You may find the free MaxMind stuff (called
MaxMind Lite) easier to get started with. The Java library is at
https://github.com/maxmind/GeoIP2-java, and the data (updated monthly) is at
http://dev.maxmind.com/geoip/geoip2/geolite2/. There are two data sets, one that includes just country information, and another that includes country and city information.