diff --git a/tajo-catalog/tajo-catalog-drivers/tajo-hive/src/main/java/org/apache/tajo/catalog/store/HiveCatalogStoreClientPool.java b/tajo-catalog/tajo-catalog-drivers/tajo-hive/src/main/java/org/apache/tajo/catalog/store/HiveCatalogStoreClientPool.java
index 8be3a73448..7180694270 100644
--- a/tajo-catalog/tajo-catalog-drivers/tajo-hive/src/main/java/org/apache/tajo/catalog/store/HiveCatalogStoreClientPool.java
+++ b/tajo-catalog/tajo-catalog-drivers/tajo-hive/src/main/java/org/apache/tajo/catalog/store/HiveCatalogStoreClientPool.java
@@ -48,14 +48,11 @@ public class HiveCatalogStoreClient {
 
     private HiveCatalogStoreClient(HiveConf hiveConf) {
       try {
-        HiveMetaHookLoader hookLoader = new HiveMetaHookLoader() {
-          @Override
-          public HiveMetaHook getHook(Table table) throws MetaException {
-            /* metadata hook implementation, or null if this
-             * storage handler does not need any metadata notifications
-             */
-            return null;
-          }
+        HiveMetaHookLoader hookLoader = table -> {
+          /* metadata hook implementation, or null if this
+           * storage handler does not need any metadata notifications
+           */
+          return null;
         };
 
         this.hiveClient = RetryingMetaStoreClient.getProxy(hiveConf, hookLoader, HiveMetaStoreClient.class.getName());
diff --git a/tajo-catalog/tajo-catalog-server/src/main/java/org/apache/tajo/catalog/CatalogServer.java b/tajo-catalog/tajo-catalog-server/src/main/java/org/apache/tajo/catalog/CatalogServer.java
index 6583d4eb01..d413ddf5ca 100644
--- a/tajo-catalog/tajo-catalog-server/src/main/java/org/apache/tajo/catalog/CatalogServer.java
+++ b/tajo-catalog/tajo-catalog-server/src/main/java/org/apache/tajo/catalog/CatalogServer.java
@@ -299,15 +299,10 @@ public GetTablespaceListResponse getAllTablespaces(RpcController controller, Nul
 
         // retrieves tablespaces from linked meta data
         tableSpaces.addAll(Collections2.transform(linkedMetadataManager.getTablespaces(),
-            new Function<Pair<String, URI>, TablespaceProto>() {
-              @Override
-              public TablespaceProto apply(Pair<String, URI> input) {
-                return TablespaceProto.newBuilder()
-                    .setSpaceName(input.getFirst())
-                    .setUri(input.getSecond().toString())
-                    .build();
-              }
-            }));
+          input -> TablespaceProto.newBuilder()
+              .setSpaceName(input.getFirst())
+              .setUri(input.getSecond().toString())
+              .build()));
 
         return GetTablespaceListResponse.newBuilder()
             .setState(OK)
diff --git a/tajo-catalog/tajo-catalog-server/src/main/java/org/apache/tajo/catalog/LinkedMetadataManager.java b/tajo-catalog/tajo-catalog-server/src/main/java/org/apache/tajo/catalog/LinkedMetadataManager.java
index 1ffe550fab..759c001d54 100644
--- a/tajo-catalog/tajo-catalog-server/src/main/java/org/apache/tajo/catalog/LinkedMetadataManager.java
+++ b/tajo-catalog/tajo-catalog-server/src/main/java/org/apache/tajo/catalog/LinkedMetadataManager.java
@@ -77,12 +77,7 @@ public Collection<String> getTablespaceNames() {
    */
   public Optional<Pair<String, URI>> getTablespace(final String spaceName) {
     Collection<MetadataProvider> filtered = filter(providerMap.values(),
-        new Predicate<MetadataProvider>() {
-          @Override
-          public boolean apply(@Nullable MetadataProvider input) {
-            return input.getTablespaceName().equals(spaceName);
-          }
-        });
+      input -> input.getTablespaceName().equals(spaceName));
 
     if (filtered.isEmpty()) {
       return Optional.empty();
diff --git a/tajo-catalog/tajo-catalog-server/src/main/java/org/apache/tajo/catalog/store/XMLCatalogSchemaManager.java b/tajo-catalog/tajo-catalog-server/src/main/java/org/apache/tajo/catalog/store/XMLCatalogSchemaManager.java
index ea15c079ea..1f0c6393d5 100644
--- a/tajo-catalog/tajo-catalog-server/src/main/java/org/apache/tajo/catalog/store/XMLCatalogSchemaManager.java
+++ b/tajo-catalog/tajo-catalog-server/src/main/java/org/apache/tajo/catalog/store/XMLCatalogSchemaManager.java
@@ -447,14 +447,8 @@ protected String[] listJarResources(URL dirURL, FilenameFilter filter)
   protected String[] listResources() throws IOException, URISyntaxException {
     String[] files = new String[0];
     URL dirURL = ClassLoader.getSystemResource(schemaPath);
-    FilenameFilter fileFilter = new FilenameFilter() {
-      
-      @Override
-      public boolean accept(File dir, String name) {
-        return ((name.lastIndexOf('.') > -1) && 
-            (".xml".equalsIgnoreCase(name.substring(name.lastIndexOf('.')))));
-      }
-    };
+    FilenameFilter fileFilter = (dir, name) -> ((name.lastIndexOf('.') > -1) &&
+        (".xml".equalsIgnoreCase(name.substring(name.lastIndexOf('.')))));
     
     if (dirURL == null) {
       throw new FileNotFoundException(schemaPath);
diff --git a/tajo-catalog/tajo-catalog-server/src/test/java/org/apache/tajo/catalog/TestLinkedMetadataManager.java b/tajo-catalog/tajo-catalog-server/src/test/java/org/apache/tajo/catalog/TestLinkedMetadataManager.java
index dece380ea8..53e0afa82f 100644
--- a/tajo-catalog/tajo-catalog-server/src/test/java/org/apache/tajo/catalog/TestLinkedMetadataManager.java
+++ b/tajo-catalog/tajo-catalog-server/src/test/java/org/apache/tajo/catalog/TestLinkedMetadataManager.java
@@ -177,12 +177,7 @@ public void testGetTablespace() throws Exception {
   @Test
   public void testGetTablespaces() throws Exception {
     Collection<String> names = Collections2.transform(catalog.getAllTablespaces(),
-        new Function<CatalogProtos.TablespaceProto, String>() {
-      @Override
-      public String apply(@Nullable CatalogProtos.TablespaceProto input) {
-        return input.getSpaceName();
-      }
-    });
+      input -> input.getSpaceName());
 
     assertEquals(Sets.newHashSet("space1", "space2", "default"), Sets.newHashSet(names));
   }
diff --git a/tajo-cli/src/main/java/org/apache/tajo/cli/tsql/TajoCli.java b/tajo-cli/src/main/java/org/apache/tajo/cli/tsql/TajoCli.java
index e6e8410ccf..6bf6ee1cd1 100644
--- a/tajo-cli/src/main/java/org/apache/tajo/cli/tsql/TajoCli.java
+++ b/tajo-cli/src/main/java/org/apache/tajo/cli/tsql/TajoCli.java
@@ -440,15 +440,12 @@ private Collection<String> getKeywords() {
   }
 
   private void addShutdownHook() {
-    ShutdownHookManager.get().addShutdownHook(new Runnable() {
-      @Override
-      public void run() {
-        try {
-          history.flush();
-        } catch (IOException e) {
-        }
-        client.close();
+    ShutdownHookManager.get().addShutdownHook(() -> {
+      try {
+        history.flush();
+      } catch (IOException e) {
       }
+      client.close();
     }, SHUTDOWN_HOOK_PRIORITY);
   }
 
diff --git a/tajo-cluster-tests/src/test/java/org/apache/tajo/QueryTestCaseBase.java b/tajo-cluster-tests/src/test/java/org/apache/tajo/QueryTestCaseBase.java
index 315f954e0a..77e6feb683 100644
--- a/tajo-cluster-tests/src/test/java/org/apache/tajo/QueryTestCaseBase.java
+++ b/tajo-cluster-tests/src/test/java/org/apache/tajo/QueryTestCaseBase.java
@@ -902,12 +902,7 @@ private Collection<Path> getPositiveQueryFiles() throws IOException {
       throw new IOException("Cannot find " + positiveQueryDir);
     }
 
-    return Collections2.transform(Lists.newArrayList(fs.listStatus(positiveQueryDir)), new Function<FileStatus, Path>(){
-      @Override
-      public Path apply(@Nullable FileStatus fileStatus) {
-        return fileStatus.getPath();
-      }
-    });
+    return Collections2.transform(Lists.newArrayList(fs.listStatus(positiveQueryDir)), fileStatus -> fileStatus.getPath());
   }
 
   private Collection<Path> getNegativeQueryFiles() throws IOException {
@@ -918,12 +913,7 @@ private Collection<Path> getNegativeQueryFiles() throws IOException {
       throw new IOException("Cannot find " + positiveQueryDir);
     }
 
-    return Collections2.transform(Lists.newArrayList(fs.listStatus(positiveQueryDir)),new Function<FileStatus, Path>(){
-      @Override
-      public Path apply(@Nullable FileStatus fileStatus) {
-        return fileStatus.getPath();
-      }
-    });
+    return Collections2.transform(Lists.newArrayList(fs.listStatus(positiveQueryDir)), fileStatus -> fileStatus.getPath());
   }
 
   private Path getQueryFilePath(String fileName) throws IOException {
diff --git a/tajo-core-tests/src/test/java/org/apache/tajo/client/TestTajoClient.java b/tajo-core-tests/src/test/java/org/apache/tajo/client/TestTajoClient.java
index 828f60c7b7..a39b990f62 100644
--- a/tajo-core-tests/src/test/java/org/apache/tajo/client/TestTajoClient.java
+++ b/tajo-core-tests/src/test/java/org/apache/tajo/client/TestTajoClient.java
@@ -770,12 +770,7 @@ public void testGetQueryInfoAndHistory() throws Exception {
 
