public static void main(String[] args) { try { Client client=new Client(); String host=args.length==0?"127.0.0.1":args[0]; client.queryServer(host); } catch (Exception e) { e.printStackTrace(); System.exit(1); } System.exit(0); }的作用

这段代码是一个Java程序的入口方法，它的作用是创建一个客户端对象并连接到指定的服务器上。

具体来说，程序首先创建了一个Client对象，然后判断命令行参数是否为空，如果不为空，则将第一个参数作为服务器的IP地址，否则默认使用本地地址127.0.0.1。接下来，程序调用Client对象的queryServer方法，该方法会连接到指定的服务器，并与服务器进行通信。

如果程序出现异常，则会打印异常堆栈信息并退出程序，返回值为1。如果程序正常执行完毕，则会退出程序，返回值为0。

总之，这段代码的主要作用是启动一个客户端程序，并连接到指定的服务器上。

相关问题

netty Bootstrap 学习例子，写在main方法

好的，以下是一个简单的 Netty Bootstrap 学习例子，写在 main 方法中：

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;

public class NettyClient {
    private final String host;
    private final int port;

    public NettyClient(String host, int port) {
        this.host = host;
        this.port = port;
    }

    public void run() throws InterruptedException {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(group)
                    .channel(NioSocketChannel.class)
                    .option(ChannelOption.TCP_NODELAY, true)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline().addLast(new NettyClientHandler());
                        }
                    });

            ChannelFuture future = bootstrap.connect(host, port).sync();
            future.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws InterruptedException {
        String host = "localhost";
        int port = 8888;
        new NettyClient(host, port).run();
    }
}

class NettyClientHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        String msg = "Hello, Netty!";
        ByteBuf byteBuf = Unpooled.buffer(msg.getBytes().length);
        byteBuf.writeBytes(msg.getBytes());
        ctx.writeAndFlush(byteBuf);
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf byteBuf = (ByteBuf) msg;
        byte[] bytes = new byte[byteBuf.readableBytes()];
        byteBuf.readBytes(bytes);
        String result = new String(bytes);
        System.out.println("Received message from server: " + result);
        byteBuf.release();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}

这是一个简单的 Netty 客户端，它会连接到指定的服务器地址和端口，并向服务器发送一条消息，然后等待服务器的响应。在这个例子中，我们使用了 NioEventLoopGroup 和 NioSocketChannel，具体细节可以参考 Netty 官方文档。同时，我们也实现了一个 NettyClientHandler，它会在客户端与服务器建立连接后被调用，并且会在接收到服务器的响应后被调用。

java代码 个人聊天室 要求： 1. 可使用文字聊天 2. 可以发送文件 3. 可以私聊 代码

很抱歉，由于代码比较长，无法在这里直接贴出。不过，以下是具体的实现步骤和代码结构，供你参考：

1. 服务器端

（1）创建一个 ServerSocket 对象，用于监听客户端的连接请求。

ServerSocket serverSocket = new ServerSocket(port);

（2）创建一个 HashMap 用于保存所有已连接的客户端。

Map<String, Socket> clientMap = new HashMap<>();

（3）使用 while 循环来等待客户端的连接请求，并在接收到请求后开启一个新的线程来处理客户端的请求。

while (true) {
    Socket socket = serverSocket.accept();
    new ServerThread(socket, clientMap).start();
}

（4）在线程中使用输入输出流来实现客户端之间的通信，并实现文字聊天、发送文件和私聊等功能。

2. 客户端

（1）创建一个 Socket 对象，用于连接服务器。

Socket socket = new Socket(host, port);

（2）使用输入输出流来发送和接收数据，并实现文字聊天、发送文件和私聊等功能。

具体的代码实现可以参考下面的示例代码：

ServerThread.java

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

public class ServerThread extends Thread {
    private Socket socket;
    private Map<String, Socket> clientMap;

    public ServerThread(Socket socket, Map<String, Socket> clientMap) {
        this.socket = socket;
        this.clientMap = clientMap;
    }

    public void run() {
        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
            String clientName = reader.readLine();

            System.out.println(clientName + " connected");

            // 将新连接的客户端添加到客户端列表中
            clientMap.put(clientName, socket);

