The Observer pattern is ... you will find the code of all the framework participants. I assume you understand the basics of EJBs, synchronization, and of course, the core Java libraries.

The Observable design pattern is used in many important Java APIs ... Let’s use an example of a newsletter to implement the Subject interface. In the following code, we store our observers ...

The code that implements these classes is shown in Listing 6. To illustrate the Observer Pattern concretely, I chose to create a Town Crier class that sends messages to any registered Town Resident ...