The Observer Pattern

Observer Pattern likes relation subscribe and publish that define a one to many dependency, if one change the states that all dependency  could changed the srates automatic.

For example there is a Service that provide some subscribe and publish services, and you can subscribe one or more of these services.

Each one make a subscriber, the service will publish the service to you.

The simple Observer Pattern is

interface ObseverServer {
  void addObserver(Observer observer);
  void removeObserver(Observer observer);
  void notifyChanges();
}

interface Obsever() {
  void update();
}

The one to many dependency when the states of ObseverServer changed , all of Obsever will update.

In the java there are the java.util.Observable and java.util.Obsever to implement the Obsever Pattern.

there is no example in the project,so just write some concept.