Rename Receiver.java to Consumer.java.
Replace static main methods with instance methods. Add point-to-point message unit tests.
Extract channel, connection creation and clean-up codes into private methods.
Remove boolean flag returned by Producer.sendMessage().
Add internal list to Consumer to store messages received.
Remove string returned by Consumer.receiveMessage().
Add a 'message' string argument to Producer.sendMessage().
Promote public methods to top of class.