diff --git a/akka-stream-tests/src/test/java/akka/stream/javadsl/AttributesTest.java b/akka-stream-tests/src/test/java/akka/stream/javadsl/AttributesTest.java
index 54e9d8c4ec..33332a6cb2 100644
--- a/akka-stream-tests/src/test/java/akka/stream/javadsl/AttributesTest.java
+++ b/akka-stream-tests/src/test/java/akka/stream/javadsl/AttributesTest.java
@@ -5,6 +5,8 @@ package akka.stream.javadsl;
 
 import static org.junit.Assert.assertEquals;
 import java.util.Arrays;
+import java.util.Collections;
+
 import org.junit.Test;
 
 import akka.stream.Attributes;
@@ -22,7 +24,7 @@ public class AttributesTest {
       Arrays.asList(new Attributes.Name("a"), new Attributes.Name("b")),
       attributes.getAttributeList(Attributes.Name.class));
     assertEquals(
-        Arrays.asList(new Attributes.InputBuffer(1, 2)),
+        Collections.singletonList(new Attributes.InputBuffer(1, 2)),
         attributes.getAttributeList(Attributes.InputBuffer.class));
   }
   
diff --git a/akka-stream-tests/src/test/java/akka/stream/javadsl/BidiFlowTest.java b/akka-stream-tests/src/test/java/akka/stream/javadsl/BidiFlowTest.java
index 5fac956e12..5dc2b093b8 100644
--- a/akka-stream-tests/src/test/java/akka/stream/javadsl/BidiFlowTest.java
+++ b/akka-stream-tests/src/test/java/akka/stream/javadsl/BidiFlowTest.java
@@ -263,7 +263,7 @@ public class BidiFlowTest extends StreamTest {
     final Future<List<Long>> r = result.second();
     assertEquals((Integer) 1, Await.result(l, oneSec));
     assertEquals((Integer) 42, Await.result(m, oneSec));
-    final Long[] rr = Await.result(r, oneSec).toArray(new Long[0]);
+    final Long[] rr = Await.result(r, oneSec).toArray(new Long[2]);
     Arrays.sort(rr);
     assertArrayEquals(new Long[] { 3L, 12L }, rr);
   }
diff --git a/akka-stream-tests/src/test/java/akka/stream/javadsl/FlowGraphTest.java b/akka-stream-tests/src/test/java/akka/stream/javadsl/FlowGraphTest.java
index 18d072930a..72d1a1ae87 100644
--- a/akka-stream-tests/src/test/java/akka/stream/javadsl/FlowGraphTest.java
+++ b/akka-stream-tests/src/test/java/akka/stream/javadsl/FlowGraphTest.java
@@ -3,8 +3,6 @@
  */
 package akka.stream.javadsl;
 
-import akka.actor.ActorRef;
-import akka.dispatch.japi;
 import akka.japi.Pair;
 import akka.pattern.Patterns;
 import akka.japi.tuple.Tuple4;
@@ -63,7 +61,7 @@ public class FlowGraphTest extends StreamTest {
     final Flow<String, String, BoxedUnit> f2 =
         Flow.of(String.class).transform(FlowGraphTest.this.<String> op()).named("f2");
     @SuppressWarnings("unused")
-    final Flow<String, String, BoxedUnit> f3 = 
+    final Flow<String, String, BoxedUnit> f3 =
         Flow.of(String.class).transform(FlowGraphTest.this.<String> op()).named("f3");
 
     final Source<String, BoxedUnit> in1 = Source.from(Arrays.asList("a", "b", "c"));
@@ -282,6 +280,7 @@ public class FlowGraphTest extends StreamTest {
 
   @Test
   public void mustBeAbleToUseMatValue() throws Exception {
+    @SuppressWarnings("unused")
     final Source<Integer, BoxedUnit> in1 = Source.single(1);
     final TestProbe probe = TestProbe.apply(system);
 
diff --git a/akka-stream-tests/src/test/scala/akka/stream/actor/ActorPublisherSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/actor/ActorPublisherSpec.scala
index af3e7e75cc..4343b1f061 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/actor/ActorPublisherSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/actor/ActorPublisherSpec.scala
@@ -168,8 +168,8 @@ class ActorPublisherSpec extends AkkaSpec(ActorPublisherSpec.config) with Implic
       val s = TestSubscriber.manualProbe[String]()
       ActorPublisher[String](ref).subscribe(s)
       ref ! Err("wrong")
-      s.expectSubscription
-      s.expectError.getMessage should be("wrong")
+      s.expectSubscription()
+      s.expectError().getMessage should be("wrong")
     }
 
     "not terminate after signalling onError" in {
@@ -177,10 +177,10 @@ class ActorPublisherSpec extends AkkaSpec(ActorPublisherSpec.config) with Implic
       val ref = system.actorOf(testPublisherProps(probe.ref))
       val s = TestSubscriber.manualProbe[String]()
       ActorPublisher[String](ref).subscribe(s)
-      s.expectSubscription
+      s.expectSubscription()
       probe.watch(ref)
       ref ! Err("wrong")
-      s.expectError.getMessage should be("wrong")
+      s.expectError().getMessage should be("wrong")
       probe.expectNoMsg(200.millis)
     }
 
@@ -189,10 +189,10 @@ class ActorPublisherSpec extends AkkaSpec(ActorPublisherSpec.config) with Implic
       val ref = system.actorOf(testPublisherProps(probe.ref))
       val s = TestSubscriber.manualProbe[String]()
       ActorPublisher[String](ref).subscribe(s)
-      s.expectSubscription
+      s.expectSubscription()
       probe.watch(ref)
       ref ! ErrThenStop("wrong")
-      s.expectError.getMessage should be("wrong")
+      s.expectError().getMessage should be("wrong")
       probe.expectTerminated(ref, 3.seconds)
     }
 
@@ -202,7 +202,7 @@ class ActorPublisherSpec extends AkkaSpec(ActorPublisherSpec.config) with Implic
       ref ! Err("early err")
       val s = TestSubscriber.manualProbe[String]()
       ActorPublisher[String](ref).subscribe(s)
-      s.expectSubscriptionAndError.getMessage should be("early err")
+      s.expectSubscriptionAndError().getMessage should be("early err")
     }
 
     "drop onNext elements after cancel" in {
@@ -246,7 +246,7 @@ class ActorPublisherSpec extends AkkaSpec(ActorPublisherSpec.config) with Implic
       ref ! Produce("elem-1")
       ref ! Complete
       s.expectNext("elem-1")
-      s.expectComplete
+      s.expectComplete()
     }
 
     "not terminate after signalling onComplete" in {
@@ -254,14 +254,14 @@ class ActorPublisherSpec extends AkkaSpec(ActorPublisherSpec.config) with Implic
       val ref = system.actorOf(testPublisherProps(probe.ref))
       val s = TestSubscriber.manualProbe[String]()
       ActorPublisher[String](ref).subscribe(s)
-      val sub = s.expectSubscription
+      val sub = s.expectSubscription()
       sub.request(3)
       probe.expectMsg(TotalDemand(3))
       probe.watch(ref)
       ref ! Produce("elem-1")
       ref ! Complete
       s.expectNext("elem-1")
-      s.expectComplete
+      s.expectComplete()
       probe.expectNoMsg(200.millis)
     }
 
@@ -270,14 +270,14 @@ class ActorPublisherSpec extends AkkaSpec(ActorPublisherSpec.config) with Implic
       val ref = system.actorOf(testPublisherProps(probe.ref))
       val s = TestSubscriber.manualProbe[String]()
       ActorPublisher[String](ref).subscribe(s)
-      val sub = s.expectSubscription
+      val sub = s.expectSubscription()
       sub.request(3)
       probe.expectMsg(TotalDemand(3))
       probe.watch(ref)
       ref ! Produce("elem-1")
       ref ! CompleteThenStop
       s.expectNext("elem-1")
-      s.expectComplete
+      s.expectComplete()
       probe.expectTerminated(ref, 3.seconds)
     }
 
@@ -287,7 +287,7 @@ class ActorPublisherSpec extends AkkaSpec(ActorPublisherSpec.config) with Implic
       ref ! Complete
       val s = TestSubscriber.manualProbe[String]()
       ActorPublisher[String](ref).subscribe(s)
-      s.expectSubscriptionAndComplete
+      s.expectSubscriptionAndComplete()
     }
 
     "only allow one subscriber" in {
@@ -295,10 +295,10 @@ class ActorPublisherSpec extends AkkaSpec(ActorPublisherSpec.config) with Implic
       val ref = system.actorOf(testPublisherProps(probe.ref))
       val s = TestSubscriber.manualProbe[String]()
       ActorPublisher[String](ref).subscribe(s)
-      s.expectSubscription
+      s.expectSubscription()
       val s2 = TestSubscriber.manualProbe[String]()
       ActorPublisher[String](ref).subscribe(s2)
-      s2.expectSubscriptionAndError.getClass should be(classOf[IllegalStateException])
+      s2.expectSubscriptionAndError().getClass should be(classOf[IllegalStateException])
     }
 
     "signal onCompete when actor is stopped" in {
@@ -306,9 +306,9 @@ class ActorPublisherSpec extends AkkaSpec(ActorPublisherSpec.config) with Implic
       val ref = system.actorOf(testPublisherProps(probe.ref))
       val s = TestSubscriber.manualProbe[String]()
       ActorPublisher[String](ref).subscribe(s)
-      s.expectSubscription
+      s.expectSubscription()
       ref ! PoisonPill
-      s.expectComplete
+      s.expectComplete()
     }
 
     "work together with Flow and ActorSubscriber" in {
diff --git a/akka-stream-tests/src/test/scala/akka/stream/impl/StreamLayoutSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/impl/StreamLayoutSpec.scala
index ae66bd5c6a..bd9b5b25d8 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/impl/StreamLayoutSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/impl/StreamLayoutSpec.scala
@@ -212,7 +212,7 @@ class StreamLayoutSpec extends AkkaSpec {
 
     def getAllAtomic(module: Module): Set[Module] = {
       val (atomics, composites) = module.subModules.partition(_.isAtomic)
-      atomics ++ composites.map(getAllAtomic).flatten
+      atomics ++ composites.flatMap(getAllAtomic)
     }
 
     val allAtomic = getAllAtomic(topLevel)
diff --git a/akka-stream-tests/src/test/scala/akka/stream/io/FramingSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/io/FramingSpec.scala
index 560fcd7aa3..34ca9fe8ae 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/io/FramingSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/io/FramingSpec.scala
@@ -67,7 +67,7 @@ class FramingSpec extends AkkaSpec {
         .named("lineFraming")
 
     def completeTestSequences(delimiter: ByteString): immutable.Iterable[ByteString] =
-      for (prefix ← 0 until delimiter.size; s ← baseTestSequences)
+      for (prefix ← delimiter.indices; s ← baseTestSequences)
         yield delimiter.take(prefix) ++ s
 
