rename akka-docs dir to docs (#62)

docs/src/test/java/jdocs/actor/SampleActor.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2009-2022 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package jdocs.actor;
+
+// #sample-actor
+import org.apache.pekko.actor.AbstractActor;
+
+public class SampleActor extends AbstractActor {
+
+  private Receive guarded =
+      receiveBuilder()
+          .match(
+              String.class,
+              s -> s.contains("guard"),
+              s -> {
+                getSender().tell("contains(guard): " + s, getSelf());
+                getContext().unbecome();
+              })
+          .build();
+
+  @Override
+  public Receive createReceive() {
+    return receiveBuilder()
+        .match(
+            Double.class,
+            d -> {
+              getSender().tell(d.isNaN() ? 0 : d, getSelf());
+            })
+        .match(
+            Integer.class,
+            i -> {
+              getSender().tell(i * 10, getSelf());
+            })
+        .match(
+            String.class,
+            s -> s.startsWith("guard"),
+            s -> {
+              getSender().tell("startsWith(guard): " + s.toUpperCase(), getSelf());
+              getContext().become(guarded, false);
+            })
+        .build();
+  }
+}
+// #sample-actor