通信记录系统(2)

import java.awt.*;import java.awt.event.*;import javax.swing.*;import javax.swing.JOptionPane.*;import java.sql.*;

public class MainFrame extends JFrame {   public MainFrame(){     setTitle("通讯纪录本：");     setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);     Container contentPane=getContentPane();     //获得屏幕大小     Toolkit kit=Toolkit.getDefaultToolkit();     Dimension screenSize=kit.getScreenSize();     int screenWidth=screenSize.width;     int screenHeight=screenSize.height;     setLocation(screenWidth/2-DEFAULT_WIDTH/2,screenHeight/2-DEFAULT_HEIGHT/2);     ///     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);     //添加菜单     JMenuBar jMenuBar=new JMenuBar();     JMenu jMenuFile=new JMenu("文件");     JMenuItem jMIOpen=new JMenuItem("打开");     jMenuFile.add(jMIOpen);     jMenuBar.add(jMenuFile);     setJMenuBar(jMenuBar);     ///     //添加窗体控件on right     JButton jBadd=new JButton("添加");     JButton jBchange=new JButton("修改");     JButton jBdelete=new JButton("删除");     bright=Box.createVerticalBox();     bright.add(jBadd);     bright.add(Box.createVerticalGlue());     bright.add(jBchange);     bright.add(Box.createVerticalGlue());     bright.add(jBdelete);     //  jPanel1     JPanel jPanel1=new JPanel(new GridLayout(5,2));     JLabel jLname=new JLabel("姓　　名：",JLabel.RIGHT);     jLname.setBorder(BorderFactory.createLineBorder(Color.black));

/这里怎么不能改变JLabel的大小呢?(只能放大,不能缩小)     jLname.setPreferredSize(new Dimension(50,20));     JTextField jTname=new JTextField(6);     JLabel jLtelephone=new JLabel("电　　话：",JLabel.RIGHT);     jLtelephone.setPreferredSize(new Dimension(30,20));     JTextField jTtelephone=new JTextField(10);     JLabel jLemail=new JLabel("电子邮件：",JLabel.RIGHT);     jLemail.setPreferredSize(new Dimension(100,25));     JTextField jTemail=new JTextField(10);     JLabel jLbirthday=new JLabel("生　　日：",JLabel.RIGHT);     jLbirthday.setPreferredSize(new Dimension(30,20));     JTextField jTbirthday=new JTextField(12);     jPanel1.add(jLname);     jPanel1.add(jTname);     jPanel1.add(jLtelephone);     jPanel1.add(jTtelephone);     jPanel1.add(jLemail);     jPanel1.add(jTemail);     jPanel1.add(jLbirthday);     jPanel1.add(jTbirthday);          /   jPanel2     JPanel jPanel2=new JPanel();     JLabel jLimage=new JLabel("kkkkkkk");     jLimage.setPreferredSize(new Dimension(200,140));     jLimage.setBorder(BorderFactory.createLineBorder(Color.black));     //jLimage.setBackground(Color.blue);     jPanel2.add(jLimage);     /   jPleft     jPleft=new JPanel(new FlowLayout());     //     JPanel jPtop=new JPanel(new FlowLayout());     jPtop.setBorder(BorderFactory.createLineBorder(Color.blue));     jPtop.add(jPanel1);     jPtop.add(Box.createRigidArea(new Dimension(70,100)));     jPtop.add(jPanel2);     jPleft.add(jPtop);     /          contentPane.add(bright,BorderLayout.WEST);     contentPane.add(jPleft,BorderLayout.CENTER);   }   public static void main(String[] args){     JFrame jFrame=new MainFrame();     jFrame.show();   }   private int DEFAULT_WIDTH=600;   private int DEFAULT_HEIGHT=400;   private Box bright;   private JPanel jPcenter;   private JPanel jPleft;}