diff --git a/http-core/src/main/scala/org/apache/pekko/http/impl/engine/client/pool/NewHostConnectionPool.scala b/http-core/src/main/scala/org/apache/pekko/http/impl/engine/client/pool/NewHostConnectionPool.scala
index fc1948bf1d..dd7e1fcdbe 100644
--- a/http-core/src/main/scala/org/apache/pekko/http/impl/engine/client/pool/NewHostConnectionPool.scala
+++ b/http-core/src/main/scala/org/apache/pekko/http/impl/engine/client/pool/NewHostConnectionPool.scala
@@ -637,10 +637,7 @@ private[client] object NewHostConnectionPool {
 
         private val safeCallback = getAsyncCallback[() => Unit](f => f())
         private def safely[T, U](f: T => Unit): T => Unit = t => safeCallback.invoke(() => f(t))
-        private def safeRunnable(body: => Unit): Runnable =
-          new Runnable {
-            def run(): Unit = safeCallback.invoke(() => body)
-          }
+        private def safeRunnable(body: => Unit): Runnable = () => safeCallback.invoke(() => body)
         private def createNewTimeoutId(): Long = {
           lastTimeoutId += 1
           lastTimeoutId
diff --git a/http-core/src/main/scala/org/apache/pekko/http/impl/engine/server/HttpServerBluePrint.scala b/http-core/src/main/scala/org/apache/pekko/http/impl/engine/server/HttpServerBluePrint.scala
index 8faa8d3c10..b29c0eb5f4 100644
--- a/http-core/src/main/scala/org/apache/pekko/http/impl/engine/server/HttpServerBluePrint.scala
+++ b/http-core/src/main/scala/org/apache/pekko/http/impl/engine/server/HttpServerBluePrint.scala
@@ -401,7 +401,7 @@ private[http] object HttpServerBluePrint {
         }
     }
     private def schedule(delay: FiniteDuration, handler: HttpRequest => HttpResponse): Cancellable =
-      materializer.scheduleOnce(delay, new Runnable { def run() = trigger.invoke((self, handler(request))) })
+      materializer.scheduleOnce(delay, () => trigger.invoke((self, handler(request))))
 
     import pekko.http.impl.util.JavaMapping.Implicits._
 
diff --git a/http-core/src/main/scala/org/apache/pekko/http/impl/util/StreamUtils.scala b/http-core/src/main/scala/org/apache/pekko/http/impl/util/StreamUtils.scala
index 0613a0a9be..85479451c6 100644
--- a/http-core/src/main/scala/org/apache/pekko/http/impl/util/StreamUtils.scala
+++ b/http-core/src/main/scala/org/apache/pekko/http/impl/util/StreamUtils.scala
@@ -279,7 +279,7 @@ private[http] object StreamUtils {
      * Schedule a block to be run once after the given duration in the context of this graph stage.
      */
     def scheduleOnce(delay: FiniteDuration)(block: => Unit): Cancellable =
-      materializer.scheduleOnce(delay, new Runnable { def run() = runInContext(block) })
+      materializer.scheduleOnce(delay, () => runInContext(block))
 
     def runInContext(block: => Unit): Unit = getAsyncCallback[AnyRef](_ => block).invoke(null)
   }
diff --git a/http-core/src/main/scala/org/apache/pekko/http/javadsl/settings/ClientConnectionSettings.scala b/http-core/src/main/scala/org/apache/pekko/http/javadsl/settings/ClientConnectionSettings.scala
index 7a7a0157d5..fcb567be86 100644
--- a/http-core/src/main/scala/org/apache/pekko/http/javadsl/settings/ClientConnectionSettings.scala
+++ b/http-core/src/main/scala/org/apache/pekko/http/javadsl/settings/ClientConnectionSettings.scala
@@ -65,9 +65,7 @@ abstract class ClientConnectionSettings private[pekko] () { self: ClientConnecti
   final def getStreamCancellationDelay: JDuration = streamCancellationDelay.toJava
   final def getRequestHeaderSizeHint: Int = requestHeaderSizeHint
   final def getWebsocketSettings: WebSocketSettings = websocketSettings
-  final def getWebsocketRandomFactory: Supplier[Random] = new Supplier[Random] {
-    override def get(): Random = websocketRandomFactory()
-  }
+  final def getWebsocketRandomFactory: Supplier[Random] = () => websocketRandomFactory()
   final def getLocalAddress: Optional[InetSocketAddress] = localAddress.toJava
 
