move code to src/test

* so that it compiles and tests pass
* fix some additional snip references in getting started

akka-docs/src/test/java/jdocs/dispatcher/MyUnboundedMailbox.java

@@ -0,0 +1,51 @@
+/**
+ * Copyright (C) 2009-2017 Lightbend Inc. <http://www.lightbend.com>
+ */
+package jdocs.dispatcher;
+
+//#mailbox-implementation-example
+import akka.actor.ActorRef;
+import akka.actor.ActorSystem;
+import akka.dispatch.Envelope;
+import akka.dispatch.MailboxType;
+import akka.dispatch.MessageQueue;
+import akka.dispatch.ProducesMessageQueue;
+import com.typesafe.config.Config;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.Queue;
+import scala.Option;
+
+public class MyUnboundedMailbox implements MailboxType,
+  ProducesMessageQueue<MyUnboundedMailbox.MyMessageQueue> {
+
+  // This is the MessageQueue implementation
+  public static class MyMessageQueue implements MessageQueue,
+      MyUnboundedMessageQueueSemantics {
+    private final Queue<Envelope> queue =
+      new ConcurrentLinkedQueue<Envelope>();
+
+    // these must be implemented; queue used as example
+    public void enqueue(ActorRef receiver, Envelope handle) {
+      queue.offer(handle);
+    }
+    public Envelope dequeue() { return queue.poll(); }
+    public int numberOfMessages() { return queue.size(); }
+    public boolean hasMessages() { return !queue.isEmpty(); }
+    public void cleanUp(ActorRef owner, MessageQueue deadLetters) {
+      for (Envelope handle: queue) {
+        deadLetters.enqueue(owner, handle);
+      }
+    }
+  }
+
+  // This constructor signature must exist, it will be called by Akka
+  public MyUnboundedMailbox(ActorSystem.Settings settings, Config config) {
+    // put your initialization code here
+  }
+
+  // The create method is called to create the MessageQueue
+  public MessageQueue create(Option<ActorRef> owner, Option<ActorSystem> system) {
+    return new MyMessageQueue();
+  }
+}
+//#mailbox-implementation-example