Scala 2.13.0 rc2 (#26967)

.travis.yml

@@ -4,7 +4,7 @@ sudo: false
 
 scala:
   - "2.12.8"
-  - "2.13.0-M5"
+  - "2.13.0-RC2"
 
 before_install:
   # using jabba for custom jdk management

akka-actor-testkit-typed/src/main/scala/akka/actor/testkit/typed/CapturedLogEvent.scala

@@ -11,7 +11,7 @@ import akka.annotation.InternalApi
 import akka.event.Logging.LogLevel
 import akka.util.OptionVal
 
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.compat.java8.OptionConverters._
 
 /**

akka-actor-testkit-typed/src/main/scala/akka/actor/testkit/typed/internal/BehaviorTestKitImpl.scala

@@ -13,7 +13,7 @@ import akka.actor.testkit.typed.{ CapturedLogEvent, Effect }
 import akka.actor.testkit.typed.Effect._
 
 import scala.annotation.tailrec
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.collection.immutable
 import scala.reflect.ClassTag
 import scala.util.control.Exception.Catcher

akka-actor-testkit-typed/src/main/scala/akka/actor/testkit/typed/internal/TestProbeImpl.scala

@@ -12,7 +12,7 @@ import java.util.function.Supplier
 import java.util.{ List => JList }
 
 import scala.annotation.tailrec
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.collection.immutable
 import scala.concurrent.Await
 import scala.concurrent.duration._

akka-actor-testkit-typed/src/main/scala/akka/actor/testkit/typed/javadsl/TestInbox.scala

@@ -10,7 +10,7 @@ import akka.actor.testkit.typed.internal.TestInboxImpl
 
 import java.util.concurrent.ThreadLocalRandom
 
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.collection.immutable
 
 object TestInbox {

akka-actor-tests/src/test/java/akka/japi/ThrowablesTest.java

@@ -14,14 +14,11 @@ public class ThrowablesTest {
     Assert.assertTrue(Throwables.isNonFatal(new IllegalArgumentException("isNonFatal")));
   }
 
-  private static class ControlThrowableImpl extends Throwable implements ControlThrowable {}
-
   @Test
   public void testIsFatal() {
     Assert.assertTrue(Throwables.isFatal(new StackOverflowError("fatal")));
     Assert.assertTrue(Throwables.isFatal(new ThreadDeath()));
     Assert.assertTrue(Throwables.isFatal(new InterruptedException("fatal")));
     Assert.assertTrue(Throwables.isFatal(new LinkageError("fatal")));
-    Assert.assertTrue(Throwables.isFatal(new ControlThrowableImpl()));
   }
 }

akka-actor-tests/src/test/scala/akka/actor/ActorSelectionSpec.scala

@@ -95,7 +95,7 @@ class ActorSelectionSpec extends AkkaSpec with DefaultTimeout {
       identify(system.child("c2").child("c21")) should ===(Some(c21)) // test Java API
       identify(system / Seq("c2", "c21")) should ===(Some(c21))
 
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
       identify(system.descendant(Seq("c2", "c21").asJava)) // test Java API
     }
 
@@ -244,7 +244,7 @@ class ActorSelectionSpec extends AkkaSpec with DefaultTimeout {
     }
 
     "return deadLetters or ActorIdentity(None), respectively, for non-existing paths" in {
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
 
       def checkOne(looker: ActorRef, query: Query, result: Option[ActorRef]): Unit = {
         val lookup = askNode(looker, query)

akka-actor-tests/src/test/scala/akka/actor/ActorWithStashSpec.scala

@@ -15,7 +15,7 @@ import com.github.ghik.silencer.silent
 
 import scala.concurrent.duration._
 import org.scalatest.BeforeAndAfterEach
-import org.scalatestplus.junit.JUnitSuiteLike
+import org.scalatest.junit.JUnitSuiteLike
 
 object ActorWithStashSpec {
 
@@ -102,6 +102,7 @@ object ActorWithStashSpec {
 
 }
 
+@silent
 class JavaActorWithStashSpec extends StashJavaAPI with JUnitSuiteLike
 
 @silent

akka-actor-tests/src/test/scala/akka/actor/CoordinatedShutdownSpec.scala

@@ -15,7 +15,8 @@ import akka.testkit.{ AkkaSpec, EventFilter, TestKit }
 import com.typesafe.config.{ Config, ConfigFactory }
 import akka.actor.CoordinatedShutdown.Phase
 import akka.actor.CoordinatedShutdown.UnknownReason
-import scala.collection.JavaConverters._
+
+import akka.util.ccompat.JavaConverters._
 import scala.concurrent.Promise
 import java.util.concurrent.TimeoutException
 

akka-actor-tests/src/test/scala/akka/actor/ExtensionSpec.scala

@@ -10,10 +10,12 @@ import akka.testkit.EventFilter
 import akka.testkit.TestKit._
 import com.typesafe.config.ConfigFactory
 import org.scalatest.{ Matchers, WordSpec }
-import org.scalatestplus.junit.JUnitSuiteLike
+import org.scalatest.junit.JUnitSuiteLike
 
 import scala.util.control.NoStackTrace
 
+import com.github.ghik.silencer.silent
+@silent
 class JavaExtensionSpec extends JavaExtension with JUnitSuiteLike
 
 object TestExtension extends ExtensionId[TestExtension] with ExtensionIdProvider {

akka-actor-tests/src/test/scala/akka/actor/FSMActorSpec.scala

@@ -251,7 +251,7 @@ class FSMActorSpec extends AkkaSpec(Map("akka.actor.debug.fsm" -> true)) with Im
     }
 
     "log events and transitions if asked to do so" in {
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
       val config = ConfigFactory
         .parseMap(Map(
           "akka.loglevel" -> "DEBUG",

akka-actor-tests/src/test/scala/akka/actor/FSMTransitionSpec.scala

@@ -27,7 +27,7 @@ object FSMTransitionSpec {
   }
 
   class MyFSM(target: ActorRef) extends Actor with FSM[Int, Unit] {
-    startWith(0, Unit)
+    startWith(0, ())
     when(0) {
       case Event("tick", _) => goto(1)
     }

akka-actor-tests/src/test/scala/akka/actor/JavaAPISpec.scala

@@ -4,6 +4,8 @@
 
 package akka.actor
 
-import org.scalatestplus.junit.JUnitSuiteLike
+import org.scalatest.junit.JUnitSuiteLike
 
+import com.github.ghik.silencer.silent
+@silent
 class JavaAPISpec extends JavaAPI with JUnitSuiteLike

akka-actor-tests/src/test/scala/akka/actor/dispatch/ActorModelSpec.scala

@@ -409,7 +409,7 @@ abstract class ActorModelSpec(config: String) extends AkkaSpec(config) with Defa
                   System.err.println(
                     "Teammates left: " + team.size + " stopLatch: " + stopLatch.getCount + " inhab:" + dispatcher.inhabitants)
 
-                  import scala.collection.JavaConverters._
+                  import akka.util.ccompat.JavaConverters._
                   team.asScala.toList.sortBy(_.self.path).foreach { cell: ActorCell =>
                     System.err.println(
                       " - " + cell.self.path + " " + cell.isTerminated + " " + cell.mailbox.currentStatus + " "
@@ -452,7 +452,7 @@ abstract class ActorModelSpec(config: String) extends AkkaSpec(config) with Defa
         val f6 = a ? Reply("bar2")
 
         val c = system.scheduler.scheduleOnce(2.seconds) {
-          import collection.JavaConverters._
+          import akka.util.ccompat.JavaConverters._
           Thread.getAllStackTraces().asScala.foreach {
             case (thread, stack) =>
               println(s"$thread:")

akka-actor-tests/src/test/scala/akka/actor/dispatch/DispatchersSpec.scala

@@ -4,7 +4,6 @@
 
 package akka.actor.dispatch
 
-import scala.collection.JavaConverters.mapAsJavaMapConverter
 import scala.reflect.ClassTag
 import com.typesafe.config.Config
 import com.typesafe.config.ConfigFactory
@@ -122,6 +121,8 @@ class DispatchersSpec extends AkkaSpec(DispatchersSpec.config) with ImplicitSend
   val defaultDispatcherConfig = settings.config.getConfig("akka.actor.default-dispatcher")
 
   lazy val allDispatchers: Map[String, MessageDispatcher] = {
+    import akka.util.ccompat.JavaConverters._
+
     validTypes
       .map(t => (t, from(ConfigFactory.parseMap(Map(tipe -> t, id -> t).asJava).withFallback(defaultDispatcherConfig))))
       .toMap
@@ -160,6 +161,7 @@ class DispatchersSpec extends AkkaSpec(DispatchersSpec.config) with ImplicitSend
     }
 
