Host Support for Packages

Question

Hi, I have been trying to get the proper definition of "observable" in the Java Language Specifications 2. However, it seems that a package is "observable" if its compilation units are "observable". Compilation units' observability depends on the host system! ??? How can I determine whether a compilation unit is observable and what is the difference between "observable" and "accessible".
Thank you!
Luka

Answer 1

Its not as tough as you feel. Consider you have 2 classes , one extends Observable , another implements Observer. Both are linked by the Observer implementation "public void update(Observable o, Object arg) ". Whenever the instance of the Observable object changes, it will notify the Observer implementation through the update method.
Following lines are taken from the API :
" 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. "
Hope this has given a start for your understanding this concept.
Rajesh