Handling Changes to a List Component
List data events are fired by a ListModel whenever one or more items are changed, added, or removed. 

 
 JList list = new JList(new DefaultListModel());
 list.getModel().addListDataListener(
   new MyListDataListener());
     
 class MyListDataListener implements ListDataListener {
     public void contentsChanged(ListDataEvent evt) {
         // A non-contiguous set of items were added,
           // removed, or modified.
         ListModel model = (ListModel)evt.getSource();
         // The next tow lines should be in one line
         for (int i=evt.getIndex0(); i<=evt.getIndex1();
            i++) {
             process(model.getElementAt(i));
         }
     }
         
     public void intervalAdded(ListDataEvent evt) {
         // The items between evt.getIndex0() and
           // evt.getIndex1(), inclusive, were added.
         ListModel model = (ListModel)evt.getSource();
         for (int i=evt.getIndex0();
            i<=evt.getIndex1(); i++) {
             process(model.getElementAt(i));
         }
     }
     public void intervalRemoved(ListDataEvent evt) {
         // The items between evt.getIndex0() 
           // and evt.getIndex1(), inclusive,
             // have been removed.
     }
 }