Sorting rows by columns in JTable

please read tutorial about JTable that’s contains TableRowSorter example,

your answer is these codes lines, set column Class correctly

public Class getColumnClass(int c) {
   return getValueAt(0, c).getClass();
}

// or could be in most cases hardcoded, and I'm using that too

            @Override
            public Class<?> getColumnClass(int colNum) {
                switch (colNum) {
                    case 0:
                        return Integer.class;
                    case 1:
                        return Double.class;
                    case 2:
                        return Long.class;
                    case 3:
                        return Boolean.class;
                    case 4:
                        return String.class;
                    case 5:
                        return Icon.class;
                    /*case 6:
                    return Double.class;
                    case 7:
                    return Double.class;
                    case 8:
                    return Double.class;*/
                    default:
                        return String.class;
                }
            }