concurrency

问题 In a hashmap, when we have the same hashcodes, we insert objects as a linked list which are later converted to TreeNode. Every New object with the same hashcode is added to the last of the linked list attached. So, my question here is why don't we add the new element as first element of the internal linked list attached to the bucket? Why do we traverse till the last element, and then add the new element. Time taken by Linked list to: Insert New element at start = O(1) Insert New element at

问题 On collection, the garbage collector copies all live objects into another memory space, thus discarding all garbage objects in the process. A forward pointer to the copied object in new space is installed into the 'old' version of an object to ensure the collector updates all remaining references to the object correctly and doesn't erroneously copy the same object twice. This obviously works quite well for stop-the-world-collectors. However, since pause times are long with stop-the-world,

问题 We have a multiuser system with users saving to a central SQL Server 2005 database. We have encountered an issue where a user refreshes in changes from the db while another user saves new data. The way we are currently collecting the changes is we have a timestamp column on each table which is filled at every row insert/update. Another user will have a timestamp stored on the client which is the last time he did a pull from the database. Each save is done in a transaction. The example we are

问题 We have a multiuser system with users saving to a central SQL Server 2005 database. We have encountered an issue where a user refreshes in changes from the db while another user saves new data. The way we are currently collecting the changes is we have a timestamp column on each table which is filled at every row insert/update. Another user will have a timestamp stored on the client which is the last time he did a pull from the database. Each save is done in a transaction. The example we are

问题 I've found in Akka docs: When using future callbacks, such as onComplete, onSuccess, and onFailure, inside actors you need to carefully avoid closing over the containing actor’s reference, i.e. do not call methods or access mutable state on the enclosing actor from within the callback. So does it mean that i should always use future pipeTo self and then call some functions? Or i can still use callbacks with method, then how should i avoid concurrency bugs? 回答1: It means this: class

问题 I've found in Akka docs: When using future callbacks, such as onComplete, onSuccess, and onFailure, inside actors you need to carefully avoid closing over the containing actor’s reference, i.e. do not call methods or access mutable state on the enclosing actor from within the callback. So does it mean that i should always use future pipeTo self and then call some functions? Or i can still use callbacks with method, then how should i avoid concurrency bugs? 回答1: It means this: class

问题 I've found in Akka docs: When using future callbacks, such as onComplete, onSuccess, and onFailure, inside actors you need to carefully avoid closing over the containing actor’s reference, i.e. do not call methods or access mutable state on the enclosing actor from within the callback. So does it mean that i should always use future pipeTo self and then call some functions? Or i can still use callbacks with method, then how should i avoid concurrency bugs? 回答1: It means this: class

问题 I have a method which takes an IList<> and adds stuff to it. I would like to pass it a ConcurrentBag in some cases, but it doesn't implement IList<> or ICollection<>, only the non-generic ICollection, which doesn't have an Add method. Now, I see why it can't (maybe) implement IList - it's not an ordered collection so it won't make sense for it to have an indexer. But I don't see an issue with any of the ICollection<> methods. So, why? And, also - is there a thread-safe collection in .NET that

问题 In a JavaFX application I wish to update a status bar according to some work logic which I've implemented in an other class. I can't figure out how to combine my desire to pass to work logic to the method (and not to write it inside the task) and to know about the work progress percentage. This is an example of the controller with the Task: public class FXMLDocumentController implements Initializable { @FXML private Label label; @FXML ProgressBar progressBar; @FXML private void

问题 In a JavaFX application I wish to update a status bar according to some work logic which I've implemented in an other class. I can't figure out how to combine my desire to pass to work logic to the method (and not to write it inside the task) and to know about the work progress percentage. This is an example of the controller with the Task: public class FXMLDocumentController implements Initializable { @FXML private Label label; @FXML ProgressBar progressBar; @FXML private void