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• How is time calculation performed by a computer?

  - by Jorge Mendoza

  I need to add a certain feature to a module in a given project regarding time calculation. For this specific case I'm using Java and reading through the documentation of the Date class I found out the time is calculated in milliseconds starting from January 1, 1970, 00:00:00 GMT. I think it's safe to assume there is a similar "starting date" in other languages so I guess the specific implementation in Java doesn't matter. How is the time calculation performed by the computer? How does it know exactly how many milliseconds have passed from that given "starting date and time" to the current date and time?

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• Exception while running an EJB program [closed]

  - by rajesh

  I'm a newbie to JEE. I'm trying a sample EJB3 program given in this website. while trying to run the client program, I get an exception like this [JBossManagedConnectionPool] Throwable while attempting to get a new connection: null org.jboss.resource.JBossResourceException: Could not create connection; - nested throwable: (org.jboss.resource.JBossResourceException: Failed to register driver for: com.mysql.jdbc.Driver; - nested throwable: (java.lang.ClassNotFoundException: com.mysql.jdbc.Driver from BaseClassLoader@4c19dd{VFSClassLoaderPolicy@35fd58{name=vfszip:/home/rajesh/workspace/jboss-5.1.0.GA/server/default/deploy/FirstJPAproject.jar/ domain=ClassLoaderDomain@17380fc{name=DefaultDomain parentPolicy=BEFORE parent=org.jboss.bootstrap.NoAnnotationURLClassLoader@76cbf7} roots=[MemoryContextHandler@9160338[path= context=vfsmemory://3j001-rho3wm-h8v3wfs4-1-h8v5pkwn-9u real=vfsmemory://3j001-rho3wm-h8v3wfs4-1-h8v5pkwn-9u], DelegatingHandler@25335794[path=FirstJPAproject.jar context=file:/home/rajesh/workspace/jboss-5.1.0.GA/server/default/deploy/ real=file:/home/rajesh/workspace/jboss-5.1.0.GA/server/default/deploy/FirstJPAproject.jar] I'm using Jboss5.1.0 and ejb 3.0 Please help me to get rid of this.

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• IL and case-sensitivity

  - by Ali .NET

  Quoted from A Brief Introduction To IL code, CLR, CTS, CLS and JIT In .NET CLS stands for Common Language Specifications. It is a subset of CTS. CLS is a set of rules or guidelines which if followed ensures that code written in one .NET language can be used by another .NET language. For example one rule is that we cannot have member functions with same name with case difference only i.e we should not have add() and Add(). This may work in C# because it is case-sensitive but if try to use that C# code in VB.NET, it is not possible because VB.NET is not case-sensitive. Based on above text I want to confirm two points here: Does the case-sensitivity of IL is a condition for member functions only, and not for member properties? Is it true that C# wouldn't be inter-operable with VB.NET if it didn't take care of the case sensitivity?

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• Design patterns and multiple programming languages

  - by Eduard Florinescu

  I am referring here to the design patterns found in the GOF book. First, how I see it, there are a few peculiarities to design pattern and knowing multiple languages, for example in Java you really need a singleton but in Python you can do without it you write a module, I saw somewhere a wiki trying to write all GOF patterns for JavaScript and all the entries were empty, I guess because it might be a daunting task to do that adaptation. If there is someone who is using design patterns and is programming multiple languages supporting the OOP paradigm and can give me a hint on how should I approach design patterns. An approach that might help me in all languages I use(Java, JavaScript, Python, Ruby): Can I write good application without knowing exactly the GOF design patterns or I might need just some of them which might be crucial and if yes which one, are there alternatives to GOF for specific languages, and should a programmer or a team make their own design patterns set?

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• *Code owner* system: is it an efficient way?

  - by sergzach

  There is a new developer in our team. An agile methodology is in use at our company. But the developer has another experience: he considers that particular parts of the code must be assigned to particular developers. So if one developer had created a program procedure or module it would be considered normal that all changes of the procedure/module would be made by him only. On the plus side, supposedly with the proposed approach we save common development time, because each developer knows his part of the code well and makes fixes fast. The downside is that developers don't know the system entirely. Do you think the approach will work well for a medium size system (development of a social network site)?

