http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/master/scheduler/SimpleScheduler.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/master/scheduler/SimpleScheduler.java 
b/tajo-core/src/main/java/org/apache/tajo/master/scheduler/SimpleScheduler.java
index e41ac95..699461f 100644
--- 
a/tajo-core/src/main/java/org/apache/tajo/master/scheduler/SimpleScheduler.java
+++ 
b/tajo-core/src/main/java/org/apache/tajo/master/scheduler/SimpleScheduler.java
@@ -75,7 +75,7 @@ public class SimpleScheduler extends AbstractQueryScheduler {
     this.masterContext = context;
     this.rmContext = rmContext;
     //Copy default array capacity from PriorityBlockingQueue.
-    this.queryQueue = new PriorityBlockingQueue<QuerySchedulingInfo>(11, 
COMPARATOR);
+    this.queryQueue = new PriorityBlockingQueue<>(11, COMPARATOR);
     this.queryProcessor = new Thread(new QueryProcessor());
   }
 
@@ -184,7 +184,7 @@ public class SimpleScheduler extends AbstractQueryScheduler 
{
       return Lists.newArrayList();
     }
 
-    LinkedList<Integer> workers = new LinkedList<Integer>();
+    LinkedList<Integer> workers = new LinkedList<>();
 
     if (request.getCandidateNodesCount() > 0) {
       workers.addAll(request.getCandidateNodesList());
@@ -197,7 +197,7 @@ public class SimpleScheduler extends AbstractQueryScheduler 
{
 
     // reserve resource in random workers
     if (reservedResources.size() < requiredContainers) {
-      LinkedList<Integer> randomNodes = new 
LinkedList<Integer>(getRMContext().getNodes().keySet());
+      LinkedList<Integer> randomNodes = new 
LinkedList<>(getRMContext().getNodes().keySet());
       Collections.shuffle(randomNodes);
 
       reservedResources.addAll(reserveClusterResource(

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/metrics/ClusterResourceMetricSet.java
----------------------------------------------------------------------
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 7454d21..1798f22 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
@@ -37,7 +37,7 @@ public class ClusterResourceMetricSet implements MetricSet {
 
   @Override
   public Map<String, Metric> getMetrics() {
-    Map<String, Metric> metricsMap = new HashMap<String, Metric>();
+    Map<String, Metric> metricsMap = new HashMap<>();
 
     metricsMap.put(Cluster.TOTAL_NODES.name(), new Gauge<Integer>() {
       @Override

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/parser/sql/SQLAnalyzer.java
----------------------------------------------------------------------
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 6190cdc..4526144 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
@@ -345,7 +345,7 @@ public class SQLAnalyzer extends SQLParserBaseVisitor<Expr> 
{
     // If grouping group is not empty
     if 
(ctx.grouping_element_list().grouping_element().get(0).empty_grouping_set() == 
null) {
       int elementSize = ctx.grouping_element_list().grouping_element().size();
-      ArrayList<GroupElement> groups = new ArrayList<GroupElement>(elementSize 
+ 1);
+      ArrayList<GroupElement> groups = new ArrayList<>(elementSize + 1);
       ArrayList<Expr> ordinaryExprs = null;
       int groupSize = 1;
       groups.add(null);
@@ -355,7 +355,7 @@ public class SQLAnalyzer extends SQLParserBaseVisitor<Expr> 
{
             ctx.grouping_element_list().grouping_element().get(i);
         if (element.ordinary_grouping_set() != null) {
           if (ordinaryExprs == null) {
-            ordinaryExprs = new ArrayList<Expr>();
+            ordinaryExprs = new ArrayList<>();
           }
           Collections.addAll(ordinaryExprs, 
getRowValuePredicandsFromOrdinaryGroupingSet(element.ordinary_grouping_set()));
         } else if (element.rollup_list() != null) {
@@ -636,7 +636,7 @@ public class SQLAnalyzer extends SQLParserBaseVisitor<Expr> 
{
   }
 
   private Expr[] 
getRowValuePredicandsFromOrdinaryGroupingSetList(Ordinary_grouping_set_listContext
 ctx) {
-    ArrayList<Expr> rowValuePredicands = new ArrayList<Expr>();
+    ArrayList<Expr> rowValuePredicands = new ArrayList<>();
     for (int i = 0; i < ctx.ordinary_grouping_set().size(); i++) {
       Collections.addAll(rowValuePredicands, 
getRowValuePredicandsFromOrdinaryGroupingSet(ctx.ordinary_grouping_set(i)));
     }
@@ -644,7 +644,7 @@ public class SQLAnalyzer extends SQLParserBaseVisitor<Expr> 
{
   }
 
   private Expr[] 
getRowValuePredicandsFromOrdinaryGroupingSet(Ordinary_grouping_setContext ctx) {
-    ArrayList<Expr> rowValuePredicands = new ArrayList<Expr>();
+    ArrayList<Expr> rowValuePredicands = new ArrayList<>();
     if (ctx.row_value_predicand() != null) {
       
rowValuePredicands.add(visitRow_value_predicand(ctx.row_value_predicand()));
     }
@@ -1357,7 +1357,7 @@ public class SQLAnalyzer extends 
SQLParserBaseVisitor<Expr> {
   @Override
   public Expr visitTruncate_table_statement(@NotNull 
Truncate_table_statementContext ctx) {
     List<Table_nameContext> tableNameContexts = ctx.table_name();
-    List<String> tableNames = new ArrayList<String>();
+    List<String> tableNames = new ArrayList<>();
 
     for (Table_nameContext eachTableNameContext: tableNameContexts) {
       tableNames.add(buildIdentifierChain(eachTableNameContext.identifier()));
@@ -1688,7 +1688,7 @@ public class SQLAnalyzer extends 
SQLParserBaseVisitor<Expr> {
 
 
   private Map<String, String> getParams(Param_clauseContext ctx) {
-    Map<String, String> params = new HashMap<String, String>();
+    Map<String, String> params = new HashMap<>();
     for (int i = 0; i < ctx.param().size(); i++) {
       params.put(stripQuote(ctx.param(i).key.getText()), 
stripQuote(ctx.param(i).value.getText()));
     }
@@ -1697,7 +1697,7 @@ public class SQLAnalyzer extends 
SQLParserBaseVisitor<Expr> {
   }
 
   public Map<String, String> escapeTableMeta(Map<String, String> map) {
-    Map<String, String> params = new HashMap<String, String>();
+    Map<String, String> params = new HashMap<>();
     for (Map.Entry<String, String> entry : map.entrySet()) {
       if (entry.getKey().equals(StorageConstants.TEXT_DELIMITER)) {
         params.put(StorageConstants.TEXT_DELIMITER, 
StringUtils.unicodeEscapedDelimiter(entry.getValue()));
@@ -1929,7 +1929,7 @@ public class SQLAnalyzer extends 
SQLParserBaseVisitor<Expr> {
   }
 
   private Map<String, String> getProperties(Property_listContext ctx) {
-    Map<String, String> params = new HashMap<String, String>();
+    Map<String, String> params = new HashMap<>();
     for (int i = 0; i < ctx.property().size(); i++) {
       params.put(stripQuote(ctx.property(i).key.getText()), 
stripQuote(ctx.property(i).value.getText()));
     }

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/querymaster/DefaultTaskScheduler.java
----------------------------------------------------------------------
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 25695a5..c705084 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
@@ -286,7 +286,7 @@ public class DefaultTaskScheduler extends 
AbstractTaskScheduler {
 
 
   protected LinkedList<TaskRequestEvent> createTaskRequest(final int 
incompleteTaskNum) throws Exception {
-    LinkedList<TaskRequestEvent> taskRequestEvents = new 
LinkedList<TaskRequestEvent>();
+    LinkedList<TaskRequestEvent> taskRequestEvents = new LinkedList<>();
 
     //If scheduled tasks is long-term task, cluster resource can be the worst 
load balance.
     //This part is to throttle the maximum required container per request
@@ -301,7 +301,7 @@ public class DefaultTaskScheduler extends 
AbstractTaskScheduler {
         getClient(serviceTracker.getUmbilicalAddress(), 
QueryCoordinatorProtocol.class, true, rpcParams);
     QueryCoordinatorProtocolService masterClientService = tmClient.getStub();
 
-    CallFuture<NodeResourceResponse> callBack = new 
CallFuture<NodeResourceResponse>();
+    CallFuture<NodeResourceResponse> callBack = new CallFuture<>();
     NodeResourceRequest.Builder request = NodeResourceRequest.newBuilder();
     request.setCapacity(NodeResources.createResource(minTaskMemory, isLeaf ? 1 
: 0).getProto())
         .setNumContainers(requestContainerNum)
@@ -380,7 +380,7 @@ public class DefaultTaskScheduler extends 
AbstractTaskScheduler {
      * These disk volumes are kept in an order of ascending order of the 
volume id.
      * In other words, the head volume ids are likely to -1, meaning no given 
volume id.
      */
-    private SortedMap<Integer, Integer> diskVolumeLoads = new TreeMap<Integer, 
Integer>();
+    private SortedMap<Integer, Integer> diskVolumeLoads = new TreeMap<>();
     /** The total number of remain tasks in this host */
     private AtomicInteger remainTasksNum = new AtomicInteger(0);
     public static final int REMOTE = -2;
@@ -395,7 +395,7 @@ public class DefaultTaskScheduler extends 
AbstractTaskScheduler {
       synchronized (unassignedTaskForEachVolume){
         LinkedHashSet<TaskAttempt> list = 
unassignedTaskForEachVolume.get(volumeId);
         if (list == null) {
-          list = new LinkedHashSet<TaskAttempt>();
+          list = new LinkedHashSet<>();
           unassignedTaskForEachVolume.put(volumeId, list);
         }
         list.add(attemptId);
@@ -653,7 +653,7 @@ public class DefaultTaskScheduler extends 
AbstractTaskScheduler {
 
         HashSet<TaskAttemptId> list = 
leafTasksRackMapping.get(hostVolumeMapping.getRack());
         if (list == null) {
-          list = new HashSet<TaskAttemptId>();
+          list = new HashSet<>();
           leafTasksRackMapping.put(hostVolumeMapping.getRack(), list);
         }
 
@@ -761,7 +761,7 @@ public class DefaultTaskScheduler extends 
AbstractTaskScheduler {
 
     public void assignToLeafTasks(LinkedList<TaskRequestEvent> taskRequests) {
       Collections.shuffle(taskRequests);
-      LinkedList<TaskRequestEvent> remoteTaskRequests = new 
LinkedList<TaskRequestEvent>();
+      LinkedList<TaskRequestEvent> remoteTaskRequests = new LinkedList<>();
       String queryMasterHostAndPort = 
context.getMasterContext().getQueryMasterContext().getWorkerContext().
           getConnectionInfo().getHostAndQMPort();
 
