swing jlist, how to print out once instread of twice when selection changed

Hi,

I got two questions for the following codes

import javax.swing.*;

import java.awt.*;
import java.awt.event.*;

public class Test {

     public static final void main( String args[] ) throws Exception {

         JFrame frame = new JFrame("Test");
         frame.setDefaultCloseOperation( JFrame.DISPOSE_ON_CLOSE );

     String[] items = {"A", "B", "C", "D"};

         JList list = new JList(items);

         list.addListSelectionListener(new
javax.swing.event.ListSelectionListener(){
          public void valueChanged(javax.swing.event.ListSelectionEvent e)
            {
                int[] k = ((JList)e.getSource()).getSelectedIndices();

                for (int i = 0; i < k.length; i++)
                    System.out.println(k[i]);

            }
         }) ;

         JScrollPane scrollingList = new JScrollPane(list);

         frame.setContentPane( scrollingList );
     frame.setSize(300,150);
         frame.pack(); //line A
         frame.setVisible( true );

     }
}

1. why every time selection changed, print out twice, how to make it
print once?
2. with line A, the setSize() didn't apply, it seemed using default
size. why?

--
Thanks
John
Toronto