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  • How to synchronize static method in java.

    - by Summer_More_More_Tea
    Hi there: I come up with this question when implementing singleton pattern in Java. Even though the example listed blow is not my real code, yet very similar to the original one. public class ConnectionFactory{ private static ConnectionFactory instance; public static synchronized ConnectionFactory getInstance(){ if( instance == null ){ instance = new ConnectionFactory(); } return instance; } private ConnectionFactory(){ // private constructor implementation } } Because I'm not quite sure about the behavior of a static synchronized method, I get some suggestion from google -- do not have (or as less as possible) multiple static synchronized methods in the same class. I guess when implementing static synchronized method, a lock belongs to Class object is used so that multiple static synchronized methods may degrade performance of the system. Am I right? or JVM use other mechanism to implement static synchronized method? What's the best practice if I have to implement multiple static synchronized methods in a class? Thank you all! Kind regards!

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  • Stuck with the math in a Flash project, would parsing engine help?

    - by VideoDnd
    I've been stuck with the math in a Flash project? It's a loose design pattern my director formulated. My goal is to keep the project object oriented, and get 'non Flash obstacles' off my plate. Do you recommend using parsing engines for processing math? XML values going to AS3, updating a changing acceleration formula. I don't hate math, but it just doesn't seem OOP or good project planning to have the math stuck in Flash. Your comments are welcome.

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  • How can I make CAPTCHA work across multiple pages?

    - by jm04469
    Ever visit a website such as myspace where they leverage CAPTCHA to prevent spam? The typical pattern is to present a challenge to each URL that is opened, yet the challenge doesn't actually belong to the page itself which causes additional bandwidth usage. So, if I open up six pages at the same time and want to present a challenge on each page. I want the challenge to be tied to the page and not to the session. How can I make this work with Spring and/or Struts.

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  • Regular expression: who's greedier?

    - by polygenelubricants
    My primary concern is with the Java flavor, but I'd also appreciate information regarding others. Let's say you have a subpattern like this: (.*)(.*) Not very useful as is, but let's say these two capture groups (say, \1 and \2) are part of a bigger pattern that matches with backreferences to these groups, etc. So both are greedy, in that they try to capture as much as possible, only taking less when they have to. My question is: who's greedier? Does \1 get first priority, giving \2 its share only if it has to? What about: (.*)(.*)(.*) Let's assume that \1 does get first priority. Let's say it got too greedy, and then spit out a character. Who gets it first? Is it always \2 or can it be \3? Let's assume it's \2 that gets \1's rejection. If this still doesn't work, who spits out now? Does \2 spit to \3, or does \1 spit out another to \2 first?

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  • Should I dive into ASP.NET MVC or start with ASP.NET Webforms?

    - by Sahat
    I plan to pick up Silverlight in the future. Possibility of going into Microsoft WPF. Currently learning Objective-C 2.0 w/ Cocoa. I already know Pros and Cons of ASP.NET MVC vs ASP.NET Webforms. What I want to know is what would be more "efficient" for me to learn given the circumstances above? By efficient I mean learning one design pattern once and then re-using it. Objective-C I believe uses MVC approach? What about Silverlight? WPF? So what do you think? Also as a side question is it true that ASP.NET Webforms is often used by freelancers/small companies and ASP.NET MVC in large enterprises?

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  • Is there a performance gain from defining routes in app.yaml versus one large mapping in a WSGIAppli

    - by jgeewax
    Scenario 1 This involves using one "gateway" route in app.yaml and then choosing the RequestHandler in the WSGIApplication. app.yaml - url: /.* script: main.py main.py from google.appengine.ext import webapp class Page1(webapp.RequestHandler): def get(self): self.response.out.write("Page 1") class Page2(webapp.RequestHandler): def get(self): self.response.out.write("Page 2") application = webapp.WSGIApplication([ ('/page1/', Page1), ('/page2/', Page2), ], debug=True) def main(): wsgiref.handlers.CGIHandler().run(application) if __name__ == '__main__': main() Scenario 2: This involves defining two routes in app.yaml and then two separate scripts for each (page1.py and page2.py). app.yaml - url: /page1/ script: page1.py - url: /page2/ script: page2.py page1.py from google.appengine.ext import webapp class Page1(webapp.RequestHandler): def get(self): self.response.out.write("Page 1") application = webapp.WSGIApplication([ ('/page1/', Page1), ], debug=True) def main(): wsgiref.handlers.CGIHandler().run(application) if __name__ == '__main__': main() page2.py from google.appengine.ext import webapp class Page2(webapp.RequestHandler): def get(self): self.response.out.write("Page 2") application = webapp.WSGIApplication([ ('/page2/', Page2), ], debug=True) def main(): wsgiref.handlers.CGIHandler().run(application) if __name__ == '__main__': main() Question What are the benefits and drawbacks of each pattern? Is one much faster than the other?