@@ -862,7 +862,7 @@ public class DefaultTaskScheduler extends 
AbstractTaskScheduler {
           Task task = stage.getTask(attemptId.getTaskId());
           TaskRequest taskAssign = new TaskRequestImpl(
               attemptId,
-              new ArrayList<FragmentProto>(task.getAllFragments()),
+                  new ArrayList<>(task.getAllFragments()),
               "",
               false,
               LogicalNodeSerializer.serialize(task.getLogicalPlan()),
@@ -887,7 +887,7 @@ public class DefaultTaskScheduler extends 
AbstractTaskScheduler {
           if (addr == null) addr = new 
InetSocketAddress(connectionInfo.getHost(), connectionInfo.getPeerRpcPort());
 
           AsyncRpcClient tajoWorkerRpc = null;
-          CallFuture<BatchAllocationResponse> callFuture = new 
CallFuture<BatchAllocationResponse>();
+          CallFuture<BatchAllocationResponse> callFuture = new CallFuture<>();
           totalAttempts++;
           try {
             tajoWorkerRpc = RpcClientManager.getInstance().getClient(addr, 
TajoWorkerProtocol.class, true,
@@ -1003,7 +1003,7 @@ public class DefaultTaskScheduler extends 
AbstractTaskScheduler {
           
requestProto.setExecutionBlockId(attemptId.getTaskId().getExecutionBlockId().getProto());
           context.getMasterContext().getEventHandler().handle(new 
TaskAttemptAssignedEvent(attemptId, connectionInfo));
 
-          CallFuture<BatchAllocationResponse> callFuture = new 
CallFuture<BatchAllocationResponse>();
+          CallFuture<BatchAllocationResponse> callFuture = new CallFuture<>();
 
           InetSocketAddress addr = 
stage.getAssignedWorkerMap().get(connectionInfo.getId());
           if (addr == null) addr = new 
InetSocketAddress(connectionInfo.getHost(), connectionInfo.getPeerRpcPort());

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/querymaster/Query.java
----------------------------------------------------------------------
diff --git a/tajo-core/src/main/java/org/apache/tajo/querymaster/Query.java 
b/tajo-core/src/main/java/org/apache/tajo/querymaster/Query.java
index f06d28c..10c7ffe 100644
--- a/tajo-core/src/main/java/org/apache/tajo/querymaster/Query.java
+++ b/tajo-core/src/main/java/org/apache/tajo/querymaster/Query.java
@@ -86,7 +86,7 @@ public class Query implements EventHandler<QueryEvent> {
   private int killedStagesCount = 0;
   private int failedStagesCount = 0;
   private int erroredStagesCount = 0;
-  private final List<String> diagnostics = new ArrayList<String>();
+  private final List<String> diagnostics = new ArrayList<>();
 
   // Internal Variables
   private final Lock readLock;
@@ -248,7 +248,7 @@ public class Query implements EventHandler<QueryEvent> {
       return 1.0f;
     } else {
       int idx = 0;
-      List<Stage> tempStages = new ArrayList<Stage>();
+      List<Stage> tempStages = new ArrayList<>();
       synchronized(stages) {
         tempStages.addAll(stages.values());
       }
@@ -301,7 +301,7 @@ public class Query implements EventHandler<QueryEvent> {
   }
 
   private List<StageHistory> makeStageHistories() {
-    List<StageHistory> stageHistories = new ArrayList<StageHistory>();
+    List<StageHistory> stageHistories = new ArrayList<>();
     for(Stage eachStage : getStages()) {
       stageHistories.add(eachStage.getStageHistory());
     }
@@ -318,7 +318,7 @@ public class Query implements EventHandler<QueryEvent> {
     queryHistory.setLogicalPlan(plan.getLogicalPlan().toString());
     queryHistory.setDistributedPlan(plan.toString());
 
-    List<String[]> sessionVariables = new ArrayList<String[]>();
+    List<String[]> sessionVariables = new ArrayList<>();
     for(Map.Entry<String,String> entry: 
plan.getContext().getAllKeyValus().entrySet()) {
       if (SessionVars.exists(entry.getKey()) && 
SessionVars.isPublic(SessionVars.get(entry.getKey()))) {
         sessionVariables.add(new String[]{entry.getKey(), entry.getValue()});

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/querymaster/QueryMaster.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/querymaster/QueryMaster.java 
b/tajo-core/src/main/java/org/apache/tajo/querymaster/QueryMaster.java
index 1b90080..6b26ddf 100644
--- a/tajo-core/src/main/java/org/apache/tajo/querymaster/QueryMaster.java
+++ b/tajo-core/src/main/java/org/apache/tajo/querymaster/QueryMaster.java
@@ -176,7 +176,7 @@ public class QueryMaster extends CompositeService 
implements EventHandler {
           rpcClientParams);
       QueryCoordinatorProtocolService masterService = rpc.getStub();
 
-      CallFuture<WorkerConnectionsResponse> callBack = new 
CallFuture<WorkerConnectionsResponse>();
+      CallFuture<WorkerConnectionsResponse> callBack = new CallFuture<>();
       masterService.getAllWorkers(callBack.getController(),
           PrimitiveProtos.NullProto.getDefaultInstance(), callBack);
 
@@ -186,7 +186,7 @@ public class QueryMaster extends CompositeService 
implements EventHandler {
     } catch (Exception e) {
       LOG.error(e.getMessage(), e);
     }
-    return new ArrayList<TajoProtos.WorkerConnectionInfoProto>();
+    return new ArrayList<>();
   }
 
   @Override
@@ -291,7 +291,7 @@ public class QueryMaster extends CompositeService 
implements EventHandler {
       queryMasterTasks.remove(queryId);
 
       TajoHeartbeatRequest queryHeartbeat = 
buildTajoHeartBeat(queryMasterTask);
-      CallFuture<TajoHeartbeatResponse> future = new 
CallFuture<TajoHeartbeatResponse>();
+      CallFuture<TajoHeartbeatResponse> future = new CallFuture<>();
 
       NettyClientBase tmClient;
       try {
@@ -397,7 +397,7 @@ public class QueryMaster extends CompositeService 
implements EventHandler {
     public void run() {
       LOG.info("Start QueryMaster heartbeat thread");
       while(!isStopped) {
-        List<QueryMasterTask> tempTasks = new ArrayList<QueryMasterTask>();
+        List<QueryMasterTask> tempTasks = new ArrayList<>();
         tempTasks.addAll(queryMasterTasks.values());
 
         for(QueryMasterTask eachTask: tempTasks) {
@@ -439,7 +439,7 @@ public class QueryMaster extends CompositeService 
implements EventHandler {
         } catch (InterruptedException e) {
           break;
         }
-        List<QueryMasterTask> tempTasks = new ArrayList<QueryMasterTask>();
+        List<QueryMasterTask> tempTasks = new ArrayList<>();
         tempTasks.addAll(queryMasterTasks.values());
 
         for(QueryMasterTask eachTask: tempTasks) {

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/querymaster/QueryMasterManagerService.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/querymaster/QueryMasterManagerService.java
 
b/tajo-core/src/main/java/org/apache/tajo/querymaster/QueryMasterManagerService.java
index 05e7165..c911fbc 100644
--- 
a/tajo-core/src/main/java/org/apache/tajo/querymaster/QueryMasterManagerService.java
+++ 
b/tajo-core/src/main/java/org/apache/tajo/querymaster/QueryMasterManagerService.java
@@ -245,7 +245,7 @@ public class QueryMasterManagerService extends 
CompositeService
   public void allocateQueryMaster(RpcController controller,
                                AllocationResourceProto request,
                                RpcCallback<PrimitiveProtos.BoolProto> done) {
-    CallFuture<PrimitiveProtos.BoolProto> callFuture = new 
CallFuture<PrimitiveProtos.BoolProto>();
+    CallFuture<PrimitiveProtos.BoolProto> callFuture = new CallFuture<>();
     workerContext.getNodeResourceManager().handle(new 
QMResourceAllocateEvent(request, callFuture));
 
     try {

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/querymaster/QueryMasterTask.java
----------------------------------------------------------------------
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 bcfb938..d6744c3 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
@@ -106,7 +106,7 @@ public class QueryMasterTask extends CompositeService {
 
   private NodeResource allocation;
 
-  private final List<TaskFatalErrorReport> diagnostics = new 
ArrayList<TaskFatalErrorReport>();
+  private final List<TaskFatalErrorReport> diagnostics = new ArrayList<>();
 
   private final ConcurrentMap<Integer, WorkerConnectionInfo> workerMap = 
Maps.newConcurrentMap();
 
@@ -261,7 +261,7 @@ public class QueryMasterTask extends CompositeService {
       tajoWorkerRpc = RpcClientManager.getInstance().getClient(workerAddress, 
TajoWorkerProtocol.class, true,
           rpcParams);
       TajoWorkerProtocol.TajoWorkerProtocolService tajoWorkerRpcClient = 
tajoWorkerRpc.getStub();
-      CallFuture<PrimitiveProtos.BoolProto> callFuture = new 
CallFuture<PrimitiveProtos.BoolProto>();
+      CallFuture<PrimitiveProtos.BoolProto> callFuture = new CallFuture<>();
       tajoWorkerRpcClient.killTaskAttempt(null, taskAttemptId.getProto(), 
callFuture);
 
       if(!callFuture.get().getValue()){

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/querymaster/Repartitioner.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/querymaster/Repartitioner.java 
b/tajo-core/src/main/java/org/apache/tajo/querymaster/Repartitioner.java
index bddf198..9e05882 100644
--- a/tajo-core/src/main/java/org/apache/tajo/querymaster/Repartitioner.java
+++ b/tajo-core/src/main/java/org/apache/tajo/querymaster/Repartitioner.java
@@ -187,8 +187,8 @@ public class Repartitioner {
     // Assigning either fragments or fetch urls to query units
     if (execBlock.hasBroadcastRelation()) { // If some relations of this EB 
are broadcasted
       boolean hasNonLeafNode = false;
-      List<Integer> largeScanIndexList = new ArrayList<Integer>();
-      List<Integer> broadcastIndexList = new ArrayList<Integer>();
+      List<Integer> largeScanIndexList = new ArrayList<>();
+      List<Integer> broadcastIndexList = new ArrayList<>();
       String nonLeafScanNames = "";
       String namePrefix = "";
       long maxStats = Long.MIN_VALUE;
@@ -286,7 +286,7 @@ public class Repartitioner {
     // The hash map is modeling as follows:
     // <Part Id, <EbId, List<Intermediate Data>>>
     Map<Integer, Map<ExecutionBlockId, List<IntermediateEntry>>> hashEntries =
-        new HashMap<Integer, Map<ExecutionBlockId, List<IntermediateEntry>>>();
+            new HashMap<>();
 
