synchronization

问题 I want to develop application same as UBER in which I need to show available taxis in the selected region and update as the taxis are hired, available, unavailable. Kind of auto refresh. Calling the web service in the background after regular time interval is not a good option. Can any one suggest me better and fast way to achieve this. Thanks 回答1: Push Use sockets when the app is running. This will give you immediate updates. Use Push notifications when the app is not running (use

问题 I have been reading a lot about synchronization in Java and all the problems that can occur. However, what I'm still slightly confused about is how the JIT can reorder a write. For instance, a simple double check lock makes sense to me: class Foo { private volatile Helper helper = null; // 1 public Helper getHelper() { // 2 if (helper == null) { // 3 synchronized(this) { // 4 if (helper == null) // 5 helper = new Helper(); // 6 } } return helper; } } We use volatile on line 1 to enforce a

问题 After change customer details from magento 1.9 changes not reflect on OroCRM almost 2 days over still not changes not reflect on OroCRM. How to do auto sync in every changes at the same time. 来源： https://stackoverflow.com/questions/60296980/magento-1-9-orocrm-update-sync-not-working-properly

问题 When I sync my project in build.gradle(Project: Allo) I see this error Failed to find target with hash string 'android-28'in: C:\Users\hacker\AppData\Local\Android\Sdk Config: apply plugin: 'com.google.gms.google-services' android { compileSdkVersion 28 defaultConfig { applicationId "com.example.android.allo" minSdkVersion 19 targetSdkVersion 28 versionCode 1 versionName "1.0" testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner" } buildTypes { release { minifyEnabled

问题 As we know, ReentrantLock has a max reentrant limit: Integer.MAX_VALUE ; Does synchronized block have reentrant limit too? Update : I found it is hard to write test code for synchronized reentrant: public class SyncReentry { public static void main(String[] args) { synchronized (SyncReentry.class) { synchronized (SyncReentry.class) { // ...write synchronized block for ever } } } } Can anyone help write some code for synchronized reentrant limit test? 回答1: Since the specification does not

问题 I have a cron task that runs periodically. This task depends on a condition to be valid in order to complete its processing. In case it matters this condition is just a SELECT for specific records in the database. If the condition is not satisfied (i.e the SELECT does not return the result set expected) then the script exits immediately. This is bad as the condition would be valid soon enough (don't know how soon but it will be valid due to the run of another script). So I would like somehow

问题 I am rather inexperienced with Java and multi-threading so maybe you guys can help. I am having trouble printing out a series of numbers and letters in a TextArea box when I multi-thread. This is my code: public class MultiThread extends Application { static TextArea outputArea = new TextArea(); @Override public void start(Stage primaryStage) throws Exception { outputArea.setWrapText(true); Runnable printA = new PrintChar('a', 100); Runnable printB = new PrintChar('b', 100); Runnable print100

问题 I didn't get clearly how coherent qualifier and atomic operations work together. I perform some accumulating operation on the same SSBO location with this code: uint prevValue, newValue; uint readValue = ssbo[index]; do { prevValue = readValue; newValue = F(readValue); } while((readValue = atomicCompSwap(ssbo[index], prevValue, newValue)) != prevValue); This code works fine for me, but still, do I need to declare the SSBO (or Image) with coherent qualifier in this case? And do I need to use

问题 I'm looking for a solution that allows a browser's localStorage to be less local, so that people can access their data on multiple devices. The traditional way is to run a database on a server and have people log in; but I'm trying to avoid doing that. I'd like the server side to be lightweight - perhaps even completely static if possible - and to not have the job of safely storing passwords, worrying about data protection etc. Many browsers have a login of some sort -- Google Account,

问题 I'm looking for a solution that allows a browser's localStorage to be less local, so that people can access their data on multiple devices. The traditional way is to run a database on a server and have people log in; but I'm trying to avoid doing that. I'd like the server side to be lightweight - perhaps even completely static if possible - and to not have the job of safely storing passwords, worrying about data protection etc. Many browsers have a login of some sort -- Google Account,