synchronized

Why is synchronized not working?

由 半腔热情 提交于 2019-12-12 16:50:27
问题 I am trying to write a method that asks a device for input and then accepts a response, all as an atomic operation. Here is my code (the query method is really what should be focused on): public class DeviceConnection implements Runnable{ //For query static int test = 0; //For writeline static PrintWriter out = null; //(initialized in constructor) //Only important for readline static String[] systemMessage=new String[10]; static int messageIn=0; static int messageOut=0; static boolean

lombok注解

由 余生颓废 提交于 2019-12-12 14:55:25
lombok注解文档 lombok官网下载 lombok介绍 lombok可以通过简单的注解的形式来帮助我们简化和消除一些必须有但显得很臃肿的Java代码，比如常见的Getter&Setter、toString()、构造函数等等。lombok不仅方便编写，同时也让我们的代码更简洁。 lombok提供了一个功能完整的jar包，可以很方便的与我们的项目进行集成。 maven依赖 <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.16.20</version> <scope>provided</scope> </dependency> lombok是一个可以帮助我们简化java代码编写的工具类，尤其是简化javabean的编写，即通过采用注解的方式，消除代码中的构造方法，getter/setter等代码，使我们写的类更加简洁，当然，这带来的副作用就是不易阅读…不过，还是能看得懂吧，废话不多说，先看一下lombok支持的一些常见的注解。 1.@NonNull 2.@Cleanup 3.@Getter/@Setter 4.@ToString 5.@EqualsAndHashCode 6.@NoArgsConstructor/

how to use a synchronized linked hash map correctly

由 元气小坏坏 提交于 2019-12-12 13:04:41
问题 trying to make an lru map by subclassing linked hash map. the map is run through collections.synchronized. all usages of the map are surrounded by a synchronized block. the unit test also fails if they are all removed. one would think they are not necessary since the map was run through collections.synchronized. one thread puts sequential numbers (0,1,2,3 ...) into the map. removals are handled by removed eldest entry. no one else removes entries from the map. the other thread gets the data

how to use lock in Julia

由 自闭症网瘾萝莉.ら 提交于 2019-12-12 09:39:14
问题 I'm working with Julia. The IDE is Juno. If I'm right, @async can generate a task, it's just like a thread. So we can do this: @async begin # do something1 end @async begin # do something2 end Now, I need to lock a thread. For example, do something1 is to push message to a list and do something2 is to pop message from the same list. It's like synchronized in Java. what is synchronized in julia? 回答1: There is also a @sync macro: help?> @sync Wait until all dynamically-enclosed uses of @async,

Do we need to use MappedByteBuffer.force() to flush data to disk?

由 丶灬走出姿态 提交于 2019-12-12 09:34:31
问题 I am using MappedByteBuffer to speed up file read/write operations(). My questions as below: I am not sure if I need to use .force() method to flush the content to disk or not. It seems like without .force(), the .getInt() can still work perfectly (well, since this is a memory-mapped buffer, i assume .getInt() fetches the data from disk, which means the data has been flushed into disk already. Is the .force() method a blocking method? Is a blocking method a synchronized block? There is a huge

Java multithreading synchronized method with two threads

由 僤鯓⒐⒋嵵緔 提交于 2019-12-12 04:59:15
问题 I have a very simple code but unable to understand. public class Test extends Thread { public synchronized void testPrint() { System.out.println("I am sleeping..." + Thread.currentThread().getName()); try { Thread.sleep(3000); System.out.println("I am done sleeping..." + Thread.currentThread().getName()); } catch (InterruptedException e) { e.printStackTrace(); } } public void run() { Test t = new Test(); t.testPrint(); System.out.println("I am out..." + Thread.currentThread().getName()); }

多线程（四） 锁 Lock

由 若如初见. 提交于 2019-12-12 04:35:37
Java中，锁的种类按照不同的维度可以区分出很多的类型，比如是否公平？可读写？可重入？等等。而本文主要介绍JUC并发包Lock接口下锁的实现，以及对常见的锁类型介绍、在实际使用中应该注意什么等。 如下图，Lock接口及实现类。 一、区分synchronized和Lock 这两者最大的区别：synchronized是Java的一个关键字，Lock是Java并发包下的一个接口。 细分两者区别： 二、Java锁机制 1、公平锁与非公平锁 回到本文的主题，Lock接口，用创建ReentrantLock实例来说明在创建一个它的一个实例对象的时候都干了什么？打开源码看看。 如上图，默认的构造方法会创建一个非公平锁，而这个锁则是继承一个叫做AbstractQueuedSynchronizer的类（简称AQS）。这个AQS类是源码作者Doug Lea大神在JUC并发包中用来构建锁或者其他同步组件（信号量、事件等）的基础框架类，毫不夸张的说只要弄懂这个同步队列的实现，基本整个JUC理解起来都不会有太大困难，等参悟透了再写文章分享。AQS是一个高度抽象的类，用于解决在多线程编程中遇到的并发同步、锁等复杂问题。首先从基础说起，公平锁和非公平锁指的是什么？ 公平锁：指的是多个线程按照申请锁的顺序来获取锁，先到先得，FIFO（First In First Out）。 非公平锁

disruptor onEvent handler appears to be too fast for java synchronized lock

由 孤街醉人 提交于 2019-12-12 03:59:30
问题 I am publishing 2 or more different events to an output disruptor at the same time (one right after the other) and the disruptor onEvent is usually sending only the last to be published event to the IO session. Basically the event data is overwritten. Whereas I want to see a copy of each event on the session layer. I have tried synchronizing the session layer on a lock but the publisher is usually still too fast even for the lock (sometimes it is working but most of the time it's not). Here's

java并发编程实战wwj----------------------第一阶段--------------27-28-29-30

由 主宰稳场 提交于 2019-12-12 02:30:07
代码：chapter9 sleep：是Threa的方法，sleep不释放锁，sleep不用synchronized，不需要被唤醒。 wait：所有对象的方法，wait释放锁 ，用synchronized，要被唤醒。 如何使用这个案例：切换m1和m2方法。 package chapter9; import java.util.stream.Stream; /*************************************** * @author:Alex Wang * @Date:2017/2/20 QQ:532500648 * QQ交流群:286081824 ***************************************/ public class DifferenceOfWaitAndSleep { private final static Object LOCK = new Object(); public static void main(String[] args) { Stream.of("T1", "T2").forEach(name -> new Thread(name) { @Override public void run() { m1(); } }.start() ); } public static void m1() {

Does Firefox synchronize requests for the same page?

由 旧街凉风 提交于 2019-12-12 01:52:41
问题 I'm using Firefox 3.6.6. I have a PHP script called index.php with the following code: <?php sleep(20); die(time()); ?> I open two browser tabs, copy the URL into each of them, and then quickly hit enter in each tab. The first tab completes in just over 20 seconds. The second tab completes in just over 40 seconds. I do the same experiment in IE and both scripts complete within a second of each other, around 20 seconds. Is this expected behavior? The actual script that caused me to test this
订阅 synchronized