HDFS-16713. Improve code with Lambda in org.apache.hadoop.hdfs.server.namenode sub packages

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ha/BootstrapStandby.java

@@ -24,7 +24,6 @@
 import java.io.IOException;
 import java.net.InetSocketAddress;
 import java.net.URI;
-import java.security.PrivilegedAction;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -118,14 +117,11 @@ public int run(String[] args) throws Exception {
     SecurityUtil.login(conf, DFS_NAMENODE_KEYTAB_FILE_KEY,
         DFS_NAMENODE_KERBEROS_PRINCIPAL_KEY, myAddr.getHostName());
 
-    return SecurityUtil.doAsLoginUserOrFatal(new PrivilegedAction<Integer>() {
-      @Override
-      public Integer run() {
-        try {
-          return doRun();
-        } catch (IOException e) {
-          throw new RuntimeException(e);
-        }
+    return SecurityUtil.doAsLoginUserOrFatal(() -> {
+      try {
+        return doRun();
+      } catch (IOException e) {
+        throw new RuntimeException(e);
       }
     });
   }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ha/EditLogTailer.java

@@ -20,7 +20,6 @@
 
 import java.io.IOException;
 import java.net.InetSocketAddress;
-import java.security.PrivilegedAction;
 import java.security.PrivilegedExceptionAction;
 import java.util.Collection;
 import java.util.Collections;
@@ -299,28 +298,23 @@ public void catchupDuringFailover() throws IOException {
     // Important to do tailing as the login user, in case the shared
     // edits storage is implemented by a JournalManager that depends
     // on security credentials to access the logs (eg QuorumJournalManager).
-    SecurityUtil.doAsLoginUser(new PrivilegedExceptionAction<Void>() {
-      @Override
-      public Void run() throws Exception {
-        long editsTailed = 0;
-        // Fully tail the journal to the end
-        do {
-          long startTime = timer.monotonicNow();
-          try {
-            NameNode.getNameNodeMetrics().addEditLogTailInterval(
-                startTime - lastLoadTimeMs);
-            // It is already under the name system lock and the checkpointer
-            // thread is already stopped. No need to acquire any other lock.
-            editsTailed = doTailEdits();
-          } catch (InterruptedException e) {
-            throw new IOException(e);
-          } finally {
-            NameNode.getNameNodeMetrics().addEditLogTailTime(
-                timer.monotonicNow() - startTime);
-          }
-        } while(editsTailed > 0);
-        return null;
-      }
+    SecurityUtil.doAsLoginUser((PrivilegedExceptionAction<Void>) () -> {
+      long editsTailed = 0;
+      // Fully tail the journal to the end
+      do {
+        long startTime = timer.monotonicNow();
+        try {
+          NameNode.getNameNodeMetrics().addEditLogTailInterval(startTime - lastLoadTimeMs);
+          // It is already under the name system lock and the checkpointer
+          // thread is already stopped. No need to acquire any other lock.
+          editsTailed = doTailEdits();
+        } catch (InterruptedException e) {
+          throw new IOException(e);
+        } finally {
+          NameNode.getNameNodeMetrics().addEditLogTailTime(timer.monotonicNow() - startTime);
+        }
+      } while(editsTailed > 0);
+      return null;
     });
   }
 
@@ -482,14 +476,10 @@ private void setShouldRun(boolean shouldRun) {
 
     @Override
     public void run() {
-      SecurityUtil.doAsLoginUserOrFatal(
-          new PrivilegedAction<Object>() {
-          @Override
-          public Object run() {
-            doWork();
-            return null;
-          }
-        });
+      SecurityUtil.doAsLoginUserOrFatal(() -> {
+        doWork();
+        return null;
+      });
     }
 
     private void doWork() {

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ha/StandbyCheckpointer.java

@@ -22,7 +22,6 @@
 import java.io.IOException;
 import java.net.URI;
 import java.net.URL;
-import java.security.PrivilegedAction;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
@@ -269,17 +268,11 @@ private void doCheckpoint() throws InterruptedException, IOException {
       boolean shouldUpload = receiverEntry.isPrimary() ||
           secsSinceLastUpload >= checkpointConf.getQuietPeriod();
       if (shouldUpload) {
-        Future<TransferFsImage.TransferResult> upload =
-            executor.submit(new Callable<TransferFsImage.TransferResult>() {
-              @Override
-              public TransferFsImage.TransferResult call()
-                  throws IOException, InterruptedException {
-                CheckpointFaultInjector.getInstance().duringUploadInProgess();
-                return TransferFsImage.uploadImageFromStorage(activeNNAddress,
-                    conf, namesystem.getFSImage().getStorage(), imageType, txid,
-                    canceler);
-              }
-            });
+        Future<TransferFsImage.TransferResult> upload = executor.submit(() -> {
+          CheckpointFaultInjector.getInstance().duringUploadInProgess();
+          return TransferFsImage.uploadImageFromStorage(activeNNAddress, conf,
+              namesystem.getFSImage().getStorage(), imageType, txid, canceler);
+        });
         uploads.put(addressString, upload);
       }
     }
@@ -397,14 +390,10 @@ private void setShouldRun(boolean shouldRun) {
     public void run() {
       // We have to make sure we're logged in as far as JAAS
       // is concerned, in order to use kerberized SSL properly.
-      SecurityUtil.doAsLoginUserOrFatal(
-          new PrivilegedAction<Object>() {
-          @Override
-          public Object run() {
-            doWork();
-            return null;
-          }
-        });
+      SecurityUtil.doAsLoginUserOrFatal(() -> {
+        doWork();
+        return null;
+      });
     }
 
