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• What is the difference between all-static-methods and applying a singleton pattern?

  - by shahensha

  I am making a database to store information about the users of my website (I am using stuts2 and hence Java EE technology). For the database I'll be making a DBManager. Should I apply singleton pattern here or rather make all it's methods static? I will be using this DBManager for basic things like adding, deleting and updating User profiles. Along with it, I'll use for all other querying purposes, for instance to find out whether a username already exists and to get all users for administrative purposes and stuff like that. My questions What is the benefit of singleton pattern? Which thing is most apt here? All static methods or a singleton pattern? Please compare both of them. regards shahensha P.S. The database is bigger than this. Here I am talking only about the tables which I'll be using for storing User Information.

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• What are the problems with a relatively large common library?

  - by Sam Pearson

  As long as the code in the base library is as loosely coupled as splitting it up into separate libraries, what's the problem? In general, having a lot of assemblies composing a .NET solution is painful. Plus, when code in one solution needs to be shared, it can just be added to the common library, rather than deciding which common library it should be added to or creating yet another library. edit: the question comes to me after using Smalltalk for a bit, where all the code is available to use, all the time.

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• I'm trying to understand hash tables - can someone explain it to me - clearly?

  - by Stevo

  I want to understand the correct use and implementation of hash tables in php (sorry). I read somewhere that an in-experienced programmer created a hash table and then iterated through it. Now, I understand why that is wrong but I haven't quite got the full knowledge to know if my understanding is correct (if you know what I mean). So could someone explain to me how to implement a hash table in php (presumably an associative array) and perhaps more importantly, how to access the values 'with a hash' and what that actually means?

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• How to estimate freight / shipping costs ??

  - by Vani

  Hi, I am working on a PHP web application and want to know the best way to estimate freight costs in USA. The site deals with construction materials that uses LTL or Truck loads. I found a few sites like www.freightCenter.com that provide quotes using webservice. Two drawbacks, its paid service and the other, my site response time is slow if I use the webservice. Is there a open source tool/logic avaliable for estimating shipping / freight costs?? Or a way to determine the rate per mile per pound for different freight classes? Thank you, Vani

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• Which is a better practice - helper methods as instance or static?

  - by Ilian Pinzon

  This question is subjective but I was just curious how most programmers approach this. The sample below is in pseudo-C# but this should apply to Java, C++, and other OOP languages as well. Anyway, when writing helper methods in my classes, I tend to declare them as static and just pass the fields if the helper method needs them. For example, given the code below, I prefer to use Method Call #2. class Foo { Bar _bar; public void DoSomethingWithBar() { // Method Call #1. DoSomethingWithBarImpl(); // Method Call #2. DoSomethingWithBarImpl(_bar); } private void DoSomethingWithBarImpl() { _bar.DoSomething(); } private static void DoSomethingWithBarImpl(Bar bar) { bar.DoSomething(); } } My reason for doing this is that it makes it clear (to my eyes at least) that the helper method has a possible side-effect on other objects - even without reading its implementation. I find that I can quickly grok methods that use this practice and thus help me in debugging things. Which do you prefer to do in your own code and what are your reasons for doing so?

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• Designing web-based plugin systems correctly so they don't waste as many resources?

  - by Xeoncross

  Many CMS systems which rely on third parties for much of their code often build "plugin" or "hooks" systems to make it easy for developers to modify the codebase's actions without editing the core files. This usually means an Observer or Event design pattern. However, when you look at systems like wordpress you see that on every page they load some kind of bootstrap file from each of the plugin's folders to see if that plugin will need to run that request. Its this poor design that causes systems like wordpress to spend many extra MB's of memory loading and parsing unneeded items each page. Are there alternative ways to do this? I'm looking for ideas in building my own. For example, Is there a way to load all this once and then cache the results so that your system knows how to lazy-load plugins? In other words, the system loads a configuration file that specifies all the events that plugin wishes to tie into and then saves it for future requests? If that also performs poorly, then perhaps there is a special file-structure that could be used to make educated guesses about when certain plugins are unneeded to fullfil the request. Any ideas? If anyone wants an example of the "plugin" concept you can find one here.

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• Why should a class be anything other than "abstract" or "final/sealed"

  - by Nicolas Repiquet

  After 10+ years of java/c# programming, I find myself creating either: abstract classes: contract not meant to be instantiated as-is. final/sealed classes: implementation not meant to serve as base class to something else. I can't think of any situation where a simple "class" (i.e. neither abstract nor final/sealed) would be "wise programming". Why should a class be anything other than "abstract" or "final/sealed" ? EDIT This great article explains my concerns far better than I can.

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• How to stop getting too focused on a train of thought when programming?