     List<ClientProtos.StageHistoryProto> taskHistories =
             new ArrayList<>(queryHistory.getStageHistoriesList());
-    Collections.sort(taskHistories, new Comparator<StageHistoryProto>() {
-      @Override
-      public int compare(ClientProtos.StageHistoryProto o1, StageHistoryProto o2) {
-        return o1.getExecutionBlockId().compareTo(o2.getExecutionBlockId());
-      }
-    });
+    Collections.sort(taskHistories, (o1, o2) -> o1.getExecutionBlockId().compareTo(o2.getExecutionBlockId()));
     assertEquals(8, taskHistories.get(0).getTotalReadRows());
     assertEquals(1, taskHistories.get(0).getTotalWriteRows());
     assertEquals(1, taskHistories.get(1).getTotalReadRows());
diff --git a/tajo-core-tests/src/test/java/org/apache/tajo/client/v2/TestTajoClientV2.java b/tajo-core-tests/src/test/java/org/apache/tajo/client/v2/TestTajoClientV2.java
index f6b4f88e02..1d3385cf8c 100644
--- a/tajo-core-tests/src/test/java/org/apache/tajo/client/v2/TestTajoClientV2.java
+++ b/tajo-core-tests/src/test/java/org/apache/tajo/client/v2/TestTajoClientV2.java
@@ -157,30 +157,27 @@ public void testExecuteQueryAsyncWithListener() throws TajoException, IOExceptio
     final AtomicBoolean success = new AtomicBoolean(false);
     final List<ResultSet> resultContainer = Lists.newArrayList();
 
-    future.addListener(new FutureListener<QueryFuture>() {
-      @Override
-      public void processingCompleted(QueryFuture future) {
-        try {
-          ResultSet result = future.get();
-          resultContainer.add(result); // for better error handling, it should be verified outside this future.
-
-          assertTrue(future.isDone());
-          assertEquals(QueryState.COMPLETED, future.state());
-          assertTrue(future.isSuccessful());
-          assertFalse(future.isFailed());
-          assertFalse(future.isKilled());
-          assertTrue(1.0f == future.progress());
-          assertEquals("default", future.queue());
-
-          assertTrue(future.submitTime() > 0);
-          assertTrue(future.startTime() > 0);
-          assertTrue(future.finishTime() > 0);
-
-          success.set(true);
-
-        } catch (Throwable t) {
-          throw new RuntimeException(t);
-        }
+    future.addListener(queryFuture -> {
+      try {
+        ResultSet result = queryFuture.get();
+        resultContainer.add(result); // for better error handling, it should be verified outside this future.
+
+        assertTrue(queryFuture.isDone());
+        assertEquals(QueryState.COMPLETED, queryFuture.state());
+        assertTrue(queryFuture.isSuccessful());
+        assertFalse(queryFuture.isFailed());
+        assertFalse(queryFuture.isKilled());
+        assertTrue(1.0f == queryFuture.progress());
+        assertEquals("default", queryFuture.queue());
+
+        assertTrue(queryFuture.submitTime() > 0);
+        assertTrue(queryFuture.startTime() > 0);
+        assertTrue(queryFuture.finishTime() > 0);
+
+        success.set(true);
+
+      } catch (Throwable t) {
+        throw new RuntimeException(t);
       }
     });
 
diff --git a/tajo-core-tests/src/test/java/org/apache/tajo/engine/planner/TestLogicalPlanner.java b/tajo-core-tests/src/test/java/org/apache/tajo/engine/planner/TestLogicalPlanner.java
index 142b2c3836..4089bc16a3 100644
--- a/tajo-core-tests/src/test/java/org/apache/tajo/engine/planner/TestLogicalPlanner.java
+++ b/tajo-core-tests/src/test/java/org/apache/tajo/engine/planner/TestLogicalPlanner.java
@@ -1355,12 +1355,7 @@ public void testSelectFromSelfDescTable() throws Exception {
 
     // projection column test
     List<Target> targets = projectionNode.getTargets();
-    Collections.sort(targets, new Comparator<Target>() {
-      @Override
-      public int compare(Target o1, Target o2) {
-        return o1.getCanonicalName().compareTo(o2.getCanonicalName());
-      }
-    });
+    Collections.sort(targets, (o1, o2) -> o1.getCanonicalName().compareTo(o2.getCanonicalName()));
     assertEquals(3, targets.size());
     assertEquals("default.self_desc_table1.dept", targets.get(0).getCanonicalName());
     assertEquals("default.self_desc_table1.id", targets.get(1).getCanonicalName());
@@ -1370,12 +1365,7 @@ public int compare(Target o1, Target o2) {
     assertEquals(NodeType.SCAN, projectionNode.getChild().getType());
     ScanNode scanNode = projectionNode.getChild();
     targets = scanNode.getTargets();
-    Collections.sort(targets, new Comparator<Target>() {
-      @Override
-      public int compare(Target o1, Target o2) {
-        return o1.getCanonicalName().compareTo(o2.getCanonicalName());
-      }
-    });
+    Collections.sort(targets, (o1, o2) -> o1.getCanonicalName().compareTo(o2.getCanonicalName()));
     assertEquals(3, targets.size());
     assertEquals("default.self_desc_table1.dept", targets.get(0).getCanonicalName());
     assertEquals("default.self_desc_table1.id", targets.get(1).getCanonicalName());
@@ -1409,12 +1399,7 @@ public void testSelectWhereFromSelfDescTable() throws Exception {
 
     // projection column test
     List<Target> targets = projectionNode.getTargets();
-    Collections.sort(targets, new Comparator<Target>() {
-      @Override
-      public int compare(Target o1, Target o2) {
-        return o1.getCanonicalName().compareTo(o2.getCanonicalName());
-      }
-    });
+    Collections.sort(targets, (o1, o2) -> o1.getCanonicalName().compareTo(o2.getCanonicalName()));
     assertEquals(2, targets.size());
     assertEquals("default.self_desc_table1.dept", targets.get(0).getCanonicalName());
     assertEquals("default.self_desc_table1.name", targets.get(1).getCanonicalName());
@@ -1428,12 +1413,7 @@ public int compare(Target o1, Target o2) {
     assertEquals(NodeType.SCAN, selectionNode.getChild().getType());
     ScanNode scanNode = selectionNode.getChild();
     targets = scanNode.getTargets();
-    Collections.sort(targets, new Comparator<Target>() {
-      @Override
-      public int compare(Target o1, Target o2) {
-        return o1.getCanonicalName().compareTo(o2.getCanonicalName());
-      }
-    });
+    Collections.sort(targets, (o1, o2) -> o1.getCanonicalName().compareTo(o2.getCanonicalName()));
     assertEquals(4, targets.size());
     assertEquals("?greaterthan", targets.get(0).getCanonicalName());
     assertEquals("default.self_desc_table1.dept", targets.get(1).getCanonicalName());
diff --git a/tajo-core-tests/src/test/java/org/apache/tajo/engine/query/TestJoinQuery.java b/tajo-core-tests/src/test/java/org/apache/tajo/engine/query/TestJoinQuery.java
index 125a2ec677..d33fb7c666 100644
--- a/tajo-core-tests/src/test/java/org/apache/tajo/engine/query/TestJoinQuery.java
+++ b/tajo-core-tests/src/test/java/org/apache/tajo/engine/query/TestJoinQuery.java
@@ -193,16 +193,21 @@ protected static void createCommonTables() throws Exception {
 
     // According to node type(leaf or non-leaf) Broadcast join is determined differently by Repartitioner.
     // testMultipleBroadcastDataFileWithZeroLength testcase is for the leaf node
-    createMultiFile("nation", 2, new TupleCreator() {
-      public Tuple createTuple(String[] columnDatas) {
-        return new VTuple(new Datum[]{
-            columnDatas[0].equals("") ? NullDatum.get() : new Int4Datum(Integer.parseInt(columnDatas[0])),
-            columnDatas[1].equals("") ? NullDatum.get() : new TextDatum(columnDatas[1]),
-            columnDatas[2].equals("") ? NullDatum.get() : new Int4Datum(Integer.parseInt(columnDatas[2])),
-            columnDatas[3].equals("") ? NullDatum.get() : new TextDatum(columnDatas[3])
-        });
-      }
-    });
+//<<<<<<< 1c44272bff0fc0022a1c8ce060b70d11a30c59e0
+    createMultiFile("nation", 2, columnDatas -> new VTuple(new Datum[]{
+      columnDatas[0].equals("") ? NullDatum.get() : new Int4Datum(Integer.parseInt(columnDatas[0])),
+      columnDatas[1].equals("") ? NullDatum.get() : new TextDatum(columnDatas[1]),
+      columnDatas[2].equals("") ? NullDatum.get() : new Int4Datum(Integer.parseInt(columnDatas[2])),
+      columnDatas[3].equals("") ? NullDatum.get() : new TextDatum(columnDatas[3])
+    }));
+//=======
+//    createMultiFile("nation", 2, columnDatas -> new VTuple(new Datum[]{
+//        new Int4Datum(Integer.parseInt(columnDatas[0])),
+//        new TextDatum(columnDatas[1]),
+//        new Int4Datum(Integer.parseInt(columnDatas[2])),
+//        new TextDatum(columnDatas[3])
+//    }));
+//>>>>>>> initial commit
     addEmptyDataFile("nation_multifile", false);
   }
 