     /**

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/DirectoryDiffListFactory.java

@@ -35,17 +35,17 @@ public static void init(int interval, int maxSkipLevels, Logger log) {
     DirectoryDiffListFactory.maxLevels = maxSkipLevels;
 
     if (maxLevels > 0) {
-      constructor = c -> new DiffListBySkipList(c);
+      constructor = DiffListBySkipList::new;
       log.info("SkipList is enabled with skipInterval=" + skipInterval
           + ", maxLevels=" + maxLevels);
     } else {
-      constructor = c -> new DiffListByArrayList<>(c);
+      constructor = DiffListByArrayList::new;
       log.info("SkipList is disabled");
     }
   }
 
-  private static volatile IntFunction<DiffList<DirectoryDiff>> constructor
-      = c -> new DiffListByArrayList<>(c);
+  private static volatile IntFunction<DiffList<DirectoryDiff>> constructor =
+      DiffListByArrayList::new;
 
   private static volatile int skipInterval;
   private static volatile int maxLevels;

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/DirectorySnapshottableFeature.java

@@ -601,43 +601,37 @@ public void dumpTreeRecursively(INodeDirectory snapshotRoot, PrintWriter out,
       out.print(", #snapshot=");
       out.println(n);
 
-      INodeDirectory.dumpTreeRecursively(out, prefix,
-          new Iterable<SnapshotAndINode>() {
-        @Override
-        public Iterator<SnapshotAndINode> iterator() {
-          return new Iterator<SnapshotAndINode>() {
-            final Iterator<DirectoryDiff> i = getDiffs().iterator();
-            private DirectoryDiff next = findNext();
-
-            private DirectoryDiff findNext() {
-              for(; i.hasNext(); ) {
-                final DirectoryDiff diff = i.next();
-                if (diff.isSnapshotRoot()) {
-                  return diff;
-                }
-              }
-              return null;
+      INodeDirectory.dumpTreeRecursively(out, prefix, () -> new Iterator<SnapshotAndINode>() {
+        final private Iterator<DirectoryDiff> diffIterator = getDiffs().iterator();
+        private DirectoryDiff next = findNext();
+
+        private DirectoryDiff findNext() {
+          while (diffIterator.hasNext()) {
+            final DirectoryDiff diff = diffIterator.next();
+            if (diff.isSnapshotRoot()) {
+              return diff;
             }
+          }
+          return null;
+        }
 
-            @Override
-            public boolean hasNext() {
-              return next != null;
-            }
+        @Override
+        public boolean hasNext() {
+          return next != null;
+        }
 
-            @Override
-            public SnapshotAndINode next() {
-              final SnapshotAndINode pair = new SnapshotAndINode(next
-                  .getSnapshotId(), getSnapshotById(next.getSnapshotId())
-                  .getRoot());
-              next = findNext();
-              return pair;
-            }
+        @Override
+        public SnapshotAndINode next() {
+          final SnapshotAndINode pair = new SnapshotAndINode(next
+              .getSnapshotId(), getSnapshotById(next.getSnapshotId())
+              .getRoot());
+          next = findNext();
+          return pair;
+        }
 
-            @Override
-            public void remove() {
-              throw new UnsupportedOperationException();
-            }
-          };
+        @Override
+        public void remove() {
+          throw new UnsupportedOperationException();
         }
       });
     }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/FSImageFormatPBSnapshot.java

@@ -28,8 +28,6 @@
 import java.io.OutputStream;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
-import java.util.Comparator;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
@@ -320,12 +318,7 @@ private List<INode> loadDeletedList(final List<INodeReference> refList,
         addToDeletedList(deletedRef, dir);
       }
 
-      Collections.sort(dlist, new Comparator<INode>() {
-        @Override
-        public int compare(INode n1, INode n2) {
-          return n1.compareTo(n2.getLocalNameBytes());
-        }
-      });
+      dlist.sort((n1, n2) -> n1.compareTo(n2.getLocalNameBytes()));
       return dlist;
     }
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/Snapshot.java

@@ -111,15 +111,8 @@ public int compare(Snapshot left, Snapshot right) {
    * Compare snapshot with IDs, where null indicates the current status thus
    * is greater than any non-null ID.
    */
-  public static final Comparator<Integer> ID_INTEGER_COMPARATOR
-      = new Comparator<Integer>() {
-    @Override
-    public int compare(Integer left, Integer right) {
-      // Snapshot.CURRENT_STATE_ID means the current state, thus should be the 
-      // largest
-      return left - right;
-    }
-  };
+  public static final Comparator<Integer> ID_INTEGER_COMPARATOR =
+      Comparator.comparingInt(left -> left);
 
   /**
    * Find the latest snapshot that 1) covers the given inode (which means the

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/startupprogress/StartupProgress.java

@@ -153,18 +153,10 @@ public Status getStatus(Phase phase) {
   public Counter getCounter(Phase phase, Step step) {
     if (!isComplete(phase)) {
       final StepTracking tracking = lazyInitStep(phase, step);
-      return new Counter() {
-        @Override
-        public void increment() {
-          tracking.count.incrementAndGet();
-        }
-      };
+      return () -> tracking.count.incrementAndGet();
     } else {
-      return new Counter() {
-        @Override
-        public void increment() {
-          // no-op, because startup has completed
-        }
+      return () -> {
+        // no-op, because startup has completed
       };
     }
   }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/top/window/RollingWindowManager.java

@@ -201,7 +201,7 @@ public boolean add(User user) {
 
     @Override
     public boolean addAll(Collection<? extends User> users) {
-      users.forEach(user -> add(user));
+      users.forEach(this::add);
       return true;
     }