From 8f131c680fb089f4e1a8be78cfe4ad72b0a1123a Mon Sep 17 00:00:00 2001
From: Viktor Klang <viktor.klang@gmail.com>
Date: Tue, 30 Oct 2012 15:08:41 +0100
Subject: [PATCH] Switching to immutable.Seq instead of Seq

---
 .../akka/actor/RelativeActorPathSpec.scala    | 12 +++--
 .../scala/akka/actor/TypedActorSpec.scala     | 13 +++---
 .../workbench/BenchResultRepository.scala     | 29 ++++++------
 .../workbench/GoogleChartBuilder.scala        | 23 +++++-----
 .../akka/performance/workbench/Report.scala   | 18 ++++----
 .../src/main/scala/akka/actor/ActorPath.scala |  2 +-
 .../scala/akka/actor/ActorRefProvider.scala   |  2 +-
 .../main/scala/akka/actor/ActorSystem.scala   | 34 +++++++-------
 .../src/main/scala/akka/actor/Address.scala   |  5 ++-
 .../src/main/scala/akka/actor/Deployer.scala  |  2 +-
 .../main/scala/akka/actor/DynamicAccess.scala | 10 ++---
 .../src/main/scala/akka/actor/Extension.scala |  2 +-
 .../main/scala/akka/actor/FaultHandling.scala | 38 +++++++---------
 akka-actor/src/main/scala/akka/actor/IO.scala | 19 ++++----
 .../main/scala/akka/actor/TypedActor.scala    | 22 +++++-----
 .../akka/dispatch/AbstractDispatcher.scala    |  4 +-
 .../scala/akka/dispatch/Dispatchers.scala     |  2 +-
 .../src/main/scala/akka/event/EventBus.scala  |  5 ++-
 .../src/main/scala/akka/event/Logging.scala   |  9 ++--
 .../src/main/scala/akka/japi/JavaAPI.scala    |  7 +--
 .../scala/akka/routing/ConsistentHash.scala   |  6 +--
 .../akka/serialization/Serialization.scala    | 21 ++++-----
 .../scala/akka/util/SubclassifiedIndex.scala  |  6 ++-
 .../akka/camel/ConcurrentActivationTest.scala | 11 +++--
 .../src/main/scala/akka/cluster/Cluster.scala |  2 +-
 .../cluster/ClusterMetricsCollector.scala     |  2 +-
 ...ientDowningNodeThatIsUnreachableSpec.scala |  5 ++-
 .../ClientDowningNodeThatIsUpSpec.scala       |  5 ++-
 ...aderDowningNodeThatIsUnreachableSpec.scala |  9 ++--
 .../akka/cluster/LeaderElectionSpec.scala     |  3 +-
 .../akka/cluster/MultiNodeClusterSpec.scala   | 35 +++++++--------
 .../akka/cluster/SingletonClusterSpec.scala   |  3 +-
 .../scala/akka/cluster/SplitBrainSpec.scala   |  7 +--
 .../UnreachableNodeRejoinsClusterSpec.scala   |  7 +--
 .../cluster/AccrualFailureDetectorSpec.scala  |  6 +--
 .../akka/cluster/MetricsCollectorSpec.scala   | 13 +++---
 .../docs/actor/FaultHandlingTestBase.java     |  4 +-
 .../jrouting/CustomRouterDocTestBase.java     |  3 +-
 .../scala/code/docs/actor/FSMDocSpec.scala    | 11 ++---
 .../code/docs/testkit/TestKitUsageSpec.scala  |  7 +--
 .../code/docs/zeromq/ZeromqDocSpec.scala      | 12 ++---
 .../src/main/scala/akka/kernel/Main.scala     |  7 +--
 .../blueprint/NamespaceHandlerTest.scala      |  6 +--
 .../akka/osgi/ActorSystemActivatorTest.scala  |  6 ++-
 .../scala/akka/osgi/PojoSRTestSupport.scala   | 16 +++----
 .../NetworkFailureInjector.scala              | 18 ++++----
 .../akka/remote/testconductor/Player.scala    | 20 ++++-----
 .../akka/remote/testkit/MultiNodeSpec.scala   | 24 +++++-----
 .../akka/remote/RemoteActorRefProvider.scala  |  2 +-
 .../remote/netty/NettyRemoteSupport.scala     | 11 ++---
 .../provider/InternetSeedGenerator.scala      |  5 ++-
 .../scala/akka/testkit/TestActorRef.scala     |  2 +-
 .../akka/testkit/TestEventListener.scala      | 19 ++++----
 .../src/main/scala/akka/testkit/TestKit.scala | 44 +++++++++----------
 .../src/main/scala/akka/testkit/package.scala |  8 ++--
 .../UntypedCoordinatedIncrementTest.java      |  4 +-
 .../transactor/UntypedTransactorTest.java     |  4 +-
 .../transactor/CoordinatedIncrementSpec.scala |  7 +--
 .../akka/transactor/FickleFriendsSpec.scala   | 15 ++++---
 .../akka/transactor/TransactorSpec.scala      |  5 ++-
 .../akka/zeromq/ConcurrentSocketActor.scala   | 13 +++---
 .../main/scala/akka/zeromq/SocketOption.scala | 32 +++++++-------
 .../akka/zeromq/ZMQMessageDeserializer.scala  |  9 ++--
 .../scala/akka/zeromq/ZeroMQExtension.scala   |  4 +-
 .../zeromq/ConcurrentSocketActorSpec.scala    |  8 ++--
 65 files changed, 375 insertions(+), 350 deletions(-)

diff --git a/akka-actor-tests/src/test/scala/akka/actor/RelativeActorPathSpec.scala b/akka-actor-tests/src/test/scala/akka/actor/RelativeActorPathSpec.scala
index 179f4aa92c..6870a36125 100644
--- a/akka-actor-tests/src/test/scala/akka/actor/RelativeActorPathSpec.scala
+++ b/akka-actor-tests/src/test/scala/akka/actor/RelativeActorPathSpec.scala
@@ -6,24 +6,22 @@ package akka.actor
 import org.scalatest.WordSpec
 import org.scalatest.matchers.MustMatchers
 import java.net.URLEncoder
+import scala.collection.immutable
 
 class RelativeActorPathSpec extends WordSpec with MustMatchers {
 
-  def elements(path: String): Seq[String] = path match {
-    case RelativeActorPath(elem) ⇒ elem.toSeq
-    case _                       ⇒ Nil
-  }
+  def elements(path: String): immutable.Seq[String] = RelativeActorPath.unapply(path).getOrElse(Nil)
 
   "RelativeActorPath" must {
     "match single name" in {
-      elements("foo") must be(Seq("foo"))
+      elements("foo") must be(List("foo"))
     }
     "match path separated names" in {
-      elements("foo/bar/baz") must be(Seq("foo", "bar", "baz"))
+      elements("foo/bar/baz") must be(List("foo", "bar", "baz"))
     }
     "match url encoded name" in {
       val name = URLEncoder.encode("akka://ClusterSystem@127.0.0.1:2552", "UTF-8")
-      elements(name) must be(Seq(name))
+      elements(name) must be(List(name))
     }
   }
 }
diff --git a/akka-actor-tests/src/test/scala/akka/actor/TypedActorSpec.scala b/akka-actor-tests/src/test/scala/akka/actor/TypedActorSpec.scala
index 040c8e6211..201b6c6949 100644
--- a/akka-actor-tests/src/test/scala/akka/actor/TypedActorSpec.scala
+++ b/akka-actor-tests/src/test/scala/akka/actor/TypedActorSpec.scala
@@ -5,18 +5,19 @@ package akka.actor
 
 import language.postfixOps
 import org.scalatest.{ BeforeAndAfterAll, BeforeAndAfterEach }
-import akka.util.Timeout
+import scala.annotation.tailrec
+import scala.collection.immutable
 import scala.concurrent.{ Await, Future, Promise }
 import scala.concurrent.duration._
-import java.util.concurrent.atomic.AtomicReference
-import annotation.tailrec
 import akka.testkit.{ EventFilter, filterEvents, AkkaSpec }
+import akka.util.Timeout
 import akka.japi.{ Option ⇒ JOption }
 import akka.testkit.DefaultTimeout
-import akka.dispatch.{ Dispatchers }
+import akka.dispatch.Dispatchers
 import akka.pattern.ask
 import akka.serialization.JavaSerializer
 import akka.actor.TypedActor._
+import java.util.concurrent.atomic.AtomicReference
 import java.lang.IllegalStateException
 import java.util.concurrent.{ TimeoutException, TimeUnit, CountDownLatch }
 
@@ -35,9 +36,9 @@ object TypedActorSpec {
     }
     """
 
-  class CyclicIterator[T](val items: Seq[T]) extends Iterator[T] {
+  class CyclicIterator[T](val items: immutable.Seq[T]) extends Iterator[T] {
 
-    private[this] val current: AtomicReference[Seq[T]] = new AtomicReference(items)
+    private[this] val current = new AtomicReference(items)
 
     def hasNext = items != Nil
 
diff --git a/akka-actor-tests/src/test/scala/akka/performance/workbench/BenchResultRepository.scala b/akka-actor-tests/src/test/scala/akka/performance/workbench/BenchResultRepository.scala
index 1cccd19417..7bc3fec9d1 100644
--- a/akka-actor-tests/src/test/scala/akka/performance/workbench/BenchResultRepository.scala
+++ b/akka-actor-tests/src/test/scala/akka/performance/workbench/BenchResultRepository.scala
@@ -12,17 +12,18 @@ import java.io.PrintWriter
 import java.text.SimpleDateFormat
 import java.util.Date
 import scala.collection.mutable.{ Map ⇒ MutableMap }
+import scala.collection.immutable
 import akka.actor.ActorSystem
 import akka.event.Logging
 
 trait BenchResultRepository {
   def add(stats: Stats)
 
-  def get(name: String): Seq[Stats]
+  def get(name: String): immutable.Seq[Stats]
 
   def get(name: String, load: Int): Option[Stats]
 
-  def getWithHistorical(name: String, load: Int): Seq[Stats]
+  def getWithHistorical(name: String, load: Int): immutable.Seq[Stats]
 
   def isBaseline(stats: Stats): Boolean
 
@@ -38,9 +39,9 @@ object BenchResultRepository {
 }
 
 class FileBenchResultRepository extends BenchResultRepository {
-  private val statsByName = MutableMap[String, Seq[Stats]]()
+  private val statsByName = MutableMap[String, immutable.Seq[Stats]]()
   private val baselineStats = MutableMap[Key, Stats]()
-  private val historicalStats = MutableMap[Key, Seq[Stats]]()
+  private val historicalStats = MutableMap[Key, immutable.Seq[Stats]]()
   private def resultDir = BenchmarkConfig.config.getString("benchmark.resultDir")
   private val serDir = resultDir + "/ser"
   private def serDirExists: Boolean = new File(serDir).exists
@@ -51,13 +52,13 @@ class FileBenchResultRepository extends BenchResultRepository {
   case class Key(name: String, load: Int)
 
   def add(stats: Stats): Unit = synchronized {
-    val values = statsByName.getOrElseUpdate(stats.name, IndexedSeq.empty)
+    val values = statsByName.getOrElseUpdate(stats.name, Vector.empty)
     statsByName(stats.name) = values :+ stats
     save(stats)
   }
 
-  def get(name: String): Seq[Stats] = synchronized {
-    statsByName.getOrElse(name, IndexedSeq.empty)
+  def get(name: String): immutable.Seq[Stats] = synchronized {
+    statsByName.getOrElse(name, Vector.empty)
   }
 
   def get(name: String, load: Int): Option[Stats] = synchronized {
@@ -68,13 +69,13 @@ class FileBenchResultRepository extends BenchResultRepository {
     baselineStats.get(Key(stats.name, stats.load)) == Some(stats)
   }
 
-  def getWithHistorical(name: String, load: Int): Seq[Stats] = synchronized {
+  def getWithHistorical(name: String, load: Int): immutable.Seq[Stats] = synchronized {
     val key = Key(name, load)
-    val historical = historicalStats.getOrElse(key, IndexedSeq.empty)
+    val historical = historicalStats.getOrElse(key, Vector.empty)
     val baseline = baselineStats.get(key)
     val current = get(name, load)
 
-    val limited = (IndexedSeq.empty ++ historical ++ baseline ++ current).takeRight(maxHistorical)
+    val limited = (Vector.empty ++ historical ++ baseline ++ current).takeRight(maxHistorical)
     limited.sortBy(_.timestamp)
   }
 
@@ -94,7 +95,7 @@ class FileBenchResultRepository extends BenchResultRepository {
       }
       val historical = load(historicalFiles)
       for (h ← historical) {
-        val values = historicalStats.getOrElseUpdate(Key(h.name, h.load), IndexedSeq.empty)
+        val values = historicalStats.getOrElseUpdate(Key(h.name, h.load), Vector.empty)
         historicalStats(Key(h.name, h.load)) = values :+ h
       }
     }
@@ -120,7 +121,7 @@ class FileBenchResultRepository extends BenchResultRepository {
     }
   }
 
-  private def load(files: Iterable[File]): Seq[Stats] = {
+  private def load(files: Iterable[File]): immutable.Seq[Stats] = {
     val result =
       for (f ← files) yield {
         var in: ObjectInputStream = null
@@ -132,11 +133,11 @@ class FileBenchResultRepository extends BenchResultRepository {
           case e: Throwable ⇒
             None
         } finally {
-          if (in ne null) try { in.close() } catch { case ignore: Exception ⇒ }
+          if (in ne null) try in.close() catch { case ignore: Exception ⇒ }
         }
       }
 
-    result.flatten.toSeq.sortBy(_.timestamp)
+    result.flatten.toVector.sortBy(_.timestamp)
   }
 
   loadFiles()
diff --git a/akka-actor-tests/src/test/scala/akka/performance/workbench/GoogleChartBuilder.scala b/akka-actor-tests/src/test/scala/akka/performance/workbench/GoogleChartBuilder.scala
index 52b30ceee7..66b634d47f 100644
--- a/akka-actor-tests/src/test/scala/akka/performance/workbench/GoogleChartBuilder.scala
+++ b/akka-actor-tests/src/test/scala/akka/performance/workbench/GoogleChartBuilder.scala
@@ -3,7 +3,7 @@ package akka.performance.workbench
 import java.io.UnsupportedEncodingException
 import java.net.URLEncoder
 
-import scala.collection.immutable.TreeMap
+import scala.collection.immutable
 
 /**
  * Generates URLs to Google Chart API http://code.google.com/apis/chart/
@@ -16,7 +16,7 @@ object GoogleChartBuilder {
   /**
    * Builds a bar chart for tps in the statistics.
    */
-  def tpsChartUrl(statsByTimestamp: TreeMap[Long, Seq[Stats]], title: String, legend: Stats ⇒ String): String = {
+  def tpsChartUrl(statsByTimestamp: immutable.TreeMap[Long, Seq[Stats]], title: String, legend: Stats ⇒ String): String = {
     if (statsByTimestamp.isEmpty) ""
     else {
       val loads = statsByTimestamp.values.head.map(_.load)
@@ -46,7 +46,7 @@ object GoogleChartBuilder {
       //sb.append("&")
 
       // legend
-      val legendStats = statsByTimestamp.values.map(_.head).toSeq
+      val legendStats = statsByTimestamp.values.toVector.map(_.head)
       appendLegend(legendStats, sb, legend)
       sb.append("&")
       // bar spacing
@@ -60,10 +60,7 @@ object GoogleChartBuilder {
       val loadStr = loads.mkString(",")
       sb.append("chd=t:")
       val maxValue = allStats.map(_.tps).max
-      val tpsSeries: Iterable[String] =
-        for (statsSeq ← statsByTimestamp.values) yield {
-          statsSeq.map(_.tps).mkString(",")
-        }
+      val tpsSeries: Iterable[String] = for (statsSeq ← statsByTimestamp.values) yield statsSeq.map(_.tps).mkString(",")
       sb.append(tpsSeries.mkString("|"))
 
       // y range
@@ -83,7 +80,7 @@ object GoogleChartBuilder {
   /**
    * Builds a bar chart for all percentiles and the mean in the statistics.
    */
-  def percentilesAndMeanChartUrl(statistics: Seq[Stats], title: String, legend: Stats ⇒ String): String = {
+  def percentilesAndMeanChartUrl(statistics: immutable.Seq[Stats], title: String, legend: Stats ⇒ String): String = {
     if (statistics.isEmpty) ""
     else {
       val current = statistics.last
@@ -146,13 +143,13 @@ object GoogleChartBuilder {
     }
   }
 
-  private def percentileLabels(percentiles: TreeMap[Int, Long], sb: StringBuilder) {
+  private def percentileLabels(percentiles: immutable.TreeMap[Int, Long], sb: StringBuilder) {
     sb.append("chxl=1:|")
     val s = percentiles.keys.toList.map(_ + "%").mkString("|")
     sb.append(s)
   }
 
-  private def appendLegend(statistics: Seq[Stats], sb: StringBuilder, legend: Stats ⇒ String) {
+  private def appendLegend(statistics: immutable.Seq[Stats], sb: StringBuilder, legend: Stats ⇒ String) {
     val legends = statistics.map(legend(_))
     sb.append("chdl=")
     val s = legends.map(urlEncode(_)).mkString("|")
@@ -166,7 +163,7 @@ object GoogleChartBuilder {
     sb.append(s)
   }
 
-  private def dataSeries(allPercentiles: Seq[TreeMap[Int, Long]], meanValues: Seq[Double], sb: StringBuilder) {
+  private def dataSeries(allPercentiles: immutable.Seq[immutable.TreeMap[Int, Long]], meanValues: immutable.Seq[Double], sb: StringBuilder) {
     val percentileSeries =
       for {
         percentiles ← allPercentiles
@@ -181,7 +178,7 @@ object GoogleChartBuilder {
     sb.append(series.mkString("|"))
   }
 
-  private def dataSeries(values: Seq[Double], sb: StringBuilder) {
+  private def dataSeries(values: immutable.Seq[Double], sb: StringBuilder) {
     val series = values.map(formatDouble(_))
     sb.append(series.mkString("|"))
   }
@@ -198,7 +195,7 @@ object GoogleChartBuilder {
     }
   }
 
-  def latencyAndThroughputChartUrl(statistics: Seq[Stats], title: String): String = {
+  def latencyAndThroughputChartUrl(statistics: immutable.Seq[Stats], title: String): String = {
     if (statistics.isEmpty) ""
     else {
       val sb = new StringBuilder
diff --git a/akka-actor-tests/src/test/scala/akka/performance/workbench/Report.scala b/akka-actor-tests/src/test/scala/akka/performance/workbench/Report.scala
index 18f87702f3..f7974e6784 100644
--- a/akka-actor-tests/src/test/scala/akka/performance/workbench/Report.scala
+++ b/akka-actor-tests/src/test/scala/akka/performance/workbench/Report.scala
@@ -5,7 +5,7 @@ import java.text.SimpleDateFormat
 import java.util.Date
 import akka.actor.ActorSystem
 import akka.event.Logging
-import scala.collection.immutable.TreeMap
+import scala.collection.immutable
 
 class Report(
   system: ActorSystem,
@@ -19,7 +19,7 @@ class Report(
   val legendTimeFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm")
   val fileTimestampFormat = new SimpleDateFormat("yyyyMMddHHmmss")
 
