No anonymous inner classes?

I'm trying to embed a groovy script into an application. The application 
has a Java interface that a class in the groovy script implements. There 
is another Java interface in the application called Command with method 
execute(); I want to be able to execute a command written in the groovy 
script by passing it to the java application, but I get an "Anonymous 
inner classes not yet supported Exception"

I tried making a normal inner class, but that seems to be not working 
either; are normal inner classes supported in groovy?

Basically, I have something like this:

Java interfaces:
public interface foo {
  foo1();
  foo2();
}
public interface Command {
  execute();
}

Groovy class:
class bar implements foo {
  foo1() {}
  foo2() {
    javaSingleton.instance().executeCommand(new Command() {
      public void execute() {
        foo3();
      }
    }
  }
  private void foo3() {
        //do some cool stuff
  }
}

The problem is I can't use the anonymous inner class. Is there a way to 
make a closure do what I want (ie: implement the Command() interface)? I 
don't really understand closures yet, so I'm not sure what they can and 
cannot do.  Is there another way around this problem?

I'll ask now; are regular inner classes supported in Groovy? if they 
are, I can use that. I'm just assuming they aren't because of problems I 
had, but perhaps I implemented it incorrectly.

thanks,
Dusty