Merge pull request #799 from akka/wip-2612-improve-receivetimeout-docs-√

#2612 - Clarifying ReceiveTimeout semantics in the documentation.

akka-docs/rst/java/code/docs/actor/MyReceivedTimeoutUntypedActor.java

@@ -11,13 +11,18 @@ import scala.concurrent.util.Duration;
 public class MyReceivedTimeoutUntypedActor extends UntypedActor {
 
   public MyReceivedTimeoutUntypedActor() {
+    // To set an initial delay
     getContext().setReceiveTimeout(Duration.parse("30 seconds"));
   }
 
   public void onReceive(Object message) {
     if (message.equals("Hello")) {
+      // To set in a response to a message
+      getContext().setReceiveTimeout(Duration.parse("10 seconds"));
       getSender().tell("Hello world", getSelf());
     } else if (message == ReceiveTimeout.getInstance()) {
+      // To turn it off
+      getContext().setReceiveTimeout(Duration.Undefined());
       throw new RuntimeException("received timeout");
     } else {
       unhandled(message);