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  • Strategy for desugaring Haskell

    - by luqui
    I'm developing a virtual machine for purely functional programs, and I would like to be able to test and use the the wide variety of Haskell modules already available. The VM takes as input essentially terms in the untyped lambda calculus. I'm wondering what would be a good way to extract such a representation from modern Haskell modules (eg. with MPTC's, pattern guards, etc.). I did a little research and there doesn't seem to be a tool that does this already (I would be delighted to be mistaken), and that's okay. I'm looking for an approach. GHC Core seems too operationally focused, especially since one of the things the VM does is to change the evaluation order significantly. Are there any accessible intermediate representations that correspond more closely to the lambda calculus?

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  • What are some of the useful concepts to know about when building Silverlight apps?

    - by cody
    The Silverlight(& WPF) space seems to have a whole new nomenclature around it so at times I'm having a hard time figuring our what is important and useful to research a bit more. For example I 'know' about the MVVM pattern but I'm looking for things that are a bit smaller in scope, that is topics, ideas, programming constructs that might be used in implementing MVVM and would need to know before hand. So basically I'm looking for some of the key topics and concepts that people have found useful or are important when creating a Silverlight apps. And maybe why it is useful or important and when\where it might be applied or used. Thanks.

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  • python processs complete list files matched

    - by thomytheyon
    Hi All, I'm trying to get a simple code working, unfortunatly im a python beginner. My script should return a list of files that doesn't match a pattern, more information here : http://stackoverflow.com/questions/2910106/python-grep-reverse-matching/2910288#2910288 My code is running but doesn't process the complete list of files found as it should : import sys,os filefilter = ['.xml','java','.jsp','lass'] path= "/home/patate/code/project" s = "helloworld" for path, subdirs, files in os.walk(path): for name in files: if name[-4:] in filefilter : f = str(os.path.join(path, name)) with open(f) as fp: if s in fp.read(): print "%s has the string" % f else: print "%s doesn't have the string" % f This code return : /home/patate/code/project/blabla/blabla/build.xml doesn't have the string None If i change f = str(os.path.join(path, name)) for print str(os.path.join(path, name)) I can see the whole list being printed. How can i process the whole list as i which to ? :( Thanks again.

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  • Is there a definitive list of uri patterns for use in android apps made by google?

    - by The Trav
    Apart from http://developer.android.com/guide/appendix/g-app-intents.html (which is quite good but fairly limited in the number of apps/uri's it covers) I've been unable to find a decent reference source for looking up URI's to use when integrating with google apps. I'm currently working on triggering the "add new contact" UI, and have found that the tel: uri pattern seems to work, but what if I only have a name and an email? I wouldn't have expected I'd need to rely on sample code / trial and error, but I really can't see anywhere where the intent/URI interface is supposed to be documented in android apps. Does such a standard exist? Is there some quasi standard / user database that I can consult? On a platform with such a good inter-interoperability architecture it just seems like something so useful I can't believe it's not there

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  • How to imitate the workflow view of Automator?

    - by andyfeind
    I’m starting to develop my first full-blown Cocoa application containing a view which I would like to behave (and look) similar to Automator’s AMWorkflowView. The basic features I’d like to achieve: Positioning of subviews Display of subviews in expanded / collapsed states Multiple selection Drag and drop In order to get accustomed to Cocoa, I started with a custom NSView which mainly served as a container for the custom subviews and handled their positioning and multiple selection. The subviews are also subclasses of NSView, and contain a variable amount of views themselves, like buttons, labels and popup menus, and therefore can have different heights. This worked quite well, but before going on, I want to make sure to have everything neat and tidy according to the MVC pattern. I suspect that there already is a class in Cocoa that facilitates the implementation of a view container, like maybe NSCollectionView. It seems that there is no (easy) way to display differently sized views in an NSCollectionView, though. Should I continue implementing my custom NSView (probably using an NSArrayController for selection and sorting support), or are there better ways to go? Any help is much appreciated

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  • How do I simplify these NUNit tests?

