How to add RXTX serial API's javadoc to eclipse or netbeans?

I tried to add the exteranl javadoc from project properties --> libraries --> javadoc loca开发者_如何转开发tion. I tried both local directory, ...\RXTX_example\documentation\public or from http://users.frii.com/jarvi/rxtx/doc/index.html in eclipse. But neither of them gives a correct result and it only shows a note: The Javadoc for this element could neither be found in the attached source nor the attached Javadoc.

Try http://users.frii.com/jarvi/rxtx/doc/ (i.e. without the index.html) as the location. This worked for me in Eclipse (but for another library).