You're asking about two different things. One is to change the WS implementation so that the WSDL picks up that change. The other is to run wsdl2java to regenerate the client-side code. How to use wsdl2java should be explained in the documentation of whichever SOAP stack you're using (Axis 2 ?).
Thanks for your response, I'm able to successfully generate the proxy clases from wsdl. I'm using JAX-RPC runtime. But I'm observing some differences between the existing proxy classes and the newly generated proxy clases. The newly generated class files exposes two more new methods which is not related to my change. The existing proxy clases were generated using RAD 6 and now I'm using RAD 7.5 to generate the new proxy clases. Did anyone ever observed one such differences due to RAD version change?