Многопоточность в Java. Часть 1

class HelloWorld {
    public static void main(String[] args) {
        System.out.println("This program is running on: " + Thread.currentThread());
        System.out.println("Hello world");
    }
}

class MyThread extends Thread {

    @Override
    public void run() {
        System.out.println("Executing code from: " + Thread.currentThread());
        System.out.println("Hello world");
    }
}

class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Creating a new thread from : " + Thread.currentThread());
        var myThread = new MyThread();
        myThread.start();
        System.out.println("Leaving from: " + Thread.currentThread());
    }
}

class MyThread extends Thread {
    @Override
    public void run() {
        System.out.println("run() выполняется в потоке: " + Thread.currentThread().getName());
    }
}

class HelloWorld {
    public static void main(String[] args) {
        MyThread thread = new MyThread();

        System.out.println("Вызываем run() напрямую:");
        thread.run();  // Выполнится в main-потоке

        System.out.println("Вызываем start():");
        thread.start();  // Создаст новый поток
    }
}

class MyRunnable implements Runnable {

    @Override
    public void run() {
        System.out.println("Using Runnable from: " +  Thread.currentThread());
        System.out.println("Hello world");
    }
}

class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Creating a new thread from : " + Thread.currentThread());
        var myRunnable = new MyRunnable();
        var thread = new Thread(myRunnable);
        thread.start();
        System.out.println("Leaving from: " + Thread.currentThread());
   }
}

var thread = new Thread(new Runnable() {
    @Override
    public void run() {
        System.out.println("Using Runnable from: " + Thread.currentThread());
        System.out.println("Hello world");
    }
});
thread.start();

var thread = new Thread(() -> {
    System.out.println("Using Runnable from: " + Thread.currentThread());
    System.out.println("Hello world");
});
thread.start();

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.stream.Collectors;
import java.net.URI;

public class SingleThreadedServer {

    private final MostFrequentWordService wordService = new MostFrequentWordService();

    public SingleThreadedServer(int port) throws IOException {
        try (var serverSocket = new ServerSocket(port)) {
            while (true) {
                try (var socket = serverSocket.accept()) {
                    handle(socket);
                }
            }
        }
    }

    private void handle(Socket socket) {
        System.out.println("Client connected: " + socket);
        try (var in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
             var out = new PrintWriter(socket.getOutputStream(), true)) {
            out.println("Enter url:");
            String line;
            while ((line = in.readLine()) != null) {
                if (isValid(line)) {
                    var wordCount = wordService.mostFrequentWord(line).stream()
                            .map(counter -> counter.word() + ": " + counter.count())
                            .collect(Collectors.joining(System.lineSeparator()));
                    out.println(wordCount);
                } else if (line.contains("quit")) {
                    out.println("Goodbye!");
                    break;
                } else {
                    out.println("Malformed URL");
                }
                out.println("\nEnter url:");
            }
        } catch (IOException e) {
            System.out.println("Communication error: " + e.getMessage());
        }
    }

    private static boolean isValid(String url) {
        try {
            URI.create(url).toURL();
            return true;
        } catch (Exception e) {
            System.out.println("invalid url: " + url);
            return false;
        }
    }

    public static void main(String[] args) throws IOException {
        new SingleThreadedServer(2222);
    }
}

import org.jsoup.Jsoup;
import java.io.IOException;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collectors;

record WordCount(String word, long count) {}

public class MostFrequentWordService {

    List<WordCount> mostFrequentWord(String url) throws IOException {
        return Arrays.stream(getWords(url))
                .filter(word -> word.length() > 3)
                .map(String::toLowerCase)
                .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()))
                .entrySet().stream()
                .sorted(Map.Entry.comparingByValue(Comparator.reverseOrder()))
                .limit(5)
                .map(entry -> new WordCount(entry.getKey(), entry.getValue()))
                .toList();
    }

    private String[] getWords(String url) throws IOException {
        return Jsoup.connect(url).get().body().text().split("\\W+");
    }
}

public class MultiThreadedServer {

    private final MostFrequentWordService wordService = new MostFrequentWordService();

    public MultiThreadedServer(int port) throws IOException {
        try (var serverSocket = new ServerSocket(port)) {
            while (true) {
                var socket = serverSocket.accept();
                var thread = new Thread(() -> handle(socket));
                thread.start();
            }
        }
    }
    
    // оставшийся код будет без изменений
}