     "work with various delimiters and test sequences" in {
diff --git a/akka-stream-tests/src/test/scala/akka/stream/io/TcpSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/io/TcpSpec.scala
index 00a0899095..297329f465 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/io/TcpSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/io/TcpSpec.scala
@@ -340,8 +340,6 @@ class TcpSpec extends AkkaSpec("akka.io.tcp.windows-connection-abort-workaround-
     }
 
     "properly full-close if requested" in assertAllStagesStopped {
-      import system.dispatcher
-
       val serverAddress = temporaryServerAddress()
       val writeButIgnoreRead: Flow[ByteString, ByteString, Unit] =
         Flow.wrap(Sink.ignore, Source.single(ByteString("Early response")))(Keep.right)
@@ -362,8 +360,6 @@ class TcpSpec extends AkkaSpec("akka.io.tcp.windows-connection-abort-workaround-
     }
 
     "Echo should work even if server is in full close mode" in {
-      import system.dispatcher
-
       val serverAddress = temporaryServerAddress()
 
       val binding =
diff --git a/akka-stream-tests/src/test/scala/akka/stream/io/TlsSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/io/TlsSpec.scala
index 1c24fc6815..949cb77b9f 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/io/TlsSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/io/TlsSpec.scala
@@ -1,6 +1,5 @@
 package akka.stream.io
 
-import java.net.InetSocketAddress
 import java.security.KeyStore
 import java.security.SecureRandom
 import java.util.concurrent.TimeoutException
@@ -15,7 +14,6 @@ import akka.actor.ActorSystem
 import akka.pattern.{ after ⇒ later }
 import akka.stream.ActorMaterializer
 import akka.stream.scaladsl._
-import akka.stream.scaladsl.FlowGraph.Implicits._
 import akka.stream.stage._
 import akka.stream.testkit._
 import akka.stream.testkit.Utils._
@@ -60,7 +58,7 @@ object TlsSpec {
     private var last: ByteString = _
 
     override def preStart(ctx: AsyncContext[ByteString, Unit]) = {
-      val cb = ctx.getAsyncCallback()
+      val cb = ctx.getAsyncCallback
       system.scheduler.scheduleOnce(duration)(cb.invoke(()))(system.dispatcher)
     }
 
diff --git a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowAppendSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowAppendSpec.scala
index 62d43355d0..f4f7f7bba2 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowAppendSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowAppendSpec.scala
@@ -45,7 +45,7 @@ class FlowAppendSpec extends AkkaSpec with River {
 
 trait River { self: Matchers ⇒
 
-  val elements = (1 to 10)
+  val elements = 1 to 10
   val otherFlow = Flow[Int].map(_.toString)
 
   def riverOf[T](flowConstructor: Subscriber[T] ⇒ Unit)(implicit system: ActorSystem) = {
diff --git a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowExpandSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowExpandSpec.scala
index f9d68afa0a..5dbedeacd3 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowExpandSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowExpandSpec.scala
@@ -79,7 +79,7 @@ class FlowExpandSpec extends AkkaSpec {
         .expand(seed = i ⇒ i)(extrapolate = i ⇒ (i, i))
         .runFold(Set.empty[Int])(_ + _)
 
-      Await.result(future, 10.seconds) should contain theSameElementsAs ((1 to 100).toSet)
+      Await.result(future, 10.seconds) should contain theSameElementsAs (1 to 100).toSet
     }
 
     "backpressure publisher when subscriber is slower" in {
diff --git a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowFoldSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowFoldSpec.scala
index c20718261f..fe8a92390c 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowFoldSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowFoldSpec.scala
@@ -6,7 +6,7 @@ package akka.stream.scaladsl
 import scala.concurrent.Await
 import scala.util.control.NoStackTrace
 
-import akka.stream.{ OverflowStrategy, ActorMaterializer }
+import akka.stream.ActorMaterializer
 import akka.stream.testkit.AkkaSpec
 import akka.stream.testkit.Utils._
 import scala.concurrent.duration._
@@ -16,7 +16,7 @@ class FlowFoldSpec extends AkkaSpec {
 
   "A Fold" must {
     val input = 1 to 100
-    val expected = input.fold(0)(_ + _)
+    val expected = input.sum
     val inputSource = Source(input).filter(_ ⇒ true).map(identity)
     val foldSource = inputSource.fold[Int](0)(_ + _).filter(_ ⇒ true).map(identity)
     val foldFlow = Flow[Int].filter(_ ⇒ true).map(identity).fold(0)(_ + _).filter(_ ⇒ true).map(identity)
diff --git a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowForeachSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowForeachSpec.scala
index d534ff3077..54c22583e8 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowForeachSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowForeachSpec.scala
@@ -39,11 +39,11 @@ class FlowForeachSpec extends AkkaSpec {
       Source(p).runForeach(testActor ! _) onFailure {
         case ex ⇒ testActor ! ex
       }
-      val proc = p.expectSubscription
+      val proc = p.expectSubscription()
       proc.expectRequest()
-      val ex = new RuntimeException("ex") with NoStackTrace
-      proc.sendError(ex)
-      expectMsg(ex)
+      val rte = new RuntimeException("ex") with NoStackTrace
+      proc.sendError(rte)
+      expectMsg(rte)
     }
 
     "complete future with failure when function throws" in assertAllStagesStopped {
diff --git a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowGroupedSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowGroupedSpec.scala
index d741e74f73..8a1d15c2a2 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowGroupedSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowGroupedSpec.scala
@@ -28,7 +28,7 @@ class FlowGroupedSpec extends AkkaSpec with ScriptedTest {
 
     "group with rest" in {
       val testLen = random.nextInt(1, 16)
-      def script = Script((TestConfig.RandomTestRange.map { _ ⇒ randomTest(testLen) } :+ randomTest(1)): _*)
+      def script = Script(TestConfig.RandomTestRange.map { _ ⇒ randomTest(testLen) } :+ randomTest(1): _*)
       TestConfig.RandomTestRange foreach (_ ⇒ runScript(script, settings)(_.grouped(testLen)))
     }
 
diff --git a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowIteratorSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowIteratorSpec.scala
index f9503559b6..0c495b6fe4 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowIteratorSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowIteratorSpec.scala
@@ -39,7 +39,7 @@ class FlowIterableSpec extends AbstractFlowIteratorSpec {
     c.expectNext(1)
     c.expectNoMsg(100.millis)
     sub.request(2)
-    c.expectError.getMessage should be("not two")
+    c.expectError().getMessage should be("not two")
     sub.request(2)
     c.expectNoMsg(100.millis)
   }
diff --git a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowMapAsyncSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowMapAsyncSpec.scala
index 57c0d90e32..ecce6e93fd 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowMapAsyncSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowMapAsyncSpec.scala
@@ -28,7 +28,7 @@ object FlowMapAsyncSpec {
 
     override def onPush(elem: In, ctx: AsyncContext[Out, Try[Out]]) = {
       val future = f(elem)
-      val cb = ctx.getAsyncCallback()
+      val cb = ctx.getAsyncCallback
       future.onComplete(cb.invoke)
       ctx.holdUpstream()
     }
@@ -132,7 +132,7 @@ class FlowMapAsyncSpec extends AkkaSpec {
       }).to(Sink(c)).run()
       val sub = c.expectSubscription()
       sub.request(10)
-      c.expectError.getMessage should be("err1")
+      c.expectError().getMessage should be("err1")
       latch.countDown()
     }
 
@@ -151,7 +151,7 @@ class FlowMapAsyncSpec extends AkkaSpec {
         to(Sink(c)).run()
       val sub = c.expectSubscription()
       sub.request(10)
-      c.expectError.getMessage should be("err2")
+      c.expectError().getMessage should be("err2")
       latch.countDown()
     }
 
@@ -216,7 +216,7 @@ class FlowMapAsyncSpec extends AkkaSpec {
       val p = Source(List("a", "b")).mapAsync(4)(elem ⇒ Future.successful(null)).to(Sink(c)).run()
       val sub = c.expectSubscription()
       sub.request(10)
-      c.expectError.getMessage should be(ReactiveStreamsCompliance.ElementMustNotBeNullMsg)
+      c.expectError().getMessage should be(ReactiveStreamsCompliance.ElementMustNotBeNullMsg)
     }
 
     "resume when future is completed with null" in {
diff --git a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowSectionSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowSectionSpec.scala
index 4c431cc762..c12b6f19b3 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowSectionSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowSectionSpec.scala
@@ -78,8 +78,8 @@ class FlowSectionSpec extends AkkaSpec(FlowSectionSpec.config) {
       //FIXME: Flow has no simple toString anymore
       pending
       val n = "Uppercase reverser"
-      val f1 = Flow[String].map(_.toLowerCase())
-      val f2 = Flow[String].map(_.toUpperCase).map(_.reverse).named(n).map(_.toLowerCase())
+      val f1 = Flow[String].map(_.toLowerCase)
+      val f2 = Flow[String].map(_.toUpperCase).map(_.reverse).named(n).map(_.toLowerCase)
 
       f1.via(f2).toString should include(n)
     }
diff --git a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowSpec.scala
index 9adaba3d36..17c5eac49a 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowSpec.scala
@@ -160,12 +160,12 @@ class FlowSpec extends AkkaSpec(ConfigFactory.parseString("akka.actor.debug.rece
       val source: Publisher[String] = Source(List("1", "2", "3")).runWith(Sink.publisher)
       source.subscribe(flowIn)
 
-      val sub1 = c1.expectSubscription
+      val sub1 = c1.expectSubscription()
       sub1.request(3)
       c1.expectNext("1")
       c1.expectNext("2")
       c1.expectNext("3")
-      c1.expectComplete
+      c1.expectComplete()
     }
 
     "materialize into Publisher/Subscriber and transformation processor" in {
@@ -174,7 +174,7 @@ class FlowSpec extends AkkaSpec(ConfigFactory.parseString("akka.actor.debug.rece
 
       val c1 = TestSubscriber.manualProbe[String]()
       flowOut.subscribe(c1)
-      val sub1 = c1.expectSubscription
+      val sub1 = c1.expectSubscription()
       sub1.request(3)
       c1.expectNoMsg(200.millis)
 
