diff --git a/akka-bench-jmh/src/main/scala/akka/actor/ActorCreationBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/actor/ActorCreationBenchmark.scala
index 3dd2b617e5..abd481d463 100644
--- a/akka-bench-jmh/src/main/scala/akka/actor/ActorCreationBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/actor/ActorCreationBenchmark.scala
@@ -34,7 +34,7 @@ class ActorCreationBenchmark {
   }
 
   @TearDown(Level.Trial)
-  def shutdown() {
+  def shutdown():Unit = {
     system.terminate()
     Await.ready(system.whenTerminated, 15.seconds)
   }
diff --git a/akka-bench-jmh/src/main/scala/akka/actor/ForkJoinActorBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/actor/ForkJoinActorBenchmark.scala
index b622830d2b..3a352282c4 100644
--- a/akka-bench-jmh/src/main/scala/akka/actor/ForkJoinActorBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/actor/ForkJoinActorBenchmark.scala
@@ -28,7 +28,7 @@ class ForkJoinActorBenchmark {
   implicit var system: ActorSystem = _
 
   @Setup(Level.Trial)
-  def setup() {
+  def setup():Unit = {
     system = ActorSystem("ForkJoinActorBenchmark", ConfigFactory.parseString(
       s"""| akka {
         |   log-dead-letters = off
@@ -48,7 +48,7 @@ class ForkJoinActorBenchmark {
   }
 
   @TearDown(Level.Trial)
-  def shutdown() {
+  def shutdown():Unit = {
     system.terminate()
     Await.ready(system.whenTerminated, 15.seconds)
   }
@@ -56,7 +56,7 @@ class ForkJoinActorBenchmark {
   @Benchmark
   @Measurement(timeUnit = TimeUnit.MILLISECONDS)
   @OperationsPerInvocation(messages)
-  def pingPong = {
+  def pingPong():Unit = {
     val ping = system.actorOf(Props[ForkJoinActorBenchmark.PingPong])
     val pong = system.actorOf(Props[ForkJoinActorBenchmark.PingPong])
 
@@ -72,7 +72,7 @@ class ForkJoinActorBenchmark {
   @Benchmark
   @Measurement(timeUnit = TimeUnit.MILLISECONDS)
   @OperationsPerInvocation(messages)
-  def floodPipe = {
+  def floodPipe():Unit = {
 
     val end = system.actorOf(Props(classOf[ForkJoinActorBenchmark.Pipe], None))
     val middle = system.actorOf(Props(classOf[ForkJoinActorBenchmark.Pipe], Some(end)))
diff --git a/akka-bench-jmh/src/main/scala/akka/actor/RouterPoolCreationBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/actor/RouterPoolCreationBenchmark.scala
index e3e9538581..1e7d86110c 100644
--- a/akka-bench-jmh/src/main/scala/akka/actor/RouterPoolCreationBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/actor/RouterPoolCreationBenchmark.scala
@@ -26,7 +26,7 @@ class RouterPoolCreationBenchmark {
   var size = 0
 
   @TearDown(Level.Trial)
-  def shutdown() {
+  def shutdown():Unit = {
     system.terminate()
     Await.ready(system.whenTerminated, 15.seconds)
   }
diff --git a/akka-bench-jmh/src/main/scala/akka/actor/ScheduleBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/actor/ScheduleBenchmark.scala
index 84bee09a0f..0d17030901 100644
--- a/akka-bench-jmh/src/main/scala/akka/actor/ScheduleBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/actor/ScheduleBenchmark.scala
@@ -56,13 +56,13 @@ class ScheduleBenchmark {
   var promise: Promise[Any] = _
 
   @Setup(Level.Iteration)
-  def setup() {
+  def setup():Unit =  {
     winner = (to * ratio + 1).toInt
     promise = Promise[Any]()
   }
 
