code: private static int getSortPriority(JTable table, int column)
      {
          List<? extends SortKey> sortKeys = table.getRowSorter().getSortKeys();
          for (int i=0; i<sortKeys.size(); i++)
          {
              SortKey sortKey = sortKeys.get(i);
              if (sortKey.getColumn() == table.convertColumnIndexToModel(column))
              {
                  return i;                        
              }
          }
          return -1;
      }
docs: Returns the sort priority of the specified column in the given
  table, where 0 means the highest priority, and -1 means that
  the column is not sorted.
  
  @param table The table
  @param column The column
  @return The sort priority