diff --git a/tajo-core-tests/src/test/java/org/apache/tajo/engine/util/TestTableCache.java b/tajo-core-tests/src/test/java/org/apache/tajo/engine/util/TestTableCache.java
index 2161074640..650ca12df5 100644
--- a/tajo-core-tests/src/test/java/org/apache/tajo/engine/util/TestTableCache.java
+++ b/tajo-core-tests/src/test/java/org/apache/tajo/engine/util/TestTableCache.java
@@ -67,43 +67,40 @@ public void testBroadcastTableCache() throws Exception {
   }
 
   private Callable<CacheHolder<Long>> createTask(final TableCacheKey key, final ExecutionBlockSharedResource resource) {
-    return new Callable<CacheHolder<Long>>() {
-      @Override
-      public CacheHolder<Long> call() throws Exception {
-        CacheHolder<Long> result;
-        synchronized (resource.getLock()) {
-          if (!TableCache.getInstance().hasCache(key)) {
-            final long nanoTime = System.nanoTime();
-            final TableStats tableStats = new TableStats();
-            tableStats.setNumRows(100);
-            tableStats.setNumBytes(1000);
-
-            final CacheHolder<Long> cacheHolder = new CacheHolder<Long>() {
-
-              @Override
-              public Long getData() {
-                return nanoTime;
-              }
-
-              @Override
-              public TableStats getTableStats() {
-                return tableStats;
-              }
-
-              @Override
-              public void release() {
-
-              }
-            };
-
-            resource.addBroadcastCache(key, cacheHolder);
-          }
+    return () -> {
+      CacheHolder<Long> result;
+      synchronized (resource.getLock()) {
+        if (!TableCache.getInstance().hasCache(key)) {
+          final long nanoTime = System.nanoTime();
+          final TableStats tableStats = new TableStats();
+          tableStats.setNumRows(100);
+          tableStats.setNumBytes(1000);
+
+          final CacheHolder<Long> cacheHolder = new CacheHolder<Long>() {
+
+            @Override
+            public Long getData() {
+              return nanoTime;
+            }
+
+            @Override
+            public TableStats getTableStats() {
+              return tableStats;
+            }
+
+            @Override
+            public void release() {
+
+            }
+          };
+
+          resource.addBroadcastCache(key, cacheHolder);
         }
-
-        CacheHolder<?> holder = resource.getBroadcastCache(key);
-        result = (CacheHolder<Long>) holder;
-        return result;
       }
+
+      CacheHolder<?> holder = resource.getBroadcastCache(key);
+      result = (CacheHolder<Long>) holder;
+      return result;
     };
   }
 }
diff --git a/tajo-core-tests/src/test/java/org/apache/tajo/master/scheduler/TestSimpleScheduler.java b/tajo-core-tests/src/test/java/org/apache/tajo/master/scheduler/TestSimpleScheduler.java
index 41ebd67a2e..d36196ed68 100644
--- a/tajo-core-tests/src/test/java/org/apache/tajo/master/scheduler/TestSimpleScheduler.java
+++ b/tajo-core-tests/src/test/java/org/apache/tajo/master/scheduler/TestSimpleScheduler.java
@@ -267,13 +267,10 @@ public QueryContext getQueryContext() {
 
     @Override
     protected boolean startQuery(final QueryId queryId, final AllocationResourceProto allocation) {
-      executorService.schedule(new Runnable() {
-        @Override
-        public void run() {
-          barrier.release();
-          qmAllocationMap.put(queryId, allocation);
-          rmContext.getDispatcher().getEventHandler().handle(new SchedulerEvent(SchedulerEventType.RESOURCE_UPDATE));
-        }
+      executorService.schedule((Runnable) () -> {
+        barrier.release();
+        qmAllocationMap.put(queryId, allocation);
+        rmContext.getDispatcher().getEventHandler().handle(new SchedulerEvent(SchedulerEventType.RESOURCE_UPDATE));
       }, testDelay, TimeUnit.MILLISECONDS);
       return true;
     }
diff --git a/tajo-core-tests/src/test/java/org/apache/tajo/parser/sql/TestSQLAnalyzer.java b/tajo-core-tests/src/test/java/org/apache/tajo/parser/sql/TestSQLAnalyzer.java
index e2968a8664..5b6a7d1240 100644
--- a/tajo-core-tests/src/test/java/org/apache/tajo/parser/sql/TestSQLAnalyzer.java
+++ b/tajo-core-tests/src/test/java/org/apache/tajo/parser/sql/TestSQLAnalyzer.java
@@ -72,26 +72,18 @@ public Collection<File> getResourceFiles(String subdir) throws URISyntaxExceptio
 
     // get only files
     Collection<FileStatus> files = filter(Lists.newArrayList(fs.listStatus(positiveQueryDir)),
-        new Predicate<FileStatus>() {
-          @Override
-          public boolean apply(@Nullable FileStatus input) {
-            // TODO: This should be removed at TAJO-1891
-            if (input.getPath().getName().indexOf("add_partition") > -1) {
-              return false;
-            } else {
-              return input.isFile();
-            }
-          }
+      input -> {
+        // TODO: This should be removed at TAJO-1891
+        if (input.getPath().getName().indexOf("add_partition") > -1) {
+          return false;
+        } else {
+          return input.isFile();
         }
+      }
     );
 
     // transform FileStatus into File
-    return transform(files, new Function<FileStatus, File>() {
-      @Override
-      public File apply(@Nullable FileStatus fileStatus) {
-        return new File(URI.create(fileStatus.getPath().toString()));
-      }
-    });
+    return transform(files, fileStatus -> new File(URI.create(fileStatus.getPath().toString())));
   }
 
   /**
@@ -102,14 +94,11 @@ public File apply(@Nullable FileStatus fileStatus) {
    * @throws URISyntaxException
    */
   public Collection<Pair<String, String>> getFileContents(String subdir) throws IOException, URISyntaxException {
-    return transform(getResourceFiles(subdir), new Function<File, Pair<String, String>>() {
-      @Override
-      public Pair<String, String> apply(@Nullable File file) {
-        try {
-          return new Pair<>(file.getName(), FileUtil.readTextFile(file));
-        } catch (IOException e) {
-          throw new RuntimeException(e);
-        }
+    return transform(getResourceFiles(subdir), file -> {
+      try {
+        return new Pair<>(file.getName(), FileUtil.readTextFile(file));
+      } catch (IOException e) {
+        throw new RuntimeException(e);
       }
     });
   }
diff --git a/tajo-core-tests/src/test/java/org/apache/tajo/querymaster/TestTaskStatusUpdate.java b/tajo-core-tests/src/test/java/org/apache/tajo/querymaster/TestTaskStatusUpdate.java
index baae7edb82..ccbf3ff90a 100644
--- a/tajo-core-tests/src/test/java/org/apache/tajo/querymaster/TestTaskStatusUpdate.java
+++ b/tajo-core-tests/src/test/java/org/apache/tajo/querymaster/TestTaskStatusUpdate.java
@@ -147,12 +147,7 @@ private void assertStatus(QueryId queryId, int numStages,
     List<StageHistory> stages = queryHistory.getStageHistories();
     assertEquals(numStages, stages.size());
 
-    Collections.sort(stages, new Comparator<StageHistory>() {
-      @Override
-      public int compare(StageHistory o1, StageHistory o2) {
-        return o1.getExecutionBlockId().compareTo(o2.getExecutionBlockId());
-      }
-    });
+    Collections.sort(stages, (o1, o2) -> o1.getExecutionBlockId().compareTo(o2.getExecutionBlockId()));
 
     int index = 0;
     StringBuilder expectedString = new StringBuilder();
diff --git a/tajo-core-tests/src/test/java/org/apache/tajo/worker/TestNodeResourceManager.java b/tajo-core-tests/src/test/java/org/apache/tajo/worker/TestNodeResourceManager.java
index 3901cdb6f6..41683c6899 100644
--- a/tajo-core-tests/src/test/java/org/apache/tajo/worker/TestNodeResourceManager.java
+++ b/tajo-core-tests/src/test/java/org/apache/tajo/worker/TestNodeResourceManager.java
@@ -252,36 +252,33 @@ public void testParallelRequest() throws Exception {
     List<Future> futureList = Lists.newArrayList();
 
     for (int i = 0; i < parallelCount; i++) {
-      futureList.add(executor.submit(new Runnable() {
-            @Override
-            public void run() {
-              int complete = 0;
-              while (true) {
-                TaskAllocationProto task = totalTasks.poll();
-                if (task == null) break;
-
-
-                BatchAllocationRequest.Builder requestProto = BatchAllocationRequest.newBuilder();
-                requestProto.addTaskRequest(task);
-                requestProto.setExecutionBlockId(ebId.getProto());
-
-                CallFuture<BatchAllocationResponse> callFuture = new CallFuture<>();
-                dispatcher.getEventHandler().handle(new NodeResourceAllocateEvent(requestProto.build(), callFuture));
-                try {
-                  BatchAllocationResponse proto = callFuture.get();
-                  if (proto.getCancellationTaskCount() > 0) {
-                    totalTasks.addAll(proto.getCancellationTaskList());
-                    totalCanceled.addAndGet(proto.getCancellationTaskCount());
-                  } else {
-                    complete++;
-                  }
-                } catch (Exception e) {
-                  fail(e.getMessage());
-                }
-              }
-              totalComplete.addAndGet(complete);
+      futureList.add(executor.submit((Runnable) () -> {
+        int complete = 0;
+        while (true) {
+          TaskAllocationProto task1 = totalTasks.poll();
+          if (task1 == null) break;
+
+
+          BatchAllocationRequest.Builder requestProto1 = BatchAllocationRequest.newBuilder();
+          requestProto1.addTaskRequest(task1);
+          requestProto1.setExecutionBlockId(ebId.getProto());
+
+          CallFuture<BatchAllocationResponse> callFuture1 = new CallFuture<>();
+          dispatcher.getEventHandler().handle(new NodeResourceAllocateEvent(requestProto1.build(), callFuture1));
+          try {
+            BatchAllocationResponse proto = callFuture1.get();
+            if (proto.getCancellationTaskCount() > 0) {
+              totalTasks.addAll(proto.getCancellationTaskList());
+              totalCanceled.addAndGet(proto.getCancellationTaskCount());
+            } else {
+              complete++;
             }
-          })
+          } catch (Exception e) {
+            fail(e.getMessage());
+          }
+        }
+        totalComplete.addAndGet(complete);
+      })
       );
     }
 
