With Excel (actually saving in .xls format) you really only have two
options. 1) OLE/COM automation and 2) Apache POI. If you are writting
this as a library for use in automated test development, you should
have no problems (OLE will be easier). If you are trying to get it
worked into the editor (I believe Functional Tester is eclipse based,
allowing plugins) then you might have alot more work cut out for you.
For COM usage in java, I like JACOB: http://www.yqcomputer.com/
POI is pretty handy too: http://www.yqcomputer.com/