This can help:
import officetools.OfficeFile; // available at dancrintea.ro/xls-to-pdf/
...
FileInputStream fis = new FileInputStream(new File("test.xls"));
FileOutputStream fos = new FileOutputStream(new File("test.csv"));
OfficeFile f = new OfficeFile(fis,"localhost","8100", true);
f.convert(fos,"csv");
All possible conversions:
XLS --> pdf, html, CSV
doc --> pdf, html, txt, rtf
ppt --> pdf, swf
html --> pdf