use case for extending enum, but this is not possible in java

Hi,

I have found a need to extend enum, but this is not possible in java.
Take a look at the situation:

In an application, there is an enum ListCommand that enumerates the
commands a user may execute on list entries:

public enum ListCommand
{
  OPEN,
  EDIT,
  DELETE;
}

There is an interface that uses this enum:

public interface ListCommandProcessor
{
  void onListCommand (ListCommand cmd);
}

And there is a generic Listing class that is used to show customized
lists in the GUI and which uses the above interface:

public class Listing<T>
{
  ...
  ListCommandProcessor processor;
  ...
}

So far, so good.

Now I am making a cut: The generic class Listing<T> should be moved into
a generic java library, so that it can be used by different
applications. So I also need to move the interface ListCommandProcesor
into this library, and this would implicate that I also move the enum
ListCommand into the library. But the enum ListCommand ist application
specific. If I move it to the library, it must be extendable somehow. If
there were no limitations in the java language, I would separate the
concerns of library and application like this:

--- library:

public enum ListCommand
{
  // empty at library level
}

public interface ListCommandProcessor
{
  void onListCommand (ListCommand cmd);
}

--- application:

public enum AppListCommand extends ListCommand
{
  OPEN,
  CLOSE,
  SOMETHINGSPECIAL;
}

public class MyApp extends ListCommandProcessor
{
  ...
  Listing<XYZ> listing = new Listing<XYZ> ();
  listing.setProcessor (this);

  public void onListCommand (ListCommand cmd)
  {
   AppListCommand c = (AppListCommand) cmd;

   switch (c)
   {
    ...
   }
  }
}

This would be my solution, but it is not possible in java to extend
enums. But I need to make a cut somewhere in order to move Listing<T>
into the generic library. The only solution I can imagine is to change

    onListCommand (ListCommand cmd);

into

    onListCommand (int cmd);

But then I would loose the beautiful type binding and I will soon find
myself defining list commands like it was done in the 90's in C:

    public static final int CMD_OPEN = 1;
    public static final int CMD_EDIT = 2;
    public static final int CMD_DELETE = 3;
    public static final int CMD_SOMETHINGSPECIAL = 55;

I know that this would be a way out, but I want to make sure that there
is no better solution.

How would you do this?

Thank you,
Laura