Well, the java.io.File class has a renameTo() method, which can move and rename files around on the same filesystem (same volume, in Windows-speak.) So a simple version could just use this method.
But renameTo() can fail, and it indicates failure by returning "false". To move a file that renameTo() can't move, you need to open the old file with FileInputStream, open the new location with FileOutputStream, read the bytes from the input, write all the bytes to the output, close the streams and delete the input file. The
I/O section of the Java Tutorial would be helpful to you in implementing this.