Examples for zipN, zipWithN and zipAll (#28510)

akka-docs/src/test/java/jdocs/stream/operators/source/Zip.java

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+/*
+ * Copyright (C) 2009-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package jdocs.stream.operators.source;
+
+import akka.NotUsed;
+import akka.actor.ActorSystem;
+import akka.stream.javadsl.Source;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class Zip {
+
+  void zipNSample() {
+    ActorSystem system = null;
+
+    // #zipN-simple
+    Source<Object, NotUsed> chars = Source.from(Arrays.asList("a", "b", "c", "e", "f"));
+    Source<Object, NotUsed> numbers = Source.from(Arrays.asList(1, 2, 3, 4, 5, 6));
+    Source<Object, NotUsed> colors =
+        Source.from(Arrays.asList("red", "green", "blue", "yellow", "purple"));
+
+    Source.zipN(Arrays.asList(chars, numbers, colors)).runForeach(System.out::println, system);
+    // prints:
+    // [a, 1, red]
+    // [b, 2, green]
+    // [c, 3, blue]
+    // [e, 4, yellow]
+    // [f, 5, purple]
+
+    // #zipN-simple
+  }
+
+  void zipWithNSample() {
+    ActorSystem system = null;
+
+    // #zipWithN-simple
+    Source<Integer, NotUsed> numbers = Source.from(Arrays.asList(1, 2, 3, 4, 5, 6));
+    Source<Integer, NotUsed> otherNumbers = Source.from(Arrays.asList(5, 2, 1, 4, 10, 4));
+    Source<Integer, NotUsed> andSomeOtherNumbers = Source.from(Arrays.asList(3, 7, 2, 1, 1));
+
+    Source.zipWithN(
+            (List<Integer> seq) -> seq.stream().mapToInt(i -> i).max().getAsInt(),
+            Arrays.asList(numbers, otherNumbers, andSomeOtherNumbers))
+        .runForeach(System.out::println, system);
+    // prints:
+    // 5
+    // 7
+    // 3
+    // 4
+    // 10
+
+    // #zipWithN-simple
+  }
+
+  void zipAllSample() {
+    ActorSystem system = null;
+    // #zipAll-simple
+
+    Source<Integer, NotUsed> numbers = Source.from(Arrays.asList(1, 2, 3, 4));
+    Source<String, NotUsed> letters = Source.from(Arrays.asList("a", "b", "c"));
+
+    numbers.zipAll(letters, -1, "default").runForeach(System.out::println, system);
+    // prints:
+    // Pair(1,a)
+    // Pair(2,b)
+    // Pair(3,c)
+    // Pair(4,default)
+    // #zipAll-simple
+  }
+}