Java JTable get column sort key

import java.util.ArrayList;
import java.util.List;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.RowSorter;
import javax.swing.RowSorter.SortKey;
import javax.swing.table.AbstractTableModel;
import javax.swing.table.TableColumn;
import javax.swing.table.TableModel;

public class Main extends JPanel {
   public static void main(String[] args) {
      JFrame f = new JFrame("JTable");
      f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      f.add(new Main());
      f.pack();//  w  ww . j  a v  a  2  s. co m
      f.setVisible(true);
   }

   public Main() {
      TableModel dataModel = new MyTableModel();
      JTable table = new JTable(dataModel);

      SortKey key = getSortKey(table,0);
      System.out.println(key);

      JScrollPane jsp = new JScrollPane(table);
      this.add(jsp);
   }

   public static SortKey getSortKey(JTable table, int column) {
      RowSorter rowSorter = table.getRowSorter();
      if (rowSorter == null) {
         return null;
      }

      List sortedColumns = rowSorter.getSortKeys();
      if (!sortedColumns.isEmpty()) {
         return (SortKey) sortedColumns.get(0);
      }
      return null;
   }
}

class MyTableModel extends AbstractTableModel {

   @Override
   public int getRowCount() {
      return 30;
   }

   @Override
   public String getColumnName(int i) {
      return "" + i;
   }

   @Override
   public int getColumnCount() {
      return 3;
   }

   @Override
   public Object getValueAt(int row, int col) {
      return Math.pow(row, col + 1);
   }

   @Override
   public Class<?> getColumnClass(int col) {
      return getValueAt(0, col).getClass();
   }
}