    - by Lucas Meijer
    These three tests are identical, except that they use a different static function to create a StartInfo instance. I have this pattern coming up all trough my testcode, and would love to be be able to simplify this using [TestCase], or any other way that reduces boilerplate code. To the best of my knowledge I'm not allowed to use a delegate as a [TestCase] argument, and I'm hoping people here have creative ideas on how to make the code below more terse. [Test] public void ResponseHeadersWorkinPlatform1() { DoResponseHeadersWorkTest(Platform1StartInfo.CreateOneRunning); } [Test] public void ResponseHeadersWorkinPlatform2() { DoResponseHeadersWorkTest(Platform2StartInfo.CreateOneRunning); } [Test] public void ResponseHeadersWorkinPlatform3() { DoResponseHeadersWorkTest(Platform3StartInfo.CreateOneRunning); } void DoResponseHeadersWorkTest(Func<ScriptResource,StartInfo> startInfoCreator) { ScriptResource sr = ScriptResource.Default; var process = startInfoCreator(sr).Start(); //assert some things here }

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  • Cakephp: Designpattern for creation of models in hasMany relationship

    - by Chris
    I have two Models: Car and Passenger. Car hasMany Passenger Passenger belongsTo Car I managed to create add functionailty for each model and managed to resolve the hasMany relationship between them. Now I'm trying to create a addCar function and view that allows the user to create a new car and automatically generate Passengers. I thought of something like this The view asks the user enter the car information The view has some field that allows to temporarly add new passengers and remove remove them When the user saves the new car, the entities for the passengers are created, the entity for the car is created and the passengers are linked to the car. If the user decides to cacnel everything, the DB remains unchanged. Now my question is: What is the best way to do this? Is there a pattern / tutorial to follow for such a entity and associated subentity creation? To clarify: The passengers associated with each car do not exist prior to the existence of the car.

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  • Text replace with regex in SQL Server

    - by Thiyaneshwaran S
    Currently I have a SQL server column of type nvarchar(max) which has text that starts with <span class="escape_<<digits>>"></span> The only thing that varies in the pattern is the <<digits>> in the class name. The common part is <span class="myclass_ and the closing </span> Some sample values are <span class="myclass_12"></span> <span class="myclass_234"></span> <span class="myclass_4546"></span> These span text are present only at the beginning of the column. Any such matching span in the middle should not be removed or matched. Whats the SQL Server query with regex to remove all these occurances of span?

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  • How can an Android Service know that its not bound to any Activities

    - by tunneling
    I have an Android Service that I would like to keep running even after the last Activity has been popped off the stack, or the User has chosen to do something else. Essentially the Service is listening for changes on a remote server, and I would like to generate a Notification if and only if an Activity from the app isn't running(or visible). In other words, I don't want the Notifications to occur while the User is directly interacting with the app. In the case where the User is directly interacting with the app, the Service will notify the Activity and update appropriate UI elements based on the changes. I plan to implement this through the Observer pattern. How can the Service know if none of apps Activities are bound to it? Thanks, J

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  • filter log file by defining regexes

    - by fmpdmb
    I have some HUGE log files (50Mb; ~500K lines) I need to start filtering some of the crap out of. The log files are being produced using log4j and have the basic pattern of: [log-level] date-time class etc, etc log-message I'm looking for a way that I can identify a regex start and regex end (or something similar) that will filter out the matching entries from the file so I can more easily wade through these massive files. I'm sure I could write a java program to accomplish this task, but I thought I'd ask the community before going down that path. Thanks in advance.

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  • Force an object to be allocated on the heap

    - by Warren Seine
    A C++ class I'm writing uses shared_from_this() to return a valid boost::shared_ptr<>. Besides, I don't want to manage memory for this kind of object. At the moment, I'm not restricting the way the user allocates the object, which causes an error if shared_from_this() is called on a stack-allocated object. I'd like to force the object to be allocated with new and managed by a smart pointer, no matter how the user declares it. I thought it could be done through a proxy or an overloaded new operator, but I can't find a proper way of doing that. Is there a common design pattern for such usage? If it's not possible, how can I test it at compile time?

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  • bulk update/delete entities of different kind in db.run_in_transaction

    - by Ray Yun
    Here goes pseudo code of bulk update/delete entities of different kind in single transaction. Note that Album and Song entities have AlbumGroup as root entity. class AlbumGroup: pass class Album: group = db.ReferenceProperty(reference_class=AlbumGroup,collection_name="albums") class Song: album = db.ReferenceProperty(reference_class=Album,collection_name="songs") def bulk_update_album_group(album_group): updated = [album_group] deleted = [] for album in album_group.albums: updated.append(album) for song in album.songs: if song.is_updated: updated.append(song) if song.is_deleted: deleted.append(song) db.put(updated) db.delete(deleted) a = AlbumGroup.all().filter("...").get() # bulk update/delete album group. for simplicity, album cannot be deleted. db.run_in_transaction(bulk_update_album_group,a) But I met a famous "Only Ancestor Queries in Transactions" error at the iterating reference properties like album.songs or album_group.albums. I guess ancestor() filter does not help because those entities are modified in memory. Should I not to iterate reference property in transaction function and always provide them as function parameters like def bulk_update_album_group(updated,deleted): ??? Is there any good coding pattern for this situation?

