Terminate Java RMI server application

I have set up a client/server project using Java RMI. Below I show parts of the implementation. I launch the server using

ProcessBuilder processBuilder = new ProcessBuilder("cmd", "/C", "start /B java -jar myServer.jar --start);
this.myProcess = processBuilder.start();

I have added a main method to the server which handles the command line call. The server starts and runs perfectly. The client is able to connect and perform as I expect it to.

My problems arise when I try to kill the server. This needs to be done from outside. The object which previously started the process is not available anymore. To actually stop the server, the main method of the server class calls a stop method (see below). This method now kills the RMI but it does not the least stop the JVM from running. The process is still available and needs to be killed from the task manager (on Windows).

Do I miss some fact in my implementation that yields this behavior. Why does the process not stop running?

public class MyServer {

    // ...

    public void startServer() throws RemoteException {

        // the RMI registry
        Registry registry;

        try {
            // find the registry
            registry = LocateRegistry.createRegistry(portRMI);
        } catch (Exception e) {
            // if the registry does not yet exist, try to create a new registry
            // entry or use an existing one
            registry = LocateRegistry.getRegistry(MyConstants.HOST_NAME, portRMI);
        }

        // create the object
        servantObject = new MyServant();

        // bind the object to the server
        registry.rebind(MyConstants.SERVER_NAME, servantObject);
    }

    public void stopServer() throws RemoteException {

        try {
            // access the service
            Registry rmiRegistry = LocateRegistry.getRegistry(MyConstants.HOST_NAME, portRMI);
            MyService myService = (MyService) rmiRegistry.lookup(MyConstants.SERVER_NAME);

            rmiRegistry.unbind(MyConstants.SERVER_NAME);

            // get rid of the service object
            UnicastRemoteObject.unexportObject(myService, true);

            // get rid of the rmi registry
            UnicastRemoteObject.unexportObject(rmiRegistry, true);

        } catch (NoSuchObjectException e) {
            // ...
        } catch (NotBoundException e) {
            // ...
        }
    }

    public static void main(String[] args) {
        // handle arguments and call either startServer or stopServer
    }
}

public class MyServant extends UnicastRemoteObject implements MyService {
    // ...
}

public interface MyService extends Remote {
    // ...
}