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  • Compare Long values Struts2

    - by Marquinio
    Hi everyone I'm trying to compare two values using struts2 s:if tag but its not working. If I hardcode the values it works but I want it to be dynamic. The variable stringValue is of type String. The variable currentLongValue is of type Long. <s:set var="stringValue" value="order"/> <s:iterator value="listTest"> <s:set var="currentLongValue" value="value"/> <s:if test="#currentLongValue.toString() == #stringValue" > //Do something </s:if> <s:else> //Do something else </s:else> </s:iterator> For the s:if I have tried toString and also the equals(). It only works if I hardcode the values. Example: <s:if test="#currentLongValue == 1234"> Any clues? Thank you.

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  • Generic <T> how cast ?

    - by Kris-I
    Hi, I have a "Product" base class, some other classes "ProductBookDetail","ProductDVDDetail" inherit from this class. I use a ProductService class to make operation on these classes. But, I have to do some check depending of the type (ISBN for Book, languages for DVD). I'd like to know the best way to cast "productDetail" value, I receive in SaveOrupdate. I tried GetType() and cast with (ProductBookDetail)productDetail but that's not work. Thanks, var productDetail = new ProductDetailBook() { .... }; var service = IoC.Resolve<IProductServiceGeneric<ProductDetailBook>>(); service.SaveOrUpdate(productDetail); var productDetail = new ProductDetailDVD() { .... }; var service = IoC.Resolve<IProductServiceGeneric<ProductDetailDVD>>(); service.SaveOrUpdate(productDetail); public class ProductServiceGeneric<T> : IProductServiceGeneric<T> { private readonly ISession _session; private readonly IProductRepoGeneric<T> _repo; public ProductServiceGeneric() { _session = UnitOfWork.CurrentSession; _repo = IoC.Resolve<IProductRepoGeneric<T>>(); } public void SaveOrUpdate(T productDetail) { using (ITransaction tx = _session.BeginTransaction()) { //here i'd like ot know the type and access properties depending of the class _repo.SaveOrUpdate(productDetail); tx.Commit(); } } }

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  • Total Average Week using a Parameter

    - by Jose
    I have a crystal report that shows sales volumes called week to date volume. It shows current week, previous week, and average week. The report prompts for a date parameter and I extract the week number to get current week and previous week volumes. Did it this way because Mngmt wants to be able to run report whenever. My problem is for Average Week I cant figure out how to get the number of weeks to divide by for my average. Report originates from June 1st, 2010. Right now I have: DATEPART("ww", {?date}) - DATEPART("ww", DATE(2010, 6, 1)) This returns 2 right now which is perfect, so i divide my total by 2. This code will work until the end of the year then I'm hooped. Any idea how I can make this a little more dynamic. I was thinking a counter somehow, just can't get the logic down because the date parameter will keep changing, meaning I cant increase my counter by 1 after each week??? Cheers.

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  • Create Session Variable from different datasources?

    - by Szafranamn
    Currently I am developing a dynamic website using Dreamweaver cs5 with ColdFusion 9 and using Access to create my databases along with QuickBooks and QODBC to create database. I have established a login session variable stemming from the login page. This session variable is being drawn from one Datasource "Access" Table "Logininfo" Field "FullName" but I wanted to create another session variable either at this point or further into the member's page to use in a query sequence. This session variable would stem from another Datasoucre "QBs" Table "Invoice" Field "CustomerRefFullName" which is generated through Quickbooks and QODBC. I am not sure if this is possible but if it is how do I do it. I want to do this so I can query the Invoice database to upload the customer's Invoices unique to them onto their page. So it would have to be related to their login credentials. If there is another better route to take I would greatly appreciate the advice. Below is the login code if there is additional information needed let me know. This is my current thinking/plan to do what I wish to intend hence the need to create the session variable: I have another Datasource "QBs" with a Table "Invoice" when I create another webpage for the customer to see their invoice I need to create a recordset that accesses that Table. In order to do so I think the best way would some home convert the session.FullName (which came from Access Datasource, Logininfor Table) into a session.CustomerRefFullName (which would have to come from (Datasource: QBs Table: Invoice Field: CustomerRefFullName) that way I could set the query WHERE CustomerRefFullName and have each logged in user see their specific Invoices. So is there a way to turn the session variable off one datasource/table into a different sessionvariable off a new datasource/table even if it is unique just to that page??? <cfif IsDefined("FORM.username")> SELECT FullName, Username,Password,AccessLevels FROM Logininfo WHERE Username= AND Password=

