程序代码：

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;
import *;

import import import import public class FTPClient extends JFrame {

    private static final String setText = null;   
    /**
     * 客户端框架
     * FlowLayout 布局管理器
     */
    JPanel pn = new JPanel();
    JPanel pn1 = new JPanel(new FlowLayout(0));
    JPanel pn2 = new JPanel(new FlowLayout(0));
    JPanel pn3 = new JPanel(new FlowLayout(0));
    JPanel pn4 = new JPanel(new FlowLayout(0));
    JPanel pn5 = new JPanel(new GridLayout(1,2)); 

    JPanel pc = new JPanel();
    JPanel ps = new JPanel();
    JLabel labelHost = new JLabel();
    JTextField textFieldHost = new JTextField(18);
    JLabel labelPort = new JLabel();
    JTextField textFieldPort = new JTextField(4);
    JButton buttonLink = new JButton();   //连接按钮
    JLabel labelUser = new JLabel();
    JTextField textFieldUser = new JTextField(8);  //用户名
    JLabel  labelPassword = new JLabel();
    TextField textFieldPassword = new TextField(8);  //密码
    JButton buttonDisconnect = new JButton();   //断开连接
    JLabel labelFileShow = new JLabel();
    JLabel labelclient = new JLabel();
    JLabel labelserver = new JLabel();
    JLabel labelstatus = new JLabel();
   
    List listclient = new List(5);   // 创建一个用指定可视行数初始化的新滚动列表
    List listServer = new List(5);
    PopupMenu pmc1 = new PopupMenu();  //组件的指定位置上动态弹出的菜单
    MenuItem upload = new MenuItem("上传");
    MenuItem view = new MenuItem("浏览");
    PopupMenu pms = new PopupMenu();
    MenuItem download = new MenuItem("下载");
    MenuItem reflash = new MenuItem("刷新");
   
   
    int port = 21;
    String dir ="";
   
    TelnetInputStream is = null;
    TelnetOutputStream os = null;
    FtpClient ftp = new FtpClient();
    /**
     *  构造方法
     */
    public FTPClient() {
        setSize(new Dimension(480,500));
        enableEvents(AWTEvent.WINDOW_EVENT_MASK);
        try {
            jbInit();
        }
        catch(Exception e){
            e.printStackTrace();
        }
    }

    private void jbInit()throws Exception {
        add(pn,BorderLayout.NORTH);
        add(pc,BorderLayout.CENTER);
        add(ps,BorderLayout.SOUTH);
        pn.setLayout(new GridLayout(5,1));
        pn.add(pn1);
        pn.add(pn2);
        pn.add(pn3);
        pn.add(pn4);
        pn.add(pn5);
        pc.setLayout(new GridLayout(1,2));
        pc.add(listclient);
        listclient.add("c");
        listclient.add("c");
        listclient.add("c");
        listclient.add("c");
        listclient.add("c");
        pc.add(listServer);
        listServer.add("s");
        listServer.add("s");
        listServer.add("s");
        listServer.add("s");
        listServer.add("s");
       
        pn1.add(labelHost);
        pn1.add(textFieldHost);
        pn1.add(buttonLink);
        pn3.add(labelPort);
        pn3.add(textFieldPort);
        pn2.add(labelUser);
        pn2.add(textFieldUser);
        pn2.add(labelPassword);
        pn2.add(textFieldPassword);
        pn2.add(buttonDisconnect);
        pn4.add(labelFileShow);
        pn5.add(labelclient);
        pn5.add(labelserver);
        ps.add(labelstatus);
       
        labelHost.setText("主机名");
        labelPort.setText("端口");
        labelUser.setText("用户名");
        labelPassword.setText("密码");
        textFieldPassword.setEchoChar('*');
        labelclient.setText("客户端");
        labelserver.setText("服务器端");
       
        pmc1.add(upload);
        pmc1.add(view);
        pms.add(download);
        pms.add(reflash);
        listclient.add(pmc1);
       
        listclient.addMouseListener( new MouseAdapter() {
            public void mouseClicked(MouseEvent me) {            //  鼠标按键在组件上单击时调用。
                if(SwingUtilities.isRightMouseButton(me)) {
                    pmc1.show(listclient,me.getX(),me.getY());
                }
            }
        });
        listServer.add(pms);
        listServer.addMouseListener(new MouseAdapter() {
            public void mouseClicked(MouseEvent me){
                if(SwingUtilities.isRightMouseButton(me)) {     //如果鼠标事件指定右边鼠标按键，则返回 true。
                    pms.show(listServer, me.getX(), me.getY());
                }
            }
        });
       
        buttonLink.setLabel("连接");
        buttonLink.addActionListener(new java.awt.event.ActionListener() {
             public void  actionPerformed(ActionEvent e) {
                buttonLink_ActionPerform(e);
             }
        });
        buttonLink.setEnabled(true);
       
        buttonDisconnect.setLabel("断开");
        buttonDisconnect.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                buttonDisconnect_ActionPerFormed(e);
            }
        });
        buttonDisconnect.setEnabled(false);
        labelFileShow.setText("目录列表");
        upload.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                upload_actionPerformed(e);      //监听器,调用处理程序
            }

        });
        view.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                view_actionPerformed(e);
            }
        });
        download.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                download_actionPerformed(e);
            }
        });
        reflash.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                reflash_actionPerformed(e);
            }
        });
       
       
    }
    /**
     *
     * 响应连接按钮事件，连接到服务器
     */
    void buttonLink_ActionPerform(ActionEvent e) {
       