@@ -184,7 +184,7 @@ class FlowSpec extends AkkaSpec(ConfigFactory.parseString("akka.actor.debug.rece
       c1.expectNext("1")
       c1.expectNext("2")
       c1.expectNext("3")
-      c1.expectComplete
+      c1.expectComplete()
     }
 
     "materialize into Publisher/Subscriber and multiple transformation processors" in {
@@ -193,7 +193,7 @@ class FlowSpec extends AkkaSpec(ConfigFactory.parseString("akka.actor.debug.rece
 
       val c1 = TestSubscriber.manualProbe[String]()
       flowOut.subscribe(c1)
-      val sub1 = c1.expectSubscription
+      val sub1 = c1.expectSubscription()
       sub1.request(3)
       c1.expectNoMsg(200.millis)
 
@@ -203,7 +203,7 @@ class FlowSpec extends AkkaSpec(ConfigFactory.parseString("akka.actor.debug.rece
       c1.expectNext("elem-1")
       c1.expectNext("elem-2")
       c1.expectNext("elem-3")
-      c1.expectComplete
+      c1.expectComplete()
     }
 
     "subscribe Subscriber" in {
@@ -213,12 +213,12 @@ class FlowSpec extends AkkaSpec(ConfigFactory.parseString("akka.actor.debug.rece
       val publisher: Publisher[String] = Source(List("1", "2", "3")).runWith(Sink.publisher)
       Source(publisher).to(sink).run()
 
-      val sub1 = c1.expectSubscription
+      val sub1 = c1.expectSubscription()
       sub1.request(3)
       c1.expectNext("1")
       c1.expectNext("2")
       c1.expectNext("3")
-      c1.expectComplete
+      c1.expectComplete()
     }
 
     "perform transformation operation" in {
@@ -239,12 +239,12 @@ class FlowSpec extends AkkaSpec(ConfigFactory.parseString("akka.actor.debug.rece
       val publisher: Publisher[Int] = Source(List(1, 2, 3)).runWith(Sink.publisher)
       Source(publisher).to(sink).run()
 
-      val sub1 = c1.expectSubscription
+      val sub1 = c1.expectSubscription()
       sub1.request(3)
       c1.expectNext("1")
       c1.expectNext("2")
       c1.expectNext("3")
-      c1.expectComplete
+      c1.expectComplete()
     }
 
     "be materializable several times with fanout publisher" in assertAllStagesStopped {
@@ -258,26 +258,26 @@ class FlowSpec extends AkkaSpec(ConfigFactory.parseString("akka.actor.debug.rece
       p2.subscribe(s2)
       p2.subscribe(s3)
 
-      val sub1 = s1.expectSubscription
-      val sub2 = s2.expectSubscription
-      val sub3 = s3.expectSubscription
+      val sub1 = s1.expectSubscription()
+      val sub2 = s2.expectSubscription()
+      val sub3 = s3.expectSubscription()
 
       sub1.request(3)
       s1.expectNext("1")
       s1.expectNext("2")
       s1.expectNext("3")
-      s1.expectComplete
+      s1.expectComplete()
 
       sub2.request(3)
       sub3.request(3)
       s2.expectNext("1")
       s2.expectNext("2")
       s2.expectNext("3")
-      s2.expectComplete
+      s2.expectComplete()
       s3.expectNext("1")
       s3.expectNext("2")
       s3.expectNext("3")
-      s3.expectComplete
+      s3.expectComplete()
     }
 
     "be covariant" in {
diff --git a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/HeadSinkSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/HeadSinkSpec.scala
index 981f61ee44..52c3516b57 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/HeadSinkSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/HeadSinkSpec.scala
@@ -27,7 +27,7 @@ class HeadSinkSpec extends AkkaSpec with ScriptedTest {
     "yield the first value" in assertAllStagesStopped {
       val p = TestPublisher.manualProbe[Int]()
       val f: Future[Int] = Source(p).map(identity).runWith(Sink.head)
-      val proc = p.expectSubscription
+      val proc = p.expectSubscription()
       proc.expectRequest()
       proc.sendNext(42)
       Await.result(f, 100.millis) should be(42)
@@ -41,7 +41,7 @@ class HeadSinkSpec extends AkkaSpec with ScriptedTest {
       val (subscriber, future) = s.toMat(f)(Keep.both).run()
 
       p.subscribe(subscriber)
-      val proc = p.expectSubscription
+      val proc = p.expectSubscription()
       proc.expectRequest()
       proc.sendNext(42)
       Await.result(future, 100.millis) should be(42)
@@ -51,7 +51,7 @@ class HeadSinkSpec extends AkkaSpec with ScriptedTest {
     "yield the first error" in assertAllStagesStopped {
       val p = TestPublisher.manualProbe[Int]()
       val f = Source(p).runWith(Sink.head)
-      val proc = p.expectSubscription
+      val proc = p.expectSubscription()
       proc.expectRequest()
       val ex = new RuntimeException("ex")
       proc.sendError(ex)
@@ -62,12 +62,12 @@ class HeadSinkSpec extends AkkaSpec with ScriptedTest {
     "yield NoSuchElementExcption for empty stream" in assertAllStagesStopped {
       val p = TestPublisher.manualProbe[Int]()
       val f = Source(p).runWith(Sink.head)
-      val proc = p.expectSubscription
+      val proc = p.expectSubscription()
       proc.expectRequest()
       proc.sendComplete()
       Await.ready(f, 100.millis)
       f.value.get match {
-        case Failure(e: NoSuchElementException) ⇒ e.getMessage() should be("empty stream")
+        case Failure(e: NoSuchElementException) ⇒ e.getMessage should be("empty stream")
         case x                                  ⇒ fail("expected NoSuchElementException, got " + x)
       }
     }
diff --git a/akka-stream/src/main/scala/akka/stream/actor/ActorPublisher.scala b/akka-stream/src/main/scala/akka/stream/actor/ActorPublisher.scala
index 546d1de89a..5dadcea25d 100644
--- a/akka-stream/src/main/scala/akka/stream/actor/ActorPublisher.scala
+++ b/akka-stream/src/main/scala/akka/stream/actor/ActorPublisher.scala
@@ -174,7 +174,7 @@ trait ActorPublisher[T] extends Actor {
    * otherwise `onNext` will throw `IllegalStateException`.
    */
   def onNext(element: T): Unit = lifecycleState match {
-    case Active | PreSubscriber ⇒
+    case Active | PreSubscriber | CompleteThenStop ⇒
       if (demand > 0) {
         demand -= 1
         tryOnNext(subscriber, element)
@@ -193,7 +193,7 @@ trait ActorPublisher[T] extends Actor {
    * call [[#onNext]], [[#onError]] and [[#onComplete]].
    */
   def onComplete(): Unit = lifecycleState match {
-    case Active | PreSubscriber ⇒
+    case Active | PreSubscriber | CompleteThenStop ⇒
       lifecycleState = Completed
       if (subscriber ne null) // otherwise onComplete will be called when the subscription arrives
         try tryOnComplete(subscriber) finally subscriber = null
@@ -226,8 +226,8 @@ trait ActorPublisher[T] extends Actor {
    * call [[#onNext]], [[#onError]] and [[#onComplete]].
    */
   def onError(cause: Throwable): Unit = lifecycleState match {
-    case Active | PreSubscriber ⇒
-      lifecycleState = ErrorEmitted(cause, false)
+    case Active | PreSubscriber | CompleteThenStop ⇒
+      lifecycleState = ErrorEmitted(cause, stop = false)
       if (subscriber ne null) // otherwise onError will be called when the subscription arrives
         try tryOnError(subscriber, cause) finally subscriber = null
     case _: ErrorEmitted ⇒
diff --git a/akka-stream/src/main/scala/akka/stream/actor/ActorSubscriber.scala b/akka-stream/src/main/scala/akka/stream/actor/ActorSubscriber.scala
index 1f5ab8d933..7ea07d308e 100644
--- a/akka-stream/src/main/scala/akka/stream/actor/ActorSubscriber.scala
+++ b/akka-stream/src/main/scala/akka/stream/actor/ActorSubscriber.scala
@@ -310,7 +310,7 @@ private[akka] final class ActorSubscriberImpl[T](val impl: ActorRef) extends Sub
 private[akka] object ActorSubscriberState extends ExtensionId[ActorSubscriberState] with ExtensionIdProvider {
   override def get(system: ActorSystem): ActorSubscriberState = super.get(system)
 
-  override def lookup = ActorSubscriberState
+  override def lookup() = ActorSubscriberState
 
   override def createExtension(system: ExtendedActorSystem): ActorSubscriberState =
     new ActorSubscriberState
diff --git a/akka-stream/src/main/scala/akka/stream/impl/ActorMaterializerImpl.scala b/akka-stream/src/main/scala/akka/stream/impl/ActorMaterializerImpl.scala
index b95c808801..c14b759d9a 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/ActorMaterializerImpl.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/ActorMaterializerImpl.scala
@@ -15,12 +15,9 @@ import akka.stream.impl.Junctions._
 import akka.stream.impl.StreamLayout.Module
 import akka.stream.impl.fusing.ActorInterpreter
 import akka.stream.impl.io.SslTlsCipherActor
-import akka.stream.scaladsl._
 import akka.stream._
-import akka.stream.io._
 import akka.stream.io.SslTls.TlsModule
 import akka.stream.stage.Stage
-import akka.util.ByteString
 import org.reactivestreams._
 
 import scala.concurrent.{ Await, ExecutionContextExecutor }
@@ -28,17 +25,14 @@ import scala.concurrent.{ Await, ExecutionContextExecutor }
 /**
  * INTERNAL API
  */
-private[akka] case class ActorMaterializerImpl(
-  val system: ActorSystem,
-  override val settings: ActorMaterializerSettings,
-  dispatchers: Dispatchers,
-  val supervisor: ActorRef,
-  val haveShutDown: AtomicBoolean,
-  flowNameCounter: AtomicLong,
-  namePrefix: String,
-  optimizations: Optimizations)
-  extends ActorMaterializer {
-  import ActorMaterializerImpl._
+private[akka] case class ActorMaterializerImpl(val system: ActorSystem,
+                                               override val settings: ActorMaterializerSettings,
+                                               dispatchers: Dispatchers,
+                                               val supervisor: ActorRef,
+                                               val haveShutDown: AtomicBoolean,
+                                               flowNameCounter: AtomicLong,
+                                               namePrefix: String,
+                                               optimizations: Optimizations) extends ActorMaterializer {
   import akka.stream.impl.Stages._
 
