A DESCRIPTION OF THE REQUEST :
Bugs such as 4418831 and 4242635 show that java.io.File(File, String) and (String, String) don't behave consistently with expectation when the second argument is an absolute or drive-relative (in Windows) path. A new method should therefore be created that deals with these situations in a consistent way and avoids the need for developer's to jump through hoops in order to get simple path joining capabilities (viz-a-viz Python's os.path.join(.) function).
Or you could just fix the dodgy constructors...
To make Java better. Less hair loss over inane behaviour is always a good thing.