            String line;
            while ((line = reader.readLine()) != null) {
                if (line.equals("quit")) {
                    break;
                } else if (line.startsWith("@")) {
                    // 私聊功能
                    String[] tokens = line.split(" ");
                    String targetClientName = tokens[0].substring(1);
                    String message = line.substring(tokens[0].length() + 1);
                    Socket targetSocket = clientMap.get(targetClientName);
                    if (targetSocket != null) {
                        BufferedWriter targetWriter = new BufferedWriter(new OutputStreamWriter(targetSocket.getOutputStream()));
                        targetWriter.write(clientName + " : " + message + "\n");
                        targetWriter.flush();
                    } else {
                        writer.write("Client " + targetClientName + " not found\n");
                        writer.flush();
                    }
                } else if (line.startsWith("#")) {
                    // 发送文件功能
                    String[] tokens = line.split(" ");
                    String targetClientName = tokens[0].substring(1);
                    String fileName = tokens[1];
                    Socket targetSocket = clientMap.get(targetClientName);
                    if (targetSocket != null) {
                        FileInputStream fileInputStream = new FileInputStream(fileName);
                        OutputStream outputStream = targetSocket.getOutputStream();
                        byte[] buffer = new byte[1024];
                        int len;
                        while ((len = fileInputStream.read(buffer)) != -1) {
                            outputStream.write(buffer, 0, len);
                        }
                        outputStream.flush();
                        fileInputStream.close();
                        writer.write("File " + fileName + " sent to " + targetClientName + "\n");
                        writer.flush();
                    } else {
                        writer.write("Client " + targetClientName + " not found\n");
                        writer.flush();
                    }
                } else {
                    // 文字聊天功能
                    for (Socket clientSocket : clientMap.values()) {
                        if (clientSocket != socket) {
                            BufferedWriter clientWriter = new BufferedWriter(new OutputStreamWriter(clientSocket.getOutputStream()));
                            clientWriter.write(clientName + " : " + line + "\n");
                            clientWriter.flush();
                        }
                    }
                }
            }

            // 将断开连接的客户端从客户端列表中移除
            clientMap.remove(clientName);

            reader.close();
            writer.close();
            socket.close();

            System.out.println(clientName + " disconnected");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Server.java

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.HashMap;
import java.util.Map;

public class Server {
    private int port;
    private Map<String, Socket> clientMap;

    public Server(int port) {
        this.port = port;
        this.clientMap = new HashMap<>();
    }

    public void start() throws IOException {
        ServerSocket serverSocket = new ServerSocket(port);
        System.out.println("Server started at port " + port);

        while (true) {
            Socket socket = serverSocket.accept();
            new ServerThread(socket, clientMap).start();
        }
    }

    public static void main(String[] args) throws IOException {
        Server server = new Server(8888);
        server.start();
    }
}

Client.java

import java.io.*;
import java.net.Socket;

public class Client {
    private String host;
    private int port;
    private String name;

    public Client(String host, int port, String name) {
        this.host = host;
        this.port = port;
        this.name = name;
    }

    public void start() throws IOException {
        Socket socket = new Socket(host, port);
        System.out.println("Connected to server");

        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        BufferedReader socketReader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
        String line;

        // 发送客户端名称给服务器
        writer.write(name + "\n");
        writer.flush();

        while ((line = reader.readLine()) != null) {
            if (line.equals("quit")) {
                break;
            } else if (line.startsWith("@")) {
                // 私聊功能
                String[] tokens = line.split(" ");
                String targetClientName = tokens[0].substring(1);
                String message = line.substring(tokens[0].length() + 1);
                writer.write(line + "\n");
                writer.flush();
                String response = socketReader.readLine();
                System.out.println(response);
            } else if (line.startsWith("#")) {
                // 发送文件功能
                String[] tokens = line.split(" ");
                String targetClientName = tokens[0].substring(1);
                String fileName = tokens[1];
                File file = new File(fileName);
                if (file.exists()) {
                    writer.write(line + "\n");
                    writer.flush();
                    OutputStream outputStream = socket.getOutputStream();
                    FileInputStream fileInputStream = new FileInputStream(file);
                    byte[] buffer = new byte[1024];
                    int len;
                    while ((len = fileInputStream.read(buffer)) != -1) {
                        outputStream.write(buffer, 0, len);
                    }
                    outputStream.flush();
                    fileInputStream.close();
                    String response = socketReader.readLine();
                    System.out.println(response);
                } else {
                    System.out.println("File " + fileName + " not found");
                }
            } else {
                // 文字聊天功能
                writer.write(line + "\n");
                writer.flush();
            }
        }

        reader.close();
        socketReader.close();
        writer.close();
        socket.close();

        System.out.println("Disconnected");
    }

    public static void main(String[] args) throws IOException {
        Client client = new Client("localhost", 8888, "client1");
        client.start();
    }
}

上面的代码实现了一个简单的个人聊天室，可以实现文字聊天、发送文件和私聊等功能。你可以根据自己的需求进行修改和扩展。