Example usage of CountDownLatch

VideoConference.java

import java.util.concurrent.CountDownLatch;
import java.util.Random;
import java.util.logging.Level;
import java.util.logging.Logger;

class Participant implements Runnable {
    private final CountDownLatch latch;
    private final Random random = new Random();
    private long id;
    private static final Logger LOGGER = Logger.getLogger(Participant.class.getName());

    public Participant(CountDownLatch latch) {
        this.latch = latch;
    }

    @Override
    public void run() {
        // Simulate the time taken for the participant to join
        try {
            Thread.sleep(random.nextLong(10000));
        } catch (InterruptedException e) {
            LOGGER.log(Level.SEVERE, e.getMessage(), e.getStackTrace());
            Thread.currentThread().interrupt();
        }

        // Signal that the participant has joined
        latch.countDown();
        System.out.println("Participant " + id + " has joined the conference.");
    }

    public void setId(long id) {
        this.id = id;
    }
}

public class VideoConference {
    private static final Logger LOGGER = Logger.getLogger(VideoConference.class.getName());

    public static void main(String[] args) {
        // Define the number of participants
        int numberOfParticipants = 5;

        // Create a CountDownLatch with the number of participants
        CountDownLatch latch = new CountDownLatch(numberOfParticipants);

        // Create participant threads and start them
        for (int i = 0; i < numberOfParticipants; i++) {
            var participant = new Participant(latch);
            var thread = new Thread(participant);
            participant.setId(thread.threadId());
            thread.start();
        }

        try {
            // Wait for all participants to join
            latch.await();
            System.out.println("All participants have joined. The meeting has started!");
        } catch (InterruptedException e) {
            LOGGER.log(Level.SEVERE, e.getMessage(), e.getStackTrace());
            Thread.currentThread().interrupt();
        }
    }
}

Output:

Participant 34 has joined the conference.
Participant 33 has joined the conference.
Participant 31 has joined the conference.
Participant 30 has joined the conference.
Participant 32 has joined the conference.
All participants have joined. The meeting has started!