-  def html(statistics: Seq[Stats]) {
+  def html(statistics: immutable.Seq[Stats]) {
 
     val current = statistics.last
     val sb = new StringBuilder
@@ -80,13 +80,13 @@ class Report(
     chartUrl
   }
 
-  def comparePercentilesAndMeanChart(stats: Stats): Seq[String] = {
+  def comparePercentilesAndMeanChart(stats: Stats): immutable.Seq[String] = {
     for {
-      compareName ← compareResultWith.toSeq
+      compareName ← compareResultWith.to[immutable.Seq]
       compareStats ← resultRepository.get(compareName, stats.load)
     } yield {
       val chartTitle = stats.name + " vs. " + compareName + ", " + stats.load + " clients" + ", Percentiles and Mean (microseconds)"
-      val chartUrl = GoogleChartBuilder.percentilesAndMeanChartUrl(Seq(compareStats, stats), chartTitle, _.name)
+      val chartUrl = GoogleChartBuilder.percentilesAndMeanChartUrl(List(compareStats, stats), chartTitle, _.name)
       chartUrl
     }
   }
@@ -102,17 +102,17 @@ class Report(
     }
   }
 
-  def compareWithHistoricalTpsChart(statistics: Seq[Stats]): Option[String] = {
+  def compareWithHistoricalTpsChart(statistics: immutable.Seq[Stats]): Option[String] = {
 
     if (statistics.isEmpty) {
       None
     } else {
       val histTimestamps = resultRepository.getWithHistorical(statistics.head.name, statistics.head.load).map(_.timestamp)
-      val statsByTimestamp = TreeMap[Long, Seq[Stats]]() ++
+      val statsByTimestamp = immutable.TreeMap[Long, Seq[Stats]]() ++
         (for (ts ← histTimestamps) yield {
           val seq =
             for (stats ← statistics) yield {
-              val withHistorical: Seq[Stats] = resultRepository.getWithHistorical(stats.name, stats.load)
+              val withHistorical: immutable.Seq[Stats] = resultRepository.getWithHistorical(stats.name, stats.load)
               val cell = withHistorical.find(_.timestamp == ts)
               cell.getOrElse(Stats(stats.name, stats.load, ts))
             }
@@ -131,7 +131,7 @@ class Report(
     chartUrl
   }
 
-  def formatResultsTable(statsSeq: Seq[Stats]): String = {
+  def formatResultsTable(statsSeq: immutable.Seq[Stats]): String = {
 
     val name = statsSeq.head.name
 
diff --git a/akka-actor/src/main/scala/akka/actor/ActorPath.scala b/akka-actor/src/main/scala/akka/actor/ActorPath.scala
index cc21e0de16..a20e8220b1 100644
--- a/akka-actor/src/main/scala/akka/actor/ActorPath.scala
+++ b/akka-actor/src/main/scala/akka/actor/ActorPath.scala
@@ -121,7 +121,7 @@ final case class RootActorPath(address: Address, name: String = "/") extends Act
     else addr + name
 
   override def compareTo(other: ActorPath): Int = other match {
-    case r: RootActorPath  ⇒ toString compareTo r.toString
+    case r: RootActorPath  ⇒ toString compareTo r.toString // FIXME make this cheaper by comparing address and name in isolation
     case c: ChildActorPath ⇒ 1
   }
 }
diff --git a/akka-actor/src/main/scala/akka/actor/ActorRefProvider.scala b/akka-actor/src/main/scala/akka/actor/ActorRefProvider.scala
index 8fa84b2978..a11da0c150 100644
--- a/akka-actor/src/main/scala/akka/actor/ActorRefProvider.scala
+++ b/akka-actor/src/main/scala/akka/actor/ActorRefProvider.scala
@@ -480,7 +480,7 @@ class LocalActorRefProvider(
   def registerExtraNames(_extras: Map[String, InternalActorRef]): Unit = extraNames ++= _extras
 
   private def guardianSupervisorStrategyConfigurator =
-    dynamicAccess.createInstanceFor[SupervisorStrategyConfigurator](settings.SupervisorStrategyClass, Seq()).get
+    dynamicAccess.createInstanceFor[SupervisorStrategyConfigurator](settings.SupervisorStrategyClass, Nil).get
 
   /**
    * Overridable supervision strategy to be used by the “/user” guardian.
diff --git a/akka-actor/src/main/scala/akka/actor/ActorSystem.scala b/akka-actor/src/main/scala/akka/actor/ActorSystem.scala
index 212ee9372d..b4309bcb5c 100644
--- a/akka-actor/src/main/scala/akka/actor/ActorSystem.scala
+++ b/akka-actor/src/main/scala/akka/actor/ActorSystem.scala
@@ -9,17 +9,17 @@ import akka.dispatch._
 import akka.pattern.ask
 import com.typesafe.config.{ Config, ConfigFactory }
 import scala.annotation.tailrec
-import scala.concurrent.duration.Duration
-import java.io.Closeable
+import scala.collection.immutable
+import scala.concurrent.duration.{ FiniteDuration, Duration }
 import scala.concurrent.{ Await, Awaitable, CanAwait, Future }
+import scala.util.{ Failure, Success }
 import scala.util.control.NonFatal
 import akka.util._
+import java.io.Closeable
 import akka.util.internal.{ HashedWheelTimer, ConcurrentIdentityHashMap }
 import java.util.concurrent.{ ThreadFactory, CountDownLatch, TimeoutException, RejectedExecutionException }
 import java.util.concurrent.TimeUnit.MILLISECONDS
 import akka.actor.dungeon.ChildrenContainer
-import scala.concurrent.duration.FiniteDuration
-import util.{ Failure, Success }
 
 object ActorSystem {
 
@@ -144,7 +144,7 @@ object ActorSystem {
 
     final val LogLevel: String = getString("akka.loglevel")
     final val StdoutLogLevel: String = getString("akka.stdout-loglevel")
-    final val EventHandlers: Seq[String] = getStringList("akka.event-handlers").asScala
+    final val EventHandlers: immutable.Seq[String] = getStringList("akka.event-handlers").asScala.to[Vector]
     final val EventHandlerStartTimeout: Timeout = Timeout(Duration(getMilliseconds("akka.event-handler-startup-timeout"), MILLISECONDS))
     final val LogConfigOnStart: Boolean = config.getBoolean("akka.log-config-on-start")
 
@@ -273,10 +273,8 @@ abstract class ActorSystem extends ActorRefFactory {
   /**
    * ''Java API'': Recursively create a descendant’s path by appending all child names.
    */
-  def descendant(names: java.lang.Iterable[String]): ActorPath = {
-    import scala.collection.JavaConverters._
-    /(names.asScala)
-  }
+  def descendant(names: java.lang.Iterable[String]): ActorPath =
+    /(scala.collection.JavaConverters.iterableAsScalaIterableConverter(names).asScala)
 
   /**
    * Start-up time in milliseconds since the epoch.
@@ -536,7 +534,7 @@ private[akka] class ActorSystemImpl(val name: String, applicationConfig: Config,
   val scheduler: Scheduler = createScheduler()
 
   val provider: ActorRefProvider = {
-    val arguments = Seq(
+    val arguments = Vector(
       classOf[String] -> name,
       classOf[Settings] -> settings,
       classOf[EventStream] -> eventStream,
@@ -676,15 +674,15 @@ private[akka] class ActorSystemImpl(val name: String, applicationConfig: Config,
   def hasExtension(ext: ExtensionId[_ <: Extension]): Boolean = findExtension(ext) != null
 
   private def loadExtensions() {
-    import scala.collection.JavaConverters.collectionAsScalaIterableConverter
-    settings.config.getStringList("akka.extensions").asScala foreach { fqcn ⇒
-      dynamicAccess.getObjectFor[AnyRef](fqcn) recoverWith { case _ ⇒ dynamicAccess.createInstanceFor[AnyRef](fqcn, Seq()) } match {
-        case Success(p: ExtensionIdProvider) ⇒ registerExtension(p.lookup())
-        case Success(p: ExtensionId[_])      ⇒ registerExtension(p)
-        case Success(other)                  ⇒ log.error("[{}] is not an 'ExtensionIdProvider' or 'ExtensionId', skipping...", fqcn)
-        case Failure(problem)                ⇒ log.error(problem, "While trying to load extension [{}], skipping...", fqcn)
+    scala.collection.JavaConverters.collectionAsScalaIterableConverter(
+      settings.config.getStringList("akka.extensions")).asScala foreach { fqcn ⇒
+        dynamicAccess.getObjectFor[AnyRef](fqcn) recoverWith { case _ ⇒ dynamicAccess.createInstanceFor[AnyRef](fqcn, Nil) } match {
+          case Success(p: ExtensionIdProvider) ⇒ registerExtension(p.lookup())
+          case Success(p: ExtensionId[_])      ⇒ registerExtension(p)
+          case Success(other)                  ⇒ log.error("[{}] is not an 'ExtensionIdProvider' or 'ExtensionId', skipping...", fqcn)
+          case Failure(problem)                ⇒ log.error(problem, "While trying to load extension [{}], skipping...", fqcn)
+        }
       }
-    }
   }
 
   override def toString: String = lookupRoot.path.root.address.toString
diff --git a/akka-actor/src/main/scala/akka/actor/Address.scala b/akka-actor/src/main/scala/akka/actor/Address.scala
index 7c87d696a4..b8f8a52e45 100644
--- a/akka-actor/src/main/scala/akka/actor/Address.scala
+++ b/akka-actor/src/main/scala/akka/actor/Address.scala
@@ -5,7 +5,8 @@ package akka.actor
 import java.net.URI
 import java.net.URISyntaxException
 import java.net.MalformedURLException
-import annotation.tailrec
+import scala.annotation.tailrec
+import scala.collection.immutable
 
 /**
  * The address specifies the physical location under which an Actor can be
@@ -71,7 +72,7 @@ private[akka] trait PathUtils {
 }
 
 object RelativeActorPath extends PathUtils {
-  def unapply(addr: String): Option[Iterable[String]] = {
+  def unapply(addr: String): Option[immutable.Seq[String]] = {
     try {
       val uri = new URI(addr)
       if (uri.isAbsolute) None
diff --git a/akka-actor/src/main/scala/akka/actor/Deployer.scala b/akka-actor/src/main/scala/akka/actor/Deployer.scala
index 06d3b01a1b..e74b54c320 100644
--- a/akka-actor/src/main/scala/akka/actor/Deployer.scala
+++ b/akka-actor/src/main/scala/akka/actor/Deployer.scala
@@ -160,7 +160,7 @@ private[akka] class Deployer(val settings: ActorSystem.Settings, val dynamicAcce
         val vnodes = deployment.getInt("virtual-nodes-factor")
         ConsistentHashingRouter(nrOfInstances, routees, resizer, virtualNodesFactor = vnodes)
       case fqn ⇒
-        val args = Seq(classOf[Config] -> deployment)
+        val args = List(classOf[Config] -> deployment)
         dynamicAccess.createInstanceFor[RouterConfig](fqn, args).recover({
           case exception ⇒ throw new IllegalArgumentException(
             ("Cannot instantiate router [%s], defined in [%s], " +
diff --git a/akka-actor/src/main/scala/akka/actor/DynamicAccess.scala b/akka-actor/src/main/scala/akka/actor/DynamicAccess.scala
index 7a73eb3b15..af891bc483 100644
--- a/akka-actor/src/main/scala/akka/actor/DynamicAccess.scala
+++ b/akka-actor/src/main/scala/akka/actor/DynamicAccess.scala
@@ -3,7 +3,7 @@
  */
 package akka.actor
 
-import scala.util.control.NonFatal
+import scala.collection.immutable
 import java.lang.reflect.InvocationTargetException
 import scala.reflect.ClassTag
 import scala.util.Try
@@ -25,7 +25,7 @@ abstract class DynamicAccess {
    * val obj = DynamicAccess.createInstanceFor(clazz, Seq(classOf[Config] -> config, classOf[String] -> name))
    * }}}
    */
-  def createInstanceFor[T: ClassTag](clazz: Class[_], args: Seq[(Class[_], AnyRef)]): Try[T]
+  def createInstanceFor[T: ClassTag](clazz: Class[_], args: immutable.Seq[(Class[_], AnyRef)]): Try[T]
 
   /**
    * Obtain a `Class[_]` object loaded with the right class loader (i.e. the one
@@ -40,7 +40,7 @@ abstract class DynamicAccess {
    * `args` argument. The exact usage of args depends on which type is requested,
    * see the relevant requesting code for details.
    */
-  def createInstanceFor[T: ClassTag](fqcn: String, args: Seq[(Class[_], AnyRef)]): Try[T]
+  def createInstanceFor[T: ClassTag](fqcn: String, args: immutable.Seq[(Class[_], AnyRef)]): Try[T]
 
   /**
    * Obtain the Scala “object” instance for the given fully-qualified class name, if there is one.
@@ -70,7 +70,7 @@ class ReflectiveDynamicAccess(val classLoader: ClassLoader) extends DynamicAcces
       if (t.isAssignableFrom(c)) c else throw new ClassCastException(t + " is not assignable from " + c)
     })
 
-  override def createInstanceFor[T: ClassTag](clazz: Class[_], args: Seq[(Class[_], AnyRef)]): Try[T] =
+  override def createInstanceFor[T: ClassTag](clazz: Class[_], args: immutable.Seq[(Class[_], AnyRef)]): Try[T] =
     Try {
       val types = args.map(_._1).toArray
       val values = args.map(_._2).toArray
@@ -81,7 +81,7 @@ class ReflectiveDynamicAccess(val classLoader: ClassLoader) extends DynamicAcces
       if (t.isInstance(obj)) obj.asInstanceOf[T] else throw new ClassCastException(clazz.getName + " is not a subtype of " + t)
     } recover { case i: InvocationTargetException if i.getTargetException ne null ⇒ throw i.getTargetException }
 
-  override def createInstanceFor[T: ClassTag](fqcn: String, args: Seq[(Class[_], AnyRef)]): Try[T] =
+  override def createInstanceFor[T: ClassTag](fqcn: String, args: immutable.Seq[(Class[_], AnyRef)]): Try[T] =
     getClassFor(fqcn) flatMap { c ⇒ createInstanceFor(c, args) }
 
   override def getObjectFor[T: ClassTag](fqcn: String): Try[T] = {
diff --git a/akka-actor/src/main/scala/akka/actor/Extension.scala b/akka-actor/src/main/scala/akka/actor/Extension.scala
index 6fab4ceb07..707c07982a 100644
--- a/akka-actor/src/main/scala/akka/actor/Extension.scala
+++ b/akka-actor/src/main/scala/akka/actor/Extension.scala
@@ -98,5 +98,5 @@ abstract class ExtensionKey[T <: Extension](implicit m: ClassTag[T]) extends Ext
   def this(clazz: Class[T]) = this()(ClassTag(clazz))
 
   override def lookup(): ExtensionId[T] = this
-  def createExtension(system: ExtendedActorSystem): T = system.dynamicAccess.createInstanceFor[T](m.runtimeClass, Seq(classOf[ExtendedActorSystem] -> system)).get
+  def createExtension(system: ExtendedActorSystem): T = system.dynamicAccess.createInstanceFor[T](m.runtimeClass, List(classOf[ExtendedActorSystem] -> system)).get
 }
diff --git a/akka-actor/src/main/scala/akka/actor/FaultHandling.scala b/akka-actor/src/main/scala/akka/actor/FaultHandling.scala
index d72389ae5e..444618df00 100644
--- a/akka-actor/src/main/scala/akka/actor/FaultHandling.scala
+++ b/akka-actor/src/main/scala/akka/actor/FaultHandling.scala
@@ -5,9 +5,10 @@ package akka.actor
 
 import language.implicitConversions
 
+import java.lang.{ Iterable ⇒ JIterable }
 import java.util.concurrent.TimeUnit
 import scala.collection.mutable.ArrayBuffer
-import java.lang.{ Iterable ⇒ JIterable }
+import scala.collection.immutable
 import scala.concurrent.duration.Duration
 /**
  * INTERNAL API
@@ -170,7 +171,7 @@ object SupervisorStrategy extends SupervisorStrategyLowPriorityImplicits {
    * Implicit conversion from `Seq` of Throwables to a `Decider`.
    * This maps the given Throwables to restarts, otherwise escalates.
    */
-  implicit def seqThrowable2Decider(trapExit: Seq[Class[_ <: Throwable]]): Decider = makeDecider(trapExit)
+  implicit def seqThrowable2Decider(trapExit: immutable.Seq[Class[_ <: Throwable]]): Decider = makeImmutableDecider(trapExit)
 
   type Decider = PartialFunction[Throwable, Directive]
   type JDecider = akka.japi.Function[Throwable, Directive]
@@ -180,23 +181,21 @@ object SupervisorStrategy extends SupervisorStrategyLowPriorityImplicits {
    * Decider builder which just checks whether one of
    * the given Throwables matches the cause and restarts, otherwise escalates.
    */
-  def makeDecider(trapExit: Array[Class[_]]): Decider =
-    { case x ⇒ if (trapExit exists (_ isInstance x)) Restart else Escalate }
-
+  def makeDecider(trapExit: immutable.Seq[Class[_ <: Throwable]]): Decider = makeImmutableDecider(trapExit)
   /**
    * Decider builder which just checks whether one of
    * the given Throwables matches the cause and restarts, otherwise escalates.
    */
-  def makeDecider(trapExit: Seq[Class[_ <: Throwable]]): Decider =
-    { case x ⇒ if (trapExit exists (_ isInstance x)) Restart else Escalate }
+  def makeDecider(trapExit: JIterable[Class[_ <: Throwable]]): Decider =
+    makeImmutableDecider(scala.collection.JavaConverters.iterableAsScalaIterableConverter(trapExit).asScala)
 
-  /**
-   * Decider builder which just checks whether one of
-   * the given Throwables matches the cause and restarts, otherwise escalates.
-   */
-  def makeDecider(trapExit: JIterable[Class[_ <: Throwable]]): Decider = {
-    import scala.collection.JavaConverters.iterableAsScalaIterableConverter
-    makeDecider(trapExit.asScala.toSeq)
+  private[this] def makeImmutableDecider(trapExit: Iterable[Class[_]]): Decider = {
+    val traps = trapExit match { // This is the sad, awkward, truth
+      case s: immutable.Seq[_] ⇒ s.asInstanceOf[immutable.Seq[Class[_]]]
+      case other               ⇒ other.to[immutable.Seq]
+    }
+
+    { case x ⇒ if (traps exists (_ isInstance x)) Restart else Escalate }
   }
 
