Hello @Maria_Rousi and welcome to the forum!
I’ll check with the team and get back to you if any of us has experience with this, but so far none of us has called the API from Java…
What Java libraries have you tried? I did a quick search and found this one specifically for android that has quite a few examples: 11. Write your first subscription - Client (Android) - Apollo GraphQL Docs
I’d be also super interested to hear what you’re building, and if you get a chance you can always Introduce yourself 🙆 !
P.S.
There are quite a few frameworks that let you build Android apps in javascript, if that’s an option we’d definitely be able to assist you more in working with the API!