   @TearDown
-  def shutdown() {
+  def shutdown():Unit = {
     system.terminate()
     Await.ready(system.whenTerminated, 15.seconds)
   }
@@ -70,7 +70,7 @@ class ScheduleBenchmark {
   def op(idx: Int) = if (idx == winner) promise.trySuccess(idx) else idx
 
   @Benchmark
-  def oneSchedule = {
+  def oneSchedule():Unit = {
     val aIdx = new AtomicInteger(1)
     val tryWithNext = scheduler.schedule(0.millis, interval) {
       val idx = aIdx.getAndIncrement
@@ -84,7 +84,7 @@ class ScheduleBenchmark {
   }
 
   @Benchmark
-  def multipleScheduleOnce = {
+  def multipleScheduleOnce():Unit = {
     val tryWithNext = (1 to to).foldLeft(0.millis -> List[Cancellable]()) {
       case ((interv, c), idx) ⇒
         (interv + interval, scheduler.scheduleOnce(interv) {
diff --git a/akka-bench-jmh/src/main/scala/akka/actor/StashCreationBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/actor/StashCreationBenchmark.scala
index b4ca986037..bda620c9c0 100644
--- a/akka-bench-jmh/src/main/scala/akka/actor/StashCreationBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/actor/StashCreationBenchmark.scala
@@ -35,7 +35,7 @@ class StashCreationBenchmark {
   val probe = TestProbe()
 
   @TearDown(Level.Trial)
-  def shutdown() {
+  def shutdown():Unit = {
     system.terminate()
     Await.ready(system.whenTerminated, 15.seconds)
   }
diff --git a/akka-bench-jmh/src/main/scala/akka/actor/TellOnlyBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/actor/TellOnlyBenchmark.scala
index 7c0ae2347c..6fe247c86f 100644
--- a/akka-bench-jmh/src/main/scala/akka/actor/TellOnlyBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/actor/TellOnlyBenchmark.scala
@@ -25,7 +25,7 @@ class TellOnlyBenchmark {
   implicit var system: ActorSystem = _
 
   @Setup(Level.Trial)
-  def setup() {
+  def setup():Unit = {
     system = ActorSystem("TellOnlyBenchmark", ConfigFactory.parseString(
       s"""| akka {
           |   log-dead-letters = off
@@ -50,7 +50,7 @@ class TellOnlyBenchmark {
   }
 
   @TearDown(Level.Trial)
-  def shutdown() {
+  def shutdown():Unit = {
     system.terminate()
     Await.ready(system.whenTerminated, 15.seconds)
   }
@@ -59,7 +59,7 @@ class TellOnlyBenchmark {
   var probe: TestProbe = _
 
   @Setup(Level.Iteration)
-  def setupIteration() {
+  def setupIteration():Unit = {
     actor = system.actorOf(Props[TellOnlyBenchmark.Echo].withDispatcher("dropping-dispatcher"))
     probe = TestProbe()
     probe.watch(actor)
@@ -71,7 +71,7 @@ class TellOnlyBenchmark {
   }
 
   @TearDown(Level.Iteration)
-  def shutdownIteration() {
+  def shutdownIteration():Unit = {
     probe.send(actor, flipDrop)
     probe.expectNoMsg(200.millis)
     actor ! stop
@@ -82,7 +82,7 @@ class TellOnlyBenchmark {
 
   @Benchmark
   @OutputTimeUnit(TimeUnit.MICROSECONDS)
-  def tell() = {
+  def tell():Unit = {
     probe.send(actor, message)
   }
 }
@@ -105,7 +105,7 @@ object TellOnlyBenchmark {
   class DroppingMessageQueue extends UnboundedMailbox.MessageQueue {
     @volatile var dropping = false
 