   /** The underlying transport used to connect to hosts. By default [[ClientTransport.TCP]] is used. */
@@ -106,9 +104,7 @@ abstract class ClientConnectionSettings private[pekko] () { self: ClientConnecti
   def withLogUnencryptedNetworkBytes(newValue: Optional[Int]): ClientConnectionSettings =
     self.copy(logUnencryptedNetworkBytes = newValue.toScala)
   def withWebsocketRandomFactory(newValue: java.util.function.Supplier[Random]): ClientConnectionSettings =
-    self.copy(websocketSettings = websocketSettings.withRandomFactoryFactory(new Supplier[Random] {
-      override def get(): Random = newValue.get()
-    }))
+    self.copy(websocketSettings = websocketSettings.withRandomFactoryFactory(() => newValue.get()))
   def withWebsocketSettings(newValue: WebSocketSettings): ClientConnectionSettings =
     self.copy(websocketSettings = newValue.asScala)
   def withSocketOptions(newValue: java.lang.Iterable[SocketOption]): ClientConnectionSettings =
diff --git a/http-core/src/main/scala/org/apache/pekko/http/scaladsl/settings/ClientConnectionSettings.scala b/http-core/src/main/scala/org/apache/pekko/http/scaladsl/settings/ClientConnectionSettings.scala
index 6eaed86eea..69c99aa3b1 100644
--- a/http-core/src/main/scala/org/apache/pekko/http/scaladsl/settings/ClientConnectionSettings.scala
+++ b/http-core/src/main/scala/org/apache/pekko/http/scaladsl/settings/ClientConnectionSettings.scala
@@ -68,9 +68,7 @@ abstract class ClientConnectionSettings private[pekko] ()
   def withWebsocketSettings(newValue: WebSocketSettings): ClientConnectionSettings =
     self.copy(websocketSettings = newValue)
   def withWebsocketRandomFactory(newValue: () => Random): ClientConnectionSettings =
-    withWebsocketSettings(self.websocketSettings.withRandomFactoryFactory(new Supplier[Random] {
-      override def get(): Random = newValue()
-    }))
+    withWebsocketSettings(self.websocketSettings.withRandomFactoryFactory(() => newValue()))
   def withUserAgentHeader(newValue: Option[`User-Agent`]): ClientConnectionSettings =
     self.copy(userAgentHeader = newValue)
   def withLogUnencryptedNetworkBytes(newValue: Option[Int]): ClientConnectionSettings =
diff --git a/http-core/src/main/scala/org/apache/pekko/http/scaladsl/settings/ParserSettings.scala b/http-core/src/main/scala/org/apache/pekko/http/scaladsl/settings/ParserSettings.scala
index 5f89fa48d2..2c0d455e17 100644
--- a/http-core/src/main/scala/org/apache/pekko/http/scaladsl/settings/ParserSettings.scala
+++ b/http-core/src/main/scala/org/apache/pekko/http/scaladsl/settings/ParserSettings.scala
@@ -88,17 +88,13 @@ abstract class ParserSettings private[pekko] () extends pekko.http.javadsl.setti
   override def getIllegalResponseHeaderValueProcessingMode = this.illegalResponseHeaderValueProcessingMode
   override def getConflictingContentTypeHeaderProcessingMode = this.conflictingContentTypeHeaderProcessingMode
 
