Java CyclicBarrier getNumberWaiting() method

The getNumberWaiting() method of the Java CyclicBarrier class is used to get the number of parties currently waiting at the barrier. This method is primarily useful for debugging and assertions.

Syntax

Return

The number of parties currently blocked in the wait.

Example 1

import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
 
class Computation1 implements Runnable
{
    public static int product = 0;
    public void run()
    {
        product = 2 * 3;
        try
        {
           CyclicBarrierGetNumberWaitingExample1.newBarrier.await();
        } 
        catch (InterruptedException | BrokenBarrierException e) 
        {
            e.printStackTrace();
        }
    }
}
 
class Computation2 implements Runnable
{
    public static int sum = 0;
    public void run()
    {
        // check if newBarrier is broken or not
        System.out.println("Is the barrier broken? - " + CyclicBarrierGetNumberWaitingExample1.newBarrier.isBroken());
        sum = 10 + 20;
        try
        {
           CyclicBarrierGetNumberWaitingExample1.newBarrier.await(3000, TimeUnit.MILLISECONDS);
         
            // number of parties waiting at the barrier
            System.out.println("Number of parties waiting at the barrier "+
            "at this point = " +CyclicBarrierGetNumberWaitingExample1.newBarrier.getNumberWaiting());
        } 
        catch (InterruptedException | BrokenBarrierException e) 
        {
            e.printStackTrace();
        } 
        catch (TimeoutException e) 
        {
            e.printStackTrace();
        }
    }
}
 
 
public class CyclicBarrierGetNumberWaitingExample1 implements Runnable
{
    public static CyclicBarrier newBarrier = new CyclicBarrier(3);
     
    public static void main(String[] args)
    {
        // parent thread
        CyclicBarrierGetNumberWaitingExample1 test = new CyclicBarrierGetNumberWaitingExample1();
         
        Thread t1 = new Thread(test);
        t1.start();
    }
    @Override
    public void run()
    {
        System.out.println("Number of parties required to trip the barrier = "+
        newBarrier.getParties());
        System.out.println("Sum of product and sum = " + (Computation1.product + 
        Computation2.sum));
         
        // objects on which the child thread has to run
        Computation1 comp1 = new Computation1();
        Computation2 comp2 = new Computation2();
         
        // creation of child thread
        Thread t1 = new Thread(comp1);
        Thread t2 = new Thread(comp2);
         
        // moving child thread to runnable state
        t1.start();
        t2.start();
 
        TimeUnit unit = TimeUnit.SECONDS;
        try
        {
            CyclicBarrierGetNumberWaitingExample1.newBarrier.await(1,unit);
        } 
        catch (InterruptedException | BrokenBarrierException | TimeoutException e) 
        {
            e.printStackTrace();
        }
         
        // barrier breaks as the number of thread waiting for the barrier
        // at this point = 3
        System.out.println("Sum of product and sum = " + (Computation1.product + 
        Computation2.sum));
                 
        // Resetting the newBarrier
        newBarrier.reset();
        System.out.println("Barrier reset successful");
    }
}

Test it Now

Output:

Number of parties required to trip the barrier = 3
Sum of product and sum = 0
Is the barrier broken? - false
Number of parties waiting at the barrier at this point = 0
Sum of product and sum = 36
Barrier reset successful

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