     // Grouping IntermediateData by a partition key and a table name
     List<ExecutionBlock> childBlocks = masterPlan.getChilds(stage.getId());
@@ -315,7 +315,7 @@ public class Repartitioner {
             }
           } else {
             Map<ExecutionBlockId, List<IntermediateEntry>> tbNameToInterm =
-                new HashMap<ExecutionBlockId, List<IntermediateEntry>>();
+                    new HashMap<>();
             tbNameToInterm.put(scanEbId, TUtil.newList(intermediateEntry));
             hashEntries.put(intermediateEntry.getPartId(), tbNameToInterm);
           }
@@ -331,7 +331,7 @@ public class Repartitioner {
             tbNameToInterm.put(scanEbId, new ArrayList<IntermediateEntry>());
         } else {
           Map<ExecutionBlockId, List<IntermediateEntry>> tbNameToInterm =
-              new HashMap<ExecutionBlockId, List<IntermediateEntry>>();
+                  new HashMap<>();
           tbNameToInterm.put(scanEbId, new ArrayList<IntermediateEntry>());
           hashEntries.put(emptyPartitionId, tbNameToInterm);
         }
@@ -365,7 +365,7 @@ public class Repartitioner {
     int joinTaskNum = Math.min(maxTaskNum, hashEntries.size());
     LOG.info("The determined number of join tasks is " + joinTaskNum);
 
-    List<Fragment> rightFragments = new ArrayList<Fragment>();
+    List<Fragment> rightFragments = new ArrayList<>();
     if (fragments.length == 2) {
       rightFragments.add(fragments[1]);
     }
@@ -419,7 +419,7 @@ public class Repartitioner {
   public static Map<Integer, Map<ExecutionBlockId, List<IntermediateEntry>>> 
mergeIntermediateByPullHost(
       Map<Integer, Map<ExecutionBlockId, List<IntermediateEntry>>> 
hashEntries) {
     Map<Integer, Map<ExecutionBlockId, List<IntermediateEntry>>> 
mergedHashEntries =
-        new HashMap<Integer, Map<ExecutionBlockId, List<IntermediateEntry>>>();
+            new HashMap<>();
 
     for(Entry<Integer, Map<ExecutionBlockId, List<IntermediateEntry>>> entry: 
hashEntries.entrySet()) {
       Integer partId = entry.getKey();
@@ -432,7 +432,7 @@ public class Repartitioner {
         // EBID + PullHost -> IntermediateEntry
         // In the case of union partEntry.getKey() return's delegated EBID.
         // Intermediate entries are merged by real EBID.
-        Map<String, IntermediateEntry> ebMerged = new HashMap<String, 
IntermediateEntry>();
+        Map<String, IntermediateEntry> ebMerged = new HashMap<>();
 
         for (IntermediateEntry eachIntermediate: intermediateList) {
           String ebMergedKey = eachIntermediate.getEbId().toString() + 
eachIntermediate.getPullHost().getPullAddress();
@@ -445,11 +445,11 @@ public class Repartitioner {
           
intermediateEntryPerPullHost.setVolume(intermediateEntryPerPullHost.getVolume() 
+ eachIntermediate.getVolume());
         }
 
-        List<IntermediateEntry> ebIntermediateEntries = new 
ArrayList<IntermediateEntry>(ebMerged.values());
+        List<IntermediateEntry> ebIntermediateEntries = new 
ArrayList<>(ebMerged.values());
 
         Map<ExecutionBlockId, List<IntermediateEntry>> mergedPartEntries = 
mergedHashEntries.get(partId);
         if (mergedPartEntries == null) {
-          mergedPartEntries = new HashMap<ExecutionBlockId, 
List<IntermediateEntry>>();
+          mergedPartEntries = new HashMap<>();
           mergedHashEntries.put(partId, mergedPartEntries);
         }
         mergedPartEntries.put(ebId, ebIntermediateEntries);
@@ -498,7 +498,7 @@ public class Repartitioner {
     //  -> SCAN
     //     . add all fragments to broadcastFragments
     Collection<Fragment> baseFragments = null;
-    List<Fragment> broadcastFragments = new ArrayList<Fragment>();
+    List<Fragment> broadcastFragments = new ArrayList<>();
     for (int i = 0; i < scans.length; i++) {
       ScanNode scan = scans[i];
       TableDesc desc = stage.getContext().getTableDesc(scan);
@@ -543,7 +543,7 @@ public class Repartitioner {
 
   private static void addJoinShuffle(Stage stage, int partitionId,
                                      Map<ExecutionBlockId, 
List<IntermediateEntry>> grouppedPartitions) {
-    Map<String, List<FetchImpl>> fetches = new HashMap<String, 
List<FetchImpl>>();
+    Map<String, List<FetchImpl>> fetches = new HashMap<>();
     for (ExecutionBlock execBlock : 
stage.getMasterPlan().getChilds(stage.getId())) {
       if (grouppedPartitions.containsKey(execBlock.getId())) {
         Collection<FetchImpl> requests = mergeShuffleRequest(partitionId, 
HASH_SHUFFLE,
@@ -569,7 +569,7 @@ public class Repartitioner {
                                                           ShuffleType type,
                                                           
List<IntermediateEntry> partitions) {
     // ebId + pullhost -> FetchImmpl
-    Map<String, FetchImpl> mergedPartitions = new HashMap<String, FetchImpl>();
+    Map<String, FetchImpl> mergedPartitions = new HashMap<>();
 
     for (IntermediateEntry partition : partitions) {
       String mergedKey = partition.getEbId().toString() + "," + 
partition.getPullHost();
@@ -603,7 +603,7 @@ public class Repartitioner {
 
   private static TableStats 
computeChildBlocksStats(QueryMasterTask.QueryMasterTaskContext context, 
MasterPlan masterPlan,
                                                     ExecutionBlockId 
parentBlockId) {
-    List<TableStats> tableStatses = new ArrayList<TableStats>();
+    List<TableStats> tableStatses = new ArrayList<>();
     List<ExecutionBlock> childBlocks = masterPlan.getChilds(parentBlockId);
     for (ExecutionBlock childBlock : childBlocks) {
       Stage childStage = context.getStage(childBlock.getId());
@@ -696,7 +696,7 @@ public class Repartitioner {
         new String[]{UNKNOWN_HOST});
     Stage.scheduleFragment(stage, dummyFragment);
 
-    List<FetchImpl> fetches = new ArrayList<FetchImpl>();
+    List<FetchImpl> fetches = new ArrayList<>();
     List<ExecutionBlock> childBlocks = masterPlan.getChilds(stage.getId());
     for (ExecutionBlock childBlock : childBlocks) {
       Stage childExecSM = stage.getContext().getStage(childBlock.getId());
@@ -710,13 +710,13 @@ public class Repartitioner {
     }
 
     SortedMap<TupleRange, Collection<FetchImpl>> map;
-    map = new TreeMap<TupleRange, Collection<FetchImpl>>();
+    map = new TreeMap<>();
 
     Set<FetchImpl> fetchSet;
     try {
       RowStoreUtil.RowStoreEncoder encoder = 
RowStoreUtil.createEncoder(sortSchema);
       for (int i = 0; i < ranges.length; i++) {
-        fetchSet = new HashSet<FetchImpl>();
+        fetchSet = new HashSet<>();
         for (FetchImpl fetch: fetches) {
           String rangeParam =
               TupleUtil.rangeToQuery(ranges[i], i == (ranges.length - 1) , 
encoder);
@@ -746,7 +746,7 @@ public class Repartitioner {
     int i;
     Map<String, List<FetchImpl>>[] fetchesArray = new Map[num];
     for (i = 0; i < num; i++) {
-      fetchesArray[i] = new HashMap<String, List<FetchImpl>>();
+      fetchesArray[i] = new HashMap<>();
     }
     i = 0;
     for (Entry<?, Collection<FetchImpl>> entry : partitions.entrySet()) {
@@ -792,16 +792,15 @@ public class Repartitioner {
 
     // TODO - We should remove dummy fragment usages
     Fragment frag = new FileFragment(scan.getCanonicalName(), new 
Path("/dummy"), 0, 0, new String[]{UNKNOWN_HOST});
-    List<Fragment> fragments = new ArrayList<Fragment>();
+    List<Fragment> fragments = new ArrayList<>();
     fragments.add(frag);
     Stage.scheduleFragments(stage, fragments);
 
-    Map<Integer, FetchGroupMeta> finalFetches = new HashMap<Integer, 
FetchGroupMeta>();
-    Map<ExecutionBlockId, List<IntermediateEntry>> intermediates = new 
HashMap<ExecutionBlockId,
-        List<IntermediateEntry>>();
+    Map<Integer, FetchGroupMeta> finalFetches = new HashMap<>();
+    Map<ExecutionBlockId, List<IntermediateEntry>> intermediates = new 
HashMap<>();
 
     for (ExecutionBlock block : masterPlan.getChilds(execBlock)) {
-      List<IntermediateEntry> partitions = new ArrayList<IntermediateEntry>();
+      List<IntermediateEntry> partitions = new ArrayList<>();
       
partitions.addAll(stage.getContext().getStage(block.getId()).getHashShuffleIntermediateEntries());
 
       // In scattered hash shuffle, Collecting each IntermediateEntry
@@ -906,7 +905,7 @@ public class Repartitioner {
     Long [] assignedVolumes = new Long[num];
     // initialization
     for (int i = 0; i < num; i++) {
-      fetchesArray[i] = new HashMap<String, List<FetchImpl>>();
+      fetchesArray[i] = new HashMap<>();
       assignedVolumes[i] = 0l;
     }
 
@@ -944,7 +943,7 @@ public class Repartitioner {
       }
     }
 
-    return new Pair<Long[], Map<String, List<FetchImpl>>[]>(assignedVolumes, 
fetchesArray);
+    return new Pair<>(assignedVolumes, fetchesArray);
   }
 
   public static void scheduleFetchesByEvenDistributedVolumes(Stage stage, 
Map<Integer, FetchGroupMeta> partitions,
@@ -974,12 +973,12 @@ public class Repartitioner {
       throw new 
RuntimeException("tajo.dist-query.table-partition.task-volume-mb should be 
great than " +
           "tajo.shuffle.hash.appender.page.volumn-mb");
     }
-    List<List<FetchImpl>> fetches = new ArrayList<List<FetchImpl>>();
+    List<List<FetchImpl>> fetches = new ArrayList<>();
 
     long totalIntermediateSize = 0L;
     for (Entry<ExecutionBlockId, List<IntermediateEntry>> listEntry : 
intermediates.entrySet()) {
       // merge by PartitionId
-      Map<Integer, List<IntermediateEntry>> partitionIntermMap = new 
HashMap<Integer, List<IntermediateEntry>>();
+      Map<Integer, List<IntermediateEntry>> partitionIntermMap = new 
HashMap<>();
       for (IntermediateEntry eachInterm: listEntry.getValue()) {
         totalIntermediateSize += eachInterm.getVolume();
         int partId = eachInterm.getPartId();
@@ -1007,7 +1006,7 @@ public class Repartitioner {
     int i = 0;
     Map<String, List<FetchImpl>>[] fetchesArray = new Map[fetches.size()];
     for(List<FetchImpl> entry : fetches) {
-      fetchesArray[i] = new HashMap<String, List<FetchImpl>>();
+      fetchesArray[i] = new HashMap<>();
       fetchesArray[i].put(tableName, entry);
 
