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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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  • How can I make this Dictionary TryGetValue code more readable?

    - by mafutrct
    I'd like to test if an id was not yet known or, if it is known, if the associated value has changed. I'm currently using code similar to this, but it is hard to understand for those not familiar with the pattern. Can you think of a way to make it more readable while keeping it short in LOC? string id; string actual; string stored; if (!someDictionary.TryGetValue (id, out stored) || stored != actual) { // id not known yet or associated value changed. }

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  • A faster alternative to Pandas `isin` function

    - by user3576212
    I have a very large data frame df that looks like: ID Value1 Value2 1345 3.2 332 1355 2.2 32 2346 1.0 11 3456 8.9 322 And I have a list that contains a subset of IDs ID_list. I need to have a subset of df for the ID contained in ID_list. Currently, I am using df_sub=df[df.ID.isin(ID_list)] to do it. But it takes a lot time. IDs contained in ID_list doesn't have any pattern, so it's not within certain range. (And I need to apply the same operation to many similar dataframes. I was wondering if there is any faster way to do this. Will it help a lot if make ID as the index? Thanks!

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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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  • 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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  • question of sed replace

    - by chun
    hi i have a config file xml <tflow name="CENTRE" inputDTD="/JOBS/cnav/etc/jobReporting/batch/dtd/dtd-ContactCentre.dtd" inputFile="/JOBS/cnav/etc/jobReporting/import/2010.05.02.CONTACTCENTRE.xml" logPath="/JOBS/cnav/etc/jobReporting/logs/" rejectPath="/JOBS/cnav/etc/jobReporting/rejets/"/> <tflow name="SKILL" inputDTD="/JOBS/cnav/etc/jobReporting/batch/dtd/dtd-Skill.dtd" inputFile="/JOBS/cnav/etc/jobReporting/import/2010.05.02.SKILLS.xml" logPath="/JOBS/cnav/etc/jobReporting/logs/" rejectPath="/JOBS/cnav/etc/jobReporting/rejets/"/> my shell is aim to change, by example '2010.05.02.SKILLS.xml' with 'newdate.SKILLS.xml' currently i think of SED, i wrote: sed 's/(import\/)(\d{4}.\d{2}.\d{2})/$1$newdate/g' myfile.xml it doesn't work,i test the pattern with RegExr(a site) which is fine. is it a problem of synthesis of SED? thanks.

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  • Grep for multiple patterns over multiple files

    - by prelic
    I've been googling around, and I can't find the answer I'm looking for. Say I have a file, text1.txt, in directory mydir whose contents are: one two and another called text2.txt, also in mydir, whose contents are: two three four I'm trying to get a list of files (for a given directory) which contain all (not any) patterns I search for. In the example I provided, I'm looking for output somewhere along the lines of: ./text1.txt or ./text1.txt:one ./text1.txt:two The only things I've been able to find are concerning matching any patterns in a file, or matching multiple patterns in a single file (which I tried extending to a whole directory, but received grep usage errors). Any help is much appreciated. Edit-Things I've tried grep "pattern1" < ./* | grep "pattern2" ./* "ambiguous redirect" grep 'pattern1'|'pattern2' ./* returns files that match either pattern

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  • Buffering db inserts in multithreaded program

    - by Winter
    I have a system which breaks a large taks into small tasks using about 30 threads as a time. As each individual thread finishes it persists its calculated results to the database. What I want to achieve is to have each thread pass its results to a new persisance class that will perform a type of double buffering and data persistance while running in its own thread. For example, after 100 threads have moved their data to the buffer the persistance class then the persistance class swaps the buffers and persists all 100 entries to the database. This would allow utilization of prepared statements and thus cut way down on the I/O between the program and the database. Is there a pattern or good example of this type of multithreading double buffering?

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  • How to search for duplicate values in a huge text file having around Half Million records

    - by Shibu
    I have an input txt file which has data in the form of records (each row is a record and represents more or less like a DB table) and I need to find for duplicate values. For example: Rec1: ACCOUNT_NBR_1*NAME_1*VALUE_1 Rec2: ACCOUNT_NBR_2*NAME_2*VALUE_2 Rec3: ACCOUNT_NBR_1*NAME_3*VALUE_3 In the above set, the Rec1 and Rec2 are considered to be duplicates as the ACCOUNT NUMBERS are same(ACCOUNT_NBR1). Note: The input file shown above is a delimiter type file (the delimiter being *) however the file type can also be a fixed length file where each column starts and ends with a specified positions. I am currently doing this with the following logic: Loop thru each ACCOUNT NUMBER Loop thru each line of the txt file and record and check if this is repeated. If repeated record the same in a hashtable. End End And I am using 'Pattern' & 'BufferedReader' java API's to perform the above task. But since it is taking a long time, I would like to know a better way of handling it. Thanks, Shibu

