add examples for scan operator #25468

akka-docs/src/main/paradox/stream/operators/Source-or-Flow/scan.md

@@ -31,3 +31,10 @@ Note that the `zero` value must be immutable.
 
 @@@
 
+## Examples
+
+Scala
+:  @@snip [SourceOrFlow.scala](/akka-docs/src/test/scala/docs/stream/operators/SourceOrFlow.scala) { #scan }
+
+Java
+:  @@snip [SourceOrFlow.java](/akka-docs/src/test/java/jdocs/stream/operators/SourceOrFlow.java) { #scan }

akka-docs/src/test/java/jdocs/stream/operators/SourceOrFlow.java

@@ -172,6 +172,19 @@ class SourceOrFlow {
     //#conflate
   }
 
+  void scanExample() {
+    //#scan
+    Source<Integer, NotUsed> source = Source.range(1, 5);
+    source.scan(0, (acc, x) -> acc + x).runForeach(System.out::println, materializer);
+    // 0  (= 0)
+    // 1  (= 0 + 1)
+    // 3  (= 0 + 1 + 2)
+    // 6  (= 0 + 1 + 2 + 3)
+    // 10 (= 0 + 1 + 2 + 3 + 4)
+    // 15 (= 0 + 1 + 2 + 3 + 4 + 5)
+    //#scan
+  }
+
   static //#conflateWithSeed-type
   class Summed {
 

akka-docs/src/test/scala/docs/stream/operators/SourceOrFlow.scala

@@ -52,4 +52,23 @@ object SourceOrFlow {
     //#conflateWithSeed
   }
 
+  def scanExample(): Unit = {
+    import akka.actor.ActorSystem
+    import akka.stream.ActorMaterializer
+
+    implicit val system: ActorSystem = ActorSystem()
+    implicit val materializer: ActorMaterializer = ActorMaterializer()
+
+    //#scan
+    val source = Source(1 to 5)
+    source.scan(0)((acc, x) ⇒ acc + x).runForeach(println)
+    // 0  (= 0)
+    // 1  (= 0 + 1)
+    // 3  (= 0 + 1 + 2)
+    // 6  (= 0 + 1 + 2 + 3)
+    // 10 (= 0 + 1 + 2 + 3 + 4)
+    // 15 (= 0 + 1 + 2 + 3 + 4 + 5)
+    //#scan
+  }
+
 }