If a database connection is tried when MariaDB server is down, the JDBC driver returns following error information:

Error code:-1
SQL State:08
Message:Could not connect to address=(host=localhost)(port=3306)(type=master) : Connection refused (Connection refused)

I believe error code -1 is not a valid error code and not documented at https://mariadb.com/kb/en/library/mariadb-error-codes/. Further, SQL State is expected to be 5 characters but not sure if it is right to return 2 character major class of errors.

Above mentioned error information can be reproduced by running attached program as following:

java MariaDbInvErrorCodeBug org.mariadb.jdbc.Driver jdbc:mariadb://localhost:3306/bladb blauser blapasswd

Output displayed by the program is as following:
Error code:-1
SQL State:08
Message:Could not connect to address=(host=localhost)(port=3306)(type=master) : Connection refused (Connection refused)