In NetBeans 3.4 and earlier, there were two basic 
approaches for choosing a file. One was to use a 
JFileChooser over the content of the whole disk, and the 
other was to use the NetBeans explorer-based chooser for 
objects mounted in FileSystems.

In NetBeans 4.0, there are many new concepts which require 
a new framework for a file chooser.

First, since the roots of filesystems are mounted, the 
distinction between the JFileChooser approach and the 
explorer containing all filesystems disappears.

Secondly, it may be useful to limit the selection to a 
subset of files, such as:
- all files in a given project
- other projects and files in them
- other projects and targets in them
- resources of a project
- all files on the classpath of a given project
- any other selection provided by modules, such as "all 
files in web applications"

Thirdly, it will be a requirement to allow mounting a VCS 
filesystem in the chooser, because as the user is not 
expected to interact with the Filesystems tab very much, 
she must be given the opportunity to mount a VCS FS later 
when she needs it, which may be when she is choosing a 
file.

It would be also useful to give the user the choice for 
which selection to use, by having tabs in the chooser 
which would say
"All Files"
"Files in Project"
"All Projects"
"Files on Classpath"
etc.

Also, individual clients (modules) of the chooser should 
be able to show some tabs, and not others, so for example 
if the Java module knows that the file chosen *has* to be 
on the classpath, it should be able to only allow "Files 
on Classpath", and disable "All Files" and similar.