   /**
@@ -222,14 +221,14 @@ object SupervisorStrategy extends SupervisorStrategyLowPriorityImplicits {
    *
    * INTERNAL API
    */
-  private[akka] def sort(in: Iterable[CauseDirective]): Seq[CauseDirective] =
+  private[akka] def sort(in: Iterable[CauseDirective]): immutable.Seq[CauseDirective] =
     (new ArrayBuffer[CauseDirective](in.size) /: in) { (buf, ca) ⇒
       buf.indexWhere(_._1 isAssignableFrom ca._1) match {
         case -1 ⇒ buf append ca
         case x  ⇒ buf insert (x, ca)
       }
       buf
-    }
+    }.to[immutable.Seq]
 
   private[akka] def withinTimeRangeOption(withinTimeRange: Duration): Option[Duration] =
     if (withinTimeRange.isFinite && withinTimeRange >= Duration.Zero) Some(withinTimeRange) else None
@@ -338,10 +337,6 @@ case class AllForOneStrategy(maxNrOfRetries: Int = -1, withinTimeRange: Duration
 
   def this(maxNrOfRetries: Int, withinTimeRange: Duration, trapExit: JIterable[Class[_ <: Throwable]]) =
     this(maxNrOfRetries, withinTimeRange)(SupervisorStrategy.makeDecider(trapExit))
-
-  def this(maxNrOfRetries: Int, withinTimeRange: Duration, trapExit: Array[Class[_]]) =
-    this(maxNrOfRetries, withinTimeRange)(SupervisorStrategy.makeDecider(trapExit))
-
   /*
    *  this is a performance optimization to avoid re-allocating the pairs upon
    *  every call to requestRestartPermission, assuming that strategies are shared
@@ -380,9 +375,6 @@ case class OneForOneStrategy(maxNrOfRetries: Int = -1, withinTimeRange: Duration
   def this(maxNrOfRetries: Int, withinTimeRange: Duration, trapExit: JIterable[Class[_ <: Throwable]]) =
     this(maxNrOfRetries, withinTimeRange)(SupervisorStrategy.makeDecider(trapExit))
 
-  def this(maxNrOfRetries: Int, withinTimeRange: Duration, trapExit: Array[Class[_]]) =
-    this(maxNrOfRetries, withinTimeRange)(SupervisorStrategy.makeDecider(trapExit))
-
   /*
    *  this is a performance optimization to avoid re-allocating the pairs upon
    *  every call to requestRestartPermission, assuming that strategies are shared
diff --git a/akka-actor/src/main/scala/akka/actor/IO.scala b/akka-actor/src/main/scala/akka/actor/IO.scala
index 635afe2a58..e1dedb3ba2 100644
--- a/akka-actor/src/main/scala/akka/actor/IO.scala
+++ b/akka-actor/src/main/scala/akka/actor/IO.scala
@@ -6,6 +6,7 @@ package akka.actor
 import language.higherKinds
 import language.postfixOps
 
+import scala.collection.immutable
 import scala.concurrent.{ ExecutionContext, Future }
 import scala.concurrent.duration.Duration
 import scala.util.control.NonFatal
@@ -122,7 +123,7 @@ object IO {
      * @return a new SocketHandle that can be used to perform actions on the
      *         new connection's SocketChannel.
      */
-    def accept(options: Seq[SocketOption] = Seq.empty)(implicit socketOwner: ActorRef): SocketHandle = {
+    def accept(options: immutable.Seq[SocketOption] = Nil)(implicit socketOwner: ActorRef): SocketHandle = {
       val socket = SocketHandle(socketOwner, ioManager)
       ioManager ! Accept(socket, this, options)
       socket
@@ -250,7 +251,7 @@ object IO {
    *
    * Normally sent using IOManager.listen()
    */
-  case class Listen(server: ServerHandle, address: SocketAddress, options: Seq[ServerSocketOption] = Seq.empty) extends IOMessage
+  case class Listen(server: ServerHandle, address: SocketAddress, options: immutable.Seq[ServerSocketOption] = Nil) extends IOMessage
 
   /**
    * Message from an [[akka.actor.IOManager]] that the ServerSocketChannel is
@@ -272,7 +273,7 @@ object IO {
    *
    * Normally sent using [[akka.actor.IO.ServerHandle]].accept()
    */
-  case class Accept(socket: SocketHandle, server: ServerHandle, options: Seq[SocketOption] = Seq.empty) extends IOMessage
+  case class Accept(socket: SocketHandle, server: ServerHandle, options: immutable.Seq[SocketOption] = Nil) extends IOMessage
 
   /**
    * Message to an [[akka.actor.IOManager]] to create a SocketChannel connected
@@ -280,7 +281,7 @@ object IO {
    *
    * Normally sent using IOManager.connect()
    */
-  case class Connect(socket: SocketHandle, address: SocketAddress, options: Seq[SocketOption] = Seq.empty) extends IOMessage
+  case class Connect(socket: SocketHandle, address: SocketAddress, options: immutable.Seq[SocketOption] = Nil) extends IOMessage
 
   /**
    * Message from an [[akka.actor.IOManager]] that the SocketChannel has
@@ -832,7 +833,7 @@ final class IOManager private (system: ExtendedActorSystem) extends Extension {
    * @param option Seq of [[akka.actor.IO.ServerSocketOptions]] to setup on socket
    * @return a [[akka.actor.IO.ServerHandle]] to uniquely identify the created socket
    */
-  def listen(address: SocketAddress, options: Seq[IO.ServerSocketOption])(implicit owner: ActorRef): IO.ServerHandle = {
+  def listen(address: SocketAddress, options: immutable.Seq[IO.ServerSocketOption])(implicit owner: ActorRef): IO.ServerHandle = {
     val server = IO.ServerHandle(owner, actor)
     actor ! IO.Listen(server, address, options)
     server
@@ -847,7 +848,7 @@ final class IOManager private (system: ExtendedActorSystem) extends Extension {
    * @param owner the ActorRef that will receive messages from the IOManagerActor
    * @return a [[akka.actor.IO.ServerHandle]] to uniquely identify the created socket
    */
-  def listen(address: SocketAddress)(implicit owner: ActorRef): IO.ServerHandle = listen(address, Seq.empty)
+  def listen(address: SocketAddress)(implicit owner: ActorRef): IO.ServerHandle = listen(address, Nil)
 
   /**
    * Create a ServerSocketChannel listening on a host and port. Messages will
@@ -860,7 +861,7 @@ final class IOManager private (system: ExtendedActorSystem) extends Extension {
    * @param owner the ActorRef that will receive messages from the IOManagerActor
    * @return a [[akka.actor.IO.ServerHandle]] to uniquely identify the created socket
    */
-  def listen(host: String, port: Int, options: Seq[IO.ServerSocketOption] = Seq.empty)(implicit owner: ActorRef): IO.ServerHandle =
+  def listen(host: String, port: Int, options: immutable.Seq[IO.ServerSocketOption] = Nil)(implicit owner: ActorRef): IO.ServerHandle =
     listen(new InetSocketAddress(host, port), options)(owner)
 
   /**
@@ -873,7 +874,7 @@ final class IOManager private (system: ExtendedActorSystem) extends Extension {
    * @param owner the ActorRef that will receive messages from the IOManagerActor
    * @return a [[akka.actor.IO.SocketHandle]] to uniquely identify the created socket
    */
-  def connect(address: SocketAddress, options: Seq[IO.SocketOption] = Seq.empty)(implicit owner: ActorRef): IO.SocketHandle = {
+  def connect(address: SocketAddress, options: immutable.Seq[IO.SocketOption] = Nil)(implicit owner: ActorRef): IO.SocketHandle = {
     val socket = IO.SocketHandle(owner, actor)
     actor ! IO.Connect(socket, address, options)
     socket
@@ -991,7 +992,7 @@ final class IOManagerActor(val settings: Settings) extends Actor with ActorLoggi
 
   private def forwardFailure(f: ⇒ Unit): Unit = try f catch { case NonFatal(e) ⇒ sender ! Status.Failure(e) }
 
-  private def setSocketOptions(socket: java.net.Socket, options: Seq[IO.SocketOption]) {
+  private def setSocketOptions(socket: java.net.Socket, options: immutable.Seq[IO.SocketOption]) {
     options foreach {
       case IO.KeepAlive(on)           ⇒ forwardFailure(socket.setKeepAlive(on))
       case IO.OOBInline(on)           ⇒ forwardFailure(socket.setOOBInline(on))
diff --git a/akka-actor/src/main/scala/akka/actor/TypedActor.scala b/akka-actor/src/main/scala/akka/actor/TypedActor.scala
index 6dbe48ba40..f7b0e853ef 100644
--- a/akka-actor/src/main/scala/akka/actor/TypedActor.scala
+++ b/akka-actor/src/main/scala/akka/actor/TypedActor.scala
@@ -4,22 +4,24 @@
 package akka.actor
 
 import language.existentials
-import akka.japi.{ Creator, Option ⇒ JOption }
-import java.lang.reflect.{ InvocationTargetException, Method, InvocationHandler, Proxy }
-import akka.util.Timeout
+
 import scala.util.control.NonFatal
+import scala.util.{ Try, Success, Failure }
+import scala.collection.immutable
+import scala.concurrent.duration.FiniteDuration
 import scala.concurrent.duration.Duration
+import scala.reflect.ClassTag
 import scala.concurrent.{ Await, Future }
+import akka.japi.{ Creator, Option ⇒ JOption }
+import akka.util.Timeout
 import akka.util.Reflect.instantiator
+import akka.serialization.{ JavaSerializer, SerializationExtension }
 import akka.dispatch._
 import java.util.concurrent.atomic.{ AtomicReference ⇒ AtomVar }
 import java.util.concurrent.TimeoutException
 import java.util.concurrent.TimeUnit.MILLISECONDS
-import scala.reflect.ClassTag
-import akka.serialization.{ JavaSerializer, SerializationExtension }
 import java.io.ObjectStreamException
-import scala.util.{ Try, Success, Failure }
-import scala.concurrent.duration.FiniteDuration
+import java.lang.reflect.{ InvocationTargetException, Method, InvocationHandler, Proxy }
 
 /**
  * A TypedActorFactory is something that can created TypedActor instances.
@@ -439,8 +441,8 @@ object TypedProps {
    * @return a sequence of interfaces that the specified class implements,
    * or a sequence containing only itself, if itself is an interface.
    */
-  def extractInterfaces(clazz: Class[_]): Seq[Class[_]] =
-    if (clazz.isInterface) Seq[Class[_]](clazz) else clazz.getInterfaces.toList
+  def extractInterfaces(clazz: Class[_]): immutable.Seq[Class[_]] =
+    if (clazz.isInterface) List[Class[_]](clazz) else clazz.getInterfaces.to[List]
 
   /**
    * Uses the supplied class as the factory for the TypedActor implementation,
@@ -489,7 +491,7 @@ object TypedProps {
  */
 @SerialVersionUID(1L)
 case class TypedProps[T <: AnyRef] protected[TypedProps] (
-  interfaces: Seq[Class[_]],
+  interfaces: immutable.Seq[Class[_]],
   creator: () ⇒ T,
   dispatcher: String = TypedProps.defaultDispatcherId,
   deploy: Deploy = Props.defaultDeploy,
diff --git a/akka-actor/src/main/scala/akka/dispatch/AbstractDispatcher.scala b/akka-actor/src/main/scala/akka/dispatch/AbstractDispatcher.scala
index 36afc8a24c..1b9de36e77 100644
--- a/akka-actor/src/main/scala/akka/dispatch/AbstractDispatcher.scala
+++ b/akka-actor/src/main/scala/akka/dispatch/AbstractDispatcher.scala
@@ -420,7 +420,7 @@ abstract class MessageDispatcherConfigurator(val config: Config, val prerequisit
       case "unbounded" ⇒ UnboundedMailbox()
       case "bounded"   ⇒ new BoundedMailbox(prerequisites.settings, config)
       case fqcn ⇒
-        val args = Seq(classOf[ActorSystem.Settings] -> prerequisites.settings, classOf[Config] -> config)
+        val args = List(classOf[ActorSystem.Settings] -> prerequisites.settings, classOf[Config] -> config)
         prerequisites.dynamicAccess.createInstanceFor[MailboxType](fqcn, args).recover({
           case exception ⇒
             throw new IllegalArgumentException(
@@ -436,7 +436,7 @@ abstract class MessageDispatcherConfigurator(val config: Config, val prerequisit
       case null | "" | "fork-join-executor" ⇒ new ForkJoinExecutorConfigurator(config.getConfig("fork-join-executor"), prerequisites)
       case "thread-pool-executor"           ⇒ new ThreadPoolExecutorConfigurator(config.getConfig("thread-pool-executor"), prerequisites)
       case fqcn ⇒
-        val args = Seq(
+        val args = List(
           classOf[Config] -> config,
           classOf[DispatcherPrerequisites] -> prerequisites)
         prerequisites.dynamicAccess.createInstanceFor[ExecutorServiceConfigurator](fqcn, args).recover({
diff --git a/akka-actor/src/main/scala/akka/dispatch/Dispatchers.scala b/akka-actor/src/main/scala/akka/dispatch/Dispatchers.scala
index e1ae0ae50b..910a5ceed5 100644
--- a/akka-actor/src/main/scala/akka/dispatch/Dispatchers.scala
+++ b/akka-actor/src/main/scala/akka/dispatch/Dispatchers.scala
@@ -147,7 +147,7 @@ class Dispatchers(val settings: ActorSystem.Settings, val prerequisites: Dispatc
       case "BalancingDispatcher" ⇒ new BalancingDispatcherConfigurator(cfg, prerequisites)
       case "PinnedDispatcher"    ⇒ new PinnedDispatcherConfigurator(cfg, prerequisites)
       case fqn ⇒
-        val args = Seq(classOf[Config] -> cfg, classOf[DispatcherPrerequisites] -> prerequisites)
+        val args = List(classOf[Config] -> cfg, classOf[DispatcherPrerequisites] -> prerequisites)
         prerequisites.dynamicAccess.createInstanceFor[MessageDispatcherConfigurator](fqn, args).recover({
           case exception ⇒
             throw new IllegalArgumentException(
diff --git a/akka-actor/src/main/scala/akka/event/EventBus.scala b/akka-actor/src/main/scala/akka/event/EventBus.scala
index cb83fbe806..403f7a0dfd 100644
--- a/akka-actor/src/main/scala/akka/event/EventBus.scala
+++ b/akka-actor/src/main/scala/akka/event/EventBus.scala
@@ -10,6 +10,7 @@ import java.util.concurrent.ConcurrentSkipListSet
 import java.util.Comparator
 import akka.util.{ Subclassification, SubclassifiedIndex }
 import scala.collection.immutable.TreeSet
+import scala.collection.immutable
 
 /**
  * Represents the base type for EventBuses
@@ -167,12 +168,12 @@ trait SubchannelClassification { this: EventBus ⇒
     recv foreach (publish(event, _))
   }
 
-  private def removeFromCache(changes: Seq[(Classifier, Set[Subscriber])]): Unit =
+  private def removeFromCache(changes: immutable.Seq[(Classifier, Set[Subscriber])]): Unit =
     cache = (cache /: changes) {
       case (m, (c, cs)) ⇒ m.updated(c, m.getOrElse(c, Set.empty[Subscriber]) -- cs)
     }
 
-  private def addToCache(changes: Seq[(Classifier, Set[Subscriber])]): Unit =
+  private def addToCache(changes: immutable.Seq[(Classifier, Set[Subscriber])]): Unit =
     cache = (cache /: changes) {
       case (m, (c, cs)) ⇒ m.updated(c, m.getOrElse(c, Set.empty[Subscriber]) ++ cs)
     }
diff --git a/akka-actor/src/main/scala/akka/event/Logging.scala b/akka-actor/src/main/scala/akka/event/Logging.scala
index c9286cf2c9..dbd561514d 100644
--- a/akka-actor/src/main/scala/akka/event/Logging.scala
+++ b/akka-actor/src/main/scala/akka/event/Logging.scala
@@ -9,12 +9,13 @@ import akka.actor._
 import akka.{ ConfigurationException, AkkaException }
 import akka.actor.ActorSystem.Settings
 import akka.util.{ Timeout, ReentrantGuard }
-import scala.concurrent.duration._
 import java.util.concurrent.atomic.AtomicInteger
-import scala.util.control.NoStackTrace
 import java.util.concurrent.TimeoutException
+import scala.annotation.implicitNotFound
+import scala.collection.immutable
+import scala.concurrent.duration._
 import scala.concurrent.Await
-import annotation.implicitNotFound
+import scala.util.control.NoStackTrace
 
 /**
  * This trait brings log level handling to the EventStream: it reads the log
@@ -448,7 +449,7 @@ object Logging {
   }
 
   // these type ascriptions/casts are necessary to avoid CCEs during construction while retaining correct type
-  val AllLogLevels: Seq[LogLevel] = Seq(ErrorLevel, WarningLevel, InfoLevel, DebugLevel)
+  val AllLogLevels: immutable.Seq[LogLevel] = Vector(ErrorLevel, WarningLevel, InfoLevel, DebugLevel)
 
   /**
    * Obtain LoggingAdapter for the given actor system and source object. This
diff --git a/akka-actor/src/main/scala/akka/japi/JavaAPI.scala b/akka-actor/src/main/scala/akka/japi/JavaAPI.scala
index ee2a688345..fda674a02c 100644
--- a/akka-actor/src/main/scala/akka/japi/JavaAPI.scala
+++ b/akka-actor/src/main/scala/akka/japi/JavaAPI.scala
@@ -5,7 +5,8 @@
 package akka.japi
 
 import language.implicitConversions
-import scala.Some
+
+import scala.collection.immutable
 import scala.reflect.ClassTag
 import scala.util.control.NoStackTrace
 import scala.runtime.AbstractPartialFunction
@@ -176,7 +177,7 @@ object Option {
 object Util {
   def classTag[T](clazz: Class[T]): ClassTag[T] = ClassTag(clazz)
 
-  def arrayToSeq[T](arr: Array[T]): Seq[T] = arr.toSeq
+  def arrayToSeq[T](arr: Array[T]): immutable.Seq[T] = arr.to[immutable.Seq]
 
-  def arrayToSeq(classes: Array[Class[_]]): Seq[Class[_]] = classes.toSeq
+  def arrayToSeq(classes: Array[Class[_]]): immutable.Seq[Class[_]] = classes.to[immutable.Seq]
 }
diff --git a/akka-actor/src/main/scala/akka/routing/ConsistentHash.scala b/akka-actor/src/main/scala/akka/routing/ConsistentHash.scala
index 819fea2586..84100f0f21 100644
--- a/akka-actor/src/main/scala/akka/routing/ConsistentHash.scala
+++ b/akka-actor/src/main/scala/akka/routing/ConsistentHash.scala
@@ -4,7 +4,7 @@
 
 package akka.routing
 
-import scala.collection.immutable.SortedMap
+import scala.collection.immutable
 import scala.reflect.ClassTag
 import java.util.Arrays
 