-    override def enqueue(receiver: ActorRef, handle: Envelope) = {
+    override def enqueue(receiver: ActorRef, handle: Envelope):Unit = {
       if (handle.message == flipDrop) dropping = !dropping
       else if (!dropping) super.enqueue(receiver, handle)
     }
diff --git a/akka-bench-jmh/src/main/scala/akka/cluster/ddata/ORSetMergeBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/cluster/ddata/ORSetMergeBenchmark.scala
index 6c56afa12b..a62ea6da6c 100644
--- a/akka-bench-jmh/src/main/scala/akka/cluster/ddata/ORSetMergeBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/cluster/ddata/ORSetMergeBenchmark.scala
@@ -48,7 +48,7 @@ class ORSetMergeBenchmark {
   var elem2: String = _
 
   @Setup(Level.Trial)
-  def setup() {
+  def setup():Unit = {
     set1 = (1 to set1Size).foldLeft(ORSet.empty[String])((s, n) => s.add(nextNode(), "elem" + n))
     addFromSameNode = set1.add(nodeA, "elem" + set1Size + 1).merge(set1)
     addFromOtherNode = set1.add(nodeB, "elem" + set1Size + 1).merge(set1)
diff --git a/akka-bench-jmh/src/main/scala/akka/cluster/ddata/VersionVectorBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/cluster/ddata/VersionVectorBenchmark.scala
index 4e75b8d7f1..6b04e499ce 100644
--- a/akka-bench-jmh/src/main/scala/akka/cluster/ddata/VersionVectorBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/cluster/ddata/VersionVectorBenchmark.scala
@@ -45,7 +45,7 @@ class VersionVectorBenchmark {
   var dot1: VersionVector = _
 
   @Setup(Level.Trial)
-  def setup() {
+  def setup():Unit = {
     vv1 = (1 to size).foldLeft(VersionVector.empty)((vv, n) => vv + nextNode())
     vv2 = vv1 + nextNode()
     vv3 = vv1 + nextNode()
diff --git a/akka-bench-jmh/src/main/scala/akka/http/HttpBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/http/HttpBenchmark.scala
index 5b0138768c..061abd488e 100644
--- a/akka-bench-jmh/src/main/scala/akka/http/HttpBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/http/HttpBenchmark.scala
@@ -38,7 +38,7 @@ class HttpBenchmark {
   var pool: Flow[(HttpRequest, Int), (Try[HttpResponse], Int), _] = _
 
   @Setup
-  def setup() = {
+  def setup():Unit = {
     val route = {
       path("test") {
         get {
@@ -53,21 +53,21 @@ class HttpBenchmark {
   }
 
   @TearDown
-  def shutdown() = {
+  def shutdown():Unit ={
     Await.ready(Http().shutdownAllConnectionPools(), 1.second)
     binding.unbind()
     Await.result(system.terminate(), 5.seconds)
   }
 
   @Benchmark
-  def single_request() = {
+  def single_request():Unit = {
     import system.dispatcher
     val response = Await.result(Http().singleRequest(request), 1.second)
     Await.result(Unmarshal(response.entity).to[String], 1.second)
   }
 
   @Benchmark
-  def single_request_pool() = {
+  def single_request_pool():Unit = {
     import system.dispatcher
     val (response, id) = Await.result(Source.single(HttpRequest(uri = "/test") -> 42).via(pool).runWith(Sink.head), 1.second)
     Await.result(Unmarshal(response.get.entity).to[String], 1.second)
diff --git a/akka-bench-jmh/src/main/scala/akka/persistence/LevelDbBatchingBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/persistence/LevelDbBatchingBenchmark.scala
index 550c5d4b08..239441bbb5 100644
--- a/akka-bench-jmh/src/main/scala/akka/persistence/LevelDbBatchingBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/persistence/LevelDbBatchingBenchmark.scala
@@ -45,7 +45,7 @@ class LevelDbBatchingBenchmark {
   val batch_200 = List.fill(200) { AtomicWrite(PersistentRepr("data", 12, "pa")) }
 
