diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/AclTransformation.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/AclTransformation.java
index 83ca54e0bb21c..288fddc02bd9f 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/AclTransformation.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/AclTransformation.java
@@ -246,19 +246,14 @@ private AclTransformation() {
    * All access ACL entries sort ahead of all default ACL entries.
    */
   static final Comparator<AclEntry> ACL_ENTRY_COMPARATOR =
-    new Comparator<AclEntry>() {
-      @Override
-      public int compare(AclEntry entry1, AclEntry entry2) {
-        return ComparisonChain.start()
+      (entry1, entry2) -> ComparisonChain.start()
           .compare(entry1.getScope(), entry2.getScope(),
-            Ordering.explicit(ACCESS, DEFAULT))
+              Ordering.explicit(ACCESS, DEFAULT))
           .compare(entry1.getType(), entry2.getType(),
-            Ordering.explicit(USER, GROUP, MASK, OTHER))
+              Ordering.explicit(USER, GROUP, MASK, OTHER))
           .compare(entry1.getName(), entry2.getName(),
-            Ordering.natural().nullsFirst())
+              Ordering.natural().nullsFirst())
           .result();
-      }
-    };
 
   /**
    * Builds the final list of ACL entries to return by trimming, sorting and
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/DefaultAuditLogger.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/DefaultAuditLogger.java
index 9ac0bec44cae0..49f6ed3dc690f 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/DefaultAuditLogger.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/DefaultAuditLogger.java
@@ -39,12 +39,7 @@
 @InterfaceStability.Evolving
 public abstract class DefaultAuditLogger extends HdfsAuditLogger {
   protected static final ThreadLocal<StringBuilder> STRING_BUILDER =
-      new ThreadLocal<StringBuilder>() {
-        @Override
-        protected StringBuilder initialValue() {
-          return new StringBuilder();
-        }
-      };
+      ThreadLocal.withInitial(StringBuilder::new);
 
   protected volatile boolean isCallerContextEnabled;
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileInputStream.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileInputStream.java
index ba4f32fd2154d..cf03df17f9e9a 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileInputStream.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileInputStream.java
@@ -28,7 +28,6 @@
 import java.net.HttpURLConnection;
 import java.net.URL;
 import java.nio.file.Files;
-import java.security.PrivilegedExceptionAction;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -478,41 +477,33 @@ public URLLog(URLConnectionFactory connectionFactory, URL url) {
 
     @Override
     public InputStream getInputStream() throws IOException {
-      return SecurityUtil.doAsCurrentUser(
-          new PrivilegedExceptionAction<InputStream>() {
-            @Override
-            public InputStream run() throws IOException {
-              HttpURLConnection connection;
-              try {
-                connection = (HttpURLConnection)
-                    connectionFactory.openConnection(url, isSpnegoEnabled);
-              } catch (AuthenticationException e) {
-                throw new IOException(e);
-              }
-              
-              if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
-                throw new HttpGetFailedException(
-                    "Fetch of " + url +
-                    " failed with status code " + connection.getResponseCode() +
-                    "\nResponse message:\n" + connection.getResponseMessage(),
-                    connection);
-              }
-        
-              String contentLength = connection.getHeaderField(CONTENT_LENGTH);
-              if (contentLength != null) {
-                advertisedSize = Long.parseLong(contentLength);
-                if (advertisedSize <= 0) {
-                  throw new IOException("Invalid " + CONTENT_LENGTH + " header: " +
-                      contentLength);
-                }
-              } else {
-                throw new IOException(CONTENT_LENGTH + " header is not provided " +
-                                      "by the server when trying to fetch " + url);
-              }
-        
-              return connection.getInputStream();
-            }
-          });
+      return SecurityUtil.doAsCurrentUser(() -> {
+        HttpURLConnection connection;
+        try {
+          connection = (HttpURLConnection) connectionFactory.openConnection(url, isSpnegoEnabled);
+        } catch (AuthenticationException e) {
+          throw new IOException(e);
+        }
+
+        if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
+          throw new HttpGetFailedException("Fetch of " + url +
+              " failed with status code " + connection.getResponseCode() +
+              "\nResponse message:\n" + connection.getResponseMessage(), connection);
+        }
+
+        String contentLength = connection.getHeaderField(CONTENT_LENGTH);
+        if (contentLength != null) {
+          advertisedSize = Long.parseLong(contentLength);
+          if (advertisedSize <= 0) {
+            throw new IOException("Invalid " + CONTENT_LENGTH + " header: " + contentLength);
+          }
+        } else {
+          throw new IOException(CONTENT_LENGTH + " header is not provided " +
+              "by the server when trying to fetch " + url);
+        }
+
+        return connection.getInputStream();
+      });
     }
 