   override def shutdown(): Unit =
@@ -103,7 +97,7 @@ private[akka] case class ActorMaterializerImpl(
           case tls: TlsModule ⇒ // TODO solve this so TlsModule doesn't need special treatment here
             val es = effectiveSettings(effectiveAttributes)
             val props =
-              SslTlsCipherActor.props(es, tls.sslContext, tls.firstSession, tracing = false, tls.role, tls.closing, tls.hostInfo)
+              SslTlsCipherActor.props(es, tls.sslContext, tls.firstSession, tls.role, tls.closing, tls.hostInfo)
             val impl = actorOf(props, stageName(effectiveAttributes), es.dispatcher)
             def factory(id: Int) = new ActorPublisher[Any](impl) {
               override val wakeUpMsg = FanOut.SubstreamSubscribePending(id)
@@ -174,10 +168,10 @@ private[akka] case class ActorMaterializerImpl(
                 (FlexiRoute.props(effectiveSettings, r.shape, flexi), r.shape.inlets.head: InPort, r.shape.outlets)
 
               case BroadcastModule(shape, eagerCancel, _) ⇒
-                (Broadcast.props(effectiveSettings, eagerCancel, shape.outArray.size), shape.in, shape.outArray.toSeq)
+                (Broadcast.props(effectiveSettings, eagerCancel, shape.outArray.length), shape.in, shape.outArray.toSeq)
 
               case BalanceModule(shape, waitForDownstreams, _) ⇒
-                (Balance.props(effectiveSettings, shape.outArray.size, waitForDownstreams), shape.in, shape.outArray.toSeq)
+                (Balance.props(effectiveSettings, shape.outArray.length, waitForDownstreams), shape.in, shape.outArray.toSeq)
 
               case unzip: UnzipWithModule ⇒
                 (unzip.props(effectiveSettings), unzip.inPorts.head, unzip.shape.outlets)
@@ -237,7 +231,7 @@ private[akka] case class ActorMaterializerImpl(
  */
 private[akka] object FlowNameCounter extends ExtensionId[FlowNameCounter] with ExtensionIdProvider {
   override def get(system: ActorSystem): FlowNameCounter = super.get(system)
-  override def lookup = FlowNameCounter
+  override def lookup() = FlowNameCounter
   override def createExtension(system: ExtendedActorSystem): FlowNameCounter = new FlowNameCounter
 }
 
@@ -259,13 +253,13 @@ private[akka] object StreamSupervisor {
     extends DeadLetterSuppression with NoSerializationVerificationNeeded
 
   /** Testing purpose */
-  final case object GetChildren
+  case object GetChildren
   /** Testing purpose */
   final case class Children(children: Set[ActorRef])
   /** Testing purpose */
-  final case object StopChildren
+  case object StopChildren
   /** Testing purpose */
-  final case object StoppedChildren
+  case object StoppedChildren
 }
 
 private[akka] class StreamSupervisor(settings: ActorMaterializerSettings, haveShutDown: AtomicBoolean) extends Actor {
@@ -291,7 +285,6 @@ private[akka] class StreamSupervisor(settings: ActorMaterializerSettings, haveSh
  */
 private[akka] object ActorProcessorFactory {
   import akka.stream.impl.Stages._
-  import ActorMaterializerImpl._
 
   def props(materializer: ActorMaterializer, op: StageModule, parentAttributes: Attributes): (Props, Any) = {
     val att = parentAttributes and op.attributes
@@ -309,17 +302,17 @@ private[akka] object ActorProcessorFactory {
       case Collect(pf, _)             ⇒ interp(fusing.Collect(pf, settings.supervisionDecider))
       case Scan(z, f, _)              ⇒ interp(fusing.Scan(z, f, settings.supervisionDecider))
       case Fold(z, f, _)              ⇒ interp(fusing.Fold(z, f, settings.supervisionDecider))
-      case Recover(pf, _)             ⇒ (ActorInterpreter.props(settings, List(fusing.Recover(pf)), materializer, att), ())
-      case Scan(z, f, _)              ⇒ (ActorInterpreter.props(settings, List(fusing.Scan(z, f, settings.supervisionDecider)), materializer, att), ())
-      case Expand(s, f, _)            ⇒ (ActorInterpreter.props(settings, List(fusing.Expand(s, f)), materializer, att), ())
-      case Conflate(s, f, _)          ⇒ (ActorInterpreter.props(settings, List(fusing.Conflate(s, f, settings.supervisionDecider)), materializer, att), ())
-      case Buffer(n, s, _)            ⇒ (ActorInterpreter.props(settings, List(fusing.Buffer(n, s)), materializer, att), ())
-      case MapConcat(f, _)            ⇒ (ActorInterpreter.props(settings, List(fusing.MapConcat(f, settings.supervisionDecider)), materializer, att), ())
-      case MapAsync(p, f, _)          ⇒ (ActorInterpreter.props(settings, List(fusing.MapAsync(p, f, settings.supervisionDecider)), materializer, att), ())
-      case MapAsyncUnordered(p, f, _) ⇒ (ActorInterpreter.props(settings, List(fusing.MapAsyncUnordered(p, f, settings.supervisionDecider)), materializer, att), ())
-      case Grouped(n, _)              ⇒ (ActorInterpreter.props(settings, List(fusing.Grouped(n)), materializer, att), ())
-      case Sliding(n, step, _)        ⇒ (ActorInterpreter.props(settings, List(fusing.Sliding(n, step)), materializer, att), ())
-      case Log(n, e, l, _)            ⇒ (ActorInterpreter.props(settings, List(fusing.Log(n, e, l)), materializer, att), ())
+      case Recover(pf, _)             ⇒ interp(fusing.Recover(pf))
+      case Scan(z, f, _)              ⇒ interp(fusing.Scan(z, f, settings.supervisionDecider))
+      case Expand(s, f, _)            ⇒ interp(fusing.Expand(s, f))
+      case Conflate(s, f, _)          ⇒ interp(fusing.Conflate(s, f, settings.supervisionDecider))
+      case Buffer(n, s, _)            ⇒ interp(fusing.Buffer(n, s))
+      case MapConcat(f, _)            ⇒ interp(fusing.MapConcat(f, settings.supervisionDecider))
+      case MapAsync(p, f, _)          ⇒ interp(fusing.MapAsync(p, f, settings.supervisionDecider))
+      case MapAsyncUnordered(p, f, _) ⇒ interp(fusing.MapAsyncUnordered(p, f, settings.supervisionDecider))
+      case Grouped(n, _)              ⇒ interp(fusing.Grouped(n))
+      case Sliding(n, step, _)        ⇒ interp(fusing.Sliding(n, step))
+      case Log(n, e, l, _)            ⇒ interp(fusing.Log(n, e, l))
       case GroupBy(f, _)              ⇒ (GroupByProcessorImpl.props(settings, f), ())
       case PrefixAndTail(n, _)        ⇒ (PrefixAndTailImpl.props(settings, n), ())
       case Split(d, _)                ⇒ (SplitWhereProcessorImpl.props(settings, d), ())
diff --git a/akka-stream/src/main/scala/akka/stream/impl/ActorProcessor.scala b/akka-stream/src/main/scala/akka/stream/impl/ActorProcessor.scala
index f7e9711cd7..a513baed8d 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/ActorProcessor.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/ActorProcessor.scala
@@ -3,7 +3,6 @@
  */
 package akka.stream.impl
 
-import java.util.Arrays
 import akka.actor._
 import akka.stream.{ AbruptTerminationException, ActorMaterializerSettings }
 import akka.stream.actor.ActorSubscriber.OnSubscribe
@@ -101,7 +100,7 @@ private[akka] abstract class BatchingInputBuffer(val size: Int, val pump: Pump)
   override def isClosed: Boolean = upstreamCompleted
 
   private def clear(): Unit = {
-    Arrays.fill(inputBuffer, 0, inputBuffer.length, null)
+    java.util.Arrays.fill(inputBuffer, 0, inputBuffer.length, null)
     inputBufferElements = 0
   }
 
diff --git a/akka-stream/src/main/scala/akka/stream/impl/FanIn.scala b/akka-stream/src/main/scala/akka/stream/impl/FanIn.scala
index 38b56f32a0..70feb471ec 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/FanIn.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/FanIn.scala
@@ -9,8 +9,6 @@ import akka.stream.actor.{ ActorSubscriberMessage, ActorSubscriber }
 import akka.stream.scaladsl.FlexiMerge.MergeLogic
 import org.reactivestreams.{ Subscription, Subscriber }
 
-import scala.collection.immutable
-
 /**
  * INTERNAL API
  */
@@ -105,7 +103,7 @@ private[akka] object FanIn {
     def cancel(input: Int) =
       if (!cancelled(input)) {
         inputs(input).cancel()
-        cancelled(input, true)
+        cancelled(input, on = true)
         unmarkInput(input)
       }
 
@@ -117,7 +115,7 @@ private[akka] object FanIn {
       if (!marked(input)) {
         if (depleted(input)) markedDepleted += 1
         if (pending(input)) markedPending += 1
-        marked(input, true)
+        marked(input, on = true)
         markCount += 1
       }
     }
@@ -126,7 +124,7 @@ private[akka] object FanIn {
       if (marked(input)) {
         if (depleted(input)) markedDepleted -= 1
         if (pending(input)) markedPending -= 1
-        marked(input, false)
+        marked(input, on = false)
         markCount -= 1
       }
     }
@@ -171,11 +169,11 @@ private[akka] object FanIn {
       val elem = input.dequeueInputElement()
       if (!input.inputsAvailable) {
         if (marked(id)) markedPending -= 1
-        pending(id, false)
+        pending(id, on = false)
       }
       if (input.inputsDepleted) {
         if (marked(id)) markedDepleted += 1
-        depleted(id, true)
+        depleted(id, on = true)
         onDepleted(id)
       }
       elem
@@ -202,7 +200,7 @@ private[akka] object FanIn {
     }
 
     val AnyOfMarkedInputs = new TransferState {
-      override def isCompleted: Boolean = (markedDepleted == markCount && markedPending == 0)
+      override def isCompleted: Boolean = markedDepleted == markCount && markedPending == 0
       override def isReady: Boolean = markedPending > 0
     }
 
