I know of at least three databases written in Java: HSQLDB: https://en.m.wikipedia.org/wiki/HSQLDB https://en.m.wikipedia.org/wiki/HSQLDB H2: https://en.m.w

I know of at least three databases written in Java: HSQLDB: https://en.m.wikipedia.org/wiki/HSQLDB https://en.m.wikipedia.org/wiki/HSQLDB H2: https://en.m.wikipedia.org/wiki/H2_(database) https://en.m.wikipedia.org/wiki/H2_(database) PointBase: https://en.m.wikipedia.org/wiki/PointBase https://en.m.wikipedia.org/wiki/PointBase I have briefly used either one of the first two, I think it was HSQLDB, with Java, years ago. PointBase was created by Bruce Scott, a co-founder of Oracle, and a few others, including an architect of Sybase. This was in the early days of Java. All three still seem to exist, according to the links above.