     @Override
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirEncryptionZoneOp.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirEncryptionZoneOp.java
index 2110a408b0877..1a8ead563f5d4 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirEncryptionZoneOp.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirEncryptionZoneOp.java
@@ -21,7 +21,6 @@
 
 import java.io.IOException;
 import java.security.GeneralSecurityException;
-import java.security.PrivilegedExceptionAction;
 import java.util.AbstractMap;
 import java.util.concurrent.ExecutorService;
 import java.util.EnumSet;
@@ -94,14 +93,11 @@ private static EncryptedKeyVersion generateEncryptedDataEncryptionKey(
     // KMS does not need configuration to allow non-hdfs user GENERATE_EEK
     // operation.
     EncryptedKeyVersion edek = SecurityUtil.doAsLoginUser(
-        new PrivilegedExceptionAction<EncryptedKeyVersion>() {
-          @Override
-          public EncryptedKeyVersion run() throws IOException {
-            try {
-              return fsd.getProvider().generateEncryptedKey(ezKeyName);
-            } catch (GeneralSecurityException e) {
-              throw new IOException(e);
-            }
+        () -> {
+          try {
+            return fsd.getProvider().generateEncryptedKey(ezKeyName);
+          } catch (GeneralSecurityException e) {
+            throw new IOException(e);
           }
         });
     long generateEDEKTime = monotonicNow() - generateEDEKStartTime;
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirErasureCodingOp.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirErasureCodingOp.java
index 6628b56a132e0..8bdeca3ccad7b 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirErasureCodingOp.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirErasureCodingOp.java
@@ -76,9 +76,7 @@ static ErasureCodingPolicy getEnabledErasureCodingPolicyByName(
         .getEnabledPolicyByName(ecPolicyName);
     if (ecPolicy == null) {
       final String sysPolicies =
-          Arrays.asList(
-              fsn.getErasureCodingPolicyManager().getEnabledPolicies())
-              .stream()
+          Arrays.stream(fsn.getErasureCodingPolicyManager().getEnabledPolicies())
               .map(ErasureCodingPolicy::getName)
               .collect(Collectors.joining(", "));
       final String message = String.format("Policy '%s' does not match any " +
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java
index c8e0cd224e1af..cd592238ad9c2 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java
@@ -125,7 +125,6 @@
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.io.Writable;
 import org.apache.hadoop.io.WritableFactories;
-import org.apache.hadoop.io.WritableFactory;
 import org.apache.hadoop.io.erasurecode.ECSchema;
 import org.apache.hadoop.io.erasurecode.ErasureCodeConstants;
 import org.apache.hadoop.ipc.ClientId;
@@ -158,12 +157,7 @@ public abstract class FSEditLogOp {
 
   public static class OpInstanceCache {
     private static final ThreadLocal<OpInstanceCacheMap> CACHE =
-        new ThreadLocal<OpInstanceCacheMap>() {
-      @Override
-      protected OpInstanceCacheMap initialValue() {
-        return new OpInstanceCacheMap();
-      }
-    };
+        ThreadLocal.withInitial(OpInstanceCacheMap::new);
 
     @SuppressWarnings("serial")
     static final class OpInstanceCacheMap extends
@@ -4467,12 +4461,7 @@ static class BlockTwo implements Writable {
     long len;
 
     static {                                      // register a ctor
-      WritableFactories.setFactory
-        (BlockTwo.class,
-         new WritableFactory() {
-           @Override
-           public Writable newInstance() { return new BlockTwo(); }
-         });
+      WritableFactories.setFactory(BlockTwo.class, BlockTwo::new);
     }
 
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormatPBINode.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormatPBINode.java
index 3f0c9faa97c9a..5b14afc73ad12 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormatPBINode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormatPBINode.java
@@ -307,20 +307,8 @@ private void fillUpInodeList(ArrayList<INode> inodeList, INode inode) {
 
     private void addToCacheAndBlockMap(final ArrayList<INode> inodeList) {
       final ArrayList<INode> inodes = new ArrayList<>(inodeList);
-      nameCacheUpdateExecutor.submit(
-          new Runnable() {
-            @Override
-            public void run() {
-              addToCacheInternal(inodes);
-            }
-          });
-      blocksMapUpdateExecutor.submit(
-          new Runnable() {
-            @Override
-            public void run() {
-              updateBlockMapInternal(inodes);
-            }
-          });
+      nameCacheUpdateExecutor.submit(() -> addToCacheInternal(inodes));
+      blocksMapUpdateExecutor.submit(() -> updateBlockMapInternal(inodes));
     }
 
     // update name cache with non-thread safe
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormatProtobuf.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormatProtobuf.java
index 58c24d4377be0..b0b46d7d56be3 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormatProtobuf.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormatProtobuf.java
@@ -34,8 +34,6 @@
 import java.security.DigestOutputStream;
 import java.security.MessageDigest;
 import java.util.ArrayList;
-import java.util.Collections;
-import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -377,18 +375,15 @@ private void loadInternal(RandomAccessFile raFile, FileInputStream fin)
 
