countdownlatch

How is CountDownLatch used in Java Multithreading?

由 安稳与你 提交于 2019-11-26 12:39:24
Can someone help me to understand what Java CountDownLatch is and when to use it? I don't have a very clear idea of how this program works. As I understand all three threads start at once and each Thread will call CountDownLatch after 3000ms. So count down will decrement one by one. After latch becomes zero the program prints "Completed". Maybe the way I understood is incorrect. import java.util.concurrent.CountDownLatch; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; class Processor implements Runnable { private CountDownLatch latch; public Processor

JAVA栅栏和闭锁的区别

由 末鹿安然 提交于 2019-11-26 11:16:25
　　闭锁： 一个同步辅助类，在完成一组正在其他线程中执行的操作之前，它允许一个或多个线程一直等待。即，一组线程等待某一事件发生，事件没有发生前，所有线程将阻塞等待；而事件发生后，所有线程将开始执行；闭锁最初处于封闭状态，当事件发生后闭锁将被打开，一旦打开，闭锁将永远处于打开状态。 　　闭锁 CountDownLatch 唯一的构造方法 CountDownLatch(int count) ，当在闭锁上调用 countDown () 方法时，闭锁的计数器将减1，当闭锁计数器为0时，闭锁将打开，所有线程将通过闭锁开始执行。 　　栅栏： 一个同步辅助类，它允许一组线程互相等待，直到到达某个公共屏障点。利用栅栏，可以使线程相互等待，直到所有线程都到达某一点，然后栅栏将打开，所有线程将通过栅栏继续执行。 CyclicBarrier 支持一个可选的 Runnable 参数 ，当线程通过栅栏时，runnable对象将被调用。构造函数 CyclicBarrier(int parties , Runnable barrierAction ) ，当线程在 CyclicBarrier 对象上调用 await() 方法时，栅栏的计数器将增加1，当计数器为 parties 时，栅栏将打开。 　　区别： 闭锁用于所有线程等待一个外部事件的发生；栅栏则是所有线程相互等待，直到所有线程都到达某一点时才打开栅栏

Java concurrency: Countdown latch vs Cyclic barrier

由 核能气质少年 提交于 2019-11-26 10:06:01
问题 I was reading through the java.util.concurrent API, and found that CountDownLatch : A synchronization aid that allows one or more threads to wait until a set of operations being performed in other threads completes. CyclicBarrier : A synchronization aid that allows a set of threads to all wait for each other to reach a common barrier point. To me both seems equal, but I am sure there is much more to it. For example, in CoundownLatch, the countdown value could not be reset, that can happen in

CountDownLatch vs. Semaphore

由 假装没事ソ 提交于 2019-11-26 08:42:41
问题 Is there any advantage of using java.util.concurrent.CountdownLatch instead of java.util.concurrent.Semaphore? As far as I can tell the following fragments are almost equivalent: 1. Semaphore final Semaphore sem = new Semaphore(0); for (int i = 0; i < num_threads; ++ i) { Thread t = new Thread() { public void run() { try { doStuff(); } finally { sem.release(); } } }; t.start(); } sem.acquire(num_threads); 2: CountDownLatch final CountDownLatch latch = new CountDownLatch(num_threads); for (int

Java 操作zookeeper

由 孤街醉人 提交于 2019-11-26 03:52:26
1,windows 下的zookeeper 单机启动，双击就可以启动了，路径必须是英文路径，启动之后 启动完成，如下图，默认端口2181 2，windows 下的图形化工具，连接zookeeper的客户端 双击打开： 可以在客户端增添节点 3，通过java 代码操作zookeeper package com.aiyuesheng.utils; import java.io.IOException; import java.util.concurrent.CountDownLatch; import org.apache.zookeeper.CreateMode; import org.apache.zookeeper.KeeperException; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.Watcher.Event.EventType; import org.apache.zookeeper.Watcher.Event.KeeperState; import org.apache.zookeeper.ZooKeeper; import org.apache.zookeeper.ZooDefs.Ids;

How is CountDownLatch used in Java Multithreading?

由 允我心安 提交于 2019-11-26 02:27:09
问题 Can someone help me to understand what Java CountDownLatch is and when to use it? I don\'t have a very clear idea of how this program works. As I understand all three threads start at once and each Thread will call CountDownLatch after 3000ms. So count down will decrement one by one. After latch becomes zero the program prints \"Completed\". Maybe the way I understood is incorrect. import java.util.concurrent.CountDownLatch; import java.util.concurrent.ExecutorService; import java.util

Java ThreadPoolExecutor线程池概述

由 柔情痞子 提交于 2019-11-26 01:27:50
导航 前言 为什么要使用线程池 线程池使用方式 Executors创建线程池 newCachedThreadPool newFixedThreadPool newScheduledThreadPool newSingleThreadExecutor 四种线程池对比 ThreadPoolExecutor创建线程池 排队策略 工作队列对比 线程池关闭 线程池大小设置 线程池的状态监控 结语 前言 在互联网的开发场景下，很多业务场景下我们需要使用到多线程的技术，从 Java 5 开始，Java 提供了自己的线程池，线程池就是一个线程的容器，每次只执行额定数量的线程。java.util.concurrent包中提供了ThreadPoolExecutor类来管理线程，本文将介绍一下ThreadPoolExecutor类的使用。 为什么要使用线程池？ 在执行一个异步任务或并发任务时，往往是通过直接new Thread()方法来创建新的线程，这样做弊端较多，更好的解决方案是合理地利用线程池，线程池的优势很明显，如下： 降低系统资源消耗，通过重用已存在的线程，降低线程创建和销毁造成的消耗； 提高系统响应速度，当有任务到达时，无需等待新线程的创建便能立即执行； 方便线程并发数的管控，线程若是无限制的创建，不仅会额外消耗大量系统资源，更是占用过多资源而阻塞系统或oom等状况，从而降低系统的稳定性
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