concurrency

问题 java.util.ConcurrentModificationException at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372) at java.util.AbstractList$Itr.next(AbstractList.java:343) at com.alpha.beta.purchasing.item.VendorItemList.loadItems(VendorItemList.java:51) at com.alpha.beta.purchasing.Shipment.loadItems(Shipment.java:1006) at com.alpha.beta.purchasing.Shipment.loadItems(Shipment.java:953) at com.alpha.beta.purchasing.Shipment.getItemTotal(Shipment.java:1503) at com.alpha.beta.purchasing

问题 In java I'm use to do following: boolean done = false; while(!done) { Long oldValue = map.putIfAbsent(key, 1L); if(oldValue != null) { done = map.replace(key, oldValue, oldValue + 1); } else { done = true; } } now i see that in scala I'm better off using TrieMap (if i insist on the mutable version) i don't really understand if there is a one shot operation already exists in this TrieMap which will do this while loop for me, if yes can you please show an example? 回答1: Be careful with TrieMap

问题 In java I'm use to do following: boolean done = false; while(!done) { Long oldValue = map.putIfAbsent(key, 1L); if(oldValue != null) { done = map.replace(key, oldValue, oldValue + 1); } else { done = true; } } now i see that in scala I'm better off using TrieMap (if i insist on the mutable version) i don't really understand if there is a one shot operation already exists in this TrieMap which will do this while loop for me, if yes can you please show an example? 回答1: Be careful with TrieMap

问题 I am following Java Concurrency in Practice , and when I read about stack confinement I felt good because it explained very well, but this statement raised some doubts for me: Maintaining stack confinement for object references requires a little more assistance from the programmer to ensure that the referent does not escape Can anyone do something in below code to produce a violation of stack confinement? I guess it has no confinement violation at present. I want to know how local object

问题 I'm trying to use Java 8's parallelStream() to execute several long-running requests (eg web requests) in parallel. Simplified example: List<Supplier<Result>> myFunctions = Arrays.asList(() -> doWebRequest(), ...) List<Result> results = myFunctions.parallelStream().map(function -> function.get()).collect(... So if there are two functions that block for 2 and 3 seconds respectively, I'd expect to get the result after 3 seconds. However, it really takes 5 seconds - ie it seems the functions are

问题 Lest I provide an XY problem, my goal is to share a memory-mapped file between multiple goroutines as recommended. Each goroutine needs to iterate over the file line by line so I had hoped to store the complete contents in memory first to speed things up. The method I tried is passing a pointer to a bufio.Scanner , but that is not working. I thought it might be related to needing to set the seek position back to the beginning of the file but it is not even working the very first time and I

问题 Reading a very interesting blog post by Dan Luu about advances in x86 architecture over the past few decades, he says: If we set _foo to 0 and have two threads that both execute incl (_foo) 10000 times each, incrementing the same location with a single instruction 20000 times, is guaranteed not to exceed 20000, but it could (theoretically) be as low as 2. If it’s not obvious why the theoretical minimum is 2 and not 10000, figuring that out is a good exercise. where _foo is some memory address

问题 First of all I'd welcome edits to the title of this question, I couldn't think how to word it better but I'm not too happy with what I came up with. This is a question about concurrency, my application is on a microcontroller in C but I don't think that matters a great deal. I have an interrupt routine which can change the values of two global variables. I have some main code which can read those variables. But it must get get consistent values from both which means I can't read one and then

问题 First of all I'd welcome edits to the title of this question, I couldn't think how to word it better but I'm not too happy with what I came up with. This is a question about concurrency, my application is on a microcontroller in C but I don't think that matters a great deal. I have an interrupt routine which can change the values of two global variables. I have some main code which can read those variables. But it must get get consistent values from both which means I can't read one and then

问题 I'm trying to pull my own flavor of the usual UITableView + async download + cache technique. What I'm doing is, for each cell that gets dequeued in cellForRowAtIndexPath: 1-Check if it's corresponding thumbnail image is already 'cached' in /Library/Caches 2-If it is, just use that. 3-If not, load a default image and enqueue an NSInvocationOperation to take care of it: 4a-The NSInvocationOperation gets the image from a remote server 4b-Does the UIGraphicsBeginContext thing to scale down the