给出一个java实现web服务器的例子

好的，以下是一个简单的Java实现Web服务器的例子：

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

public class SimpleWebServer {

    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(8080);
        System.out.println("Web服务器已启动，监听端口：8080");
        while (true) {
            Socket clientSocket = serverSocket.accept();
            System.out.println("收到来自 " + clientSocket.getInetAddress().getHostAddress() + " 的HTTP请求");
            BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
            String requestLine = in.readLine();
            System.out.println("请求头：" + requestLine);
            String[] requestParts = requestLine.split(" ");
            String method = requestParts[0];
            String path = requestParts[1];
            if (!method.equals("GET")) {
                clientSocket.close();
                continue;
            }
            File file = new File("." + path);
            if (!file.exists()) {
                PrintWriter out = new PrintWriter(clientSocket.getOutputStream());
                out.println("HTTP/1.1 404 Not Found");
                out.println();
                out.close();
                continue;
            }
            FileInputStream fileInputStream = new FileInputStream(file);
            byte[] data = new byte[(int) file.length()];
            fileInputStream.read(data);
            OutputStream outputStream = clientSocket.getOutputStream();
            PrintWriter printWriter = new PrintWriter(outputStream);
            printWriter.println("HTTP/1.1 200 OK");
            printWriter.println("Content-Type: text/html");
            printWriter.println("Content-Length: " + file.length());
            printWriter.println();
            outputStream.write(data);
            printWriter.close();
            fileInputStream.close();
            clientSocket.close();
            System.out.println("已向 " + clientSocket.getInetAddress().getHostAddress() + " 发送HTTP响应");
        }
    }
}

运行这段代码后，你可以在浏览器中输入 `http://localhost:8080` 来访问该Web服务器。它会返回当前工作目录下的 `index.html` 文件的内容。如果该文件不存在，则会返回404 Not Found错误。你可以根据需要修改代码中的端口号和默认文件名。