diff --git a/tajo-core/src/main/java/org/apache/tajo/engine/planner/physical/CommonJoinExec.java b/tajo-core/src/main/java/org/apache/tajo/engine/planner/physical/CommonJoinExec.java
index 96ed0a6e74..6c4778d8dc 100644
--- a/tajo-core/src/main/java/org/apache/tajo/engine/planner/physical/CommonJoinExec.java
+++ b/tajo-core/src/main/java/org/apache/tajo/engine/planner/physical/CommonJoinExec.java
@@ -172,11 +172,8 @@ protected Iterator<Tuple> rightFiltered(Iterable<Tuple> rightTuples) {
     if (rightJoinFilter == null) {
       return rightTuples.iterator();
     }
-    return Iterators.filter(rightTuples.iterator(), new Predicate<Tuple>() {
-      @Override
-      public boolean apply(Tuple input) {
-        return rightJoinFilter.eval(input).isTrue();
-      }
+    return Iterators.filter(rightTuples.iterator(), input -> {
+      return rightJoinFilter.eval(input).isTrue();
     });
   }
 
diff --git a/tajo-core/src/main/java/org/apache/tajo/engine/planner/physical/VectorizedSorter.java b/tajo-core/src/main/java/org/apache/tajo/engine/planner/physical/VectorizedSorter.java
index 44649cd100..08c8509c54 100644
--- a/tajo-core/src/main/java/org/apache/tajo/engine/planner/physical/VectorizedSorter.java
+++ b/tajo-core/src/main/java/org/apache/tajo/engine/planner/physical/VectorizedSorter.java
@@ -63,16 +63,11 @@ public void swap(int i1, int i2) {
   @Override
   public Iterable<Tuple> sort() {
     new QuickSort().sort(this, 0, mappings.length);
-    return new Iterable<Tuple>() {
-      @Override
-      public Iterator<Tuple> iterator() {
-        return new Iterator<Tuple>() {
-          int index;
-          public boolean hasNext() { return index < mappings.length; }
-          public Tuple next() { return tuples[mappings[index++]]; }
-          public void remove() { throw new TajoRuntimeException(new UnsupportedException()); }
-        };
-      }
+    return () -> new Iterator<Tuple>() {
+      int index;
+      public boolean hasNext() { return index < mappings.length; }
+      public Tuple next() { return tuples[mappings[index++]]; }
+      public void remove() { throw new TajoRuntimeException(new UnsupportedException()); }
     };
   }
 }
diff --git a/tajo-core/src/main/java/org/apache/tajo/master/GlobalEngine.java b/tajo-core/src/main/java/org/apache/tajo/master/GlobalEngine.java
index c088a8b4c6..b6642a4f60 100644
--- a/tajo-core/src/main/java/org/apache/tajo/master/GlobalEngine.java
+++ b/tajo-core/src/main/java/org/apache/tajo/master/GlobalEngine.java
@@ -154,11 +154,7 @@ private QueryContext createQueryContext(Session session) {
     // Set queryCache in session
     int queryCacheSize = context.getConf().getIntVar(TajoConf.ConfVars.QUERY_SESSION_QUERY_CACHE_SIZE);
     if (queryCacheSize > 0 && session.getQueryCache() == null) {
-      Weigher<String, Expr> weighByLength = new Weigher<String, Expr>() {
-        public int weigh(String key, Expr expr) {
-          return key.length();
-        }
-      };
+      Weigher<String, Expr> weighByLength = (key, expr) -> key.length();
       LoadingCache<String, Expr> cache = CacheBuilder.newBuilder()
         .maximumWeight(queryCacheSize * 1024)
         .weigher(weighByLength)
diff --git a/tajo-core/src/main/java/org/apache/tajo/metrics/ClusterResourceMetricSet.java b/tajo-core/src/main/java/org/apache/tajo/metrics/ClusterResourceMetricSet.java
index 1798f22e88..a7d8878be0 100644
--- a/tajo-core/src/main/java/org/apache/tajo/metrics/ClusterResourceMetricSet.java
+++ b/tajo-core/src/main/java/org/apache/tajo/metrics/ClusterResourceMetricSet.java
@@ -39,54 +39,19 @@ public ClusterResourceMetricSet(TajoMaster.MasterContext masterContext) {
   public Map<String, Metric> getMetrics() {
     Map<String, Metric> metricsMap = new HashMap<>();
 
-    metricsMap.put(Cluster.TOTAL_NODES.name(), new Gauge<Integer>() {
-      @Override
-      public Integer getValue() {
-        return masterContext.getResourceManager().getNodes().size();
-      }
-    });
+    metricsMap.put(Cluster.TOTAL_NODES.name(), (Gauge<Integer>) () -> masterContext.getResourceManager().getNodes().size());
 
-    metricsMap.put(Cluster.ACTIVE_NODES.name(), new Gauge<Integer>() {
-      @Override
-      public Integer getValue() {
-        return getNumWorkers(NodeState.RUNNING);
-      }
-    });
+    metricsMap.put(Cluster.ACTIVE_NODES.name(), (Gauge<Integer>) () -> getNumWorkers(NodeState.RUNNING));
 
-    metricsMap.put(Cluster.LOST_NODES.name(), new Gauge<Integer>() {
-      @Override
-      public Integer getValue() {
-        return getNumWorkers(NodeState.LOST);
-      }
-    });
+    metricsMap.put(Cluster.LOST_NODES.name(), (Gauge<Integer>) () -> getNumWorkers(NodeState.LOST));
 
-    metricsMap.put(Cluster.TOTAL_MEMORY.name(), new Gauge<Integer>() {
-      @Override
-      public Integer getValue() {
-        return masterContext.getResourceManager().getScheduler().getMaximumResourceCapability().getMemory();
-      }
-    });
+    metricsMap.put(Cluster.TOTAL_MEMORY.name(), (Gauge<Integer>) () -> masterContext.getResourceManager().getScheduler().getMaximumResourceCapability().getMemory());
 
-    metricsMap.put(Cluster.FREE_MEMORY.name(), new Gauge<Integer>() {
-      @Override
-      public Integer getValue() {
-        return masterContext.getResourceManager().getScheduler().getClusterResource().getMemory();
-      }
-    });
+    metricsMap.put(Cluster.FREE_MEMORY.name(), (Gauge<Integer>) () -> masterContext.getResourceManager().getScheduler().getClusterResource().getMemory());
 
-    metricsMap.put(Cluster.TOTAL_VCPU.name(), new Gauge<Integer>() {
-      @Override
-      public Integer getValue() {
-        return masterContext.getResourceManager().getScheduler().getMaximumResourceCapability().getVirtualCores();
-      }
-    });
+    metricsMap.put(Cluster.TOTAL_VCPU.name(), (Gauge<Integer>) () -> masterContext.getResourceManager().getScheduler().getMaximumResourceCapability().getVirtualCores());
 
-    metricsMap.put(Cluster.FREE_VCPU.name(), new Gauge<Integer>() {
-      @Override
-      public Integer getValue() {
-        return masterContext.getResourceManager().getScheduler().getClusterResource().getVirtualCores();
-      }
-    });
+    metricsMap.put(Cluster.FREE_VCPU.name(), (Gauge<Integer>) () -> masterContext.getResourceManager().getScheduler().getClusterResource().getVirtualCores());
 
     return metricsMap;
   }
diff --git a/tajo-core/src/main/java/org/apache/tajo/parser/sql/SQLAnalyzer.java b/tajo-core/src/main/java/org/apache/tajo/parser/sql/SQLAnalyzer.java
index 6ffe65b059..bac9272e7b 100644
--- a/tajo-core/src/main/java/org/apache/tajo/parser/sql/SQLAnalyzer.java
+++ b/tajo-core/src/main/java/org/apache/tajo/parser/sql/SQLAnalyzer.java
@@ -2035,11 +2035,6 @@ private static String buildIdentifier(IdentifierContext identifier) {
   }
 