@@ -222,15 +220,15 @@ private[akka] object FanIn {
         inputs(id).subreceive(ActorSubscriber.OnSubscribe(subscription))
       case OnNext(id, elem) ⇒
         if (marked(id) && !pending(id)) markedPending += 1
-        pending(id, true)
+        pending(id, on = true)
         inputs(id).subreceive(ActorSubscriberMessage.OnNext(elem))
       case OnComplete(id) ⇒
         if (!pending(id)) {
           if (marked(id) && !depleted(id)) markedDepleted += 1
-          depleted(id, true)
+          depleted(id, on = true)
           onDepleted(id)
         }
-        completed(id, true)
+        completed(id, on = true)
         inputs(id).subreceive(ActorSubscriberMessage.OnComplete)
       case OnError(id, e) ⇒
         onError(id, e)
diff --git a/akka-stream/src/main/scala/akka/stream/impl/FlexiMergeImpl.scala b/akka-stream/src/main/scala/akka/stream/impl/FlexiMergeImpl.scala
index 268729d814..7976583228 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/FlexiMergeImpl.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/FlexiMergeImpl.scala
@@ -42,9 +42,9 @@ private[akka] class FlexiMergeImpl[T, S <: Shape](
   }
 
   override protected val inputBunch = new FanIn.InputBunch(inputCount, settings.maxInputBufferSize, this) {
-    override def onError(input: Int, e: Throwable): Unit = {
+    override def onError(input: Int, t: Throwable): Unit = {
       changeBehavior(
-        try completion.onUpstreamFailure(ctx, inputMapping(input), e)
+        try completion.onUpstreamFailure(ctx, inputMapping(input), t)
         catch {
           case NonFatal(e) ⇒ fail(e); mergeLogic.SameState
         })
diff --git a/akka-stream/src/main/scala/akka/stream/impl/FlexiRouteImpl.scala b/akka-stream/src/main/scala/akka/stream/impl/FlexiRouteImpl.scala
index a6b361b4ab..c5e9d41b2f 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/FlexiRouteImpl.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/FlexiRouteImpl.scala
@@ -51,9 +51,9 @@ private[akka] class FlexiRouteImpl[T, S <: Shape](_settings: ActorMaterializerSe
   }
 
   override protected val primaryInputs: Inputs = new BatchingInputBuffer(settings.maxInputBufferSize, this) {
-    override def onError(e: Throwable): Unit = {
-      try completion.onUpstreamFailure(ctx, e) catch { case NonFatal(e) ⇒ fail(e) }
-      fail(e)
+    override def onError(t: Throwable): Unit = {
+      try completion.onUpstreamFailure(ctx, t) catch { case NonFatal(e) ⇒ fail(e) }
+      fail(t)
     }
 
     override def onComplete(): Unit = {
diff --git a/akka-stream/src/main/scala/akka/stream/impl/Flows.scala b/akka-stream/src/main/scala/akka/stream/impl/FlowModule.scala
similarity index 100%
rename from akka-stream/src/main/scala/akka/stream/impl/Flows.scala
rename to akka-stream/src/main/scala/akka/stream/impl/FlowModule.scala
diff --git a/akka-stream/src/main/scala/akka/stream/impl/Modules.scala b/akka-stream/src/main/scala/akka/stream/impl/Modules.scala
index 3776655de2..1ded51b290 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/Modules.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/Modules.scala
@@ -10,7 +10,7 @@ import akka.stream._
 import org.reactivestreams._
 import scala.annotation.unchecked.uncheckedVariance
 import scala.concurrent.duration.FiniteDuration
-import scala.concurrent.{ Promise }
+import scala.concurrent.Promise
 import scala.util.{ Failure, Success }
 
 /**
diff --git a/akka-stream/src/main/scala/akka/stream/impl/Stages.scala b/akka-stream/src/main/scala/akka/stream/impl/Stages.scala
index 0fa58bfc28..c29a0127d8 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/Stages.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/Stages.scala
@@ -3,14 +3,13 @@
  */
 package akka.stream.impl
 
-import akka.event.{ LoggingAdapter, Logging }
+import akka.event.LoggingAdapter
 import akka.stream.impl.SplitDecision.SplitDecision
 import akka.stream.impl.StreamLayout._
 import akka.stream.{ OverflowStrategy, TimerTransformer, Attributes }
 import akka.stream.Attributes._
 import akka.stream.stage.Stage
 import org.reactivestreams.Processor
-import akka.event.Logging.simpleName
 import scala.collection.immutable
 import scala.concurrent.Future
 
diff --git a/akka-stream/src/main/scala/akka/stream/impl/StreamLayout.scala b/akka-stream/src/main/scala/akka/stream/impl/StreamLayout.scala
index 461ae2f691..d84da3721c 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/StreamLayout.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/StreamLayout.scala
@@ -3,7 +3,7 @@
  */
 package akka.stream.impl
 
-import java.util.concurrent.atomic.{ AtomicInteger, AtomicBoolean, AtomicReference }
+import java.util.concurrent.atomic.{ AtomicInteger, AtomicReference }
 import akka.stream.impl.MaterializerSession.MaterializationPanic
 import akka.stream.impl.StreamLayout.Module
 import akka.stream.scaladsl.Keep
@@ -58,7 +58,8 @@ private[akka] object StreamLayout {
     if (downs != ups2) problems ::= s"inconsistent maps: ups ${pairs(ups2 -- inter)} downs ${pairs(downs -- inter)}"
     val (allIn, dupIn, allOut, dupOut) =
       subModules.foldLeft((Set.empty[InPort], Set.empty[InPort], Set.empty[OutPort], Set.empty[OutPort])) {
-        case ((ai, di, ao, doo), m) ⇒ (ai ++ m.inPorts, di ++ ai.intersect(m.inPorts), ao ++ m.outPorts, doo ++ ao.intersect(m.outPorts))
+        case ((ai, di, ao, doo), sm) ⇒
+          (ai ++ sm.inPorts, di ++ ai.intersect(sm.inPorts), ao ++ sm.outPorts, doo ++ ao.intersect(sm.outPorts))
       }
     if (dupIn.nonEmpty) problems ::= s"duplicate ports in submodules ${ins(dupIn)}"
     if (dupOut.nonEmpty) problems ::= s"duplicate ports in submodules ${outs(dupOut)}"
@@ -73,7 +74,7 @@ private[akka] object StreamLayout {
       n match {
         case Ignore                  ⇒ Set.empty
         case Transform(f, dep)       ⇒ atomics(dep)
-        case Atomic(m)               ⇒ Set(m)
+        case Atomic(module)          ⇒ Set(module)
         case Combine(f, left, right) ⇒ atomics(left) ++ atomics(right)
       }
     val atomic = atomics(materializedValueComputation)
diff --git a/akka-stream/src/main/scala/akka/stream/impl/StreamOfStreamProcessors.scala b/akka-stream/src/main/scala/akka/stream/impl/StreamOfStreamProcessors.scala
index 4bc2e02dbf..c659035bd3 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/StreamOfStreamProcessors.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/StreamOfStreamProcessors.scala
@@ -8,7 +8,6 @@ import akka.actor._
 import akka.stream.ActorMaterializerSettings
 import org.reactivestreams.{ Publisher, Subscriber, Subscription }
 import scala.collection.mutable
-import scala.concurrent.duration.FiniteDuration
 
 /**
  * INTERNAL API
@@ -48,7 +47,7 @@ private[akka] object MultiStreamOutputProcessor {
     override def subreceive: SubReceive =
       throw new UnsupportedOperationException("Substream outputs are managed in a dedicated receive block")
 
-    def isAttached() = state.get().isInstanceOf[Attached]
+    def isAttached = state.get().isInstanceOf[Attached]
 
     def enqueueOutputDemand(demand: Long): Unit = {
       downstreamDemand += demand
@@ -188,8 +187,8 @@ private[akka] trait MultiStreamOutputProcessorLike extends Pump with StreamSubsc
       case _         ⇒ // ignore...
     }
     case SubstreamSubscriptionTimeout(key) ⇒ substreamOutputs.get(key) match {
-      case Some(sub) if !sub.isAttached() ⇒ subscriptionTimedOut(sub)
-      case _                              ⇒ // ignore...
+      case Some(sub) if !sub.isAttached ⇒ subscriptionTimedOut(sub)
+      case _                            ⇒ // ignore...
     }
     case SubstreamCancel(key) ⇒
       invalidateSubstreamOutput(key)
diff --git a/akka-stream/src/main/scala/akka/stream/impl/StreamSubscriptionTimeout.scala b/akka-stream/src/main/scala/akka/stream/impl/StreamSubscriptionTimeout.scala
index 3662ceec4f..a6388d55c2 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/StreamSubscriptionTimeout.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/StreamSubscriptionTimeout.scala
@@ -15,7 +15,7 @@ object StreamSubscriptionTimeoutSupport {
   /**
    * A subscriber who calls `cancel` directly from `onSubscribe` and ignores all other callbacks.
    */
-  final case object CancelingSubscriber extends Subscriber[Any] {
+  case object CancelingSubscriber extends Subscriber[Any] {
     override def onSubscribe(s: Subscription): Unit = {
       ReactiveStreamsCompliance.requireNonNullSubscription(s)
       s.cancel()
@@ -37,7 +37,7 @@ object StreamSubscriptionTimeoutSupport {
    * Subscription timeout which does not start any scheduled events and always returns `true`.
    * This specialized implementation is to be used for "noop" timeout mode.
    */
-  final case object NoopSubscriptionTimeout extends Cancellable {
+  case object NoopSubscriptionTimeout extends Cancellable {
     override def cancel() = true
     override def isCancelled = true
   }
@@ -79,11 +79,11 @@ private[akka] trait StreamSubscriptionTimeoutSupport {
     target match {
       case p: Processor[_, _] ⇒
         log.debug("Cancelling {} Processor's publisher and subscriber sides (after {} ms)", p, millis)
-        handleSubscriptionTimeout(target, new SubscriptionTimeoutException(s"Publisher was not attached to upstream within deadline (${millis}) ms") with NoStackTrace)
+        handleSubscriptionTimeout(target, new SubscriptionTimeoutException(s"Publisher was not attached to upstream within deadline ($millis) ms") with NoStackTrace)
 
