java下拉框，滚动条

package com.soft.test;

/**
 * 下拉列表、下拉框、滚动条的使用
 */

import javax.swing.*;
import java.awt.*;
public class Dem5 extends JFrame {


 private JPanel jp1, jp2;
 private JLabel jlb1, jlb2;
 private JComboBox jb1;
 private JList jl;
 private JScrollPane jsp;
 
 public Dem5() {
  jp1 = new JPanel();
  jp2 = new JPanel();
  jlb1 = new JLabel("籍贯");
  jlb2 = new JLabel("旅游地点");
  
  
  String []jz = {"南昌","赣州","吉安","新余","鹰潭","景德镇","抚州"};
  jb1 = new JComboBox(jz);
  String []ly = {"三清山","将军园","龙虎山","庐山","腾王阁"};
  
  jl = new JList(ly);
  jsp = new JScrollPane(jl);
  jl.setVisibleRowCount(3);
  
  this.setLayout(new GridLayout(3, 1));
  
  jp1.add(jlb1);
  jp1.add(jb1);
  jp2.add(jlb2);
  jp2.add(jsp);
  this.add(jp1);
  this.add(jp2);
  this.setSize(300,300);
  this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  this.setLocation(300,300);
  this.setVisible(true);
  this.setResizable(false);  
 }
 
 public static void main(String args[]) {
  
  Dem5 dem5 = new Dem5();
 }
}