CyclicBarrier Real time Usage

In continuation to what we've learnt in CyclicBarrier , find below code snippet explaining real time scenario which is a perfect analogy.

package com.concurrent.jdk5;

import java.util.concurrent.BrokenBarrierException;

import java.util.concurrent.CyclicBarrier;

/* 4 bikers starting from Manali and reaching to Leh after

 * crossing 3 checkpoints */

public class CyclicBarrierDemo {

     public static void main(String[] args) {

          final CyclicBarrier checkPoint = new CyclicBarrier(4, new BarrierAction());

    

          Thread t1 = new Thread(new Biker(checkPoint), "Biker 1");

          Thread t2 = new Thread(new Biker(checkPoint), "Biker 2");

          Thread t3 = new Thread(new Biker(checkPoint), "Biker 3");

          Thread t4 = new Thread(new Biker(checkPoint), "Biker 4");

          t1.start();

          t2.start();

          t3.start();

          t4.start();

     }

}

/* Worker thread*/

class Biker implements Runnable {

     private CyclicBarrier checkPoint;

     public Biker(CyclicBarrier checkPoint) {

          this.checkPoint = checkPoint;

         

     }

    

     public void run() {

          try {

              /* All bikers called await() and waiting to end the barrier. Once number of threads

               * crossing the barrier is equal to number mentioned in above construtor, then

               * last thread entering will call the barrier action which has seperate implementation*/

             

              System.out.println(Thread.currentThread().getName() + 

              " has left Manali");

              checkPoint.await();

              System.out.println(Thread.currentThread().getName() + 

              " has left the first checkpoint / barrier");

              /* Again, all bikers called await() and waiting to end the barrier. */

              checkPoint.await();

              System.out.println(Thread.currentThread().getName() + 

              " has left the second checkpoint / barrier");

              checkPoint.await();

              System.out.println(Thread.currentThread().getName() + 

           " has reached Leh");

          } catch (InterruptedException | BrokenBarrierException e) {

              e.printStackTrace();

          }

     }

}

/* barrierAction-the action to execute when all threads crossed the barrier number */

class BarrierAction implements Runnable {

     public void run() {

          System.out.println("Barrier Action run by Thread :"+Thread.currentThread().getName());

          System.out.println("\nAll bikers have arrived to checkpoint. Lets refill the petrol\n");

     }

}

Output

Biker 1 has left Manali

Biker 4 has left Manali

Biker 3 has left Manali

Biker 2 has left Manali

Barrier Action run by Thread :Biker 2

All bikers have arrived to checkpoint. Lets refill the petrol

Biker 2 has left the first checkpoint / barrier

Biker 3 has left the first checkpoint / barrier

Biker 1 has left the first checkpoint / barrier

Biker 4 has left the first checkpoint / barrier

Barrier Action run by Thread :Biker 4

All bikers have arrived to checkpoint. Lets refill the petrol

Biker 4 has left the second checkpoint / barrier

Biker 1 has left the second checkpoint / barrier

Biker 2 has left the second checkpoint / barrier

Biker 3 has left the second checkpoint / barrier

Barrier Action run by Thread :Biker 3

All bikers have arrived to checkpoint. Lets refill the petrol

Biker 3 has reached Leh

Biker 1 has reached Leh

Biker 2 has reached Leh

Biker 4 has reached Leh

References : http://codepumpkin.com/cyclicbarrier-java-concurrency-utilities/