Extending the Interface

Question

Suppose I create the following interface
package com.foo;
import javax.swing.ListModel;
public interface MyInterface extends ListModel
     public void bar();
}MyInterface then can be said to enforce the contract of "ListModel".
So when I use it for my GUI, it works.
MyInterface myint = new MyInterfaceImpl();
JList list = new JList();
list.setModel(myint);I understand that ComboBoxModel extends from ListModel. Given this, I use it for the interface
hoping to be able to use the implementation of the interface for the model of both JList and JComboBox.
public interface MyInterface extends ComboBoxModel
     public void bar();
MyInterface myint = new MyInterfaceImpl();
JComboBox box = new JComboBox();
box.setModel(myint);But I generate errors not only when I attempt to apply the updated interface to the model of the JList, but also when I apply it to the model of the JComboBox. But why? If the interface ComboBoxModel extends from the interface ListModel, why do problems arise?

Answer 1

Just to update...
I've managed to create a model that satisifies the model for both JList and JComboBox by using a class that extends DefaultComboBoxModel rather than extending the class DefaultListModel.
And I'm currently reviewing another thread relevant to the subject here..
http://forum.java.sun.com/thread.jsp?forum=54&thread=519806
I understand that the interface defines an "is a" relationship between the implementation and the interface (ie ArrayList is a List etc..) So I might assume that it is the same to say that a ComboBoxModel is a ListModel, though this relationship is one of extension. javax.swing.ComboBoxModel extends javax.swing.ListModel. But I am confused as to why the increased specificity would cause the code to generate errors. Surely I am not taking away from the interface..If the interface extends from a subclass of ListModel, doesn't it continue to extend from ListModel?
The error message when I extend from CombBoxModel rather than ListModel is something like ...
setModel(javax.swing.ListModel) in javax.swing.JList cannot be applied to com.foo.MyInterface
Thanks