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  • JQuery: how to store records id for data from ajax query in dynamicly created html elements

    - by grapkulec
    Probably question title is rather cryptic but I will try to explain myself here so please bare with me :) Let's assume this configuration: server-side is PHP application responding for requests with data (list of items, single item details, etc.) in json format client-side is JQuery application sending ajax request to that PHP app and creating html content corresponding with received data So, for example: client requests "list of all animals with names staring with 'A'", gets the json response from server, and for every "animal" creates some html gizmo like div with animal description or something like that. It doesn't really matter what html element it will be but it has to point exactly to specific record by "containing" id of that record. And here is my dilemma: is it good solution to use "id" property for that? So it would be like: <div id="10" class="animal"> <p> This is animal of very mysterious kind... </p> </div> <div id="11" class="animal"> <p> And this one is very common to our country... </p> </div> where id="10" is of course indication that this is representation of record with id = 10. Or maybe I should store this record id in some custom made tag like <record_id>10</record_id> and leave an "id" strictly for what it was meant to be (css selector)? I need that record id for further stuff like updating database with some user input or deleting some of "animals" or creating new ones or anything that will be needed. All manipulations will be done with JQuery and ajax requests and responses will be visualized also with dynamic creation of html interface. I'm sure that somebody had to deal with that kind of stuff before so I would be grateful for some tips on that topic.

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  • Java ArrayList remove dupes without sets

    - by Kieran
    I'm having problems removing duplicates from an ArrayList. It's for an assignment for college. Here's the code I have already: public int numberOfDiffWords() { ArrayList<String> list = new ArrayList<>(); for(int i=0; i<words.size()-1; i++) { for(int j=i+1; j<words.size(); j++) { if(words.get(i).equals(words.get(j))) { // do nothing } else { list.add(words.get(i)); } } } return list.size(); } The problem is in the numberOfDiffWords() method. The populate list method is working correctly, as my instructor has given me a sample string (containing 4465 words) to analyse - printing words.size() gives the correct result. I want to return the size of the new ArrayList with all duplicates removed. words is an ArrayList class attribute. UPDATE: I should have mentioned I'm only allowed to use dynamic indexed-based storage for this part of the assignment, which means no hash-based storage.

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  • Autocommands for Matlab in vim?

    - by Benjamin Oakes
    I use several different programming languages every day, and I'd like to have different tab widths (in spaces) for each. For example: I use the "standard" 2 spaces for Ruby, but all our existing Matlab code uses 4 spaces. I have this from my personal ~/.vimrc: augroup lang_perl au! set tabstop=4 " tabstop length N in spaces set shiftwidth=4 " make >> and friends (<<, ^T, ^D) shift N, not the default 8 set expandtab " Use spaces instead of tabs augroup END augroup lang_ruby au! set tabstop=2 " tabstop length N in spaces set shiftwidth=2 " make >> and friends (<<, ^T, ^D) shift N, not the default 8 set expandtab " Use spaces instead of tabs augroup END Those work, but the following doesn't: augroup lang_matlab au! set tabstop=4 " tabstop length N in spaces set shiftwidth=4 " make >> and friends (<<, ^T, ^D) shift N, not the default 8 set expandtab " Use spaces instead of tabs augroup END I really don't understand how augroup lang_ruby figures out that I'm editing a Ruby file. (My searches brought up ftdetect, but the solution wasn't obvious.) It doesn't seem like vim knows that I'm editing Matlab using augroup lang_matlab. What do I change to make this work?

