GeoLite2 Free Downloadable Databases « Maxmind Developer Site

http://dev.maxmind.com/geoip/geoip2/geolite2/

GeoLite2 databases are free IP geolocation databases comparable to, but less accurate than, MaxMind’s GeoIP2 databases. GeoLite2 databases are updated on the first Tuesday of each month.

IPアドレスと国名、街の名前、経度・緯度のデータベース。

GeoLite Legacy Downloadable Databases « Maxmind Developer Site

http://dev.maxmind.com/geoip/legacy/geolite/

The GeoLite databases are our free IP geolocation databases. They are updated on the first Tuesday of each month. These databases are offered in the same binary and csv formats as our subscription databases. Any code which can read the subscription databases can also read the GeoLite databases.

IPアドレスと国名、街の名前、経度・緯度、AS番号のデータベース。

Huffman coding (Java) | Project Nayuki

http://www.nayuki.io/page/huffman-coding-java

Huffman coding (Java)

This project is an open-source reference implementation of Huffman coding in Java. The code is intended to be used for study, and as a solid basis for modification and extension. As such, it is optimized for clear logic and low complexity, not speed/memory/performance.