Barrier.java

package com.freemindcafe.concurrency.sample6;

import java.util.concurrent.Semaphore;

public class Barrier {
    
    private int nThreads;
    private int counter;
    private Semaphore semaphore = new Semaphore(0);
    private Semaphore mutex = new Semaphore(1);
    
    public Barrier(int nThreads) {
        this.counter = nThreads;
        this.nThreads = nThreads;
    }
    
    public void await() throws InterruptedException{
        mutex.acquire();
        counter--;
        mutex.release();
        if(counter == 0){
            semaphore.release(nThreads);
        }
        semaphore.acquire();
    }

}