NetBeans is an integrated development environment (IDE) for Java and other languages.
You can get a free copy of NetBeans at http://www.netbeans.org/. These instructions assume that you have been able to download, install, and start NetBeans.
Although you probably put the source code in a different place than shown in this example, the relative location of subdirectories in the source code will be the same as shown here.
For debugging to work, you need to select directories containing the root-level Java package. For omar, they are the directories shown, since they each contain a org directory that corresponds to the org in the org.freebxml.omar... package names used in the source code.
You could, for example, select src instead and still be able to edit the code in NetBeans, but you wouldn't be able to step into the code when debugging.
You should now have three (or four) "local filesystems".
When you want to run a project's program from within NetBeans, you should set the project's "main class".
This is probably not so necessary when you are attaching to a running program.
The simplest way to debug the registry server is to start its servlet container with debugging enabled and then attach the NetBeans debugger to the running servlet container.
See the Debugging page for how to start the servlet container with debugging enabled.

Figure 10 - Selecting "Toggle Breakpoint"
Alternatively, you can select the line with a left-click and then press Shift-F8 on your keyboard to toggle the breakpoint.
Lines with a breakpoint set are highlighted in pink.
You can use NetBeans to checkout and manage your local copy of the CVS files. These are the instructions to set it up and checkout OMAR (based on NetBeans 4.0):
You can also register a working dirictory which you have already checked out (using command line cvs tool, for instance). To process is similar and the other parameter will be filled once you choose the working directory.