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What is Observer and Observable?

Hemant Agarwal
Ranch Hand

Joined: Nov 21, 2005
Posts: 138
What is Observer and Observable? What is their use?
fred rosenberger
lowercase baba

Joined: Oct 02, 2003
Posts: 11923

They're part of the Observer pattern. you have one object that notifies a bunch of others when needed. many "observers" may register with an "observable", and all may un-register.

Check out the Head First Design Patterns book, or google "design patterns observer" and you'll find tons of into...

There are only two hard things in computer science: cache invalidation, naming things, and off-by-one errors
Ulf Dittmer

Joined: Mar 22, 2005
Posts: 42959
There's a good IBM Developerworks tutorial on event delivery techniques, which you can find here. It covers Observer/Observable, JavaBean event techniques and more.
[ January 01, 2006: Message edited by: Ulf Dittmer ]
It is sorta covered in the JavaRanch Style Guide.
subject: What is Observer and Observable?
It's not a secret anymore!