JScrollPane竖直滚动条的监控问题

我想得到的效果是当我去拉竖直滚动条的时候，才去更改lbl的值，但是这里一开始运行程序就已经把lbl的值改成"你滚动了垂直滚动条111！"
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.AdjustmentEvent;
import java.awt.event.AdjustmentListener;
import java.awt.event.ItemEvent;import javax.swing.*;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;class Sample07JList extends JFrame{
JLabel lbl = new JLabel("OK");
JScrollBar bar;
JList moviestars;
JLabel lblTitle;
JScrollPane scrollObj;
public Sample07JList(){
String stars[] = {"安东尼奥.班德拉斯","来昂纳多.迪卡普尼奥", "桑德拉.布洛克","休.格兰特","朱莉亚.罗伯茨","dddddd","dddddd","dddddd"};
JPanel pnl=new JPanel();
lblTitle = new JLabel("您最喜欢哪位电影明星呢？");

moviestars = new JList(stars);
moviestars.setFixedCellWidth(130);
moviestars.setVisibleRowCount(4);
scrollObj = new JScrollPane(moviestars,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                    JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
 bar = scrollObj.getVerticalScrollBar();
bar.addAdjustmentListener(new ScrollEvent());
pnl.add(lblTitle);
pnl.add(scrollObj);
pnl.add(lbl);
getContentPane().add(pnl);
setSize(500,500);
setVisible(true);
}
class ScrollEvent implements AdjustmentListener { public void adjustmentValueChanged(AdjustmentEvent e) {
   
     lbl.setText("你滚动了垂直滚动条111!");
}

} public static void main(String args[]){
new Sample07JList();

}
}