     "throw ConfigurationException if type does not exist" in {
+      import akka.util.ccompat.JavaConverters._
       intercept[ConfigurationException] {
         from(
           ConfigFactory

akka-actor-tests/src/test/scala/akka/dispatch/PriorityDispatcherSpec.scala

@@ -13,6 +13,9 @@ import akka.util.unused
 import scala.concurrent.duration._
 
 object PriorityDispatcherSpec {
+
+  case object Result
+
   val config = """
     unbounded-prio-dispatcher {
       mailbox-type = "akka.dispatch.PriorityDispatcherSpec$Unbounded"
@@ -24,19 +27,20 @@ object PriorityDispatcherSpec {
 
   class Unbounded(@unused settings: ActorSystem.Settings, @unused config: Config)
       extends UnboundedPriorityMailbox(PriorityGenerator({
-        case i: Int   => i //Reverse order
+        case i: Int => i //Reverse order
-        case "Result" => Int.MaxValue
+        case Result => Int.MaxValue
       }: Any => Int))
 
   class Bounded(@unused settings: ActorSystem.Settings, @unused config: Config)
       extends BoundedPriorityMailbox(PriorityGenerator({
-        case i: Int   => i //Reverse order
+        case i: Int => i //Reverse order
-        case "Result" => Int.MaxValue
+        case Result => Int.MaxValue
       }: Any => Int), 1000, 10 seconds)
 
 }
 
 class PriorityDispatcherSpec extends AkkaSpec(PriorityDispatcherSpec.config) with DefaultTimeout {
+  import PriorityDispatcherSpec._
 
   "A PriorityDispatcher" must {
     "Order it's messages according to the specified comparator using an unbounded mailbox" in {
@@ -66,11 +70,11 @@ class PriorityDispatcherSpec extends AkkaSpec(PriorityDispatcherSpec.config) wit
           self ! m
         }
 
-        self.tell("Result", testActor)
+        self.tell(Result, testActor)
 
         def receive = {
-          case i: Int   => acc += i
+          case i: Int => acc += i
-          case "Result" => sender() ! acc.toList
+          case Result => sender() ! acc.toList
         }
       }).withDispatcher(dispatcherKey))
 

akka-actor-tests/src/test/scala/akka/dispatch/StablePriorityDispatcherSpec.scala

@@ -13,6 +13,8 @@ import akka.util.unused
 import scala.concurrent.duration._
 
 object StablePriorityDispatcherSpec {
+  case object Result
+
   val config = """
     unbounded-stable-prio-dispatcher {
       mailbox-type = "akka.dispatch.StablePriorityDispatcherSpec$Unbounded"
@@ -26,19 +28,20 @@ object StablePriorityDispatcherSpec {
       extends UnboundedStablePriorityMailbox(PriorityGenerator({
         case i: Int if i <= 100 => i // Small integers have high priority
         case _: Int             => 101 // Don't care for other integers
-        case "Result"           => Int.MaxValue
+        case Result             => Int.MaxValue
       }: Any => Int))
 
   class Bounded(@unused settings: ActorSystem.Settings, @unused config: Config)
       extends BoundedStablePriorityMailbox(PriorityGenerator({
         case i: Int if i <= 100 => i // Small integers have high priority
         case _: Int             => 101 // Don't care for other integers
-        case "Result"           => Int.MaxValue
+        case Result             => Int.MaxValue
       }: Any => Int), 1000, 10 seconds)
 
 }
 
 class StablePriorityDispatcherSpec extends AkkaSpec(StablePriorityDispatcherSpec.config) with DefaultTimeout {
+  import StablePriorityDispatcherSpec._
 
   "A StablePriorityDispatcher" must {
     "Order its messages according to the specified comparator while preserving FIFO for equal priority messages, " +
@@ -70,11 +73,11 @@ class StablePriorityDispatcherSpec extends AkkaSpec(StablePriorityDispatcherSpec
             self ! m
           }
 
-          self.tell("Result", testActor)
+          self.tell(Result, testActor)
 
           def receive = {
-            case i: Int   => acc += i
+            case i: Int => acc += i
-            case "Result" => sender() ! acc.toList
+            case Result => sender() ! acc.toList
           }
         }).withDispatcher(dispatcherKey))
 

akka-actor-tests/src/test/scala/akka/event/LoggingReceiveSpec.scala

@@ -11,7 +11,7 @@ import scala.concurrent.duration._
 import akka.testkit._
 import org.scalatest.WordSpec
 import com.typesafe.config.ConfigFactory
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import akka.actor._
 import scala.annotation.tailrec
 

akka-actor-tests/src/test/scala/akka/io/TcpIntegrationSpecSupport.scala

@@ -40,11 +40,17 @@ trait TcpIntegrationSpecSupport { _: AkkaSpec =>
     def establishNewClientConnection(): (TestProbe, ActorRef, TestProbe, ActorRef) = {
       val connectCommander = TestProbe()(clientSystem)
       connectCommander.send(IO(Tcp)(clientSystem), Connect(endpoint, options = connectOptions))
-      val Connected(`endpoint`, localAddress) = connectCommander.expectMsgType[Connected]
+      val localAddress = connectCommander.expectMsgType[Connected] match {
+        case Connected(`endpoint`, localAddress) => localAddress
+        case Connected(other, _)                 => fail(s"No match: $other")
+      }
       val clientHandler = TestProbe()(clientSystem)
       connectCommander.sender() ! Register(clientHandler.ref)
 
-      val Connected(`localAddress`, `endpoint`) = bindHandler.expectMsgType[Connected]
+      bindHandler.expectMsgType[Connected] match {
+        case Connected(`localAddress`, `endpoint`) => //ok
+        case other                                 => fail(s"No match: ${other}")
+      }
       val serverHandler = TestProbe()
       bindHandler.sender() ! Register(serverHandler.ref)
 

akka-actor-tests/src/test/scala/akka/io/dns/DockerBindDnsService.scala

@@ -4,7 +4,7 @@
 
 package akka.io.dns
 
-import collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import akka.testkit.AkkaSpec
 import com.spotify.docker.client.DefaultDockerClient
 import com.spotify.docker.client.DockerClient.{ ListContainersParam, LogsParam }

akka-actor-tests/src/test/scala/akka/io/dns/internal/ResolvConfParserSpec.scala

@@ -9,7 +9,7 @@ import org.scalatest.{ Matchers, WordSpec }
 class ResolvConfParserSpec extends WordSpec with Matchers {
 
   private def parse(str: String): ResolvConf = {
-    ResolvConfParser.parseLines(str.lines)
+    ResolvConfParser.parseLines(str.linesIterator)
   }
 
   "The ResolvConfParser" should {

akka-actor-tests/src/test/scala/akka/japi/JavaAPITest.scala

@@ -4,6 +4,8 @@
 
 package akka.japi
 
-import org.scalatestplus.junit.JUnitSuiteLike
+import org.scalatest.junit.JUnitSuiteLike
+import com.github.ghik.silencer.silent
 
+@silent
 class JavaAPITest extends JavaAPITestBase with JUnitSuiteLike

akka-actor-tests/src/test/scala/akka/pattern/BackoffOnRestartSupervisorSpec.scala

@@ -167,7 +167,7 @@ class BackoffOnRestartSupervisorSpec extends AkkaSpec with ImplicitSender {
 
       supervisor ! BackoffSupervisor.GetCurrentChild
       // new instance
-      val Some(child) = expectMsgType[BackoffSupervisor.CurrentChild].ref
+      val child = expectMsgType[BackoffSupervisor.CurrentChild].ref.get
 
       child ! "PING"
       expectMsg("PONG")

akka-actor-tests/src/test/scala/akka/util/BoundedBlockingQueueSpec.scala

@@ -17,7 +17,7 @@ import org.scalatest.time.Span
 import org.scalatest.time.SpanSugar._
 import org.scalatest.{ Matchers, WordSpec }
 
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.collection.mutable
 import scala.concurrent.{ Await, ExecutionContext, ExecutionContextExecutor, Future }
 import scala.util.control.Exception

akka-actor-tests/src/test/scala/akka/util/ByteStringSpec.scala

@@ -742,7 +742,7 @@ class ByteStringSpec extends WordSpec with Matchers with Checkers {
           a.asByteBuffers.forall(_.isReadOnly)
         }
         check { (a: ByteString) =>
-          import scala.collection.JavaConverters.iterableAsScalaIterableConverter
+          import akka.util.ccompat.JavaConverters._
           a.asByteBuffers.zip(a.getByteBuffers().asScala).forall(x => x._1 == x._2)
         }
       }

akka-actor-tests/src/test/scala/akka/util/JavaDurationSpec.scala

@@ -4,6 +4,8 @@
 
 package akka.util
 
-import org.scalatestplus.junit.JUnitSuiteLike
+import org.scalatest.junit.JUnitSuiteLike
+import com.github.ghik.silencer.silent
 
+@silent
 class JavaDurationSpec extends JavaDuration with JUnitSuiteLike

akka-actor-typed-tests/src/test/scala/akka/actor/typed/eventstream/EventStreamSpec.scala

