HSQLDB is a relational database written in Java.
It is used
HSQLDB stores data in local files
Each HyperSQL database is called a catalog
file: stored in filesystem files
For example, the database named “test” consists of the following files:
res: stored in a Java resource, such as a Jar and always read-only
compile("org.hsqldb:hsqldb:2.5.0")