用java写一个使用TCP编程，实现客户端发送hello server 到服务器，服务器接收到的消息后打印内容在控制台，然后发送hello server 给客户端

好的，以下是Java代码实现：

客户端：

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

public class Client {
    public static void main(String[] args) throws Exception {
        Socket socket = new Socket("localhost", 8888);
        
        OutputStream os = socket.getOutputStream();
        PrintWriter pw = new PrintWriter(os);
        pw.write("hello server\n");
        pw.flush();

        InputStream is = socket.getInputStream();
        BufferedReader br = new BufferedReader(new InputStreamReader(is));
        String message = br.readLine();
        System.out.println("Server response: " + message);

        pw.close();
        os.close();
        socket.close();
    }
}

服务器端：

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

public class Server {
    public static void main(String[] args) throws Exception {
        ServerSocket serverSocket = new ServerSocket(8888);
        Socket socket = serverSocket.accept();

        InputStream is = socket.getInputStream();
        BufferedReader br = new BufferedReader(new InputStreamReader(is));
        String message = br.readLine();
        System.out.println("Client message: " + message);

        OutputStream os = socket.getOutputStream();
        PrintWriter pw = new PrintWriter(os);
        pw.write("hello client\n");
        pw.flush();

        pw.close();
        os.close();
        br.close();
        is.close();
        socket.close();
        serverSocket.close();
    }
}

以上代码使用了Java Socket编程，客户端向服务器发送 "hello server"，服务器接收到消息后打印内容并回复 "hello client" 给客户端。