   private static String buildIdentifierChain(final Collection<IdentifierContext> identifierChains) {
-    return Joiner.on(".").join(Collections2.transform(identifierChains, new Function<IdentifierContext, String>() {
-      @Override
-      public String apply(IdentifierContext identifierContext) {
-        return buildIdentifier(identifierContext);
-      }
-    }));
+    return Joiner.on(".").join(Collections2.transform(identifierChains, identifierContext -> buildIdentifier(identifierContext)));
   }
 }
diff --git a/tajo-core/src/main/java/org/apache/tajo/querymaster/DefaultTaskScheduler.java b/tajo-core/src/main/java/org/apache/tajo/querymaster/DefaultTaskScheduler.java
index 401ba0a3a6..7c81a29dfe 100644
--- a/tajo-core/src/main/java/org/apache/tajo/querymaster/DefaultTaskScheduler.java
+++ b/tajo-core/src/main/java/org/apache/tajo/querymaster/DefaultTaskScheduler.java
@@ -722,17 +722,14 @@ private TaskAttemptId allocateRackTask(String host) {
       if (remainingTasks.size() > 0) {
         synchronized (scheduledRequests) {
           //find largest remaining task of other host in rack
-          Collections.sort(remainingTasks, new Comparator<HostVolumeMapping>() {
-            @Override
-            public int compare(HostVolumeMapping v1, HostVolumeMapping v2) {
-              // descending remaining tasks
-              if (v2.remainTasksNum.get() > v1.remainTasksNum.get()) {
-                return 1;
-              } else if (v2.remainTasksNum.get() == v1.remainTasksNum.get()) {
-                return 0;
-              } else {
-                return -1;
-              }
+          Collections.sort(remainingTasks, (v1, v2) -> {
+            // descending remaining tasks
+            if (v2.remainTasksNum.get() > v1.remainTasksNum.get()) {
+              return 1;
+            } else if (v2.remainTasksNum.get() == v1.remainTasksNum.get()) {
+              return 0;
+            } else {
+              return -1;
             }
           });
         }
diff --git a/tajo-core/src/main/java/org/apache/tajo/querymaster/QueryMasterTask.java b/tajo-core/src/main/java/org/apache/tajo/querymaster/QueryMasterTask.java
index 8eaab3f417..1f05b80b0e 100644
--- a/tajo-core/src/main/java/org/apache/tajo/querymaster/QueryMasterTask.java
+++ b/tajo-core/src/main/java/org/apache/tajo/querymaster/QueryMasterTask.java
@@ -281,12 +281,7 @@ protected void killTaskAttempt(int workerId, TaskAttemptId taskAttemptId) {
   private class LocalTaskEventHandler implements EventHandler<LocalTaskEvent> {
     @Override
     public void handle(final LocalTaskEvent event) {
-      queryMasterContext.getEventExecutor().submit(new Runnable() {
-        @Override
-        public void run() {
-          killTaskAttempt(event.getWorkerId(), event.getTaskAttemptId());
-        }
-      });
+      queryMasterContext.getEventExecutor().submit((Runnable) () -> killTaskAttempt(event.getWorkerId(), event.getTaskAttemptId()));
     }
   }
 
@@ -475,17 +470,14 @@ private void cleanupQuery(final QueryId queryId) {
 
       LOG.info("Cleanup resources of all workers. Query: " + queryId + ", workers: " + workers.size());
       for (final InetSocketAddress worker : workers) {
-        queryMasterContext.getEventExecutor().submit(new Runnable() {
-          @Override
-          public void run() {
-            try {
-              AsyncRpcClient rpc = RpcClientManager.getInstance().getClient(worker, TajoWorkerProtocol.class, true,
-                  rpcParams);
-              TajoWorkerProtocol.TajoWorkerProtocolService tajoWorkerProtocolService = rpc.getStub();
-              tajoWorkerProtocolService.stopQuery(null, queryId.getProto(), NullCallback.get());
-            } catch (Throwable e) {
-              LOG.error(e.getMessage(), e);
-            }
+        queryMasterContext.getEventExecutor().submit((Runnable) () -> {
+          try {
+            AsyncRpcClient rpc = RpcClientManager.getInstance().getClient(worker, TajoWorkerProtocol.class, true,
+                rpcParams);
+            TajoWorkerProtocol.TajoWorkerProtocolService tajoWorkerProtocolService = rpc.getStub();
+            tajoWorkerProtocolService.stopQuery(null, queryId.getProto(), NullCallback.get());
+          } catch (Throwable e) {
+            LOG.error(e.getMessage(), e);
           }
         });
       }
diff --git a/tajo-core/src/main/java/org/apache/tajo/querymaster/Stage.java b/tajo-core/src/main/java/org/apache/tajo/querymaster/Stage.java
index c055d119e4..be5445f16f 100644
--- a/tajo-core/src/main/java/org/apache/tajo/querymaster/Stage.java
+++ b/tajo-core/src/main/java/org/apache/tajo/querymaster/Stage.java
@@ -734,18 +734,15 @@ protected Map<Integer, InetSocketAddress> getAssignedWorkerMap() {
   private void sendStopExecutionBlockEvent(final StopExecutionBlockRequest requestProto) {
 
     for (final InetSocketAddress worker : getAssignedWorkerMap().values()) {
-      getContext().getQueryMasterContext().getEventExecutor().submit(new Runnable() {
-        @Override
-        public void run() {
-          try {
-            AsyncRpcClient tajoWorkerRpc =
-                RpcClientManager.getInstance().getClient(worker, TajoWorkerProtocol.class, true, rpcParams);
-            TajoWorkerProtocol.TajoWorkerProtocolService tajoWorkerRpcClient = tajoWorkerRpc.getStub();
-            tajoWorkerRpcClient.stopExecutionBlock(null,
-                requestProto, NullCallback.get(PrimitiveProtos.BoolProto.class));
-          } catch (Throwable e) {
-            LOG.error(e.getMessage(), e);
-          }
+      getContext().getQueryMasterContext().getEventExecutor().submit((Runnable) () -> {
+        try {
+          AsyncRpcClient tajoWorkerRpc =
+              RpcClientManager.getInstance().getClient(worker, TajoWorkerProtocol.class, true, rpcParams);
+          TajoWorkerProtocol.TajoWorkerProtocolService tajoWorkerRpcClient = tajoWorkerRpc.getStub();
+          tajoWorkerRpcClient.stopExecutionBlock(null,
+              requestProto, NullCallback.get(PrimitiveProtos.BoolProto.class));
+        } catch (Throwable e) {
+          LOG.error(e.getMessage(), e);
         }
       });
     }
@@ -859,42 +856,37 @@ public StageState transition(final Stage stage, StageEvent stageEvent) {
           // TODO: verify changed shuffle plan
           initTaskScheduler(stage);
           // execute pre-processing asyncronously
-          stage.getContext().getQueryMasterContext().getSingleEventExecutor()
-              .submit(new Runnable() {
-                        @Override
-                        public void run() {
-                          try {
-                            schedule(stage);
-                            stage.totalScheduledObjectsCount = stage.getTaskScheduler().remainingScheduledObjectNum();
-                            LOG.info(stage.totalScheduledObjectsCount + " objects are scheduled");
-
-                            if (stage.getTaskScheduler().remainingScheduledObjectNum() == 0) { // if there is no tasks
-                              stage.eventHandler.handle(
-                                  new StageEvent(stage.getId(), StageEventType.SQ_STAGE_COMPLETED));
-                            } else {
-                              if(stage.getSynchronizedState() == StageState.INITED) {
-                                stage.eventHandler.handle(new StageEvent(stage.getId(), StageEventType.SQ_START));
-                                stage.taskScheduler.start();
-                              } else {
-                                /* all tasks are killed before stage are inited */
-                                if (stage.getTotalScheduledObjectsCount() == stage.getCompletedTaskCount()) {
-                                  stage.eventHandler.handle(
-                                      new StageEvent(stage.getId(), StageEventType.SQ_STAGE_COMPLETED));
-                                } else {
-                                  stage.eventHandler.handle(
-                                      new StageEvent(stage.getId(), StageEventType.SQ_KILL));
-                                }
-                              }
-                            }
-                          } catch (Throwable e) {
-                            LOG.error("Stage (" + stage.getId() + ") ERROR: ", e);
-                            stage.setFinishTime();
-                            stage.eventHandler.handle(new StageDiagnosticsUpdateEvent(stage.getId(), e.getMessage()));
-                            stage.eventHandler.handle(new StageCompletedEvent(stage.getId(), StageState.ERROR));
-                          }
-                        }
-                      }
-              );
+          stage.getContext().getQueryMasterContext().getSingleEventExecutor().submit(() -> {
+            try {
+              schedule(stage);
+              stage.totalScheduledObjectsCount = stage.getTaskScheduler().remainingScheduledObjectNum();
+              LOG.info(stage.totalScheduledObjectsCount + " objects are scheduled");
+
+              if (stage.getTaskScheduler().remainingScheduledObjectNum() == 0) { // if there is no tasks
+                stage.eventHandler.handle(
+                    new StageEvent(stage.getId(), StageEventType.SQ_STAGE_COMPLETED));
+              } else {
+                if(stage.getSynchronizedState() == StageState.INITED) {
+                  stage.eventHandler.handle(new StageEvent(stage.getId(), StageEventType.SQ_START));
+                  stage.taskScheduler.start();
+                } else {
+                  /* all tasks are killed before stage are inited */
+                  if (stage.getTotalScheduledObjectsCount() == stage.getCompletedTaskCount()) {
+                    stage.eventHandler.handle(
+                        new StageEvent(stage.getId(), StageEventType.SQ_STAGE_COMPLETED));
+                  } else {
+                    stage.eventHandler.handle(
+                        new StageEvent(stage.getId(), StageEventType.SQ_KILL));
+                  }
+                }
+              }
+            } catch (Throwable e) {
+              LOG.error("Stage (" + stage.getId() + ") ERROR: ", e);
+              stage.setFinishTime();
+              stage.eventHandler.handle(new StageDiagnosticsUpdateEvent(stage.getId(), e.getMessage()));
+              stage.eventHandler.handle(new StageCompletedEvent(stage.getId(), StageState.ERROR));
+            }
+          });
           state = StageState.INITED;
         }
       } catch (Throwable e) {
diff --git a/tajo-core/src/main/java/org/apache/tajo/util/JSPUtil.java b/tajo-core/src/main/java/org/apache/tajo/util/JSPUtil.java
index 671a365a4a..48e085605c 100644
--- a/tajo-core/src/main/java/org/apache/tajo/util/JSPUtil.java
+++ b/tajo-core/src/main/java/org/apache/tajo/util/JSPUtil.java
@@ -87,15 +87,11 @@ public static List<QueryMasterTask> sortQueryMasterTask(Collection<QueryMasterTa
                                                           final boolean desc) {
     List<QueryMasterTask> queryMasterTaskList = new ArrayList<>(queryMasterTasks);
 
