CMIS is a standard that defines two bindings - RESTful HTTP API and SOAP Web Services, so CMIS doesn't define Java APIs.
That said, there are Java layer underneath the RESTful services, although that's not meant to be used by developers (although you obviously could).
We also have Core Java Repository services (NodeService, ContentService, VersioningService, etc) that we expose - you are welcome to use those - from your question the use case is not clear.
