Follow these steps to implement the example:

1. Create a class named Videoconference and specify that it implements the Runnable interface. This class will implement the video conference system:

        public class Videoconference implements Runnable{

2. Declare a CountDownLatch object named controller:

        private final CountDownLatch controller;

3. Implement the constructor of the class that initializes the CountDownLatch attribute. The Videoconference class will wait for the arrival of the number of participants received as a parameter:

        public Videoconference(int number) { 
          controller=new CountDownLatch(number); 
        }

4. Implement the arrive() method. This method will be called each time a participant arrives for the video conference. It receives a String type named name as the parameter:

        public void arrive(String name){

5. First, it writes a message with the parameter it has received:

        System.out.printf("%s has arrived.",name);

6. Then, it calls the countDown() method of the CountDownLatch object:

        controller.countDown();

7. Finally, it writes another message with the number of participants whose arrival is pending, using the getCount() method of the CountDownLatch object:

        System.out.printf("VideoConference: Waiting for %d
                           participants.
",controller.getCount());

8. Next, implement the main method of the video conference system. It's the run() method that every Runnable object must have:

        @Override 
        public void run() {

9. First, use the getCount() method to write a message with the number of participants in the video conference:

        System.out.printf("VideoConference: Initialization: %d
                           participants.
",controller.getCount());

10. Then, use the await() method to wait for all the participants. As this method can throw an InterruptedException exception, you must include the code to process it:

        try { 
          controller.await();

11. Finally, write a message to indicate that all the participants have arrived:

          System.out.printf("VideoConference: All the participants have
                             come
"); 
          System.out.printf("VideoConference: Let's start...
"); 
        } catch (InterruptedException e) { 
          e.printStackTrace(); 
        }

12. Next, create the Participant class and specify that it implements the Runnable interface. This class represents each participant in the video conference:

        public class Participant implements Runnable {

13. Declare a private Videoconference attribute named conference:

        private Videoconference conference;

14. Declare a private String attribute named name:

        private String name;

15. Implement the constructor of the class that initializes both the preceding attributes:

        public Participant(Videoconference conference, String name) { 
          this.conference=conference; 
          this.name=name; 
        }

16. Implement the run() method of the participants:

        @Override 
        public void run() {

17. First, put the thread to sleep for a random period of time:

        long duration=(long)(Math.random()*10); 
        try { 
          TimeUnit.SECONDS.sleep(duration); 
        } catch (InterruptedException e) { 
          e.printStackTrace(); 
        }

18. Then, use the arrive() method of the Videoconference object to indicate the arrival of this participant:

        conference.arrive(name);

19. Finally, implement the main class of the example by creating a class named Main and adding the main() method to it:

        public class Main { 
          public static void main(String[] args) {

20. Next, create a Videoconference object named conference that waits for 10 participants:

        Videoconference conference=new Videoconference(10);

21. Create Thread to run this Videoconference object and start it:

        Thread threadConference=new Thread(conference); 
        threadConference.start();

22. Create 10 Participant objects, a Thread object to run each of them, and start all the threads:

        for (int i=0; i<10; i++){ 
          Participant p=new Participant(conference, "Participant "+i); 
          Thread t=new Thread(p); 
          t.start(); 
        }