@@ -18,7 +18,7 @@ import java.util.Arrays
  * hash, i.e. make sure it is different for different nodes.
  *
  */
-class ConsistentHash[T: ClassTag] private (nodes: SortedMap[Int, T], val virtualNodesFactor: Int) {
+class ConsistentHash[T: ClassTag] private (nodes: immutable.SortedMap[Int, T], val virtualNodesFactor: Int) {
 
   import ConsistentHash._
 
@@ -106,7 +106,7 @@ class ConsistentHash[T: ClassTag] private (nodes: SortedMap[Int, T], val virtual
 
 object ConsistentHash {
   def apply[T: ClassTag](nodes: Iterable[T], virtualNodesFactor: Int): ConsistentHash[T] = {
-    new ConsistentHash(SortedMap.empty[Int, T] ++
+    new ConsistentHash(immutable.SortedMap.empty[Int, T] ++
       (for (node ← nodes; vnode ← 1 to virtualNodesFactor) yield (nodeHashFor(node, vnode) -> node)),
       virtualNodesFactor)
   }
diff --git a/akka-actor/src/main/scala/akka/serialization/Serialization.scala b/akka-actor/src/main/scala/akka/serialization/Serialization.scala
index 003c9de2b1..1f78fbd3a7 100644
--- a/akka-actor/src/main/scala/akka/serialization/Serialization.scala
+++ b/akka-actor/src/main/scala/akka/serialization/Serialization.scala
@@ -4,14 +4,15 @@
 
 package akka.serialization
 
-import akka.AkkaException
 import com.typesafe.config.Config
+import akka.AkkaException
 import akka.actor.{ Extension, ExtendedActorSystem, Address, DynamicAccess }
 import akka.event.Logging
 import java.util.concurrent.ConcurrentHashMap
 import scala.collection.mutable.ArrayBuffer
 import java.io.NotSerializableException
-import util.{ Try, DynamicVariable }
+import scala.util.{ Try, DynamicVariable }
+import scala.collection.immutable
 
 object Serialization {
 
@@ -97,7 +98,7 @@ class Serialization(val system: ExtendedActorSystem) extends Extension {
     serializerMap.get(clazz) match {
       case null ⇒
         // bindings are ordered from most specific to least specific
-        def unique(possibilities: Seq[(Class[_], Serializer)]): Boolean =
+        def unique(possibilities: immutable.Seq[(Class[_], Serializer)]): Boolean =
           possibilities.size == 1 ||
             (possibilities forall (_._1 isAssignableFrom possibilities(0)._1)) ||
             (possibilities forall (_._2 == possibilities(0)._2))
@@ -122,8 +123,8 @@ class Serialization(val system: ExtendedActorSystem) extends Extension {
    * loading is performed by the system’s [[akka.actor.DynamicAccess]].
    */
   def serializerOf(serializerFQN: String): Try[Serializer] =
-    system.dynamicAccess.createInstanceFor[Serializer](serializerFQN, Seq(classOf[ExtendedActorSystem] -> system)) recoverWith {
-      case _ ⇒ system.dynamicAccess.createInstanceFor[Serializer](serializerFQN, Seq())
+    system.dynamicAccess.createInstanceFor[Serializer](serializerFQN, List(classOf[ExtendedActorSystem] -> system)) recoverWith {
+      case _ ⇒ system.dynamicAccess.createInstanceFor[Serializer](serializerFQN, Nil)
     }
 
   /**
@@ -137,21 +138,21 @@ class Serialization(val system: ExtendedActorSystem) extends Extension {
    *  bindings is a Seq of tuple representing the mapping from Class to Serializer.
    *  It is primarily ordered by the most specific classes first, and secondly in the configured order.
    */
-  private[akka] val bindings: Seq[ClassSerializer] =
-    sort(for ((k: String, v: String) ← settings.SerializationBindings if v != "none") yield (system.dynamicAccess.getClassFor[Any](k).get, serializers(v)))
+  private[akka] val bindings: immutable.Seq[ClassSerializer] =
+    sort(for ((k: String, v: String) ← settings.SerializationBindings if v != "none") yield (system.dynamicAccess.getClassFor[Any](k).get, serializers(v))).to[immutable.Seq]
 
   /**
    * Sort so that subtypes always precede their supertypes, but without
    * obeying any order between unrelated subtypes (insert sort).
    */
-  private def sort(in: Iterable[ClassSerializer]): Seq[ClassSerializer] =
-    (new ArrayBuffer[ClassSerializer](in.size) /: in) { (buf, ca) ⇒
+  private def sort(in: Iterable[ClassSerializer]): immutable.Seq[ClassSerializer] =
+    ((new ArrayBuffer[ClassSerializer](in.size) /: in) { (buf, ca) ⇒
       buf.indexWhere(_._1 isAssignableFrom ca._1) match {
         case -1 ⇒ buf append ca
         case x  ⇒ buf insert (x, ca)
       }
       buf
-    }
+    }).to[immutable.Seq]
 
   /**
    * serializerMap is a Map whose keys is the class that is serializable and values is the serializer
diff --git a/akka-actor/src/main/scala/akka/util/SubclassifiedIndex.scala b/akka-actor/src/main/scala/akka/util/SubclassifiedIndex.scala
index 565d50e636..d0ee67c1fb 100644
--- a/akka-actor/src/main/scala/akka/util/SubclassifiedIndex.scala
+++ b/akka-actor/src/main/scala/akka/util/SubclassifiedIndex.scala
@@ -3,6 +3,8 @@
  */
 package akka.util
 
+import scala.collection.immutable
+
 /**
  * Typeclass which describes a classification hierarchy. Observe the contract between `isEqual` and `isSubclass`!
  */
@@ -74,7 +76,7 @@ private[akka] class SubclassifiedIndex[K, V] private (private var values: Set[V]
 
   import SubclassifiedIndex._
 
-  type Changes = Seq[(K, Set[V])]
+  type Changes = immutable.Seq[(K, Set[V])]
 
   protected var subkeys = Vector.empty[Nonroot[K, V]]
 
@@ -208,5 +210,5 @@ private[akka] class SubclassifiedIndex[K, V] private (private var values: Set[V]
   private def mergeChangesByKey(changes: Changes): Changes =
     (emptyMergeMap[K, V] /: changes) {
       case (m, (k, s)) ⇒ m.updated(k, m(k) ++ s)
-    }.toSeq
+    }.to[immutable.Seq]
 }
diff --git a/akka-camel/src/test/scala/akka/camel/ConcurrentActivationTest.scala b/akka-camel/src/test/scala/akka/camel/ConcurrentActivationTest.scala
index a4ad1564c2..ff5524ad6c 100644
--- a/akka-camel/src/test/scala/akka/camel/ConcurrentActivationTest.scala
+++ b/akka-camel/src/test/scala/akka/camel/ConcurrentActivationTest.scala
@@ -1,13 +1,18 @@
+/**
+ * Copyright (C) 2009-2012 Typesafe Inc. <http://www.typesafe.com>
+ */
 package akka.camel
 
+import language.postfixOps
+
 import org.scalatest.WordSpec
 import org.scalatest.matchers.MustMatchers
+import scala.concurrent.{ Promise, Await, Future }
+import scala.collection.immutable
 import akka.camel.TestSupport.NonSharedCamelSystem
 import akka.actor.{ ActorRef, Props, Actor }
 import akka.routing.BroadcastRouter
-import concurrent.{ Promise, Await, Future }
 import scala.concurrent.duration._
-import language.postfixOps
 import akka.testkit._
 import akka.util.Timeout
 import org.apache.camel.model.RouteDefinition
@@ -58,7 +63,7 @@ class ConcurrentActivationTest extends WordSpec with MustMatchers with NonShared
         activations.size must be(2 * number * number)
         // must be the size of the activated activated producers and consumers
         deactivations.size must be(2 * number * number)
-        def partitionNames(refs: Seq[ActorRef]) = refs.map(_.path.name).partition(_.startsWith("concurrent-test-echo-consumer"))
+        def partitionNames(refs: immutable.Seq[ActorRef]) = refs.map(_.path.name).partition(_.startsWith("concurrent-test-echo-consumer"))
         def assertContainsSameElements(lists: (Seq[_], Seq[_])) {
           val (a, b) = lists
           a.intersect(b).size must be(a.size)
diff --git a/akka-cluster/src/main/scala/akka/cluster/Cluster.scala b/akka-cluster/src/main/scala/akka/cluster/Cluster.scala
index 13f93d0482..80fdc69fed 100644
--- a/akka-cluster/src/main/scala/akka/cluster/Cluster.scala
+++ b/akka-cluster/src/main/scala/akka/cluster/Cluster.scala
@@ -75,7 +75,7 @@ class Cluster(val system: ExtendedActorSystem) extends Extension {
   val failureDetector: FailureDetector = {
     import settings.{ FailureDetectorImplementationClass ⇒ fqcn }
     system.dynamicAccess.createInstanceFor[FailureDetector](
-      fqcn, Seq(classOf[ActorSystem] -> system, classOf[ClusterSettings] -> settings)).recover({
+      fqcn, List(classOf[ActorSystem] -> system, classOf[ClusterSettings] -> settings)).recover({
         case e ⇒ throw new ConfigurationException("Could not create custom failure detector [" + fqcn + "] due to:" + e.toString)
       }).get
   }
diff --git a/akka-cluster/src/main/scala/akka/cluster/ClusterMetricsCollector.scala b/akka-cluster/src/main/scala/akka/cluster/ClusterMetricsCollector.scala
index 76c01a6381..7ed3699035 100644
--- a/akka-cluster/src/main/scala/akka/cluster/ClusterMetricsCollector.scala
+++ b/akka-cluster/src/main/scala/akka/cluster/ClusterMetricsCollector.scala
@@ -557,7 +557,7 @@ private[cluster] class MetricsCollector private (private val sigar: Option[AnyRe
  */
 private[cluster] object MetricsCollector {
   def apply(address: Address, log: LoggingAdapter, dynamicAccess: DynamicAccess): MetricsCollector =
-    dynamicAccess.createInstanceFor[AnyRef]("org.hyperic.sigar.Sigar", Seq.empty) match {
+    dynamicAccess.createInstanceFor[AnyRef]("org.hyperic.sigar.Sigar", Nil) match {
       case Success(identity) ⇒ new MetricsCollector(Some(identity), address)
       case Failure(e) ⇒
         log.debug(e.toString)
diff --git a/akka-cluster/src/multi-jvm/scala/akka/cluster/ClientDowningNodeThatIsUnreachableSpec.scala b/akka-cluster/src/multi-jvm/scala/akka/cluster/ClientDowningNodeThatIsUnreachableSpec.scala
index 3efb891a3b..bf1009b472 100644
--- a/akka-cluster/src/multi-jvm/scala/akka/cluster/ClientDowningNodeThatIsUnreachableSpec.scala
+++ b/akka-cluster/src/multi-jvm/scala/akka/cluster/ClientDowningNodeThatIsUnreachableSpec.scala
@@ -8,6 +8,7 @@ import akka.remote.testkit.MultiNodeConfig
 import akka.remote.testkit.MultiNodeSpec
 import akka.testkit._
 import akka.actor.Address
+import scala.collection.immutable
 
 case class ClientDowningNodeThatIsUnreachableMultiNodeConfig(failureDetectorPuppet: Boolean) extends MultiNodeConfig {
   val first = role("first")
@@ -51,7 +52,7 @@ abstract class ClientDowningNodeThatIsUnreachableSpec(multiNodeConfig: ClientDow
         cluster.down(thirdAddress)
         enterBarrier("down-third-node")
 
-        awaitUpConvergence(numberOfMembers = 3, canNotBePartOfMemberRing = Seq(thirdAddress))
+        awaitUpConvergence(numberOfMembers = 3, canNotBePartOfMemberRing = List(thirdAddress))
         clusterView.members.exists(_.address == thirdAddress) must be(false)
       }
 
@@ -62,7 +63,7 @@ abstract class ClientDowningNodeThatIsUnreachableSpec(multiNodeConfig: ClientDow
       runOn(second, fourth) {
         enterBarrier("down-third-node")
 
-        awaitUpConvergence(numberOfMembers = 3, canNotBePartOfMemberRing = Seq(thirdAddress))
+        awaitUpConvergence(numberOfMembers = 3, canNotBePartOfMemberRing = List(thirdAddress))
       }
 
       enterBarrier("await-completion")
diff --git a/akka-cluster/src/multi-jvm/scala/akka/cluster/ClientDowningNodeThatIsUpSpec.scala b/akka-cluster/src/multi-jvm/scala/akka/cluster/ClientDowningNodeThatIsUpSpec.scala
index 5a7308ec92..2a0af15997 100644
--- a/akka-cluster/src/multi-jvm/scala/akka/cluster/ClientDowningNodeThatIsUpSpec.scala
+++ b/akka-cluster/src/multi-jvm/scala/akka/cluster/ClientDowningNodeThatIsUpSpec.scala
@@ -8,6 +8,7 @@ import akka.remote.testkit.MultiNodeConfig
 import akka.remote.testkit.MultiNodeSpec
 import akka.testkit._
 import akka.actor.Address
+import scala.collection.immutable
 
 case class ClientDowningNodeThatIsUpMultiNodeConfig(failureDetectorPuppet: Boolean) extends MultiNodeConfig {
   val first = role("first")
@@ -49,7 +50,7 @@ abstract class ClientDowningNodeThatIsUpSpec(multiNodeConfig: ClientDowningNodeT
 
         markNodeAsUnavailable(thirdAddress)
 
-        awaitUpConvergence(numberOfMembers = 3, canNotBePartOfMemberRing = Seq(thirdAddress))
+        awaitUpConvergence(numberOfMembers = 3, canNotBePartOfMemberRing = List(thirdAddress))
         clusterView.members.exists(_.address == thirdAddress) must be(false)
       }
 
@@ -60,7 +61,7 @@ abstract class ClientDowningNodeThatIsUpSpec(multiNodeConfig: ClientDowningNodeT
       runOn(second, fourth) {
         enterBarrier("down-third-node")
 
-        awaitUpConvergence(numberOfMembers = 3, canNotBePartOfMemberRing = Seq(thirdAddress))
+        awaitUpConvergence(numberOfMembers = 3, canNotBePartOfMemberRing = List(thirdAddress))
       }
 
       enterBarrier("await-completion")
diff --git a/akka-cluster/src/multi-jvm/scala/akka/cluster/LeaderDowningNodeThatIsUnreachableSpec.scala b/akka-cluster/src/multi-jvm/scala/akka/cluster/LeaderDowningNodeThatIsUnreachableSpec.scala
index 134ed4d0d6..279e32ab66 100644
--- a/akka-cluster/src/multi-jvm/scala/akka/cluster/LeaderDowningNodeThatIsUnreachableSpec.scala
+++ b/akka-cluster/src/multi-jvm/scala/akka/cluster/LeaderDowningNodeThatIsUnreachableSpec.scala
@@ -11,6 +11,7 @@ import akka.remote.testkit.MultiNodeSpec
 import akka.testkit._
 import akka.actor._
 import scala.concurrent.duration._
+import scala.collection.immutable
 
 case class LeaderDowningNodeThatIsUnreachableMultiNodeConfig(failureDetectorPuppet: Boolean) extends MultiNodeConfig {
   val first = role("first")
@@ -59,7 +60,7 @@ abstract class LeaderDowningNodeThatIsUnreachableSpec(multiNodeConfig: LeaderDow
 
         // --- HERE THE LEADER SHOULD DETECT FAILURE AND AUTO-DOWN THE UNREACHABLE NODE ---
 
-        awaitUpConvergence(numberOfMembers = 3, canNotBePartOfMemberRing = Seq(fourthAddress), 30.seconds)
+        awaitUpConvergence(numberOfMembers = 3, canNotBePartOfMemberRing = List(fourthAddress), 30.seconds)
       }
 
       runOn(fourth) {
@@ -69,7 +70,7 @@ abstract class LeaderDowningNodeThatIsUnreachableSpec(multiNodeConfig: LeaderDow
       runOn(second, third) {
         enterBarrier("down-fourth-node")
 
-        awaitUpConvergence(numberOfMembers = 3, canNotBePartOfMemberRing = Seq(fourthAddress), 30.seconds)
+        awaitUpConvergence(numberOfMembers = 3, canNotBePartOfMemberRing = List(fourthAddress), 30.seconds)
       }
 
       enterBarrier("await-completion-1")
@@ -89,7 +90,7 @@ abstract class LeaderDowningNodeThatIsUnreachableSpec(multiNodeConfig: LeaderDow
 
         // --- HERE THE LEADER SHOULD DETECT FAILURE AND AUTO-DOWN THE UNREACHABLE NODE ---
 
-        awaitUpConvergence(numberOfMembers = 2, canNotBePartOfMemberRing = Seq(secondAddress), 30.seconds)
+        awaitUpConvergence(numberOfMembers = 2, canNotBePartOfMemberRing = List(secondAddress), 30.seconds)
       }
 
       runOn(second) {
@@ -99,7 +100,7 @@ abstract class LeaderDowningNodeThatIsUnreachableSpec(multiNodeConfig: LeaderDow
       runOn(third) {
         enterBarrier("down-second-node")
 
-        awaitUpConvergence(numberOfMembers = 2, canNotBePartOfMemberRing = Seq(secondAddress), 30 seconds)
+        awaitUpConvergence(numberOfMembers = 2, canNotBePartOfMemberRing = List(secondAddress), 30 seconds)
       }
 
       enterBarrier("await-completion-2")
diff --git a/akka-cluster/src/multi-jvm/scala/akka/cluster/LeaderElectionSpec.scala b/akka-cluster/src/multi-jvm/scala/akka/cluster/LeaderElectionSpec.scala
index fc8c4d2619..dfe1553369 100644
--- a/akka-cluster/src/multi-jvm/scala/akka/cluster/LeaderElectionSpec.scala
+++ b/akka-cluster/src/multi-jvm/scala/akka/cluster/LeaderElectionSpec.scala
@@ -10,6 +10,7 @@ import akka.remote.testkit.MultiNodeConfig
 import akka.remote.testkit.MultiNodeSpec
 import akka.testkit._
 import scala.concurrent.duration._
+import scala.collection.immutable
 
 case class LeaderElectionMultiNodeConfig(failureDetectorPuppet: Boolean) extends MultiNodeConfig {
   val controller = role("controller")
@@ -42,7 +43,7 @@ abstract class LeaderElectionSpec(multiNodeConfig: LeaderElectionMultiNodeConfig
   import multiNodeConfig._
 
   // sorted in the order used by the cluster
-  lazy val sortedRoles = Seq(first, second, third, fourth).sorted
+  lazy val sortedRoles = List(first, second, third, fourth).sorted
 
   "A cluster of four nodes" must {
 
diff --git a/akka-cluster/src/multi-jvm/scala/akka/cluster/MultiNodeClusterSpec.scala b/akka-cluster/src/multi-jvm/scala/akka/cluster/MultiNodeClusterSpec.scala
index 12fc8ebbc6..d696f9b62b 100644
--- a/akka-cluster/src/multi-jvm/scala/akka/cluster/MultiNodeClusterSpec.scala
+++ b/akka-cluster/src/multi-jvm/scala/akka/cluster/MultiNodeClusterSpec.scala
@@ -4,21 +4,21 @@
 package akka.cluster
 
 import language.implicitConversions
+
+import org.scalatest.Suite
+import org.scalatest.exceptions.TestFailedException
+
 import com.typesafe.config.Config
 import com.typesafe.config.ConfigFactory
-import akka.actor.{ Address, ExtendedActorSystem }
 import akka.remote.testconductor.RoleName
 import akka.remote.testkit.{ STMultiNodeSpec, MultiNodeSpec }
 import akka.testkit._
 import akka.testkit.TestEvent._
-import scala.concurrent.duration._
-import org.scalatest.Suite
-import org.scalatest.exceptions.TestFailedException
-import java.util.concurrent.ConcurrentHashMap
-import akka.actor.ActorPath
-import akka.actor.RootActorPath
+import akka.actor.{ ActorSystem, Address }
 import akka.event.Logging.ErrorLevel
-import akka.actor.ActorSystem
+import scala.concurrent.duration._
+import scala.collection.immutable
+import java.util.concurrent.ConcurrentHashMap
 
 object MultiNodeClusterSpec {
 
@@ -158,7 +158,7 @@ trait MultiNodeClusterSpec extends Suite with STMultiNodeSpec { self: MultiNodeS
    * nodes (roles). First node will be started first
    * and others will join the first.
    */
-  def startCluster(roles: RoleName*): Unit = awaitStartCluster(false, roles.toSeq)
+  def startCluster(roles: RoleName*): Unit = awaitStartCluster(false, roles.to[immutable.Seq])
 