@@ -5,6 +5,7 @@
 package akka.actor.typed.eventstream
 
 import scala.concurrent.duration._
+import scala.language.postfixOps
 
 import akka.actor.testkit.typed.scaladsl.{ ScalaTestWithActorTestKit, TestProbe }
 import org.scalatest.WordSpecLike
@@ -13,7 +14,7 @@ class EventStreamSpec extends ScalaTestWithActorTestKit with WordSpecLike {
 
   import EventStreamSpec._
 
-  private final val ShortWait = 100 milli
+  private final val ShortWait = 100.millis
 
   "system event stream".can {
     val eventObjListener: TestProbe[EventObj.type] = testKit.createTestProbe()

akka-actor-typed/src/main/scala/akka/actor/typed/internal/ExtensionsImpl.scala

@@ -10,7 +10,7 @@ import akka.annotation.InternalApi
 import akka.actor.typed.{ ActorSystem, Extension, ExtensionId, Extensions }
 import scala.annotation.tailrec
 import scala.util.{ Failure, Success, Try }
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 
 import akka.actor.typed.ExtensionSetup
 

akka-actor-typed/src/main/scala/akka/actor/typed/internal/adapter/LoggerAdapterImpl.scala

@@ -10,7 +10,7 @@ import akka.event.Logging._
 import akka.event.{ LoggingBus, LoggingFilterWithMarker, LogMarker => UntypedLM }
 import akka.util.OptionVal
 
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 
 /**
  * INTERNAL API

akka-actor-typed/src/main/scala/akka/actor/typed/internal/receptionist/ReceptionistMessages.scala

@@ -9,7 +9,7 @@ import akka.actor.typed.receptionist.Receptionist.Command
 import akka.actor.typed.receptionist.{ Receptionist, ServiceKey }
 import akka.annotation.InternalApi
 
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 
 /**
  * Internal API

akka-actor-typed/src/main/scala/akka/actor/typed/javadsl/Behaviors.scala

@@ -14,7 +14,7 @@ import akka.japi.function.{ Effect, Function2 => JapiFunction2 }
 import akka.japi.pf.PFBuilder
 import akka.util.unused
 
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.reflect.ClassTag
 
 /**

akka-actor-typed/src/main/scala/akka/actor/typed/receptionist/Receptionist.scala

@@ -8,7 +8,7 @@ import akka.actor.typed.{ ActorRef, ActorSystem, Dispatchers, Extension, Extensi
 import akka.actor.typed.internal.receptionist._
 import akka.annotation.DoNotInherit
 
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.reflect.ClassTag
 import akka.annotation.InternalApi
 

akka-actor/src/main/mima-filters/2.5.23.backwards.excludes

@@ -0,0 +1,9 @@
+# These were added for bincompat with 2.4 but no longer part of the public API,
+# so can be safely excluded now. Required to avoid naming clashes with extension
+# methods generated on Scala 2.13 (https://github.com/scala/scala/commit/f9879b63a87b1e3062c58abd9ce30e68d9fee8ca)
+# These should go into the .backwards.excludes for the last 2.5 version in
+# which Scala 2.13 support is merged
+ProblemFilters.exclude[DirectMissingMethodProblem]("akka.pattern.AskableActorRef.ask$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("akka.pattern.AskableActorRef.?$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("akka.pattern.AskableActorSelection.ask$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("akka.pattern.AskableActorSelection.?$extension")

akka-actor/src/main/scala-2.13+/akka/util/ByteString.scala

@@ -7,13 +7,15 @@ package akka.util
 import java.io.{ ObjectInputStream, ObjectOutputStream }
 import java.nio.{ ByteBuffer, ByteOrder }
 import java.lang.{ Iterable => JIterable }
+import java.nio.charset.{ Charset, StandardCharsets }
 
 import scala.annotation.{ tailrec, varargs }
 import scala.collection.mutable.{ Builder, WrappedArray }
 import scala.collection.{ immutable, mutable }
 import scala.collection.immutable.{ IndexedSeq, IndexedSeqOps, StrictOptimizedSeqOps, VectorBuilder }
 import scala.reflect.ClassTag
-import java.nio.charset.{ Charset, StandardCharsets }
+
+import com.github.ghik.silencer.silent
 
 object ByteString {
 
@@ -384,7 +386,7 @@ object ByteString {
       }
     }
 
-    override protected def writeReplace(): AnyRef = new SerializationProxy(this)
+    protected def writeReplace(): AnyRef = new SerializationProxy(this)
   }
 
   private[akka] object ByteStrings extends Companion {
@@ -626,7 +628,7 @@ object ByteString {
       }
     }
 
-    override protected def writeReplace(): AnyRef = new SerializationProxy(this)
+    protected def writeReplace(): AnyRef = new SerializationProxy(this)
   }
 
   @SerialVersionUID(1L)
@@ -675,10 +677,7 @@ sealed abstract class ByteString
 
   override protected def fromSpecific(coll: IterableOnce[Byte]): ByteString = ByteString(coll)
   override protected def newSpecificBuilder: mutable.Builder[Byte, ByteString] = ByteString.newBuilder
-
+  override val empty: ByteString = ByteString.empty
-  // FIXME this is a workaround for
-  //  https://github.com/scala/bug/issues/11192#issuecomment-436926231
-  protected[this] override def writeReplace(): AnyRef = this
 
   def apply(idx: Int): Byte
   private[akka] def byteStringCompanion: ByteString.Companion
@@ -814,6 +813,7 @@ sealed abstract class ByteString
    * Java API: Returns an Iterable of read-only ByteBuffers that directly wraps this ByteStrings
    * all fragments. Will always have at least one entry.
    */
+  @silent
   def getByteBuffers(): JIterable[ByteBuffer] = {
     import scala.collection.JavaConverters.asJavaIterableConverter
     asByteBuffers.asJava

akka-actor/src/main/scala-2.13+/akka/util/ccompat/package.scala

@@ -14,4 +14,10 @@ package akka.util
 package object ccompat {
   private[akka] type Factory[-A, +C] = scala.collection.Factory[A, C]
   private[akka] val Factory = scala.collection.Factory
+
+  // When we drop support for 2.12 we can delete this concept
+  // and import scala.jdk.CollectionConverters.Ops._ instead
+  object JavaConverters
+      extends scala.collection.convert.AsJavaExtensions
+      with scala.collection.convert.AsScalaExtensions
 }

akka-actor/src/main/scala-2.13-/akka/util/ccompat/package.scala

@@ -82,4 +82,6 @@ package object ccompat {
   implicit class ImmutableSortedSetOps[A](val real: i.SortedSet[A]) extends AnyVal {
     def unsorted: i.Set[A] = real
   }
+
+  object JavaConverters extends scala.collection.convert.DecorateAsJava with scala.collection.convert.DecorateAsScala
 }

akka-actor/src/main/scala/akka/actor/CoordinatedShutdown.scala

@@ -294,7 +294,7 @@ object CoordinatedShutdown extends ExtensionId[CoordinatedShutdown] with Extensi
    * INTERNAL API
    */
   private[akka] def phasesFromConfig(conf: Config): Map[String, Phase] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     val defaultPhaseTimeout = conf.getString("default-phase-timeout")
     val phasesConf = conf.getConfig("phases")
     val defaultPhaseConfig = ConfigFactory.parseString(s"""
@@ -588,7 +588,7 @@ final class CoordinatedShutdown private[akka] (
    * Sum of timeouts of all phases that have some task.
    */
   def totalTimeout(): FiniteDuration = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     tasks.keySet.asScala.foldLeft(Duration.Zero) {
       case (acc, phase) => acc + timeout(phase)
     }

akka-actor/src/main/scala/akka/actor/Deployer.scala

@@ -135,7 +135,7 @@ case object NoScopeGiven extends NoScopeGiven {
  */
 private[akka] class Deployer(val settings: ActorSystem.Settings, val dynamicAccess: DynamicAccess) {
 
