Restriction:
This is supported for Java only.
You can only debug Java classes that have been registered with the debugger or classes that are part of packages that have been registered with the debugger. Registered classes and packages are those that appear in the Packages pane.
To register a class or package with the debugger:
If you want to register more than one class with the debugger, click Open to register the class you just entered. Then register your next class. When you have registered all your classes, click OK.
If the class you entered is part of a package, the entire package is registered with the debugger as well as the class you entered.