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  • Haskell quiz: a simple function

    - by levy
    I'm not a Haskell programmer, but I'm curious about the following questions. Informal function specification: Let MapProduct be a function that takes a function called F and multiple lists. It returns a list containing the results of calling F with one argument from each list in each possible combination. Example: Call MapProduct with F being a function that simply returns a list of its arguments, and two lists. One of the lists contains the integers 1 and 2, the other one contains the strings "a" and "b". It should return a list that contains the lists: 1 and "a", 1 and "b", 2 and "a", 2 and "b". Questions: How is MapProduct implemented? What is the function's type? What is F's type? Can one guess what the function does just by looking at its type? Can you handle inhomogeneous lists as input? (e.g. 1 and "a" in one of the input lists) What extra limitation (if any) do you need to introduce to implement MapProduct?

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  • Simplest LINQ in C# troubleshooting.

    - by Jay
    I'm trying to learn a bit of LINQ but I'm having compile issues right off the bat. Is there any specific reason why this won't work? using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace HelloLINQ { class HelloLINQ { public static void Main() { Example1(); } public static void Example1() { var numbers = new int[] { 1, 5, 3, 7, 3, 8, 9, 3, 6, 6, 2 }; var under5 = from n in numbers select n; foreach (var n in under5) { Console.WriteLine(n); } } } } The error is: Could not find an implementation of the query pattern for source type 'int[]'. 'Select' not found. Are you missing a reference to 'System.Core.dll' or a using directive for 'System.Linq'?

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  • Optimizing NSNumber numberWithInt:

    - by Riviera
    I am profiling an iPhone app and I noticed a strange pattern. In a certain block of code that's called quite frequently... [item setQuadrant:[NSNumber numberWithInt:a]]; [item setIndex:[NSNumber numberWithInt:b]]; [item setTimestamp:[NSNumber numberWithInt:c]]; [item setState:[NSNumber numberWithInt:d]]; [item setCompletionPercentage:[NSNumber numberWithInt:e]]; [item setId_:[NSNumber numberWithInt:f]]; ...the first call to [NSNumber numberWithInt:] takes an inordinate amount of time, in the order of 10-15x that of the remaining calls. I've verified that the results are consistent if I shuffle the lines (the first line is always the slow one, by the same ratio). Is there something going on that I'm not aware of? Perhaps this happens because this block is inside a try/catch?

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  • How to get the action from the HttpServlet request to dispatch to multiple pages

    - by JFB
    I am using the Page Controller pattern. How could I use the same controller for two different pages by detecting the request action and then dispatching according to the result? Here is my code: account.jsp <form name="input" action="<%=request.getContextPath() %>/edit" method="get"> <input type="submit" value="Modifier" /> </form> Account Servlet public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("received HTTP GET"); String action = request.getParameter("action"); if (action == null) { // the account page dispatch(request, response, "/account"); } else if (action == "/edit") { // the popup edit page dispatch(request, response, "/edit"); } protected void dispatch(HttpServletRequest request, HttpServletResponse response, String page) throws javax.servlet.ServletException, java.io.IOException { RequestDispatcher dispatcher = getServletContext() .getRequestDispatcher(page); dispatcher.forward(request, response); } }

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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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  • Help with regex pulling XML data from response body in PHP

    - by spdaly
    I am working on a project that pulls data from JMS queue using PHP and Zend Framework. The HTTP client response is below. All I need is the XML string. I came up with /(.*)<\/RequestDetails/gs which tests ok on http://gskinner.com/RegExr/ but the preg_match call is returning an empty matches array. I'm going to continue to hunt around for a pattern, but thought I would post here as well. Thanks to all who read, etc... Steve UPDATE: I can't get the code to paste correctly. Here's a link to a pastbin: http://pastebin.com/rQxzcfSg

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  • RegEx replace query to pick out wiki syntax

    - by Jeremy Thake
    I've got a string of HTML that I need to grab the "[Title|http://www.test.com]" pattern out of e.g. "dafasdfasdf, adfasd. [Test|http://www.test.com/] adf ddasfasdf [SDAF|http://www.madee.com/] assg ad" I need to replace "[Title|http://www.test.com]" this with "Title". What is the best away to approach this? I was getting close with: string test = "dafasdfasdf adfasd [Test|http://www.test.com/] adf ddasfasdf [SDAF|http://www.madee.com/] assg ad "; string p18 = @"(\[.*?|.*?\])"; MatchCollection mc18 = Regex.Matches(test, p18, RegexOptions.Singleline | RegexOptions.IgnoreCase); foreach (Match m in mc18) { string value = m.Groups[1].Value; string fulltag = value.Substring(value.IndexOf("["), value.Length - value.IndexOf("[")); Console.WriteLine("text=" + fulltag); } There must be a cleaner way of getting the two values out e.g. the "Title" bit and the url itself. Any suggestions?