-    Collections.sort(queryMasterTaskList, new Comparator<QueryMasterTask>() {
-
-      @Override
-      public int compare(QueryMasterTask task1, QueryMasterTask task2) {
-        if(desc) {
-          return task2.getQueryId().toString().compareTo(task1.getQueryId().toString());
-        } else {
-          return task1.getQueryId().toString().compareTo(task2.getQueryId().toString());
-        }
+    Collections.sort(queryMasterTaskList, (task1, task2) -> {
+      if(desc) {
+        return task2.getQueryId().toString().compareTo(task1.getQueryId().toString());
+      } else {
+        return task1.getQueryId().toString().compareTo(task2.getQueryId().toString());
       }
     });
 
@@ -106,14 +102,11 @@ public static List<QueryInProgress> sortQueryInProgress(Collection<QueryInProgre
                                                           final boolean desc) {
     List<QueryInProgress> queryProgressList = new ArrayList<>(queryInProgresses);
 
-    Collections.sort(queryProgressList, new Comparator<QueryInProgress>() {
-      @Override
-      public int compare(QueryInProgress query1, QueryInProgress query2) {
-        if(desc) {
-          return query2.getQueryId().toString().compareTo(query1.getQueryId().toString());
-        } else {
-          return query1.getQueryId().toString().compareTo(query2.getQueryId().toString());
-        }
+    Collections.sort(queryProgressList, (query1, query2) -> {
+      if(desc) {
+        return query2.getQueryId().toString().compareTo(query1.getQueryId().toString());
+      } else {
+        return query1.getQueryId().toString().compareTo(query2.getQueryId().toString());
       }
     });
 
@@ -122,21 +115,18 @@ public int compare(QueryInProgress query1, QueryInProgress query2) {
 
   public static List<Stage> sortStages(Collection<Stage> stages) {
     List<Stage> stageList = new ArrayList<>(stages);
-    Collections.sort(stageList, new Comparator<Stage>() {
-      @Override
-      public int compare(Stage stage1, Stage stage2) {
-        long q1StartTime = stage1.getStartTime();
-        long q2StartTime = stage2.getStartTime();
-
-        q1StartTime = (q1StartTime == 0 ? Long.MAX_VALUE : q1StartTime);
-        q2StartTime = (q2StartTime == 0 ? Long.MAX_VALUE : q2StartTime);
-
-        int result = compareLong(q1StartTime, q2StartTime);
-        if (result == 0) {
-          return stage1.getId().toString().compareTo(stage2.getId().toString());
-        } else {
-          return result;
-        }
+    Collections.sort(stageList, (stage1, stage2) -> {
+      long q1StartTime = stage1.getStartTime();
+      long q2StartTime = stage2.getStartTime();
+
+      q1StartTime = (q1StartTime == 0 ? Long.MAX_VALUE : q1StartTime);
+      q2StartTime = (q2StartTime == 0 ? Long.MAX_VALUE : q2StartTime);
+
+      int result = compareLong(q1StartTime, q2StartTime);
+      if (result == 0) {
+        return stage1.getId().toString().compareTo(stage2.getId().toString());
+      } else {
+        return result;
       }
     });
 
@@ -145,21 +135,18 @@ public int compare(Stage stage1, Stage stage2) {
 
   public static List<StageHistory> sortStageHistories(Collection<StageHistory> stages) {
     List<StageHistory> stageList = new ArrayList<>(stages);
-    Collections.sort(stageList, new Comparator<StageHistory>() {
-      @Override
-      public int compare(StageHistory stage1, StageHistory stage2) {
-        long q1StartTime = stage1.getStartTime();
-        long q2StartTime = stage2.getStartTime();
-
-        q1StartTime = (q1StartTime == 0 ? Long.MAX_VALUE : q1StartTime);
-        q2StartTime = (q2StartTime == 0 ? Long.MAX_VALUE : q2StartTime);
-
-        int result = compareLong(q1StartTime, q2StartTime);
-        if (result == 0) {
-          return stage1.getExecutionBlockId().compareTo(stage2.getExecutionBlockId());
-        } else {
-          return result;
-        }
+    Collections.sort(stageList, (stage1, stage2) -> {
+      long q1StartTime = stage1.getStartTime();
+      long q2StartTime = stage2.getStartTime();
+
+      q1StartTime = (q1StartTime == 0 ? Long.MAX_VALUE : q1StartTime);
+      q2StartTime = (q2StartTime == 0 ? Long.MAX_VALUE : q2StartTime);
+
+      int result = compareLong(q1StartTime, q2StartTime);
+      if (result == 0) {
+        return stage1.getExecutionBlockId().compareTo(stage2.getExecutionBlockId());
+      } else {
+        return result;
       }
     });
 
diff --git a/tajo-core/src/main/java/org/apache/tajo/util/metrics/LogEventGaugeSet.java b/tajo-core/src/main/java/org/apache/tajo/util/metrics/LogEventGaugeSet.java
index 10d17042ca..80c0e84781 100644
--- a/tajo-core/src/main/java/org/apache/tajo/util/metrics/LogEventGaugeSet.java
+++ b/tajo-core/src/main/java/org/apache/tajo/util/metrics/LogEventGaugeSet.java
@@ -31,33 +31,13 @@ public class LogEventGaugeSet implements MetricSet {
   public Map<String, Metric> getMetrics() {
     final Map<String, Metric> gauges = new HashMap<>();
 
-    gauges.put("Fatal", new Gauge<Long>() {
-      @Override
-      public Long getValue() {
-        return TajoLogEventCounter.getFatal();
-      }
-    });
+    gauges.put("Fatal", (Gauge<Long>) () -> TajoLogEventCounter.getFatal());
 
-    gauges.put("Error", new Gauge<Long>() {
-      @Override
-      public Long getValue() {
-        return TajoLogEventCounter.getError();
-      }
-    });
+    gauges.put("Error", (Gauge<Long>) () -> TajoLogEventCounter.getError());
 
-    gauges.put("Warn", new Gauge<Long>() {
-      @Override
-      public Long getValue() {
-        return TajoLogEventCounter.getWarn();
-      }
-    });
+    gauges.put("Warn", (Gauge<Long>) () -> TajoLogEventCounter.getWarn());
 
-    gauges.put("Info", new Gauge<Long>() {
-      @Override
-      public Long getValue() {
-        return TajoLogEventCounter.getInfo();
-      }
-    });
+    gauges.put("Info", (Gauge<Long>) () -> TajoLogEventCounter.getInfo());
 
     return gauges;
   }
diff --git a/tajo-core/src/main/java/org/apache/tajo/util/metrics/reporter/TajoMetricsScheduledReporter.java b/tajo-core/src/main/java/org/apache/tajo/util/metrics/reporter/TajoMetricsScheduledReporter.java
index 7e3d9bca6e..9594c7c07a 100644
--- a/tajo-core/src/main/java/org/apache/tajo/util/metrics/reporter/TajoMetricsScheduledReporter.java
+++ b/tajo-core/src/main/java/org/apache/tajo/util/metrics/reporter/TajoMetricsScheduledReporter.java
@@ -136,14 +136,11 @@ public void start() {
    */
   public void start(long period, TimeUnit unit) {
     this.period = period;
-    executor.scheduleAtFixedRate(new Runnable() {
-      @Override
-      public void run() {
-        try {
-          report();
-        } catch (Exception e) {
-          LOG.warn("Metric report error:" + e.getMessage(), e);
-        }
+    executor.scheduleAtFixedRate((Runnable) () -> {
+      try {
+        report();
+      } catch (Exception e) {
+        LOG.warn("Metric report error:" + e.getMessage(), e);
       }
     }, period, period, unit);
   }
diff --git a/tajo-plan/src/main/java/org/apache/tajo/plan/LogicalPlanner.java b/tajo-plan/src/main/java/org/apache/tajo/plan/LogicalPlanner.java
index aaf64cd4a7..06d1ecd859 100644
--- a/tajo-plan/src/main/java/org/apache/tajo/plan/LogicalPlanner.java
+++ b/tajo-plan/src/main/java/org/apache/tajo/plan/LogicalPlanner.java
@@ -374,12 +374,7 @@ private void insertDistinctOperator(PlanContext context, ProjectionNode projecti
 
     List<ExprNormalizer.WindowSpecReferences> windowSpecReferencesList = new ArrayList<>();
 
-    List<Integer> targetsIds = normalize(context, projection, normalizedExprList, new Matcher() {
-      @Override
-      public boolean isMatch(Expr expr) {
-        return ExprFinder.finds(expr, OpType.WindowFunction).size() == 0;
-      }
-    });
+    List<Integer> targetsIds = normalize(context, projection, normalizedExprList, expr -> ExprFinder.finds(expr, OpType.WindowFunction).size() == 0);
 
     // Note: Why separate normalization and add(Named)Expr?
     //
@@ -388,12 +383,7 @@ public boolean isMatch(Expr expr) {
     // the same logical node. It will cause impossible evaluation in physical executors.
     addNamedExprs(block, referenceNames, normalizedExprList, windowSpecReferencesList, projection, targetsIds);
 
