This is an implementation of the observer pattern.
The Observer pattern is defined as
a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.
You can take advantage of java.util.Observable in your own usage of the Observer pattern
- an abstraction has two aspects, one dependent on the other. Encapsulating these aspects in separate objects lets you vary and reuse them independently
- a change to one object requires changing others, and you don't know how many objects need to be changed
- an object should be able to notify other objects without making assumptions about who these objects are. In other words, you don't want these objects tightly coupled