       Stage.scheduleFetches(stage, fetchesArray[i]);
@@ -1031,13 +1030,13 @@ public class Repartitioner {
   public static List<List<FetchImpl>> splitOrMergeIntermediates(
       ExecutionBlockId ebId, List<IntermediateEntry> entries, long 
splitVolume, long pageSize) {
     // Each List<FetchImpl> has splitVolume size.
-    List<List<FetchImpl>> fetches = new ArrayList<List<FetchImpl>>();
+    List<List<FetchImpl>> fetches = new ArrayList<>();
 
     Iterator<IntermediateEntry> iter = entries.iterator();
     if (!iter.hasNext()) {
       return null;
     }
-    List<FetchImpl> fetchListForSingleTask = new ArrayList<FetchImpl>();
+    List<FetchImpl> fetchListForSingleTask = new ArrayList<>();
     long fetchListVolume = 0;
 
     while (iter.hasNext()) {
@@ -1060,7 +1059,7 @@ public class Repartitioner {
           if (!fetchListForSingleTask.isEmpty()) {
             fetches.add(fetchListForSingleTask);
           }
-          fetchListForSingleTask = new ArrayList<FetchImpl>();
+          fetchListForSingleTask = new ArrayList<>();
           fetchListVolume = 0;
         }
         FetchImpl fetch = new FetchImpl(currentInterm.getPullHost(), 
SCATTERED_HASH_SHUFFLE,
@@ -1098,7 +1097,7 @@ public class Repartitioner {
       
urlPrefix.append("&offset=").append(fetch.getOffset()).append("&length=").append(fetch.getLength());
     }
 
-    List<URI> fetchURLs = new ArrayList<URI>();
+    List<URI> fetchURLs = new ArrayList<>();
     if(includeParts) {
       if (fetch.getType() == HASH_SHUFFLE || fetch.getType() == 
SCATTERED_HASH_SHUFFLE) {
         fetchURLs.add(URI.create(urlPrefix.toString()));
@@ -1107,7 +1106,7 @@ public class Repartitioner {
         // the long request uri may cause HTTP Status Code - 414 Request-URI 
Too Long.
         // Refer to 
http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.15
         // The below code transforms a long request to multiple requests.
-        List<String> taskIdsParams = new ArrayList<String>();
+        List<String> taskIdsParams = new ArrayList<>();
         StringBuilder taskIdListBuilder = new StringBuilder();
         List<Integer> taskIds = fetch.getTaskIds();
         List<Integer> attemptIds = fetch.getAttemptIds();
@@ -1156,7 +1155,7 @@ public class Repartitioner {
   }
 
   public static Map<Integer, List<IntermediateEntry>> 
hashByKey(List<IntermediateEntry> entries) {
-    Map<Integer, List<IntermediateEntry>> hashed = new HashMap<Integer, 
List<IntermediateEntry>>();
+    Map<Integer, List<IntermediateEntry>> hashed = new HashMap<>();
     for (IntermediateEntry entry : entries) {
       if (hashed.containsKey(entry.getPartId())) {
         hashed.get(entry.getPartId()).add(entry);
@@ -1169,7 +1168,7 @@ public class Repartitioner {
   }
 
   public static Map<Task.PullHost, List<IntermediateEntry>> 
hashByHost(List<IntermediateEntry> entries) {
-    Map<Task.PullHost, List<IntermediateEntry>> hashed = new 
HashMap<Task.PullHost, List<IntermediateEntry>>();
+    Map<Task.PullHost, List<IntermediateEntry>> hashed = new HashMap<>();
 
     Task.PullHost host;
     for (IntermediateEntry entry : entries) {

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/querymaster/Stage.java
----------------------------------------------------------------------
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 98ad292..74edc48 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
@@ -101,7 +101,7 @@ public class Stage implements EventHandler<StageEvent> {
   private EventHandler<Event> eventHandler;
   private AbstractTaskScheduler taskScheduler;
   private QueryMasterTask.QueryMasterTaskContext context;
-  private final List<String> diagnostics = new ArrayList<String>();
+  private final List<String> diagnostics = new ArrayList<>();
   private StageState stageState;
 
   private long startTime;
@@ -374,7 +374,7 @@ public class Stage implements EventHandler<StageEvent> {
       if (getState() == StageState.NEW) {
         return 0.0f;
       } else {
-        tempTasks = new ArrayList<Task>(tasks.values());
+        tempTasks = new ArrayList<>(tasks.values());
       }
     } finally {
       readLock.unlock();
@@ -435,7 +435,7 @@ public class Stage implements EventHandler<StageEvent> {
   }
 
   private List<TaskHistory> makeTaskHistories() {
-    List<TaskHistory> taskHistories = new ArrayList<TaskHistory>();
+    List<TaskHistory> taskHistories = new ArrayList<>();
 
     for(Task eachTask : getTasks()) {
       taskHistories.add(eachTask.getTaskHistory());

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/querymaster/Task.java
----------------------------------------------------------------------
diff --git a/tajo-core/src/main/java/org/apache/tajo/querymaster/Task.java 
b/tajo-core/src/main/java/org/apache/tajo/querymaster/Task.java
index a586e4b..7a9c8b1 100644
--- a/tajo-core/src/main/java/org/apache/tajo/querymaster/Task.java
+++ b/tajo-core/src/main/java/org/apache/tajo/querymaster/Task.java
@@ -191,10 +191,10 @@ public class Task implements EventHandler<TaskEvent> {
                this.taskId = id;
     this.eventHandler = eventHandler;
     this.isLeafTask = isLeafTask;
-               scan = new ArrayList<ScanNode>();
+               scan = new ArrayList<>();
     fetchMap = Maps.newHashMap();
     fragMap = Maps.newHashMap();
-    shuffleFileOutputs = new ArrayList<ShuffleFileOutput>();
+    shuffleFileOutputs = new ArrayList<>();
     attempts = Collections.emptyMap();
     lastAttemptId = null;
     nextAttempt = -1;
@@ -269,7 +269,7 @@ public class Task implements EventHandler<TaskEvent> {
       }
     }
 
-    List<String> fragmentList = new ArrayList<String>();
+    List<String> fragmentList = new ArrayList<>();
     for (FragmentProto eachFragment : getAllFragments()) {
       try {
         Fragment fragment = FragmentConvertor.convert(systemConf, 
eachFragment);
@@ -281,7 +281,7 @@ public class Task implements EventHandler<TaskEvent> {
     }
     taskHistory.setFragments(fragmentList.toArray(new String[]{}));
 
-    List<String[]> fetchList = new ArrayList<String[]>();
+    List<String[]> fetchList = new ArrayList<>();
     for (Map.Entry<String, Set<FetchImpl>> e : getFetchMap().entrySet()) {
       for (FetchImpl f : e.getValue()) {
         for (URI uri : f.getSimpleURIs()){
@@ -292,7 +292,7 @@ public class Task implements EventHandler<TaskEvent> {
 
     taskHistory.setFetchs(fetchList.toArray(new String[][]{}));
 
-    List<String> dataLocationList = new ArrayList<String>();
+    List<String> dataLocationList = new ArrayList<>();
     for(DataLocation eachLocation: getDataLocations()) {
       dataLocationList.add(eachLocation.toString());
     }
@@ -305,7 +305,7 @@ public class Task implements EventHandler<TaskEvent> {
          this.plan = plan;
 
          LogicalNode node = plan;
-         ArrayList<LogicalNode> s = new ArrayList<LogicalNode>();
+         ArrayList<LogicalNode> s = new ArrayList<>();
          s.add(node);
          while (!s.isEmpty()) {
            node = s.remove(s.size()-1);
@@ -340,7 +340,7 @@ public class Task implements EventHandler<TaskEvent> {
     if (fragMap.containsKey(fragment.getTableName())) {
       fragmentProtos = fragMap.get(fragment.getTableName());
     } else {
-      fragmentProtos = new HashSet<FragmentProto>();
+      fragmentProtos = new HashSet<>();
       fragMap.put(fragment.getTableName(), fragmentProtos);
     }
     fragmentProtos.add(fragment.getProto());
@@ -381,7 +381,7 @@ public class Task implements EventHandler<TaskEvent> {
        }
 
   public Collection<FragmentProto> getAllFragments() {
-    Set<FragmentProto> fragmentProtos = new HashSet<FragmentProto>();
+    Set<FragmentProto> fragmentProtos = new HashSet<>();
     for (Set<FragmentProto> eachFragmentSet : fragMap.values()) {
       fragmentProtos.addAll(eachFragmentSet);
     }
@@ -547,7 +547,7 @@ public class Task implements EventHandler<TaskEvent> {
 
       case 1:
         Map<TaskAttemptId, TaskAttempt> newAttempts
-            = new LinkedHashMap<TaskAttemptId, TaskAttempt>(3);
+            = new LinkedHashMap<>(3);
         newAttempts.putAll(attempts);
         attempts = newAttempts;
         attempts.put(attempt.getId(), attempt);
@@ -716,7 +716,7 @@ public class Task implements EventHandler<TaskEvent> {
   }
 
   public void setIntermediateData(Collection<IntermediateEntry> partitions) {
-    this.intermediateData = new ArrayList<IntermediateEntry>(partitions);
+    this.intermediateData = new ArrayList<>(partitions);
   }
 
   public List<IntermediateEntry> getIntermediateData() {
@@ -795,14 +795,14 @@ public class Task implements EventHandler<TaskEvent> {
       this.host = new PullHost(pullHost[0], Integer.parseInt(pullHost[1]));
       this.volume = proto.getVolume();
 
-      failureRowNums = new ArrayList<Pair<Long, Pair<Integer, Integer>>>();
+      failureRowNums = new ArrayList<>();
       for (FailureIntermediateProto eachFailure: proto.getFailuresList()) {
 
         failureRowNums.add(new Pair(eachFailure.getPagePos(),
             new Pair(eachFailure.getStartRowNum(), 
eachFailure.getEndRowNum())));
       }
 
-      pages = new ArrayList<Pair<Long, Integer>>();
+      pages = new ArrayList<>();
       for (IntermediateEntryProto.PageProto eachPage: proto.getPagesList()) {
         pages.add(new Pair(eachPage.getPos(), eachPage.getLength()));
       }
@@ -873,7 +873,7 @@ public class Task implements EventHandler<TaskEvent> {
     }
 
     public List<Pair<Long, Long>> split(long firstSplitVolume, long 
splitVolume) {
-      List<Pair<Long, Long>> splits = new ArrayList<Pair<Long, Long>>();
+      List<Pair<Long, Long>> splits = new ArrayList<>();
 
       if (pages == null || pages.isEmpty()) {
         return splits;

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/querymaster/TaskAttempt.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/querymaster/TaskAttempt.java 
b/tajo-core/src/main/java/org/apache/tajo/querymaster/TaskAttempt.java
index cda62a4..3f03411 100644
--- a/tajo-core/src/main/java/org/apache/tajo/querymaster/TaskAttempt.java
+++ b/tajo-core/src/main/java/org/apache/tajo/querymaster/TaskAttempt.java
@@ -59,7 +59,7 @@ public class TaskAttempt implements 
EventHandler<TaskAttemptEvent> {
   private final Lock readLock;
   private final Lock writeLock;
 
-  private final List<String> diagnostics = new ArrayList<String>();
+  private final List<String> diagnostics = new ArrayList<>();
 
   private final TaskAttemptScheduleContext scheduleContext;
 