-  override def getCustomMethods = new Function[String, Optional[pekko.http.javadsl.model.HttpMethod]] {
-    override def apply(t: String) = (self.customMethods(t): Option[pekko.http.javadsl.model.HttpMethod]).toJava
-  }
-  override def getCustomStatusCodes = new Function[Int, Optional[pekko.http.javadsl.model.StatusCode]] {
-    override def apply(t: Int) = (self.customStatusCodes(t): Option[pekko.http.javadsl.model.StatusCode]).toJava
-  }
+  override def getCustomMethods =
+    (t: String) => (self.customMethods(t): Option[pekko.http.javadsl.model.HttpMethod]).toJava
+  override def getCustomStatusCodes =
+    (t: Int) => (self.customStatusCodes(t): Option[pekko.http.javadsl.model.StatusCode]).toJava
   override def getCustomMediaTypes =
-    new pekko.japi.function.Function2[String, String, Optional[pekko.http.javadsl.model.MediaType]] {
-      override def apply(mainType: String, subType: String): Optional[model.MediaType] =
-        (self.customMediaTypes(mainType, subType): Option[pekko.http.javadsl.model.MediaType]).toJava
-    }
+    (mainType: String, subType: String) =>
+      (self.customMediaTypes(mainType, subType): Option[pekko.http.javadsl.model.MediaType]).toJava
   def getModeledHeaderParsing: Boolean = this.modeledHeaderParsing
 
   // override for more specific return type
diff --git a/http-core/src/main/scala/org/apache/pekko/http/scaladsl/settings/WebSocketSettings.scala b/http-core/src/main/scala/org/apache/pekko/http/scaladsl/settings/WebSocketSettings.scala
index e39571051b..b97e258125 100644
--- a/http-core/src/main/scala/org/apache/pekko/http/scaladsl/settings/WebSocketSettings.scala
+++ b/http-core/src/main/scala/org/apache/pekko/http/scaladsl/settings/WebSocketSettings.scala
@@ -25,9 +25,7 @@ import scala.concurrent.duration._
 @DoNotInherit
 abstract class WebSocketSettings extends pekko.http.javadsl.settings.WebSocketSettings { self: WebSocketSettingsImpl =>
   def randomFactory: () => Random
-  override final val getRandomFactory: Supplier[Random] = new Supplier[Random] {
-    override def get(): Random = self.randomFactory()
-  }
+  override final val getRandomFactory: Supplier[Random] = () => self.randomFactory()
   override def periodicKeepAliveMode: String
   override def periodicKeepAliveMaxIdle: Duration
 
@@ -37,9 +35,7 @@ abstract class WebSocketSettings extends pekko.http.javadsl.settings.WebSocketSe
    * so keep in mind to keep it relatively small, in order not to make the frames too bloated.
    */
   def periodicKeepAliveData: () => ByteString
-  final def getPeriodicKeepAliveData: Supplier[ByteString] = new Supplier[ByteString] {
-    override def get(): ByteString = self.periodicKeepAliveData()
-  }
+  final def getPeriodicKeepAliveData: Supplier[ByteString] = () => self.periodicKeepAliveData()
 
   override def withRandomFactoryFactory(newValue: Supplier[Random]): WebSocketSettings =
     copy(randomFactory = () => newValue.get())
diff --git a/http-core/src/test/scala/org/apache/pekko/http/javadsl/HttpExtensionApiSpec.scala b/http-core/src/test/scala/org/apache/pekko/http/javadsl/HttpExtensionApiSpec.scala
index 2ad88f6ee3..fd22cc684b 100644
--- a/http-core/src/test/scala/org/apache/pekko/http/javadsl/HttpExtensionApiSpec.scala
+++ b/http-core/src/test/scala/org/apache/pekko/http/javadsl/HttpExtensionApiSpec.scala
@@ -53,16 +53,10 @@ class HttpExtensionApiSpec extends PekkoSpecWithMaterializer(
 
   val successResponse = HttpResponse.create().withStatus(200)
 
-  val httpSuccessFunction = new Function[HttpRequest, HttpResponse] {
-    @throws(classOf[Exception])
-    override def apply(param: HttpRequest): HttpResponse = successResponse
-  }
+  val httpSuccessFunction: Function[HttpRequest, HttpResponse] = (_: HttpRequest) => successResponse
 
-  val asyncHttpSuccessFunction = new Function[HttpRequest, CompletionStage[HttpResponse]] {
-    @throws(classOf[Exception])
-    override def apply(param: HttpRequest): CompletionStage[HttpResponse] =
-      CompletableFuture.completedFuture(successResponse)
-  }
+  val asyncHttpSuccessFunction: Function[HttpRequest, CompletionStage[HttpResponse]] =
+    (_: HttpRequest) => CompletableFuture.completedFuture(successResponse)
 
