H2 is an embeddable RDBMS written in Java.
Java HTML PLSQL JavaScript CSS Batchfile Other
Latest commit efd50a4 Jan 18, 2017 @grandinj grandinj remove link to latest jar
we don't seem to be keeping this up to date anymore

README.md

Welcome to H2, the Java SQL database. Build Status

The main features of H2 are:

  1. Very fast, open source, JDBC API
  2. Embedded and server modes; in-memory databases
  3. Browser based Console application
  4. Small footprint: around 1.5 MB jar file size

More information: http://h2database.com

Features

H2 Derby HSQLDB MySQL PostgreSQL
Pure Java Yes Yes Yes No No
Memory Mode Yes Yes Yes No No
Encrypted Database Yes Yes Yes No No
ODBC Driver Yes No No Yes Yes
Fulltext Search Yes No No Yes Yes
Multi Version Concurrency Yes No Yes Yes Yes
Footprint (jar/dll size) ~1 MB ~2 MB ~1 MB ~4 MB ~6 MB