Examples for the sliding operator #25468

akka-docs/src/test/java/jdocs/stream/operators/sourceorflow/Sliding.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2009-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package jdocs.stream.operators.sourceorflow;
+
+import akka.NotUsed;
+import akka.actor.typed.ActorSystem;
+import akka.stream.javadsl.Source;
+
+import java.util.Arrays;
+import java.util.stream.Collectors;
+
+public class Sliding {
+
+  private final ActorSystem<Void> system = null;
+
+  public void slidingExample1() {
+    // #sliding-1
+    Source<Integer, NotUsed> source = Source.range(1, 4);
+    source.sliding(2, 1).runForeach(n -> System.out.println(n), system);
+    // prints:
+    // [1, 2]
+    // [2, 3]
+    // [3, 4]
+    // #sliding-1
+  }
+
+  public void slidingExample2() {
+    // #sliding-2
+    Source<Integer, NotUsed> source = Source.range(1, 4);
+    source.sliding(3, 2).runForeach(n -> System.out.println(n), system);
+    // prints:
+    // Vector(1, 2, 3)
+    // [1, 2, 3]
+    // [3, 4] - shorter because stream ended before we got 3 elements
+    // #sliding-2
+  }
+
+  public void slidingExample3() {
+    // #moving-average
+    Source<Integer, NotUsed> numbers = Source.from(Arrays.asList(1, 3, 10, 2, 3, 4, 2, 10, 11));
+    Source<Float, NotUsed> movingAverage =
+        numbers
+            .sliding(5, 1)
+            .map(window -> ((float) window.stream().mapToInt(i -> i).sum()) / window.size());
+    movingAverage.runForeach(n -> System.out.println(n), system);
+    // prints
+    // 3.8 = average of 1, 3, 10, 2, 3
+    // 4.4 = average of 3, 10, 2, 3, 4
+    // 4.2 = average of 10, 2, 3, 4, 2
+    // 4.2 = average of 2, 3, 4, 2, 10
+    // 6.0 = average of 3, 4, 2, 10, 11
+    // #moving-average
+  }
+}