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• How to manage primary key while updating [migrated]

  - by Subin Jacob

  In the following table primaryKeyColumn is primary key. To maintain the data history I always uses the values with WHERE condition(WHERE StatusColumn=1) And will set the StatusColumn to 0 if the data is edited (So that I could keep the previous data). But the problem is, if I update it to 0 , I can't insert the same key to primarykeycolumn since the column validated for primary keys. How can I manage these kind of validations? what the mistake I did in this design? primaryKeyColumn ValueColumn StatusColumn ---------------- ----------- ------------ 2 Name1 1 3 Name2 1 4 Name3 0

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• When are Getters and Setters Justified

  - by Winston Ewert

  Getters and setters are often criticized as being not proper OO. On the other hand most OO code I've seen has extensive getters and setters. When are getters and setters justified? Do you try to avoid using them? Are they overused in general? If your favorite language has properties (mine does) then such things are also considered getters and setters for this question. They are same thing from an OO methodology perspective. They just have nicer syntax. Sources for Getter/Setter Criticism (some taken from comments to give them better visibility): http://www.javaworld.com/javaworld/jw-09-2003/jw-0905-toolbox.html http://typicalprogrammer.com/?p=23 http://c2.com/cgi/wiki?AccessorsAreEvil http://www.darronschall.com/weblog/2005/03/no-brain-getter-and-setters.cfm http://www.adam-bien.com/roller/abien/entry/encapsulation_violation_with_getters_and To state the criticism simply: Getters and Setters allow you to manipulate the internal state of objects from outside of the object. This violates encapsulation. Only the object itself should care about its internal state. And an example Procedural version of code. struct Fridge { int cheese; } void go_shopping(Fridge fridge) { fridge.cheese += 5; } Mutator version of code: class Fridge { int cheese; void set_cheese(int _cheese) { cheese = _cheese; } int get_cheese() { return cheese; } } void go_shopping(Fridge fridge) { fridge.set_cheese(fridge.get_cheese() + 5); } The getters and setters made the code much more complicated without affording proper encapsulation. Because the internal state is accessible to other objects we don't gain a whole lot by adding these getters and setters. The question has been previously discussed on Stack Overflow: http://stackoverflow.com/questions/565095/java-are-getters-and-setters-evil http://stackoverflow.com/questions/996179

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• Use a template to get alternate behaviour?

  - by Serge

  Is this a bad practice? const int sId(int const id); // true/false it doesn't matter template<bool i> const int sId(int const id) { return this->id = id; } const int MCard::sId(int const id){ MCard card = *this; this->id = id; this->onChange.fire(EventArgs<MCard&, MCard&>(*this, card)); return this->id; } myCard.sId(9); myCard.sId<true>(8); As you can see, my goal is to be able to have an alternative behaviour for sId. I know I could use a second parameter to the function and use a if, but this feels more fun (imo) and might prevent branch prediction (I'm no expert in that field). So, is it a valid practice, and/or is there a better approach?

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• Content Locking network with Microsoft Web Development tools? [closed]

  - by Jose Garcia

  I want my team to develop a content locking network for a client. But we dont know what is need to devlop such a network. We need to code it from Scratch. Please give us some advice. Content locking networks http://www.blamads.com/ adworkmedia.com These two networks are made with MS Tools it seems. FAQ http://support.blamads.com/index.php?pg=kb.book&id=5 https://www.adworkmedia.com/cpa-network-features.php

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• I'm creating my own scalable, rapid prototyping web server. How should I design it?