   @Setup(Level.Trial)
-  def setup() {
+  def setup():Unit = {
     sys = ActorSystem("sys")
     deleteStorage(sys)
     SharedLeveldbJournal.setStore(store, sys)
@@ -55,7 +55,7 @@ class LevelDbBatchingBenchmark {
   }
 
   @TearDown(Level.Trial)
-  def tearDown() {
+  def tearDown():Unit = {
     store ! PoisonPill
     Thread.sleep(500)
 
@@ -66,7 +66,7 @@ class LevelDbBatchingBenchmark {
   @Benchmark
   @Measurement(timeUnit = TimeUnit.MICROSECONDS)
   @OperationsPerInvocation(1)
-  def write_1() = {
+  def write_1():Unit = {
     probe.send(store, WriteMessages(batch_1))
     probe.expectMsgType[Any]
   }
@@ -74,7 +74,7 @@ class LevelDbBatchingBenchmark {
   @Benchmark
   @Measurement(timeUnit = TimeUnit.MICROSECONDS)
   @OperationsPerInvocation(10)
-  def writeBatch_10() = {
+  def writeBatch_10():Unit = {
     probe.send(store, WriteMessages(batch_10))
     probe.expectMsgType[Any]
   }
@@ -82,7 +82,7 @@ class LevelDbBatchingBenchmark {
   @Benchmark
   @Measurement(timeUnit = TimeUnit.MICROSECONDS)
   @OperationsPerInvocation(100)
-  def writeBatch_100() = {
+  def writeBatch_100():Unit = {
     probe.send(store, WriteMessages(batch_100))
     probe.expectMsgType[Any]
   }
@@ -90,7 +90,7 @@ class LevelDbBatchingBenchmark {
   @Benchmark
   @Measurement(timeUnit = TimeUnit.MICROSECONDS)
   @OperationsPerInvocation(200)
-  def writeBatch_200() = {
+  def writeBatch_200():Unit = {
     probe.send(store, WriteMessages(batch_200))
     probe.expectMsgType[Any]
   }
diff --git a/akka-bench-jmh/src/main/scala/akka/persistence/PersistenceActorDeferBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/persistence/PersistenceActorDeferBenchmark.scala
index 517ce82528..c7612ce10d 100644
--- a/akka-bench-jmh/src/main/scala/akka/persistence/PersistenceActorDeferBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/persistence/PersistenceActorDeferBenchmark.scala
@@ -43,7 +43,7 @@ class PersistentActorDeferBenchmark {
   val data10k = (1 to 10000).toArray
 
   @Setup
-  def setup() {
+  def setup():Unit = {
     system = ActorSystem("test", config)
 
     probe = TestProbe()(system)
@@ -54,7 +54,7 @@ class PersistentActorDeferBenchmark {
   }
 
   @TearDown
-  def shutdown() {
+  def shutdown():Unit = {
     system.terminate()
     Await.ready(system.whenTerminated, 15.seconds)
 
@@ -63,7 +63,7 @@ class PersistentActorDeferBenchmark {
 
   @Benchmark
   @OperationsPerInvocation(10000)
-  def tell_persistAsync_defer_persistAsync_reply() {
+  def tell_persistAsync_defer_persistAsync_reply():Unit = {
     for (i <- data10k) persistAsync_defer.tell(i, probe.ref)
 
     probe.expectMsg(data10k.last)
@@ -71,7 +71,7 @@ class PersistentActorDeferBenchmark {
 
   @Benchmark
   @OperationsPerInvocation(10000)
-  def tell_persistAsync_defer_persistAsync_replyASAP() {
+  def tell_persistAsync_defer_persistAsync_replyASAP():Unit = {
     for (i <- data10k) persistAsync_defer_replyASAP.tell(i, probe.ref)
 
     probe.expectMsg(data10k.last)
diff --git a/akka-bench-jmh/src/main/scala/akka/persistence/PersistentActorBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/persistence/PersistentActorBenchmark.scala
index 2d5d2395be..de8912d54e 100644
--- a/akka-bench-jmh/src/main/scala/akka/persistence/PersistentActorBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/persistence/PersistentActorBenchmark.scala
@@ -35,7 +35,7 @@ class PersistentActorThroughputBenchmark {
   val data10k = (1 to 10000).toArray
 