-    targetsIds = normalize(context, projection, normalizedExprList, new Matcher() {
-      @Override
-      public boolean isMatch(Expr expr) {
-        return ExprFinder.finds(expr, OpType.WindowFunction).size() > 0;
-      }
-    });
+    targetsIds = normalize(context, projection, normalizedExprList, expr -> ExprFinder.finds(expr, OpType.WindowFunction).size() > 0);
     addNamedExprs(block, referenceNames, normalizedExprList, windowSpecReferencesList, projection, targetsIds);
 
     return new Pair<>(referenceNames,
diff --git a/tajo-plan/src/main/java/org/apache/tajo/plan/exprrewrite/EvalTreeOptimizer.java b/tajo-plan/src/main/java/org/apache/tajo/plan/exprrewrite/EvalTreeOptimizer.java
index 4d742c7186..2d027da373 100644
--- a/tajo-plan/src/main/java/org/apache/tajo/plan/exprrewrite/EvalTreeOptimizer.java
+++ b/tajo-plan/src/main/java/org/apache/tajo/plan/exprrewrite/EvalTreeOptimizer.java
@@ -56,13 +56,10 @@ public class EvalTreeOptimizer {
       rules.add(rule);
     }
 
-    Collections.sort(rules, new Comparator<EvalTreeOptimizationRule>() {
-      @Override
-      public int compare(EvalTreeOptimizationRule o1, EvalTreeOptimizationRule o2) {
-        int priority1 = o1.getClass().getAnnotation(Prioritized.class).priority();
-        int priority2 = o2.getClass().getAnnotation(Prioritized.class).priority();
-        return priority1 - priority2;
-      }
+    Collections.sort(rules, (o1, o2) -> {
+      int priority1 = o1.getClass().getAnnotation(Prioritized.class).priority();
+      int priority2 = o2.getClass().getAnnotation(Prioritized.class).priority();
+      return priority1 - priority2;
     });
   }
 
diff --git a/tajo-plan/src/main/java/org/apache/tajo/plan/rewrite/SelfDescSchemaBuildPhase.java b/tajo-plan/src/main/java/org/apache/tajo/plan/rewrite/SelfDescSchemaBuildPhase.java
index a49c42389f..9243e98239 100644
--- a/tajo-plan/src/main/java/org/apache/tajo/plan/rewrite/SelfDescSchemaBuildPhase.java
+++ b/tajo-plan/src/main/java/org/apache/tajo/plan/rewrite/SelfDescSchemaBuildPhase.java
@@ -407,13 +407,8 @@ private Schema buildSchemaFromColumnSet(Set<Column> columns) throws TajoExceptio
 
       Set<Column> simpleColumns = new HashSet<>();
       List<Column> columnList = new ArrayList<>(columns);
-      Collections.sort(columnList, new Comparator<Column>() {
-        @Override
-        public int compare(Column c1, Column c2) {
-          return c2.getSimpleName().split(NestedPathUtil.PATH_DELIMITER).length -
-              c1.getSimpleName().split(NestedPathUtil.PATH_DELIMITER).length;
-        }
-      });
+      Collections.sort(columnList, (c1, c2) -> c2.getSimpleName().split(NestedPathUtil.PATH_DELIMITER).length -
+          c1.getSimpleName().split(NestedPathUtil.PATH_DELIMITER).length);
 
       for (Column eachColumn : columnList) {
         String simpleName = eachColumn.getSimpleName();
diff --git a/tajo-plan/src/main/java/org/apache/tajo/plan/serder/EvalNodeDeserializer.java b/tajo-plan/src/main/java/org/apache/tajo/plan/serder/EvalNodeDeserializer.java
index 6b38feb450..5e1ae7b4e6 100644
--- a/tajo-plan/src/main/java/org/apache/tajo/plan/serder/EvalNodeDeserializer.java
+++ b/tajo-plan/src/main/java/org/apache/tajo/plan/serder/EvalNodeDeserializer.java
@@ -62,12 +62,7 @@ public static EvalNode deserialize(OverridableConf context, EvalContext evalCont
 
     // sort serialized eval nodes in an ascending order of their IDs.
     List<PlanProto.EvalNode> nodeList = Lists.newArrayList(tree.getNodesList());
-    Collections.sort(nodeList, new Comparator<PlanProto.EvalNode>() {
-      @Override
-      public int compare(PlanProto.EvalNode o1, PlanProto.EvalNode o2) {
-        return o1.getId() - o2.getId();
-      }
-    });
+    Collections.sort(nodeList, (o1, o2) -> o1.getId() - o2.getId());
 
     EvalNode current = null;
 
diff --git a/tajo-plan/src/main/java/org/apache/tajo/plan/serder/LogicalNodeDeserializer.java b/tajo-plan/src/main/java/org/apache/tajo/plan/serder/LogicalNodeDeserializer.java
index 4b47e4ac87..03d3b6c515 100644
--- a/tajo-plan/src/main/java/org/apache/tajo/plan/serder/LogicalNodeDeserializer.java
+++ b/tajo-plan/src/main/java/org/apache/tajo/plan/serder/LogicalNodeDeserializer.java
@@ -58,12 +58,7 @@ public static LogicalNode deserialize(OverridableConf context, @Nullable EvalCon
 
     // sort serialized logical nodes in an ascending order of their sids
     List<PlanProto.LogicalNode> nodeList = Lists.newArrayList(tree.getNodesList());
-    Collections.sort(nodeList, new Comparator<PlanProto.LogicalNode>() {
-      @Override
-      public int compare(PlanProto.LogicalNode o1, PlanProto.LogicalNode o2) {
-        return o1.getVisitSeq() - o2.getVisitSeq();
-      }
-    });
+    Collections.sort(nodeList, (o1, o2) -> o1.getVisitSeq() - o2.getVisitSeq());
 
     LogicalNode current = null;
 
diff --git a/tajo-pullserver/src/main/java/org/apache/tajo/pullserver/HttpDataServerHandler.java b/tajo-pullserver/src/main/java/org/apache/tajo/pullserver/HttpDataServerHandler.java
index 15cfdf4cea..a29da18ab3 100644
--- a/tajo-pullserver/src/main/java/org/apache/tajo/pullserver/HttpDataServerHandler.java
+++ b/tajo-pullserver/src/main/java/org/apache/tajo/pullserver/HttpDataServerHandler.java
@@ -151,11 +151,9 @@ private ChannelFuture sendFile(ChannelHandlerContext ctx,
           file.startOffset(), file.length());
       writeFuture = ctx.write(region);
       lastContentFuture = ctx.write(LastHttpContent.EMPTY_LAST_CONTENT);
-      writeFuture.addListener(new ChannelFutureListener() {
-        public void operationComplete(ChannelFuture future) {
-          if (region.refCnt() > 0) {
-            region.release();
-          }
+      writeFuture.addListener(future -> {
+        if (region.refCnt() > 0) {
+          region.release();
         }
       });
     }
diff --git a/tajo-storage/tajo-storage-common/src/main/java/org/apache/tajo/storage/TablespaceManager.java b/tajo-storage/tajo-storage-common/src/main/java/org/apache/tajo/storage/TablespaceManager.java
index 88410bb2cc..8f83c3bd94 100644
--- a/tajo-storage/tajo-storage-common/src/main/java/org/apache/tajo/storage/TablespaceManager.java
+++ b/tajo-storage/tajo-storage-common/src/main/java/org/apache/tajo/storage/TablespaceManager.java
@@ -446,18 +446,8 @@ public static Iterable<Tablespace> getAllTablespaces() {
   }
 
   public static Collection<MetadataProvider> getMetadataProviders() {
-    Collection<Tablespace> filteredSpace = Collections2.filter(TABLE_SPACES.values(), new Predicate<Tablespace>() {
-      @Override
-      public boolean apply(@Nullable Tablespace space) {
-        return space.getProperty().isMetadataProvided();
-      }
-    });
+    Collection<Tablespace> filteredSpace = Collections2.filter(TABLE_SPACES.values(), space -> space.getProperty().isMetadataProvided());
 
-    return Collections2.transform(filteredSpace, new Function<Tablespace, MetadataProvider>() {
-      @Override
-      public MetadataProvider apply(@Nullable Tablespace space) {
-        return space.getMetadataProvider();
-      }
-    });
+    return Collections2.transform(filteredSpace, space -> space.getMetadataProvider());
   }
 }
diff --git a/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/FileTablespace.java b/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/FileTablespace.java
index 17c413ebfa..1a28ffdf54 100644
--- a/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/FileTablespace.java
+++ b/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/FileTablespace.java
@@ -56,11 +56,9 @@
 
 public class FileTablespace extends Tablespace {
 
-  public static final PathFilter hiddenFileFilter = new PathFilter() {
-    public boolean accept(Path p) {
-      String name = p.getName();
-      return !name.startsWith("_") && !name.startsWith(".");
-    }
+  public static final PathFilter hiddenFileFilter = p -> {
+    String name1 = p.getName();
+    return !name1.startsWith("_") && !name1.startsWith(".");
   };
   private static final Log LOG = LogFactory.getLog(FileTablespace.class);
 
@@ -424,13 +422,7 @@ protected FileFragment makeNonSplit(String fragmentId, Path file, long start, lo
     }
 
     List<Map.Entry<String, Integer>> entries = new ArrayList<>(hostsBlockMap.entrySet());
-    Collections.sort(entries, new Comparator<Map.Entry<String, Integer>>() {
-
-      @Override
-      public int compare(Map.Entry<String, Integer> v1, Map.Entry<String, Integer> v2) {
-        return v1.getValue().compareTo(v2.getValue());
-      }
-    });
+    Collections.sort(entries, (v1, v2) -> v1.getValue().compareTo(v2.getValue()));
 
