notify

在多线程的情况下，由于同一进程的多个线程共享同一片存储空间，在带来方便的同时，也带来了访问冲突这个严重的问题。Java语言提供了专门机制以解决这种冲突，有效避免了同一个数据对象被多个线程同时访问。 wait与notify是java同步机制中重要的组成部分。结合与synchronized关键字使用，可以建立很多优秀的同步模型。 synchronized(this){ }等价于publicsynchronized void method(){.....} 同步分为类级别和对象级别，分别对应着类锁和对象锁。类锁是每个类只有一个，如果static的方法被synchronized关键字修饰，则在这个方法被执行前必须获得类锁；对象锁类同。 首先，调用一个Object的wait与notify/notifyAll的时候，必须保证调用代码对该Object是同步的，也就是说必须在作用等同于synchronized(obj){......}的内部才能够去调用obj的wait与notify/notifyAll三个方法，否则就会报错： java.lang.IllegalMonitorStateException:current thread not owner 在调用wait的时候，线程自动释放其占有的对象锁，同时不会去申请对象锁。当线程被唤醒的时候，它才再次获得了去获得对象锁的权利。 所以

Java是第一个内置对多线程支持的主流编程语言。在Java5之前，对多线程的支持主要是通过对块结构的同步实现的（synchronized配合wait，notify，notifyAll），Java5引入了java.util.concurrent包，提供了对多线程编程的更高层的支持。 在Java中，除了int等基本类型之外，一切皆为对象。synchronized关键字以及Object类中的wait，notify和notifyAll方法为我们编写多线程程序提供了原始的支持。 例如： public class A { public synchronized void fun() { ... } } 在调用方法fun之前，调用该方法的执行线程必须要先获得类A的实例（a）的对象锁。上面的方法fun在功能上等同于： public void fun() { synchronized(this) { ... } } 在执行fun之前，要获取a的对象锁，在方法fun返回之前，要释放a的对象锁。 通常可以使用synchronized和notify，notifyAll以及wait方法来实现线程之间的数据传递及控制。对于对象obj来说： obj.wait()：该方法的调用，使得调用该方法的执行线程（T1）放弃obj的对象锁并阻塞，直到别的线程调用了obj的notifyAll方法

I have a activity that extends listactivity, extended in this class i have a class that extends baseadapter. now in my listactivity i have this onCreate /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setListAdapter(new BuildingAdapter(this)); final ProgressDialog loading = new ProgressDialog(this); loading.setProgressStyle(ProgressDialog.STYLE_SPINNER); loading.setTitle("Laddar"); loading.setMessage("Hämtar data från servern"); loading.show(); new AsyncTask<Void, Void, DataPacket.Data>() {

Imagine you have a typical producer-consumer pattern in Java. To be a bit more efficient you want to use notify() and not notifyAll() when a new element is added to the queue. If two producer threads invoke notify, is it guaranteed that two distinct waiting consumer threads will be awoken? Or can it be that two notify() s fired shortly after each other cause the same comsumer thread to be queued for wakeup twice? I can't find the section is the API describing how this exactly works. Does java have some atomic internal operation for waking up threads exactly once? If only one comsumer is

For example. I have a database upgrade script for adding a column to a database table. It looks a little like this: IF NOT Exists(SELECT * FROM SysColumns sc, SysObjects so WHERE sc.Name = 'dealer_number' AND so.Name = 'collector' AND so.Type= 'U' AND so.id = sc.id) BEGIN -- SQL for creating column END ELSE BEGIN -- notify user that column already exists END How do I notify the user that the column already exists? RAISERROR ('column already exists',0,1) with nowait or print 'column already exists' you can use PRINT statement in SQL RAISERROR seems appropriate here. See here . Use PRINT - it

Hello, I am trying to learn Twilio API. When I [send SMS through php][1] script.. twilio returns a response object with status = 'queued'. Now I want to get notified when the status changes to 'sent'. Is this possible with Twilio??? and if yes then could any body advise me on how to implement his. And how to add 'StatusCallback' url $sms = $client->account->sms_messages->create( // the number we are sending from, must be a valid Twilio number "000-000-0000", // the number we are sending to - Any phone number "0000000000", // the sms body "Hey Friend, Monkey Party at 6PM. Bring Bananas!" ); You

I am working on the application (C# 2.0). I have implemented single instance in it. Everything is fine. If i run the application again, it shows messagebox saying "instance is already running". Actually i don't want to show the message through messagebox. I want to show this message using Balloon tip of already running instance (it has notify icon in system tray). How can i achieve this? Thanks in advance. You need a form of interprocess communication , to signal to the other instance that it should display the messagebox. In this instance, you could go one better than telling the existing