   @Setup
-  def setup() {
+  def setup():Unit = {
     system = ActorSystem("test", config)
 
     probe = TestProbe()(system)
@@ -52,7 +52,7 @@ class PersistentActorThroughputBenchmark {
   }
 
   @TearDown
-  def shutdown() {
+  def shutdown():Unit = {
     system.terminate()
     Await.ready(system.whenTerminated, 15.seconds)
 
@@ -61,7 +61,7 @@ class PersistentActorThroughputBenchmark {
 
   @Benchmark
   @OperationsPerInvocation(10000)
-  def actor_normalActor_reply_baseline() {
+  def actor_normalActor_reply_baseline():Unit = {
     for (i <- data10k) actor.tell(i, probe.ref)
 
     probe.expectMsg(data10k.last)
@@ -69,7 +69,7 @@ class PersistentActorThroughputBenchmark {
 
   @Benchmark
   @OperationsPerInvocation(10000)
-  def persistentActor_persist_reply() {
+  def persistentActor_persist_reply():Unit = {
     for (i <- data10k) persistPersistentActor.tell(i, probe.ref)
 
     probe.expectMsg(Evt(data10k.last))
@@ -77,7 +77,7 @@ class PersistentActorThroughputBenchmark {
 
   @Benchmark
   @OperationsPerInvocation(10000)
-  def persistentActor_persistAsync_reply() {
+  def persistentActor_persistAsync_reply():Unit = {
     for (i <- data10k) persistAsync1PersistentActor.tell(i, probe.ref)
 
     probe.expectMsg(Evt(data10k.last))
@@ -85,7 +85,7 @@ class PersistentActorThroughputBenchmark {
 
   @Benchmark
   @OperationsPerInvocation(10000)
-  def persistentActor_noPersist_reply() {
+  def persistentActor_noPersist_reply():Unit = {
     for (i <- data10k) noPersistPersistentActor.tell(i, probe.ref)
 
     probe.expectMsg(Evt(data10k.last))
@@ -93,7 +93,7 @@ class PersistentActorThroughputBenchmark {
 
   @Benchmark
   @OperationsPerInvocation(10000)
-  def persistentActor_persistAsync_replyRightOnCommandReceive() {
+  def persistentActor_persistAsync_replyRightOnCommandReceive():Unit = {
     for (i <- data10k) persistAsyncQuickReplyPersistentActor.tell(i, probe.ref)
 
     probe.expectMsg(Evt(data10k.last))
diff --git a/akka-bench-jmh/src/main/scala/akka/persistence/PersistentActorWithAtLeastOnceDeliveryBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/persistence/PersistentActorWithAtLeastOnceDeliveryBenchmark.scala
index 59c0d453f2..59a300c8ff 100644
--- a/akka-bench-jmh/src/main/scala/akka/persistence/PersistentActorWithAtLeastOnceDeliveryBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/persistence/PersistentActorWithAtLeastOnceDeliveryBenchmark.scala
@@ -36,7 +36,7 @@ class PersistentActorWithAtLeastOnceDeliveryBenchmark {
   val dataCount = 10000
 
   @Setup
-  def setup() {
+  def setup():Unit = {
     system = ActorSystem("PersistentActorWithAtLeastOnceDeliveryBenchmark", config)
 
     probe = TestProbe()(system)
@@ -51,7 +51,7 @@ class PersistentActorWithAtLeastOnceDeliveryBenchmark {
   }
 
   @TearDown
-  def shutdown() {
+  def shutdown():Unit = {
     system.terminate()
     Await.ready(system.whenTerminated, 15.seconds)
 