       case p: Publisher[_] ⇒
         log.debug("Cancelling {} (after: {} ms)", p, millis)
-        handleSubscriptionTimeout(target, new SubscriptionTimeoutException(s"Publisher (${p}) you are trying to subscribe to has been shut-down " +
+        handleSubscriptionTimeout(target, new SubscriptionTimeoutException(s"Publisher ($p) you are trying to subscribe to has been shut-down " +
           s"because exceeding it's subscription-timeout.") with NoStackTrace)
     }
   }
diff --git a/akka-stream/src/main/scala/akka/stream/impl/SubscriberManagement.scala b/akka-stream/src/main/scala/akka/stream/impl/SubscriberManagement.scala
index 3b8051b349..bb3adf558e 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/SubscriberManagement.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/SubscriberManagement.scala
@@ -173,7 +173,7 @@ private[akka] trait SubscriberManagement[T] extends ResizableMultiReaderRingBuff
             val element = buffer.read(head)
             head.dispatch(element)
             head.totalDemand -= 1
-            dispatch(tail, true)
+            dispatch(tail, sent = true)
           } else dispatch(tail, sent)
         case _ ⇒ sent
       }
diff --git a/akka-stream/src/main/scala/akka/stream/impl/TickPublisher.scala b/akka-stream/src/main/scala/akka/stream/impl/TickPublisher.scala
index a7808c0e35..b022c3a39b 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/TickPublisher.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/TickPublisher.scala
@@ -122,7 +122,7 @@ private[akka] class TickPublisher(initialDelay: FiniteDuration, interval: Finite
   }
 
   override def postStop(): Unit = {
-    tickTask.foreach(_.cancel)
+    tickTask.foreach(_.cancel())
     cancelled.set(true)
     if (exposedPublisher ne null)
       exposedPublisher.shutdown(ActorPublisher.SomeNormalShutdownReason)
diff --git a/akka-stream/src/main/scala/akka/stream/impl/TimerTransformerProcessorsImpl.scala b/akka-stream/src/main/scala/akka/stream/impl/TimerTransformerProcessorsImpl.scala
index 31df7c7518..de00397883 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/TimerTransformerProcessorsImpl.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/TimerTransformerProcessorsImpl.scala
@@ -3,7 +3,6 @@
  */
 package akka.stream.impl
 
-import java.util.LinkedList
 import akka.stream.ActorMaterializerSettings
 import akka.stream.TimerTransformer
 import scala.util.control.NonFatal
@@ -46,7 +45,7 @@ private[akka] class TimerTransformerProcessorsImpl(
   }
 
   val schedulerInputs: Inputs = new DefaultInputTransferStates {
-    val queue = new LinkedList[Any]
+    val queue = new java.util.LinkedList[Any]
 
     override def dequeueInputElement(): Any = queue.removeFirst()
 
@@ -76,6 +75,11 @@ private[akka] class TimerTransformerProcessorsImpl(
     def isCompleted = false
   }
 
+  private val terminate = TransferPhase(Always) { () ⇒
+    emits = transformer.onTermination(errorEvent)
+    emitAndThen(completedPhase)
+  }
+
   private val running: TransferPhase = TransferPhase(RunningCondition) { () ⇒
     if (primaryInputs.inputsDepleted || (transformer.isComplete && !schedulerInputs.inputsAvailable)) {
       nextPhase(terminate)
@@ -89,11 +93,6 @@ private[akka] class TimerTransformerProcessorsImpl(
     }
   }
 
-  private val terminate = TransferPhase(Always) { () ⇒
-    emits = transformer.onTermination(errorEvent)
-    emitAndThen(completedPhase)
-  }
-
   override def toString: String = s"Transformer(emits=$emits, transformer=$transformer)"
 
 }
diff --git a/akka-stream/src/main/scala/akka/stream/impl/fusing/ActorInterpreter.scala b/akka-stream/src/main/scala/akka/stream/impl/fusing/ActorInterpreter.scala
index 8481c9d1fc..76e9fdb77b 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/fusing/ActorInterpreter.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/fusing/ActorInterpreter.scala
@@ -3,20 +3,17 @@
  */
 package akka.stream.impl.fusing
 
-import java.util.Arrays
 import akka.actor._
 import akka.stream.impl.ReactiveStreamsCompliance._
 import akka.stream.{ AbruptTerminationException, ActorMaterializerSettings, Attributes, ActorMaterializer }
 import akka.stream.actor.ActorSubscriber.OnSubscribe
 import akka.stream.actor.ActorSubscriberMessage.{ OnNext, OnError, OnComplete }
 import akka.stream.impl._
-import akka.stream.impl.fusing.OneBoundedInterpreter.{ InitializationFailed, InitializationFailure, InitializationSuccessful }
+import akka.stream.impl.fusing.OneBoundedInterpreter.{ InitializationFailed, InitializationSuccessful }
 import akka.stream.stage._
 import org.reactivestreams.{ Subscriber, Subscription }
 import akka.event.{ Logging, LoggingAdapter }
 
-import scala.util.control.NonFatal
-
 /**
  * INTERNAL API
  */
@@ -101,7 +98,7 @@ private[akka] class BatchingActorInputBoundary(val size: Int, val name: String)
   }
 
   private def clear(): Unit = {
-    Arrays.fill(inputBuffer, 0, inputBuffer.length, null)
+    java.util.Arrays.fill(inputBuffer, 0, inputBuffer.length, null)
     inputBufferElements = 0
   }
 
diff --git a/akka-stream/src/main/scala/akka/stream/impl/fusing/Interpreter.scala b/akka-stream/src/main/scala/akka/stream/impl/fusing/OneBoundedInterpreter.scala
similarity index 99%
rename from akka-stream/src/main/scala/akka/stream/impl/fusing/Interpreter.scala
rename to akka-stream/src/main/scala/akka/stream/impl/fusing/OneBoundedInterpreter.scala
index 6b7052232f..bdb6efa411 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/fusing/Interpreter.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/fusing/OneBoundedInterpreter.scala
@@ -21,7 +21,7 @@ private[akka] object OneBoundedInterpreter {
   /** INTERNAL API */
   private[akka] sealed trait InitializationStatus
   /** INTERNAL API */
-  private[akka] final case object InitializationSuccessful extends InitializationStatus
+  private[akka] case object InitializationSuccessful extends InitializationStatus
   /** INTERNAL API */
   private[akka] final case class InitializationFailed(failures: immutable.Seq[InitializationFailure]) extends InitializationStatus {
     // exceptions are reverse ordered here, below methods help to avoid confusion when used from the outside
@@ -197,7 +197,7 @@ private[akka] class OneBoundedInterpreter(ops: Seq[Stage[_, _]],
   private var lastOpFailing: Int = -1
 
   private def pipeName(op: UntypedOp): String = {
-    val o = (op: AbstractStage[_, _, _, _, _, _])
+    val o = op: AbstractStage[_, _, _, _, _, _]
     (o match {
       case Finished               ⇒ "finished"
       case _: BoundaryStage       ⇒ "boundary"
@@ -219,7 +219,7 @@ private[akka] class OneBoundedInterpreter(ops: Seq[Stage[_, _]],
   private def calculateJumpBacks: Array[Int] = {
     val table = Array.ofDim[Int](pipeline.length)
     var nextJumpBack = -1
-    for (pos ← 0 until pipeline.length) {
+    for (pos ← pipeline.indices) {
       table(pos) = nextJumpBack
       if (!pipeline(pos).isInstanceOf[PushStage[_, _]]) nextJumpBack = pos
     }
@@ -310,7 +310,7 @@ private[akka] class OneBoundedInterpreter(ops: Seq[Stage[_, _]],
       null
     }
 
-    override def getAsyncCallback(): AsyncCallback[Any] = {
+    override def getAsyncCallback: AsyncCallback[Any] = {
       val current = currentOp.asInstanceOf[AsyncStage[Any, Any, Any]]
       val context = current.context // avoid concurrent access (to avoid @volatile)
       new AsyncCallback[Any] {
diff --git a/akka-stream/src/main/scala/akka/stream/impl/fusing/Ops.scala b/akka-stream/src/main/scala/akka/stream/impl/fusing/Ops.scala
index dc288fd9eb..679f7a643a 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/fusing/Ops.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/fusing/Ops.scala
@@ -6,7 +6,6 @@ package akka.stream.impl.fusing
 import akka.event.Logging.LogLevel
 import akka.event.{ LogSource, Logging, LoggingAdapter }
 import akka.stream.Attributes.LogLevels
-import akka.stream.Supervision.Resume
 import akka.stream.impl.{ FixedSizeBuffer, ReactiveStreamsCompliance }
 import akka.stream.stage._
 import akka.stream.{ Supervision, _ }
@@ -68,7 +67,7 @@ private[akka] final case class DropWhile[T](p: T ⇒ Boolean, decider: Supervisi
   override def decide(t: Throwable): Supervision.Directive = decider(t)
 }
 
-private[akka] final object Collect {
+private[akka] object Collect {
   // Cached function that can be used with PartialFunction.applyOrElse to ensure that A) the guard is only applied once,
   // and the caller can check the returned value with Collect.notApplied to query whether the PF was applied or not.
   // Prior art: https://github.com/scala/scala/blob/v2.11.4/src/library/scala/collection/immutable/List.scala#L458
@@ -336,12 +335,12 @@ private[akka] final case class Buffer[T](size: Int, overflowStrategy: OverflowSt
 
   override def onPull(ctx: DetachedContext[T]): DownstreamDirective = {
     if (ctx.isFinishing) {
-      val elem = buffer.dequeue().asInstanceOf[T]
+      val elem = buffer.dequeue()
       if (buffer.isEmpty) ctx.pushAndFinish(elem)
       else ctx.push(elem)
-    } else if (ctx.isHoldingUpstream) ctx.pushAndPull(buffer.dequeue().asInstanceOf[T])
+    } else if (ctx.isHoldingUpstream) ctx.pushAndPull(buffer.dequeue())
     else if (buffer.isEmpty) ctx.holdDownstream()
-    else ctx.push(buffer.dequeue().asInstanceOf[T])
+    else ctx.push(buffer.dequeue())
   }
 
   override def onUpstreamFinish(ctx: DetachedContext[T]): TerminationDirective =
@@ -350,37 +349,31 @@ private[akka] final case class Buffer[T](size: Int, overflowStrategy: OverflowSt
 
   val enqueueAction: (DetachedContext[T], T) ⇒ UpstreamDirective = {
     overflowStrategy match {
-      case DropHead ⇒ { (ctx, elem) ⇒
+      case DropHead ⇒ (ctx, elem) ⇒
         if (buffer.isFull) buffer.dropHead()
         buffer.enqueue(elem)
         ctx.pull()
-      }
-      case DropTail ⇒ { (ctx, elem) ⇒
+        case DropTail ⇒ (ctx, elem) ⇒
         if (buffer.isFull) buffer.dropTail()
         buffer.enqueue(elem)
         ctx.pull()
-      }
-      case DropBuffer ⇒ { (ctx, elem) ⇒
+        case DropBuffer ⇒ (ctx, elem) ⇒
         if (buffer.isFull) buffer.clear()
         buffer.enqueue(elem)
         ctx.pull()
-      }
-      case DropNew ⇒ { (ctx, elem) ⇒
+        case DropNew ⇒ (ctx, elem) ⇒
         if (!buffer.isFull) buffer.enqueue(elem)
         ctx.pull()
-      }
-      case Backpressure ⇒ { (ctx, elem) ⇒
+        case Backpressure ⇒ (ctx, elem) ⇒
         buffer.enqueue(elem)
         if (buffer.isFull) ctx.holdUpstream()
         else ctx.pull()
-      }
-      case Fail ⇒ { (ctx, elem) ⇒
+        case Fail ⇒ (ctx, elem) ⇒
         if (buffer.isFull) ctx.fail(new Fail.BufferOverflowException(s"Buffer overflow (max capacity was: $size)!"))
         else {
           buffer.enqueue(elem)
           ctx.pull()
         }
-      }
     }
   }
 }
@@ -478,9 +471,9 @@ private[akka] final case class Expand[In, Out, Seed](seed: In ⇒ Seed, extrapol
     else ctx.absorbTermination()
   }
 
