synchronization

问题 This is my Java 1.6 class: public class Foo { private ArrayList<String> names; public void scan() { if (names == null) { synchronized (this) { this.names = new ArrayList<String>(); // fill the array with data } } } } Findbugs says: Inconsistent synchronization of com.XXX.Foo.names; locked 40% of time What does it mean and what I'm doing wrong? I'm trying to avoid problems when two or more clients call Foo.scan() at the same time. 回答1: It's beacuse you are only synchronizing when you set the

问题 This is my Java 1.6 class: public class Foo { private ArrayList<String> names; public void scan() { if (names == null) { synchronized (this) { this.names = new ArrayList<String>(); // fill the array with data } } } } Findbugs says: Inconsistent synchronization of com.XXX.Foo.names; locked 40% of time What does it mean and what I'm doing wrong? I'm trying to avoid problems when two or more clients call Foo.scan() at the same time. 回答1: It's beacuse you are only synchronizing when you set the

问题 I get the exact same error as #62999928, but not with the same configuration. I'm just trying to access a global Realm file which is on my Realm Cloud (I am NOT on MongoDB and the beta). I get the “Operation canceled” Realm Error Domain=io.realm.unknown Code=89 error when I try to open the Realm. Realm Studio: Opening code: let url = URL(string: "realms://\(MY_INSTANCE_ADDRESS)/common")! let config = user.configuration(realmURL: url, fullSynchronization: true) Realm.asyncOpen(configuration:

问题 I have a java.util.HashMap object. I guarantee that writing to HashMap is done by single dedicated thread. However, reading from the same HashMap object can be done from more that one thread at the time. Can I run in any troubles with such implementation? 回答1: Yes, you can run into big troubles with such an implementation! Adding a value to the HashMap is not an atomic operation. So if you read the map from another thread you might see an inconsistent state when another thread is adding a

问题 I have a java.util.HashMap object. I guarantee that writing to HashMap is done by single dedicated thread. However, reading from the same HashMap object can be done from more that one thread at the time. Can I run in any troubles with such implementation? 回答1: Yes, you can run into big troubles with such an implementation! Adding a value to the HashMap is not an atomic operation. So if you read the map from another thread you might see an inconsistent state when another thread is adding a

问题 (For the purposes of this post, I will refer to each "sheet" in a google spreadsheet as a tab, I find the naming convention to be confusing when reading) In a Google Sheets add-on, I am attempting to create a setup process that will allow the user to enter the link of a Google Form based on a prompt for that form (the reason I don't just pull all the ID's into the code manually is that the forms themselves being used may change from user to user), and have that form's responses be linked to

问题 In my android application I have configured a periodic syncing using sync adapter, and its working fine except if the android storage space is running out.If i deleted some files and free up space then sync will start to work.Actually I am just syncing data from my device to the remote server,so there is no need for extra space in device while syncing.So why does the android sync adapter demand some space to work.What I noticed is the sync adapter won't work even if there is a 2% free memory

问题 I have read somewhere that every threads have its own copy of shared states, even if I'm using synchronized or locks for modifying the variables, what guarantees that the changed state will be flushed into the main memory rather than in thread's own cache memory. I know volatile guarantees and justifies the above scenario, even I know synchronized justifies too. How does synchronized guarantees that changing the value is happening in the main memory rather than thread cache memory. Ex Thread

问题 to put it simply: is there a way to have multiple sccrollable widgets (say, SingleSchildScrollView ) together in sync? i just want 2 scrollables that can scroll the other as i scroll one. this way i can use Stack to put them on top of each other and the one behind can scroll following the front one. or maybe put them in another set of Column or Row so that they are separate, but still scrolls by just scrolling either one. i tried using controller but it does not seems to be doing what i think

问题 Background: My WCF application has to call a service that does not have any concurrency checking in it. It is a service created by a third party and getting them to add concurrency checking may not be possible. I can ensure that the only way to call the third party service is via my WCF application. So I am considering putting concurrency checking in my code. To do this, I will use an identifier that uniquely describes the data being modified. The idea is that if one call to the service is