       ArrayList<FileSummary.Section> sections = Lists.newArrayList(summary
           .getSectionsList());
-      Collections.sort(sections, new Comparator<FileSummary.Section>() {
-        @Override
-        public int compare(FileSummary.Section s1, FileSummary.Section s2) {
-          SectionName n1 = SectionName.fromString(s1.getName());
-          SectionName n2 = SectionName.fromString(s2.getName());
-          if (n1 == null) {
-            return n2 == null ? 0 : -1;
-          } else if (n2 == null) {
-            return -1;
-          } else {
-            return n1.ordinal() - n2.ordinal();
-          }
+      sections.sort((s1, s2) -> {
+        SectionName n1 = SectionName.fromString(s1.getName());
+        SectionName n2 = SectionName.fromString(s2.getName());
+        if (n1 == null) {
+          return n2 == null ? 0 : -1;
+        } else if (n2 == null) {
+          return -1;
+        } else {
+          return n1.ordinal() - n2.ordinal();
         }
       });
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageSerialization.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageSerialization.java
index 404f2c73ad3a2..b1cd36f4785da 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageSerialization.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageSerialization.java
@@ -75,13 +75,7 @@ private FSImageSerialization() {}
    * in this class should be thread-safe since image-saving is multithreaded, so 
    * we need to keep the static objects in a thread-local.
    */
-  static private final ThreadLocal<TLData> TL_DATA =
-    new ThreadLocal<TLData>() {
-    @Override
-    protected TLData initialValue() {
-      return new TLData();
-    }
-  };
+  static private final ThreadLocal<TLData> TL_DATA = ThreadLocal.withInitial(TLData::new);
 
   /**
    * Simple container "struct" for threadlocal data.
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
index 347fec858675d..f5a301947c950 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
@@ -6736,12 +6736,7 @@ public String getNodeUsage() {
         new HashMap<String, Map<String,Object>>();
     final List<DatanodeDescriptor> live = new ArrayList<DatanodeDescriptor>();
     blockManager.getDatanodeManager().fetchDatanodes(live, null, true);
-    for (Iterator<DatanodeDescriptor> it = live.iterator(); it.hasNext();) {
-      DatanodeDescriptor node = it.next();
-      if (!node.isInService()) {
-        it.remove();
-      }
-    }
+    live.removeIf(node -> !node.isInService());
 
     if (live.size() > 0) {
       float totalDfsUsed = 0;
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystemLock.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystemLock.java
index e510bd625e738..f4d9425a6a691 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystemLock.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystemLock.java
@@ -93,12 +93,7 @@ class FSNamesystemLock {
    * many read locks held simultaneously.
    */
   private final ThreadLocal<Long> readLockHeldTimeStampNanos =
-      new ThreadLocal<Long>() {
-        @Override
-        public Long initialValue() {
-          return Long.MAX_VALUE;
-        }
-      };
+      ThreadLocal.withInitial(() -> Long.MAX_VALUE);
   private final AtomicInteger numReadLockWarningsSuppressed =
       new AtomicInteger(0);
   /** Time stamp (ms) of the last time a read lock report was written. */
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FileJournalManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FileJournalManager.java
index 42a5d2d7385bf..13ddbd6073077 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FileJournalManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FileJournalManager.java
@@ -537,16 +537,11 @@ public static class EditLogFile {
     private boolean hasCorruptHeader = false;
     private final boolean isInProgress;
 
-    final static Comparator<EditLogFile> COMPARE_BY_START_TXID 
-      = new Comparator<EditLogFile>() {
-      @Override
-      public int compare(EditLogFile a, EditLogFile b) {
-        return ComparisonChain.start()
-        .compare(a.getFirstTxId(), b.getFirstTxId())
-        .compare(a.getLastTxId(), b.getLastTxId())
-        .result();
-      }
-    };
+    final static Comparator<EditLogFile> COMPARE_BY_START_TXID =
+        (a, b) -> ComparisonChain.start()
+            .compare(a.getFirstTxId(), b.getFirstTxId())
+            .compare(a.getLastTxId(), b.getLastTxId())
+            .result();
 
     EditLogFile(File file,
         long firstTxId, long lastTxId) {
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FsImageValidation.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FsImageValidation.java
index 3325222267d5d..6f226f3aa00fa 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FsImageValidation.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FsImageValidation.java
@@ -48,7 +48,6 @@
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.Collections;
-import java.util.Iterator;
 import java.util.Timer;
 import java.util.TimerTask;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -148,19 +147,16 @@ static String toCommaSeparatedNumber(long n) {
     /** @return a filter for the given type. */
     static FilenameFilter newFilenameFilter(NameNodeFile type) {
       final String prefix = type.getName() + "_";
-      return new FilenameFilter() {
-        @Override
-        public boolean accept(File dir, String name) {
-          if (!name.startsWith(prefix)) {
+      return (dir, name) -> {
+        if (!name.startsWith(prefix)) {
+          return false;
+        }
+        for (int i = prefix.length(); i < name.length(); i++) {
+          if (!Character.isDigit(name.charAt(i))) {
             return false;
           }
-          for (int i = prefix.length(); i < name.length(); i++) {
-            if (!Character.isDigit(name.charAt(i))) {
-              return false;
-            }
-          }
-          return true;
         }
+        return true;
       };
     }
   }
@@ -264,12 +260,7 @@ FSNamesystem checkINodeReference(Configuration conf,
 
   static class INodeMapValidation {
     static Iterable<INodeWithAdditionalFields> iterate(INodeMap map) {
-      return new Iterable<INodeWithAdditionalFields>() {
-        @Override
-        public Iterator<INodeWithAdditionalFields> iterator() {
-          return map.getMapIterator();
-        }
-      };
+      return map::getMapIterator;
     }
 
