If it is not explicitly told in following recipe, setting up services are described for Ubuntu 20.04 server, but applications are described for Xubuntu 20.04 workstation. If you use different Ubuntu version or Linux distribution, settings as well as content, names and places of configuration files may be different!
Got it.

Extra 5. JSON

  1. Look for more information about popular JSON implementation in Java
  2. Look at some examples how to use this library

  3. Add following dependency in <dependencies> element of pom.xml file:

    <!-- JSON -->
    <dependency>
    <groupId>org.json</groupId>
    <artifactId>json</artifactId>
    <version>20180813</version>
    </dependency>

  4. Regenerate project files for eclipse with command in your project:

    mvn eclipse:eclipse

    and refresh project in Eclipse

  5. Investigate jtm.extra05 package
  6. Implement classes Car and JsonCars  to pass unit tests.