     String[] hosts = new String[blkLocations[0].getHosts().length];
 
diff --git a/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/HashShuffleAppenderManager.java b/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/HashShuffleAppenderManager.java
index 79203a2dc4..5b07cd8b6b 100644
--- a/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/HashShuffleAppenderManager.java
+++ b/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/HashShuffleAppenderManager.java
@@ -206,16 +206,13 @@ public Future<MemoryRowBlock> writePartitions(TableMeta meta, Schema schema, fin
     HashShuffleAppenderWrapper appender =
         getAppender(rowBlock, taskId.getTaskId().getExecutionBlockId(), partId, meta, schema);
     ExecutorService executor = executors.get(appender.getVolumeId());
-    return executor.submit(new Callable<MemoryRowBlock>() {
-      @Override
-      public MemoryRowBlock call() throws Exception {
-        appender.writeRowBlock(taskId, rowBlock);
+    return executor.submit(() -> {
+      appender.writeRowBlock(taskId, rowBlock);
 
-        if (release) rowBlock.release();
-        else rowBlock.clear();
+      if (release) rowBlock.release();
+      else rowBlock.clear();
 
-        return rowBlock;
-      }
+      return rowBlock;
     });
   }
 
diff --git a/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/rcfile/BytesRefArrayWritable.java b/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/rcfile/BytesRefArrayWritable.java
index 5e200a0b2f..9cd7b505ee 100644
--- a/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/rcfile/BytesRefArrayWritable.java
+++ b/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/rcfile/BytesRefArrayWritable.java
@@ -249,13 +249,6 @@ public void write(DataOutput out) throws IOException {
 
   static {
     WritableFactories.setFactory(BytesRefArrayWritable.class,
-        new WritableFactory() {
-
-          @Override
-          public Writable newInstance() {
-            return new BytesRefArrayWritable();
-          }
-
-        });
+      () -> new BytesRefArrayWritable());
   }
 }
diff --git a/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/rcfile/BytesRefWritable.java b/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/rcfile/BytesRefWritable.java
index 158c740784..ac63501f7f 100644
--- a/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/rcfile/BytesRefWritable.java
+++ b/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/rcfile/BytesRefWritable.java
@@ -228,14 +228,7 @@ public boolean equals(Object right_obj) {
   }
 
   static {
-    WritableFactories.setFactory(BytesRefWritable.class, new WritableFactory() {
-
-      @Override
-      public Writable newInstance() {
-        return new BytesRefWritable();
-      }
-
-    });
+    WritableFactories.setFactory(BytesRefWritable.class, () -> new BytesRefWritable());
   }
 
   public int getLength() {
diff --git a/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/thirdparty/orc/WriterImpl.java b/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/thirdparty/orc/WriterImpl.java
index 5dedc2eae8..d0e8c6f7d4 100644
--- a/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/thirdparty/orc/WriterImpl.java
+++ b/tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/thirdparty/orc/WriterImpl.java
@@ -138,13 +138,7 @@ public WriterImpl(FileSystem fs,
     this.callback = opts.getCallback();
     this.schema = opts.getSchema();
     if (callback != null) {
-      callbackContext = new OrcFile.WriterContext(){
-
-        @Override
-        public Writer getWriter() {
-          return WriterImpl.this;
-        }
-      };
+      callbackContext = () -> WriterImpl.this;
     } else {
       callbackContext = null;
     }
diff --git a/tajo-storage/tajo-storage-jdbc/src/main/java/org/apache/tajo/storage/jdbc/JdbcMetadataProviderBase.java b/tajo-storage/tajo-storage-jdbc/src/main/java/org/apache/tajo/storage/jdbc/JdbcMetadataProviderBase.java
index fb095a40bf..bff96c84b1 100644
--- a/tajo-storage/tajo-storage-jdbc/src/main/java/org/apache/tajo/storage/jdbc/JdbcMetadataProviderBase.java
+++ b/tajo-storage/tajo-storage-jdbc/src/main/java/org/apache/tajo/storage/jdbc/JdbcMetadataProviderBase.java
@@ -204,20 +204,10 @@ public TableDesc getTableDesc(String schemaName, String tableName) throws Undefi
       }
 
       // sort columns in an order of ordinal position
-      Collections.sort(columns, new Comparator<Pair<Integer, Column>>() {
-        @Override
-        public int compare(Pair<Integer, Column> o1, Pair<Integer, Column> o2) {
-          return o1.getFirst() - o2.getFirst();
-        }
-      });
+      Collections.sort(columns, (o1, o2) -> o1.getFirst() - o2.getFirst());
 
       // transform the pair list into collection for columns
-      final Schema schema = SchemaBuilder.builder().addAll(Collections2.transform(columns, new Function<Pair<Integer,Column>, Column>() {
-        @Override
-        public Column apply(@Nullable Pair<Integer, Column> columnPair) {
-          return columnPair.getSecond();
-        }
-      })).build();
+      final Schema schema = SchemaBuilder.builder().addAll(Collections2.transform(columns, Pair::getSecond)).build();
 
 
       // fill the table stats
diff --git a/tajo-storage/tajo-storage-jdbc/src/main/java/org/apache/tajo/storage/jdbc/SQLBuilder.java b/tajo-storage/tajo-storage-jdbc/src/main/java/org/apache/tajo/storage/jdbc/SQLBuilder.java
index 14d5eb8d33..d7872d36cf 100644
--- a/tajo-storage/tajo-storage-jdbc/src/main/java/org/apache/tajo/storage/jdbc/SQLBuilder.java
+++ b/tajo-storage/tajo-storage-jdbc/src/main/java/org/apache/tajo/storage/jdbc/SQLBuilder.java
@@ -53,11 +53,8 @@ public String build(String tableName, Column [] targets, @Nullable EvalNode filt
 
     StringBuilder selectClause = new StringBuilder("SELECT ");
     if (targets.length > 0) {
-      selectClause.append(StringUtils.join(targets, ",", new Function<Column, String>() {
-        @Override
-        public String apply(@Nullable Column input) {
-          return input.getSimpleName();
-        }
+      selectClause.append(StringUtils.join(targets, ",", input -> {
+        return input.getSimpleName();
       }));
     } else {
       selectClause.append("1");
@@ -174,15 +171,12 @@ public void visitScan(SQLBuilderContext ctx, ScanNode scan, Stack<LogicalNode> s
   }
 
   public String generateTargetList(List<Target> targets) {
-    return StringUtils.join(targets, ",", new Function<Target, String>() {
-      @Override
-      public String apply(@Nullable Target t) {
-        StringBuilder sb = new StringBuilder(sqlExprGen.generate(t.getEvalTree()));
-        if (t.hasAlias()) {
-          sb.append(" AS ").append(t.getAlias());
-        }
-        return sb.toString();
+    return StringUtils.join(targets, ",", t -> {
+      StringBuilder sb = new StringBuilder(sqlExprGen.generate(t.getEvalTree()));
+      if (t.hasAlias()) {
+        sb.append(" AS ").append(t.getAlias());
       }
+      return sb.toString();
     });
   }
 }
diff --git a/tajo-storage/tajo-storage-jdbc/src/main/java/org/apache/tajo/storage/jdbc/SQLExpressionGenerator.java b/tajo-storage/tajo-storage-jdbc/src/main/java/org/apache/tajo/storage/jdbc/SQLExpressionGenerator.java
index da97e32e92..c681be1d37 100644
--- a/tajo-storage/tajo-storage-jdbc/src/main/java/org/apache/tajo/storage/jdbc/SQLExpressionGenerator.java
+++ b/tajo-storage/tajo-storage-jdbc/src/main/java/org/apache/tajo/storage/jdbc/SQLExpressionGenerator.java
@@ -128,11 +128,8 @@ protected EvalNode visitConst(Context context, ConstEval constant, Stack<EvalNod
 
   protected EvalNode visitRowConstant(Context context, RowConstantEval row, Stack<EvalNode> stack) {
     StringBuilder sb = new StringBuilder("(");
-    sb.append(StringUtils.join(row.getValues(), ",", new Function<Datum, String>() {
-      @Override
-      public String apply(Datum v) {
-        return convertDatumToSQLLiteral(v);
-      }
+    sb.append(StringUtils.join(row.getValues(), ",", v -> {
+      return convertDatumToSQLLiteral(v);
     }));
     sb.append(")");
     context.append(sb.toString());
diff --git a/tajo-storage/tajo-storage-pgsql/src/test/java/org/apache/tajo/storage/pgsql/PgSQLTestServer.java b/tajo-storage/tajo-storage-pgsql/src/test/java/org/apache/tajo/storage/pgsql/PgSQLTestServer.java
index 6de1573d4e..40f1846fc1 100644
--- a/tajo-storage/tajo-storage-pgsql/src/test/java/org/apache/tajo/storage/pgsql/PgSQLTestServer.java
+++ b/tajo-storage/tajo-storage-pgsql/src/test/java/org/apache/tajo/storage/pgsql/PgSQLTestServer.java
@@ -73,14 +73,11 @@ private PgSQLTestServer() throws Exception {
         "tpch"
     );
 
-    Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() {
-      @Override
-      public void run() {
-        try {
-          server.close();
-        } catch (IOException e) {
-          e.printStackTrace();
-        }
+    Runtime.getRuntime().addShutdownHook(new Thread(() -> {
+      try {
+        server.close();
+      } catch (IOException e) {
+        e.printStackTrace();
       }
     }));