-  final override def decide(t: Throwable): Supervision.Directive = Supervision.Stop
+  override def decide(t: Throwable): Supervision.Directive = Supervision.Stop
 
-  final override def restart(): Expand[In, Out, Seed] =
+  override def restart(): Expand[In, Out, Seed] =
     throw new UnsupportedOperationException("Expand doesn't support restart")
 }
 
@@ -505,7 +498,7 @@ private[akka] final case class MapAsync[In, Out](parallelism: Int, f: In ⇒ Fut
   private val elemsInFlight = FixedSizeBuffer[Try[Out]](parallelism)
 
   override def preStart(ctx: AsyncContext[Out, Notification]): Unit = {
-    callback = ctx.getAsyncCallback()
+    callback = ctx.getAsyncCallback
   }
 
   override def decide(ex: Throwable) = decider(ex)
@@ -554,7 +547,7 @@ private[akka] final case class MapAsync[In, Out](parallelism: Int, f: In ⇒ Fut
           else ctx.ignore()
         } else ctx.fail(ex)
       case (idx, s: Success[_]) ⇒
-        val ex = try {
+        val exception = try {
           ReactiveStreamsCompliance.requireNonNullElement(s.value)
           elemsInFlight.put(idx, s)
           null: Exception
@@ -565,7 +558,7 @@ private[akka] final case class MapAsync[In, Out](parallelism: Int, f: In ⇒ Fut
               null: Exception
             } else ex
         }
-        if (ex != null) ctx.fail(ex)
+        if (exception != null) ctx.fail(exception)
         else if (ctx.isHoldingDownstream) rec()
         else ctx.ignore()
     }
@@ -589,7 +582,7 @@ private[akka] final case class MapAsyncUnordered[In, Out](parallelism: Int, f: I
   private def todo = inFlight + buffer.used
 
   override def preStart(ctx: AsyncContext[Out, Try[Out]]): Unit =
-    callback = ctx.getAsyncCallback()
+    callback = ctx.getAsyncCallback
 
   override def decide(ex: Throwable) = decider(ex)
 
diff --git a/akka-stream/src/main/scala/akka/stream/impl/io/SslTls.scala b/akka-stream/src/main/scala/akka/stream/impl/io/SslTlsCipherActor.scala
similarity index 93%
rename from akka-stream/src/main/scala/akka/stream/impl/io/SslTls.scala
rename to akka-stream/src/main/scala/akka/stream/impl/io/SslTlsCipherActor.scala
index 9ad40125fc..8780f53b8d 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/io/SslTls.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/io/SslTlsCipherActor.scala
@@ -4,8 +4,6 @@
 package akka.stream.impl.io
 
 import java.nio.ByteBuffer
-import java.security.Principal
-import java.security.cert.Certificate
 import javax.net.ssl.SSLEngineResult.HandshakeStatus
 import javax.net.ssl.SSLEngineResult.HandshakeStatus._
 import javax.net.ssl.SSLEngineResult.Status._
@@ -16,13 +14,8 @@ import akka.stream.impl.FanIn.InputBunch
 import akka.stream.impl.FanOut.OutputBunch
 import akka.stream.impl._
 import akka.util.ByteString
-import akka.util.ByteStringBuilder
-import org.reactivestreams.Publisher
-import org.reactivestreams.Subscriber
 import scala.annotation.tailrec
-import scala.collection.immutable
 import akka.stream.io._
-import akka.event.LoggingReceive
 
 /**
  * INTERNAL API.
@@ -32,11 +25,11 @@ private[akka] object SslTlsCipherActor {
   def props(settings: ActorMaterializerSettings,
             sslContext: SSLContext,
             firstSession: NegotiateNewSession,
-            tracing: Boolean,
             role: Role,
             closing: Closing,
-            hostInfo: Option[(String, Int)]): Props =
-    Props(new SslTlsCipherActor(settings, sslContext, firstSession, tracing, role, closing, hostInfo)).withDeploy(Deploy.local)
+            hostInfo: Option[(String, Int)],
+            tracing: Boolean = false): Props =
+    Props(new SslTlsCipherActor(settings, sslContext, firstSession, role, closing, hostInfo, tracing)).withDeploy(Deploy.local)
 
   final val TransportIn = 0
   final val TransportOut = 0
@@ -49,8 +42,8 @@ private[akka] object SslTlsCipherActor {
  * INTERNAL API.
  */
 private[akka] class SslTlsCipherActor(settings: ActorMaterializerSettings, sslContext: SSLContext,
-                                      firstSession: NegotiateNewSession, tracing: Boolean,
-                                      role: Role, closing: Closing, hostInfo: Option[(String, Int)])
+                                      firstSession: NegotiateNewSession, role: Role, closing: Closing,
+                                      hostInfo: Option[(String, Int)], tracing: Boolean)
   extends Actor with ActorLogging with Pump {
 
   import SslTlsCipherActor._
@@ -113,7 +106,7 @@ private[akka] class SslTlsCipherActor(settings: ActorMaterializerSettings, sslCo
      * not know that we are runnable.
      */
     def putBack(b: ByteBuffer): Unit =
-      if (b.hasRemaining()) {
+      if (b.hasRemaining) {
         if (tracing) log.debug(s"putting back ${b.remaining} bytes into $name")
         val bs = ByteString(b)
         if (bs.nonEmpty) buffer = bs ++ buffer
@@ -156,12 +149,10 @@ private[akka] class SslTlsCipherActor(settings: ActorMaterializerSettings, sslCo
     e
   }
   var currentSession = engine.getSession
-  var currentSessionParameters = firstSession
-  applySessionParameters()
+  applySessionParameters(firstSession)
 
-  def applySessionParameters(): Unit = {
-    val csp = currentSessionParameters
-    import csp._
+  def applySessionParameters(params: NegotiateNewSession): Unit = {
+    import params._
     enabledCipherSuites foreach (cs ⇒ engine.setEnabledCipherSuites(cs.toArray))
     enabledProtocols foreach (p ⇒ engine.setEnabledProtocols(p.toArray))
     clientAuth match {
@@ -175,11 +166,10 @@ private[akka] class SslTlsCipherActor(settings: ActorMaterializerSettings, sslCo
     lastHandshakeStatus = engine.getHandshakeStatus
   }
 
-  def setNewSessionParameters(n: NegotiateNewSession): Unit = {
-    if (tracing) log.debug(s"applying $n")
+  def setNewSessionParameters(params: NegotiateNewSession): Unit = {
+    if (tracing) log.debug(s"applying $params")
     currentSession.invalidate()
-    currentSessionParameters = n
-    applySessionParameters()
+    applySessionParameters(params)
     corkUser = true
   }
 
@@ -280,7 +270,7 @@ private[akka] class SslTlsCipherActor(settings: ActorMaterializerSettings, sslCo
   }
 
   def completeOrFlush(): Unit =
-    if (engine.isOutboundDone()) nextPhase(completedPhase)
+    if (engine.isOutboundDone) nextPhase(completedPhase)
     else nextPhase(flushingOutbound)
 
   private def doInbound(isOutboundClosed: Boolean, inboundState: TransferState): Boolean =
@@ -370,7 +360,7 @@ private[akka] class SslTlsCipherActor(settings: ActorMaterializerSettings, sslCo
         userInChoppingBlock.putBack(userInBuffer)
       case CLOSED ⇒
         flushToTransport()
-        if (engine.isInboundDone()) nextPhase(completedPhase)
+        if (engine.isInboundDone) nextPhase(completedPhase)
         else nextPhase(awaitingClose)
       case s ⇒ fail(new IllegalStateException(s"unexpected status $s in doWrap()"))
     }
@@ -392,12 +382,12 @@ private[akka] class SslTlsCipherActor(settings: ActorMaterializerSettings, sslCo
             handshakeFinished()
             transportInChoppingBlock.putBack(transportInBuffer)
           case _ ⇒
-            if (transportInBuffer.hasRemaining()) doUnwrap()
+            if (transportInBuffer.hasRemaining) doUnwrap()
             else flushToUser()
         }
       case CLOSED ⇒
         flushToUser()
-        if (engine.isOutboundDone()) nextPhase(completedPhase)
+        if (engine.isOutboundDone) nextPhase(completedPhase)
         else nextPhase(flushingOutbound)
       case BUFFER_UNDERFLOW ⇒
         flushToUser()
diff --git a/akka-stream/src/main/scala/akka/stream/impl/io/TcpConnectionStream.scala b/akka-stream/src/main/scala/akka/stream/impl/io/TcpConnectionStream.scala
index a053f212a1..bb84039bdd 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/io/TcpConnectionStream.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/io/TcpConnectionStream.scala
@@ -5,13 +5,12 @@ package akka.stream.impl.io
 
 import java.net.InetSocketAddress
 import akka.io.{ IO, Tcp }
-import akka.stream.impl.io.StreamTcpManager.ExposedProcessor
 import scala.concurrent.Promise
 import akka.actor._
 import akka.util.ByteString
 import akka.io.Tcp._
-import akka.stream.{ AbruptTerminationException, StreamSubscriptionTimeoutSettings, ActorMaterializerSettings, StreamTcpException }
-import org.reactivestreams.{ Publisher, Processor }
+import akka.stream.{ AbruptTerminationException, ActorMaterializerSettings, StreamTcpException }
+import org.reactivestreams.Processor
 import akka.stream.impl._
 
