@Override
    public Class getColumnClass(int column) {
        Class returnValue;
        if ((column >= 0) && (column < getColumnCount())) {
            if (getValueAt(0, column) == null) {
                return Object.class;
            }
            returnValue = getValueAt(0, column).getClass();
        } else {
            returnValue = Object.class;
        }
        return returnValue;
    }