Preventing multiple instances of an application to start

Hello, I had the problem that I did not want multiple instances of my
application to start. I would like instead to have the command line
parameters (file paths in my case) of a second starting instance to be
forwarded to the first already running app (eg. if someone double-clicks
on an associated file type).
Here is the solution I came up with (posting it for future reference).
Any comments/corrections are welcome (this is my first try at RMI).

Phil

-- RemoteContactInterface.java --
import java.io.File;
import java.rmi.Remote;
import java.rmi.RemoteException;
public interface RemoteContactInterface extends Remote {
  void loadFile(File f) throws RemoteException;
}

-- MyMainClass.java --
import java.io.File;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;

public class MyMainClass extends JFrame implements RemoteContactInterface {

  MyMainClass(){
// start RMI server
   try {
    int PORT = 1099;
    LocateRegistry.createRegistry(PORT);
    RemoteContactInterface stub =
(RemoteContactInterface)UnicastRemoteObject.exportObject(this, PORT);
    Registry registry = LocateRegistry.getRegistry();
    registry.bind("myClassID", stub);
    System.out.println("Server ready");
   } catch (Exception e) {
    System.err.println("RMI Server exception: " + e.toString());
    e.printStackTrace();
   }

   setDefaultCloseOperation(EXIT_ON_CLOSE);
   this.getContentPane().add(new JLabel("Hello World"));
   pack();
   setVisible(true);

  }

  public static void main(String args[]) {
   try {
    Registry registry = LocateRegistry.getRegistry(null);
    RemoteContactInterface stub = (RemoteContactInterface)
registry.lookup("myClassID");
    for(String s: args){
     File f = new File(s);
     stub.loadFile(f);
    }
    System.out.println("App already running");
    System.exit(0);
   } catch (Exception e) {
    // if exception is thrown, no other process already exists
    // go on with normal loading
   }

   SwingUtilities.invokeLater(new Runnable() {
    public void run() {
     MyMainClass myClass = new MyMainClass();
    }
   });

  }

  public void loadFile(File f) throws RemoteException {
   // load the file here;
  }
}