   /**
    * Initialize the cluster of the specified member
@@ -166,11 +166,9 @@ trait MultiNodeClusterSpec extends Suite with STMultiNodeSpec { self: MultiNodeS
    * First node will be started first  and others will join
    * the first.
    */
-  def awaitClusterUp(roles: RoleName*): Unit = {
-    awaitStartCluster(true, roles.toSeq)
-  }
+  def awaitClusterUp(roles: RoleName*): Unit = awaitStartCluster(true, roles.to[immutable.Seq])
 
-  private def awaitStartCluster(upConvergence: Boolean = true, roles: Seq[RoleName]): Unit = {
+  private def awaitStartCluster(upConvergence: Boolean = true, roles: immutable.Seq[RoleName]): Unit = {
     runOn(roles.head) {
       // make sure that the node-to-join is started before other join
       startClusterNode()
@@ -196,16 +194,15 @@ trait MultiNodeClusterSpec extends Suite with STMultiNodeSpec { self: MultiNodeS
     expectedAddresses.sorted.zipWithIndex.foreach { case (a, i) ⇒ members(i).address must be(a) }
   }
 
-  def assertLeader(nodesInCluster: RoleName*): Unit = if (nodesInCluster.contains(myself)) {
-    assertLeaderIn(nodesInCluster)
-  }
+  def assertLeader(nodesInCluster: RoleName*): Unit =
+    if (nodesInCluster.contains(myself)) assertLeaderIn(nodesInCluster.to[immutable.Seq])
 
   /**
    * Assert that the cluster has elected the correct leader
    * out of all nodes in the cluster. First
    * member in the cluster ring is expected leader.
    */
-  def assertLeaderIn(nodesInCluster: Seq[RoleName]): Unit = if (nodesInCluster.contains(myself)) {
+  def assertLeaderIn(nodesInCluster: immutable.Seq[RoleName]): Unit = if (nodesInCluster.contains(myself)) {
     nodesInCluster.length must not be (0)
     val expectedLeader = roleOfLeader(nodesInCluster)
     val leader = clusterView.leader
@@ -221,7 +218,7 @@ trait MultiNodeClusterSpec extends Suite with STMultiNodeSpec { self: MultiNodeS
    */
   def awaitUpConvergence(
     numberOfMembers: Int,
-    canNotBePartOfMemberRing: Seq[Address] = Seq.empty[Address],
+    canNotBePartOfMemberRing: immutable.Seq[Address] = Nil,
     timeout: FiniteDuration = 20.seconds): Unit = {
     within(timeout) {
       awaitCond(clusterView.members.size == numberOfMembers)
@@ -239,7 +236,7 @@ trait MultiNodeClusterSpec extends Suite with STMultiNodeSpec { self: MultiNodeS
   def awaitSeenSameState(addresses: Address*): Unit =
     awaitCond((addresses.toSet -- clusterView.seenBy).isEmpty)
 
-  def roleOfLeader(nodesInCluster: Seq[RoleName] = roles): RoleName = {
+  def roleOfLeader(nodesInCluster: immutable.Seq[RoleName] = roles): RoleName = {
     nodesInCluster.length must not be (0)
     nodesInCluster.sorted.head
   }
diff --git a/akka-cluster/src/multi-jvm/scala/akka/cluster/SingletonClusterSpec.scala b/akka-cluster/src/multi-jvm/scala/akka/cluster/SingletonClusterSpec.scala
index 291a59a44f..33ce67ecb5 100644
--- a/akka-cluster/src/multi-jvm/scala/akka/cluster/SingletonClusterSpec.scala
+++ b/akka-cluster/src/multi-jvm/scala/akka/cluster/SingletonClusterSpec.scala
@@ -8,6 +8,7 @@ import akka.remote.testkit.MultiNodeConfig
 import akka.remote.testkit.MultiNodeSpec
 import akka.testkit._
 import scala.concurrent.duration._
+import scala.collection.immutable
 
 case class SingletonClusterMultiNodeConfig(failureDetectorPuppet: Boolean) extends MultiNodeConfig {
   val first = role("first")
@@ -65,7 +66,7 @@ abstract class SingletonClusterSpec(multiNodeConfig: SingletonClusterMultiNodeCo
 
         markNodeAsUnavailable(secondAddress)
 
-        awaitUpConvergence(numberOfMembers = 1, canNotBePartOfMemberRing = Seq(secondAddress), 30.seconds)
+        awaitUpConvergence(numberOfMembers = 1, canNotBePartOfMemberRing = List(secondAddress), 30.seconds)
         clusterView.isSingletonCluster must be(true)
         awaitCond(clusterView.isLeader)
       }
diff --git a/akka-cluster/src/multi-jvm/scala/akka/cluster/SplitBrainSpec.scala b/akka-cluster/src/multi-jvm/scala/akka/cluster/SplitBrainSpec.scala
index e1b1a4af96..a7a7c6f4ba 100644
--- a/akka-cluster/src/multi-jvm/scala/akka/cluster/SplitBrainSpec.scala
+++ b/akka-cluster/src/multi-jvm/scala/akka/cluster/SplitBrainSpec.scala
@@ -9,9 +9,10 @@ import com.typesafe.config.ConfigFactory
 import akka.remote.testkit.MultiNodeConfig
 import akka.remote.testkit.MultiNodeSpec
 import akka.testkit._
-import scala.concurrent.duration._
 import akka.actor.Address
 import akka.remote.testconductor.Direction
+import scala.concurrent.duration._
+import scala.collection.immutable
 
 case class SplitBrainMultiNodeConfig(failureDetectorPuppet: Boolean) extends MultiNodeConfig {
   val first = role("first")
@@ -53,8 +54,8 @@ abstract class SplitBrainSpec(multiNodeConfig: SplitBrainMultiNodeConfig)
 
   muteMarkingAsUnreachable()
 
-  val side1 = IndexedSeq(first, second)
-  val side2 = IndexedSeq(third, fourth, fifth)
+  val side1 = Vector(first, second)
+  val side2 = Vector(third, fourth, fifth)
 
   "A cluster of 5 members" must {
 
diff --git a/akka-cluster/src/multi-jvm/scala/akka/cluster/UnreachableNodeRejoinsClusterSpec.scala b/akka-cluster/src/multi-jvm/scala/akka/cluster/UnreachableNodeRejoinsClusterSpec.scala
index db2f9fc930..395d803865 100644
--- a/akka-cluster/src/multi-jvm/scala/akka/cluster/UnreachableNodeRejoinsClusterSpec.scala
+++ b/akka-cluster/src/multi-jvm/scala/akka/cluster/UnreachableNodeRejoinsClusterSpec.scala
@@ -6,13 +6,14 @@ package akka.cluster
 import language.postfixOps
 
 import org.scalatest.BeforeAndAfter
+import com.typesafe.config.ConfigFactory
 import akka.remote.testkit.MultiNodeConfig
 import akka.remote.testkit.MultiNodeSpec
 import akka.testkit._
-import com.typesafe.config.ConfigFactory
 import akka.actor.Address
 import akka.remote.testconductor.{ RoleName, Direction }
 import scala.concurrent.duration._
+import scala.collection.immutable
 
 case class UnreachableNodeRejoinsClusterMultiNodeConfig(failureDetectorPuppet: Boolean) extends MultiNodeConfig {
   val first = role("first")
@@ -45,7 +46,7 @@ abstract class UnreachableNodeRejoinsClusterSpec(multiNodeConfig: UnreachableNod
 
   muteMarkingAsUnreachable()
 
-  def allBut(role: RoleName, roles: Seq[RoleName] = roles): Seq[RoleName] = {
+  def allBut(role: RoleName, roles: immutable.Seq[RoleName] = roles): immutable.Seq[RoleName] = {
     roles.filterNot(_ == role)
   }
 
@@ -125,7 +126,7 @@ abstract class UnreachableNodeRejoinsClusterSpec(multiNodeConfig: UnreachableNod
       }
 
       runOn(allBut(victim): _*) {
-        awaitUpConvergence(roles.size - 1, Seq(victim))
+        awaitUpConvergence(roles.size - 1, List(victim))
       }
 
       endBarrier
diff --git a/akka-cluster/src/test/scala/akka/cluster/AccrualFailureDetectorSpec.scala b/akka-cluster/src/test/scala/akka/cluster/AccrualFailureDetectorSpec.scala
index 45476864db..8a9d6eb6fc 100644
--- a/akka-cluster/src/test/scala/akka/cluster/AccrualFailureDetectorSpec.scala
+++ b/akka-cluster/src/test/scala/akka/cluster/AccrualFailureDetectorSpec.scala
@@ -7,7 +7,7 @@ package akka.cluster
 import akka.actor.Address
 import akka.testkit._
 import akka.testkit.TestEvent._
-import scala.collection.immutable.TreeMap
+import scala.collection.immutable
 import scala.concurrent.duration._
 
 @org.junit.runner.RunWith(classOf[org.scalatest.junit.JUnitRunner])
@@ -27,7 +27,7 @@ class AccrualFailureDetectorSpec extends AkkaSpec("""
     val conn = Address("akka", "", "localhost", 2552)
     val conn2 = Address("akka", "", "localhost", 2553)
 
-    def fakeTimeGenerator(timeIntervals: Seq[Long]): () ⇒ Long = {
+    def fakeTimeGenerator(timeIntervals: immutable.Seq[Long]): () ⇒ Long = {
       var times = timeIntervals.tail.foldLeft(List[Long](timeIntervals.head))((acc, c) ⇒ acc ::: List[Long](acc.last + c))
       def timeGenerator(): Long = {
         val currentTime = times.head
@@ -73,7 +73,7 @@ class AccrualFailureDetectorSpec extends AkkaSpec("""
 
     "return realistic phi values" in {
       val fd = createFailureDetector()
-      val test = TreeMap(0 -> 0.0, 500 -> 0.1, 1000 -> 0.3, 1200 -> 1.6, 1400 -> 4.7, 1600 -> 10.8, 1700 -> 15.3)
+      val test = immutable.TreeMap(0 -> 0.0, 500 -> 0.1, 1000 -> 0.3, 1200 -> 1.6, 1400 -> 4.7, 1600 -> 10.8, 1700 -> 15.3)
       for ((timeDiff, expectedPhi) ← test) {
         fd.phi(timeDiff = timeDiff, mean = 1000.0, stdDeviation = 100.0) must be(expectedPhi plusOrMinus (0.1))
       }
diff --git a/akka-cluster/src/test/scala/akka/cluster/MetricsCollectorSpec.scala b/akka-cluster/src/test/scala/akka/cluster/MetricsCollectorSpec.scala
index 6589ba0efc..609975db6a 100644
--- a/akka-cluster/src/test/scala/akka/cluster/MetricsCollectorSpec.scala
+++ b/akka-cluster/src/test/scala/akka/cluster/MetricsCollectorSpec.scala
@@ -5,14 +5,16 @@
 package akka.cluster
 
 import scala.language.postfixOps
+
+import scala.collection.immutable
 import scala.concurrent.duration._
 import scala.concurrent.Await
+import scala.util.{ Success, Try, Failure }
 
 import akka.actor._
 import akka.testkit._
 import org.scalatest.WordSpec
 import org.scalatest.matchers.MustMatchers
-import util.{ Success, Try, Failure }
 
 object MetricsEnabledSpec {
   val config = """
@@ -207,11 +209,10 @@ trait MetricSpec extends WordSpec with MustMatchers {
     if (decay > 0) metrics.collect { case m if m.trendable && (!m.initializable) ⇒ m }.foreach(_.average.isDefined must be(true))
   }
 
-  def collectNodeMetrics(nodes: Set[NodeMetrics]): Seq[Metric] = {
-    var r: Seq[Metric] = Seq.empty
-    nodes.foreach(n ⇒ r ++= n.metrics.filter(_.isDefined))
-    r
-  }
+  def collectNodeMetrics(nodes: Set[NodeMetrics]): immutable.Seq[Metric] =
+    nodes.foldLeft(Vector[Metric]()) {
+      case (r, n) ⇒ r ++ n.metrics.filter(_.isDefined)
+    }
 }
 
 trait AbstractClusterMetricsSpec extends DefaultTimeout {
diff --git a/akka-docs/rst/java/code/docs/actor/FaultHandlingTestBase.java b/akka-docs/rst/java/code/docs/actor/FaultHandlingTestBase.java
index c78da61fb1..9ea2a332b1 100644
--- a/akka-docs/rst/java/code/docs/actor/FaultHandlingTestBase.java
+++ b/akka-docs/rst/java/code/docs/actor/FaultHandlingTestBase.java
@@ -30,7 +30,7 @@ import static java.util.concurrent.TimeUnit.SECONDS;
 import akka.japi.Function;
 import scala.Option;
 import scala.collection.JavaConverters;
-import scala.collection.Seq;
+import scala.collection.immutable.Seq;
 
 import org.junit.Test;
 import org.junit.BeforeClass;
@@ -220,7 +220,7 @@ public class FaultHandlingTestBase {
   //#testkit
   public <A> Seq<A> seq(A... args) {
     return JavaConverters.collectionAsScalaIterableConverter(
-      java.util.Arrays.asList(args)).asScala().toSeq();
+      java.util.Arrays.asList(args)).asScala().toList();
   }
   //#testkit
 }
diff --git a/akka-docs/rst/java/code/docs/jrouting/CustomRouterDocTestBase.java b/akka-docs/rst/java/code/docs/jrouting/CustomRouterDocTestBase.java
index c4e7414ce1..73b8c5c639 100644
--- a/akka-docs/rst/java/code/docs/jrouting/CustomRouterDocTestBase.java
+++ b/akka-docs/rst/java/code/docs/jrouting/CustomRouterDocTestBase.java
@@ -11,6 +11,7 @@ import static docs.jrouting.CustomRouterDocTestBase.Message.RepublicanVote;
 import static org.junit.Assert.assertEquals;
 
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 import org.junit.After;
@@ -69,7 +70,7 @@ public class CustomRouterDocTestBase {
     //#supervision
     final SupervisorStrategy strategy =
       new OneForOneStrategy(5, Duration.create("1 minute"),
-        new Class<?>[] { Exception.class });
+         Collections.<Class<? extends Throwable>>singletonList(Exception.class));
     final ActorRef router = system.actorOf(new Props(MyActor.class)
         .withRouter(new RoundRobinRouter(5).withSupervisorStrategy(strategy)));
     //#supervision
diff --git a/akka-docs/rst/scala/code/docs/actor/FSMDocSpec.scala b/akka-docs/rst/scala/code/docs/actor/FSMDocSpec.scala
index bcc908990f..cc88416b0e 100644
--- a/akka-docs/rst/scala/code/docs/actor/FSMDocSpec.scala
+++ b/akka-docs/rst/scala/code/docs/actor/FSMDocSpec.scala
@@ -8,6 +8,7 @@ import language.postfixOps
 import akka.testkit.{ AkkaSpec ⇒ MyFavoriteTestFrameWorkPlusAkkaTestKit }
 //#test-code
 import akka.actor.Props
+import scala.collection.immutable
 
 class FSMDocSpec extends MyFavoriteTestFrameWorkPlusAkkaTestKit {
 
@@ -24,7 +25,7 @@ class FSMDocSpec extends MyFavoriteTestFrameWorkPlusAkkaTestKit {
     case object Flush
 
     // sent events
-    case class Batch(obj: Seq[Any])
+    case class Batch(obj: immutable.Seq[Any])
     //#simple-events
     //#simple-state
     // states
@@ -34,7 +35,7 @@ class FSMDocSpec extends MyFavoriteTestFrameWorkPlusAkkaTestKit {
 
     sealed trait Data
     case object Uninitialized extends Data
-    case class Todo(target: ActorRef, queue: Seq[Any]) extends Data
+    case class Todo(target: ActorRef, queue: immutable.Seq[Any]) extends Data
     //#simple-state
     //#simple-fsm
     class Buncher extends Actor with FSM[State, Data] {
@@ -193,12 +194,12 @@ class FSMDocSpec extends MyFavoriteTestFrameWorkPlusAkkaTestKit {
       buncher ! SetTarget(testActor)
       buncher ! Queue(42)
       buncher ! Queue(43)
-      expectMsg(Batch(Seq(42, 43)))
+      expectMsg(Batch(immutable.Seq(42, 43)))
       buncher ! Queue(44)
       buncher ! Flush
       buncher ! Queue(45)
-      expectMsg(Batch(Seq(44)))
-      expectMsg(Batch(Seq(45)))
+      expectMsg(Batch(immutable.Seq(44)))
+      expectMsg(Batch(immutable.Seq(45)))
     }
 
     "batch not if uninitialized" in {
diff --git a/akka-docs/rst/scala/code/docs/testkit/TestKitUsageSpec.scala b/akka-docs/rst/scala/code/docs/testkit/TestKitUsageSpec.scala
index 48e6b6664b..8b153c5944 100644
--- a/akka-docs/rst/scala/code/docs/testkit/TestKitUsageSpec.scala
+++ b/akka-docs/rst/scala/code/docs/testkit/TestKitUsageSpec.scala
@@ -22,6 +22,7 @@ import akka.testkit.DefaultTimeout
 import akka.testkit.ImplicitSender
 import akka.testkit.TestKit
 import scala.concurrent.duration._
+import scala.collection.immutable
 
 /**
  * a Test to show some TestKit examples
@@ -38,8 +39,8 @@ class TestKitUsageSpec
   val filterRef = system.actorOf(Props(new FilteringActor(testActor)))
   val randomHead = Random.nextInt(6)
   val randomTail = Random.nextInt(10)
-  val headList = Seq().padTo(randomHead, "0")
-  val tailList = Seq().padTo(randomTail, "1")
+  val headList = immutable.Seq().padTo(randomHead, "0")
+  val tailList = immutable.Seq().padTo(randomTail, "1")
   val seqRef =
     system.actorOf(Props(new SequencingActor(testActor, headList, tailList)))
 
@@ -145,7 +146,7 @@ object TestKitUsageSpec {
    * like to test that the interesting value is received and that you cant
    * be bothered with the rest
    */
-  class SequencingActor(next: ActorRef, head: Seq[String], tail: Seq[String])
+  class SequencingActor(next: ActorRef, head: immutable.Seq[String], tail: immutable.Seq[String])
     extends Actor {
     def receive = {
       case msg ⇒ {
diff --git a/akka-docs/rst/scala/code/docs/zeromq/ZeromqDocSpec.scala b/akka-docs/rst/scala/code/docs/zeromq/ZeromqDocSpec.scala
index 0e3b4df262..28ff2e3d34 100644
--- a/akka-docs/rst/scala/code/docs/zeromq/ZeromqDocSpec.scala
+++ b/akka-docs/rst/scala/code/docs/zeromq/ZeromqDocSpec.scala
@@ -5,13 +5,13 @@ package docs.zeromq
 
 import language.postfixOps
 
-import akka.actor.{ Actor, Props }
 import scala.concurrent.duration._
+import scala.collection.immutable
+import akka.actor.{ Actor, Props }
 import akka.testkit._
-import akka.zeromq.{ ZeroMQVersion, ZeroMQExtension }
+import akka.zeromq.{ ZeroMQVersion, ZeroMQExtension, SocketType, Bind }
 import java.text.SimpleDateFormat
 import java.util.Date
-import akka.zeromq.{ SocketType, Bind }
 
 object ZeromqDocSpec {
 
@@ -52,12 +52,12 @@ object ZeromqDocSpec {
         val heapPayload = ser.serialize(Heap(timestamp, currentHeap.getUsed,
           currentHeap.getMax)).get
         // the first frame is the topic, second is the message
-        pubSocket ! ZMQMessage(Seq(Frame("health.heap"), Frame(heapPayload)))
+        pubSocket ! ZMQMessage(immutable.Seq(Frame("health.heap"), Frame(heapPayload)))
 