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  • Caching result of SELECT statement for reuse in multiple queries

    - by Andrew
    I have a reasonably complex query to extract the Id field of the results I am interested in based on parameters entered by the user. After extracting the relevant Ids I am using the resulting set of Ids several times, in separate queries, to extract the actual output record sets I want (by joining to other tables, using aggregate functions, etc). I would like to avoid running the initial query separately for every set of results I want to return. I imagine my situation is a common pattern so I am interested in what the best approach is. The database is in MS SQL Server and I am using .NET 3.5.

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  • What is a good architecture for a Lift-JPA application?

    - by egervari
    I was wondering what is the best practice for a JPA model in Lift? I noticed that in the jpa demo application, there is just a Model object that is like a super object that does everything. I don't think this can be the most scalable approach, no? Is it is wise to still do the DAO pattern in Lift? For example, there's some code that looks a tad bloated and could be simplified across all model objects: Model.remove(Model.getReference(classOf[Author], someId)) Could be: AuthorDao.remove(someId) I'd appreciate any tips for setting up something that will work with the way Lift wants to work and is also easy to organize and maintain. Preferably from someone who has actually used JPA on a medium to large Lift site rather than just postulating what Spring does (we know how to do that) ;) The first phase of development will be around 30-40 tables, and will eventually get to over 100... we need a scalable, neat approach.

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  • String Functions in IIS Url Rewrite Module

    - by Nariman
    The IIS URL Rewrite Module ships with 3 built-in functions: * ToLower - returns the input string converted to lower case. * UrlEncode - returns the input string converted to URL-encoded format. This function can be used if the substitution URL in rewrite rule contains special characters (for example non-ASCII or URI-unsafe characters). * UrlDecode - decodes the URL-encoded input string. This function can be used to decode a condition input before matching it against a pattern. The functions can be invoked by using the following syntax: {function_name:any_string} The question is: can this list be extended by introducing a Replace function that's available for changing values within a rewrite rule action or condition? Another way to frame the question: is there any way to do a global replace on a URL coming in using this module? It seems that you're limited to using regular expressions and back-references to construct strings, without a search/replace functionality to replace every X with Y in {REQUEST_URI} before issuing a redirect.

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  • Teacher confused about MVC?

    - by Gideon
    I have an assignment to create a game in java using MVC as a pattern. The thing is that stuff I read about MVC aren't really what the teacher is telling me. What I read is that the Model are the information objects, they are manipulated by the controllers. So in a game the controller mutates the placement of the objects and check if there is any collision etc. What my teacher told me is that I should put everything that is universal to the platform in the models and the controllers should only tell the model which input is given. That means the game loop will be in a model class, but also collision checks etc. So what I get from his story is that the View is the screen, the Controller is the unput handeler, and the Model is the rest. Can someone point me in the right direction?

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  • Joomla forwarding code to the View...is this the correct way to do it?

    - by jax
    Here are some sample methods from my Controller class. Now when the user clicks the New button $task=add is sent to the Controller and the add() method is called. As you can see it does not really do anything, it just creates a url and forwards it off to the correct view. Is this the correct way of doing things in the MVC pattern? /** * New button was pressed */ function add() { $link = JRoute::_('index.php?option=com_myapp&c=apps&view=editapp&cid[]=', false); $this->setRedirect($link); } /** * Edit button was pressed - just use the first selection for editing */ function edit() { $cid = JRequest::getVar( 'cid', array(0), '', 'array' ); $id = $cid[0]; $link = JRoute::_("index.php?option=com_myapp&c=apps&view=editapp&cid[]=$id", false); $this->setRedirect($link); }

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  • Interface with inner implementation - good or bad

    - by dermoritz
    I am working on a project with many someInterface - someInterfaceImpl-pairs. Some days ago I got the idea (probably inspired by reading some objective c code) to include the default implementations as an inner class. Now some colleagues (all with much more java experience than me) saw this idea - feedback was between shocked and surprised ("this is working?"). I googled around a bit but didn't find much evidence of usefulness of this "pattern" (personal i like it): pdf-paper and a faq about code style What do you think - especially in those cases where an "default" implementation is tightly coupled to an interface. Update i just found this: Java Interface-Implementation Pair (see accepted answer)

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  • How often do you implement the big three?

    - by Neil Butterworth
    I was just musing about the number of questions here that either are about the "big three" (copy constructor, assignment operator and destructor) or about problems caused by them not being implemented correctly, when it occurred to me that I could not remember the last time I had implemented them myself. A swift grep on my two most active projects indicate that I implement all three in only one class out of about 150. That's not to say I don't implement/declare one or more of them - obviously base classes need a virtual destructor, and a large number of my classes forbid copying using the private copy ctor & assignment op idiom. But fully implemented, there is this single lonely class, which does some reference counting. So I was wondering am I unusual in this? How often do you implement all three of these functions? Is there any pattern to the classes where you do implement them?

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