How to authenticate a mobile app in the backend services

I'm currently developing a mobile app that doesn't have user login feature, so I can't implement user session token. But I want to authenticate the mobile app to the server. Since we have some get URL, I want to verify that it is the mobile app installed on the mobile device that is sending the request and not a standalone program.

Any idea where to begin? I have a REST web service on javaEE.

Thanks