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  • Best way to create a SPARQL endpoint for a RDBMS (MySQL database)

    - by Ankur
    I am doing (want to do) some experiments with Linked Open Datasets particularly those put out by governments. I have a RDBMS (more specifically MySQL). I designed it with semantic web ideas in mind i.e. I have a information stored as objects, predicates and classes which define objects. In turn all objects are related to each other though statements of the form subject -- predicate -- object (where the subjects are from the objects table). I want to be able to query other RDF triple stores from my application and let other triple stores query my data. Is it possible to "set something up" so that this is possible? I have looked at Jena. Using Jena seems to mean I have to it as a storage application rather than MySQL - the only problem with this is that I include a new concept called a category (which I don't think is part of the semantic web languages). I will use categories to help with displaying information (they don't have any other meaning) but using Jena seems to mean that I can't organise predicates under categories for more convenient viewing. I am using Java so a JAVA API is preferred. It's also possible I misunderstood the purpose of Jena, and maybe that can be of use, but I am not sure how. I am sure four days from now this question will seem rather silly, but at the moment I am somewhat confused about how to proceed.

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  • Is it "right" to translate error messages?

    - by Iraklis
    This is somehow subjective depending on the target translation language, but bear with me for a sec. I have recently been involved in a translation project. The goal was to translate the strings of an MVC framework to the Greek language. 70% of the language strings of the framework where translated, however 30% where intentionally left out. The decision was that we will not translate error messages aimed towards the developer of the application. The reasoning behind this (in short) was: are aimed towards designers/programmers. Programmers ( and even designers :) ) should have a basic understanding of English, at least enough so they can search on it on Google if they do not know what it means. (racist?) are aimed towards the developer and in a perfect world should not be displayed to the end user of the application as they concern the inner workings of the web application itself. i.e "You must set the database name in your database config file." and perhaps most importantly, they make the life of the developer harder when he tries to get more information/help regarding the error. For example the above error yields 8 results in Google (in quotes), whereas its Greek translation yields exactly 0. I know that this depends on the popularity of the target translation language and the application itself. For example I'm guessing that there are is vast amount of documentation regarding German SAP error messages (i know, i know, SAP IS German, but you get the point), as opposed to Greek Error Messages documentation regarding random application X which has about 500 installations worldwide. So to summarize: When you develop language translation packs for your applications do you translate error messages? Do you only do for predominant languages like English/Spanish/German/French? Or do you live them intact? I'm not looking for the "right" or "correct" answer, I'm looking for a "best-practices" answer, or if this problem is defined in any "official" standard/policy that you have had experience with.

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  • How to use the FindControl function to find a dynamically generated control?

    - by Abe Miessler
    I have a PlaceHolder control inside of a ListView that I am using to render controls from my code behind. The code below adds the controls: TextBox tb = new TextBox(); tb.Text = quest.Value; tb.ID = quest.ShortName.Replace(" ", ""); ((PlaceHolder)e.Item.FindControl("ph_QuestionInput")).Controls.Add(tb); I am using the following code to retrieve the values that have been entered into the TextBox: foreach (ListViewDataItem di in lv_Questions.Items) { int QuestionId = Convert.ToInt32(((HiddenField)di.FindControl("hf_QuestionId")).Value); Question quest = dc.Questions.Single(q => q.QuestionId == QuestionId); TextBox tb = ((TextBox)di.FindControl(quest.ShortName.Replace(" ",""))); //tb is always null! } But it never finds the control. I've looked at the source code for the page and the control i want has the id: ctl00_cphContentMiddle_lv_Questions_ctrl0_Numberofacres For some reason when I look at the controls in the ListViewDataItem it has the ClientID: ctl00_cphContentMiddle_lv_Questions_ctrl0_ctl00 Why would it be changing Numberofacres to ctl00? Is there any way to work around this? UPDATE: Just to clarify, I am databinding my ListView in the Page_Init event. I then create the controls in the ItemBound event for my ListView. But based on what @Womp and MSDN are saying the controls won't actually be created until after the Load event (which is after the Page_Init event) and therefore are not in ViewState? Does this sound correct? If so am I just SOL when it comes to retrieving the values in my dynamic controls from my OnClick event?

