How much should we rely on "Parent" nodes like group?

Question

So I'm curious how much overhead does these groups, regions, panes, etc take up, and is there a point to worry about them?
in the current application I'm working on I was thinking of having a group of bookstypes, within a group of bookshelves, within a group of bookcases. So technically I could have 5 groups on a shelf, 5 shelf groups on a bookcase, and 10 book cases being displayed at once, 250 is a lot of groups.
Now I've seen people post on here saying that have hundreds of groups and such, so I think I'll be okay, but I'm just curious what the practice on these things are. Groups to me are going to make everything much easier, but I don't want to take "easy" for "slower." So if I didn't have these groups I would have to worry about where each book type is on each shelf, where each shelf is on each bookcase, for dragging, moving, rotating, etc.

Answer 1

Yes, you want a class to do "one thing." Of course, "one thing" can be kind of fuzzy, but there sould be one core responsibility, with maybe a couple of different ways of accomplishing it, or a couple of different aspects or faces to that responsibility.
As an example that I pull out of you-don't-wanna-know-where, look at java.io.File.
It does "one thing", but it's really sort of multiple aspects of or tasks associated with that one thing.
The one thing being "model a file on the file system" and the multiple tasks being, find out the file's type (directory or regular file), create the file, delete the file, list the "file's" (directory's) contents, etc.
As for .java file length, It does vary on a class to class basis, and depending on whether you put braces on a line by themselves, how much you comment, etc. In general though, my classes tend to be a couple dozen to a couple hundred lines in length. If they start getting bigger than that, I look closely to see if it makes sense to refactor. If I see a 1000 line .java file.
Note, though, that generated .java files (e.g. from compiling JSPs, or various source code generation tools) tend to be longer, and one doesn't generally farg around with them by hand.