     static void run(FSDirectory fsdir, AtomicInteger errorCount) {
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodeReference.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodeReference.java
index 6e655f7a13408..aa1a9614ce091 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodeReference.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodeReference.java
@@ -388,13 +388,8 @@ public static class WithCount extends INodeReference {
      * Compare snapshot with IDs, where null indicates the current status thus
      * is greater than any non-null snapshot.
      */
-    public static final Comparator<WithName> WITHNAME_COMPARATOR
-        = new Comparator<WithName>() {
-      @Override
-      public int compare(WithName left, WithName right) {
-        return left.lastSnapshotId - right.lastSnapshotId;
-      }
-    };
+    public static final Comparator<WithName> WITHNAME_COMPARATOR =
+        Comparator.comparingInt(left -> left.lastSnapshotId);
     
     public WithCount(INodeReference parent, INode referred) {
       super(parent, referred);
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ImageServlet.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ImageServlet.java
index 442c1aba95b1c..b7734add740bf 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ImageServlet.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ImageServlet.java
@@ -565,135 +565,117 @@ protected void doPut(final HttpServletRequest request,
       validateRequest(context, conf, request, response, nnImage,
           parsedParams.getStorageInfoString());
 
-      UserGroupInformation.getCurrentUser().doAs(
-          new PrivilegedExceptionAction<Void>() {
-
-            @Override
-            public Void run() throws Exception {
-              // if its not the active NN, then we need to notify the caller it was was the wrong
-              // target (regardless of the fact that we got the image)
-              HAServiceProtocol.HAServiceState state = NameNodeHttpServer
-                  .getNameNodeStateFromContext(getServletContext());
-              if (state != HAServiceProtocol.HAServiceState.ACTIVE &&
-                  state != HAServiceProtocol.HAServiceState.OBSERVER) {
-                // we need a different response type here so the client can differentiate this
-                // from the failure to upload due to (1) security, or (2) other checkpoints already
-                // present
-                sendError(response, HttpServletResponse.SC_EXPECTATION_FAILED,
-                    "Nameode "+request.getLocalAddr()+" is currently not in a state which can "
-                        + "accept uploads of new fsimages. State: "+state);
-                return null;
-              }
-
-              final long txid = parsedParams.getTxId();
-              String remoteAddr = request.getRemoteAddr();
-              ImageUploadRequest imageRequest = new ImageUploadRequest(txid, remoteAddr);
-
-              final NameNodeFile nnf = parsedParams.getNameNodeFile();
-
-              // if the node is attempting to upload an older transaction, we ignore it
-              SortedSet<ImageUploadRequest> larger = currentlyDownloadingCheckpoints.tailSet(imageRequest);
-              if (larger.size() > 0) {
-                sendError(response, HttpServletResponse.SC_CONFLICT,
-                    "Another checkpointer is already in the process of uploading a" +
-                        " checkpoint made up to transaction ID " + larger.last());
-                return null;
-              }
-
-              //make sure no one else has started uploading one
-              if (!currentlyDownloadingCheckpoints.add(imageRequest)) {
-                sendError(response, HttpServletResponse.SC_CONFLICT,
-                    "Either current namenode is checkpointing or another"
-                        + " checkpointer is already in the process of "
-                        + "uploading a checkpoint made at transaction ID "
-                        + txid);
-                return null;
-              }
-
-              long now = System.currentTimeMillis();
-              long lastCheckpointTime =
-                  nnImage.getStorage().getMostRecentCheckpointTime();
-              long lastCheckpointTxid =
-                  nnImage.getStorage().getMostRecentCheckpointTxId();
-
-              long checkpointPeriod =
-                  conf.getTimeDuration(DFS_NAMENODE_CHECKPOINT_PERIOD_KEY,
-                      DFS_NAMENODE_CHECKPOINT_PERIOD_DEFAULT, TimeUnit.SECONDS);
-              checkpointPeriod = Math.round(
-                  checkpointPeriod * recentImageCheckTimePrecision);
-
-              long checkpointTxnCount =
-                  conf.getLong(DFS_NAMENODE_CHECKPOINT_TXNS_KEY,
-                      DFS_NAMENODE_CHECKPOINT_TXNS_DEFAULT);
-
-              long timeDelta = TimeUnit.MILLISECONDS.toSeconds(
-                  now - lastCheckpointTime);
-
-              // Since the goal of the check below is to prevent overly
-              // frequent upload from Standby, the check should only be done
-              // for the periodical upload from Standby. For the other
-              // scenarios such as rollback image and ckpt file, they skip
-              // this check, see HDFS-15036 for more info.
-              if (checkRecentImageEnable &&
-                  NameNodeFile.IMAGE.equals(parsedParams.getNameNodeFile()) &&
-                  timeDelta < checkpointPeriod &&
-                  txid - lastCheckpointTxid < checkpointTxnCount) {
-                // only when at least one of two conditions are met we accept
-                // a new fsImage
-                // 1. most recent image's txid is too far behind
-                // 2. last checkpoint time was too old
-                String message = "Rejecting a fsimage due to small time delta "
-                    + "and txnid delta. Time since previous checkpoint is "
-                    + timeDelta + " expecting at least " + checkpointPeriod
-                    + " txnid delta since previous checkpoint is " +
-                    (txid - lastCheckpointTxid) + " expecting at least "
-                    + checkpointTxnCount;
-                LOG.info(message);
-                sendError(response, HttpServletResponse.SC_CONFLICT, message);
-                return null;
-              }
-
-              try {
-                if (nnImage.getStorage().findImageFile(nnf, txid) != null) {
-                  String message = "Either current namenode has checkpointed or "
-                      + "another checkpointer already uploaded an "
-                      + "checkpoint for txid " + txid;
-                  LOG.info(message);
-                  sendError(response, HttpServletResponse.SC_CONFLICT, message);
-                  return null;
-                }
-
-                InputStream stream = request.getInputStream();
-                try {
-                  long start = monotonicNow();
-                  MD5Hash downloadImageDigest = TransferFsImage
-                      .handleUploadImageRequest(request, txid,
-                          nnImage.getStorage(), stream,
-                          parsedParams.getFileSize(), getThrottler(conf));
-                  nnImage.saveDigestAndRenameCheckpointImage(nnf, txid,
-                      downloadImageDigest);
-                  // Metrics non-null only when used inside name node
-                  if (metrics != null) {
-                    long elapsed = monotonicNow() - start;
-                    metrics.addPutImage(elapsed);
-                  }
-                  // Now that we have a new checkpoint, we might be able to
-                  // remove some old ones.
-                  nnImage.purgeOldStorage(nnf);
-                } finally {
-                  // remove the request once we've processed it, or it threw an error, so we
-                  // aren't using it either
-                  currentlyDownloadingCheckpoints.remove(imageRequest);
-
-                  stream.close();
-                }
-              } finally {
-                nnImage.removeFromCheckpointing(txid);
-              }
-              return null;
-            }
+      UserGroupInformation.getCurrentUser().doAs((PrivilegedExceptionAction<Void>) () -> {
+        // if its not the active NN, then we need to notify the caller it was was the wrong
+        // target (regardless of the fact that we got the image)
+        HAServiceProtocol.HAServiceState state = NameNodeHttpServer
+            .getNameNodeStateFromContext(getServletContext());
+        if (state != HAServiceProtocol.HAServiceState.ACTIVE &&
+            state != HAServiceProtocol.HAServiceState.OBSERVER) {
+          // we need a different response type here so the client can differentiate this
+          // from the failure to upload due to (1) security, or (2) other checkpoints already
+          // present
+          sendError(response, HttpServletResponse.SC_EXPECTATION_FAILED,
+              "Nameode "+request.getLocalAddr()+" is currently not in a state which can "
+                  + "accept uploads of new fsimages. State: "+state);
+          return null;
+        }
+
+        final long txid = parsedParams.getTxId();
+        String remoteAddr = request.getRemoteAddr();
+        ImageUploadRequest imageRequest = new ImageUploadRequest(txid, remoteAddr);
 
