Just for those wondering around what is WSDL file or technology in the area of Business 2 Business (when companies speak to each other automatically over the network): you can think of it as a declaration of the client-server conversation. In this case one B (server) provides some functionality (like taking square roots of big numbers) and another B (client) has a lot of these numbers and needs square roots of them.
So the server declares a method (which is in fact a remote method):
Double squareRoot(Double number)
in its WSDL file. The client side then takes this file and generates the client side code, which handles the protocol of communication and remote method invocation automatically. What client needs is simply to implement a business logic around this invocation, like a web page with a text field for the number or the entire hardware with touch screen display.
In general the input and return types of remote methods can be simple and complex -- in fact as complex and "proprietary" as you need, because the entire WSDL file is nothing but xml as well as the messages being sent over the network.
One of the libraries used in the industry is Axis and Axis2. Using the library you can generate the java code from wsdl for you client (and even generate wsdl from your java code for you server).