@@ -60,7 +60,7 @@ class PersistentActorWithAtLeastOnceDeliveryBenchmark {
 
   @Benchmark
   @OperationsPerInvocation(10000)
-  def persistentActor_persistAsync_with_AtLeastOnceDelivery() {
+  def persistentActor_persistAsync_with_AtLeastOnceDelivery():Unit = {
     for (i <- 1 to dataCount)
       persistAsyncPersistentActorWithAtLeastOnceDelivery.tell(i, probe.ref)
     probe.expectMsg(20.seconds, Evt(dataCount))
@@ -68,7 +68,7 @@ class PersistentActorWithAtLeastOnceDeliveryBenchmark {
 
   @Benchmark
   @OperationsPerInvocation(10000)
-  def persistentActor_persist_with_AtLeastOnceDelivery() {
+  def persistentActor_persist_with_AtLeastOnceDelivery():Unit = {
     for (i <- 1 to dataCount)
       persistPersistentActorWithAtLeastOnceDelivery.tell(i, probe.ref)
     probe.expectMsg(2.minutes, Evt(dataCount))
@@ -76,7 +76,7 @@ class PersistentActorWithAtLeastOnceDeliveryBenchmark {
 
   @Benchmark
   @OperationsPerInvocation(10000)
-  def persistentActor_noPersist_with_AtLeastOnceDelivery() {
+  def persistentActor_noPersist_with_AtLeastOnceDelivery():Unit = {
     for (i <- 1 to dataCount)
       noPersistPersistentActorWithAtLeastOnceDelivery.tell(i, probe.ref)
     probe.expectMsg(20.seconds, Evt(dataCount))
diff --git a/akka-bench-jmh/src/main/scala/akka/stream/FlatMapMergeBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/stream/FlatMapMergeBenchmark.scala
index c331f17d9f..8e60d645e9 100644
--- a/akka-bench-jmh/src/main/scala/akka/stream/FlatMapMergeBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/stream/FlatMapMergeBenchmark.scala
@@ -23,14 +23,14 @@ class FlatMapMergeBenchmark {
   val NumberOfElements = 100000
 
   @Param(Array("0", "1", "10"))
-  val NumberOfStreams = 0
+  var NumberOfStreams = 0
 
   var graph: RunnableGraph[Future[Done]] = _
 
   def createSource(count: Int): Graph[SourceShape[Int], NotUsed] = akka.stream.Fusing.aggressive(Source.repeat(1).take(count))
 
   @Setup
-  def setup() {
+  def setup():Unit = {
     val source = NumberOfStreams match {
       // Base line: process NumberOfElements-many elements from a single source without using flatMapMerge
       case 0 => createSource(NumberOfElements)
@@ -43,13 +43,13 @@ class FlatMapMergeBenchmark {
   }
 
   @TearDown
-  def shutdown() {
+  def shutdown():Unit = {
     Await.result(system.terminate(), 5.seconds)
   }
 
   @Benchmark
   @OperationsPerInvocation(100000) // Note: needs to match NumberOfElements.
-  def flat_map_merge_100k_elements() {
+  def flat_map_merge_100k_elements():Unit = {
     Await.result(graph.run(), Duration.Inf)
   }
 }
diff --git a/akka-bench-jmh/src/main/scala/akka/stream/FlowMapBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/stream/FlowMapBenchmark.scala
index 07dff03b89..5e5cf0df3f 100644
--- a/akka-bench-jmh/src/main/scala/akka/stream/FlowMapBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/stream/FlowMapBenchmark.scala
@@ -54,7 +54,7 @@ class FlowMapBenchmark {
   var materializer: ActorMaterializer = _
 
   @Param(Array("true", "false"))
-  val UseGraphStageIdentity = false
+  var UseGraphStageIdentity = false
 
   final val successMarker = Success(1)
   final val successFailure = Success(new Exception)
@@ -63,13 +63,13 @@ class FlowMapBenchmark {
   var flow: Source[Int, NotUsed] = _
 
