concurrency

问题 The javadoc for SimpleDateFormat states that SimpleDateFormat is not synchronized. "Date formats are not synchronized. It is recommended to create separate format instances for each thread. If multiple threads access a format concurrently, it must be synchronized externally." But what is the best approach to using an instance of SimpleDateFormat in a multi threaded environment. Here are a few options I have thought of, I have used options 1 and 2 in the past but I am curious to know if there

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Multiple (asynchronous) connections with urllib2 or other http library? I am working on a Linux web server that runs Python code to grab realtime data over HTTP from a 3rd party API. The data is put into a MySQL database. I need to make a lot of queries to a lot of URL's, and I need to do it fast (faster = better). Currently I'm using urllib3 as my HTTP library. What is the best way to go about this? Should I

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Multiple (asynchronous) connections with urllib2 or other http library? I am working on a Linux web server that runs Python code to grab realtime data over HTTP from a 3rd party API. The data is put into a MySQL database. I need to make a lot of queries to a lot of URL's, and I need to do it fast (faster = better). Currently I'm using urllib3 as my HTTP library. What is the best way to go about this? Should I

问题 The documentation for asyncio gives two examples for how to print "Hello World" every two seconds: https://docs.python.org/3/library/asyncio-eventloop.html#asyncio-hello-world-callback https://docs.python.org/3/library/asyncio-task.html#asyncio-hello-world-coroutine I can run those from the interpreter, but if I do I lose access to the interpreter. Can an asyncio event loop be run in the background, so that I can keep typing commands at the interpreter? 回答1: Edit: If using Python 3.8 or above

问题 Are some implementations better than others for specific applications? Is there anything to earn by rolling out your own? 回答1: Check out the description of the Test-and-set machine instruction on Wikipedia, which alludes to how atomic operations are achieved at the machine level. I can imagine most language-level mutex implementations rely on machine-level support such as Test-and-set. 回答2: Building on Adamski's test-and-set suggestion, you should also look at the concept of "fast user-space

问题 I'm new to threads. How can I get t.join to work, whereby the thread calling it waits until t is done executing? This code would just freeze the program, because the thread is waiting for itself to die, right? public static void main(String[] args) throws InterruptedException { Thread t0 = new Thready(); t0.start(); } @Override public void run() { for (String s : info) { try { join(); Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.printf("%s %s%n",

问题 I have been playing with my own version of this, using 'if', and all seems to be working fine. Of course this will break down horribly if signalAll() is used instead of signal(), but if only one thread at a time is notified, how can this go wrong? Their code here - check out the put() and take() methods; a simpler and more-to-the-point implementation can be seen at the top of the JavaDoc for Condition. Relevant portion of my implementation below. public Object get() { lock.lock(); try { if(

问题 I'm new to threads. How can I get t.join to work, whereby the thread calling it waits until t is done executing? This code would just freeze the program, because the thread is waiting for itself to die, right? public static void main(String[] args) throws InterruptedException { Thread t0 = new Thready(); t0.start(); } @Override public void run() { for (String s : info) { try { join(); Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.printf("%s %s%n",

问题 I'm new to threads. How can I get t.join to work, whereby the thread calling it waits until t is done executing? This code would just freeze the program, because the thread is waiting for itself to die, right? public static void main(String[] args) throws InterruptedException { Thread t0 = new Thready(); t0.start(); } @Override public void run() { for (String s : info) { try { join(); Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.printf("%s %s%n",

问题 This was asked slightly differently earlier but asking for a yes/no answer but I'm looking for the explanation that's missing from the book (Java Concurrency in Practice), of how this apparent big mistake would be exploited maliciously or accidentally. A final mechanism by which an object or its internal state can be published is to publish an inner class instance, as shown in ThisEscape in Listing 3.7. When ThisEscape publishes the EventListener, it implicitly publishes the enclosing