title: interface for only certain classes?
body: <p>Can you create an interface which can only be applied to certain classes and subclasses?</p>
  
  <p>If my interface is <strong>only</strong> added to <em>different</em> subclasses of JComponent, and I need to refer to both the methods of JComponent and my interface...  how should I do this?  Off the top of my head I can accomplish this by adding methods from JComponent to my interface.  </p>
  
  <p>This seems clumsy.  What is a better way to do this?</p>