find the current class

Jetbrains have a lot of useful articles on their confluence page that are worth looking at, for instance here are a few ways to achieve what you're after - http://confluence.jetbrains.com/display/IDEADEV/IntelliJ+IDEA+Architectural+Overview#IntelliJIDEAArchitecturalOverview-PsiFiles

For your code to work, the focus (or Cursor) has to be in the Editor. If not, you would get NULL.

Following code will give you the class name :

PsiFile psiFile = e.getData(DataKeys.PSI_FILE);
System.out.println("psiFile.getName() = " + psiFile.getName());

Or if you want the actual path to the file, then use the following code :

PsiFile psiFile = e.getData(DataKeys.PSI_FILE);
System.out.println("psiFile.getVirtualFile().getCanonicalPath() = " + psiFile.getVirtualFile().getCanonicalPath());

You can also get the Virtual File directly by :

VirtualFile virtualFile = e.getData(DataKeys.VIRTUAL_FILE);