HyperSQL

100% Java Database

HSQLDB (HyperSQL DataBase) is an SQL relational database engine written in Java. It has a JDBC driver and supports nearly full ANSI-92 SQL (BNF tree format) plus many SQL:2008 enhancements. It offers a small, fast database engine which offers in-memory and disk-based tables and supports embedded and server modes. Additionally, it includes tools such as a command line SQL tool and GUI query tools. http://hsqldb.org/