         // use akka SerializationExtension to convert to bytes
         val loadPayload = ser.serialize(Load(timestamp, os.getSystemLoadAverage)).get
         // the first frame is the topic, second is the message
-        pubSocket ! ZMQMessage(Seq(Frame("health.load"), Frame(loadPayload)))
+        pubSocket ! ZMQMessage(immutable.Seq(Frame("health.load"), Frame(loadPayload)))
     }
   }
   //#health
@@ -146,7 +146,7 @@ class ZeromqDocSpec extends AkkaSpec("akka.loglevel=INFO") {
 
     val payload = Array.empty[Byte]
     //#pub-topic
-    pubSocket ! ZMQMessage(Seq(Frame("foo.bar"), Frame(payload)))
+    pubSocket ! ZMQMessage(Frame("foo.bar"), Frame(payload))
     //#pub-topic
 
     system.stop(subSocket)
diff --git a/akka-kernel/src/main/scala/akka/kernel/Main.scala b/akka-kernel/src/main/scala/akka/kernel/Main.scala
index 97ff625ab8..3fe3cac403 100644
--- a/akka-kernel/src/main/scala/akka/kernel/Main.scala
+++ b/akka-kernel/src/main/scala/akka/kernel/Main.scala
@@ -9,6 +9,7 @@ import java.io.File
 import java.lang.Boolean.getBoolean
 import java.net.URLClassLoader
 import java.util.jar.JarFile
+import scala.collection.immutable
 import scala.collection.JavaConverters._
 
 /**
@@ -77,8 +78,8 @@ object Main {
 
     Thread.currentThread.setContextClassLoader(classLoader)
 
-    val bootClasses: Seq[String] = args.toSeq
-    val bootables: Seq[Bootable] = bootClasses map { c ⇒ classLoader.loadClass(c).newInstance.asInstanceOf[Bootable] }
+    val bootClasses: immutable.Seq[String] = args.to[immutable.Seq]
+    val bootables: immutable.Seq[Bootable] = bootClasses map { c ⇒ classLoader.loadClass(c).newInstance.asInstanceOf[Bootable] }
 
     for (bootable ← bootables) {
       log("Starting up " + bootable.getClass.getName)
@@ -122,7 +123,7 @@ object Main {
     new URLClassLoader(urls, Thread.currentThread.getContextClassLoader)
   }
 
-  private def addShutdownHook(bootables: Seq[Bootable]): Unit = {
+  private def addShutdownHook(bootables: immutable.Seq[Bootable]): Unit = {
     Runtime.getRuntime.addShutdownHook(new Thread(new Runnable {
       def run = {
         log("")
diff --git a/akka-osgi-aries/src/test/scala/akka/osgi/aries/blueprint/NamespaceHandlerTest.scala b/akka-osgi-aries/src/test/scala/akka/osgi/aries/blueprint/NamespaceHandlerTest.scala
index 2728a80894..79d07c65a3 100644
--- a/akka-osgi-aries/src/test/scala/akka/osgi/aries/blueprint/NamespaceHandlerTest.scala
+++ b/akka-osgi-aries/src/test/scala/akka/osgi/aries/blueprint/NamespaceHandlerTest.scala
@@ -32,7 +32,7 @@ class SimpleNamespaceHandlerTest extends WordSpec with MustMatchers with PojoSRT
 
   import NamespaceHandlerTest._
 
-  val testBundles: Seq[BundleDescriptor] = buildTestBundles(Seq(
+  val testBundles = buildTestBundles(List(
     AKKA_OSGI_BLUEPRINT,
     bundle(TEST_BUNDLE_NAME).withBlueprintFile(getClass.getResource("simple.xml"))))
 
@@ -62,7 +62,7 @@ class ConfigNamespaceHandlerTest extends WordSpec with MustMatchers with PojoSRT
 
   import NamespaceHandlerTest._
 
-  val testBundles: Seq[BundleDescriptor] = buildTestBundles(Seq(
+  val testBundles = buildTestBundles(List(
     AKKA_OSGI_BLUEPRINT,
     bundle(TEST_BUNDLE_NAME).withBlueprintFile(getClass.getResource("config.xml"))))
 
@@ -94,7 +94,7 @@ class DependencyInjectionNamespaceHandlerTest extends WordSpec with MustMatchers
 
   import NamespaceHandlerTest._
 
-  val testBundles: Seq[BundleDescriptor] = buildTestBundles(Seq(
+  val testBundles = buildTestBundles(List(
     AKKA_OSGI_BLUEPRINT,
     bundle(TEST_BUNDLE_NAME).withBlueprintFile(getClass.getResource("injection.xml"))))
 
diff --git a/akka-osgi/src/test/scala/akka/osgi/ActorSystemActivatorTest.scala b/akka-osgi/src/test/scala/akka/osgi/ActorSystemActivatorTest.scala
index d582209d76..27455be75e 100644
--- a/akka-osgi/src/test/scala/akka/osgi/ActorSystemActivatorTest.scala
+++ b/akka-osgi/src/test/scala/akka/osgi/ActorSystemActivatorTest.scala
@@ -10,6 +10,7 @@ import akka.actor.ActorSystem
 import akka.pattern.ask
 import scala.concurrent.Await
 import scala.concurrent.duration._
+import scala.collection.immutable
 import akka.util.Timeout
 import de.kalpatec.pojosr.framework.launch.BundleDescriptor
 import test.{ RuntimeNameActorSystemActivator, TestActivators, PingPongActorSystemActivator }
@@ -32,7 +33,7 @@ class PingPongActorSystemActivatorTest extends WordSpec with MustMatchers with P
 
   import ActorSystemActivatorTest._
 
-  val testBundles: Seq[BundleDescriptor] = buildTestBundles(Seq(
+  val testBundles: immutable.Seq[BundleDescriptor] = buildTestBundles(List(
     bundle(TEST_BUNDLE_NAME).withActivator(classOf[PingPongActorSystemActivator])))
 
   "PingPongActorSystemActivator" must {
@@ -65,7 +66,8 @@ class RuntimeNameActorSystemActivatorTest extends WordSpec with MustMatchers wit
 
   import ActorSystemActivatorTest._
 
-  val testBundles: Seq[BundleDescriptor] = buildTestBundles(Seq(bundle(TEST_BUNDLE_NAME).withActivator(classOf[RuntimeNameActorSystemActivator])))
+  val testBundles: immutable.Seq[BundleDescriptor] =
+    buildTestBundles(List(bundle(TEST_BUNDLE_NAME).withActivator(classOf[RuntimeNameActorSystemActivator])))
 
   "RuntimeNameActorSystemActivator" must {
 
diff --git a/akka-osgi/src/test/scala/akka/osgi/PojoSRTestSupport.scala b/akka-osgi/src/test/scala/akka/osgi/PojoSRTestSupport.scala
index e993d04f01..b8c7ea24e5 100644
--- a/akka-osgi/src/test/scala/akka/osgi/PojoSRTestSupport.scala
+++ b/akka-osgi/src/test/scala/akka/osgi/PojoSRTestSupport.scala
@@ -17,7 +17,7 @@ import java.io._
 import org.scalatest.{ BeforeAndAfterAll, Suite }
 import java.util.{ UUID, Date, ServiceLoader, HashMap }
 import scala.reflect.ClassTag
-import scala.Some
+import scala.collection.immutable
 
 /**
  * Trait that provides support for building akka-osgi tests using PojoSR
@@ -31,7 +31,7 @@ trait PojoSRTestSupport extends Suite with BeforeAndAfterAll {
    * All bundles being found on the test classpath are automatically installed and started in the PojoSR runtime.
    * Implement this to define the extra bundles that should be available for testing.
    */
-  def testBundles: Seq[BundleDescriptor]
+  def testBundles: immutable.Seq[BundleDescriptor]
 
   val bufferedLoadingErrors = new ByteArrayOutputStream()
 
@@ -82,15 +82,11 @@ trait PojoSRTestSupport extends Suite with BeforeAndAfterAll {
     }
   }
 
-  protected def buildTestBundles(builders: Seq[BundleDescriptorBuilder]): Seq[BundleDescriptor] = builders map (_.build)
+  protected def buildTestBundles(builders: immutable.Seq[BundleDescriptorBuilder]): immutable.Seq[BundleDescriptor] =
+    builders map (_.build)
 
-  def filterErrors()(block: ⇒ Unit): Unit = {
-    try {
-      block
-    } catch {
-      case e: Throwable ⇒ System.err.write(bufferedLoadingErrors.toByteArray); throw e
-    }
-  }
+  def filterErrors()(block: ⇒ Unit): Unit =
+    try block catch { case e: Throwable ⇒ System.err.write(bufferedLoadingErrors.toByteArray); throw e }
 }
 
 object PojoSRTestSupport {
diff --git a/akka-remote-tests/src/main/scala/akka/remote/testconductor/NetworkFailureInjector.scala b/akka-remote-tests/src/main/scala/akka/remote/testconductor/NetworkFailureInjector.scala
index 3f2e739308..26d6f6f243 100644
--- a/akka-remote-tests/src/main/scala/akka/remote/testconductor/NetworkFailureInjector.scala
+++ b/akka-remote-tests/src/main/scala/akka/remote/testconductor/NetworkFailureInjector.scala
@@ -6,13 +6,13 @@ package akka.remote.testconductor
 import language.postfixOps
 import java.net.InetSocketAddress
 import scala.annotation.tailrec
-import scala.collection.immutable.Queue
+import scala.collection.immutable
+import scala.concurrent.duration._
 import org.jboss.netty.buffer.ChannelBuffer
 import org.jboss.netty.channel.{ SimpleChannelHandler, MessageEvent, Channels, ChannelStateEvent, ChannelHandlerContext, ChannelFutureListener, ChannelFuture }
 import akka.actor.{ Props, LoggingFSM, Address, ActorSystem, ActorRef, ActorLogging, Actor, FSM }
 import akka.event.Logging
 import akka.remote.netty.ChannelAddress
-import scala.concurrent.duration._
 
 /**
  * INTERNAL API.
@@ -230,7 +230,7 @@ private[akka] object ThrottleActor {
   case object Throttle extends State
   case object Blackhole extends State
 
-  case class Data(lastSent: Long, rateMBit: Float, queue: Queue[Send])
+  case class Data(lastSent: Long, rateMBit: Float, queue: immutable.Queue[Send])
 
   case class Send(ctx: ChannelHandlerContext, direction: Direction, future: Option[ChannelFuture], msg: AnyRef)
   case class SetRate(rateMBit: Float)
@@ -248,7 +248,7 @@ private[akka] class ThrottleActor(channelContext: ChannelHandlerContext)
 
   private val packetSplitThreshold = TestConductor(context.system).Settings.PacketSplitThreshold
 
-  startWith(PassThrough, Data(0, -1, Queue()))
+  startWith(PassThrough, Data(0, -1, immutable.Queue()))
 
   when(PassThrough) {
     case Event(s @ Send(_, _, _, msg), _) ⇒
@@ -258,8 +258,8 @@ private[akka] class ThrottleActor(channelContext: ChannelHandlerContext)
   }
 
   when(Throttle) {
-    case Event(s: Send, data @ Data(_, _, Queue())) ⇒
-      stay using sendThrottled(data.copy(lastSent = System.nanoTime, queue = Queue(s)))
+    case Event(s: Send, data @ Data(_, _, immutable.Queue())) ⇒
+      stay using sendThrottled(data.copy(lastSent = System.nanoTime, queue = immutable.Queue(s)))
     case Event(s: Send, data) ⇒
       stay using sendThrottled(data.copy(queue = data.queue.enqueue(s)))
     case Event(Tick, data) ⇒
@@ -286,7 +286,7 @@ private[akka] class ThrottleActor(channelContext: ChannelHandlerContext)
   whenUnhandled {
     case Event(SetRate(rate), d) ⇒
       if (rate > 0) {
-        goto(Throttle) using d.copy(lastSent = System.nanoTime, rateMBit = rate, queue = Queue())
+        goto(Throttle) using d.copy(lastSent = System.nanoTime, rateMBit = rate, queue = immutable.Queue())
       } else if (rate == 0) {
         goto(Blackhole)
       } else {
@@ -328,7 +328,7 @@ private[akka] class ThrottleActor(channelContext: ChannelHandlerContext)
    */
   private def schedule(d: Data): (Data, Seq[Send], Option[FiniteDuration]) = {
     val now = System.nanoTime
-    @tailrec def rec(d: Data, toSend: Seq[Send]): (Data, Seq[Send], Option[FiniteDuration]) = {
+    @tailrec def rec(d: Data, toSend: immutable.Seq[Send]): (Data, immutable.Seq[Send], Option[FiniteDuration]) = {
       if (d.queue.isEmpty) (d, toSend, None)
       else {
         val timeForPacket = d.lastSent + (1000 * size(d.queue.head.msg) / d.rateMBit).toLong
@@ -344,7 +344,7 @@ private[akka] class ThrottleActor(channelContext: ChannelHandlerContext)
         }
       }
     }
-    rec(d, Seq())
+    rec(d, Nil)
   }
 
   /**
diff --git a/akka-remote-tests/src/main/scala/akka/remote/testconductor/Player.scala b/akka-remote-tests/src/main/scala/akka/remote/testconductor/Player.scala
index 2a3957d146..95bfab1ee5 100644
--- a/akka-remote-tests/src/main/scala/akka/remote/testconductor/Player.scala
+++ b/akka-remote-tests/src/main/scala/akka/remote/testconductor/Player.scala
@@ -4,20 +4,20 @@
 package akka.remote.testconductor
 
 import language.postfixOps
+
+import java.util.concurrent.TimeoutException
 import akka.actor.{ Actor, ActorRef, ActorSystem, LoggingFSM, Props, PoisonPill, Status, Address, Scheduler }
-import RemoteConnection.getAddrString
+import akka.remote.testconductor.RemoteConnection.getAddrString
+import scala.collection.immutable
+import scala.concurrent.{ ExecutionContext, Await, Future }
 import scala.concurrent.duration._
+import scala.util.control.NoStackTrace
+import scala.reflect.classTag
 import akka.util.Timeout
 import org.jboss.netty.channel.{ Channel, SimpleChannelUpstreamHandler, ChannelHandlerContext, ChannelStateEvent, MessageEvent, WriteCompletionEvent, ExceptionEvent }
-import com.typesafe.config.ConfigFactory
-import java.util.concurrent.TimeUnit.MILLISECONDS
-import java.util.concurrent.TimeoutException
 import akka.pattern.{ ask, pipe, AskTimeoutException }
-import scala.util.control.NoStackTrace
 import akka.event.{ LoggingAdapter, Logging }
 import java.net.{ InetSocketAddress, ConnectException }
-import scala.reflect.classTag
-import concurrent.{ ExecutionContext, Await, Future }
 
 /**
  * The Player is the client component of the
@@ -67,15 +67,13 @@ trait Player { this: TestConductorExt ⇒
    * Enter the named barriers, one after the other, in the order given. Will
    * throw an exception in case of timeouts or other errors.
    */
-  def enter(name: String*) {
-    enter(Settings.BarrierTimeout, name)
-  }
+  def enter(name: String*): Unit = enter(Settings.BarrierTimeout, name.to[immutable.Seq])
 
   /**
    * Enter the named barriers, one after the other, in the order given. Will
    * throw an exception in case of timeouts or other errors.
    */
-  def enter(timeout: Timeout, name: Seq[String]) {
+  def enter(timeout: Timeout, name: immutable.Seq[String]) {
     system.log.debug("entering barriers " + name.mkString("(", ", ", ")"))
     val stop = Deadline.now + timeout.duration
     name foreach { b ⇒
diff --git a/akka-remote-tests/src/main/scala/akka/remote/testkit/MultiNodeSpec.scala b/akka-remote-tests/src/main/scala/akka/remote/testkit/MultiNodeSpec.scala
index c40a4e5a7b..e79ab4a1ee 100644
--- a/akka-remote-tests/src/main/scala/akka/remote/testkit/MultiNodeSpec.scala
+++ b/akka-remote-tests/src/main/scala/akka/remote/testkit/MultiNodeSpec.scala
@@ -7,16 +7,17 @@ import language.implicitConversions
 import language.postfixOps
 
 import java.net.InetSocketAddress
+import java.util.concurrent.TimeoutException
 import com.typesafe.config.{ ConfigObject, ConfigFactory, Config }
+import scala.concurrent.{ Await, Awaitable }
+import scala.util.control.NonFatal
+import scala.collection.immutable
 import akka.actor._
 import akka.util.Timeout
 import akka.remote.testconductor.{ TestConductorExt, TestConductor, RoleName }
 import akka.remote.RemoteActorRefProvider
 import akka.testkit._
-import scala.concurrent.{ Await, Awaitable }
-import scala.util.control.NonFatal
 import scala.concurrent.duration._
-import java.util.concurrent.TimeoutException
 import akka.remote.testconductor.RoleName
 import akka.remote.testconductor.TestConductorTransport
 import akka.actor.RootActorPath
@@ -30,7 +31,7 @@ abstract class MultiNodeConfig {
   private var _commonConf: Option[Config] = None
   private var _nodeConf = Map[RoleName, Config]()
   private var _roles = Vector[RoleName]()
-  private var _deployments = Map[RoleName, Seq[String]]()
+  private var _deployments = Map[RoleName, immutable.Seq[String]]()
   private var _allDeploy = Vector[String]()
   private var _testTransport = false
 
@@ -106,9 +107,9 @@ abstract class MultiNodeConfig {
     configs reduce (_ withFallback _)
   }
 
-  private[testkit] def deployments(node: RoleName): Seq[String] = (_deployments get node getOrElse Nil) ++ _allDeploy
+  private[testkit] def deployments(node: RoleName): immutable.Seq[String] = (_deployments get node getOrElse Nil) ++ _allDeploy
 
-  private[testkit] def roles: Seq[RoleName] = _roles
+  private[testkit] def roles: immutable.Seq[RoleName] = _roles
 
 }
 
@@ -234,7 +235,7 @@ object MultiNodeSpec {
  * `AskTimeoutException: sending to terminated ref breaks promises`. Using lazy
  * val is fine.
  */
-abstract class MultiNodeSpec(val myself: RoleName, _system: ActorSystem, _roles: Seq[RoleName], deployments: RoleName ⇒ Seq[String])
+abstract class MultiNodeSpec(val myself: RoleName, _system: ActorSystem, _roles: immutable.Seq[RoleName], deployments: RoleName ⇒ Seq[String])
   extends TestKit(_system) with MultiNodeSpecCallbacks {
 
   import MultiNodeSpec._
@@ -294,7 +295,7 @@ abstract class MultiNodeSpec(val myself: RoleName, _system: ActorSystem, _roles:
   /**
    * All registered roles
    */
-  def roles: Seq[RoleName] = _roles
+  def roles: immutable.Seq[RoleName] = _roles
 