 import scala.util.control.NoStackTrace
@@ -248,7 +247,7 @@ private[akka] abstract class TcpStreamActor(val settings: ActorMaterializerSetti
     case SubscriptionTimeout ⇒
       val millis = settings.subscriptionTimeoutSettings.timeout.toMillis
       if (!primaryOutputs.isSubscribed) {
-        fail(new SubscriptionTimeoutException(s"Publisher was not attached to upstream within deadline (${millis}) ms") with NoStackTrace)
+        fail(new SubscriptionTimeoutException(s"Publisher was not attached to upstream within deadline ($millis) ms") with NoStackTrace)
         context.stop(self)
       }
   }
@@ -305,7 +304,6 @@ private[akka] class OutboundTcpStreamActor(processorPromise: Promise[Processor[B
                                            _halfClose: Boolean,
                                            val connectCmd: Connect, _settings: ActorMaterializerSettings)
   extends TcpStreamActor(_settings, _halfClose) {
-  import TcpStreamActor._
   import context.system
 
   val initSteps = new SubReceive(waitingExposedProcessor)
diff --git a/akka-stream/src/main/scala/akka/stream/io/SslTls.scala b/akka-stream/src/main/scala/akka/stream/io/SslTls.scala
index 186dd5759a..eae3bf3305 100644
--- a/akka-stream/src/main/scala/akka/stream/io/SslTls.scala
+++ b/akka-stream/src/main/scala/akka/stream/io/SslTls.scala
@@ -121,7 +121,7 @@ object SslTls {
     override def withAttributes(att: Attributes): Module = copy(attributes = att)
     override def carbonCopy: Module = {
       val mod = TlsModule(attributes, sslContext, firstSession, role, closing, hostInfo)
-      if (plainIn == shape.inlets(0)) mod
+      if (plainIn == shape.inlets.head) mod
       else mod.replaceShape(mod.shape.asInstanceOf[BidiShape[_, _, _, _]].reversed)
     }
 
@@ -158,7 +158,7 @@ object SslTlsPlacebo {
     scaladsl.BidiFlow() { implicit b ⇒
       // this constructs a session for (invalid) protocol SSL_NULL_WITH_NULL_NULL
       val session = SSLContext.getDefault.createSSLEngine.getSession
-      val top = b.add(scaladsl.Flow[SslTlsOutbound].collect { case SendBytes(b) ⇒ b })
+      val top = b.add(scaladsl.Flow[SslTlsOutbound].collect { case SendBytes(bytes) ⇒ bytes })
       val bottom = b.add(scaladsl.Flow[ByteString].map(SessionBytes(session, _)))
       BidiShape(top, bottom)
     }
diff --git a/akka-stream/src/main/scala/akka/stream/javadsl/Flow.scala b/akka-stream/src/main/scala/akka/stream/javadsl/Flow.scala
index 821e7b6330..df2857bbb5 100644
--- a/akka-stream/src/main/scala/akka/stream/javadsl/Flow.scala
+++ b/akka-stream/src/main/scala/akka/stream/javadsl/Flow.scala
@@ -5,18 +5,16 @@ package akka.stream.javadsl
 
 import akka.event.LoggingAdapter
 import akka.stream._
-import akka.japi.{ Util, Pair }
+import akka.japi.Pair
 import akka.japi.function
-import akka.stream.impl.Stages.Recover
 import akka.stream.scaladsl
-import akka.stream.scaladsl.{ Keep, Sink, Source }
-import org.reactivestreams.{ Subscription, Publisher, Subscriber, Processor }
+import org.reactivestreams.Processor
 import scala.annotation.unchecked.uncheckedVariance
 import scala.collection.immutable
 import scala.concurrent.Future
 import scala.concurrent.duration.FiniteDuration
 import akka.stream.stage.Stage
-import akka.stream.impl.{ Stages, StreamLayout }
+import akka.stream.impl.StreamLayout
 
 object Flow {
 
diff --git a/akka-stream/src/main/scala/akka/stream/javadsl/Graph.scala b/akka-stream/src/main/scala/akka/stream/javadsl/Graph.scala
index 463b72380b..dc2ce75bb4 100644
--- a/akka-stream/src/main/scala/akka/stream/javadsl/Graph.scala
+++ b/akka-stream/src/main/scala/akka/stream/javadsl/Graph.scala
@@ -150,12 +150,14 @@ object Balance {
   /**
    * Create a new `Balance` vertex with the specified input type.
    */
-  def create[T](outputCount: Int): Graph[UniformFanOutShape[T, T], Unit] = create(outputCount, false)
+  def create[T](outputCount: Int): Graph[UniformFanOutShape[T, T], Unit] =
+    create(outputCount, waitForAllDownstreams = false)
 
   /**
    * Create a new `Balance` vertex with the specified input type.
    */
-  def create[T](clazz: Class[T], outputCount: Int): Graph[UniformFanOutShape[T, T], Unit] = create(outputCount)
+  def create[T](clazz: Class[T], outputCount: Int): Graph[UniformFanOutShape[T, T], Unit] =
+    create(outputCount)
 
   /**
    * Create a new `Balance` vertex with the specified input type.
diff --git a/akka-stream/src/main/scala/akka/stream/javadsl/Materialization.scala b/akka-stream/src/main/scala/akka/stream/javadsl/Keep.scala
similarity index 94%
rename from akka-stream/src/main/scala/akka/stream/javadsl/Materialization.scala
rename to akka-stream/src/main/scala/akka/stream/javadsl/Keep.scala
index bd08f4ea16..dc47d50092 100644
--- a/akka-stream/src/main/scala/akka/stream/javadsl/Materialization.scala
+++ b/akka-stream/src/main/scala/akka/stream/javadsl/Keep.scala
@@ -4,11 +4,8 @@
 package akka.stream.javadsl
 
 import akka.japi.function
-import akka.stream.scaladsl
 import akka.japi.Pair
 
-import scala.runtime.BoxedUnit
-
 object Keep {
   private val _left = new function.Function2[Any, Any, Any] with ((Any, Any) ⇒ Any) { def apply(l: Any, r: Any) = l }
   private val _right = new function.Function2[Any, Any, Any] with ((Any, Any) ⇒ Any) { def apply(l: Any, r: Any) = r }
diff --git a/akka-stream/src/main/scala/akka/stream/javadsl/Tcp.scala b/akka-stream/src/main/scala/akka/stream/javadsl/Tcp.scala
index 794a48e168..69de538ab5 100644
--- a/akka-stream/src/main/scala/akka/stream/javadsl/Tcp.scala
+++ b/akka-stream/src/main/scala/akka/stream/javadsl/Tcp.scala
@@ -36,7 +36,7 @@ object Tcp extends ExtensionId[Tcp] with ExtensionIdProvider {
      *
      * The produced [[scala.concurrent.Future]] is fulfilled when the unbinding has been completed.
      */
-    def unbind(): Future[Unit] = delegate.unbind
+    def unbind(): Future[Unit] = delegate.unbind()
   }
 
   /**
diff --git a/akka-stream/src/main/scala/akka/stream/scaladsl/Flow.scala b/akka-stream/src/main/scala/akka/stream/scaladsl/Flow.scala
index 29474686ce..61268a1ed7 100644
--- a/akka-stream/src/main/scala/akka/stream/scaladsl/Flow.scala
+++ b/akka-stream/src/main/scala/akka/stream/scaladsl/Flow.scala
@@ -214,9 +214,9 @@ final class Flow[-In, +Out, +Mat](private[stream] override val module: Module)
     val outs = copy.shape.outlets
     new Flow(module
       .compose(copy, combine)
-      .wire(shape.outlet, ins(0))
+      .wire(shape.outlet, ins.head)
       .wire(outs(1), shape.inlet)
-      .replaceShape(FlowShape(ins(1), outs(0))))
+      .replaceShape(FlowShape(ins(1), outs.head)))
   }
 
   /**
@@ -365,7 +365,7 @@ case class RunnableGraph[+Mat](private[stream] val module: StreamLayout.Module)
   def run()(implicit materializer: Materializer): Mat = materializer.materialize(this)
 
   override def withAttributes(attr: Attributes): RunnableGraph[Mat] =
-    new RunnableGraph(module.withAttributes(attr).nest)
+    new RunnableGraph(module.withAttributes(attr).nest())
 
   override def named(name: String): RunnableGraph[Mat] = withAttributes(Attributes.name(name))
 
diff --git a/akka-stream/src/main/scala/akka/stream/stage/Stage.scala b/akka-stream/src/main/scala/akka/stream/stage/Stage.scala
index e176606f4c..34b3e3377b 100644
--- a/akka-stream/src/main/scala/akka/stream/stage/Stage.scala
+++ b/akka-stream/src/main/scala/akka/stream/stage/Stage.scala
@@ -3,8 +3,7 @@
  */
 package akka.stream.stage
 
-import akka.event.{ Logging, LogSource }
-import akka.stream.{ ActorMaterializer, Materializer, Attributes, Supervision }
+import akka.stream.{ Materializer, Attributes, Supervision }
 
 /**
  * General interface for stream transformation.
@@ -34,10 +33,10 @@ sealed trait Stage[-In, Out]
 private[stream] object AbstractStage {
   final val UpstreamBall = 1
   final val DownstreamBall = 2
-  final val BothBalls = UpstreamBall | DownstreamBall
-  final val BothBallsAndNoTerminationPending = UpstreamBall | DownstreamBall | NoTerminationPending
   final val PrecedingWasPull = 0x4000
   final val NoTerminationPending = 0x8000
+  final val BothBalls = UpstreamBall | DownstreamBall
+  final val BothBallsAndNoTerminationPending = UpstreamBall | DownstreamBall | NoTerminationPending
 }
 
 abstract class AbstractStage[-In, Out, PushD <: Directive, PullD <: Directive, Ctx <: Context[Out], LifeCtx <: LifecycleContext] extends Stage[In, Out] {
@@ -655,7 +654,7 @@ trait AsyncContext[Out, Ext] extends DetachedContext[Out] {
    *
    * This object can be cached and reused within the same [[AsyncStage]].
    */
-  def getAsyncCallback(): AsyncCallback[Ext]
+  def getAsyncCallback: AsyncCallback[Ext]
   /**
    * In response to an asynchronous notification an [[AsyncStage]] may choose
    * to neither push nor pull nor terminate, which is represented as this