Java で IO ストリームを使用してファイルとネットワーク通信を処理するにはどうすればよいですか?

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;

public class FileDemo {
    public static void main(String[] args) {
        File file = new File("data.txt");
        
        try (BufferedReader br = new BufferedReader(new FileReader(file))) {
            String line;
            while ((line = br.readLine()) != null) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

public class FileDemo {
    public static void main(String[] args) {
        File file = new File("output.txt");
        
        try (BufferedWriter bw = new BufferedWriter(new FileWriter(file))) {
            bw.write("Hello, World!");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import java.io.IOException;
import java.io.InputStream;
import java.net.Socket;

public class ClientDemo {
    public static void main(String[] args) {
        try (Socket socket = new Socket("localhost", 8080)) {
            InputStream is = socket.getInputStream();
            
            byte[] buffer = new byte[1024];
            int length = is.read(buffer);
            
            System.out.println("Received message: " + new String(buffer, 0, length));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import java.io.IOException;
import java.io.OutputStream;
import java.net.Socket;

public class ClientDemo {
    public static void main(String[] args) {
        try (Socket socket = new Socket("localhost", 8080)) {
            OutputStream os = socket.getOutputStream();
            
            String message = "Hello, Server!";
            os.write(message.getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}