-          });
+        final NameNodeFile nnf = parsedParams.getNameNodeFile();
+
+        // if the node is attempting to upload an older transaction, we ignore it
+        SortedSet<ImageUploadRequest> larger =
+            currentlyDownloadingCheckpoints.tailSet(imageRequest);
+        if (larger.size() > 0) {
+          sendError(response, HttpServletResponse.SC_CONFLICT,
+              "Another checkpointer is already in the process of uploading a" +
+                  " checkpoint made up to transaction ID " + larger.last());
+          return null;
+        }
+
+        //make sure no one else has started uploading one
+        if (!currentlyDownloadingCheckpoints.add(imageRequest)) {
+          sendError(response, HttpServletResponse.SC_CONFLICT,
+              "Either current namenode is checkpointing or another"
+                  + " checkpointer is already in the process of "
+                  + "uploading a checkpoint made at transaction ID "
+                  + txid);
+          return null;
+        }
+
+        long now = System.currentTimeMillis();
+        long lastCheckpointTime = nnImage.getStorage().getMostRecentCheckpointTime();
+        long lastCheckpointTxid = nnImage.getStorage().getMostRecentCheckpointTxId();
+
+        long checkpointPeriod = conf.getTimeDuration(DFS_NAMENODE_CHECKPOINT_PERIOD_KEY,
+            DFS_NAMENODE_CHECKPOINT_PERIOD_DEFAULT, TimeUnit.SECONDS);
+        checkpointPeriod = Math.round(checkpointPeriod * recentImageCheckTimePrecision);
+
+        long checkpointTxnCount = conf.getLong(DFS_NAMENODE_CHECKPOINT_TXNS_KEY,
+            DFS_NAMENODE_CHECKPOINT_TXNS_DEFAULT);
+
+        long timeDelta = TimeUnit.MILLISECONDS.toSeconds(now - lastCheckpointTime);
+
+        // Since the goal of the check below is to prevent overly
+        // frequent upload from Standby, the check should only be done
+        // for the periodical upload from Standby. For the other
+        // scenarios such as rollback image and ckpt file, they skip
+        // this check, see HDFS-15036 for more info.
+        if (checkRecentImageEnable && NameNodeFile.IMAGE.equals(parsedParams.getNameNodeFile()) &&
+            timeDelta < checkpointPeriod && txid - lastCheckpointTxid < checkpointTxnCount) {
+          // only when at least one of two conditions are met we accept
+          // a new fsImage
+          // 1. most recent image's txid is too far behind
+          // 2. last checkpoint time was too old
+          String message = "Rejecting a fsimage due to small time delta "
+              + "and txnid delta. Time since previous checkpoint is "
+              + timeDelta + " expecting at least " + checkpointPeriod
+              + " txnid delta since previous checkpoint is " +
+              (txid - lastCheckpointTxid) + " expecting at least "
+              + checkpointTxnCount;
+          LOG.info(message);
+          sendError(response, HttpServletResponse.SC_CONFLICT, message);
+          return null;
+        }
+
+        try {
+          if (nnImage.getStorage().findImageFile(nnf, txid) != null) {
+            String message = "Either current namenode has checkpointed or "
+                + "another checkpointer already uploaded an "
+                + "checkpoint for txid " + txid;
+            LOG.info(message);
+            sendError(response, HttpServletResponse.SC_CONFLICT, message);
+            return null;
+          }
+
+          try (InputStream stream = request.getInputStream()) {
+            long start = monotonicNow();
+            MD5Hash downloadImageDigest = TransferFsImage.handleUploadImageRequest(
+                request, txid, nnImage.getStorage(), stream,
+                parsedParams.getFileSize(), getThrottler(conf));
+            nnImage.saveDigestAndRenameCheckpointImage(nnf, txid, downloadImageDigest);
+            // Metrics non-null only when used inside name node
+            if (metrics != null) {
+              long elapsed = monotonicNow() - start;
+              metrics.addPutImage(elapsed);
+            }
+            // Now that we have a new checkpoint, we might be able to
+            // remove some old ones.
+            nnImage.purgeOldStorage(nnf);
+          } finally {
+            // remove the request once we've processed it, or it threw an error, so we
+            // aren't using it either
+            currentlyDownloadingCheckpoints.remove(imageRequest);
+          }
+        } finally {
+          nnImage.removeFromCheckpointing(txid);
+        }
+        return null;
+      });
     } catch (Throwable t) {
       String errMsg = "PutImage failed. " + StringUtils.stringifyException(t);
       sendError(response, HttpServletResponse.SC_GONE, errMsg);
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/LeaseManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/LeaseManager.java
index b21a34a932af9..77acba586508e 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/LeaseManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/LeaseManager.java
@@ -223,25 +223,21 @@ public Set<INodesInPath> getINodeWithLeases(final INodeDirectory
         Executors.newFixedThreadPool(workerCount);
     for (int workerIdx = 0; workerIdx < workerCount; workerIdx++) {
       final int startIdx = workerIdx;
-      Callable<List<INodesInPath>> c = new Callable<List<INodesInPath>>() {
-        @Override
-        public List<INodesInPath> call() {
-          List<INodesInPath> iNodesInPaths = Lists.newArrayList();
-          for (int idx = startIdx; idx < inodeCount; idx += workerCount) {
-            INode inode = inodes[idx];
-            if (!inode.isFile()) {
-              continue;
-            }
-            INodesInPath inodesInPath = INodesInPath.fromINode(
-                fsnamesystem.getFSDirectory().getRoot(), inode.asFile());
-            if (ancestorDir != null &&
-                !inodesInPath.isDescendant(ancestorDir)) {
-              continue;
-            }
-            iNodesInPaths.add(inodesInPath);
+      Callable<List<INodesInPath>> c = () -> {
+        List<INodesInPath> iNodesInPaths = Lists.newArrayList();
+        for (int idx = startIdx; idx < inodeCount; idx += workerCount) {
+          INode inode = inodes[idx];
+          if (!inode.isFile()) {
+            continue;
+          }
+          INodesInPath inodesInPath = INodesInPath.fromINode(
+              fsnamesystem.getFSDirectory().getRoot(), inode.asFile());
+          if (ancestorDir != null && !inodesInPath.isDescendant(ancestorDir)) {
+            continue;
           }
-          return iNodesInPaths;
+          iNodesInPaths.add(inodesInPath);
         }
+        return iNodesInPaths;
       };
 