  - by LDM91

  I often find myself getting too focused on a train of thought when programming, which results in me having what I guess could be described as "tunnel vision". As a result of this I miss important details/clues, which means I waste a fair amount of time before finally deciding the path I'm taking to solve the task is wrong. Afterwards, I take a step back which almost always results in me discovering what I've missed in a lot less time.. It's becoming really frustrating as it feels like I'm wasting a lot of time and effort, so I was wondering if anyone else had experienced similar issues, and had some suggestions to stop going down dead ends and programming "blindly" as it were!

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• What is the difference between industrial development and open source development?

  - by Ida

  Intuitively, I think open source development should be much more "casual" than industrial development process (like in Microsoft). Because for OSS development: Duty separation is not that strict than in big companies (maybe developers == testers in open source development?) People come in and out of the open source community, much more frequently than in big companies However, above are just my guesses. I really want to know more about the major difference between the open source and industrial development. Is their division of duty totally different (e.g., is there a leader/manager-like role in open source development?)? Maybe it is their communication style that differs a lot? Or their workflow? Please share your opinions. Thanks a lot!

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• Absolute Top Programming Tips [closed]

  - by Eric

  I'm very intersted in the stuff that REALLY makes a critical difference to career in programming, other than intrinsic stuff like how smart your are, where you were born, etc... Some ideas: 1) Best approach to managing small, medium, and large teams. 2) Most important books to read. 3) Most important skills to know. 4) Correct balance of learning theory vs. just writing code. 5) A good approach to estimating time and cost of a project. 6) Etc... Please limit your answers. If you see somebody has already written your idea, please just vote for their response. I'd like to see what the community thinks are the true indicators of a successful career in our field.

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• Best Method of function parameter validation

  - by Aglystas

  I've been dabbling with the idea of creating my own CMS for the experience and because it would be fun to run my website off my own code base. One of the decisions I keep coming back to is how best to validate incoming parameters for functions. This is mostly in reference to simple data types since object validation would be quite a bit more complex. At first I debated creating a naming convention that would contain information about what the parameters should be, (int, string, bool, etc) then I also figured I could create options to validate against. But then in every function I still need to run some sort of parameter validation that parses the parameter name to determine what the value can be then validate against it, granted this would be handled by passing the list of parameters to function but that still needs to happen and one of my goals is to remove the parameter validation from the function itself so that you can only have the actual function code that accomplishes the intended task without the additional code for validation. Is there any good way of handling this, or is it so low level that typically parameter validation is just done at the start of the function call anyway, so I should stick with doing that.

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• Several domains using 302 redirect to our domain

  - by Yamaha32088

  I am wondering what implications we can run into if one of our dealers is redirecting several of their domains using a 302 to our domain. The reason they are doing this is because they want to have time to build on their current sites but still want some content on the domains they own. Currently our domain is under a Manual Penalty for back links that we are working on removing. I do not like the idea of them linking back to our site but I need logical reasons other than "because I don't want you to".

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• Is using ELSE bad programming?

  - by dave.b

  I've often come across bugs that have been caused by using the ELSE construct. A prime example is something along the lines of: If (passwordCheck() == false){ displayMessage(); }else{ letThemIn(); } To me this screams security problem. I know that passwordCheck is likely to be a boolean, but I wouldn't place my applications security on it. What would happen if its a string, int etc? I usually try to avoid using ELSE, and instead opt for two completely separate IF statements to test for what I expect. Anything else then either gets ignored OR is specifically handled. Surely this is a better way to prevent bugs / security issues entering your app. How do you guys do it?

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• Confused about implementing Single Responsibility Principle

  - by HichemSeeSharp

  Please bear with me if the question looks not well structured. To put you in the context of my issue: I am building an application that invoices vehicles stay duration in a parking. In addition to the stay service there are some other services. Each service has its own calculation logic. Here is an illustration (please correct me if the design is wrong): public abstract class Service { public int Id { get; set; } public bool IsActivated { get; set; } public string Name { get; set } public decimal Price { get; set; } } public class VehicleService : Service { //MTM : many to many public virtual ICollection<MTMVehicleService> Vehicles { get; set; } } public class StayService : VehicleService { } public class Vehicle { public int Id { get; set; } public string ChassisNumber { get; set; } public DateTime? EntryDate { get; set; } public DateTime? DeliveryDate { get; set; } //... public virtual ICollection<MTMVehicleService> Services{ get; set; } } Now, I am focusing on the stay service as an example: I would like to know at invoicing time which class(es) would be responsible for generating the invoice item for the service and for each vehicle? This should calculate the duration cost knowing that the duration could be invoiced partially so the like is as follows: not yet invoiced stay days * stay price per day. At this moment I have InvoiceItemsGenerator do everything but I am aware that there is a better design.

