Hi Thomas, thanks for the quick reply.

From a usability point of view, I want the cell to look like a JComboBox
even when it's not in use, so the user knows which rows are dropdowns and
which are normal text entry.  But I think the renderer will be easy compared
to the editor.

Thanks, I got it working.  Here's the code.   Some of it seems really
sketchy though, especially the 'lastrow' business to remember which row is
being edited.  Is there a cleaner way to go about this?

private class MyCustomEditor extends DefaultCellEditor
   {
       // Internal array of editors.
       private Component[] editors = null;

       // Maintain a reference to the last selected row
       private int lastrow = -1;

       // This gets called immediately before getCellEditorValue(), below.
       public Component getTableCellEditorComponent(JTable table, Object
value, boolean isSelected, int row, int column)
       {
           lastrow=row;
           return editors[row];   // This works!
       }

       // Assume that lastrow is set immediately before this
       public Object getCellEditorValue()
       {
           Object o = null;

           if (editors[lastrow] instanceof JTextField)
           {
               o = ((JTextField)editors[lastrow]).getText();
           }
           else if (editors[lastrow] instanceof JComboBox)
           {
               o =
((JComboBox)editors[lastrow]).getSelectedItem().toString();
           }

           return o;
       }

       // Constructor
       public MyCustomEditor(int[] parameters, int rows)
       {
           super(new JTextField("dummy"));

           editors = new Component[rows];
           for (int i=0; i<rows; i++)
           {
               if ( parameters[i].isEnumeration() )
               {
                   editors[i]= new JComboBox(
parameters[i].getPossibleValues() );
               }
               else
               {
                   editors[i]= new JTextField();
               }
           }
       }
   }