notify

I learned that calling an Object's wait() method will release the object monitor, if present. But I have some questions regarding calling notify() on this object by another thread: (when) will the waiting thread wake up, if another (a 3rd) thread owns the object monitor in the meanwhile? will the waiting thread wake up, if a 3rd thread called wait() on this object? is it possible to determine if a thread is waiting for notifying a particular object (java 1.4/java 5) What's happening if wait() will be called in the finalize() method? notify will wake one thread waiting on the monitor. Unless

A thread can use Object.wait() to block until another thread calls notify() or notifyAll() on that object. But what if a thread wants to wait until one of multiple objects is signaled? For example, my thread must wait until either a) bytes become available to read from an InputStream or b) an item is added to an ArrayList . How can the thread wait for either of these events to occur? EDIT This question deals with waiting for multiple threads to complete -- my case involves a thread waiting for one of many objects to be singnaled. sgokhales A thread cannot wait on more than one object at a time

I have the code to fire a trigger only on an update of a single specific column. The trigger is used to fire a function that will raise a postgres "notify" event, which I am listening for and will need to test and validate the newly input details. There are many values on the account_details table which could be change which do not require an account validate, so a trigger on AFTER UPDATE only (without a when) is no good. CREATE TRIGGER trigger_update_account_details AFTER UPDATE ON account_details FOR EACH ROW WHEN (OLD.email IS DISTINCT FROM NEW.email) EXECUTE PROCEDURE notify_insert_account

Every Java Object has the methods wait() and notify() (and additional variants). I have never used these and I suspect many others haven't. Why are these so fundamental that every object has to have them and is there a performance hit in having them (presumably some state is stored in them)? EDIT to emphasize the question. If I have a List<Double> with 100,000 elements then every Double has these methods as it is extended from Object . But it seems unlikely that all of these have to know about the threads that manage the List . EDIT excellent and useful answers. @Jon has a very good blog post

notify()与notifyAll()都是Object对象用于通知处在等待该对象的线程的方法。两者最大的区别在于： notifyAll使所有原来在该对象上等待被notify的线程统统退出wait的状态，变成等待该对象上的锁，一旦该对象被解锁，他们就会去竞争。 notify则文明得多他只是选择一个wait状态线程进行通知，并使它获得该对象上的锁，但不惊动其他同样在等待被该对象notify的线程们，当第一个线程运行完毕以后释放对象上的锁此时如果该对象没有再次使用notify语句，则即便该对象已经空闲，其他wait状态等待的线程由于没有得到该对象的通知，继续处在wait状态，直到这个对象发出一个notify或notifyAll，它们等待的是被notify或notifyAll，而不是锁。 简单点来说就是，notifyAll()使所有在wait状态下的线程进入ready状态，当可以执行时一起竞争CPU的时间片。而notify()则是随机使所有处于wait状态线程的其中之一进入ready状态，当可以执行时获取CPU的时间片，剩下的处于wait状态的线程仍然处于wait状态。 来源： oschina 链接： https://my.oschina.net/u/2314763/blog/737120

First thing i think i should say is that i am not looking for a solution , this is hwk , but it runs correctly , what would help me greatly is come clarification.. We were just introduce to threads in my object oriented programing class , and received an assignment , which I completed. In my code I never call notifyAll() , but it seems as though it is called implicitly before exiting the run(). Another classmate of mine had the same question. I read somewhere that a Thread that is waiting on another Thread is notified ( implicit notifyAll() ?) when the thread it is waiting on dies/exits the

I have an android application that is connected to the computer via USB cable. I use a TCPServer Class to send messages and listen. For example: When I send a message like: request:x I get the response: response:x:55 I need to make changes on my activity according to the response I get. At the moment I temporarily solved the problem by passing activity and activity class object to the TCPServer's constructor public TCPServer(int portNum, Activity activity, IntroActivity ia) { super(); port = portNum; this.activity = activity; this.ia = ia; } Then after I receive the response: void updateButton