培训老师给小弟我们做的一个聊天小程序，大家看看好不

import java.util.*;import java.net.*;import java.io.*;public class Server{    public static final int port=10000;    public static final Vector users=new Vector();    public static void main(String args[]){        ServerSocket server=null;        try{            server=new ServerSocket(port);            System.out.println("Server start up on port :"+port);            while(true){                Socket s=server.accept();                User user=new User(s);                user.start();            }                    }catch(Exception e){            e.printStackTrace();        }finally{            if(server!=null&&!server.isClosed()){                try{server.close();}catch(Exception e){}            }            }    }}class User extends Thread{    private Socket s;    private String userName;    private InetAddress ip;    public User(Socket s){        this.s=s;    }    public void run(){        try{            InputStream input=s.getInputStream();            OutputStream output=s.getOutputStream();            BufferedReader buf=new                 BufferedReader(new                 InputStreamReader(input));            PrintWriter pw=new             PrintWriter(new OutputStreamWriter(output),true);                        pw.println("welcome u ,enter your name :");            userName=buf.readLine();            Server.users.add(this);            sendAll(userName+" has join us ");;            long t=0;            while(true){                String line=buf.readLine();                long s=System.currentTimeMillis();                if((s-t)/1000<3){                    pw.println("flush denied ");                    continue;                }                t=s;                    if(line==null||line.trim().length()==0){                pw.println("flush denied ");                continue;                }                if(line.equals("bye")){                    sendAll(userName+" leave us ");                    Server.users.remove(this);                        break;                            }                sendAll(userName+" said :"+line);            }                }catch(Exception e){            //e.printStackTrace();        }finally{            if(s!=null)try{s.close();}catch(Exception e){}        }    }    public  synchronized void sendMessage(String message){        try{            PrintWriter pw=new             PrintWriter(new OutputStreamWriter(            s.getOutputStream()));            pw.println(message);            pw.flush();        }catch(Exception e){}    }    public void sendAll(String message){        Iterator it=Server.users.iterator();        while(it.hasNext()){            User user=(User)it.next();            user.sendMessage(message);        }    }}