Class organisation for long project

Question

Hello there,
I have developed a system for some collegues which, among many others, contains a single class that shows the output of their work in a GUI. My work contract runs out soon, however, these guys are going to need to continue to develop this GUI - probably by making another GUI class, which contains much of my code.
My problem lies here: currently, my GUI class called GUI_Main sets up everything, and also passes itself as parameter to several other classes, which run as threads or whatever, so they can call methods on my GUI class once they have completed some work - to update the GUI. So; if my collegues create another GUI class sometinme, and they copoy my code and try to pass this class to other classes to update the GUI, it will fail.
To regular Java programmers, this is a problem which can be solved trivially e.g. change the parameter types for those classes which take references to GUI_Main. However ,then there is the issue of not the original GUI_Main not working.
I was thinking about creating an abstract class which defines the method signatures of all of the methods used by other classes to update the GUI. Then making GUI_Main and whatever other GUI class that is developed to extend this abstract class. Then, I could change the parameter types for those classes which originally were references to GUI_Main to this new abstract class.
I wanted to make this an abstract class, and not an interface because GUI_Main is a JFrame - meaning that I would be able to make it extend JFrame. Is this ok?
Sorry if this is too long a message - but any help on general programming practise would be very greatly received.
- yours sincerely,,
Edward Turner.

Answer 1

Make it an interface, and phrase the method names in as generic way as possible. This will allow the greatest amount of reuse.
eg:
if there is something like refreshOutputPanel(ResultsData data) in GUI_Main, which is called when a Thread CalculateResultsData finishes running, make an interfaceinterface ResultsDataTarget {
void resultsDataCalculated (ResultsData data);
}that captures the higher level event rather that the result specific to a single GUI implementation.
That way not only can other GUIs by used (eg an AWT dialog), the same callback interface can be used inside an application server or console app, should the need arise in the future.
Pete