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  • Square Brackets in Python Regular Expressions (re.sub)

    - by user1479984
    I'm migrating wiki pages from the FlexWiki engine to the FOSwiki engine using Python regular expressions to handle the differences between the two engines' markup languages. The FlexWiki markup and the FOSwiki markup, for reference. Most of the conversion works very well, except when I try to convert the renamed links. Both wikis support renamed links in their markup. For example, Flexwiki uses: "Link To Wikipedia":[http://www.wikipedia.org/] FOSwiki uses: [[http://www.wikipedia.org/][Link To Wikipedia]] both of which produce something that looks like I'm using the regular expression renameLink = re.compile ("\"(?P<linkName>[^\"]+)\":\[(?P<linkTarget>[^\[\]]+)\]") to parse out the link elements from the FlexWiki markup, which after running through something like "Link Name":[LinkTarget] is reliably producing groups <linkName> = Link Name <linkTarget = LinkTarget My issue occurs when I try to use re.sub to insert the parsed content into the FOSwiki markup. My experience with regular expressions isn't anything to write home about, but I'm under the impression that, given the groups <linkName> = Link Name <linkTarget = LinkTarget a line like line = renameLink.sub ( "[[\g<linkTarget>][\g<linkName>]]" , line ) should produce [[LinkTarget][Link Name]] However, in the output to the text files I'm getting [[LinkTarget [[Link Name]] which breaks the renamed links. After a little bit of fiddling I managed a workaround, where line = renameLink.sub ( "[[\g<linkTarget>][ [\g<linkName>]]" , line ) produces [[LinkTarget][ [[Link Name]] which, when displayed in FOSwiki looks like <[[Link Name> <--- Which WORKS, but isn't very pretty. I've also tried line = renameLink.sub ( "[[\g<linkTarget>]" + "[\g<linkName>]]" , line ) which is producing [[linkTarget [[linkName]] There are probably thousands of instances of these renamed links in the pages I'm trying to convert, so fixing it by hand isn't any good. For the record I've run the script under Python 2.5.4 and Python 2.7.3, and gotten the same results. Am I missing something really obvious with the syntax? Or is there an easy workaround?

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  • Why is using a common-lookup table to restrict the status of entity wrong?

    - by FreshCode
    According to Five Simple Database Design Errors You Should Avoid by Anith Sen, using a common-lookup table to store the possible statuses for an entity is a common mistake. Why is this wrong? I disagree that it's wrong, citing the example of jobs at a repair service with many possible statuses that generally have a natural flow, eg.: Booked In Assigned to Technician Diagnosing problem Waiting for Client Confirmation Repaired & Ready for Pickup Repaired & Couriered Irreparable & Ready for Pickup Quote Rejected Arguably, some of these statuses can be normalised to tables like Couriered Items, Completed Jobs and Quotes (with Pending/Accepted/Rejected statuses), but that feels like unnecessary schema complication. Another common example would be order statuses that restrict the status of an order, eg: Pending Completed Shipped Cancelled Refunded The status titles and descriptions are in one place for editing and are easy to scaffold as a drop-down with a foreign key for dynamic data applications. This has worked well for me in the past. If the business rules dictate the creation of a new order status, I can just add it to OrderStatus table, without rebuilding my code.

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  • SIFR, JAVASCRIPT & PHP - How to apply SIFR to dynamically loaded content.

    - by user311039
    Well here's the problem: I have a PHP index page which uses show/hide layers javascript. I am using the on menu.click function to show and hide content relevant to each menu. On.click all divs are hidden except the content for that menu item , which fades in. The content relating to each menu item are displayed within separate DIVS. The property is applied to all the text within all the divs. See: http://jobe-group.com/jobeco/uk/2010live/dynamic/content/index.php# The trouble is that SIFR only appears to be applied to the displayed on.load when the page is first loaded. When this is hidden and the other s shown through the "show" function they load in classic CSS fonts without the SIFR applied. Is this unavoidable with the SIFR setup. Or am I not calling the divs properly. I have set the SIFR to apply to the selector and indeed it works fine on the for the displayed on load. It doesn't work for the within other . In theory I would think its possible to load the SIFR on all divs on page.load even if those divs are presently visibility:hidden. What's the verdict on this? Hope someone can help. Cheers, John

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  • How to (kindly) ask your users to upgrade from IE6?