   "The Java HTTP extension" should {
 
diff --git a/http-core/src/test/scala/org/apache/pekko/testkit/Coroner.scala b/http-core/src/test/scala/org/apache/pekko/testkit/Coroner.scala
index 9d02293642..55313244dd 100644
--- a/http-core/src/test/scala/org/apache/pekko/testkit/Coroner.scala
+++ b/http-core/src/test/scala/org/apache/pekko/testkit/Coroner.scala
@@ -124,7 +124,7 @@ object Coroner {
         watchedHandle.finished()
       }
     }
-    new Thread(new Runnable { def run = triggerReportIfOverdue(duration) }, "Coroner").start()
+    new Thread(() => triggerReportIfOverdue(duration), "Coroner").start()
     watchedHandle.waitForStart()
     watchedHandle
   }
diff --git a/http-tests/src/test/scala/org/apache/pekko/http/scaladsl/RouteJavaScalaDslConversionSpec.scala b/http-tests/src/test/scala/org/apache/pekko/http/scaladsl/RouteJavaScalaDslConversionSpec.scala
index ebf8fdf5e5..c4ece8782d 100644
--- a/http-tests/src/test/scala/org/apache/pekko/http/scaladsl/RouteJavaScalaDslConversionSpec.scala
+++ b/http-tests/src/test/scala/org/apache/pekko/http/scaladsl/RouteJavaScalaDslConversionSpec.scala
@@ -29,9 +29,7 @@ class RouteJavaScalaDslConversionSpec extends AnyWordSpec {
       import org.apache.pekko
 
       val javaRoute =
-        pekko.http.javadsl.server.Directives.get(new Supplier[pekko.http.javadsl.server.Route] {
-          override def get(): Route = pekko.http.javadsl.server.Directives.complete("ok")
-        })
+        pekko.http.javadsl.server.Directives.get(() => pekko.http.javadsl.server.Directives.complete("ok"))
 
       // Remember that Route in Scala is just a type alias:
       //   type Route = RequestContext => Future[RouteResult]
diff --git a/http/src/main/scala/org/apache/pekko/http/javadsl/common/PartialApplication.scala b/http/src/main/scala/org/apache/pekko/http/javadsl/common/PartialApplication.scala
index 8084b309a4..abc7bcc8de 100644
--- a/http/src/main/scala/org/apache/pekko/http/javadsl/common/PartialApplication.scala
+++ b/http/src/main/scala/org/apache/pekko/http/javadsl/common/PartialApplication.scala
@@ -39,10 +39,6 @@ object PartialApplication {
    * @return the function partially applied
    */
   @ApiMayChange
-  def bindParameter[A, B, R](f: BiFunction[A, B, R], a: A): Function[B, R] = {
-    new Function[B, R] {
-      override def apply(b: B): R = f.apply(a, b)
-    }
-  }
+  def bindParameter[A, B, R](f: BiFunction[A, B, R], a: A): Function[B, R] = (b: B) => f.apply(a, b)
 
 }
diff --git a/http/src/main/scala/org/apache/pekko/http/javadsl/server/Directives.scala b/http/src/main/scala/org/apache/pekko/http/javadsl/server/Directives.scala
index b587a1dfc6..a047b484d4 100644
--- a/http/src/main/scala/org/apache/pekko/http/javadsl/server/Directives.scala
+++ b/http/src/main/scala/org/apache/pekko/http/javadsl/server/Directives.scala
@@ -82,10 +82,7 @@ object Directives extends AllDirectives {
   @ApiMayChange
   def allOf(first: Function[Supplier[Route], Route], second: Function[Supplier[Route], Route], inner: Supplier[Route])
       : Route = {
-    first.apply(new Supplier[Route] {
-      override def get(): Route =
-        second.apply(inner)
-    })
+    first.apply(() => second.apply(inner))
   }
 
