It is a very common need to retrieve the "main" class contained inside a
SourceElement. This would be the class named according to the source file. But
it is I think more work than it ought to be:

- getClasses()[0] usually works, but some strange person could put a
package-private class before the main class

- getClasses() and search for the public one works, if there is some public one
(it is an error for there to be more than one); but I guess not if they are all
package-private

- getClasses() and search for the one with the same name as the source file
might be best; but SourceElement does not have the source name, I think, you
have to getCookie(DataObject.class)...

In short, all of these approaches might get you what you want but they are a lot
of code and probably not 100% reliable. It would be nice if there were a simple
method in SourceElement, getMainClass (?) which could return null, whose
implementation would try to find what the Java compiler would consider the
primary outer class in the file (possibly null in case of an erroneous source).