Phaser是并发包juc.concurrent包下的一个关于线程同步和线程通信的一个工具类，类似于CountDownLanch 和 CyclicBarrier，不同的是
Phaser可以用来根据步骤，等待线程按步骤同时触发执行。

package com.example.test;import com.example.abstractClass.B;import java.util.concurrent.Phaser;public class A extends B {void a2() {super.a();}public static void main(String[] args) {// Phaser 参数为：维护线程个数Phaser phaser = new Phaser(10) {@Overrideprotected boolean onAdvance(int phase, int registeredParties) {System.out.println("phase: " + phase+ " registeredParties: " + registeredParties);return phase == 10;}};for (int i = 0; i < 10; i++) {Thread thread = new Thread(new C(phaser), "Thread" + i);thread.start();}}
}class C implements Runnable {private Phaser phaser;public C(Phaser phaser) {this.phaser = phaser;}@Overridepublic void run() {System.out.println(Thread.currentThread().getName() + " do something 1 ");phaser.arriveAndAwaitAdvance();System.out.println(Thread.currentThread().getName() + " do something 2 ");phaser.arriveAndAwaitAdvance();System.out.println(Thread.currentThread().getName() + " do something 3 ");phaser.arriveAndAwaitAdvance();System.out.println(Thread.currentThread().getName() + " do something 4 ");phaser.arriveAndAwaitAdvance();System.out.println(Thread.currentThread().getName() + " do something 5 ");phaser.arriveAndAwaitAdvance();System.out.println(Thread.currentThread().getName() + " do something 6 ");phaser.arriveAndAwaitAdvance();}
}

打印查看：

Phaser的 onAdvance(int phase, int registeredParties) 方法phase指的是 phaser.arriveAndAwaitAdvance() 方法执行的次数，在创建Phaser的构造参数中，入参指的是参与维护线程的数量；