  - by Mike Willliams

  I'm going to create my own web server that focuses on scalability, rapid prototyping and the use of JavaScript as the server's scripting language, much like node.js. It will use a Model-View-Controller design pattern so a web application can support more concurrent users just by adding hardware -- and not having to redesign the software. Basically, I'm aiming to produce a framework that allows for fast and easy development of cloud applications without the need to write lots of boiler plate code. I've got some questions about this... How hard will it be to put MySQL in the cloud? How could I go about implementing this and make the resulting product free? Will I have to write my own engine or modify an existing one, if I do what should I watch out for? To make this scalable I need to adjust from one server to hundreds of servers this creates the requirement for the servers to be load balancing, how should I do this? If I balance based on the work load per server I would need gateway to handle all the incoming requests. Is it the right idea to have all the servers check into the gateway and update there status. By having the servers run through a gateway if the gateway dies all the incoming requests are ignored. I'm thinking that having all the servers maintain a list of each other, or at least a few I could rebuild the list of servers and establish a new gateway. Is it worth it? Or should I have a backup gateway that could switch out? Should I let the user choose? How should I pick which server handles the database and which handles the page serving? Should I spread the database so that queries are preformed on multiple servers? Which would theoretically improve performance. The servers would need to mirror the database at least once so that if a server goes down the database isn't corrupted. So this brings up writing another question, should I broadcast SQL queries so that all the servers can take a bit of the work load? If I do it that way wouldn't a query clog up the network so that other queries couldn't be preformed? What are my alternatives? Finally, is there a free solution already out there that might need a little modification that suits my needs?

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• Designing persistence schema for BigTable on AppEngine

  - by Vitalij Zadneprovskij

  I have tried to design the datastore schema for a very small application. That schema would have been very simple, if not trivial, using a relational database with foreign keys, many-to-many relations, joins, etc. But the problem was that my application was targeted for Google App Engine and I had to design for a database that was not relational. At the end I gave up. Is there a book or an article that describes design principles for applications that are meant for such databases? The books that I have found are about programming for App Engine and they don't spend many words about database design principles.

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• Inheritance, commands and event sourcing

  - by Arthis

  In order not to redo things several times I wanted to factorize common stuff. For Instance, let's say we have a cow and a horse. The cow produces milk, the horse runs fast, but both eat grass. public class Herbivorous { public void EatGrass(int quantity) { var evt= Build.GrassEaten .WithQuantity(quantity); RaiseEvent(evt); } } public class Horse : Herbivorous { public void RunFast() { var evt= Build.FastRun; RaiseEvent(evt); } } public class Cow: Herbivorous { public void ProduceMilk() { var evt= Build.MilkProduced; RaiseEvent(evt); } } To eat Grass, the command handler should be : public class EatGrassHandler : CommandHandler<EatGrass> { public override CommandValidation Execute(EatGrass cmd) { Contract.Requires<ArgumentNullException>(cmd != null); var herbivorous= EventRepository.GetById<Herbivorous>(cmd.Id); if (herbivorous.IsNull()) throw new AggregateRootInstanceNotFoundException(); herbivorous.EatGrass(cmd.Quantity); EventRepository.Save(herbivorous, cmd.CommitId); } } so far so good. I get a Herbivorous object , I have access to its EatGrass function, whether it is a horse or a cow doesn't matter really. The only problem is here : EventRepository.GetById<Herbivorous>(cmd.Id) Indeed, let's imagine we have a cow that has produced milk during the morning and now wants to eat grass. The EventRepository contains an event MilkProduced, and then come the command EatGrass. With the CommandHandler, we are no longer in the presence of a cow and the herbivorious doesn't know anything about producing milk . what should it do? Ignore the event and continue , thus allowing the inheritance and "general" commands? or throw an exception to forbid execution, it would mean only CowEatGrass, and HorseEatGrass might exists as commands ? Thanks for your help, I am just beginning with these kinds of problem, and I would be glad to have some news from someone more experienced.

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• c# class naming standards/guidelines

  - by Ben

  Over the years I've used various naming conventions for services in my applications for example: [ClassName]Service [ClassName]Manager [ClassName]Factory [ClassName]Provider [ClassName]Helper I generally only use the "Helper" suffix for utility classes that have no external dependencies. However I find that there is a bit of a cross-over between the others, and wondered if there was any recommendations/standards/guidelines on what to use and when?

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• How can I thoroughly evaluate a prospective employer?

