Design question: Communication between objects

Hi all,
Just interested in some opinions from your experience. If you have two components, say two GUI components which are repesented by two separate classes, and you need to have these classes communicate in a relatively small way, how would you do it?
What I've done is passed a reference of the second object to the first.
I guess I'm wondering whether this would be considered a reasonable design, or should there be some in-between class which manages the communication between objects.
For a more concrete example: I have a main class (with my main() )which is a JFrame, and this frame has a split panel. I want the left and right sides to communicate with each other. Should I handle the communication through my main class, or should I "couple" the two classes upon initialization and let them do their communication independent of the my main class?
Thanks for any opinions or comments.

>
When the user selects a node on the JTree, I want to
populate a particular ComboBox on the right based on
what the user selected in the tree. Or I may just
re-initialize the entire right component based on the
selected node on the JTree.
I guess I was wondering whether I should "marry" the
JTree and the JPanel class, and let them do their
communicating when needed, or whether I should manage
the communucations through the JFrame class.
For example, say I use the JFrame as a "message
manager". The JFrame class will listen for events
from the JTree on the left side, and then send the
appropriate information to the right side. This way
the JTree class and the JPanel class would have no
knowledge of each other. They are glued together
through my JFrame.
Thanks for your opinions.
Then you must register a selection listener with the JTree with addTreeSelectionListener this listener has a reference to the combo. The listener can be a new class (inner class or anonymous) used only for this purpose.
Bye.

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Regards
David

Rommie and Rajesh,
Thank you both kindly for sharing your time and valuable knowledge. As I have only been programming with Java for a year part time (as one section of a Computer Systems Diploma) I consider myself to be a beginner in programming terms. I want to do really well with Java as quickly as possible and you have both helped me tremendously.
Rommie the methodology that you have passed onto me is great, thankyou so much, I feel like a new section of Java has completely opened to me. I will be using the third "reference" class methodology from everyday now on.
Rajesh your words are encouraging, and I will be reading up on Hierarchy and Aggregation immediately. When you said "Before using either, decide on the existence of the object, its intended functionalities e.t.c. ...", could you please explain with an example as to where Hierarchy is desirable and where Aggregation is desirable.
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E-mail: [email protected]
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Communication between two portlets
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