synchronization

问题 I know that using the synchronize keyword before a method brings synchronization to that object. That is, 2 threads running the same instance of the object will be synchronized. However, since the synchronization is at the object level, 2 threads running different instances of the object will not be synchronized. If we have a static variable in a Java class that is called by the method, we would like it to be synchronized across instances of the class. The two instances are running in 2

问题 I\'m new to multithreading, and was trying to understand how mutexes work. Did a lot of Googling and I found a decent tutorial, but it still left some doubts of how it works because I created my own program in which locking didn\'t work. One absolutely non-intuitive syntax of the mutex is pthread_mutex_lock( &mutex1 ); , where it looks like the mutex is being locked, when what I really want to lock is some other variable. Does this syntax mean that locking a mutex locks a region of code until

问题 After updating Android Studio and Gradle to 3.5, I now get this error: NDK Resolution Outcome: Project settings: Gradle model version=5.4.1, NDK version is UNKNOWN I changed the Gradle version in build-gradle back to 3.4.2 but it didn\'t help. 回答1: I had similar problem and solved it by opening project using Import project (Gradle, Eclipse, etc.) instead of Open existing Android Studio project . 回答2: You can download NDK from File>Project Structur>Choosing SDK location from left panel and

问题 I have an ArrayList that I want to use to hold RaceCar objects that extend the Thread class as soon as they are finished executing. A class, called Race, handles this ArrayList using a callback method that the RaceCar object calls when it is finished executing. The callback method, addFinisher(RaceCar finisher), adds the RaceCar object to the ArrayList. This is supposed to give the order in which the Threads finish executing. I know that ArrayList isn\'t synchronized and thus isn\'t thread

问题 I have two threads, one updating an int and one reading it. This is a statistic value where the order of the reads and writes is irrelevant. My question is, do I need to synchronize access to this multi-byte value anyway? Or, put another way, can part of the write be complete and get interrupted, and then the read happen. For example, think of a value = 0x0000FFFF that gets incremented value of 0x00010000. Is there a time where the value looks like 0x0001FFFF that I should be worried about?

问题 Does @synchronized not use \"lock\" and \"unlock\" to achieve mutual exclusion? How does it do lock/unlock then? The output of the following program is only \"Hello World\". @interface MyLock: NSLock<NSLocking> @end @implementation MyLock - (id)init { return [super init]; } - (void)lock { NSLog(@\"before lock\"); [super lock]; NSLog(@\"after lock\"); } - (void)unlock { NSLog(@\"before unlock\"); [super unlock]; NSLog(@\"after unlock\"); } @end int main (int argc, const char * argv[]) {

问题 If I have a util class with static methods that will call Hibernate functions to accomplish basic data access. I am wondering if making the method synchronized is the right approach to ensure thread-safety. I want this to prevent access of info to the same DB instance. However, I\'m now sure if the following code are preventing getObjectById being called for all Classes when it is called by a particular class. public class Utils { public static synchronized Object getObjectById (Class

问题 I see that for using objects which are not thread safe we wrap the code with a lock like this: private static readonly Object obj = new Object(); lock (obj) { // thread unsafe code } So what happens when multiple threads access the same code (let\'s assume that it is running in a ASP.NET web application). Are they queued? If so how long will they wait? What is the performance impact because of using locks? 回答1: The lock statement is translated by C# 3.0 to the following: var temp = obj;

问题 Is it true that C++0x will come without semaphores? There are already some questions on Stack Overflow regarding the use of semaphores. I use them (posix semaphores) all the time to let a thread wait for some event in another thread: void thread0(...) { doSomething0(); event1.wait(); ... } void thread1(...) { doSomething1(); event1.post(); ... } If I would do that with a mutex: void thread0(...) { doSomething0(); event1.lock(); event1.unlock(); ... } void thread1(...) { event1.lock();

问题 I need to store the result of FireBase getValue method that is async by his own. I can\'t use something like \"onPostExecute()\" and, for my purpose, i can\'t execute all my operation \"into onDataChange()\" because i need some references in future time in other activities. Here my snippet to retrieve data: List<Village> villages = new LinkedList<>(); Firebase ref = new Firebase(\"MYFIREBASEURL\").child(\"village\"); ref.addValueEventListener(new ValueEventListener() { @Override public void