@@ -266,7 +266,7 @@ public class TaskAttempt implements 
EventHandler<TaskAttemptEvent> {
   private void fillTaskStatistics(TaskCompletionReport report) {
     this.progress = 1.0f;
 
-    List<IntermediateEntry> partitions = new ArrayList<IntermediateEntry>();
+    List<IntermediateEntry> partitions = new ArrayList<>();
 
     if (report.getShuffleFileOutputsCount() > 0) {
       this.getTask().setShuffleFileOutputs(report.getShuffleFileOutputsList());

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/session/Session.java
----------------------------------------------------------------------
diff --git a/tajo-core/src/main/java/org/apache/tajo/session/Session.java 
b/tajo-core/src/main/java/org/apache/tajo/session/Session.java
index 0d067dc..54aab20 100644
--- a/tajo-core/src/main/java/org/apache/tajo/session/Session.java
+++ b/tajo-core/src/main/java/org/apache/tajo/session/Session.java
@@ -41,7 +41,7 @@ public class Session implements SessionConstants, 
ProtoObject<SessionProto>, Clo
   private final String userName;
   private String currentDatabase;
   private final Map<String, String> sessionVariables;
-  private final Map<QueryId, NonForwardQueryResultScanner> nonForwardQueryMap 
= new HashMap<QueryId, NonForwardQueryResultScanner>();
+  private final Map<QueryId, NonForwardQueryResultScanner> nonForwardQueryMap 
= new HashMap<>();
   private LoadingCache<String, Expr> cache;
 
   // transient status
@@ -53,7 +53,7 @@ public class Session implements SessionConstants, 
ProtoObject<SessionProto>, Clo
     this.currentDatabase = databaseName;
     this.lastAccessTime = System.currentTimeMillis();
 
-    this.sessionVariables = new HashMap<String, String>();
+    this.sessionVariables = new HashMap<>();
     sessionVariables.put(SessionVars.SESSION_ID.keyname(), sessionId);
     sessionVariables.put(SessionVars.USERNAME.keyname(), userName);
     selectDatabase(databaseName);

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/session/SessionManager.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/session/SessionManager.java 
b/tajo-core/src/main/java/org/apache/tajo/session/SessionManager.java
index a69533f..38a39ab 100644
--- a/tajo-core/src/main/java/org/apache/tajo/session/SessionManager.java
+++ b/tajo-core/src/main/java/org/apache/tajo/session/SessionManager.java
@@ -34,7 +34,7 @@ import java.util.concurrent.ConcurrentHashMap;
 public class SessionManager extends CompositeService implements 
EventHandler<SessionEvent> {
   private static final Log LOG = LogFactory.getLog(SessionManager.class);
 
-  public final ConcurrentHashMap<String, Session> sessions = new 
ConcurrentHashMap<String, Session>();
+  public final ConcurrentHashMap<String, Session> sessions = new 
ConcurrentHashMap<>();
   private final Dispatcher dispatcher;
   private SessionLivelinessMonitor sessionLivelinessMonitor;
 

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/util/JSPUtil.java
----------------------------------------------------------------------
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 919b2c2..f7928ea 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
@@ -87,7 +87,7 @@ public class JSPUtil {
 
   public static List<QueryMasterTask> 
sortQueryMasterTask(Collection<QueryMasterTask> queryMasterTasks,
                                                           final boolean desc) {
-    List<QueryMasterTask> queryMasterTaskList = new 
ArrayList<QueryMasterTask>(queryMasterTasks);
+    List<QueryMasterTask> queryMasterTaskList = new 
ArrayList<>(queryMasterTasks);
 
     Collections.sort(queryMasterTaskList, new Comparator<QueryMasterTask>() {
 
@@ -106,7 +106,7 @@ public class JSPUtil {
 
   public static List<QueryInProgress> 
sortQueryInProgress(Collection<QueryInProgress> queryInProgresses,
                                                           final boolean desc) {
-    List<QueryInProgress> queryProgressList = new 
ArrayList<QueryInProgress>(queryInProgresses);
+    List<QueryInProgress> queryProgressList = new 
ArrayList<>(queryInProgresses);
 
     Collections.sort(queryProgressList, new Comparator<QueryInProgress>() {
       @Override
@@ -123,7 +123,7 @@ public class JSPUtil {
   }
 
   public static List<Stage> sortStages(Collection<Stage> stages) {
-    List<Stage> stageList = new ArrayList<Stage>(stages);
+    List<Stage> stageList = new ArrayList<>(stages);
     Collections.sort(stageList, new Comparator<Stage>() {
       @Override
       public int compare(Stage stage1, Stage stage2) {
@@ -146,7 +146,7 @@ public class JSPUtil {
   }
 
   public static List<StageHistory> sortStageHistories(Collection<StageHistory> 
stages) {
-    List<StageHistory> stageList = new ArrayList<StageHistory>(stages);
+    List<StageHistory> stageList = new ArrayList<>(stages);
     Collections.sort(stageList, new Comparator<StageHistory>() {
       @Override
       public int compare(StageHistory stage1, StageHistory stage2) {
@@ -380,7 +380,7 @@ public class JSPUtil {
 
   public static <T extends Object> List<T> getPageNavigationList(List<T> 
originList, int page, int pageSize) {
     if (originList == null) {
-      return new ArrayList<T>();
+      return new ArrayList<>();
     }
     int start = (page - 1) * pageSize;
     int end = start + pageSize;

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/util/history/HistoryReader.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/util/history/HistoryReader.java 
b/tajo-core/src/main/java/org/apache/tajo/util/history/HistoryReader.java
index 66077cf..5261335 100644
--- a/tajo-core/src/main/java/org/apache/tajo/util/history/HistoryReader.java
+++ b/tajo-core/src/main/java/org/apache/tajo/util/history/HistoryReader.java
@@ -247,13 +247,13 @@ public class HistoryReader {
   public List<TaskHistory> getTaskHistory(String queryId, String ebId, long 
startTime) throws IOException {
     Path queryHistoryFile = getQueryHistoryFilePath(queryId, startTime);
     if (queryHistoryFile == null) {
-      return new ArrayList<TaskHistory>();
+      return new ArrayList<>();
     }
     Path detailFile = new Path(queryHistoryFile.getParent(), ebId + 
HistoryWriter.HISTORY_FILE_POSTFIX);
     FileSystem fs = HistoryWriter.getNonCrcFileSystem(detailFile, tajoConf);
 
     if (!fs.exists(detailFile)) {
-      return new ArrayList<TaskHistory>();
+      return new ArrayList<>();
     }
 
     FileStatus fileStatus = fs.getFileStatus(detailFile);

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/util/history/HistoryWriter.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/util/history/HistoryWriter.java 
b/tajo-core/src/main/java/org/apache/tajo/util/history/HistoryWriter.java
index 5fca7a7..bc62cac 100644
--- a/tajo-core/src/main/java/org/apache/tajo/util/history/HistoryWriter.java
+++ b/tajo-core/src/main/java/org/apache/tajo/util/history/HistoryWriter.java
@@ -61,9 +61,9 @@ public class HistoryWriter extends AbstractService {
   public static final String HISTORY_FILE_POSTFIX = ".hist";
 
   private final LinkedBlockingQueue<WriterFuture<WriterHolder>>
-      historyQueue = new LinkedBlockingQueue<WriterFuture<WriterHolder>>();
+      historyQueue = new LinkedBlockingQueue<>();
   // key: yyyyMMddHH
-  private Map<String, WriterHolder> taskWriters = new HashMap<String, 
WriterHolder>();
+  private Map<String, WriterHolder> taskWriters = new HashMap<>();
 
   // For TajoMaster's query list
   private WriterHolder querySummaryWriter = null;
@@ -131,7 +131,7 @@ public class HistoryWriter extends AbstractService {
 
   /* asynchronously append to history file */
   public WriterFuture<WriterHolder> appendHistory(History history) {
-    WriterFuture<WriterHolder> future = new 
WriterFuture<WriterHolder>(history);
+    WriterFuture<WriterHolder> future = new WriterFuture<>(history);
     historyQueue.add(future);
     return future;
   }
@@ -255,7 +255,7 @@ public class HistoryWriter extends AbstractService {
         Calendar cal = Calendar.getInstance();
         cal.add(Calendar.HOUR_OF_DAY, -2);
         String closeTargetTime = df.format(cal.getTime());
-        List<String> closingTargets = new ArrayList<String>();
+        List<String> closingTargets = new ArrayList<>();
 
         for (String eachWriterTime : taskWriters.keySet()) {
           if (eachWriterTime.compareTo(closeTargetTime) <= 0) {

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/util/history/QueryHistory.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/util/history/QueryHistory.java 
b/tajo-core/src/main/java/org/apache/tajo/util/history/QueryHistory.java
index fdc45a1..46d333d 100644
--- a/tajo-core/src/main/java/org/apache/tajo/util/history/QueryHistory.java
+++ b/tajo-core/src/main/java/org/apache/tajo/util/history/QueryHistory.java
@@ -124,7 +124,7 @@ public class QueryHistory implements GsonObject, History {
       .setLogicalPlan(logicalPlan)
       .setDistributedPlan(distributedPlan);
 
-    List<KeyValueProto> sessionProtos = new ArrayList<KeyValueProto>();
+    List<KeyValueProto> sessionProtos = new ArrayList<>();
 
     if (sessionVariables != null) {
       KeyValueProto.Builder keyValueBuilder = KeyValueProto.newBuilder();
@@ -139,7 +139,7 @@ public class QueryHistory implements GsonObject, History {
     builder.addAllSessionVariables(sessionProtos);
 
 
-    List<StageHistoryProto> stageHistoryProtos = new 
ArrayList<ClientProtos.StageHistoryProto>();
+    List<StageHistoryProto> stageHistoryProtos = new ArrayList<>();
     if (stageHistories != null) {
       for (StageHistory eachStage: stageHistories) {
         stageHistoryProtos.add((eachStage.getProto()));

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/util/history/StageHistory.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/util/history/StageHistory.java 
b/tajo-core/src/main/java/org/apache/tajo/util/history/StageHistory.java
index e760f86..03b7fac 100644
--- a/tajo-core/src/main/java/org/apache/tajo/util/history/StageHistory.java
+++ b/tajo-core/src/main/java/org/apache/tajo/util/history/StageHistory.java
@@ -236,7 +236,7 @@ public class StageHistory implements GsonObject {
 
   public static List<TaskHistory> fromJsonTasks(String json) {
     if (json == null || json.trim().isEmpty()) {
-      return new ArrayList<TaskHistory>();
+      return new ArrayList<>();
     }
     return CoreGsonHelper.getInstance().fromJson(json, new 
TypeToken<List<TaskHistory>>() {
     }.getType());

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/util/metrics/LogEventGaugeSet.java
----------------------------------------------------------------------
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 6e130ff..10d1704 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
@@ -29,7 +29,7 @@ public class LogEventGaugeSet implements MetricSet {
 
