业务场景描述:假设一条流水线上有三个工作者:worker1,worker2,worker3。有一个任务的完成需要他们三者协作完成,worker3可以开始这个任务的前提是worker1和worker2完成了他们的工作,而worker1和worker2是可以并行他们各自的工作的。
1.join实现
public class CountDownLatchAndJoin { public static void main(String[] args) throws InterruptedException { // 三个独立的工人线程 worker worker1 = new worker("worker1", (long) (Math.random()*4000)); worker worker2 = new worker("worker2", (long) (Math.random()*4000)); worker worker3 = new worker("worker3", (long) (Math.random()*4000)); // worker worker1 = new worker("worker1", 6000); // worker worker2 = new worker("worker2", 5000); // worker worker3 = new worker("worker3", 5000); worker1.start(); worker2.start(); worker1.join(); worker2.join(); System.out.println("准备工作就绪..."); worker3.start(); } // 工人类 public static class worker extends Thread { // 名字 private String name; //工作时间 private long time; worker(String name, long time) { this.name = name; this.time = time; } public void run() { try { System.out.println(name + "开始工作"); Thread.sleep(time); System.out.println(name + "工作完成,耗费时间=" + time); } catch (InterruptedException e) { e.printStackTrace(); } } } }
结果:
worker2开始工作 worker1开始工作 worker1工作完成,耗费时间=601 worker2工作完成,耗费时间=2886 准备工作就绪... worker3开始工作 worker3工作完成,耗费时间=686
可以顺利的完成工作,join的工作原理是,不停检查thread是否存活,如果存活则让当前线程永远wait,直到thread线程终止,线程的notifyAll就会被调用,还可以理解为join就是插队的意思