       // Submit the inode filter task to the Executor Service
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NNStorageRetentionManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NNStorageRetentionManager.java
index b81cfccd75734..aa80b60093245 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NNStorageRetentionManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NNStorageRetentionManager.java
@@ -18,11 +18,9 @@
 package org.apache.hadoop.hdfs.server.namenode;
 
 import java.io.File;
-import java.io.FilenameFilter;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collections;
-import java.util.Comparator;
 import java.util.EnumSet;
 import java.util.Iterator;
 import java.util.List;
@@ -134,15 +132,10 @@ void purgeOldStorage(NameNodeFile nnf) throws IOException {
     
     ArrayList<EditLogInputStream> editLogs = new ArrayList<EditLogInputStream>();
     purgeableLogs.selectInputStreams(editLogs, purgeLogsFrom, false, false);
-    Collections.sort(editLogs, new Comparator<EditLogInputStream>() {
-      @Override
-      public int compare(EditLogInputStream a, EditLogInputStream b) {
-        return ComparisonChain.start()
-            .compare(a.getFirstTxId(), b.getFirstTxId())
-            .compare(a.getLastTxId(), b.getLastTxId())
-            .result();
-      }
-    });
+    editLogs.sort((a, b) -> ComparisonChain.start()
+        .compare(a.getFirstTxId(), b.getFirstTxId())
+        .compare(a.getLastTxId(), b.getLastTxId())
+        .result());
 
