I would definitely prefer to use Java to generate RTF documents than Word documents. Word is very proprietary and this year's Word document format is not next year's Word document format is not last year's Word document format.
I have not yet run across an API that just outputs Word documents from Java. I know the group working on the POI project over at Jakarta are developing such an API to generate Word '97 documents. I'm not sure how far along they are. Take a look at
their project site for more information.
Mueller Und Stein offer a free Java Bean to control Microsoft Word.
Otherwise, perhaps there is an indirect path through XML to get from Java to Word (and perhaps back again).
Good Luck.