What do you know about CyclicBarrier in java?

Problem statement: Write a cab transport service where passengers will come one by one and join the queue but they can't board the cab or cab won't move until there are 3 passengers waiting in the queue.

1. CyclicBarrier is one of the Java Concurrency Utility.
2. It was introduced in java 5
3. It falls under java.util.concurrency package
4. Using this we can synchronised the threads which are processing through some algorithm
5.  Using this we can make threads wait at a point of code until specific number of threads have reached that point of code.Threads will be ordered to wait on call of await() method
6. CyclicBarrier can be instantiated as: CyclicBarrier obj = new CyclicBarrier(n) where n is an interger and also that specific number.

[1]:

import java.util.concurrent.CyclicBarrier;

public class CabBooking {

    public static void main(String args[]) throws InterruptedException {

        CyclicBarrier cyclicBarrier = new CyclicBarrier(3);

        Thread t1 = new Thread(new CabService(cyclicBarrier));

        t1.setName("Passenger-1");

        t1.start();

        Thread.sleep(5000);

        Thread t2 = new Thread(new CabService(cyclicBarrier));

        t2.setName("Passenger=-2");

        t2.start();

        Thread.sleep(5000);

        Thread t3 = new Thread(new CabService(cyclicBarrier));

        t3.setName("Passenger-3");

        t3.start();

        Thread.sleep(5000);

    }

}

[2]:

import java.util.concurrent.BrokenBarrierException;

import java.util.concurrent.CyclicBarrier;

public class CabService implements Runnable {

    CyclicBarrier cyclicBarrier;

    public CabService(CyclicBarrier cyclicBarrier) {

        this.cyclicBarrier = cyclicBarrier;

    }

    @Override

    public void run() {

        try {

            System.out.println("++++++ " + Thread.currentThread().getName() + " has arrived");

            try {

                cyclicBarrier.await();

            } catch (BrokenBarrierException e) {

                e.printStackTrace();

            }

            System.out.println("****** " + Thread.currentThread().getName() + " is going to board the cab");

        } catch (InterruptedException e) {

            e.printStackTrace();

        }

    }

}

Output:

++++++ Passenger-1 has arrived

++++++ Passenger=-2 has arrived

++++++ Passenger-3 has arrived

****** Passenger-3 is going to board the cab

****** Passenger-1 is going to board the cab

****** Passenger=-2 is going to board the cab
ref: click for oracle doc