Changes

Abstract coupling between subject and observer: All a subject knows is that it has a list of its there are observers. Because Since the subject and observer aren't tightly coupled, they the two objects can belong to be on different layers of abstraction in a system.

Support for broadcast communication: The notification that When a subject sends doesn't have to out a notification it does not specify its a receiver. The subject doesn't care about how many observers are observing it, all it does is a broadcast of just broadcasts its current change of its state.

Unexpected updates: A cascade of Since observers do not know about the other observers which may or may not be watching the subject, there may be a lot of updates to observers the observes and their dependent the objects may occur when which could result in an observer does a change to a subjectendless loop.  == Links ==http://www.dofactory.com/Patterns/PatternObserver.aspx#_self1 <br />http://en.wikipedia.org/wiki/Observer_pattern <br />http://sern.ucalgary.ca/courses/SENG/609.04/W98/lamsh/observerLib.html <br />http://www.java2s. This occurs because the observers do not know of other observerscom/Code/Java/Design-Pattern/Observer-Pattern.htm <br />