   @Override
   public Map<String, Metric> getMetrics() {
-    final Map<String, Metric> gauges = new HashMap<String, Metric>();
+    final Map<String, Metric> gauges = new HashMap<>();
 
     gauges.put("Fatal", new Gauge<Long>() {
       @Override

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/util/metrics/MetricsFilterList.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/util/metrics/MetricsFilterList.java 
b/tajo-core/src/main/java/org/apache/tajo/util/metrics/MetricsFilterList.java
index b2fc6e4..e3c2a78 100644
--- 
a/tajo-core/src/main/java/org/apache/tajo/util/metrics/MetricsFilterList.java
+++ 
b/tajo-core/src/main/java/org/apache/tajo/util/metrics/MetricsFilterList.java
@@ -25,7 +25,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class MetricsFilterList implements MetricFilter {
-  List<MetricFilter> filters = new ArrayList<MetricFilter>();
+  List<MetricFilter> filters = new ArrayList<>();
 
   public void addMetricFilter(MetricFilter filter) {
     filters.add(filter);

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/util/metrics/RegexpMetricsFilter.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/util/metrics/RegexpMetricsFilter.java 
b/tajo-core/src/main/java/org/apache/tajo/util/metrics/RegexpMetricsFilter.java
index 4faa3e7..ef74a4e 100644
--- 
a/tajo-core/src/main/java/org/apache/tajo/util/metrics/RegexpMetricsFilter.java
+++ 
b/tajo-core/src/main/java/org/apache/tajo/util/metrics/RegexpMetricsFilter.java
@@ -27,7 +27,7 @@ import java.util.List;
 import java.util.regex.Pattern;
 
 public class RegexpMetricsFilter implements MetricFilter {
-  List<Pattern> filterPatterns = new ArrayList<Pattern>();
+  List<Pattern> filterPatterns = new ArrayList<>();
 
   public RegexpMetricsFilter(Collection<String> filterExpressions) {
     for(String eachExpression: filterExpressions) {

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/util/metrics/TajoSystemMetrics.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/util/metrics/TajoSystemMetrics.java 
b/tajo-core/src/main/java/org/apache/tajo/util/metrics/TajoSystemMetrics.java
index ecdf5ef..8d02ddd 100644
--- 
a/tajo-core/src/main/java/org/apache/tajo/util/metrics/TajoSystemMetrics.java
+++ 
b/tajo-core/src/main/java/org/apache/tajo/util/metrics/TajoSystemMetrics.java
@@ -45,7 +45,7 @@ public class TajoSystemMetrics extends TajoMetrics {
 
   private String hostAndPort;
 
-  private List<TajoMetricsScheduledReporter> metricsReporters = new 
ArrayList<TajoMetricsScheduledReporter>();
+  private List<TajoMetricsScheduledReporter> metricsReporters = new 
ArrayList<>();
 
   private boolean inited = false;
 
@@ -126,7 +126,7 @@ public class TajoSystemMetrics extends TajoMetrics {
 
   private void setMetricsReporter(String groupName) {
     // reporter name -> class name
-    Map<String, String> reporters = new HashMap<String, String>();
+    Map<String, String> reporters = new HashMap<>();
 
     List<String> reporterNames = metricsProps.getList(groupName + 
".reporters");
     if(reporterNames.isEmpty()) {
@@ -134,7 +134,7 @@ public class TajoSystemMetrics extends TajoMetrics {
       return;
     }
 
-    Map<String, String> allReporterProperties = new HashMap<String, String>();
+    Map<String, String> allReporterProperties = new HashMap<>();
 
     Iterator<String> keys = metricsProps.getKeys();
     while (keys.hasNext()) {
@@ -191,7 +191,7 @@ public class TajoSystemMetrics extends TajoMetrics {
   }
 
   private Map<String, String> findMetircsProperties(Map<String, String> 
allReporterProperties, String findKey) {
-    Map<String, String> metricsProperties = new HashMap<String, String>();
+    Map<String, String> metricsProperties = new HashMap<>();
 
     for (Map.Entry<String, String> entry: allReporterProperties.entrySet()) {
       String eachKey = entry.getKey();

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/util/metrics/reporter/TajoMetricsReporter.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/util/metrics/reporter/TajoMetricsReporter.java
 
b/tajo-core/src/main/java/org/apache/tajo/util/metrics/reporter/TajoMetricsReporter.java
index 584fcbe..d6e27d3 100644
--- 
a/tajo-core/src/main/java/org/apache/tajo/util/metrics/reporter/TajoMetricsReporter.java
+++ 
b/tajo-core/src/main/java/org/apache/tajo/util/metrics/reporter/TajoMetricsReporter.java
@@ -32,10 +32,10 @@ public abstract class TajoMetricsReporter {
                               SortedMap<String, Timer> timers);
 
   public <T> Map<String, Map<String, T>> 
findMetricsItemGroup(SortedMap<String, T> metricsMap) {
-    Map<String, Map<String, T>> metricsGroup = new HashMap<String, Map<String, 
T>>();
+    Map<String, Map<String, T>> metricsGroup = new HashMap<>();
 
     String previousGroup = null;
-    Map<String, T> groupItems = new HashMap<String, T>();
+    Map<String, T> groupItems = new HashMap<>();
 
     for (Map.Entry<String, T> entry : metricsMap.entrySet()) {
       String key = entry.getKey();
@@ -66,7 +66,7 @@ public abstract class TajoMetricsReporter {
 
       if (previousGroup != null && !previousGroup.equals(groupName)) {
         metricsGroup.put(previousGroup, groupItems);
-        groupItems = new HashMap<String, T>();
+        groupItems = new HashMap<>();
       }
       groupItems.put(itemName, entry.getValue());
       previousGroup = groupName;

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/util/metrics/reporter/TajoMetricsScheduledReporter.java
----------------------------------------------------------------------
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 7e0ec4a..7e3d9bc 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
@@ -103,7 +103,7 @@ public abstract class TajoMetricsScheduledReporter extends 
TajoMetricsReporter i
     filterList.addMetricFilter(new GroupNameMetricsFilter(metricsName));
 
     String regexpFilterKey = metricsPropertyKey + "regexp.";
-    Set<String> regexpExpressions = new HashSet<String>();
+    Set<String> regexpExpressions = new HashSet<>();
 
     for(Map.Entry<String, String> entry: metricsProperties.entrySet()) {
       String key = entry.getKey();

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/webapp/HttpServer.java
----------------------------------------------------------------------
diff --git a/tajo-core/src/main/java/org/apache/tajo/webapp/HttpServer.java 
b/tajo-core/src/main/java/org/apache/tajo/webapp/HttpServer.java
index 60faef2..72309eb 100644
--- a/tajo-core/src/main/java/org/apache/tajo/webapp/HttpServer.java
+++ b/tajo-core/src/main/java/org/apache/tajo/webapp/HttpServer.java
@@ -51,9 +51,9 @@ public class HttpServer {
   protected final Connector listener;
   protected final WebAppContext webAppContext;
   protected final boolean findPort;
-  protected final Map<Context, Boolean> defaultContexts = 
-      new HashMap<Context, Boolean>();
-  protected final List<String> filterNames = new ArrayList<String>();
+  protected final Map<Context, Boolean> defaultContexts =
+          new HashMap<>();
+  protected final List<String> filterNames = new ArrayList<>();
   private static final int MAX_RETRIES = 10;
   private final boolean listenerStartedExternally;
   static final String STATE_DESCRIPTION_ALIVE = " - alive";

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/webapp/QueryExecutorServlet.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/webapp/QueryExecutorServlet.java 
b/tajo-core/src/main/java/org/apache/tajo/webapp/QueryExecutorServlet.java
index a04ff6c..896c83e 100644
--- a/tajo-core/src/main/java/org/apache/tajo/webapp/QueryExecutorServlet.java
+++ b/tajo-core/src/main/java/org/apache/tajo/webapp/QueryExecutorServlet.java
@@ -71,7 +71,7 @@ public class QueryExecutorServlet extends HttpServlet {
 
   //queryRunnerId -> QueryRunner
   //TODO We must handle the session.
-  private transient final Map<String, QueryRunner> queryRunners = new 
HashMap<String, QueryRunner>();
+  private transient final Map<String, QueryRunner> queryRunners = new 
HashMap<>();
 
   private transient TajoConf tajoConf;
   private transient TajoClient tajoClient;
@@ -105,7 +105,7 @@ public class QueryExecutorServlet extends HttpServlet {
   public void service(HttpServletRequest request,
                       HttpServletResponse response) throws ServletException, 
IOException {
     String action = request.getParameter("action");
-    Map<String, Object> returnValue = new HashMap<String, Object>();
+    Map<String, Object> returnValue = new HashMap<>();
     try {
       if(tajoClient == null) {
         errorResponse(response, "TajoClient not initialized");
@@ -241,7 +241,7 @@ public class QueryExecutorServlet extends HttpServlet {
   }
 
   private void errorResponse(HttpServletResponse response, String message) 
throws IOException {
-    Map<String, Object> errorMessage = new HashMap<String, Object>();
+    Map<String, Object> errorMessage = new HashMap<>();
     errorMessage.put("success", "false");
     errorMessage.put("errorMessage", message);
     writeHttpResponse(response, errorMessage);
@@ -261,7 +261,7 @@ public class QueryExecutorServlet extends HttpServlet {
     public void run() {
       List<QueryRunner> queryRunnerList;
       synchronized(queryRunners) {
-        queryRunnerList = new ArrayList<QueryRunner>(queryRunners.values());
+        queryRunnerList = new ArrayList<>(queryRunners.values());
         for(QueryRunner eachQueryRunner: queryRunnerList) {
           if(!eachQueryRunner.running.get() &&
               (System.currentTimeMillis() - eachQueryRunner.finishTime > 180 * 
1000)) {
@@ -291,7 +291,7 @@ public class QueryExecutorServlet extends HttpServlet {
 
     AtomicInteger progress = new AtomicInteger(0);
 
-    List<String> columnNames = new ArrayList<String>();
+    List<String> columnNames = new ArrayList<>();
 
     List<List<Object>> queryResult;
 
@@ -499,7 +499,7 @@ public class QueryExecutorServlet extends HttpServlet {
       for(int i = 0; i < numOfColumns; i++) {
         columnNames.add(rsmd.getColumnName(i + 1));
       }
-      queryResult = new ArrayList<List<Object>>();
+      queryResult = new ArrayList<>();
 
       if(sizeLimit < resultRows) {
         numOfRows = (long)((float)(resultRows) * ((float)sizeLimit / (float) 
resultRows));
@@ -512,7 +512,7 @@ public class QueryExecutorServlet extends HttpServlet {
         if(rowCount > numOfRows) {
           break;
         }
-        List<Object> row = new ArrayList<Object>();
+        List<Object> row = new ArrayList<>();
         for(int i = 0; i < numOfColumns; i++) {
           row.add(String.valueOf(res.getObject(i + 1)));
         }

