Hello Disha
I believe that the best starting point for this conversion is the requirements document for this report.
Read the document carefully and see if you can identify specific "business objects".
Each of these "business objects" may become an own class.
Very important: if, for example, your report is dealing with lots of invoices do NOT care about the quantity but think exclusively about ONE "invoice object".
Next identify for each object the required methods.
Finally, compose your objects together. For this you will probably need another class.
I can give you an example of a "report" I have written recently:
This "report" deals "Actual Assessment Cycles" (transaction KSU2). Because it was a dialog I created three classes: controller class, model class and view class (MVC architecture). I had about six different classes (for objects "CATS data", "employee", "Cycle", "Exceptions",...) that I composed together into the model instance (which should hold the buinsess logic). The view instance contained the controls for display (three ALV lists) and the controller instance was responsible for handling the user interactions.
A final remark: There are only rare occasions where we should use local classes. In general, create global classes (even if nobody else will use them) because the transparency is much better than with local classes (especially if the classes become bigger and bigger).
Hope I could give you some ideas.
Regards
Uwe
PS: It's worthwhile doing this shift from classical ABAP to ABAP-OO.
Bluesky
