How to make use of CyclicBarrier

The CyclicBarrier allows you to run some tasks on the condition that certain prior tasks complete. Let's suppose a mixed tennis game which requires the presence of 4 players in order to start, here is how you might implement this in Java using the predefined CyclicBarrier class:

import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;

// The run() method in this thread should be called only when 
// four players are ready to start the game 
class MixedDoubleTennisGame extends Thread {
@Override
public void run() {
System.out.println("All four players ready, game starts \n Love all...");
}
}

// This thread simulates arrival of a player.
// Once a player arrives, he/she should wait for other players to arrive
class Player extends Thread {
CyclicBarrier waitPoint;

public Player(CyclicBarrier barrier, String name) {
this.setName(name);
waitPoint = barrier;
this.start();
}

@Override
public void run() {
System.out.println("Player " + getName() + " is ready ");
try {
waitPoint.await(); // await for all four players to arrive
} catch (BrokenBarrierException | InterruptedException exception) {
System.out.println("An exception occurred while waiting... " + exception);
}
}
}

// Creates a CyclicBarrier object by passing the number of threads and the
// thread to run
// when all the threads reach the barrier
class CyclicBarrierTest {
public static void main(String[] args) {
// a mixed-double tennis game requires four players;
// so wait for four players
// (i.e., four threads) to join to start the game
System.out.println("Reserving tennis court \n" + "As soon as four players arrive, game will start");
CyclicBarrier barrier = new CyclicBarrier(4, new MixedDoubleTennisGame());
new Player(barrier, "G I Joe");
new Player(barrier, "Dora");
new Player(barrier, "Tintin");
new Player(barrier, "Barbie");
}
}

Running this outputs:

Reserving tennis court 
As soon as four players arrive, game will start
Player Dora is ready 
Player G I Joe is ready 
Player Tintin is ready 
Player Barbie is ready 
All four players ready, game starts 
 Love all...