   @Param(Array("8", "32", "128"))
-  val initialInputBufferSize = 0
+  var initialInputBufferSize = 0
 
   @Param(Array("1", "5", "10"))
-  val numberOfMapOps = 0
+  var numberOfMapOps = 0
 
   @Setup
-  def setup() {
+  def setup():Unit = {
     val settings = ActorMaterializerSettings(system)
       .withInputBuffer(initialInputBufferSize, initialInputBufferSize)
 
@@ -111,13 +111,13 @@ class FlowMapBenchmark {
   }
 
   @TearDown
-  def shutdown() {
+  def shutdown():Unit = {
     Await.result(system.terminate(), 5.seconds)
   }
 
   @Benchmark
   @OperationsPerInvocation(100000)
-  def flow_map_100k_elements() {
+  def flow_map_100k_elements():Unit = {
     val lock = new Lock() // todo rethink what is the most lightweight way to await for a streams completion
     lock.acquire()
 
diff --git a/akka-bench-jmh/src/main/scala/akka/stream/GraphBuilderBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/stream/GraphBuilderBenchmark.scala
index 08e6e8676c..477d9ec149 100644
--- a/akka-bench-jmh/src/main/scala/akka/stream/GraphBuilderBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/stream/GraphBuilderBenchmark.scala
@@ -13,25 +13,25 @@ import org.openjdk.jmh.annotations._
 class GraphBuilderBenchmark {
 
   @Param(Array("1", "10", "100", "1000"))
-  val complexity = 0
+  var complexity = 0
 
   @Benchmark
-  def flow_with_map() {
+  def flow_with_map():Unit = {
     MaterializationBenchmark.flowWithMapBuilder(complexity)
   }
 
   @Benchmark
-  def graph_with_junctions() {
+  def graph_with_junctions():Unit ={
     MaterializationBenchmark.graphWithJunctionsBuilder(complexity)
   }
 
   @Benchmark
-  def graph_with_nested_imports() {
+  def graph_with_nested_imports():Unit = {
     MaterializationBenchmark.graphWithNestedImportsBuilder(complexity)
   }
 
   @Benchmark
-  def graph_with_imported_flow() {
+  def graph_with_imported_flow():Unit = {
     MaterializationBenchmark.graphWithImportedFlowBuilder(complexity)
   }
 }
diff --git a/akka-bench-jmh/src/main/scala/akka/stream/InterpreterBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/stream/InterpreterBenchmark.scala
index fe3580d6f7..afb1ecf472 100644
--- a/akka-bench-jmh/src/main/scala/akka/stream/InterpreterBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/stream/InterpreterBenchmark.scala
@@ -20,11 +20,11 @@ class InterpreterBenchmark {
   final val data100k: Vector[Int] = (1 to 100000).toVector
 
   @Param(Array("1", "5", "10"))
-  val numberOfIds: Int = 0
+  var numberOfIds: Int = 0
 
   @Benchmark
   @OperationsPerInvocation(100000)
-  def graph_interpreter_100k_elements() {
+  def graph_interpreter_100k_elements():Unit = {
     new GraphInterpreterSpecKit {
       new TestSetup {
         val identities = Vector.fill(numberOfIds)(GraphStages.identity[Int])
diff --git a/akka-bench-jmh/src/main/scala/akka/stream/MaterializationBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/stream/MaterializationBenchmark.scala
index 0268f17e17..3addd7cf97 100644
--- a/akka-bench-jmh/src/main/scala/akka/stream/MaterializationBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/stream/MaterializationBenchmark.scala
@@ -88,10 +88,10 @@ class MaterializationBenchmark {
   var graphWithImportedFlow: RunnableGraph[NotUsed] = _
 
   @Param(Array("1", "10", "100", "1000"))
-  val complexity = 0
+  var complexity = 0
 
