synchronization

问题 I'm trying to use the synchronization java directive to implement fine-grained synchronization in a class, i.e. synchronize the least amount of code I can.. I'll comment the code inline, to explain what I do and after the code I'll ask you how to improve the code: public class MyClass { private static volatile MyClass singletonInstance = null; private HashMap<String, Integer> mHashMap = null; private String mStringA = null; private String mStringB = null; // Use double check technique to use

问题 I am running into the issue of what to do when a user does a delete, for example, while offline? I was considering using an addedQueue, modifiedQueue, and deletedQueue, and persisting them using NSCoding and NSKeyedArchiver . Maybe I would use a Set or a Dictionary. Then I would iterate over them in the background or once every app launch, and remove from them on success. Does that sound reasonable? Does anyone have experience with this problem they can share? I've done quite a bit of

问题 I know that hundreds of variations of these considerations have been posted all over the net. However, I haven't found anything that adresses my exact problem, so I hope you can help me see the light. I'm currently toying with 2D game development in Java using OpenGL. The language and graphics library used is not that relevant to my question though as it has a more general character. I'm attempting to design a general purpose game loop which can be used more or less as is for any game that

问题 I have a program with one main thread where I spawn a second thread that uses asyncio. Are there any tools provided to synchronize these two threads? If everything was asyncio, I could do it with its synchronization primitives, eg: import asyncio async def taskA(lst, evt): print(f'Appending 1') lst.append(1) evt.set() async def taskB(lst, evt): await evt.wait() print('Retrieved:', lst.pop()) lst = [] evt = asyncio.Event() asyncio.get_event_loop().run_until_complete(asyncio.gather( taskA(lst,

问题 rephrased for clarity I would like to be able to mix the use of the synchronized block with more explicit locking via calling lock and release methods directly when appropriate. Thus allowing me the syntaxtical sugar of using sychtronized(myObject) when I can get away with it, but also being able to call myObject.lock & myObject.unlock dierctly for those times when a synchronized block is not flexible enough to do what I need done. I know that every single Object has, implicitly, a rentrant

问题 I have read that code in servlets can be synchronized with synchronized blocks. However, I have also read that whilst there is often only one instance of a servlet the servlet container may keep a pool of instances. Surely this means that a synchronized block is therefore not guaranteed to work as you don't know which instance the request thread will choose? 回答1: Section 2.2 of the specification (3.0) says: For a servlet not hosted in a distributed environment (the default), the servlet

问题 I attended an interview and I was asked to design a class for the following requirement. Assume I have a class A and it can have any number of children, i.e., subclasses. The class A has a method called doSomething() which is synchronized. The requirements are : It is mandatory that all subclasses of A override the doSomething() method. All subclasses' overriden doSomething() method must be Thread safe in nature. All subclasses' must have the provision to implement their own logic for their

问题 I'm writing conjugate-gradient method realization. I use Java multi threading for matrix back-substitution. Synchronization is made using CyclicBarrier, CountDownLatch. Why it takes so much time to synchronize threads? Are there other ways to do it? code snippet private void syncThreads() { // barrier.await(); try { barrier.await(); } catch (InterruptedException e) { } catch (BrokenBarrierException e) { } } 回答1: How many threads are being used in total? That is likely the source of your

问题 I have multiple threads writing data to a common source, and I would like two threads to block each other if and only if they are touching the same piece of data. It would be nice to have a way to lock specifically on an arbitrary key: string id = GetNextId(); AquireLock(id); try { DoDangerousThing(); } finally { ReleaseLock(id); } If nobody else is trying to lock the same key, I would expect they would be able to run concurrently. I could achieve this with a simple dictionary of mutexes, but

问题 Often after a Drupal (6.x) site is launched, I have people starting to sign up and enter their own content. Whenever there is need for an upgrade, the database on production is copied to dev and then the development is done on dev, later get pushed to staging for client's approval. When the site is eventually ready to go live, there is a problem. Production server has the latest user inputted content, dev and staging have the latest functionality. Simply overwriting the database on production