-  import scala.collection.JavaConverters._
+  import akka.util.ccompat.JavaConverters._
 
   private val resizerEnabled: Config = ConfigFactory.parseString("resizer.enabled=on")
   private val deployments = new AtomicReference(WildcardIndex[Deploy]())

akka-actor/src/main/scala/akka/actor/Stash.scala

@@ -75,6 +75,7 @@ trait UnrestrictedStash extends Actor with StashSupport {
    *  Overridden callback. Prepends all messages in the stash to the mailbox,
    *  clears the stash, stops all children and invokes the postStop() callback.
    */
+  @throws(classOf[Exception])
   override def preRestart(reason: Throwable, message: Option[Any]): Unit = {
     try unstashAll()
     finally super.preRestart(reason, message)
@@ -85,6 +86,7 @@ trait UnrestrictedStash extends Actor with StashSupport {
    *  Must be called when overriding this method, otherwise stashed messages won't be propagated to DeadLetters
    *  when actor stops.
    */
+  @throws(classOf[Exception])
   override def postStop(): Unit =
     try unstashAll()
     finally super.postStop()

akka-actor/src/main/scala/akka/actor/dungeon/Children.scala

@@ -30,6 +30,7 @@ private[akka] trait Children { this: ActorCell =>
     Unsafe.instance.getObjectVolatile(this, AbstractActorCell.childrenOffset).asInstanceOf[ChildrenContainer]
 
   final def children: immutable.Iterable[ActorRef] = childrenRefs.children
+  @silent
   final def getChildren(): java.lang.Iterable[ActorRef] =
     scala.collection.JavaConverters.asJavaIterableConverter(children).asJava
 

akka-actor/src/main/scala/akka/dispatch/Dispatchers.scala

@@ -194,7 +194,7 @@ class Dispatchers @InternalApi private[akka] (
    * INTERNAL API
    */
   private[akka] def config(id: String, appConfig: Config): Config = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     def simpleName = id.substring(id.lastIndexOf('.') + 1)
     idConfig(id)
       .withFallback(appConfig)
@@ -203,7 +203,7 @@ class Dispatchers @InternalApi private[akka] (
   }
 
   private def idConfig(id: String): Config = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     ConfigFactory.parseMap(Map("id" -> id).asJava)
   }
 

akka-actor/src/main/scala/akka/dispatch/Future.scala

@@ -93,7 +93,7 @@ object ExecutionContexts {
  * Futures is the Java API for Futures and Promises
  */
 object Futures {
-  import scala.collection.JavaConverters.iterableAsScalaIterableConverter
+  import akka.util.ccompat.JavaConverters._
 
   /**
    * Starts an asynchronous computation and returns a `Future` object with the result of that computation.

akka-actor/src/main/scala/akka/dispatch/Mailboxes.scala

@@ -55,7 +55,7 @@ private[akka] class Mailboxes(
   private val mailboxTypeConfigurators = new ConcurrentHashMap[String, MailboxType]
 
   private val mailboxBindings: Map[Class[_ <: Any], String] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     settings.config
       .getConfig("akka.actor.mailbox.requirements")
       .root
@@ -255,7 +255,7 @@ private[akka] class Mailboxes(
 
   //INTERNAL API
   private def config(id: String): Config = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     ConfigFactory
       .parseMap(Map("id" -> id).asJava)
       .withFallback(settings.config.getConfig(id))

akka-actor/src/main/scala/akka/event/Logging.scala

@@ -745,7 +745,7 @@ object Logging {
      * Java API: Retrieve the contents of the MDC.
      */
     def getMDC: java.util.Map[String, Any] = {
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
       mdc.asJava
     }
   }
@@ -1564,7 +1564,7 @@ trait DiagnosticLoggingAdapter extends LoggingAdapter {
 
   import Logging._
 
-  import scala.collection.JavaConverters._
+  import akka.util.ccompat.JavaConverters._
 
   private var _mdc = emptyMDC
 

akka-actor/src/main/scala/akka/io/Tcp.scala

@@ -12,7 +12,7 @@ import com.typesafe.config.Config
 
 import scala.concurrent.duration._
 import scala.collection.immutable
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import akka.util.{ ByteString, Helpers }
 import akka.util.Helpers.Requiring
 import akka.util.JavaDurationConverters._

akka-actor/src/main/scala/akka/io/TcpConnection.scala

@@ -387,7 +387,7 @@ private[io] abstract class TcpConnection(val tcp: TcpExt, val channel: SocketCha
 
     val interestedInClose: Set[ActorRef] =
       (if (writePending) Set(pendingWrite.commander) else Set.empty) ++
-      closedMessage.toSet[CloseInformation].flatMap(_.notificationsTo)
+      closedMessage.toList.flatMap(_.notificationsTo).toSet
 
     if (channel.isOpen) // if channel is still open here, we didn't go through stopWith => unexpected actor termination
       prepareAbort()

akka-actor/src/main/scala/akka/io/Udp.scala

@@ -245,7 +245,7 @@ class UdpExt(system: ExtendedActorSystem) extends IO.Extension {
 object UdpMessage {
   import Udp._
   import java.lang.{ Iterable => JIterable }
-  import scala.collection.JavaConverters._
+  import akka.util.ccompat.JavaConverters._
 
   /**
    * Each [[Udp.Send]] can optionally request a positive acknowledgment to be sent

akka-actor/src/main/scala/akka/io/UdpConnected.scala

@@ -256,7 +256,7 @@ object UdpConnectedMessage {
   def resumeReading: Command = ResumeReading
 
   implicit private def fromJava[T](coll: JIterable[T]): immutable.Iterable[T] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     coll.asScala.to(immutable.Iterable)
   }
 }

akka-actor/src/main/scala/akka/io/dns/DnsProtocol.scala

@@ -9,7 +9,7 @@ import java.util
 import akka.actor.NoSerializationVerificationNeeded
 
 import scala.collection.{ immutable => im }
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 
 /**
  * Supersedes [[akka.io.Dns]] protocol.

akka-actor/src/main/scala/akka/io/dns/DnsSettings.scala

@@ -15,7 +15,7 @@ import akka.util.Helpers
 import akka.util.JavaDurationConverters._
 import com.typesafe.config.{ Config, ConfigValueType }
 
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.collection.immutable
 import scala.concurrent.duration.FiniteDuration
 import scala.util.{ Failure, Success, Try }

akka-actor/src/main/scala/akka/io/dns/internal/ResolvConfParser.scala

@@ -7,7 +7,7 @@ package akka.io.dns.internal
 import java.io.File
 import java.nio.file.Files
 
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.util.Try
 
 private[dns] case class ResolvConf(search: List[String], ndots: Int)

akka-actor/src/main/scala/akka/pattern/AskSupport.scala

@@ -261,18 +261,6 @@ trait ExplicitAskSupport {
 
 object AskableActorRef {
 
-  /**
-   * INTERNAL API: for binary compatibility
-   */
-  private[pattern] def ask$extension(actorRef: ActorRef, message: Any, timeout: Timeout): Future[Any] =
-    actorRef.internalAsk(message, timeout, ActorRef.noSender)
-
-  /**
-   * INTERNAL API: for binary compatibility
-   */
-  private[pattern] def $qmark$extension(actorRef: ActorRef, message: Any, timeout: Timeout): Future[Any] =
-    actorRef.internalAsk(message, timeout, ActorRef.noSender)
-
   private def messagePartOfException(message: Any, sender: ActorRef): String = {
     val msg = if (message == null) "unknown" else message
     val wasSentBy = if (sender == ActorRef.noSender) "" else s" was sent by [$sender]"
@@ -402,21 +390,6 @@ final class ExplicitlyAskableActorRef(val actorRef: ActorRef) extends AnyVal {
     }
 }
 
-object AskableActorSelection {
-
-  /**
-   * INTERNAL API: for binary compatibility
-   */
-  private[pattern] def ask$extension(actorSel: ActorSelection, message: Any, timeout: Timeout): Future[Any] =
-    actorSel.internalAsk(message, timeout, ActorRef.noSender)
-
-  /**
-   * INTERNAL API: for binary compatibility
-   */
-  private[pattern] def $qmark$extension(actorSel: ActorSelection, message: Any, timeout: Timeout): Future[Any] =
-    actorSel.internalAsk(message, timeout, ActorRef.noSender)
-}
-
 /*
  * Implementation class of the “ask” pattern enrichment of ActorSelection
  */

akka-actor/src/main/scala/akka/routing/ConsistentHash.scala

@@ -126,7 +126,7 @@ object ConsistentHash {
    * Java API: Factory method to create a ConsistentHash
    */
   def create[T](nodes: java.lang.Iterable[T], virtualNodesFactor: Int): ConsistentHash[T] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     apply(nodes.asScala, virtualNodesFactor)(ClassTag(classOf[Any].asInstanceOf[Class[T]]))
   }
 

akka-actor/src/main/scala/akka/routing/Router.scala

@@ -78,7 +78,7 @@ final case class SeveralRoutees(routees: immutable.IndexedSeq[Routee]) extends R
    * Java API
    */
   def getRoutees(): java.util.List[Routee] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     routees.asJava
   }
 

akka-actor/src/main/scala/akka/routing/RouterConfig.scala

@@ -405,7 +405,7 @@ final case class Routees(routees: immutable.IndexedSeq[Routee]) {
    * Java API
    */
   def getRoutees: java.util.List[Routee] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     routees.asJava
   }
 }

akka-actor/src/main/scala/akka/serialization/Serialization.scala

@@ -63,7 +63,7 @@ object Serialization {
     }
 
     private final def configToMap(cfg: Config): Map[String, String] = {
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
       cfg.root.unwrapped.asScala.toMap.map { case (k, v) => (k -> v.toString) }
     }
   }

akka-actor/src/main/scala/akka/serialization/SerializationSetup.scala

@@ -8,7 +8,7 @@ import akka.actor.ExtendedActorSystem
 import akka.actor.setup.Setup
 
 import scala.collection.immutable
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 
 object SerializationSetup {
 

akka-actor/src/main/scala/akka/util/Index.scala

@@ -8,7 +8,11 @@ import annotation.tailrec
 
 import java.util.concurrent.{ ConcurrentHashMap, ConcurrentSkipListSet }
 import java.util.Comparator
-import scala.collection.JavaConverters.{ asScalaIteratorConverter, collectionAsScalaIterableConverter }
+
+import scala.collection.JavaConverters.collectionAsScalaIterableConverter
+import akka.util.ccompat.JavaConverters._
+
+import com.github.ghik.silencer.silent
 
