synchronization

问题 UPDATE: Solution right after question. Question: Usually, synchronization is serializing parallel requests within a JVM, e.g. private static final Object LOCK = new Object(); public void doSomething() { ... synchronized(LOCK) { ... } ... } When looking at web applications, some synchronization on "JVM global" scope is maybe becoming a performance bottleneck and synchronization only within the scope of the user's HttpSession would make more sense. Is the following code a possibility? I doubt

问题 This question already has answers here : Java: System.out.println and System.err.println out of order (7 answers) Closed 6 years ago . Please consider this java code: public class CMain { public static void main(String[] args){ for (int i = 0; i < 10; i++) { System.out.println("A"); System.err.println("B"); } } } By a quick look at the code, some of us may think the output has to be the print of As and Bs alternatively. However is not! It is a random appearance of 10 A characters and 10 B

问题 What are the exact differences between implicitwait() , explicitwait() and fluentwait() ? Could you explain with examples? 回答1: I posted a blog article about this, and I think I provide a few very details that these other answers missed. Implicit Wait: During an Implicit wait, if the Web Driver cannot find it immediately because of its availability, the WebDriver will periodically poll the DOM ( at an interval of 0.5 seconds or depending on the driver-browser implementation ) until the

问题 consider this function : func doAllWork() error { var wg sync.WaitGroup wg.Add(3) for i := 0; i < 2; i++ { go func() { defer wg.Done() for j := 0; j < 10; j++ { result, err := work(j) if err != nil { // can't use `return err` here // what sould I put instead ? os.Exit(0) } } }() } wg.Wait() return nil } In each goroutine, the function work() is called 10 times. If one call to work() returns an error in any of the running goroutines, I want all the goroutines to stop immediately, and the

问题 This code selects all xml files in the same folder, as the invoked executable and asynchronously applies processing to each result in the callback method (in the example below, just the name of the file is printed out). How do I avoid using the sleep method to keep the main method from exiting? I have problems wrapping my head around channels (I assume that's what it takes, to synchronize the results) so any help is appreciated! package main import ( "fmt" "io/ioutil" "path" "path/filepath"

问题 This code selects all xml files in the same folder, as the invoked executable and asynchronously applies processing to each result in the callback method (in the example below, just the name of the file is printed out). How do I avoid using the sleep method to keep the main method from exiting? I have problems wrapping my head around channels (I assume that's what it takes, to synchronize the results) so any help is appreciated! package main import ( "fmt" "io/ioutil" "path" "path/filepath"

问题 I have always thought that synchronizing the run method in a java class which implements Runnable is redundant. I am trying to figure out why people do this: public class ThreadedClass implements Runnable{ //other stuff public synchronized void run(){ while(true) //do some stuff in a thread } } } It seems redundant and unnecessary since they are obtaining the object's lock for another thread. Or rather, they are making explicit that only one thread has access to the run() method. But since

问题 This question already has answers here : Closed 8 years ago . Possible Duplicate: What are the differences between various threading synchronization options in C#? What is the difference between a Monitor and a Mutex in C#? When to use a Monitor and when to use a Mutex in C#? 回答1: A Monitor is managed, and more lightweight - but is restricted to your AppDomain . A Mutex can be named, and can span processes (allowing some simple IPC scenarios between applications), and can be used in code that

问题 When should one use a semaphore and when should one use a conditional variable (CondVar) ? 回答1: Locks are used for mutual exclusion. When you want to ensure that a piece of code is atomic, put a lock around it. You could theoretically use a binary semaphore to do this, but that's a special case. Semaphores and condition variables build on top of the mutual exclusion provide by locks and are used for providing synchronized access to shared resources. They can be used for similar purposes. A

问题 List<String> list = Collections.synchronizedList(new ArrayList<String>()); synchronized (list) { list.add("message"); } Is the block "synchronized (list){} " really need here ? 回答1: You don't need to synchronize as you put in your example. HOWEVER, very important, you need to synchronize around the list when you iterate it (as noted in the Javadoc): It is imperative that the user manually synchronize on the returned list when iterating over it: List list = Collections.synchronizedList(new