Java Phaser class

Introduction

Phaser synchronizes threads by representing one or more phases of activity.

Here is an example that shows Phaser class usage.

It creates three threads, each of which have three phases.

It uses a Phaser to synchronize each phase. 


import java.util.concurrent.Phaser;

public class Main {
  public static void main(String args[]) {
    Phaser phsr = new Phaser(1);
    int curPhase;

    System.out.println("Starting");

    new MyThread(phsr, "A");
    new MyThread(phsr, "B");
    new MyThread(phsr, "C");

    // Wait for all threads to complete phase one.
    curPhase = phsr.getPhase();// w ww. j av a 2  s . co m
    phsr.arriveAndAwaitAdvance();
    System.out.println("Phase " + curPhase + " Complete");

    // Wait for all threads to complete phase two.
    curPhase = phsr.getPhase();
    phsr.arriveAndAwaitAdvance();
    System.out.println("Phase " + curPhase + " Complete");

    curPhase = phsr.getPhase();
    phsr.arriveAndAwaitAdvance();
    System.out.println("Phase " + curPhase + " Complete");

    // Deregister the main thread.
    phsr.arriveAndDeregister();

    if (phsr.isTerminated())
      System.out.println("The Phaser is terminated");
  }
}

// A thread of execution that uses a Phaser.
class MyThread implements Runnable {
  Phaser phsr;
  String name;

  MyThread(Phaser p, String n) {
    phsr = p;
    name = n;
    phsr.register();
    new Thread(this).start();
  }

  public void run() {

    System.out.println("Thread " + name + " Beginning Phase One");
    phsr.arriveAndAwaitAdvance(); 
    
    try {
      Thread.sleep(10);
    } catch (InterruptedException e) {
      System.out.println(e);
    }

    System.out.println("Thread " + name + " Beginning Phase Two");
    phsr.arriveAndAwaitAdvance(); // Signal arrival.

    try {
      Thread.sleep(10);
    } catch (InterruptedException e) {
      System.out.println(e);
    }

    System.out.println("Thread " + name + " Beginning Phase Three");
    phsr.arriveAndDeregister(); // Signal arrival and deregister.
  }
}



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