    - by nickf
    It's no secret at all that IE6 has been a major roadblock to the advancement of the web over the last few years. I couldn't count the number of hours I've spent bashing my head against a wall trying to fix or debug IE6 issues. The way I see it, there are two types of IE6 user. a) the poor corporate schmoe whose IT department doesn't want to upgrade in case something breaks, and b) the mums and dads of the world who think the internet is the blue E on their desktop (and I don't mean that in a nasty way). There's probably a couple of people who know about all the other browsers, but still choose to run IE6. They get what they deserve, IMO. Anyway, getting to the point, I'd say that 90% of my IE6-using visitors are in the the mums and dads category - they're not stupid, they just don't know WHY they should upgrade to IE7 or Firefox or whatever. How do I educate these people without pissing them off? Is there a nice and friendly website I can direct these people to, which explains the reasons for upgrading in plain language? Any mention of "security" or "web standards" I think would just come across as scary. I've just seen http://www.whatbrowser.org which seems to fit the bill nicely. It explains in very basic terms: what a web browser is why you'd want to upgrade it how old your current browser is (subtle hint to those with a 9 year old browser) ..aaaand it's in 22 languages. It's from Google but displays no bias (it links to Firefox, Chrome, Opera, Safari, Internet Explorer displayed in a random order).

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  • C# / Silverlight / WPF / Fast rendering lots of circles

    - by Walt W
    I want to render a lot of circles or small graphics within either silverlight or wpf (around 1000-10000) as fast and as frequently as possible. If I have to go to DX or OGL, that's fine, but I'm wondering about doing this within either of those two frameworks first (read: it's OK if an answer is WPF-only or Silverlight-only). Also, if there is a way to access DX through WPF and render on a surface that way, I would be interested in that as well. So, what's the fastest way to draw a load of circles? They can be as plain as necessary, but they do need to have a radius. Currently I'm using DrawingVisual and a DrawingContext.DrawEllipse() command for each circle, then rendering the visual to a RenderTargetBItmap, but it becomes very slow as the number of circles rises. By the way, these circles move every frame, so caching isn't really an option unless you're going to suggest caching the individual circles . . . But their sizes are dynamic, so I'm not sure that's a great approach.

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  • open Fancybox in tabs

    - by Prashant
    Hello all. I am using PHP + jQuery + Fancybox in my project. I have multiple tabs that get created dynamically. I have got a star icon on every tab header and on clicking them I want to open a fancybox. My tabs are basically ul-li with following dynamic code. $("#tabs").append("<li class='current'><a class='tab' id='tab_" + tabCnt + "<a href='#loginBox_div' class='login_link'> <img src='star.png' style='cursor:pointer'/> </a>" + "<a href='javascript:void(0);' class='remove'>x</a></li>"); in my index file : $(document).ready(function() { $("a.login_link").fancybox({ 'titlePosition' : 'inside', 'transitionIn' : 'none', 'transitionOut' : 'none' }); }); The problem is that when I click on star icon of first tab, the loginBox_div (fancybox) opens properly. But when my second tab is created and when I click on its star icon, the fancybox is not opening although the class is applied in second and successive tabs. No javascript errors too. Please show me the way. Thank you.

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  • Error running web project in eclipse

    - by DarkKnight
    I am a newbie to servlets. I created a dynamic web project in eclipse. I have following files in my project home.html validateServlet.java I have defined validated servlet as an action in home.html form. However when I run it, I get http status 404. Below is the hierarchy of my project Project Java Resources src com.servlets ValidateServlet.java build WebContent META-INF WEB-INF web.xml hello.html Contents of my web.xml are as follows: <?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web- app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0"> <display-name>Website</display-name> <servlet> <description></description> <display-name>ValidateServlet</display-name> <servlet-name>validate</servlet-name> <servlet-class>com.oracle.coen235.servlets.ValidateServlet</servlet-class> </servlet> </web-app> In my hello.html, action is specified as , What might be the issue? I guess I am not able to generate the class file for my servlet. Can anyone guide me through this problem?