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  • Live asynchronous time feed for websites

    - by Maven
    I want to show up the time over my website based over the location of the user, let’s say if user one browsing the website is from USA than the time should be what is in USA currently and same for China etc. and all. I was wondering if there exists a JavaScript plugin for it but I didn’t find any as dynamic as I want, my requirements include: Something that can be fully stylized according to website theme (no iframes) The pattern I want is to be in (HH:MM:SS) It should be asynchronous like the second [SS] keep ticking and the time keep updating Is this possible, a way around to achieve it?

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  • Dimension Reduction in Categorical Data with missing values

    - by user227290
    I have a regression model in which the dependent variable is continuous but ninety percent of the independent variables are categorical(both ordered and unordered) and around thirty percent of the records have missing values(to make matters worse they are missing randomly without any pattern, that is, more that forty five percent of the data hava at least one missing value). There is no a priori theory to choose the specification of the model so one of the key tasks is dimension reduction before running the regression. While I am aware of several methods for dimension reduction for continuous variables I am not aware of a similar statical literature for categorical data (except, perhaps, as a part of correspondence analysis which is basically a variation of principal component analysis on frequency table). Let me also add that the dataset is of moderate size 500000 observations with 200 variables. I have two questions. Is there a good statistical reference out there for dimension reduction for categorical data along with robust imputation (I think the first issue is imputation and then dimension reduction)? This is linked to implementation of above problem. I have used R extensively earlier and tend to use transcan and impute function heavily for continuous variables and use a variation of tree method to impute categorical values. I have a working knowledge of Python so if something is nice out there for this purpose then I will use it. Any implementation pointers in python or R will be of great help. Thank you.

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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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  • php regex to split invoice line item description

    - by user1053700
    I am attempting to split strings like the following: An item (Item A) which may contain 89798 numbers and letters @ $550.00 4 of Item B @ $420.00 476584 of Item C, with a larger quantity and different currency symbol @ £420.00 into: array( 0 => 1 1 => "some item which may contain 89798 numbers and letters" 2 => $550.00 ); does that make sense? I am looking for a regex pattern which will split the quantity, description, and price (including symbol). the strings will always be: qty x description @ price+symbol so i assume the regex would be something like: `(match a number and only a number) x (get description letters and numbers before the @ symbol) @ (match the currency symbol and price)` How should I approach this?

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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's the right way to handle "One, Both, or None" logic?

    - by Stephen
    I have a logic situation that is best described as two "Teams" trying to win a task. The outcome of this task could be a single winner, a tie (draw), or no winner (stalemate). Currently, I'm using a nested if/else statement like so: // using PHP, but the concept seems language agnostic. if ($team_a->win()) { if ($team_b->win()) { // this is a draw } else { // team_a is the winner } } else { if ($team_b->win()) { // team_b is the winner } else { // This is a stalemate, no winner. } } This seems rather spaghetti-like and repetitive. Is there a more logical, DRY pattern I could use?

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  • Which would be better? Storing/access data in a local text file, or in a database?

    - by TerranRich
    Basically, I'm still working on a puzzle-related website (micro-site really), and I'm making a tool that lets you input a word pattern (e.g. "r??n") and get all the matching words (in this case: rain, rein, ruin, etc.). Should I store the words in local text files (such as words5.txt, which would have a return-delimited list of 5-letter words), or in a database (such as the table Words5, which would again store 5-letter words)? I'm looking at the problem in terms of data retrieval speeds and CPU server load. I could definitely try it both ways and record the times taken for several runs with both methods, but I'd rather hear it from people who might have had experience with this. Which method is generally better overall?

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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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  • Injecting a dependancy into a base class

    - by Jamie Dixon
    Hey everyone, I'm on a roll today with questions. I'm starting out with Dependency Injection and am having some trouble injecting a dependency into a base class. I have a BaseController controller which my other controllers inherit from. Inside of this base controller I do a number of checks such as determining if the user has the right privileges to view the current page, checking for the existence of some session variables etc. I have a dependency inside of this base controller that I'd like to inject using Ninject however when I set this up as I would for my other dependencies I'm told by the compiler that: Error 1 'MyProject.Controllers.BaseController' does not contain a constructor that takes 0 argument This makes sense but I'm just not sure how to inject this dependency. Should I be using this pattern of using a base controller at all or should I be doing this in a more efficient/correct way?

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