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• Is loose coupling w/o use cases an anti-pattern?

  - by dsimcha

  Loose coupling is, to some developers, the holy grail of well-engineered software. It's certainly a good thing when it makes code more flexible in the face of changes that are likely to occur in the foreseeable future, or avoids code duplication. On the other hand, efforts to loosely couple components increase the amount of indirection in a program, thus increasing its complexity, often making it more difficult to understand and often making it less efficient. Do you consider a focus on loose coupling without any use cases for the loose coupling (such as avoiding code duplication or planning for changes that are likely to occur in the foreseeable future) to be an anti-pattern? Can loose coupling fall under the umbrella of YAGNI?

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• How should I study programming languages?

  - by gcc

  I am a student of computer engineering. I have never done any programming before, and as you can understand, I don't know how to study it or how to make my own programs. My English is weak [edited for clarity - ed], and so if you don't like the choices I list, please feel free to provide others. How should I study? How should I learn programming languages? Study completely from a book. Don't study from a book, just try writing code. A mix of the two; study from a book, then try writing code. Study half the book, then write the code by hand on paper. Listed to the teacher, then try to solve general problems (those not from any specific chapter).

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• Building a template engine - starting point

  - by Anirudh

  We're building a Django-based project with a template component. This component will be separate from the project as such and can be Django/Python, Node, Java or whatever works. The template has to be rendered into HTML. The templates will contain references to objects with properties that are defined in the DB, say, a Bus. For eg, it could be something like [object type="vehicle" weight="heavy"] and it would have to pull a random object from the DB fulfilling the criteria : type="vehicle" weight="heavy" (bus/truck/jet) and then substitute that tag with an image, say, of a Bus. Also it would have to be able to handle some processing. Eg: What is [X type="integer" lte="10"] + [Y type="integer" lte="10"] [option X+Y correct_ans="true"] [option X-Y correct_ans="false"] [option X+y+1 correct_ans="false"] The engine would be expected to fill in a random integer value <= 10 for X and Y and show radioboxes for each of the options. Would also have to store the fact that the first option is the correct answer. Does it to make sense to write something from the scratch? Or is it better to use an existing templating system (like Django's own templating system) as a starting point? Any suggestions on how I can approach this?

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• Quick Tip - Speed a Slow Restore from the Transaction Log

  - by KKline

  Here's a quick tip for you: During some restore operations on Microsoft SQL Server, the transaction log redo step might be taking an unusually long time. Depending somewhat on the version and edition of SQL Server you've installed, you may be able to increase performance by tinkering with the readahead performance for the redo operations. To do this, you should use the MAXTRANSFERSIZE parameter of the RESTORE statement. For example, if you set MAXTRANSFERSIZE=1048576, it'll use 1MB buffers. If you...(read more)

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• How can I optimize my development machines files/dirs?

  - by LuxuryMode

  Like any programmer, I've got a lot of stuff on my machine. Some of that stuff is projects of my own, some are projects I'm working on for my employer, others are open-source tools and projects, etc. Currently, I have my files organized as follows: /Code --/development (things I'm sort of hacking on plus maybe libraries used in other projects) --/scala (organized by language...why? I don't know!) --/android --/ruby --/employer_name -- /mobile --/android --/ios --/open-source (basically my forks that I'm pushing commits back upstream from) --/some-awesome-oss-project --/another-awesome-one --/tools random IDE settings sprinkled in here plus some other apps As you can see, things are kind of a mess here. How can I keep things organized in some sort of coherent fashion?

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• Techniques for separating game model from presentation

  - by liortal

  I am creating a simple 2D game using XNA. The elements that make up the game world are what i refer to as the "model". For instance, in a board game, i would have a GameBoard class that stores information about the board. This information could be things such as: Location Size Details about cells on the board (occupied/not occupied) etc This object should either know how to draw itself, or describe how to draw itself to some other entity (renderer) in order to be displayed. I believe that since the board only contains the data+logic for things regarding it or cells on it, it should not provide the logic of how to draw things (separation of concerns). How can i achieve a good partitioning and easily allow some other entity to draw it properly? My motivations for doing so are: Allow multiple "implementations" of presentation for a single game entity Easier porting to other environments where the presentation code is not available (for example - porting my code to Unity or other game technology that does not rely on XNA).

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• Studying computer science - what am I getting myself into?

  - by clankercrusher

  I'm a student considering the possibility of studying computer science. I've picked up programming indie games and websites as a hobby and I really enjoy it. Despite my fairly positive experience, I somehow get the feeling that computer science in the business world will be completely different than do-it-for-fun game making. Since I'm interested in the field and I'd like to study well, I want to prepare myself for the onslaught. (If that’s even possible) What are some of the most important principals I need to know if I decide to study computer science? What will I need to know about computer science that a University probably won't teach me? Is there any way I can get hands on experience before or while I'm at a University? What am I getting myself into? P.S. Is this the right stack exchange site for this type of question?

