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();
}
}