   /**
    * TO BE DEFINED BY USER: Defines the number of participants required for starting the test. This
@@ -335,9 +336,10 @@ abstract class MultiNodeSpec(val myself: RoleName, _system: ActorSystem, _roles:
    * Enter the named barriers in the order given. Use the remaining duration from
    * the innermost enclosing `within` block or the default `BarrierTimeout`
    */
-  def enterBarrier(name: String*) {
-    testConductor.enter(Timeout.durationToTimeout(remainingOr(testConductor.Settings.BarrierTimeout.duration)), name)
-  }
+  def enterBarrier(name: String*): Unit =
+    testConductor.enter(
+      Timeout.durationToTimeout(remainingOr(testConductor.Settings.BarrierTimeout.duration)),
+      name.to[immutable.Seq])
 
   /**
    * Query the controller for the transport address of the given node (by role name) and
diff --git a/akka-remote/src/main/scala/akka/remote/RemoteActorRefProvider.scala b/akka-remote/src/main/scala/akka/remote/RemoteActorRefProvider.scala
index 4967978582..48fca0af08 100644
--- a/akka-remote/src/main/scala/akka/remote/RemoteActorRefProvider.scala
+++ b/akka-remote/src/main/scala/akka/remote/RemoteActorRefProvider.scala
@@ -70,7 +70,7 @@ class RemoteActorRefProvider(
 
     _transport = {
       val fqn = remoteSettings.RemoteTransport
-      val args = Seq(
+      val args = List(
         classOf[ExtendedActorSystem] -> system,
         classOf[RemoteActorRefProvider] -> this)
 
diff --git a/akka-remote/src/main/scala/akka/remote/netty/NettyRemoteSupport.scala b/akka-remote/src/main/scala/akka/remote/netty/NettyRemoteSupport.scala
index a65bac1a66..2a067237a7 100644
--- a/akka-remote/src/main/scala/akka/remote/netty/NettyRemoteSupport.scala
+++ b/akka-remote/src/main/scala/akka/remote/netty/NettyRemoteSupport.scala
@@ -8,7 +8,9 @@ import java.net.InetSocketAddress
 import java.util.concurrent.atomic.{ AtomicReference, AtomicBoolean }
 import java.util.concurrent.locks.ReentrantReadWriteLock
 import java.util.concurrent.Executors
-import scala.collection.mutable.HashMap
+import scala.collection.mutable
+import scala.collection.immutable
+import scala.util.control.NonFatal
 import org.jboss.netty.channel.group.{ DefaultChannelGroup, ChannelGroupFuture }
 import org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory
 import org.jboss.netty.channel.{ ChannelHandlerContext, Channel, DefaultChannelPipeline, ChannelHandler, ChannelPipelineFactory, ChannelLocal }
@@ -20,7 +22,6 @@ import org.jboss.netty.util.{ DefaultObjectSizeEstimator, HashedWheelTimer }
 import akka.event.Logging
 import akka.remote.RemoteProtocol.AkkaRemoteProtocol
 import akka.remote.{ RemoteTransportException, RemoteTransport, RemoteActorRefProvider, RemoteActorRef, RemoteServerStarted }
-import scala.util.control.NonFatal
 import akka.actor.{ ExtendedActorSystem, Address, ActorRef }
 import com.google.protobuf.MessageLite
 
@@ -53,7 +54,7 @@ private[akka] class NettyRemoteTransport(_system: ExtendedActorSystem, _provider
      * Construct a DefaultChannelPipeline from a sequence of handlers; to be used
      * in implementations of ChannelPipelineFactory.
      */
-    def apply(handlers: Seq[ChannelHandler]): DefaultChannelPipeline =
+    def apply(handlers: immutable.Seq[ChannelHandler]): DefaultChannelPipeline =
       (new DefaultChannelPipeline /: handlers) { (p, h) ⇒ p.addLast(Logging.simpleName(h.getClass), h); p }
 
     /**
@@ -69,7 +70,7 @@ private[akka] class NettyRemoteTransport(_system: ExtendedActorSystem, _provider
      * Construct a default protocol stack, excluding the “head” handler (i.e. the one which
      * actually dispatches the received messages to the local target actors).
      */
-    def defaultStack(withTimeout: Boolean, isClient: Boolean): Seq[ChannelHandler] =
+    def defaultStack(withTimeout: Boolean, isClient: Boolean): immutable.Seq[ChannelHandler] =
       (if (settings.EnableSSL) List(NettySSLSupport(settings, NettyRemoteTransport.this.log, isClient)) else Nil) :::
         (if (withTimeout) List(timeout) else Nil) :::
         msgFormat :::
@@ -138,7 +139,7 @@ private[akka] class NettyRemoteTransport(_system: ExtendedActorSystem, _provider
   def createPipeline(endpoint: ⇒ ChannelHandler, withTimeout: Boolean, isClient: Boolean): ChannelPipelineFactory =
     PipelineFactory(Seq(endpoint), withTimeout, isClient)
 
-  private val remoteClients = new HashMap[Address, RemoteClient]
+  private val remoteClients = new mutable.HashMap[Address, RemoteClient]
   private val clientsLock = new ReentrantReadWriteLock
 
   override protected def useUntrustedMode = remoteSettings.UntrustedMode
diff --git a/akka-remote/src/main/scala/akka/remote/security/provider/InternetSeedGenerator.scala b/akka-remote/src/main/scala/akka/remote/security/provider/InternetSeedGenerator.scala
index f049a4e678..b274c4c0b6 100644
--- a/akka-remote/src/main/scala/akka/remote/security/provider/InternetSeedGenerator.scala
+++ b/akka-remote/src/main/scala/akka/remote/security/provider/InternetSeedGenerator.scala
@@ -16,6 +16,7 @@
 package akka.remote.security.provider
 
 import org.uncommons.maths.random.{ SeedGenerator, SeedException, SecureRandomSeedGenerator, RandomDotOrgSeedGenerator, DevRandomSeedGenerator }
+import scala.collection.immutable
 
 /**
  * Internal API
@@ -33,8 +34,8 @@ object InternetSeedGenerator {
   /**Singleton instance. */
   private final val Instance: InternetSeedGenerator = new InternetSeedGenerator
   /**Delegate generators. */
-  private final val Generators: Seq[SeedGenerator] =
-    Seq(new RandomDotOrgSeedGenerator, // first try the Internet seed generator
+  private final val Generators: immutable.Seq[SeedGenerator] =
+    List(new RandomDotOrgSeedGenerator, // first try the Internet seed generator
       new SecureRandomSeedGenerator) // this is last because it always works
 }
 
diff --git a/akka-testkit/src/main/scala/akka/testkit/TestActorRef.scala b/akka-testkit/src/main/scala/akka/testkit/TestActorRef.scala
index 520f2557c7..132e3f5e78 100644
--- a/akka-testkit/src/main/scala/akka/testkit/TestActorRef.scala
+++ b/akka-testkit/src/main/scala/akka/testkit/TestActorRef.scala
@@ -138,7 +138,7 @@ object TestActorRef {
   def apply[T <: Actor](implicit t: ClassTag[T], system: ActorSystem): TestActorRef[T] = apply[T](randomName)
 
   def apply[T <: Actor](name: String)(implicit t: ClassTag[T], system: ActorSystem): TestActorRef[T] = apply[T](Props({
-    system.asInstanceOf[ExtendedActorSystem].dynamicAccess.createInstanceFor[T](t.runtimeClass, Seq()).recover({
+    system.asInstanceOf[ExtendedActorSystem].dynamicAccess.createInstanceFor[T](t.runtimeClass, Nil).recover({
       case exception ⇒ throw ActorInitializationException(null,
         "Could not instantiate Actor" +
           "\nMake sure Actor is NOT defined inside a class/trait," +
diff --git a/akka-testkit/src/main/scala/akka/testkit/TestEventListener.scala b/akka-testkit/src/main/scala/akka/testkit/TestEventListener.scala
index 1fdd339ca5..c46f15a26a 100644
--- a/akka-testkit/src/main/scala/akka/testkit/TestEventListener.scala
+++ b/akka-testkit/src/main/scala/akka/testkit/TestEventListener.scala
@@ -6,14 +6,15 @@ package akka.testkit
 import language.existentials
 
 import scala.util.matching.Regex
+import scala.collection.JavaConverters
+import scala.collection.immutable
+import scala.concurrent.duration.Duration
+import scala.reflect.ClassTag
 import akka.actor.{ DeadLetter, ActorSystem, Terminated, UnhandledMessage }
 import akka.dispatch.{ SystemMessage, Terminate }
 import akka.event.Logging.{ Warning, LogEvent, InitializeLogger, Info, Error, Debug, LoggerInitialized }
 import akka.event.Logging
 import java.lang.{ Iterable ⇒ JIterable }
-import scala.collection.JavaConverters
-import scala.concurrent.duration.Duration
-import scala.reflect.ClassTag
 import akka.actor.NoSerializationVerificationNeeded
 
 /**
@@ -38,22 +39,22 @@ sealed trait TestEvent
  */
 object TestEvent {
   object Mute {
-    def apply(filter: EventFilter, filters: EventFilter*): Mute = new Mute(filter +: filters.toSeq)
+    def apply(filter: EventFilter, filters: EventFilter*): Mute = new Mute(filter +: filters.to[immutable.Seq])
   }
-  case class Mute(filters: Seq[EventFilter]) extends TestEvent with NoSerializationVerificationNeeded {
+  case class Mute(filters: immutable.Seq[EventFilter]) extends TestEvent with NoSerializationVerificationNeeded {
     /**
      * Java API
      */
-    def this(filters: JIterable[EventFilter]) = this(JavaConverters.iterableAsScalaIterableConverter(filters).asScala.toSeq)
+    def this(filters: JIterable[EventFilter]) = this(JavaConverters.iterableAsScalaIterableConverter(filters).asScala.to[immutable.Seq])
   }
   object UnMute {
-    def apply(filter: EventFilter, filters: EventFilter*): UnMute = new UnMute(filter +: filters.toSeq)
+    def apply(filter: EventFilter, filters: EventFilter*): UnMute = new UnMute(filter +: filters.to[immutable.Seq])
   }
-  case class UnMute(filters: Seq[EventFilter]) extends TestEvent with NoSerializationVerificationNeeded {
+  case class UnMute(filters: immutable.Seq[EventFilter]) extends TestEvent with NoSerializationVerificationNeeded {
     /**
      * Java API
      */
-    def this(filters: JIterable[EventFilter]) = this(JavaConverters.iterableAsScalaIterableConverter(filters).asScala.toSeq)
+    def this(filters: JIterable[EventFilter]) = this(JavaConverters.iterableAsScalaIterableConverter(filters).asScala.to[immutable.Seq])
   }
 }
 
diff --git a/akka-testkit/src/main/scala/akka/testkit/TestKit.scala b/akka-testkit/src/main/scala/akka/testkit/TestKit.scala
index 4f6744b74b..e81acb23a3 100644
--- a/akka-testkit/src/main/scala/akka/testkit/TestKit.scala
+++ b/akka-testkit/src/main/scala/akka/testkit/TestKit.scala
@@ -5,15 +5,15 @@ package akka.testkit
 
 import language.postfixOps
 
+import scala.annotation.{ varargs, tailrec }
+import scala.collection.immutable
+import scala.concurrent.duration._
+import scala.reflect.ClassTag
+import java.util.concurrent.{ BlockingDeque, LinkedBlockingDeque, TimeUnit, atomic }
+import java.util.concurrent.atomic.AtomicInteger
 import akka.actor._
 import akka.actor.Actor._
-import scala.concurrent.duration._
-import java.util.concurrent.{ BlockingDeque, LinkedBlockingDeque, TimeUnit, atomic }
-import atomic.AtomicInteger
-import scala.annotation.tailrec
 import akka.util.{ Timeout, BoxedType }
-import scala.annotation.varargs
-import scala.reflect.ClassTag
 
 object TestActor {
   type Ignore = Option[PartialFunction[Any, Boolean]]
@@ -415,7 +415,7 @@ trait TestKitBase {
   /**
    * Same as `expectMsgAllOf(remaining, obj...)`, but correctly treating the timeFactor.
    */
-  def expectMsgAllOf[T](obj: T*): Seq[T] = expectMsgAllOf_internal(remaining, obj: _*)
+  def expectMsgAllOf[T](obj: T*): immutable.Seq[T] = expectMsgAllOf_internal(remaining, obj: _*)
 
   /**
    * Receive a number of messages from the test actor matching the given
@@ -430,19 +430,19 @@ trait TestKitBase {
    *   expectMsgAllOf(1 second, Result1(), Result2())
    * </pre>
    */
-  def expectMsgAllOf[T](max: FiniteDuration, obj: T*): Seq[T] = expectMsgAllOf_internal(max.dilated, obj: _*)
+  def expectMsgAllOf[T](max: FiniteDuration, obj: T*): immutable.Seq[T] = expectMsgAllOf_internal(max.dilated, obj: _*)
 
-  private def expectMsgAllOf_internal[T](max: FiniteDuration, obj: T*): Seq[T] = {
+  private def expectMsgAllOf_internal[T](max: FiniteDuration, obj: T*): immutable.Seq[T] = {
     val recv = receiveN_internal(obj.size, max)
     obj foreach (x ⇒ assert(recv exists (x == _), "not found " + x))
     recv foreach (x ⇒ assert(obj exists (x == _), "found unexpected " + x))
-    recv.asInstanceOf[Seq[T]]
+    recv.asInstanceOf[immutable.Seq[T]]
   }
 
   /**
    * Same as `expectMsgAllClassOf(remaining, obj...)`, but correctly treating the timeFactor.
    */
-  def expectMsgAllClassOf[T](obj: Class[_ <: T]*): Seq[T] = internalExpectMsgAllClassOf(remaining, obj: _*)
+  def expectMsgAllClassOf[T](obj: Class[_ <: T]*): immutable.Seq[T] = internalExpectMsgAllClassOf(remaining, obj: _*)
 
   /**
    * Receive a number of messages from the test actor matching the given
@@ -452,19 +452,19 @@ trait TestKitBase {
    * Wait time is bounded by the given duration, with an AssertionFailure
    * being thrown in case of timeout.
    */
-  def expectMsgAllClassOf[T](max: FiniteDuration, obj: Class[_ <: T]*): Seq[T] = internalExpectMsgAllClassOf(max.dilated, obj: _*)
+  def expectMsgAllClassOf[T](max: FiniteDuration, obj: Class[_ <: T]*): immutable.Seq[T] = internalExpectMsgAllClassOf(max.dilated, obj: _*)
 
-  private def internalExpectMsgAllClassOf[T](max: FiniteDuration, obj: Class[_ <: T]*): Seq[T] = {
+  private def internalExpectMsgAllClassOf[T](max: FiniteDuration, obj: Class[_ <: T]*): immutable.Seq[T] = {
     val recv = receiveN_internal(obj.size, max)
     obj foreach (x ⇒ assert(recv exists (_.getClass eq BoxedType(x)), "not found " + x))
     recv foreach (x ⇒ assert(obj exists (c ⇒ BoxedType(c) eq x.getClass), "found non-matching object " + x))
-    recv.asInstanceOf[Seq[T]]
+    recv.asInstanceOf[immutable.Seq[T]]
   }
 
   /**
    * Same as `expectMsgAllConformingOf(remaining, obj...)`, but correctly treating the timeFactor.
    */
-  def expectMsgAllConformingOf[T](obj: Class[_ <: T]*): Seq[T] = internalExpectMsgAllConformingOf(remaining, obj: _*)
+  def expectMsgAllConformingOf[T](obj: Class[_ <: T]*): immutable.Seq[T] = internalExpectMsgAllConformingOf(remaining, obj: _*)
 
   /**
    * Receive a number of messages from the test actor matching the given
@@ -477,13 +477,13 @@ trait TestKitBase {
    * Beware that one object may satisfy all given class constraints, which
    * may be counter-intuitive.
    */
-  def expectMsgAllConformingOf[T](max: FiniteDuration, obj: Class[_ <: T]*): Seq[T] = internalExpectMsgAllConformingOf(max.dilated, obj: _*)
+  def expectMsgAllConformingOf[T](max: FiniteDuration, obj: Class[_ <: T]*): immutable.Seq[T] = internalExpectMsgAllConformingOf(max.dilated, obj: _*)
 
-  private def internalExpectMsgAllConformingOf[T](max: FiniteDuration, obj: Class[_ <: T]*): Seq[T] = {
+  private def internalExpectMsgAllConformingOf[T](max: FiniteDuration, obj: Class[_ <: T]*): immutable.Seq[T] = {
     val recv = receiveN_internal(obj.size, max)
     obj foreach (x ⇒ assert(recv exists (BoxedType(x) isInstance _), "not found " + x))
     recv foreach (x ⇒ assert(obj exists (c ⇒ BoxedType(c) isInstance x), "found non-matching object " + x))
-    recv.asInstanceOf[Seq[T]]
+    recv.asInstanceOf[immutable.Seq[T]]
   }
 
   /**
@@ -520,7 +520,7 @@ trait TestKitBase {
    * assert(series == (1 to 7).toList)
    * </pre>
    */
-  def receiveWhile[T](max: Duration = Duration.Undefined, idle: Duration = Duration.Inf, messages: Int = Int.MaxValue)(f: PartialFunction[AnyRef, T]): Seq[T] = {
+  def receiveWhile[T](max: Duration = Duration.Undefined, idle: Duration = Duration.Inf, messages: Int = Int.MaxValue)(f: PartialFunction[AnyRef, T]): immutable.Seq[T] = {
     val stop = now + remainingOrDilated(max)
     var msg: Message = NullMessage
 
@@ -553,14 +553,14 @@ trait TestKitBase {
    * Same as `receiveN(n, remaining)` but correctly taking into account
    * Duration.timeFactor.
    */
-  def receiveN(n: Int): Seq[AnyRef] = receiveN_internal(n, remaining)
+  def receiveN(n: Int): immutable.Seq[AnyRef] = receiveN_internal(n, remaining)
 
   /**
    * Receive N messages in a row before the given deadline.
    */
-  def receiveN(n: Int, max: FiniteDuration): Seq[AnyRef] = receiveN_internal(n, max.dilated)
+  def receiveN(n: Int, max: FiniteDuration): immutable.Seq[AnyRef] = receiveN_internal(n, max.dilated)
 
-  private def receiveN_internal(n: Int, max: Duration): Seq[AnyRef] = {
+  private def receiveN_internal(n: Int, max: Duration): immutable.Seq[AnyRef] = {
     val stop = max + now
     for { x ← 1 to n } yield {
       val timeout = stop - now
diff --git a/akka-testkit/src/main/scala/akka/testkit/package.scala b/akka-testkit/src/main/scala/akka/testkit/package.scala
index 38d6d853af..ff8926154e 100644
--- a/akka-testkit/src/main/scala/akka/testkit/package.scala
+++ b/akka-testkit/src/main/scala/akka/testkit/package.scala
@@ -4,14 +4,16 @@ import language.implicitConversions
 
 import akka.actor.ActorSystem
 import scala.concurrent.duration.{ Duration, FiniteDuration }
-import java.util.concurrent.TimeUnit.MILLISECONDS
 import scala.reflect.ClassTag
+import scala.collection.immutable
+import java.util.concurrent.TimeUnit.MILLISECONDS
 
 package object testkit {
   def filterEvents[T](eventFilters: Iterable[EventFilter])(block: ⇒ T)(implicit system: ActorSystem): T = {
     def now = System.currentTimeMillis
 