 /**
  * An implementation of a ConcurrentMultiMap
@@ -143,6 +147,7 @@ class Index[K, V](val mapSize: Int, val valueComparator: Comparator[V]) {
     if (set ne null) {
       set.synchronized {
         container.remove(key, set)
+        @silent
         val ret = collectionAsScalaIterableConverter(set.clone()).asScala // Make copy since we need to clear the original
         set.clear() // Clear the original set to signal to any pending writers that there was a conflict
         Some(ret)

akka-actor/src/main/scala/akka/util/Unused.scala

@@ -4,6 +4,8 @@
 
 package akka.util
 
+import com.github.ghik.silencer.silent
+
 import akka.annotation.InternalApi
 
 /**
@@ -12,6 +14,15 @@ import akka.annotation.InternalApi
  * or other reason. Useful in combination with
  * `-Ywarn-unused:explicits,implicits` compiler options.
  *
+ * Extends 'deprecated' to make sure using a parameter marked @unused
+ * produces a warning, and not using a parameter marked @unused does not
+ * produce an 'unused parameter' warning.
+ *
+ * This approach is deprecated in Scala 2.13 and scheduled to be
+ * removed in 2.14. Perhaps we should promote introducing an `@unused`
+ * to Scala? https://contributors.scala-lang.org/t/more-error-reporting-annotations/1681/7
+ *
  * INTERNAL API
  */
+@silent
 @InternalApi private[akka] class unused extends deprecated("unused", "")

akka-bench-jmh-typed/src/main/scala/akka/BenchRunner.scala

@@ -10,7 +10,7 @@ import org.openjdk.jmh.runner.options.CommandLineOptions
 
 object BenchRunner {
   def main(args: Array[String]) = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
 
     val args2 = args.toList.flatMap {
       case "quick"    => "-i 1 -wi 1 -f1 -t1".split(" ").toList

akka-bench-jmh/src/main/scala/akka/BenchRunner.scala

@@ -10,7 +10,7 @@ import org.openjdk.jmh.runner.options.CommandLineOptions
 
 object BenchRunner {
   def main(args: Array[String]) = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
 
     val args2 = args.toList.flatMap {
       case "quick"    => "-i 1 -wi 1 -f1 -t1".split(" ").toList

akka-cluster-metrics/src/main/scala/akka/cluster/metrics/ClusterMetricsCollector.scala

@@ -16,6 +16,8 @@ import akka.cluster.MemberStatus
 import java.util.concurrent.ThreadLocalRandom
 import akka.actor.DeadLetterSuppression
 
+import com.github.ghik.silencer.silent
+
 /**
  *  Runtime collection management commands.
  */
@@ -92,6 +94,7 @@ trait ClusterMetricsEvent
 final case class ClusterMetricsChanged(nodeMetrics: Set[NodeMetrics]) extends ClusterMetricsEvent {
 
   /** Java API */
+  @silent
   def getNodeMetrics: java.lang.Iterable[NodeMetrics] =
     scala.collection.JavaConverters.asJavaIterableConverter(nodeMetrics).asJava
 }

akka-cluster-metrics/src/main/scala/akka/cluster/metrics/Metric.scala

@@ -9,6 +9,8 @@ import scala.util.Success
 import scala.util.Failure
 import scala.util.Try
 
+import com.github.ghik.silencer.silent
+
 /**
  * Metrics key/value.
  *
@@ -323,6 +325,7 @@ final case class NodeMetrics(address: Address, timestamp: Long, metrics: Set[Met
   /**
    * Java API
    */
+  @silent
   def getMetrics: java.lang.Iterable[Metric] =
     scala.collection.JavaConverters.asJavaIterableConverter(metrics).asJava
 

akka-cluster-metrics/src/main/scala/akka/cluster/metrics/protobuf/MessageSerializer.scala

@@ -18,7 +18,7 @@ import akka.util.ccompat._
 
 import scala.annotation.tailrec
 import scala.collection.immutable
-import scala.collection.JavaConverters.{ asJavaIterableConverter, asScalaBufferConverter, setAsJavaSetConverter }
+import akka.util.ccompat.JavaConverters._
 import java.io.NotSerializableException
 
 import akka.dispatch.Dispatchers

akka-cluster-sharding/src/main/scala/akka/cluster/sharding/ClusterSharding.scala

@@ -8,7 +8,7 @@ import java.net.URLEncoder
 import java.util.Optional
 import java.util.concurrent.ConcurrentHashMap
 
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.collection.immutable
 import scala.concurrent.Await
 import scala.util.control.NonFatal

akka-cluster-sharding/src/main/scala/akka/cluster/sharding/ShardCoordinator.scala

@@ -109,14 +109,14 @@ object ShardCoordinator {
         shardId: ShardId,
         currentShardAllocations: Map[ActorRef, immutable.IndexedSeq[ShardId]]): Future[ActorRef] = {
 
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
       allocateShard(requester, shardId, currentShardAllocations.asJava)
     }
 
     override final def rebalance(
         currentShardAllocations: Map[ActorRef, immutable.IndexedSeq[ShardId]],
         rebalanceInProgress: Set[ShardId]): Future[Set[ShardId]] = {
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
       implicit val ec = ExecutionContexts.sameThreadExecutionContext
       rebalance(currentShardAllocations.asJava, rebalanceInProgress.asJava).map(_.asScala.toSet)
     }

akka-cluster-sharding/src/main/scala/akka/cluster/sharding/ShardRegion.scala

@@ -242,7 +242,7 @@ object ShardRegion {
      * Java API
      */
     def getRegions: java.util.Set[Address] = {
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
       regions.asJava
     }
 
@@ -269,7 +269,7 @@ object ShardRegion {
      * Java API
      */
     def getRegions(): java.util.Map[Address, ShardRegionStats] = {
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
       regions.asJava
     }
   }
@@ -297,7 +297,7 @@ object ShardRegion {
      * Java API
      */
     def getStats(): java.util.Map[ShardId, Int] = {
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
       stats.asJava
     }
 
@@ -329,7 +329,7 @@ object ShardRegion {
      * If gathering the shard information times out the set of shards will be empty.
      */
     def getShards(): java.util.Set[ShardState] = {
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
       shards.asJava
     }
   }
@@ -340,7 +340,7 @@ object ShardRegion {
      * Java API:
      */
     def getEntityIds(): java.util.Set[EntityId] = {
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
       entityIds.asJava
     }
   }

akka-cluster-sharding/src/main/scala/akka/cluster/sharding/protobuf/ClusterShardingMessageSerializer.scala

@@ -9,7 +9,7 @@ import java.util.zip.GZIPInputStream
 import java.util.zip.GZIPOutputStream
 
 import scala.annotation.tailrec
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.collection.immutable
 import akka.actor.ActorRef
 import akka.actor.ExtendedActorSystem

akka-cluster-tools/src/main/scala/akka/cluster/client/ClusterClient.scala

@@ -152,7 +152,7 @@ final class ClusterClientSettings(
    * Java API
    */
   def withInitialContacts(initialContacts: java.util.Set[ActorPath]): ClusterClientSettings = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     withInitialContacts(initialContacts.asScala.toSet)
   }
 
@@ -262,7 +262,7 @@ case object GetContactPoints extends GetContactPoints {
  * @param contactPoints The presently known list of contact points.
  */
 final case class ContactPoints(contactPoints: Set[ActorPath]) {
-  import scala.collection.JavaConverters._
+  import akka.util.ccompat.JavaConverters._
 
   /**
    * Java API
@@ -811,7 +811,7 @@ case object GetClusterClients extends GetClusterClients {
  * @param clusterClients The presently known list of cluster clients.
  */
 final case class ClusterClients(clusterClients: Set[ActorRef]) {
-  import scala.collection.JavaConverters._
+  import akka.util.ccompat.JavaConverters._
 
   /**
    * Java API

akka-cluster-tools/src/main/scala/akka/cluster/client/protobuf/ClusterClientMessageSerializer.scala

@@ -4,7 +4,7 @@
 
 package akka.cluster.client.protobuf
 
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import akka.actor.ExtendedActorSystem
 import akka.serialization.BaseSerializer
 import akka.serialization.SerializerWithStringManifest

akka-cluster-tools/src/main/scala/akka/cluster/pubsub/DistributedPubSubMediator.scala

