Listener on a list

Question

Hi everybody,
I would like to have a listener on a list. More acurately i want to be notified when an element is added into my list. How can i do ? Should i have to write my own list implementing a listener or does such implementation already exists ? If somebody already write this code can i have a sample please ?
Thanks.
Manu

Answer 1

Thanks and sorry i made a mistake in my previous
post. I have already saw the defaultListModel wich is
the default implementation of the interface you
suggest to me.
Using this interface means write my own
implementation and it is maybe quite difficult to
write "reliable". No more difficult than writing most anything else to be reliable, I wouldn't think.
According to you i have to and i
can reuse this class ?You don't have to, there are options - you can use the DefaultListModel class (or something else in the API) you could write your own class that may or may not implement the ListModel interface, you could check out the java.util.Observable/java.util.Observer class/interface pair, you could start from scratch and write your own everything.
If all you want is a List implementation that supports the idea of "Observablility" then maybe you should write up something that either extends AbstractList and adds the "add/removeListener" methods and overrides the add method to fire events off at your Listeners (but check out the default implementation of the addAll method, that might not be a behavior you want) (also see think about if you want to fire change events when elements are removed from your list). Or extends the Observable class and implements List (maybe taking a List in a ctor and delegating to it) and then your listeners can implement the Observer interface.
http://www.javaworld.com/javaworld/jw-10-1996/jw-10-howto.html
Or, if you don't want to deal with those classes, just write up your own Listener intrerface with one "somethingHappened" method and use that.
Good Luck
Lee