An mdf file can be an old (JET based) Microsoft Access database file, so a JDBC driver for SQL Server, a totally different product, isn't going to help you much. Here on SO there are a couple of posts that explain how to use the JDBC-ODBC bridge to access Access databases via the ODBC driver detour, but since you specifically mention Linux that's not going to help you.
I see two possible (free) approaches:
- use the open source jackcess package that allows Java programs across platforms to open, read and write MS Access database
- transfer the content of the MSAccess database file to some database that has native Java drivers (that is, most of them that are not MS Access).
However, an mdf file could also be a SQLServer database, but using that database under Linux is also going to be quite tricky, as you'll need some edition of SQL Server to open it - see here for some details on how to "attach" such an mdf file to an installed instance of SQLServer - but to my knowledge there is no edition of SQL Server that runs under Linux. So, unless you can find some Windows machine to run SQLServer on, and then connect to it using the JDBC driver you have both options mentioned before may be valid alternatives (ie, option 1 = copy your data into an MSAccess file and access that file with jackcess or option 2, copy the data into some Linux-tolerant database with a decent JDBC driver and use that)