What is use of observer and Observable in java?

The java.util.Observable class represents an observable object, or “data” in the model-view paradigm .Following are the important points about Observable − The class can be subclassed to represent an object that the application wants to have observed. An observable object can have one or more observers.

A class that implements the Observable interface allows the registration of listeners that want to be notified of property changes of on the observable object .

The Java language supports the MVC architecture with two classes: Observer : Any object that wishes to be notified when the state of another object changes. Observable : Any object whose state may be of interest, and in whom another object may register an interest .

An observable object can have one or more observers . An observer may be any object that implements interface Observer. After an observable instance changes, an application calling the Observable ‘s notifyObservers method causes all of its observers to be notified of the change by a call to their update method.