-    system.eventStream.publish(TestEvent.Mute(eventFilters.toSeq))
+    system.eventStream.publish(TestEvent.Mute(eventFilters.to[immutable.Seq]))
+
     try {
       val result = block
 
@@ -23,7 +25,7 @@ package object testkit {
 
       result
     } finally {
-      system.eventStream.publish(TestEvent.UnMute(eventFilters.toSeq))
+      system.eventStream.publish(TestEvent.UnMute(eventFilters.to[immutable.Seq]))
     }
   }
 
diff --git a/akka-transactor/src/test/java/akka/transactor/UntypedCoordinatedIncrementTest.java b/akka-transactor/src/test/java/akka/transactor/UntypedCoordinatedIncrementTest.java
index 5aecd341e0..27323787aa 100644
--- a/akka-transactor/src/test/java/akka/transactor/UntypedCoordinatedIncrementTest.java
+++ b/akka-transactor/src/test/java/akka/transactor/UntypedCoordinatedIncrementTest.java
@@ -32,7 +32,7 @@ import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 
 import scala.collection.JavaConverters;
-import scala.collection.Seq;
+import scala.collection.immutable.Seq;
 
 public class UntypedCoordinatedIncrementTest {
   private static ActorSystem system;
@@ -110,6 +110,6 @@ public class UntypedCoordinatedIncrementTest {
   }
 
   public <A> Seq<A> seq(A... args) {
-    return JavaConverters.collectionAsScalaIterableConverter(Arrays.asList(args)).asScala().toSeq();
+    return JavaConverters.collectionAsScalaIterableConverter(Arrays.asList(args)).asScala().toList();
   }
 }
diff --git a/akka-transactor/src/test/java/akka/transactor/UntypedTransactorTest.java b/akka-transactor/src/test/java/akka/transactor/UntypedTransactorTest.java
index 5aae61d9c1..3b841e300b 100644
--- a/akka-transactor/src/test/java/akka/transactor/UntypedTransactorTest.java
+++ b/akka-transactor/src/test/java/akka/transactor/UntypedTransactorTest.java
@@ -32,7 +32,7 @@ import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 
 import scala.collection.JavaConverters;
-import scala.collection.Seq;
+import scala.collection.immutable.Seq;
 
 public class UntypedTransactorTest {
 
@@ -120,6 +120,6 @@ public class UntypedTransactorTest {
   public <A> Seq<A> seq(A... args) {
     return JavaConverters
         .collectionAsScalaIterableConverter(Arrays.asList(args)).asScala()
-        .toSeq();
+        .toList();
   }
 }
diff --git a/akka-transactor/src/test/scala/akka/transactor/CoordinatedIncrementSpec.scala b/akka-transactor/src/test/scala/akka/transactor/CoordinatedIncrementSpec.scala
index 1aa9fb555c..6dad1079a3 100644
--- a/akka-transactor/src/test/scala/akka/transactor/CoordinatedIncrementSpec.scala
+++ b/akka-transactor/src/test/scala/akka/transactor/CoordinatedIncrementSpec.scala
@@ -6,12 +6,13 @@ package akka.transactor
 
 import org.scalatest.BeforeAndAfterAll
 
-import akka.actor._
 import scala.concurrent.Await
 import scala.concurrent.duration._
+import scala.concurrent.stm._
+import scala.collection.immutable
+import akka.actor._
 import akka.util.Timeout
 import akka.testkit._
-import scala.concurrent.stm._
 import akka.pattern.{ AskTimeoutException, ask }
 
 object CoordinatedIncrement {
@@ -30,7 +31,7 @@ object CoordinatedIncrement {
     }
   """
 
-  case class Increment(friends: Seq[ActorRef])
+  case class Increment(friends: immutable.Seq[ActorRef])
   case object GetCount
 
   class Counter(name: String) extends Actor {
diff --git a/akka-transactor/src/test/scala/akka/transactor/FickleFriendsSpec.scala b/akka-transactor/src/test/scala/akka/transactor/FickleFriendsSpec.scala
index a087ab5b6d..eb75247164 100644
--- a/akka-transactor/src/test/scala/akka/transactor/FickleFriendsSpec.scala
+++ b/akka-transactor/src/test/scala/akka/transactor/FickleFriendsSpec.scala
@@ -8,21 +8,22 @@ import language.postfixOps
 
 import org.scalatest.BeforeAndAfterAll
 
-import akka.actor._
 import scala.concurrent.Await
 import scala.concurrent.duration._
+import scala.concurrent.stm._
+import scala.collection.immutable
+import scala.util.Random.{ nextInt ⇒ random }
+import scala.util.control.NonFatal
+import akka.actor._
 import akka.testkit._
 import akka.testkit.TestEvent.Mute
-import scala.concurrent.stm._
-import scala.util.Random.{ nextInt ⇒ random }
 import java.util.concurrent.CountDownLatch
 import akka.pattern.{ AskTimeoutException, ask }
 import akka.util.Timeout
-import scala.util.control.NonFatal
 
 object FickleFriends {
-  case class FriendlyIncrement(friends: Seq[ActorRef], timeout: Timeout, latch: CountDownLatch)
-  case class Increment(friends: Seq[ActorRef])
+  case class FriendlyIncrement(friends: immutable.Seq[ActorRef], timeout: Timeout, latch: CountDownLatch)
+  case class Increment(friends: immutable.Seq[ActorRef])
   case object GetCount
 
   /**
@@ -120,7 +121,7 @@ class FickleFriendsSpec extends AkkaSpec with BeforeAndAfterAll {
 
   "Coordinated fickle friends" should {
     "eventually succeed to increment all counters by one" in {
-      val ignoreExceptions = Seq(
+      val ignoreExceptions = immutable.Seq(
         EventFilter[ExpectedFailureException](),
         EventFilter[CoordinatedTransactionException](),
         EventFilter[AskTimeoutException]())
diff --git a/akka-transactor/src/test/scala/akka/transactor/TransactorSpec.scala b/akka-transactor/src/test/scala/akka/transactor/TransactorSpec.scala
index 4fd05a0e1e..0de8a13d97 100644
--- a/akka-transactor/src/test/scala/akka/transactor/TransactorSpec.scala
+++ b/akka-transactor/src/test/scala/akka/transactor/TransactorSpec.scala
@@ -7,15 +7,16 @@ package akka.transactor
 import language.postfixOps
 
 import akka.actor._
+import scala.collection.immutable
 import scala.concurrent.Await
 import scala.concurrent.duration._
+import scala.concurrent.stm._
 import akka.util.Timeout
 import akka.testkit._
-import scala.concurrent.stm._
 import akka.pattern.{ AskTimeoutException, ask }
 
 object TransactorIncrement {
-  case class Increment(friends: Seq[ActorRef], latch: TestLatch)
+  case class Increment(friends: immutable.Seq[ActorRef], latch: TestLatch)
   case object GetCount
 
   class Counter(name: String) extends Transactor {
diff --git a/akka-zeromq/src/main/scala/akka/zeromq/ConcurrentSocketActor.scala b/akka-zeromq/src/main/scala/akka/zeromq/ConcurrentSocketActor.scala
index 20c8b2d723..a9efa56c1e 100644
--- a/akka-zeromq/src/main/scala/akka/zeromq/ConcurrentSocketActor.scala
+++ b/akka-zeromq/src/main/scala/akka/zeromq/ConcurrentSocketActor.scala
@@ -6,13 +6,14 @@ package akka.zeromq
 import org.zeromq.ZMQ.{ Socket, Poller }
 import org.zeromq.{ ZMQ ⇒ JZMQ }
 import akka.actor._
+import scala.collection.immutable
+import scala.annotation.tailrec
 import scala.concurrent.{ Promise, Future }
 import scala.concurrent.duration.Duration
-import scala.annotation.tailrec
 import scala.collection.mutable.ListBuffer
+import scala.util.control.NonFatal
 import akka.event.Logging
 import java.util.concurrent.TimeUnit
-import scala.util.control.NonFatal
 
 private[zeromq] object ConcurrentSocketActor {
   private sealed trait PollMsg
@@ -25,7 +26,7 @@ private[zeromq] object ConcurrentSocketActor {
 
   private val DefaultContext = Context()
 }
-private[zeromq] class ConcurrentSocketActor(params: Seq[SocketOption]) extends Actor {
+private[zeromq] class ConcurrentSocketActor(params: immutable.Seq[SocketOption]) extends Actor {
 
   import ConcurrentSocketActor._
   private val noBytes = Array[Byte]()
@@ -40,7 +41,7 @@ private[zeromq] class ConcurrentSocketActor(params: Seq[SocketOption]) extends A
   private val socket: Socket = zmqContext.socket(socketType)
   private val poller: Poller = zmqContext.poller
 
-  private val pendingSends = new ListBuffer[Seq[Frame]]
+  private val pendingSends = new ListBuffer[immutable.Seq[Frame]]
 
   def receive = {
     case m: PollMsg         ⇒ doPoll(m)
@@ -151,7 +152,7 @@ private[zeromq] class ConcurrentSocketActor(params: Seq[SocketOption]) extends A
     }
   } finally notifyListener(Closed)
 
-  @tailrec private def flushMessage(i: Seq[Frame]): Boolean =
+  @tailrec private def flushMessage(i: immutable.Seq[Frame]): Boolean =
     if (i.isEmpty)
       true
     else {
@@ -198,7 +199,7 @@ private[zeromq] class ConcurrentSocketActor(params: Seq[SocketOption]) extends A
       case frames ⇒ notifyListener(deserializer(frames)); doPoll(mode, togo - 1)
     }
 
-  @tailrec private def receiveMessage(mode: PollMsg, currentFrames: Vector[Frame] = Vector.empty): Seq[Frame] =
+  @tailrec private def receiveMessage(mode: PollMsg, currentFrames: Vector[Frame] = Vector.empty): immutable.Seq[Frame] =
     if (mode == PollCareful && (poller.poll(0) <= 0)) {
       if (currentFrames.isEmpty) currentFrames else throw new IllegalStateException("Received partial transmission!")
     } else {
diff --git a/akka-zeromq/src/main/scala/akka/zeromq/SocketOption.scala b/akka-zeromq/src/main/scala/akka/zeromq/SocketOption.scala
index f935a9c31d..b70c245327 100644
--- a/akka-zeromq/src/main/scala/akka/zeromq/SocketOption.scala
+++ b/akka-zeromq/src/main/scala/akka/zeromq/SocketOption.scala
@@ -4,9 +4,10 @@
 package akka.zeromq
 
 import com.google.protobuf.Message
-import org.zeromq.{ ZMQ ⇒ JZMQ }
 import akka.actor.ActorRef
 import scala.concurrent.duration._
+import scala.collection.immutable
+import org.zeromq.{ ZMQ ⇒ JZMQ }
 import org.zeromq.ZMQ.{ Poller, Socket }
 
 /**
@@ -36,7 +37,7 @@ sealed trait SocketConnectOption extends SocketOption {
  * A base trait for pubsub options for the ZeroMQ socket
  */
 sealed trait PubSubOption extends SocketOption {
-  def payload: Seq[Byte]
+  def payload: immutable.Seq[Byte]
 }
 
 /**
@@ -79,7 +80,7 @@ class Context(numIoThreads: Int) extends SocketMeta {
  * A base trait for message deserializers
  */
 trait Deserializer extends SocketOption {
-  def apply(frames: Seq[Frame]): Any
+  def apply(frames: immutable.Seq[Frame]): Any
 }
 
 /**
@@ -172,12 +173,12 @@ case class Bind(endpoint: String) extends SocketConnectOption
  *
  * @param payload the topic to subscribe to
  */
-case class Subscribe(payload: Seq[Byte]) extends PubSubOption {
-  def this(topic: String) = this(topic.getBytes("UTF-8"))
+case class Subscribe(payload: immutable.Seq[Byte]) extends PubSubOption {
+  def this(topic: String) = this(topic.getBytes("UTF-8").to[immutable.Seq])
 }
 object Subscribe {
   def apply(topic: String): Subscribe = new Subscribe(topic)
-  val all = Subscribe(Seq.empty)
+  val all = Subscribe("")
 }
 
 /**
@@ -189,8 +190,8 @@ object Subscribe {
  *
  * @param payload
  */
-case class Unsubscribe(payload: Seq[Byte]) extends PubSubOption {
-  def this(topic: String) = this(topic.getBytes("UTF-8"))
+case class Unsubscribe(payload: immutable.Seq[Byte]) extends PubSubOption {
+  def this(topic: String) = this(topic.getBytes("UTF-8").to[immutable.Seq])
 }
 object Unsubscribe {
   def apply(topic: String): Unsubscribe = new Unsubscribe(topic)
@@ -200,17 +201,17 @@ object Unsubscribe {
  * Send a message over the zeromq socket
  * @param frames
  */
-case class Send(frames: Seq[Frame]) extends Request
+case class Send(frames: immutable.Seq[Frame]) extends Request
 
 /**
  * A message received over the zeromq socket
  * @param frames
  */
-case class ZMQMessage(frames: Seq[Frame]) {
+case class ZMQMessage(frames: immutable.Seq[Frame]) {
 
-  def this(frame: Frame) = this(Seq(frame))
-  def this(frame1: Frame, frame2: Frame) = this(Seq(frame1, frame2))
-  def this(frameArray: Array[Frame]) = this(frameArray.toSeq)
+  def this(frame: Frame) = this(List(frame))
+  def this(frame1: Frame, frame2: Frame) = this(List(frame1, frame2))
+  def this(frameArray: Array[Frame]) = this(frameArray.to[immutable.Seq])
 
   /**
    * Convert the bytes in the first frame to a String, using specified charset.
@@ -224,8 +225,9 @@ case class ZMQMessage(frames: Seq[Frame]) {
   def payload(frameIndex: Int): Array[Byte] = frames(frameIndex).payload.toArray
 }
 object ZMQMessage {
-  def apply(bytes: Array[Byte]): ZMQMessage = ZMQMessage(Seq(Frame(bytes)))
-  def apply(message: Message): ZMQMessage = ZMQMessage(message.toByteArray)
+  def apply(bytes: Array[Byte]): ZMQMessage = new ZMQMessage(List(Frame(bytes)))
+  def apply(frames: Frame*): ZMQMessage = new ZMQMessage(frames.to[immutable.Seq])
+  def apply(message: Message): ZMQMessage = apply(message.toByteArray)
 }
 
 /**
diff --git a/akka-zeromq/src/main/scala/akka/zeromq/ZMQMessageDeserializer.scala b/akka-zeromq/src/main/scala/akka/zeromq/ZMQMessageDeserializer.scala
index 2d41424e88..d0141bf515 100644
--- a/akka-zeromq/src/main/scala/akka/zeromq/ZMQMessageDeserializer.scala
+++ b/akka-zeromq/src/main/scala/akka/zeromq/ZMQMessageDeserializer.scala
@@ -3,7 +3,10 @@
  */
 package akka.zeromq
 
+import scala.collection.immutable
+
 object Frame {
+  def apply(bytes: Array[Byte]): Frame = new Frame(bytes)
   def apply(text: String): Frame = new Frame(text)
 }
 
@@ -11,8 +14,8 @@ object Frame {
  * A single message frame of a zeromq message
  * @param payload
  */
-case class Frame(payload: Seq[Byte]) {
-  def this(bytes: Array[Byte]) = this(bytes.toSeq)
+case class Frame(payload: immutable.Seq[Byte]) {
+  def this(bytes: Array[Byte]) = this(bytes.to[immutable.Seq])
   def this(text: String) = this(text.getBytes("UTF-8"))
 }
 
@@ -20,5 +23,5 @@ case class Frame(payload: Seq[Byte]) {
  * Deserializes ZeroMQ messages into an immutable sequence of frames
  */
 class ZMQMessageDeserializer extends Deserializer {
-  def apply(frames: Seq[Frame]): ZMQMessage = ZMQMessage(frames)
+  def apply(frames: immutable.Seq[Frame]): ZMQMessage = ZMQMessage(frames)
 }
diff --git a/akka-zeromq/src/main/scala/akka/zeromq/ZeroMQExtension.scala b/akka-zeromq/src/main/scala/akka/zeromq/ZeroMQExtension.scala
index 85e05e54f3..bc40ea580b 100644
--- a/akka-zeromq/src/main/scala/akka/zeromq/ZeroMQExtension.scala
+++ b/akka-zeromq/src/main/scala/akka/zeromq/ZeroMQExtension.scala
@@ -7,6 +7,7 @@ import org.zeromq.{ ZMQ ⇒ JZMQ }
 import org.zeromq.ZMQ.Poller
 import akka.actor._
 import akka.pattern.ask
+import scala.collection.immutable
 import scala.concurrent.Await
 import scala.concurrent.duration.Duration
 import java.util.concurrent.TimeUnit
@@ -66,7 +67,8 @@ class ZeroMQExtension(system: ActorSystem) extends Extension {
       case s: SocketType.ZMQSocketType ⇒ true
       case _                           ⇒ false
     }, "A socket type is required")
-    Props(new ConcurrentSocketActor(socketParameters)).withDispatcher("akka.zeromq.socket-dispatcher")
+    val params = socketParameters.to[immutable.Seq]
+    Props(new ConcurrentSocketActor(params)).withDispatcher("akka.zeromq.socket-dispatcher")
   }
 
   /**
diff --git a/akka-zeromq/src/test/scala/akka/zeromq/ConcurrentSocketActorSpec.scala b/akka-zeromq/src/test/scala/akka/zeromq/ConcurrentSocketActorSpec.scala
index 68123761c5..6feaffd6d6 100644
--- a/akka-zeromq/src/test/scala/akka/zeromq/ConcurrentSocketActorSpec.scala
+++ b/akka-zeromq/src/test/scala/akka/zeromq/ConcurrentSocketActorSpec.scala
@@ -51,7 +51,7 @@ class ConcurrentSocketActorSpec extends AkkaSpec {
       val msgGenerator = system.scheduler.schedule(100 millis, 10 millis, new Runnable {
         var number = 0
         def run() {
-          publisher ! ZMQMessage(Seq(Frame(number.toString.getBytes), Frame(Seq())))
+          publisher ! ZMQMessage(Frame(number.toString), Frame(Nil))
           number += 1
         }
       })
@@ -88,8 +88,8 @@ class ConcurrentSocketActorSpec extends AkkaSpec {
 
       try {
         replierProbe.expectMsg(Connecting)
-        val request = ZMQMessage(Seq(Frame("Request")))
-        val reply = ZMQMessage(Seq(Frame("Reply")))
+        val request = ZMQMessage(Frame("Request"))
+        val reply = ZMQMessage(Frame("Reply"))
 
         requester ! request
         replierProbe.expectMsg(request)
@@ -112,7 +112,7 @@ class ConcurrentSocketActorSpec extends AkkaSpec {
 
       try {
         pullerProbe.expectMsg(Connecting)
-        val message = ZMQMessage(Seq(Frame("Pushed message")))
+        val message = ZMQMessage(Frame("Pushed message"))
 
         pusher ! message
         pullerProbe.expectMsg(message)