@@ -236,7 +236,7 @@ object DistributedPubSubMediator {
      * Java API
      */
     def getTopics(): java.util.Set[String] = {
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
       topics.asJava
     }
   }
@@ -590,14 +590,12 @@ class DistributedPubSubMediator(settings: DistributedPubSubSettings)
     case Send(path, msg, localAffinity) =>
       val routees = registry(selfAddress).content.get(path) match {
         case Some(valueHolder) if localAffinity =>
-          (for {
+          valueHolder.routee.toList.toIndexedSeq
-            routee <- valueHolder.routee
-          } yield routee).toVector
         case _ =>
           (for {
             (_, bucket) <- registry
-            valueHolder <- bucket.content.get(path).toSeq
+            valueHolder <- bucket.content.get(path).toList
-            routee <- valueHolder.routee.toSeq
+            routee <- valueHolder.routee.toList
           } yield routee).toVector
       }
 
@@ -780,8 +778,8 @@ class DistributedPubSubMediator(settings: DistributedPubSubSettings)
     val refs = for {
       (address, bucket) <- registry
       if !(allButSelf && address == selfAddress) // if we should skip sender() node and current address == self address => skip
-      valueHolder <- bucket.content.get(path).toSeq
+      valueHolder <- bucket.content.get(path).toList
-      ref <- valueHolder.ref.toSeq
+      ref <- valueHolder.ref.toList
     } yield ref
     if (refs.isEmpty) ignoreOrSendToDeadLetters(msg)
     else refs.foreach(_.forward(msg))

akka-cluster-tools/src/main/scala/akka/cluster/pubsub/protobuf/DistributedPubSubMessageSerializer.scala

@@ -12,7 +12,7 @@ import java.util.zip.GZIPOutputStream
 import java.util.zip.GZIPInputStream
 import scala.annotation.tailrec
 import akka.cluster.pubsub.protobuf.msg.{ DistributedPubSubMessages => dm }
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import akka.cluster.pubsub.DistributedPubSubMediator._
 import akka.cluster.pubsub.DistributedPubSubMediator.Internal._
 import akka.actor.ActorRef

akka-cluster-tools/src/test/scala/akka/cluster/TestLease.scala

@@ -15,7 +15,7 @@ import akka.testkit.TestProbe
 import com.typesafe.config.ConfigFactory
 
 import scala.concurrent.{ Future, Promise }
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 
 object TestLeaseExt extends ExtensionId[TestLeaseExt] with ExtensionIdProvider {
   override def get(system: ActorSystem): TestLeaseExt = super.get(system)

akka-cluster/src/main/scala/akka/cluster/Cluster.scala

@@ -26,6 +26,8 @@ import scala.util.control.NonFatal
 
 import akka.event.Logging.LogLevel
 
+import com.github.ghik.silencer.silent
+
 /**
  * Cluster Extension Id and factory for creating Cluster extension.
  */
@@ -94,6 +96,7 @@ class Cluster(val system: ExtendedActorSystem) extends Extension {
   /**
    * Java API: roles that this member has
    */
+  @silent
   def getSelfRoles: java.util.Set[String] =
     scala.collection.JavaConverters.setAsJavaSetConverter(selfRoles).asJava
 

akka-cluster/src/main/scala/akka/cluster/ClusterEvent.scala

@@ -19,6 +19,8 @@ import akka.util.ccompat._
 
 import scala.runtime.AbstractFunction5
 
+import com.github.ghik.silencer.silent
+
 /**
  * Domain events published to the event bus.
  * Subscribe with:
@@ -120,25 +122,28 @@ object ClusterEvent {
      * Java API: get current member list.
      */
     def getMembers: java.lang.Iterable[Member] = {
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
       members.asJava
     }
 
     /**
      * Java API: get current unreachable set.
      */
+    @silent
     def getUnreachable: java.util.Set[Member] =
       scala.collection.JavaConverters.setAsJavaSetConverter(unreachable).asJava
 
     /**
      * Java API: All data centers in the cluster
      */
+    @silent
     def getUnreachableDataCenters: java.util.Set[String] =
       scala.collection.JavaConverters.setAsJavaSetConverter(unreachableDataCenters).asJava
 
     /**
      * Java API: get current “seen-by” set.
      */
+    @silent
     def getSeenBy: java.util.Set[Address] =
       scala.collection.JavaConverters.setAsJavaSetConverter(seenBy).asJava
 
@@ -166,6 +171,7 @@ object ClusterEvent {
     /**
      * Java API: All node roles in the cluster
      */
+    @silent
     def getAllRoles: java.util.Set[String] =
       scala.collection.JavaConverters.setAsJavaSetConverter(allRoles).asJava
 
@@ -177,6 +183,7 @@ object ClusterEvent {
     /**
      * Java API: All data centers in the cluster
      */
+    @silent
     def getAllDataCenters: java.util.Set[String] =
       scala.collection.JavaConverters.setAsJavaSetConverter(allDataCenters).asJava
 

akka-cluster/src/main/scala/akka/cluster/ClusterSettings.scala

@@ -166,7 +166,7 @@ final class ClusterSettings(val config: Config, val systemName: String) {
     cc.getInt("min-nr-of-members")
   }.requiring(_ > 0, "min-nr-of-members must be > 0")
   val MinNrOfMembersOfRole: Map[String, Int] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     cc.getConfig("role")
       .root
       .asScala
@@ -186,7 +186,7 @@ final class ClusterSettings(val config: Config, val systemName: String) {
 
   val ByPassConfigCompatCheck: Boolean = !cc.getBoolean("configuration-compatibility-check.enforce-on-join")
   val ConfigCompatCheckers: Set[String] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     cc.getConfig("configuration-compatibility-check.checkers")
       .root
       .unwrapped
@@ -200,7 +200,7 @@ final class ClusterSettings(val config: Config, val systemName: String) {
   }
 
   val SensitiveConfigPaths = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
 
     val sensitiveKeys =
       cc.getConfig("configuration-compatibility-check.sensitive-config-paths")

akka-cluster/src/main/scala/akka/cluster/JoinConfigCompatChecker.scala

@@ -11,7 +11,7 @@ import akka.annotation.{ DoNotInherit, InternalApi }
 import akka.util.ccompat._
 import com.typesafe.config.{ Config, ConfigFactory, ConfigValue }
 
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.collection.{ immutable => im }
 
 abstract class JoinConfigCompatChecker {

akka-cluster/src/main/scala/akka/cluster/Member.scala

@@ -49,6 +49,7 @@ class Member private[cluster] (
   /**
    * Java API
    */
+  @silent
   def getRoles: java.util.Set[String] =
     scala.collection.JavaConverters.setAsJavaSetConverter(roles).asJava
 

akka-cluster/src/main/scala/akka/cluster/protobuf/ClusterMessageSerializer.scala

@@ -15,14 +15,13 @@ import akka.protobuf.{ ByteString, MessageLite }
 
 import scala.annotation.tailrec
 import scala.collection.immutable
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.concurrent.duration.Deadline
 import akka.annotation.InternalApi
 import akka.cluster.InternalClusterAction._
 import akka.cluster.routing.{ ClusterRouterPool, ClusterRouterPoolSettings }
 import akka.routing.Pool
 import akka.util.ccompat._
-import akka.util.ccompat._
 import com.github.ghik.silencer.silent
 import com.typesafe.config.{ Config, ConfigFactory, ConfigRenderOptions }
 
@@ -184,6 +183,7 @@ final class ClusterMessageSerializer(val system: ExtendedActorSystem)
     builder.build()
   }
 
+  @silent
   private def clusterRouterPoolSettingsToProto(settings: ClusterRouterPoolSettings): cm.ClusterRouterPoolSettings = {
     val builder = cm.ClusterRouterPoolSettings.newBuilder()
     builder
@@ -193,8 +193,7 @@ final class ClusterMessageSerializer(val system: ExtendedActorSystem)
       .addAllUseRoles(settings.useRoles.asJava)
 
     // for backwards compatibility
-    @silent
+    settings.useRole.foreach(builder.setUseRole)
-    val _ = settings.useRole.foreach(builder.setUseRole)
 
     builder.build()
   }

akka-cluster/src/main/scala/akka/cluster/routing/ClusterRouterConfig.scala

@@ -30,7 +30,7 @@ import com.typesafe.config.ConfigFactory
 
 import scala.annotation.{ tailrec, varargs }
 import scala.collection.immutable
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 
 object ClusterRouterGroupSettings {
   @deprecated("useRole has been replaced with useRoles", since = "2.5.4")

akka-cluster/src/multi-jvm/scala/akka/cluster/StressSpec.scala

@@ -770,7 +770,7 @@ abstract class StressSpec
       .append(" MB")
     sb.append("\n")
 
