protected void clearCase(int i)
    {
        try
        {
            myLemma.clearCase(i);
            myCases.remove(i);
            myMessage.setText("Case #" + (i + 1) + " deleted.");
            refresh();
        }
        catch(ArrayIndexOutOfBoundsException e)
        {
            /* 
             * This should not happen because the button should be disabled
             * if there is no selection.
             */
            myMessage.setText("Please select a case to clear.");
        }
        
    }