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/worker/ExecutionBlockContext.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/worker/ExecutionBlockContext.java 
b/tajo-core/src/main/java/org/apache/tajo/worker/ExecutionBlockContext.java
index a3cc8fc..db28433 100644
--- a/tajo-core/src/main/java/org/apache/tajo/worker/ExecutionBlockContext.java
+++ b/tajo-core/src/main/java/org/apache/tajo/worker/ExecutionBlockContext.java
@@ -251,7 +251,7 @@ public class ExecutionBlockContext {
 
     try {
       //If QueryMaster does not responding, current execution block should be 
stop
-      CallFuture<PrimitiveProtos.NullProto> callFuture = new 
CallFuture<PrimitiveProtos.NullProto>();
+      CallFuture<PrimitiveProtos.NullProto> callFuture = new CallFuture<>();
       getStub().fatalError(callFuture.getController(), builder.build(), 
callFuture);
       callFuture.get(RpcConstants.FUTURE_TIMEOUT_SECONDS_DEFAULT, 
TimeUnit.SECONDS);
     } catch (Exception e) {
@@ -298,7 +298,7 @@ public class ExecutionBlockContext {
       if (shuffles == null) {
         reporterBuilder.addAllIntermediateEntries(intermediateEntries);
 
-        CallFuture<PrimitiveProtos.NullProto> callFuture = new 
CallFuture<PrimitiveProtos.NullProto>();
+        CallFuture<PrimitiveProtos.NullProto> callFuture = new CallFuture<>();
         stub.doneExecutionBlock(callFuture.getController(), 
reporterBuilder.build(), callFuture);
         callFuture.get(RpcConstants.FUTURE_TIMEOUT_SECONDS_DEFAULT, 
TimeUnit.SECONDS);
         return;
@@ -353,7 +353,7 @@ public class ExecutionBlockContext {
       }
     }
     try {
-      CallFuture<PrimitiveProtos.NullProto> callFuture = new 
CallFuture<PrimitiveProtos.NullProto>();
+      CallFuture<PrimitiveProtos.NullProto> callFuture = new CallFuture<>();
       stub.doneExecutionBlock(callFuture.getController(), 
reporterBuilder.build(), callFuture);
       callFuture.get(RpcConstants.FUTURE_TIMEOUT_SECONDS_DEFAULT, 
TimeUnit.SECONDS);
     } catch (Throwable e) {
@@ -391,7 +391,7 @@ public class ExecutionBlockContext {
               if(tasks.size() == 0){
                 masterStub.ping(null, getExecutionBlockId().getProto(), 
NullCallback.get());
               } else {
-                for (Task task : new ArrayList<Task>(tasks.values())){
+                for (Task task : new ArrayList<>(tasks.values())){
 
                   if (task.getTaskContext().getState() ==
                       TajoProtos.TaskAttemptState.TA_RUNNING && 
task.isProgressChanged()) {

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/worker/ExecutionBlockSharedResource.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/worker/ExecutionBlockSharedResource.java
 
b/tajo-core/src/main/java/org/apache/tajo/worker/ExecutionBlockSharedResource.java
index 1a83104..d55c4ba 100644
--- 
a/tajo-core/src/main/java/org/apache/tajo/worker/ExecutionBlockSharedResource.java
+++ 
b/tajo-core/src/main/java/org/apache/tajo/worker/ExecutionBlockSharedResource.java
@@ -96,7 +96,7 @@ public class ExecutionBlockSharedResource {
   public EvalNode getPreCompiledEval(Schema schema, EvalNode eval) {
     if (codeGenEnabled) {
 
-      Pair<Schema, EvalNode> key = new Pair<Schema, EvalNode>(schema, eval);
+      Pair<Schema, EvalNode> key = new Pair<>(schema, eval);
       if (compilationContext.getPrecompiedEvals().containsKey(key)) {
         return compilationContext.getPrecompiedEvals().get(key);
       } else {

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/worker/FetchImpl.java
----------------------------------------------------------------------
diff --git a/tajo-core/src/main/java/org/apache/tajo/worker/FetchImpl.java 
b/tajo-core/src/main/java/org/apache/tajo/worker/FetchImpl.java
index 07a9ba6..3fa9d11 100644
--- a/tajo-core/src/main/java/org/apache/tajo/worker/FetchImpl.java
+++ b/tajo-core/src/main/java/org/apache/tajo/worker/FetchImpl.java
@@ -53,8 +53,8 @@ public class FetchImpl implements ProtoObject<FetchProto>, 
Cloneable {
   private long length = -1;
 
   public FetchImpl() {
-    taskIds = new ArrayList<Integer>();
-    attemptIds = new ArrayList<Integer>();
+    taskIds = new ArrayList<>();
+    attemptIds = new ArrayList<>();
   }
 
   public FetchImpl(FetchProto proto) {

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/worker/NodeStatusUpdater.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/worker/NodeStatusUpdater.java 
b/tajo-core/src/main/java/org/apache/tajo/worker/NodeStatusUpdater.java
index a3b71e1..3ca0bfb 100644
--- a/tajo-core/src/main/java/org/apache/tajo/worker/NodeStatusUpdater.java
+++ b/tajo-core/src/main/java/org/apache/tajo/worker/NodeStatusUpdater.java
@@ -165,7 +165,7 @@ public class NodeStatusUpdater extends AbstractService 
implements EventHandler<N
 
     NodeHeartbeatResponse response = null;
     try {
-      CallFuture<NodeHeartbeatResponse> callBack = new 
CallFuture<NodeHeartbeatResponse>();
+      CallFuture<NodeHeartbeatResponse> callBack = new CallFuture<>();
 
       resourceTracker.nodeHeartbeat(callBack.getController(), requestProto, 
callBack);
       response = callBack.get(RpcConstants.FUTURE_TIMEOUT_SECONDS_DEFAULT, 
TimeUnit.SECONDS);

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/worker/TajoWorker.java
----------------------------------------------------------------------
diff --git a/tajo-core/src/main/java/org/apache/tajo/worker/TajoWorker.java 
b/tajo-core/src/main/java/org/apache/tajo/worker/TajoWorker.java
index 607e7ff..0071a14 100644
--- a/tajo-core/src/main/java/org/apache/tajo/worker/TajoWorker.java
+++ b/tajo-core/src/main/java/org/apache/tajo/worker/TajoWorker.java
@@ -493,7 +493,7 @@ public class TajoWorker extends CompositeService {
         for (Path path : iter) {
           PathData[] items = PathData.expandAsGlob(localFS.makeQualified(new 
Path(path, "*")).toString(), systemConf);
 
-          ArrayList<Path> paths = new ArrayList<Path>();
+          ArrayList<Path> paths = new ArrayList<>();
           for (PathData pd : items) {
             paths.add(pd.path);
           }

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/worker/TaskAttemptContext.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/worker/TaskAttemptContext.java 
b/tajo-core/src/main/java/org/apache/tajo/worker/TaskAttemptContext.java
index 228c32a..485fa03 100644
--- a/tajo-core/src/main/java/org/apache/tajo/worker/TaskAttemptContext.java
+++ b/tajo-core/src/main/java/org/apache/tajo/worker/TaskAttemptContext.java
@@ -106,7 +106,7 @@ public class TaskAttemptContext {
         if (fragmentMap.containsKey(t.getId())) {
           fragmentMap.get(t.getId()).add(t);
         } else {
-          List<FragmentProto> frags = new ArrayList<FragmentProto>();
+          List<FragmentProto> frags = new ArrayList<>();
           frags.add(t);
           fragmentMap.put(t.getId(), frags);
         }
@@ -259,7 +259,7 @@ public class TaskAttemptContext {
       if (fragmentMap.containsKey(t.getTableName())) {
         fragmentMap.get(t.getTableName()).add(t.getProto());
       } else {
-        List<FragmentProto> frags = new ArrayList<FragmentProto>();
+        List<FragmentProto> frags = new ArrayList<>();
         frags.add(t.getProto());
         fragmentMap.put(t.getTableName(), frags);
       }
@@ -273,7 +273,7 @@ public class TaskAttemptContext {
     List<FragmentProto> tableFragments = fragmentMap.get(tableId);
 
     if (tableFragments == null) {
-      tableFragments = new ArrayList<FragmentProto>();
+      tableFragments = new ArrayList<>();
     }
 
     List<Path> paths = fragmentToPath(tableFragments);

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/worker/TaskExecutor.java
----------------------------------------------------------------------
diff --git a/tajo-core/src/main/java/org/apache/tajo/worker/TaskExecutor.java 
b/tajo-core/src/main/java/org/apache/tajo/worker/TaskExecutor.java
index 1d6e2b8..8b9d43f 100644
--- a/tajo-core/src/main/java/org/apache/tajo/worker/TaskExecutor.java
+++ b/tajo-core/src/main/java/org/apache/tajo/worker/TaskExecutor.java
@@ -66,7 +66,7 @@ public class TaskExecutor extends AbstractService implements 
EventHandler<TaskSt
     this.workerContext = workerContext;
     this.allocatedResourceMap = Maps.newConcurrentMap();
     this.runningTasks = new AtomicInteger();
-    this.taskQueue = new LinkedBlockingQueue<Task>();
+    this.taskQueue = new LinkedBlockingQueue<>();
     this.fetcherThreadPoolList = Lists.newArrayList();
   }
 

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/worker/TaskImpl.java
----------------------------------------------------------------------
diff --git a/tajo-core/src/main/java/org/apache/tajo/worker/TaskImpl.java 
b/tajo-core/src/main/java/org/apache/tajo/worker/TaskImpl.java
index a8e874c..a96e3bb 100644
--- a/tajo-core/src/main/java/org/apache/tajo/worker/TaskImpl.java
+++ b/tajo-core/src/main/java/org/apache/tajo/worker/TaskImpl.java
@@ -365,7 +365,7 @@ public class TaskImpl implements Task {
     Collection<String> inputs = Lists.newArrayList(context.getInputTables());
 
     // Get all broadcasted tables
-    Set<String> broadcastTableNames = new HashSet<String>();
+    Set<String> broadcastTableNames = new HashSet<>();
     List<EnforceProperty> broadcasts = 
context.getEnforcer().getEnforceProperties(EnforceType.BROADCAST);
     if (broadcasts != null) {
       for (EnforceProperty eachBroadcast : broadcasts) {
@@ -553,7 +553,7 @@ public class TaskImpl implements Task {
     FileSystem fs = FileSystem.get(c);
     Path tablePath = new Path(file.getAbsolutePath());
 
-    List<FileFragment> listTablets = new ArrayList<FileFragment>();
+    List<FileFragment> listTablets = new ArrayList<>();
     FileFragment tablet;
 
     FileStatus[] fileLists = fs.listStatus(tablePath);

