How to connect oracle database docker image
You better check whether DB is running at all by checking your container status.
This link has a lot of information about Oracle in container (credits to chuck and his comment).
https://www.toadworld.com/platforms/oracle/b/weblog/archive/2017/06/21/modularization-by-using-oracle-database-containers-and-pdbs-on-docker-engine
wrt tags, seems like this is an old image, check docker inspect ...
to see when it was produced. You may see other tags as well.
For a newer version you can check instructions how to build by yourself at: https://github.com/3scale/oracle-database
Update: link to more official instructions for building Oracle images https://github.com/oracle/docker-images