     // Remove from consideration any edit logs that are in fact required.
     while (editLogs.size() > 0 &&
@@ -256,12 +249,8 @@ void purgeOldLegacyOIVImages(String dir, long txid) {
     String filesInStorage[];
 
     // Get the listing
-    filesInStorage = oivImageDir.list(new FilenameFilter() {
-      @Override
-      public boolean accept(File dir, String name) {
-        return name.matches(oivImagePrefix + "_(\\d+)");
-      }
-    });
+    filesInStorage = oivImageDir.list(
+        (dir1, name) -> name.matches(oivImagePrefix + "_(\\d+)"));
 
     // Check whether there is any work to do.
     if (filesInStorage != null
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java
index 63c7721b7493c..7ed3dbd140daa 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java
@@ -112,7 +112,6 @@
 import java.io.PrintStream;
 import java.net.InetSocketAddress;
 import java.net.URI;
-import java.security.PrivilegedExceptionAction;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -1032,13 +1031,10 @@ private void startTrashEmptier(final Configuration conf) throws IOException {
     // case the current user is the administrator, not the NN. The trash
     // emptier needs to run as the NN. See HDFS-3972.
     FileSystem fs = SecurityUtil.doAsLoginUser(
-        new PrivilegedExceptionAction<FileSystem>() {
-          @Override
-          public FileSystem run() throws IOException {
-            FileSystem dfs = new DistributedFileSystem();
-            dfs.initialize(FileSystem.getDefaultUri(conf), conf);
-            return dfs;
-          }
+        () -> {
+          FileSystem dfs = new DistributedFileSystem();
+          dfs.initialize(FileSystem.getDefaultUri(conf), conf);
+          return dfs;
         });
     this.emptier = new Thread(new Trash(fs, conf).getEmptier(), "Trash Emptier");
     this.emptier.setDaemon(true);
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeRpcServer.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeRpcServer.java
index b19bfc13acf65..124be95cdf428 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeRpcServer.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeRpcServer.java
@@ -1694,18 +1694,14 @@ public void blockReceivedAndDeleted(final DatanodeRegistration nodeReg,
         nodeReg, receivedAndDeletedBlocks.length);
     final BlockManager bm = namesystem.getBlockManager();
     for (final StorageReceivedDeletedBlocks r : receivedAndDeletedBlocks) {
-      bm.enqueueBlockOp(new Runnable() {
-        @Override
-        public void run() {
-          try {
-            namesystem.processIncrementalBlockReport(nodeReg, r);
-          } catch (Exception ex) {
-            // usually because the node is unregistered/dead.  next heartbeat
-            // will correct the problem
-            blockStateChangeLog.error(
-                "*BLOCK* NameNode.blockReceivedAndDeleted: "
-                    + "failed from " + nodeReg + ": " + ex.getMessage());
-          }
+      bm.enqueueBlockOp(() -> {
+        try {
+          namesystem.processIncrementalBlockReport(nodeReg, r);
+        } catch (Exception ex) {
+          // usually because the node is unregistered/dead.  next heartbeat
+          // will correct the problem
+          blockStateChangeLog.error("*BLOCK* NameNode.blockReceivedAndDeleted: "
+              + "failed from " + nodeReg + ": " + ex.getMessage());
         }
       });
     }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NamenodeFsck.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NamenodeFsck.java
index 1e8517edecad1..f6a5bc4802b3c 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NamenodeFsck.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NamenodeFsck.java
@@ -51,11 +51,9 @@
 import org.apache.hadoop.hdfs.DFSClient;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DFSUtilClient;
-import org.apache.hadoop.hdfs.RemotePeerFactory;
 import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys;
 import org.apache.hadoop.hdfs.net.Peer;
 import org.apache.hadoop.hdfs.protocol.Block;
-import org.apache.hadoop.hdfs.protocol.DatanodeID;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfoWithStorage;
 import org.apache.hadoop.hdfs.protocol.DirectoryListing;
@@ -67,7 +65,6 @@
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
 import org.apache.hadoop.hdfs.protocol.SnapshottableDirectoryStatus;
 import org.apache.hadoop.hdfs.protocol.datatransfer.sasl.DataEncryptionKeyFactory;
-import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier;
 import org.apache.hadoop.hdfs.security.token.block.DataEncryptionKey;
 import org.apache.hadoop.hdfs.server.blockmanagement.BlockInfo;
 import org.apache.hadoop.hdfs.server.blockmanagement.BlockInfoStriped;
@@ -84,7 +81,6 @@
 import org.apache.hadoop.net.NodeBase;
 import org.apache.hadoop.security.AccessControlException;
 import org.apache.hadoop.security.UserGroupInformation;
-import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.tracing.TraceUtils;
 import org.apache.hadoop.util.Time;
 import org.apache.hadoop.tracing.Tracer;
@@ -1094,26 +1090,20 @@ private void copyBlock(final DFSClient dfs, LocatedBlock lblock,
             setCachingStrategy(CachingStrategy.newDropBehind()).
             setClientCacheContext(dfs.getClientContext()).
             setConfiguration(namenode.getConf()).
-            setRemotePeerFactory(new RemotePeerFactory() {
-              @Override
-              public Peer newConnectedPeer(InetSocketAddress addr,
-                  Token<BlockTokenIdentifier> blockToken, DatanodeID datanodeId)
-                  throws IOException {
-                Peer peer = null;
-                Socket s = NetUtils.getDefaultSocketFactory(conf).createSocket();
-                try {
-                  s.connect(addr, HdfsConstants.READ_TIMEOUT);
-                  s.setSoTimeout(HdfsConstants.READ_TIMEOUT);
-                  peer = DFSUtilClient.peerFromSocketAndKey(
-                        dfs.getSaslDataTransferClient(), s, NamenodeFsck.this,
-                        blockToken, datanodeId, HdfsConstants.READ_TIMEOUT);
-                } finally {
-                  if (peer == null) {
-                    IOUtils.closeStream(s);
-                  }
+            setRemotePeerFactory((addr, blockToken, datanodeId) -> {
+              Peer peer = null;
+              Socket s = NetUtils.getDefaultSocketFactory(conf).createSocket();
+              try {
+                s.connect(addr, HdfsConstants.READ_TIMEOUT);
+                s.setSoTimeout(HdfsConstants.READ_TIMEOUT);
+                peer = DFSUtilClient.peerFromSocketAndKey(dfs.getSaslDataTransferClient(), s,
+                    NamenodeFsck.this, blockToken, datanodeId, HdfsConstants.READ_TIMEOUT);
+              } finally {
+                if (peer == null) {
+                  IOUtils.closeStream(s);
                 }
-                return peer;
               }
+              return peer;
             }).
             build();
       }  catch (IOException ex) {
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/SecondaryNameNode.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/SecondaryNameNode.java
index e95200b35aaa5..f0fe53dd2a20e 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/SecondaryNameNode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/SecondaryNameNode.java
@@ -25,7 +25,6 @@
 import java.net.InetSocketAddress;
 import java.net.URI;
 import java.net.URL;
-import java.security.PrivilegedAction;
 import java.security.PrivilegedExceptionAction;
 import java.util.*;
 