   /**
@@ -102,13 +99,7 @@ object Directives extends AllDirectives {
   @ApiMayChange
   def allOf[A, B](first: Function[Function[A, Route], Route], second: Function[Function[B, Route], Route],
       inner: BiFunction[A, B, Route]): Route = {
-    first.apply(new Function[A, Route] {
-      override def apply(a: A): Route =
-        second.apply(new Function[B, Route] {
-          override def apply(b: B): Route =
-            inner.apply(a, b)
-        })
-    })
+    first.apply((a: A) => second.apply((b: B) => inner.apply(a, b)))
   }
 
   /**
@@ -124,12 +115,6 @@ object Directives extends AllDirectives {
   @ApiMayChange
   def allOf[A](first: Function[Supplier[Route], Route], second: Function[Function[A, Route], Route],
       inner: Function[A, Route]): Route = {
-    first.apply(new Supplier[Route] {
-      override def get(): Route =
-        second.apply(new Function[A, Route] {
-          override def apply(a: A): Route =
-            inner.apply(a)
-        })
-    })
+    first.apply(() => second.apply((a: A) => inner.apply(a)))
   }
 }
diff --git a/http/src/main/scala/org/apache/pekko/http/scaladsl/server/Rejection.scala b/http/src/main/scala/org/apache/pekko/http/scaladsl/server/Rejection.scala
index ea19c4c9c7..dbde2f99a8 100644
--- a/http/src/main/scala/org/apache/pekko/http/scaladsl/server/Rejection.scala
+++ b/http/src/main/scala/org/apache/pekko/http/scaladsl/server/Rejection.scala
@@ -310,15 +310,13 @@ final case class ValidationRejection(message: String, cause: Option[Throwable] =
  */
 final case class TransformationRejection(transform: immutable.Seq[Rejection] => immutable.Seq[Rejection])
     extends jserver.TransformationRejection with Rejection {
-  override def getTransform = new Function[Iterable[jserver.Rejection], Iterable[jserver.Rejection]] {
-    override def apply(t: Iterable[jserver.Rejection]): Iterable[jserver.Rejection] = {
-      // explicit collects assignment is because of unidoc failing compilation on .asScala and .asJava here
-      val transformed: Seq[jserver.Rejection] =
-        transform(Util.convertIterable[jserver.Rejection, jserver.Rejection](t).collect { case r: Rejection =>
-          r
-        }).collect { case j: jserver.Rejection => j }
-      transformed.asJava // TODO "asJavaDeep" and optimise?
-    }
+  override def getTransform = (t: Iterable[jserver.Rejection]) => {
+    // explicit collects assignment is because of unidoc failing compilation on .asScala and .asJava here
+    val transformed: Seq[jserver.Rejection] =
+      transform(Util.convertIterable[jserver.Rejection, jserver.Rejection](t).collect { case r: Rejection =>
+        r
+      }).collect { case j: jserver.Rejection => j }
+    transformed.asJava // TODO "asJavaDeep" and optimise?
   }
 }
 
diff --git a/http2-tests/src/test/scala/org/apache/pekko/http/impl/engine/http2/Http2FrameHpackSupport.scala b/http2-tests/src/test/scala/org/apache/pekko/http/impl/engine/http2/Http2FrameHpackSupport.scala
index 8549de3436..48ebe3d320 100644
--- a/http2-tests/src/test/scala/org/apache/pekko/http/impl/engine/http2/Http2FrameHpackSupport.scala
+++ b/http2-tests/src/test/scala/org/apache/pekko/http/impl/engine/http2/Http2FrameHpackSupport.scala
@@ -60,11 +60,9 @@ trait Http2FrameHpackSupport extends Http2FrameProbeDelegator with Http2FrameSen
   def decodeHeaders(bytes: ByteString): Seq[(String, String)] = {
     val hs = new VectorBuilder[(String, String)]()
     decoder.decode(bytes.compact.asInputStream,
-      new HeaderListener {
-        def addHeader(name: String, value: String, parsedValue: AnyRef, sensitive: Boolean): AnyRef = {
-          hs += name -> value
-          parsedValue
-        }
+      (name: String, value: String, parsedValue: AnyRef, _: Boolean) => {
+        hs += name -> value
+        parsedValue
       })
     hs.result()
   }