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     val args = runtime.getInputArguments.asScala.filterNot(_.contains("classpath")).mkString("\n  ")
     sb.append("Args:\n  ").append(args)
     sb.append("\n")

akka-cluster/src/test/scala/akka/cluster/ClusterConfigSpec.scala

@@ -12,8 +12,10 @@ import akka.dispatch.Dispatchers
 import akka.remote.PhiAccrualFailureDetector
 import akka.util.Helpers.ConfigOps
 import akka.actor.Address
+
 import com.github.ghik.silencer.silent
 
+@silent
 class ClusterConfigSpec extends AkkaSpec {
 
   "Clustering" must {
@@ -41,8 +43,7 @@ class ClusterConfigSpec extends AkkaSpec {
       UnreachableNodesReaperInterval should ===(1 second)
       PublishStatsInterval should ===(Duration.Undefined)
       AutoDownUnreachableAfter should ===(Duration.Undefined)
-      @silent
+      DownRemovalMargin should ===(Duration.Zero)
-      val _ = DownRemovalMargin should ===(Duration.Zero)
       MinNrOfMembers should ===(1)
       MinNrOfMembersOfRole should ===(Map.empty[String, Int])
       SelfDataCenter should ===("default")

akka-cluster/src/test/scala/akka/cluster/JoinConfigCompatPreDefinedChecksSpec.scala

@@ -37,18 +37,20 @@ class JoinConfigCompatPreDefinedChecksSpec extends WordSpec with Matchers {
 
     "fail when some required keys are NOT provided" in {
 
-      val Invalid(incompatibleKeys) =
+      JoinConfigCompatChecker.exists(
-        JoinConfigCompatChecker.exists(
+        requiredKeys,
-          requiredKeys,
+        config("""
-          config("""
+            |{
-              |{
+            | akka.cluster.min-nr-of-members = 1
-              | akka.cluster.min-nr-of-members = 1
+            |}
-              |}
+          """.stripMargin)) match {
-            """.stripMargin))
+        case Valid =>
-
+          fail()
-      incompatibleKeys should have size 2
+        case Invalid(incompatibleKeys) =>
-      incompatibleKeys should contain("akka.cluster.retry-unsuccessful-join-after is missing")
+          incompatibleKeys should have size 2
-      incompatibleKeys should contain("akka.cluster.allow-weakly-up-members is missing")
+          incompatibleKeys should contain("akka.cluster.retry-unsuccessful-join-after is missing")
+          incompatibleKeys should contain("akka.cluster.allow-weakly-up-members is missing")
+      }
     }
   }
 
@@ -87,56 +89,62 @@ class JoinConfigCompatPreDefinedChecksSpec extends WordSpec with Matchers {
 
     "fail when some required keys are NOT provided" in {
 
-      val Invalid(incompatibleKeys) =
+      JoinConfigCompatChecker.fullMatch(
-        JoinConfigCompatChecker.fullMatch(
+        requiredKeys,
-          requiredKeys,
+        config("""
-          config("""
+            |{
-              |{
+            | akka.cluster.min-nr-of-members = 1
-              | akka.cluster.min-nr-of-members = 1
+            |}
-              |}
+          """.stripMargin),
-            """.stripMargin),
+        clusterConfig) match {
-          clusterConfig)
+        case Valid =>
-
+          fail()
-      incompatibleKeys should have size 2
+        case Invalid(incompatibleKeys) =>
-      incompatibleKeys should contain("akka.cluster.retry-unsuccessful-join-after is missing")
+          incompatibleKeys should have size 2
-      incompatibleKeys should contain("akka.cluster.allow-weakly-up-members is missing")
+          incompatibleKeys should contain("akka.cluster.retry-unsuccessful-join-after is missing")
+          incompatibleKeys should contain("akka.cluster.allow-weakly-up-members is missing")
+      }
     }
 
     "fail when all required keys are passed, but some values don't match cluster config" in {
 
-      val Invalid(incompatibleKeys) =
+      JoinConfigCompatChecker.fullMatch(
-        JoinConfigCompatChecker.fullMatch(
+        requiredKeys,
-          requiredKeys,
+        config("""
-          config("""
+            |{
-              |{
+            | akka.cluster.min-nr-of-members = 1
-              | akka.cluster.min-nr-of-members = 1
+            | akka.cluster.retry-unsuccessful-join-after = 15s
-              | akka.cluster.retry-unsuccessful-join-after = 15s
+            | akka.cluster.allow-weakly-up-members = off
-              | akka.cluster.allow-weakly-up-members = off
+            |}
-              |}
+          """.stripMargin),
-            """.stripMargin),
+        clusterConfig) match {
-          clusterConfig)
+        case Valid =>
-
+          fail()
-      incompatibleKeys should have size 2
+        case Invalid(incompatibleKeys) =>
-      incompatibleKeys should contain("akka.cluster.retry-unsuccessful-join-after is incompatible")
+          incompatibleKeys should have size 2
-      incompatibleKeys should contain("akka.cluster.allow-weakly-up-members is incompatible")
+          incompatibleKeys should contain("akka.cluster.retry-unsuccessful-join-after is incompatible")
+          incompatibleKeys should contain("akka.cluster.allow-weakly-up-members is incompatible")
+      }
     }
 
     "fail when all required keys are passed, but some are missing and others don't match cluster config" in {
 
-      val Invalid(incompatibleKeys) =
+      JoinConfigCompatChecker.fullMatch(
-        JoinConfigCompatChecker.fullMatch(
+        requiredKeys,
-          requiredKeys,
+        config("""
-          config("""
+            |{
-              |{
+            | akka.cluster.min-nr-of-members = 1
-              | akka.cluster.min-nr-of-members = 1
+            | akka.cluster.allow-weakly-up-members = off
-              | akka.cluster.allow-weakly-up-members = off
+            |}
-              |}
+          """.stripMargin),
-            """.stripMargin),
+        clusterConfig) match {
-          clusterConfig)
+        case Valid =>
-
+          fail()
-      incompatibleKeys should have size 2
+        case Invalid(incompatibleKeys) =>
-      incompatibleKeys should contain("akka.cluster.retry-unsuccessful-join-after is missing")
+          incompatibleKeys should have size 2
-      incompatibleKeys should contain("akka.cluster.allow-weakly-up-members is incompatible")
+          incompatibleKeys should contain("akka.cluster.retry-unsuccessful-join-after is missing")
+          incompatibleKeys should contain("akka.cluster.allow-weakly-up-members is incompatible")
+      }
     }
   }
 

akka-cluster/src/test/scala/akka/cluster/protobuf/ClusterMessageSerializerSpec.scala

@@ -14,7 +14,7 @@ import collection.immutable.SortedSet
 import akka.testkit.{ AkkaSpec, TestKit }
 import com.github.ghik.silencer.silent
 import com.typesafe.config.ConfigFactory
-
+@silent
 class ClusterMessageSerializerSpec extends AkkaSpec("akka.actor.provider = cluster") {
 
   val serializer = new ClusterMessageSerializer(system.asInstanceOf[ExtendedActorSystem])
@@ -148,8 +148,7 @@ class ClusterMessageSerializerSpec extends AkkaSpec("akka.actor.provider = clust
             pool.settings.totalInstances should ===(123)
             pool.settings.maxInstancesPerNode should ===(345)
             pool.settings.allowLocalRoutees should ===(true)
-            @silent
+            pool.settings.useRole should ===(Some("role ABC"))
-            val _ = pool.settings.useRole should ===(Some("role ABC"))
             pool.settings.useRoles should ===(Set("role ABC"))
         }
       } finally {

akka-discovery/src/main/scala/akka/discovery/ServiceDiscovery.scala

@@ -35,7 +35,7 @@ object ServiceDiscovery {
      * Java API
      */
     def getAddresses: java.util.List[ResolvedTarget] = {
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
       addresses.asJava
     }
 
@@ -58,6 +58,8 @@ object ServiceDiscovery {
   object ResolvedTarget {
     // Simply compare the bytes of the address.
     // This may not work in exotic cases such as IPv4 addresses encoded as IPv6 addresses.
+    import com.github.ghik.silencer.silent
+    @silent
     private implicit val inetAddressOrdering: Ordering[InetAddress] =
       Ordering.by[InetAddress, Iterable[Byte]](_.getAddress)
 

akka-discovery/src/main/scala/akka/discovery/aggregate/AggregateServiceDiscovery.scala

@@ -13,7 +13,7 @@ import akka.event.Logging
 import akka.util.Helpers.Requiring
 import com.typesafe.config.Config
 
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.concurrent.Future
 import scala.concurrent.duration.FiniteDuration
 import scala.util.control.NonFatal

akka-discovery/src/main/scala/akka/discovery/config/ConfigServiceDiscovery.scala

@@ -11,7 +11,7 @@ import akka.discovery.ServiceDiscovery.{ Resolved, ResolvedTarget }
 import akka.event.Logging
 import com.typesafe.config.Config
 