@@ -318,14 +317,10 @@ public void shutdown() {
 
   @Override
   public void run() {
-    SecurityUtil.doAsLoginUserOrFatal(
-        new PrivilegedAction<Object>() {
-        @Override
-        public Object run() {
-          doWork();
-          return null;
-        }
-      });
+    SecurityUtil.doAsLoginUserOrFatal(() -> {
+      doWork();
+      return null;
+    });
   }
   //
   // The main work loop
@@ -406,11 +401,8 @@ static boolean downloadCheckpointFiles(
     }
 
     try {
-        Boolean b = UserGroupInformation.getCurrentUser().doAs(
-            new PrivilegedExceptionAction<Boolean>() {
-  
-          @Override
-          public Boolean run() throws Exception {
+      return UserGroupInformation.getCurrentUser().doAs(
+          (PrivilegedExceptionAction<Boolean>) () -> {
             dstImage.getStorage().cTime = sig.cTime;
 
             // get fsimage
@@ -425,19 +417,16 @@ public Boolean run() throws Exception {
               dstImage.saveDigestAndRenameCheckpointImage(NameNodeFile.IMAGE,
                   sig.mostRecentCheckpointTxId, downloadedHash);
             }
-        
+
             // get edits file
             for (RemoteEditLog log : manifest.getLogs()) {
-              TransferFsImage.downloadEditsToStorage(
-                  nnHostPort, log, dstImage.getStorage());
+              TransferFsImage.downloadEditsToStorage(nnHostPort, log, dstImage.getStorage());
             }
-        
+
             // true if we haven't loaded all the transactions represented by the
             // downloaded fsimage.
             return dstImage.getLastAppliedTxId() < sig.mostRecentCheckpointTxId;
-          }
-        });
-        return b.booleanValue();
+          });
       } catch (InterruptedException e) {
         throw new RuntimeException(e);
       }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/StoragePolicySummary.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/StoragePolicySummary.java
index a13032de1c85d..48ecca2e268a0 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/StoragePolicySummary.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/StoragePolicySummary.java
@@ -20,8 +20,6 @@
 
 import java.text.NumberFormat;
 import java.util.Arrays;
-import java.util.Collections;
-import java.util.Comparator;
 import java.util.EnumMap;
 import java.util.Formatter;
 import java.util.HashMap;
@@ -70,14 +68,7 @@ static List<Entry<StorageTypeAllocation, Long>> sortByComparator(
     List<Entry<StorageTypeAllocation, Long>> storageAllocations = 
         new LinkedList<>(unsortMap.entrySet());
     // Sorting the list based on values
-    Collections.sort(storageAllocations, 
-      new Comparator<Entry<StorageTypeAllocation, Long>>() {
-          public int compare(Entry<StorageTypeAllocation, Long> o1,
-              Entry<StorageTypeAllocation, Long> o2)
-          {
-            return o2.getValue().compareTo(o1.getValue());
-          }
-    });
+    storageAllocations.sort((o1, o2) -> o2.getValue().compareTo(o1.getValue()));
     return storageAllocations;
   }