Phaser 介绍及应用详解

??Phaser是JDK提供的同步辅助类，用来解决多线程间分阶段同步完成任务的工具类。其和CountDownLatch、CyclicBarrier功能类似，但Phaser提供了更加丰富的功能，使用上更加灵活。

??演示示例：

package com.securitit.serialize.juc;import java.util.Date;
import java.util.concurrent.Phaser;import org.assertj.core.util.DateUtil;public class PhaserTester {
    private static final Phaser phaser = new Phaser(3);public static void main(String[] args) throws Exception {
    new Thread(() -> {
    try {
    Thread.sleep(5000);phaser.arriveAndAwaitAdvance();System.out.println(DateUtil.formatAsDatetime(new Date()) + " " + Thread.currentThread().getName() + " 线程集合点A.");Thread.sleep(1000);phaser.arriveAndAwaitAdvance();System.out.println(DateUtil.formatAsDatetime(new Date()) + " " + Thread.currentThread().getName() + " 线程集合点B.");} catch (Exception ex) {
    ex.printStackTrace();} }).start();new Thread(() -> {
    try {
    Thread.sleep(2000);phaser.arriveAndAwaitAdvance();System.out.println(DateUtil.formatAsDatetime(new Date()) + " " + Thread.currentThread().getName() + " 线程集合点A.");Thread.sleep(2000);phaser.arriveAndAwaitAdvance();System.out.println(DateUtil.formatAsDatetime(new Date()) + " " + Thread.currentThread().getName() + " 线程集合点B.");} catch (Exception ex) {
    ex.printStackTrace();} }).start();new Thread(() -> {
    try {
    Thread.sleep(1000);phaser.arriveAndAwaitAdvance();System.out.println(DateUtil.formatAsDatetime(new Date()) + " " + Thread.currentThread().getName() + " 线程集合点A.");Thread.sleep(5000);phaser.arriveAndAwaitAdvance();System.out.println(DateUtil.formatAsDatetime(new Date()) + " " + Thread.currentThread().getName() + " 线程集合点B.");} catch (Exception ex) {
    ex.printStackTrace();} }).start();}}

??输出结果：

2020-06-27T15:16:52 Thread-0 线程集合点A.
2020-06-27T15:16:52 Thread-1 线程集合点A.
2020-06-27T15:16:52 Thread-2 线程集合点A.
2020-06-27T15:16:57 Thread-2 线程集合点B.
2020-06-27T15:16:57 Thread-0 线程集合点B.
2020-06-27T15:16:57 Thread-1 线程集合点B.

??从结果可以看出，arriveAndAwaitAdvance可以实现线程协作，完成线程集合等功能。