future.isSuccess()) {
+        ctx.channel().pipeline().remove(HttpResponseEncoder.class);
+        HttpRequest newReq = new DefaultFullHttpRequest(HTTP_1_1, req.method(), req.uri());
+        newReq.headers().add(req.headers());
+        newReq.headers().set(CONNECTION, HttpHeaderValues.CLOSE);
+        future.channel().writeAndFlush(newReq);
+      } else {
+        DefaultHttpResponse resp = new DefaultHttpResponse(HTTP_1_1, INTERNAL_SERVER_ERROR);
+        resp.headers().set(CONNECTION, HttpHeaderValues.CLOSE);
+        LOG.info("Proxy {} failed. Cause: ", uri, future.cause());
+        ctx.writeAndFlush(resp).addListener(ChannelFutureListener.CLOSE);
+        client.close();
       }
     });
   }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/webhdfs/DataNodeUGIProvider.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/webhdfs/DataNodeUGIProvider.java
index 93e24201b6173..a0ef7fc8ab247 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/webhdfs/DataNodeUGIProvider.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/webhdfs/DataNodeUGIProvider.java
@@ -30,7 +30,6 @@
 import java.io.ByteArrayInputStream;
 import java.io.DataInputStream;
 import java.io.IOException;
-import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 
@@ -78,13 +77,7 @@ UserGroupInformation ugi() throws IOException {
       // This makes it possible to access the data stored in secure DataNode
       // through insecure Namenode.
       if (UserGroupInformation.isSecurityEnabled() && token != null) {
-        ugi = ugiCache.get(buildTokenCacheKey(token),
-            new Callable<UserGroupInformation>() {
-              @Override
-              public UserGroupInformation call() throws Exception {
-                return tokenUGI(token);
-              }
-            });
+        ugi = ugiCache.get(buildTokenCacheKey(token), () -> tokenUGI(token));
       } else {
         final String usernameFromQuery = params.userName();
         final String doAsUserFromQuery = params.doAsUser();
@@ -92,15 +85,8 @@ public UserGroupInformation call() throws Exception {
             .getDefaultWebUserName(params.conf()) // not specified in request
             : usernameFromQuery;
 
-        ugi = ugiCache.get(
-            buildNonTokenCacheKey(doAsUserFromQuery, remoteUser),
-            new Callable<UserGroupInformation>() {
-              @Override
-              public UserGroupInformation call() throws Exception {
-                return nonTokenUGI(usernameFromQuery, doAsUserFromQuery,
-                    remoteUser);
-              }
-            });
+        ugi = ugiCache.get(buildNonTokenCacheKey(doAsUserFromQuery, remoteUser),
+            () -> nonTokenUGI(usernameFromQuery, doAsUserFromQuery, remoteUser));
       }
     } catch (ExecutionException e) {
       Throwable cause = e.getCause();
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/webhdfs/WebHdfsHandler.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/webhdfs/WebHdfsHandler.java
index 8de736ac0e237..d08dbfb772de5 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/webhdfs/WebHdfsHandler.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/webhdfs/WebHdfsHandler.java
@@ -130,25 +130,21 @@ public void channelRead0(final ChannelHandlerContext ctx,
     path = params.path();
 
     injectToken();
-    ugi.doAs(new PrivilegedExceptionAction<Void>() {
-      @Override
-      public Void run() throws Exception {
+    ugi.doAs((PrivilegedExceptionAction<Void>) () -> {
+      try {
+        handle(ctx, req);
+      } finally {
+        String host;
         try {
-          handle(ctx, req);
-        } finally {
-          String host = null;
-          try {
-            host = ((InetSocketAddress)ctx.channel().remoteAddress()).
-                getAddress().getHostAddress();
-          } catch (Exception e) {
-            LOG.warn("Error retrieving hostname: ", e);
-            host = "unknown";
-          }
-          REQLOG.info(host + " " + req.method() + " "  + req.uri() + " " +
-              getResponseCode());
+          host = ((InetSocketAddress) ctx.channel().remoteAddress())
+              .getAddress().getHostAddress();
+        } catch (Exception e) {
+          LOG.warn("Error retrieving hostname: ", e);
+          host = "unknown";
         }
-        return null;
+        REQLOG.info(host + " " + req.method() + " "  + req.uri() + " " + getResponseCode());
       }
+      return null;
     });
   }