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  • How can I use rows in a lookup table as columns in a MySQL query?

    - by TomH
    I'm trying to build a MySQL query that uses the rows in a lookup table as the columns in my result set. LookupTable id | AnalysisString 1 | color 2 | size 3 | weight 4 | speed ScoreTable id | lookupID | score | customerID 1 | 1 | A | 1 2 | 2 | C | 1 3 | 4 | B | 1 4 | 2 | A | 2 5 | 3 | A | 2 6 | 1 | A | 3 7 | 2 | F | 3 I'd like a query that would use the relevant lookupTable rows as columns in a query so that I can get a result like this: customerID | color | size | weight | speed 1 A C D 2 A A 3 A F The kicker of the problem is that there may be additional rows added to the LookupTable and the query should be dynamic and not have the Lookup IDs hardcoded. That is, this will work: SELECT st.customerID, (SELECT st1.score FROM ScoreTable st1 WHERE lookupID=1 AND st.customerID = st1.customerID) AS color, (SELECT st1.score FROM ScoreTable st1 WHERE lookupID=2 AND st.customerID = st1.customerID) AS size, (SELECT st1.score FROM ScoreTable st1 WHERE lookupID=3 AND st.customerID = st1.customerID) AS weight, (SELECT st1.score FROM ScoreTable st1 WHERE lookupID=4 AND st.customerID = st1.customerID) AS speed FROM ScoreTable st GROUP BY st.customerID Until there is a fifth row added to the LookupTable . . . Perhaps I'm breaking the whole relational model and will have to resolve this in the backend PHP code? Thanks for pointers/guidance. tom

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  • Why does Ruby have Rails while Python has no central framework?

    - by yar
    This is a(n) historical question, not a comparison-between-languages question: This article from 2005 talks about the lack of a single, central framework for Python. For Ruby, this framework is clearly Rails. Why, historically speaking, did this happen for Ruby but not for Python? (or did it happen, and that framework is Django?) Also, the hypothetical questions: would Python be more popular if it had one, good framework? Would Ruby be less popular if it had no central framework? [Please avoid discussions of whether Ruby or Python is better, which is just too open-ended to answer.] Edit: Though I thought this is obvious, I'm not saying that other frameworks do not exist for Ruby, but rather that the big one in terms of popularity is Rails. Also, I should mention that I'm not saying that frameworks for Python are not as good (or better than) Rails. Every framework has its pros and cons, but Rails seems to, as Ben Blank says in the one of the comments below, have surpassed Ruby in terms of popularity. There are no examples of that on the Python side. WHY? That's the question.

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  • Observer pattern and violation of Single Responsibility Principle

    - by Devil Jin
    I have an applet which repaints itself once the text has changed Design 1: //MyApplet.java public class MyApplet extends Applet implements Listener{ private DynamicText text = null; public void init(){ text = new DynamicText("Welcome"); } public void paint(Graphics g){ g.drawString(text.getText(), 50, 30); } //implement Listener update() method public void update(){ repaint(); } } //DynamicText.java public class DynamicText implements Publisher{ // implements Publisher interface methods //notify listeners whenever text changes } Isn't this a violation of Single Responsibility Principle where my Applet not only acts as Applet but also has to do Listener job. Same way DynamicText class not only generates the dynamic text but updates the registered listeners. Design 2: //MyApplet.java public class MyApplet extends Applet{ private AppletListener appLstnr = null; public void init(){ appLstnr = new AppletListener(this); // applet stuff } } // AppletListener.java public class AppletListener implements Listener{ private Applet applet = null; public AppletListener(Applet applet){ this.applet = applet; } public void update(){ this.applet.repaint(); } } // DynamicText public class DynamicText{ private TextPublisher textPblshr = null; public DynamicText(TextPublisher txtPblshr){ this.textPblshr = txtPblshr; } // call textPblshr.notifyListeners whenever text changes } public class TextPublisher implments Publisher{ // implements publisher interface methods } Q1. Is design 1 a SPR violation? Q2. Is composition a better choice here to remove SPR violation as in design 2.

