Listing users and files

Hi all,

I want to write a Java web application that using Confluence API to list all users and all the files, and documents they have on Confluence cloud. I am new to Confluence Cloud development; there are different options of Authentication (Basic, OAuth 2, and JWT), which one is best for my purpose? I need to have a way that I don’t have to generate a new access token (the token is never expired). I cannot find any Confluence API SDK. It seems that the only API for Confluence is the REST API, is it right?
Thanks.