Oracle Berkeley Database Java Edition

 Oracle Berkeley DB Java Edition is a open source, embeddable,
 transactional storage engine written entirely in Java. Like Oracle
 Berkeley DB, Oracle Berkeley DB Java Edition executes in the address
 space of the application, without the overhead of client/server
 communication. It stores data in the application's native format, so
 no runtime data translation is required. It provides an easy-to-use,
 programmatic interface, allowing developers to store and retrieve
 information quickly, simply and reliably.