swing 事件的有关问题

swing 事件的问题
//创建的是单击Button   打印出下拉列表选中项
import   javax.swing.*;
import   java.awt.*;
import   java.awt.event.*;
public   class   StudyEvent   extends   JPanel{
private   JComboBox   jcb;
private   JButton   jb;

StudyEvent(){
this.jb=new   JButton( "打印 ");
this.jcb=new   JComboBox();
this.jcb.addItem( "北京 ");
this.jcb.addItem( "上海 ");
this.jcb.addItem( "大连 ");
this.jcb.addItem( "哈尔滨 ");
this.add(this.jb);
this.add(this.jcb);
getEvent();
}
public   void   getEvent(){
this.jb.addActionListener(new   StudyListener(this));
}
public   void   getPrint(){
                                //我想打印出下拉列表选中的项的文字例如北京，应该                                               怎么写
System.out.println(this.jcb.getActionCommand());
}
}
class   StudyListener   implements   ActionListener{
private   StudyEvent   se;
StudyListener(StudyEvent   se){
this.se=se;
}
public   void   actionPerformed(ActionEvent   arg0)   {
se.getPrint();
}
}
class   StudyEventDemo{
public   static   void   main(String   args[]){
JFrame   frame=new   JFrame( "打印下拉列表文字 ");
frame.setSize(300,300);
frame.add(new   StudyEvent());
frame.setVisible(true);
}
}

------解决方案--------------------
public void getPrint(){
System.out.println(this.jcb.getSelectedItem());
}
把类StudyEventDemo写作public的
StudyEvent的public不要