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• How to deal with tautology in comments?

  - by Tamás Szelei

  Sometimes I find myself in situations when the part of code that I am writing is (or seems to be) so self-evident that its name would be basically repeated as a comment: class Example { /// <summary> /// The location of the update. /// </summary> public Uri UpdateLocation { get; set; }; } (C# example, but please refer to the question as language-agnostic). A comment like that is useless; what am I doing wrong? Is it the choice of the name that is wrong? How could I comment parts like this better? Should I just skip the comment for things like this?

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• Data Transformation Pipeline

  - by davenewza

  I have create some kind of data pipeline to transform coordinate data into more useful information. Here is the shell of pipeline: public class PositionPipeline { protected List<IPipelineComponent> components; public PositionPipeline() { components = new List<IPipelineComponent>(); } public PositionPipelineEntity Process(Position position) { foreach (var component in components) { position = component.Execute(position); } return position; } public PositionPipeline RegisterComponent(IPipelineComponent component) { components.Add(component); return this; } } Every IPipelineComponent accepts and returns the same type - a PositionPipelineEntity. Code: public interface IPipelineComponent { PositionPipelineEntity Execute(PositionPipelineEntity position); } The PositionPipelineEntity needs to have many properties, many which are unused in certain components and required in others. Some properties will also have become redundant at the end of the pipeline. For example, these components could be executed: TransformCoordinatesComponent: Parse the raw coordinate data into a Coordinate type. DetermineCountryComponent: Determine and stores country code. DetermineOnRoadComponent: Determine and store whether coordinate is on a road. Code: pipeline .RegisterComponent(new TransformCoordinatesComponent()) .RegisterComponent(new DetermineCountryComponent()) .RegisterComponent(new DetermineOnRoadComponent()); pipeline.Process(positionPipelineEntity); The PositionPipelineEntity type: public class PositionPipelineEntity { // Only relevant to the TransformCoordinatesComponent public decimal RawCoordinateLatitude { get; set; } // Only relevant to the TransformCoordinatesComponent public decimal RawCoordinateLongitude { get; set; } // Required by all components after TransformCoordinatesComponent public Coordinate CoordinateLatitude { get; set; } // Required by all components after TransformCoordinatesComponent public Coordinate CoordinateLongitude { get; set; } // Set in DetermineCountryComponent, not required anywhere. // Requires CoordinateLatitude and CoordinateLongitude (TransformCoordinatesComponent) public string CountryCode { get; set; } // Set in DetermineOnRoadComponent, not required anywhere. // Requires CoordinateLatitude and CoordinateLongitude (TransformCoordinatesComponent) public bool OnRoad { get; set; } } Problems: I'm very concerned about the dependency that a component has on properties. The way to solve this would be to create specific types for each component. The problem then is that I cannot chain them together like this. The other problem is the order of components in the pipeline matters. There is some dependency. The current structure does not provide any static or runtime checking for such a thing. Any feedback would be appreciated.

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• Why do we keep using CSV?

  - by Stephen

  Why do we keep using CSV? I recently made a shift to working the health domain and despite the wonderful work in data transfer standards, all data transfer is in CSV, both for reporting to external organisations, and for data migrations when implementing new systems. Unfortunately the use of CSV is the cause of the endless repetition of the same stupid errors, with the same waste of developer time. (bad escaping, failing to handle null fields etc.) I know we can do better, and anything between JSON and XML (depending on the instance) would be fine. (Most of the time this is data going from one MS SQLserver 2005 to another!) I feel as if each time I see this happening I am literally watching one developer waste anothers time. So why do we keep shafting each other? When will we stop?

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• Need to re-build an application - how?

  - by Tom

  For our main system, we have a small monitor application that sits outside our network and periodically tries to log in to verify the system still works. We have a problem with the monitor though in that the communications component set (Asta 3 inside Delphi applications) doesn't always connect through. Overall, I'd say it's about 95% reliable, but that other 5% kills the monitor since it will try to log in and hang on the connection attempt (no timeout in the component). This really isn't an issue on the client side of the system since the clients don't disconnect and reconnect repeatedly on the same application instance, but I need a way to make sure the monitor stays up and continues working even when the component fails on a run. I have a few ideas as to which way to have the program run, the main idea being to put the communications inside a threaded data module so that if one thread crashes then another thread can test later and the program keep going. Does this sound like a valid way to go? Any other ideas how to ensure a reliable monitoring application with a less than 100% reliable component? Thanks. P.S. Not sure these tags are the most appropriate. Tried including "system-reliability" as one, but not high enough rep to create.

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