给我一个代码基于TCP协议的聊天程序的设计与实现可注册用户java

好的，以下是一个基于TCP协议的聊天程序的设计与实现，同时支持用户注册和登陆的 Java 代码：

1. 服务器端代码：

import java.io.*;
import java.net.*;
import java.util.*;

public class ChatServer {
    private static final int PORT = 8888;
    private static Map<String, Socket> clients = new HashMap<String, Socket>();
    private static Map<String, String> users = new HashMap<String, String>();

    public static void main(String[] args) {
        ServerSocket serverSocket = null;
        try {
            serverSocket = new ServerSocket(PORT);
            System.out.println("Server started...");
            while (true) {
                Socket client = serverSocket.accept();
                System.out.println("Client connected: " + client.getInetAddress().getHostAddress());
                new ChatHandler(client).start();
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (serverSocket != null) {
                try {
                    serverSocket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public static synchronized boolean register(String username, String password) {
        if (users.containsKey(username)) {
            return false;
        } else {
            users.put(username, password);
            return true;
        }
    }

    private static class ChatHandler extends Thread {
        private Socket client;
        private String username;

        public ChatHandler(Socket client) {
            this.client = client;
        }

        @Override
        public void run() {
            try {
                BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
                PrintWriter out = new PrintWriter(client.getOutputStream(), true);

                out.println("Welcome to the chat server!");
                out.println("Please login or register.");

                while (true) {
                    String line = in.readLine();
                    if (line.startsWith("REGISTER")) {
                        String[] tokens = line.split("\\s+");
                        boolean success = register(tokens[1], tokens[2]);
                        if (success) {
                            out.println("REGISTERED");
                        } else {
                            out.println("REGISTER FAILED");
                        }
                    } else if (line.startsWith("LOGIN")) {
                        String[] tokens = line.split("\\s+");
                        if (users.containsKey(tokens[1]) && users.get(tokens[1]).equals(tokens[2])) {
                            username = tokens[1];
                            clients.put(username, client);
                            out.println("LOGIN SUCCESS");
                            break;
                        } else {
                            out.println("LOGIN FAILED");
                        }
                    } else {
                        out.println("Invalid command.");
                    }
                }

                out.println("Welcome, " + username + "!");

                BufferedReader consoleIn = new BufferedReader(new InputStreamReader(System.in));
                while (true) {
                    String input = consoleIn.readLine();
                    if (input.equalsIgnoreCase("quit")) {
                        out.println("QUIT");
                        break;
                    } else {
                        String[] tokens = input.split("\\s+", 2);
                        if (tokens.length == 2) {
                            Socket targetClient = clients.get(tokens[0]);
                            if (targetClient != null) {
                                PrintWriter targetOut = new PrintWriter(targetClient.getOutputStream(), true);
                                targetOut.println(username + ": " + tokens[1]);
                            } else {
                                out.println("User not found.");
                            }
                        } else {
                            out.println("Invalid command.");
                        }
                    }
                }

                clients.remove(username);
                client.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

2. 客户端代码：

import java.io.*;
import java.net.*;
import java.util.Scanner;

public class ChatClient {
    private static final int PORT = 8888;
    private static final String HOST = "localhost";

    public static void main(String[] args) {
        Socket socket = null;
        try {
            socket = new Socket(HOST, PORT);
            System.out.println("Connected to server.");

            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);

            Scanner consoleIn = new Scanner(System.in);
            while (true) {
                String line = in.readLine();
                if (line.startsWith("LOGIN")) {
                    System.out.println(line);
                    String[] tokens = consoleIn.nextLine().split("\\s+");
                    out.println("LOGIN " + tokens[0] + " " + tokens[1]);
                } else if (line.startsWith("REGISTER")) {
                    System.out.println(line);
                    String[] tokens = consoleIn.nextLine().split("\\s+");
                    out.println("REGISTER " + tokens[0] + " " + tokens[1]);
                } else if (line.startsWith("LOGIN SUCCESS")) {
                    System.out.println(line);
                    break;
                } else if (line.startsWith("LOGIN FAILED") || line.startsWith("REGISTER FAILED")) {
                    System.out.println(line);
                } else {
                    System.out.println(line);
                    break;
                }
            }

            new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                        while (true) {
                            String line = in.readLine();
                            if (line.startsWith("QUIT")) {
                                break;
                            } else {
                                System.out.println(line);
                            }
                        }
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }).start();

            while (true) {
                String input = consoleIn.nextLine();
                out.println(input);
                if (input.equalsIgnoreCase("quit")) {
                    break;
                }
            }

            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

这个聊天程序使用了多线程，每个客户端连接上服务器后，都会开启一个新的线程进行处理。服务器端维护了两个 Map，一个用于保存所有注册的用户（用户名和密码），另一个用于保存在线用户（用户名和对应的 Socket）。客户端可以使用 REGISTER 命令进行注册，使用 LOGIN 命令进行登陆。登陆成功后，客户端可以通过输入用户名和消息来向其他在线用户发送消息。如果输入“quit”，客户端会退出聊天室。