Some methods take a File object purely to read or write to it (i.e. they don't do anything related to the filesystem). In this case it would be useful to have an overload that takes a Reader or Writer, so that e.g. data can be written directly to a string, or read directly from a URL. Particularly handy for unit tests, to save the time and inconvenience of writing to a file, immediately reading from it again, and deleting it.
Some methods take a File object purely to read or write to it (i.e. they don't do anything related to the filesystem). In this case it would be useful to have an overload that takes a Reader or Writer, so that e.g. data can be written directly to a string, or read directly from a URL. Particularly handy for unit tests, to save the time and inconvenience of writing to a file, immediately reading from it again, and deleting it.