The "Allow service to interact with the desktop" property is a binary flag stored in the Type value for the service in the registry. To see it in action, open regedit and go to HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\xxx, where xxx is any service. Observe the current value of Type. Then change the service with Services control panel and not the flag that is set/unset.
How do you change that in Java? You can't. Unless you can find a Java library that can edit the registry. The most you can hope for is to have Java call an application that can make this change. By the way, it would be easy to write a PowerShell script to make such a change, and it is easy to run PowerShell from Java using System.exec().