        System.out.println("连接中。。。。。!");
       
        String hostname = textFieldHost.getText();
        labelstatus.setText("连接中，请等待。。。");
        try {
           
            ftp.openServer(hostname,port);
            ftp.login(textFieldUser.getText(), textFieldPassword.getText());
            ftp.binary();
            ftp.cd(dir);
            showFileContents();
            labelstatus.setText("连接主机："+textFieldHost.getText()+"成功");
            buttonDisconnect.setEnabled(true);
        }
        catch(FtpLoginException e0) {
            labelstatus.setText("用户名、密码错误！");
            e0.printStackTrace();
        }
        catch(IOException e1) {
            labelstatus.setText(hostname+"连接失败！！！");
            e1.printStackTrace();
        }
        catch(SecurityException e2) {
            labelstatus.setText("没有权限!!");
            e2.printStackTrace();
        }
        if(hostname.equals(""))
            labelstatus.setText("FTP服务器不能为空!!!");
        else if(textFieldUser.getText().equals(""))
            labelstatus.setText("用户名不能为空！！！");
        else if(textFieldPassword.getText().equals(""))
            labelstatus.setText("密码不能为空！！！") ;
    }

    void buttonDisconnect_ActionPerFormed(ActionEvent e) {

        try {
            ftp.closeServer(); //关闭客户端与服务器的连接
            labelstatus.setText("与服务器已断开....");
        } catch (IOException e1) {
            System.out.println("Error" + e1);
            e1.printStackTrace();
        }
        buttonLink.setEnabled(true);
        buttonDisconnect.setEnabled(false);
    }
    

    protected void reflash_actionPerformed(ActionEvent e) {
        System.out.println("view!");
       
       
    }

    void download_actionPerformed(ActionEvent e) {
       
        System.out.println("down!");
        upload.setEnabled(false);
        TelnetInputStream fget = null;
        RandomAccessFile  getfile = null ;
        try {
            String fileName = "test.jpg";
            String fileUrl = "E:\test.jpg";
            char ch;
            if(!new File("E:/FTP共享/").isDirectory()) {
                new File("E:/FTP共享/").mkdir();
            }
           
            String keepLocate = "E:/FTP共享/"+fileName;
            fget = ftp.get("fileUrl");
            DataInputStream puts = new DataInputStream(fget);
           
            File fi = new File(keepLocate);
            RandomAccessFile  getFile = new RandomAccessFile(fi,"rw");
            getFile.seek(0);   //将指针指向最前端
            while((ch = (char) puts.read()) >= 0) {
                getFile.write(ch);
            }
           
            System.out.print("------4" + "finish and success" );
        }
        catch (Exception e1) {
            e1.printStackTrace(System.out);
//            throws new Exception(e.getMessage());
           
        }finally {
            try {
                fget.close();
            }catch(Exception e2) {
                System.out.print("-------1" + "" +e);
            }
            try {
               
                getfile.close();
            }catch(Exception e3) {
                System.out.println("-----2" + e);
            }
            try {
                ftp.closeServer();
            }catch(Exception e4) {
                System.out.println("------3" + "" +e);
            }
            System.out.println("--------5" + "finish and success");
        }
       
    /*    String outfile = null;String file = null;
        try {
           
            RandomAccessFile rFile = new RandomAccessFile(outfile,"rw");   //对随机访问文件的读写和写入
            rFile.seek(0);    // 设置到此文件开头测量到的文件指针偏移量，在该位置发生下一个读取或写入操作。
           
            TelnetInputStream tInput =  ftp.get(file);            //.get(file);
            DataInputStream dInput = new DataInputStream(tInput);
            while((ch = dInput.read())>=0) {
                rFile.write(ch);
            }
            dInput.close();
            rFile.close();
        }
        catch(IOException e1) {
            System.out.println("Error" + e1);
            e1.printStackTrace();
        }*/ 
    }

    protected void view_actionPerformed(ActionEvent e) {
        System.out.println("view");
    }
   
        void showFileContents() {
           
            FtpClient ftp = new FtpClient();
            int ch;
            StringBuffer buf = new StringBuffer();
            try {
                FilterInputStream inStream = ftp.list(); //获取服务器当前目录下所有的文件盒目录的输入
                while((ch=inStream.read())>=0) {   //读取数据
                    buf.append((char)ch);      //保存数据到缓冲区
                }
//                listServer.append(buf.toString());
                buf.append(buf.toString());
                inStream.close();
            }
            catch(Exception e) {
                System.out.println("Error" + e);
            }
           
//        }
    }
       
       
        private void upload_actionPerformed(ActionEvent e) {
           
            String infile = null;
            int i = infile.lastIndexOf("//");
            String outfile = infile.substring(i+1,infile.length());
            labelstatus.setText("infile[" +infile + "]");
            labelstatus.setText("outfile[" + outfile + "]lastindex[" + i+ "]");
            try {
               
                TelnetOutputStream os =ftp.put(outfile);
                File file_in = new File(infile);
                FileInputStream is = new FileInputStream(file_in);
                byte[] bytes = new byte[1024];
                int c;
                while((c=is.read(bytes))!=-1){
                    os.write(bytes,0,c);
                    labelstatus.setText("bytes[" + bytes + "]");
                }
                is.close();
                os.close();
            }
            catch(IOException e1){
                e1.printStackTrace();
            }
        }

        

    public static void main(String[] args) {
        System.out.println("Starting FTPClient!");
        FTPClient mainFrame = new FTPClient();
        mainFrame.setVisible(true);
    }