I think usb4java would definitely work for sharing files between an android device and a desktop pc, but to get this working you would need a lot of know how over the basics of USB, the basics of usb mass storage and at last a lot of knowledge over your working desktop system. (Windows Kernel). When you have all the information, I think this would work in claiming the interfaces, sending some control transfer and at last performing a bulk transfer.
I think it would be easier to search some examples of libusb in C code, because here you would find the most examples and then rewrite the program shema to your java sample using usb4java.
Von meinem Sony Xperia™-Smartphone gesendet