Java如何使用Phaser实现多阶段任务同步_Java并发协调控制机制分析

import java.util.concurrent.Phaser;

public class MultiStageTask {
    public static void main(String[] args) {
        Phaser phaser = new Phaser(3); // 初始3个参与者

        for (int i = 1; i <= 3; i++) {
            new Thread(new Worker(phaser, "Worker-" + i)).start();
        }
    }

    static class Worker implements Runnable {
        private final Phaser phaser;
        private final String name;

        Worker(Phaser phaser, String name) {
            this.phaser = phaser;
            this.name = name;
        }

        @Override
        public void run() {
            int phase;

            // 阶段1：准备
            System.out.println(name + " 开始准备工作");
            sleep(500);
            phase = phaser.arriveAndAwaitAdvance();
            System.out.println(name + " 完成准备，进入阶段 " + (phase + 1));

            // 阶段2：加工
            System.out.println(name + " 开始加工任务");
            sleep(700);
            phase = phaser.arriveAndAwaitAdvance();
            System.out.println(name + " 完成加工，进入阶段 " + (phase + 1));

            // 阶段3：收尾
            System.out.println(name + " 进行收尾工作");
            sleep(400);
            phaser.arriveAndAwaitAdvance(); // 最后一阶段无需再继续
            System.out.println(name + " 任务结束");
        }

        private void sleep(long ms) {
            try {
                Thread.sleep(ms);
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        }
    }
}

// 在某个阶段后动态添加参与者
phaser.register();
new Thread(() -> {
    System.out.println("质检员加入");
    phaser.arriveAndAwaitAdvance(); // 等待当前阶段结束
    System.out.println("质检员检查完成");
    phaser.arriveAndDeregister();  // 检查完退出
}).start();

// 工人完成前两个阶段后退出
phaser.arriveAndAwaitAdvance(); // 第一阶段
phaser.arriveAndAwaitAdvance(); // 第二阶段
phaser.arriveAndDeregister();   // 不再参与后续阶段
System.out.println(name + " 提前离场");

Phaser phaser = new Phaser(3) {
    @Override
    protected boolean onAdvance(int phase, int registeredParties) {
        System.out.println("▶ 阶段 " + phase + " 完成，当前参与者：" + registeredParties);
        return phase >= 2 || registeredParties == 0; // 执行完第3阶段后停止
    }
};