This class represents an observable object, or "data" in the model-view paradigm. It can be subclassed to represent an object that the application wants to have observed.
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
causes all of its observers to be notified of the change by a call
The order in which notifications will be delivered is unspecified. The default implementation provided in the Observable class will notify Observers in the order in which they registered interest, but subclasses may change this order, use no guaranteed order, deliver notifications on separate threads, or may guarantee that their subclass follows this order, as they choose.
Note that this notification mechanism is has nothing to do with threads and is completely separate from the wait and notify mechanism of class Object.
When an observable object is newly created, its set of observers is empty. Two observers are considered the same if and only if the equals method returns true for them.
Public Constructor Summary
Construct an Observable with zero Observers.
Public Method Summary
Returns the number of observers of this Observable object.
Clears the observer list so that this object no longer has any observers.
Tests if this object has changed.