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  • Apples, oranges, and pointers to the most derived c++ class

    - by Matthew Lowe
    Suppose I have a bunch of fruit: class Fruit { ... }; class Apple : public Fruit { ... }; class Orange: public Fruit { ... }; And some polymorphic functions that operate on said fruit: void Eat(Fruit* f, Pesticide* p) { } void Eat(Apple* f, Pesticide* p) { ingest(f,p); } void Eat(Orange* f, Pesticide* p) { peel(f,p); ingest(f,p); } OK, wait. Stop right there. Note at this point that any sane person would make Eat() a virtual member function of the Fruit classes. But that's not an option, because I am not a sane person. Also, I don't want that Pesticide* in the header file for my fruit class. Sadly, what I want to be able to do next is exactly what member functions and dynamic binding allow: typedef list<Fruit*> Fruits; Fruits fs; ... for(Fruits::iterator i=fs.begin(), e=fs.end(); i!=e; ++i) Eat(*i); And obviously, the problem here is that the pointer we pass to Eat() will be a Fruit*, not an Apple* or an Orange*, therefore nothing will get eaten and we will all be very hungry. So what I really want to be able to do instead of this: Eat(*i); is this: Eat(MAGIC_CAST_TO_MOST_DERIVED_CLASS(*i)); But to my limited knowledge, such magic does not exist, except possibly in the form of a big nasty if-statement full of calls to dynamic_cast. So is there some run-time magic of which I am not aware? Or should I implement and maintain a big nasty if-statement full of dynamic_casts? Or should I suck it up, quit thinking about how I would implement this in Ruby, and allow a little Pesticide to make its way into my fruit header?

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  • Java abstract visitor - guarantueed to succeed? If so, why?

    - by disown
    I was dealing with hibernate, trying to figure out the run-time class behind proxied instances by using the visitor pattern. I then came up with an AbstractVisitable approach, but I wonder if it will always produce correct results. Consider the following code: interface Visitable { public void accept(Visitor v); } interface Visitor { public void visit(Visitable visitorHost); } abstract class AbstractVisitable implements Visitable { @Override public void accept(Visitor v) { v.visit(this); } } class ConcreteVisitable extends AbstractVisitable { public static void main(String[] args) { final Visitable visitable = new ConcreteVisitable(); final Visitable proxyVisitable = (Visitable) Proxy.newProxyInstance( Thread.currentThread().getContextClassLoader(), new Class<?>[] { Visitable.class }, new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { return method.invoke(visitable, args); } }); proxyVisitable.accept(new Visitor() { @Override public void visit(Visitable visitorHost) { System.out.println(visitorHost.getClass()); } }); } } This makes a ConcreteVisitable which inherits the accept method from AbstractVisitable. In c++, I would consider this risky, since this in AbstractVisitable could be referencing to AbstractVisitable::this, and not ConcreteVisitable::this. I was worried that the code under certain circumstances would print class AbstractVisible. Yet the code above outputs class ConcreteVisitable, even though I hid the real type behind a dynamic proxy (the most difficult case I could come up with). Is the abstract visitor approach above guaranteed to work, or are there some pitfalls with this approach? What guarantees are given in Java with respect to the this pointer?

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  • Optimizing T-SQL where an array would be nice

