I had to write all the REW graphing code from scratch, couldn't find anything that had what I wanted. However, Romain Guy has since produced a very nice graph component that he's committed to the swingx project, you can get the source and browse the javadoc at
http://swinglabs.org/downloads.jsp and see a screenshot of the component in use at
http://www.jroller.com/page/gfx?entry=jxgraph_in_swingx
All REW audio interfacing is through the standard JavaSound classes. Regarding soundcard frequencies, you can query the mixers to ask what formats they support but often the answer will be NOT_SPECIFIED (-1), meaning the mixer will support most rates you might ask for - to get anything more specific you have to request a line of the format & rate you want and see whether the mixer says it supports it. More info available at
http://www.jsresources.org/
HTH,
John