diff --git a/common/src/main/java/org/apache/nemo/common/ir/IRDAGChecker.java b/common/src/main/java/org/apache/nemo/common/ir/IRDAGChecker.java
index 4484505..bdca93c 100644
--- a/common/src/main/java/org/apache/nemo/common/ir/IRDAGChecker.java
+++ b/common/src/main/java/org/apache/nemo/common/ir/IRDAGChecker.java
@@ -230,7 +230,7 @@
       final Optional<Integer> parallelism = v.getPropertyValue(ParallelismProperty.class);
       for (final IREdge inEdge : inEdges) {
         final Optional<Integer> keyRangeListSize = inEdge.getPropertyValue(PartitionSetProperty.class)
-          .map(keyRangeList -> keyRangeList.size());
+          .map(List::size);
         if (parallelism.isPresent() && keyRangeListSize.isPresent() && !parallelism.equals(keyRangeListSize)) {
           return failure("PartitionSet must contain all task offsets required for the dst parallelism",
             v, ParallelismProperty.class, inEdge, PartitionSetProperty.class);
@@ -384,7 +384,7 @@
 
       for (final IRVertex v : irdag.getVertices()) {
         final MutableObject violatingReachableVertex = new MutableObject();
-        v.getPropertyValue(ScheduleGroupProperty.class).ifPresent(startingScheduleGroup -> {
+        v.getPropertyValue(ScheduleGroupProperty.class).ifPresent(startingScheduleGroup ->
           irdag.dfsDo(
             v,
             visited -> {
@@ -394,8 +394,7 @@
               }
             },
             DAGInterface.TraversalOrder.PreOrder,
-            new HashSet<>());
-        });
+            new HashSet<>()));
         if (violatingReachableVertex.getValue() != null) {
           return failure(
             "A reachable vertex with a smaller schedule group ",
@@ -547,8 +546,7 @@
                         final Class... eps) {
     final List<Optional> epsList = Arrays.stream(eps)
       .map(ep -> (Class<VertexExecutionProperty<Serializable>>) ep)
-      .map(ep -> v.getPropertyValue(ep))
-      .collect(Collectors.toList());
+      .map(v::getPropertyValue).collect(Collectors.toList());
     return failure(String.format("%s - [IRVertex %s: %s]", description, v.getId(), epsList.toString()));
   }
 
@@ -557,7 +555,7 @@
                         final Class... eps) {
     final List<Optional> epsList = Arrays.stream(eps)
       .map(ep -> (Class<EdgeExecutionProperty<Serializable>>) ep)
-      .map(ep -> e.getPropertyValue(ep)).collect(Collectors.toList());
+      .map(e::getPropertyValue).collect(Collectors.toList());
     return failure(String.format("%s - [IREdge(%s->%s) %s: %s]",
       description, e.getSrc().getId(), e.getDst().getId(), e.getId(), epsList.toString()));
   }
diff --git a/common/src/test/java/org/apache/nemo/common/DAGTest.java b/common/src/test/java/org/apache/nemo/common/DAGTest.java
index 139edd9..c01fa03 100644
--- a/common/src/test/java/org/apache/nemo/common/DAGTest.java
+++ b/common/src/test/java/org/apache/nemo/common/DAGTest.java
@@ -69,6 +69,7 @@
     assertEquals(1, dag.getOutgoingEdgesOf(new IntegerVertex(4)).size());
     assertEquals(5, dag.getTopologicalSort().size());
 
+
     final List<IntegerVertex> topologicalOrder = dag.getTopologicalSort();
 
     assertEquals(1, topologicalOrder.get(0).getValue());
diff --git a/compiler/optimizer/src/main/java/org/apache/nemo/compiler/optimizer/policy/PolicyImpl.java b/compiler/optimizer/src/main/java/org/apache/nemo/compiler/optimizer/policy/PolicyImpl.java
index 9059891..2c19d4d 100644
--- a/compiler/optimizer/src/main/java/org/apache/nemo/compiler/optimizer/policy/PolicyImpl.java
+++ b/compiler/optimizer/src/main/java/org/apache/nemo/compiler/optimizer/policy/PolicyImpl.java
@@ -81,11 +81,10 @@
         // Apply the pass to the DAG.
         processedDAG = passToApply.apply(dag);
 
-        final boolean advanced = processedDAG.advanceDAGSnapshot((beforePass, afterPass) -> {
+        final boolean advanced = processedDAG.advanceDAGSnapshot((beforePass, afterPass) ->
           // Ensure AnnotatingPass and ReshapingPass functions as intended.
-          return !((passToApply instanceof AnnotatingPass && !checkAnnotatingPass(beforePass, afterPass))
-            || (passToApply instanceof ReshapingPass && !checkReshapingPass(beforePass, afterPass)));
-        });
+          !((passToApply instanceof AnnotatingPass && !checkAnnotatingPass(beforePass, afterPass))
+            || (passToApply instanceof ReshapingPass && !checkReshapingPass(beforePass, afterPass))));
 
         if (!advanced) {
           throw new CompileTimeOptimizationException(passToApply.getClass().getSimpleName()
diff --git a/runtime/executor/src/main/java/org/apache/nemo/runtime/executor/task/DataFetcher.java b/runtime/executor/src/main/java/org/apache/nemo/runtime/executor/task/DataFetcher.java
index 12121c9..7af0885 100644
--- a/runtime/executor/src/main/java/org/apache/nemo/runtime/executor/task/DataFetcher.java
+++ b/runtime/executor/src/main/java/org/apache/nemo/runtime/executor/task/DataFetcher.java
@@ -22,7 +22,6 @@
 import org.apache.nemo.common.ir.vertex.IRVertex;
 
 import java.io.IOException;
-import java.util.NoSuchElementException;
 
 /**
  * An abstraction for fetching data from task-external sources.
@@ -48,7 +47,7 @@
    * @throws IOException                      upon I/O error
    * @throws java.util.NoSuchElementException if no more element is available
    */
-  abstract Object fetchDataElement() throws IOException, NoSuchElementException;
+  abstract Object fetchDataElement() throws IOException;
 
   OutputCollector getOutputCollector() {
     return outputCollector;
diff --git a/runtime/executor/src/main/java/org/apache/nemo/runtime/executor/task/MultiThreadParentTaskDataFetcher.java b/runtime/executor/src/main/java/org/apache/nemo/runtime/executor/task/MultiThreadParentTaskDataFetcher.java
index 4e460f9..12cc9a6 100644
--- a/runtime/executor/src/main/java/org/apache/nemo/runtime/executor/task/MultiThreadParentTaskDataFetcher.java
+++ b/runtime/executor/src/main/java/org/apache/nemo/runtime/executor/task/MultiThreadParentTaskDataFetcher.java
@@ -78,7 +78,7 @@
   }
 
   @Override
-  Object fetchDataElement() throws IOException, NoSuchElementException {
+  Object fetchDataElement() throws IOException {
     if (firstFetch) {
       fetchDataLazily();
       firstFetch = false;