NEED JAVA I/O HALP BAD

if the user gives me the name of a file, how do i establish a connection/begin working with the file itself? sorry if this sounds stupid but i has no textbook and my professor spent only about ten seconds on this in lecture while i was looking the other way. (a multitude of internets to whoever knows)

#4
What the fuck is your problem man?
#5
I want to establish a connection with the file itself not this stream thing..