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.concurrent.Future
 import scala.concurrent.duration.FiniteDuration
 

akka-distributed-data/src/main/scala/akka/cluster/ddata/DurableStore.scala

@@ -8,7 +8,7 @@ import java.io.File
 import java.nio.ByteBuffer
 import java.util.concurrent.TimeUnit
 
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.concurrent.duration._
 import scala.util.Try
 import scala.util.control.NonFatal
@@ -301,7 +301,7 @@ final class LmdbDurableStore(config: Config) extends Actor with ActorLogging {
             TimeUnit.NANOSECONDS.toMillis(System.nanoTime - t0))
       } catch {
         case NonFatal(e) =>
-          import scala.collection.JavaConverters._
+          import akka.util.ccompat.JavaConverters._
           log.error(e, "failed to store [{}]", pending.keySet.asScala.mkString(","))
           tx.abort()
       } finally {

akka-distributed-data/src/main/scala/akka/cluster/ddata/GSet.scala

@@ -43,7 +43,7 @@ final case class GSet[A] private (elements: Set[A])(override val delta: Option[G
    * Java API
    */
   def getElements(): java.util.Set[A] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     elements.asJava
   }
 

akka-distributed-data/src/main/scala/akka/cluster/ddata/LWWMap.scala

@@ -75,7 +75,7 @@ final class LWWMap[A, B] private[akka] (private[akka] val underlying: ORMap[A, L
    * Java API: All entries of the map.
    */
   def getEntries(): java.util.Map[A, B] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     entries.asJava
   }
 

akka-distributed-data/src/main/scala/akka/cluster/ddata/ORMap.scala

@@ -196,7 +196,7 @@ final class ORMap[A, B <: ReplicatedData] private[akka] (
    * Java API: All entries of the map.
    */
   def getEntries(): java.util.Map[A, B] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     entries.asJava
   }
 

akka-distributed-data/src/main/scala/akka/cluster/ddata/ORMultiMap.scala

@@ -102,7 +102,7 @@ final class ORMultiMap[A, B] private[akka] (
    * Java API: All entries of a multimap where keys are strings and values are sets.
    */
   def getEntries(): java.util.Map[A, java.util.Set[B]] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     val result = new java.util.HashMap[A, java.util.Set[B]]
     if (withValueDeltas)
       underlying.entries.foreach {
@@ -165,14 +165,14 @@ final class ORMultiMap[A, B] private[akka] (
    * replicated data set.
    */
   def put(node: SelfUniqueAddress, key: A, value: java.util.Set[B]): ORMultiMap[A, B] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     put(node.uniqueAddress, key, value.asScala.toSet)
   }
 
   @Deprecated
   @deprecated("Use `put` that takes a `SelfUniqueAddress` parameter instead.", since = "2.5.20")
   def put(node: Cluster, key: A, value: java.util.Set[B]): ORMultiMap[A, B] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     put(node.selfUniqueAddress, key, value.asScala.toSet)
   }
 

akka-distributed-data/src/main/scala/akka/cluster/ddata/ORSet.scala

@@ -309,7 +309,7 @@ final class ORSet[A] private[akka] (
    * Java API
    */
   def getElements(): java.util.Set[A] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     elements.asJava
   }
 

akka-distributed-data/src/main/scala/akka/cluster/ddata/PNCounterMap.scala

@@ -54,7 +54,7 @@ final class PNCounterMap[A] private[akka] (private[akka] val underlying: ORMap[A
 
   /** Java API */
   def getEntries: java.util.Map[A, BigInteger] = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     underlying.entries.map { case (k, c) => k -> c.value.bigInteger }.asJava
   }
 

akka-distributed-data/src/main/scala/akka/cluster/ddata/Replicator.scala

@@ -65,6 +65,8 @@ import akka.event.Logging
 import akka.util.JavaDurationConverters._
 import akka.util.ccompat._
 
+import com.github.ghik.silencer.silent
+
 @ccompatUsedUntil213
 object ReplicatorSettings {
 
@@ -87,7 +89,7 @@ object ReplicatorSettings {
       case _               => config.getDuration("pruning-interval", MILLISECONDS).millis
     }
 
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     new ReplicatorSettings(
       role = roleOption(config.getString("role")),
       gossipInterval = config.getDuration("gossip-interval", MILLISECONDS).millis,
@@ -177,7 +179,7 @@ final class ReplicatorSettings(
       deltaCrdtEnabled: Boolean,
       maxDeltaSize: Int) =
     this(
-      role.toSet,
+      role.iterator.toSet,
       gossipInterval,
       notifySubscribersInterval,
       maxDeltaElements,
@@ -201,7 +203,7 @@ final class ReplicatorSettings(
       pruningInterval: FiniteDuration,
       maxPruningDissemination: FiniteDuration) =
     this(
-      roles = role.toSet,
+      roles = role.iterator.toSet,
       gossipInterval,
       notifySubscribersInterval,
       maxDeltaElements,
@@ -270,9 +272,9 @@ final class ReplicatorSettings(
       deltaCrdtEnabled,
       200)
 
-  def withRole(role: String): ReplicatorSettings = copy(roles = ReplicatorSettings.roleOption(role).toSet)
+  def withRole(role: String): ReplicatorSettings = copy(roles = ReplicatorSettings.roleOption(role).iterator.toSet)
 
-  def withRole(role: Option[String]): ReplicatorSettings = copy(roles = role.toSet)
+  def withRole(role: Option[String]): ReplicatorSettings = copy(roles = role.iterator.toSet)
 
   @varargs
   def withRoles(roles: String*): ReplicatorSettings = copy(roles = roles.toSet)
@@ -325,7 +327,7 @@ final class ReplicatorSettings(
    * Java API
    */
   def withDurableKeys(durableKeys: java.util.Set[String]): ReplicatorSettings = {
-    import scala.collection.JavaConverters._
+    import akka.util.ccompat.JavaConverters._
     withDurableKeys(durableKeys.asScala.toSet)
   }
 
@@ -464,7 +466,7 @@ object Replicator {
      * Java API
      */
     def getKeyIds: java.util.Set[String] = {
-      import scala.collection.JavaConverters._
+      import akka.util.ccompat.JavaConverters._
       keyIds.asJava
     }
   }
@@ -1329,7 +1331,9 @@ final class Replicator(settings: ReplicatorSettings) extends Actor with ActorLog
   // possibility to disable Gossip for testing purpose
   var fullStateGossipEnabled = true
 
+  @silent
   val subscribers = new mutable.HashMap[KeyId, mutable.Set[ActorRef]] with mutable.MultiMap[KeyId, ActorRef]
+  @silent
   val newSubscribers = new mutable.HashMap[KeyId, mutable.Set[ActorRef]] with mutable.MultiMap[KeyId, ActorRef]
   var subscriptionKeys = Map.empty[KeyId, KeyR]
 

akka-distributed-data/src/main/scala/akka/cluster/ddata/protobuf/ReplicatedDataSerializer.scala

@@ -11,7 +11,7 @@ import java.util.Comparator
 import java.util.TreeSet
 
 import scala.annotation.tailrec
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.collection.immutable
 
 import akka.actor.ExtendedActorSystem

akka-distributed-data/src/main/scala/akka/cluster/ddata/protobuf/ReplicatorMessageSerializer.scala

@@ -6,7 +6,7 @@ package akka.cluster.ddata.protobuf
 
 import scala.concurrent.duration._
 import java.util.concurrent.TimeUnit
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import scala.collection.immutable
 import scala.concurrent.duration.Duration
 import akka.actor.ExtendedActorSystem

akka-distributed-data/src/main/scala/akka/cluster/ddata/protobuf/SerializationSupport.scala

@@ -10,7 +10,7 @@ import java.util.zip.GZIPInputStream
 import java.util.zip.GZIPOutputStream
 import scala.annotation.tailrec
 import scala.collection.immutable.TreeMap
-import scala.collection.JavaConverters._
+import akka.util.ccompat.JavaConverters._
 import akka.actor.ActorRef
 import akka.actor.Address
 import akka.actor.ExtendedActorSystem

akka-distributed-data/src/test/scala/akka/cluster/ddata/ORMultiMapSpec.scala

@@ -138,7 +138,7 @@ class ORMultiMapSpec extends WordSpec with Matchers {
 
   "be able to get all bindings for an entry and then reduce them upon putting them back" in {
     val m = ORMultiMap().addBinding(node1, "a", "A1").addBinding(node1, "a", "A2").addBinding(node1, "b", "B1")
-    val Some(a) = m.get("a")
+    val a = m.get("a").get
 
     a should be(Set("A1", "A2"))
 

akka-docs/src/test/java/jdocs/persistence/LambdaPersistencePluginDocTest.java

@@ -169,6 +169,7 @@ public class LambdaPersistencePluginDocTest {
 
   static Object o4 =
       new Object() {
+        // https://github.com/akka/akka/issues/26826
         // #journal-tck-before-after-java
         @RunWith(JUnitRunner.class)
         class MyJournalSpecTest extends JavaJournalSpec {