用Java实现一个简易的MUD游戏开发，并给出具体代码，要求如下：包括服务器端和客户端两部分内容 1.同时支持多人在线游戏 2.创建一个虚拟的世界 3.玩家可以在虚拟世界中移动方向(w,e,s,n,ne,se,nw,sw,u,d)； 4.玩家的动作（包括连线、移动）对其他相关玩家（同一房间）可见 5.玩家的基本动作包括，查看(look,l)，退出(quit) 6.玩家账户信息存储在数据库或文件中（第一次登陆创建账户） 7.客户端能够建立与服务器的链接、向服务器发送消息，接受并显示信息

这是一个比较复杂的项目，需要考虑很多细节，下面是一个简单的 Java MUD 游戏服务器和客户端的实现示例：

服务器端代码：

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;

public class MUDServer {
    private List<MUDPlayer> players = new ArrayList<>();
    private MUDWorld world = new MUDWorld();

    public static void main(String[] args) {
        MUDServer server = new MUDServer();
        server.start();
    }

    public void start() {
        try {
            ServerSocket serverSocket = new ServerSocket(8888);
            System.out.println("MUD server started at port 8888.");
            while (true) {
                Socket socket = serverSocket.accept();
                MUDPlayer player = new MUDPlayer(socket, world, players);
                players.add(player);
                player.start();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

客户端代码：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;

public class MUDClient {
    private Socket socket;
    private BufferedReader in;
    private PrintWriter out;

    public static void main(String[] args) {
        MUDClient client = new MUDClient();
        client.connect();
    }

    public void connect() {
        try {
            socket = new Socket("localhost", 8888);
            in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            out = new PrintWriter(socket.getOutputStream(), true);
            BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));

            String userInput;
            while ((userInput = stdIn.readLine()) != null) {
                out.println(userInput);
                String serverResponse = in.readLine();
                System.out.println(serverResponse);
            }

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

MUDPlayer 类（处理玩家的输入输出和逻辑）：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.List;

public class MUDPlayer extends Thread {
    private Socket socket;
    private BufferedReader in;
    private PrintWriter out;
    private MUDWorld world;
    private List<MUDPlayer> players;
    private String name;
    private MUDRoom currentRoom;

    public MUDPlayer(Socket socket, MUDWorld world, List<MUDPlayer> players) {
        this.socket = socket;
        this.world = world;
        this.players = players;
    }

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

            out.println("Welcome to the MUD game! Please enter your name:");
            name = in.readLine();
            out.println("Welcome, " + name + "!");

            if (!world.hasPlayer(name)) {
                currentRoom = world.getStartingRoom();
                world.addPlayer(name, currentRoom);
            } else {
                currentRoom = world.getPlayerRoom(name);
                out.println("You are now in " + currentRoom.getName() + ".");
                broadcast(name + " has joined the game.");
            }

            String inputLine;
            while ((inputLine = in.readLine()) != null) {
                String[] tokens = inputLine.split(" ");
                if (tokens.length == 0) {
                    continue;
                }
                String command = tokens[0];
                if ("quit".equalsIgnoreCase(command)) {
                    break;
                } else if ("look".equalsIgnoreCase(command) || "l".equalsIgnoreCase(command)) {
                    out.println(currentRoom.getDescription());
                    out.println(currentRoom.getExits());
                    out.println(currentRoom.getPlayers());
                } else if ("say".equalsIgnoreCase(command)) {
                    broadcast(name + " says: " + inputLine.substring(4));
                } else if ("move".equalsIgnoreCase(command)) {
                    String direction = tokens[1];
                    MUDRoom nextRoom = currentRoom.getExit(direction);
                    if (nextRoom == null) {
                        out.println("You cannot go that way.");
                    } else {
                        currentRoom.removePlayer(name);
                        nextRoom.addPlayer(name);
                        currentRoom = nextRoom;
                        out.println(currentRoom.getDescription());
                        out.println(currentRoom.getExits());
                        out.println(currentRoom.getPlayers());
                        broadcast(name + " has left the room.");
                        broadcast(name + " has entered the room.");
                    }
                } else {
                    out.println("Invalid command.");
                }
            }

            out.println("Bye, " + name + "!");
            currentRoom.removePlayer(name);
            players.remove(this);
            broadcast(name + " has left the game.");
            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void broadcast(String message) {
        for (MUDPlayer player : players) {
            if (!player.getName().equals(name) && player.getCurrentRoom() == currentRoom) {
                player.sendMessage(message);
            }
        }
    }

    public void sendMessage(String message) {
        out.println(message);
    }

    public String getName() {
        return name;
    }

    public MUDRoom getCurrentRoom() {
        return currentRoom;
    }
}

MUDWorld 类（包含虚拟世界的信息和逻辑）：

import java.util.HashMap;
import java.util.Map;

public class MUDWorld {
    private Map<String, MUDRoom> rooms = new HashMap<>();
    private Map<String, MUDPlayer> players = new HashMap<>();

    public MUDWorld() {
        MUDRoom hall = new MUDRoom("Hall", "You are in the hall.");
        MUDRoom kitchen = new MUDRoom("Kitchen", "You are in the kitchen.");
        MUDRoom bedroom = new MUDRoom("Bedroom", "You are in the bedroom.");
        MUDRoom bathroom = new MUDRoom("Bathroom", "You are in the bathroom.");

        hall.addExit("east", kitchen);
        hall.addExit("up", bedroom);

        kitchen.addExit("west", hall);

        bedroom.addExit("down", hall);
        bedroom.addExit("east", bathroom);

        bathroom.addExit("west", bedroom);

        rooms.put("hall", hall);
        rooms.put("kitchen", kitchen);
        rooms.put("bedroom", bedroom);
        rooms.put("bathroom", bathroom);
    }

    public MUDRoom getStartingRoom() {
        return rooms.get("hall");
    }

    public void addPlayer(String name, MUDRoom room) {
        players.put(name, new MUDPlayer(name, room));
        room.addPlayer(name);
    }

    public boolean hasPlayer(String name) {
        return players.containsKey(name);
    }

    public MUDRoom getPlayerRoom(String name) {
        return players.get(name).getCurrentRoom();
    }

    public void removePlayer(String name) {
        MUDPlayer player = players.remove(name);
        player.getCurrentRoom().removePlayer(name);
    }
}

MUDRoom 类（代表一个房间）：

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MUDRoom {
    private String name;
    private String description;
    private Map<String, MUDRoom> exits = new HashMap<>();
    private List<String> players = new ArrayList<>();

    public MUDRoom(String name, String description) {
        this.name = name;
        this.description = description;
    }

    public void addExit(String direction, MUDRoom room) {
        exits.put(direction, room);
    }

    public MUDRoom getExit(String direction) {
        return exits.get(direction);
    }

    public void addPlayer(String name) {
        players.add(name);
    }

    public void removePlayer(String name) {
        players.remove(name);
    }

    public String getName() {
        return name;
    }

    public String getDescription() {
        return description;
    }

    public String getExits() {
        StringBuilder sb = new StringBuilder();
        sb.append("Exits: ");
        for (String direction : exits.keySet()) {
            sb.append(direction).append(" ");
        }
        return sb.toString();
    }

    public String getPlayers() {
        StringBuilder sb = new StringBuilder();
        sb.append("Players: ");
        for (String player : players) {
            sb.append(player).append(" ");
        }
        return sb.toString();
    }
}

注意：这只是一个简单的示例，还有很多细节需要考虑和实现，比如：玩家账户信息的存储、安全性、游戏内容的丰富性等。