How to implement an application that works with a remote database?

Question

Java

The application must read and change the data. The database itself must be somewhere on the network.
How to implement all this? What hosting to use? (Is it necessary to have a database)
Data from the hosting can be parsed, but not edited. I tried to download a file with text via ftp, and then upload it (it didn’t work to upload it via ftpclient).
I read about Retrofit, but as I understand it, it is not needed for this task (or I'm wrong).
Explain how this kind of application works, where data is read, changed and uploaded back.
Thank you.

Answer 1

Try Firebase, specifically Realtime Database. It’s convenient because you don’t need to write any backend.

Answer 2

Listen, there is jdb, which can connect to any host. The question is only in the settings of the database itself, so that it would allow requests from outside to pass to itself.

Answer 3

Look at any cloud