Tag: What is the purpose of using an observer?

The observer pattern in java is known for its use in design. Whenever an observable object changes its state, its corresponding observer classes are notified . Observable is implemented as a class which includes methods for managing Observer lists and notifying Observers.

Observable is used to create subclasses that other parts of the program can observe . When an object of such subclass undergoes a change, observing classes are notified. The update( ) method is called when an observer is notified of a change.

The responsibility of observers is to register (and unregister) themselves on a subject (to get notified of state changes) and to update their state (synchronize their state with the subject’s state) when they are notified.