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/worker/TaskManager.java
----------------------------------------------------------------------
diff --git a/tajo-core/src/main/java/org/apache/tajo/worker/TaskManager.java 
b/tajo-core/src/main/java/org/apache/tajo/worker/TaskManager.java
index a0b3f97..e5cf7c9 100644
--- a/tajo-core/src/main/java/org/apache/tajo/worker/TaskManager.java
+++ b/tajo-core/src/main/java/org/apache/tajo/worker/TaskManager.java
@@ -122,7 +122,7 @@ public class TaskManager extends AbstractService implements 
EventHandler<TaskMan
 
       client = RpcClientManager.getInstance().newClient(address, 
QueryMasterProtocol.class, true, rpcParams);
       QueryMasterProtocol.QueryMasterProtocolService.Interface stub = 
client.getStub();
-      CallFuture<ExecutionBlockContextResponse> callback = new 
CallFuture<ExecutionBlockContextResponse>();
+      CallFuture<ExecutionBlockContextResponse> callback = new CallFuture<>();
       stub.getExecutionBlockContext(callback.getController(), request.build(), 
callback);
 
       ExecutionBlockContextResponse contextProto =

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/worker/rule/WorkerRuleProvider.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/worker/rule/WorkerRuleProvider.java 
b/tajo-core/src/main/java/org/apache/tajo/worker/rule/WorkerRuleProvider.java
index 81c2522..1b58c32 100644
--- 
a/tajo-core/src/main/java/org/apache/tajo/worker/rule/WorkerRuleProvider.java
+++ 
b/tajo-core/src/main/java/org/apache/tajo/worker/rule/WorkerRuleProvider.java
@@ -37,7 +37,7 @@ public class WorkerRuleProvider implements 
SelfDiagnosisRuleProvider {
   public List<SelfDiagnosisRule> getDefinedRules() {
     Set<Class> classSet = ClassUtil.findClasses(SelfDiagnosisRule.class, 
         getClass().getPackage().getName());
-    List<SelfDiagnosisRule> ruleList = new 
ArrayList<SelfDiagnosisRule>(classSet.size());
+    List<SelfDiagnosisRule> ruleList = new ArrayList<>(classSet.size());
     
     for (Class<SelfDiagnosisRule> ruleClazz: classSet) {
       try {

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/ws/rs/ClientApplication.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/ws/rs/ClientApplication.java 
b/tajo-core/src/main/java/org/apache/tajo/ws/rs/ClientApplication.java
index b88b8ed..7d7c924 100644
--- a/tajo-core/src/main/java/org/apache/tajo/ws/rs/ClientApplication.java
+++ b/tajo-core/src/main/java/org/apache/tajo/ws/rs/ClientApplication.java
@@ -56,7 +56,7 @@ public class ClientApplication extends Application {
     
     this.secureRandom = new SecureRandom();
     
-    this.queryIdToResultSetCacheIdMap = new ConcurrentHashMap<QueryId, Long>();
+    this.queryIdToResultSetCacheIdMap = new ConcurrentHashMap<>();
     this.queryResultScannerCache = CacheBuilder.newBuilder()
         .concurrencyLevel(4)
         .maximumSize(1000)
@@ -66,7 +66,7 @@ public class ClientApplication extends Application {
 
   @Override
   public Set<Class<?>> getClasses() {
-    Set<Class<?>> classes = new HashSet<Class<?>>();
+    Set<Class<?>> classes = new HashSet<>();
     
     classes.add(SessionsResource.class);
     classes.add(DatabasesResource.class);

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/ws/rs/JerseyResourceDelegateContext.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/ws/rs/JerseyResourceDelegateContext.java
 
b/tajo-core/src/main/java/org/apache/tajo/ws/rs/JerseyResourceDelegateContext.java
index 9f1fb4a..69c4550 100644
--- 
a/tajo-core/src/main/java/org/apache/tajo/ws/rs/JerseyResourceDelegateContext.java
+++ 
b/tajo-core/src/main/java/org/apache/tajo/ws/rs/JerseyResourceDelegateContext.java
@@ -28,7 +28,7 @@ import java.util.concurrent.ConcurrentMap;
 public class JerseyResourceDelegateContext {
 
   private final ConcurrentMap<JerseyResourceDelegateContextKey<?>, Object> 
contextMap =
-      new ConcurrentHashMap<JerseyResourceDelegateContextKey<?>, Object>();
+          new ConcurrentHashMap<>();
   
   /**
    * Add value to Context. If value exists, it will overwrite.

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/ws/rs/JerseyResourceDelegateContextKey.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/ws/rs/JerseyResourceDelegateContextKey.java
 
b/tajo-core/src/main/java/org/apache/tajo/ws/rs/JerseyResourceDelegateContextKey.java
index 3c059d4..b1d759a 100644
--- 
a/tajo-core/src/main/java/org/apache/tajo/ws/rs/JerseyResourceDelegateContextKey.java
+++ 
b/tajo-core/src/main/java/org/apache/tajo/ws/rs/JerseyResourceDelegateContextKey.java
@@ -26,7 +26,7 @@ import javax.ws.rs.core.GenericType;
 public class JerseyResourceDelegateContextKey<T> {
   
   private static final ConcurrentMap<String, 
JerseyResourceDelegateContextKey<?>> keyMap =
-      new ConcurrentHashMap<String, JerseyResourceDelegateContextKey<?>>();
+          new ConcurrentHashMap<>();
   
   private final String name;
   private final Class<T> type;
@@ -43,7 +43,7 @@ public class JerseyResourceDelegateContextKey<T> {
     
     JerseyResourceDelegateContextKey<T> key = 
(JerseyResourceDelegateContextKey<T>) keyMap.get(name);
     if (key == null) {
-      key = new JerseyResourceDelegateContextKey<T>(name, type);
+      key = new JerseyResourceDelegateContextKey<>(name, type);
       keyMap.putIfAbsent(name, key);
     }
     

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/ClusterResource.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/ClusterResource.java 
b/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/ClusterResource.java
index 19d8b28..9311139 100644
--- 
a/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/ClusterResource.java
+++ 
b/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/ClusterResource.java
@@ -100,13 +100,13 @@ public class ClusterResource {
       MasterContext masterContext = context.get(masterContextKey);
       
       Map<Integer, NodeStatus> workerMap = 
masterContext.getResourceManager().getNodes();
-      List<WorkerResponse> workerList = new ArrayList<WorkerResponse>();
+      List<WorkerResponse> workerList = new ArrayList<>();
       
       for (NodeStatus nodeStatus : workerMap.values()) {
         workerList.add(new WorkerResponse(nodeStatus));
       }
       
-      Map<String, List<WorkerResponse>> workerResponseMap = new 
HashMap<String, List<WorkerResponse>>();
+      Map<String, List<WorkerResponse>> workerResponseMap = new HashMap<>();
       workerResponseMap.put(workersName, workerList);
       
       return Response.ok(workerResponseMap).build();

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/DatabasesResource.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/DatabasesResource.java
 
b/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/DatabasesResource.java
index 046e538..5d3c95b 100644
--- 
a/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/DatabasesResource.java
+++ 
b/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/DatabasesResource.java
@@ -105,7 +105,7 @@ public class DatabasesResource {
       MasterContext masterContext = context.get(masterContextKey);
       
       Collection<String> databaseNames = 
masterContext.getCatalog().getAllDatabaseNames();
-      Map<String, Collection<String>> databaseNamesMap = new HashMap<String, 
Collection<String>>();
+      Map<String, Collection<String>> databaseNamesMap = new HashMap<>();
       databaseNamesMap.put(databasesKeyName, databaseNames);
       return Response.ok(databaseNamesMap).build();
     }

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/FunctionsResource.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/FunctionsResource.java
 
b/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/FunctionsResource.java
index ead4b71..871328d 100644
--- 
a/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/FunctionsResource.java
+++ 
b/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/FunctionsResource.java
@@ -89,8 +89,8 @@ public class FunctionsResource {
       
       Collection<FunctionDesc> functionDescriptors = 
masterContext.getCatalog().getFunctions();
       if (functionDescriptors.size() > 0) {
-        List<FunctionSignature> functionSignature = 
-            new ArrayList<FunctionSignature>(functionDescriptors.size());
+        List<FunctionSignature> functionSignature =
+                new ArrayList<>(functionDescriptors.size());
         for (FunctionDesc functionDesc : functionDescriptors) {
           functionSignature.add(functionDesc.getSignature());
         }

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/QueryResource.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/QueryResource.java 
b/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/QueryResource.java
index eb67167..e4cf025 100644
--- a/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/QueryResource.java
+++ b/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/QueryResource.java
@@ -145,8 +145,8 @@ public class QueryResource {
         return ResourcesUtil.createBadRequestResponse(LOG, state + " is not a 
valid query state.");
       }
       
-      Map<String, List<QueryInfo>> queriesMap = new HashMap<String, 
List<QueryInfo>>();
-      List<QueryInfo> queriesInfo = new ArrayList<QueryInfo>();
+      Map<String, List<QueryInfo>> queriesMap = new HashMap<>();
+      List<QueryInfo> queriesInfo = new ArrayList<>();
       
       QueryManager queryManager = masterContext.getQueryJobManager();
       for (QueryInProgress queryInProgress: 
queryManager.getSubmittedQueries()) {
@@ -172,7 +172,7 @@ public class QueryResource {
     }
     
     private List<QueryInfo> selectQueriesInfoByState(List<QueryInfo> 
queriesInfo, TajoProtos.QueryState state) {
-      List<QueryInfo> resultQueriesInfo = new 
ArrayList<QueryInfo>(queriesInfo.size()/2);
+      List<QueryInfo> resultQueriesInfo = new ArrayList<>(queriesInfo.size() / 
2);
       
       for (QueryInfo queryInfo: queriesInfo) {
         if (state.equals(queryInfo.getQueryState())) {
@@ -184,7 +184,7 @@ public class QueryResource {
     }
     
     private List<QueryInfo> selectQueriesInfoByTime(List<QueryInfo> 
queriesInfo, long startTime, long endTime) {
-      List<QueryInfo> resultQueriesInfo = new 
ArrayList<QueryInfo>(queriesInfo.size()/2);
+      List<QueryInfo> resultQueriesInfo = new ArrayList<>(queriesInfo.size() / 
2);
       
       for (QueryInfo queryInfo: queriesInfo) {
         if (queryInfo.getStartTime() > startTime) {

http://git-wip-us.apache.org/repos/asf/tajo/blob/aa699c70/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/SessionsResource.java
----------------------------------------------------------------------
diff --git 
a/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/SessionsResource.java 
b/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/SessionsResource.java
index 8456202..52d8fe7 100644
--- 
a/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/SessionsResource.java
+++ 
b/tajo-core/src/main/java/org/apache/tajo/ws/rs/resources/SessionsResource.java
@@ -267,11 +267,11 @@ public class SessionsResource {
       String sessionId = context.get(sessionIdKey);
 
       try {
-        Map<String, Map<String, String>> variablesMap = new HashMap<String, 
Map<String, String>>();
+        Map<String, Map<String, String>> variablesMap = new HashMap<>();
         variablesMap.put(variablesOutputKeyName,
             masterContext.getSessionManager().getAllVariables(sessionId));
         GenericEntity<Map<String, Map<String, String>>> variablesEntity =
-            new GenericEntity<Map<String, Map<String, String>>>(variablesMap, 
Map.class);
+                new GenericEntity<>(variablesMap, Map.class);
         return Response.ok(variablesEntity).build();
       } catch (InvalidSessionException e) {
         LOG.error("Unable to find a session : " + sessionId);

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