    - by Polatrite
    Alright, first you'll need to grab a barf bag. I've been tasked with optimizing several old stored procedures in our database. This SP does the following: 1) cursor loops through a series of "buildings" 2) cursor loops through a week, Sunday-Saturday 3) has a huge set of IF blocks that are responsible for counting how many Objects of what Types are present in a given building Essentially what you'll see in this code block is that, if there are 5 objects of type #2, it will increment @Type_2_Objects_5 by 1. IF @Number_Type_1_Objects = 0 BEGIN SET @Type_1_Objects_0 = @Type_1_Objects_0 + 1 END IF @Number_Type_1_Objects = 1 BEGIN SET @Type_1_Objects_1 = @Type_1_Objects_1 + 1 END IF @Number_Type_1_Objects = 2 BEGIN SET @Type_1_Objects_2 = @Type_1_Objects_2 + 1 END IF @Number_Type_1_Objects = 3 BEGIN SET @Type_1_Objects_3 = @Type_1_Objects_3 + 1 END [... Objects_4 through Objects_20 for Type_1] IF @Number_Type_2_Objects = 0 BEGIN SET @Type_2_Objects_0 = @Type_2_Objects_0 + 1 END IF @Number_Type_2_Objects = 1 BEGIN SET @Type_2_Objects_1 = @Type_2_Objects_1 + 1 END IF @Number_Type_2_Objects = 2 BEGIN SET @Type_2_Objects_2 = @Type_2_Objects_2 + 1 END IF @Number_Type_2_Objects = 3 BEGIN SET @Type_2_Objects_3 = @Type_2_Objects_3 + 1 END [... Objects_4 through Objects_20 for Type_2] In addition to being extremely hacky (and limited to a quantity of 20 objects), it seems like a terrible way of handling this. In a traditional language, this could easily be solved with a 2-dimensional array... objects[type][quantity] += 1; I'm a T-SQL novice, but since writing stored procedures often uses a lot of temporary tables (which could essentially be a 2-dimensional array) I was wondering if someone could illuminate a better way of handling a situation like this with two dynamic pieces of data to store. Requested in comments: The columns are simply Number_Type_1_Objects, Number_Type_2_Objects, Number_Type_3_Objects, Number_Type_4_Objects, Number_Type_5_Objects, and CurrentDateTime. Each row in the table represents 5 minutes. The expected output is to figure out what percentage of time a given quantity of objects is present throughout each day. Sunday - Object Type 1 0 objects - 69 rows, 5:45, 34.85% 1 object - 85 rows, 7:05, 42.93% 2 objects - 44 rows, 3:40, 22.22% On Sunday, there were 0 objects of type 1 for 34.85% of the day. There was 1 object for 42.93% of the day, and 2 objects for 22.22% of the day. Repeat for each object type.

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  • Software Company Library

    - by dbemerlin
    Hi. A few days ago i had the idea to create a company library since my company has no training and many developers still develop as they did when they learned it 5 years ago. My hope is that they can lend books, read them and hopefully learn something from them (for example: object oriented programming or unit testing, which noone here knows how to use). After asking around most agreed that it was a good idea, so i brought my books, made a simple printed sheet with "Book A belongs to B" and "Developer A took the Book on dd.mm.yyyy" to get it started. Now i want to get some ideas for Books that i could add to the shelf (sadly from my own money since 100€/month for training is too much money for this multi-million euro company). We develop mostly PHP & MySQL so books specific to this topic would be preferred but i think if people learn other languages they might get ideas on how to develop better with the current language so other books are ok, too. Which books would you recommend? PS: Personally i'd like to add some Project Management books, too, as it's a topic i'm interested in, eventhough i'm just a junior developer (We've got Peopleware already, great book btw).

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  • Are .NET's regular expressions Turing complete?

    - by Robert
    Regular expressions are often pointed to as the classical example of a language that is not Turning complete. For example "regular expressions" is given in as the answer to this SO question looking for languages that are not Turing complete. In my, perhaps somewhat basic, understanding of the notion of Turning completeness, this means that regular expressions cannot be used check for patterns that are "balanced". Balanced meaning have an equal number of opening characters as closing characters. This is because to do this would require you to have some kind of state, to allow you to match the opening and closing characters. However the .NET implementation of regular expressions introduces the notion of a balanced group. This construct is designed to let you backtrack and see if a previous group was matched. This means that a .NET regular expressions: ^(?<p>a)*(?<-p>b)*(?(p)(?!))$ Could match a pattern that: ab aabb aaabbb aaaabbbb ... etc. ... Does this means .NET's regular expressions are Turing complete? Or are there other things that are missing that would be required for the language to be Turing complete?

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