I would recommend against doing this. The interaction should instead use something like XML over HTTP or a SOAP call. While you can undoubtedly make it work via a Java service it is not the typical communication approach for IS-based solutions.
Side trip: The following is not intended to criticize shafi but more of a commentary on the relative irrational tendency of our industry to refer to everything as a service (we used to call everything objects). Remote Method Invocation has nothing to do with services in an SOA sense.* As the name explicitly states–it is the calling of a method of an object hosted remotely.
- wM IS services aren’t services in an SOA sense either–but the labelling of FLOW and Java components in IS as services precedes the current SOA hype.
[end soap box] 
#Integration-Server-and-ESB#webMethods#Flow-and-Java-services