   @Setup
-  def setup() {
+  def setup():Unit = {
     flowWithMap = flowWithMapBuilder(complexity)
     graphWithJunctions = graphWithJunctionsBuilder(complexity)
     graphWithNestedImports = graphWithNestedImportsBuilder(complexity)
@@ -99,27 +99,23 @@ class MaterializationBenchmark {
   }
 
   @TearDown
-  def shutdown() {
+  def shutdown():Unit = {
     Await.result(system.terminate(), 5.seconds)
   }
 
   @Benchmark
-  def flow_with_map() {
-    flowWithMap.run()
-  }
+  def flow_with_map():Unit = flowWithMap.run()
+
 
   @Benchmark
-  def graph_with_junctions() {
-    graphWithJunctions.run()
-  }
+  def graph_with_junctions():Unit = graphWithJunctions.run()
+
 
   @Benchmark
-  def graph_with_nested_imports() {
-    graphWithNestedImports.run()
-  }
+  def graph_with_nested_imports():Unit = graphWithNestedImports.run()
+
 
   @Benchmark
-  def graph_with_imported_flow() {
-    graphWithImportedFlow.run()
-  }
+  def graph_with_imported_flow():Unit = graphWithImportedFlow.run()
+
 }
diff --git a/akka-bench-jmh/src/main/scala/akka/stream/io/FileSourcesBenchmark.scala b/akka-bench-jmh/src/main/scala/akka/stream/io/FileSourcesBenchmark.scala
index 39b6698ea2..501adbb1ae 100644
--- a/akka-bench-jmh/src/main/scala/akka/stream/io/FileSourcesBenchmark.scala
+++ b/akka-bench-jmh/src/main/scala/akka/stream/io/FileSourcesBenchmark.scala
@@ -43,14 +43,14 @@ class FileSourcesBenchmark {
   }
 
   @Param(Array("2048"))
-  val bufSize = 0
+  var bufSize = 0
 
   var fileChannelSource: Source[ByteString, Future[IOResult]] = _
   var fileInputStreamSource: Source[ByteString, Future[IOResult]] = _
   var ioSourceLinesIterator: Source[ByteString, NotUsed] = _
 
   @Setup
-  def setup() {
+  def setup():Unit = {
     fileChannelSource = FileIO.fromFile(file, bufSize)
     fileInputStreamSource = StreamConverters.fromInputStream(() ⇒ new FileInputStream(file), bufSize)
     ioSourceLinesIterator = Source.fromIterator(() ⇒ scala.io.Source.fromFile(file).getLines()).map(ByteString(_))
@@ -62,26 +62,26 @@ class FileSourcesBenchmark {
   }
 
   @TearDown
-  def shutdown() {
+  def shutdown():Unit = {
     Await.result(system.terminate(), Duration.Inf)
   }
 
   @Benchmark
-  def fileChannel() = {
+  def fileChannel():Unit = {
     val h = fileChannelSource.to(Sink.ignore).run()
 
     Await.result(h, 30.seconds)
   }
 
   @Benchmark
-  def fileChannel_noReadAhead() = {
+  def fileChannel_noReadAhead():Unit = {
     val h = fileChannelSource.withAttributes(Attributes.inputBuffer(1, 1)).to(Sink.ignore).run()
 
     Await.result(h, 30.seconds)
   }
 
   @Benchmark
-  def inputStream() = {
+  def inputStream():Unit = {
     val h = fileInputStreamSource.to(Sink.ignore).run()
 
     Await.result(h, 30.seconds)
@@ -93,7 +93,7 @@ class FileSourcesBenchmark {
    * FileSourcesBenchmark.naive_ioSourceLinesIterator  avgt   20  7067.944 ± 1341.847  ms/op
    */
   @Benchmark
-  def naive_ioSourceLinesIterator() = {
+  def naive_ioSourceLinesIterator():Unit = {
     val p = Promise[Done]()
     ioSourceLinesIterator.to(Sink.onComplete(p.complete(_))).run()