protected Comparator getComparator(int column) {
   Class columnType = tableModel.getColumnClass(column);
   Comparator comparator = (Comparator) columnComparators.get(columnType);
   if (comparator != null) {
     return comparator;
   }
   if (Comparable.class.isAssignableFrom(columnType)) {
     return COMPARABLE_COMAPRATOR;
   }
   return LEXICAL_COMPARATOR;
 }
 public Class getColumnClass(int column) {
   return tableModel.getColumnClass(column);
 }
 public Class getColumnClass(int iColIndex) {
   return parentModel.getColumnClass(iColIndex);
 }