Is XE like the old personal oracle where it is installed on a developers local machine and user access is only through a local SQLPLUS connection (or some development tool local to the XE database), or can it be accessed by a remote client OCI, JDBC , etc.
Yes remote connections are allowed. If they are enabled and allowed by the host.
If the client has the correct configuration to get to the database, the database listener is running, and the host does not have the listener port blocked in the firewall.
If you don't want remote connections, stop the listener. Or leave the listener port blocked in the firewall that will have the same effect as stopping the listener.
Or shutdown the database. That will also have the same effect.
And jdbc can be challenging in its own ways, and x64 and windows (and java versions too) can muddle up the details.
Usually a host:port:sid or :service_name connect string is needed for the jdbc client, most oracle network connects just reference a tnsalias and the oracle client, via tnsnames.ora, or possibly an oracle naming service on your network resolves the alias to its host:port:<sid|service_name> particulars.