  - by glenviewjeff

  We hear much about code smells, test smells, and even project smells, but I have heard no discussion about employer "smells" outside of the Joel Test. After much frustration working for employers with a bouquet of unpleasant corporate-culture odors, I believe it's time for me to actively seek a more mature development environment. I've started assembling a list of questions to help vet employers by identifying issues during a job interview, and am looking for additional ideas. I suppose this list could easily be modified by an employer to vet an employee as well, but please answer from the interviewee's perspective. I think it would be important to ask many of these questions of multiple people to find out if consistent answers are given. For the most part, I tried to put the questions in each section in the order they could be asked. An undesired answer to an early question will often make follow-ups moot. Values What constitutes "well-written" software? What attributes does a good developer have? Same question for manager. Process Do you have a development process? How rigorously do you follow it? How do you decide how much process to apply to each project? Describe a typical project lifecycle. Ask the following if they don't come up otherwise: Waterfall/iterative: How much time is spent in upfront requirements gathering? upfront design? Testing Who develops tests (developers or separate test engineers?) When are they developed? When are the tests executed? How long do they take to execute? What makes a good test? How do you know you've tested enough? What percentage of code is tested? Review What is the review process like? What percentage of code is reviewed? Design? How frequently can I expect to participate as code/design reviewer/reviewee? What are the criteria applied to review and where do the criteria come from? Improvement What new tools and techniques have you evaluated or deployed in the past year? What training courses have your employees been given in the past year? What will I be doing for the first six months in your company (hinting at what kind of organized mentorship/training has been thought through, if any) What changes to your development process have been made in the past year? How do you improve and learn from your mistakes as an organization? What was your organizations biggest mistake in the past year, and how was it addressed? What feedback have you given to management lately? Was it implemented? If not, why? How does your company use "best practices?" How do you seek them out from the outside or within, and how do you share them with each other? Ethics Tell me about an ethical problem you or your employees experienced recently and how was it resolved? Do you use open-source software? What open-source contributions have you made? Follow-Ups I liked what @jim-leonardo said on this Stack Overflow question: Really a thing to ask yourself: "Does this person seem like they are trying to recruit me and make me interested?" I think this is one of the most important bits. If they seem to be taking the attitude that the only one being interviewed is you, then they probably will treat you poorly. Good interviewers understand they have to sell the position as much as the candidate needs to sell themselves. @SethP added: Glassdoor.com is a good web site for researching potential employers. It contains information about how specific companies conduct interviews...

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• Rewrote GNU GPL v2 code in another language: can I change a license?

  - by Anton Gogolev

  I rewrote some parts of Mercurial (which is licensed under GNU GPL v2) in C#. Naturally, I looked a lot into original Python code and some parts are direct translations from Python to C#. Is is possible have "my code" licensed under different terms or to even make a part of a closed-source commercial application? If not, can I re-license "my-code" under LGPL, open-source it and then use this open-sourced C# library in my closed-source commercial application?

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• Is it legal and ethical to reverse engineer software to port it to another system?

  - by Igor Zinov'yev

  I love gaming, I love games that allow modding and I love linux. But the fact that most games right now are targeted for windows (consoles aside), most mods and modding tools are also targeted for windows. There is a certain modder called Boris Vorontsov that makes a famous visual overhaul mod series called ENB. What he does (or I think he does) is he enhances or changes the behavior of classes defined in the d3d9.dll library. Needless to say it almost never works under wine. Recently I have asked him if he would ever release his version of the library under some open license, and he said "no". Now that I think of it, even if he did release his code, he would have surely faced some legal problems. Now there is my question. Is it legal and ethical to reverse engineer his version of the library to adapt the wine's open source version of d3d9.dll to be able to run his mods?

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• Outsourcing a private project: can it be done?

  - by Stafford Williams

  I'm an employed software designer/developer/analyst/monkey and I'm pondering the possibility of outsourcing the coding component(s) of some private(ly funded) projects. I have never used outsourcing before and am hesitant due to the contractors i've seen in the workplace that seem to have a reverse relationship on renumeration vs results/quality. Has anyone had any luck with outsourcing private coding jobs and can you offer any pointers?

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• Do immutable objects and DDD go together?

  - by SnOrfus

  Consider a system that uses DDD (as well: any system that uses an ORM). The point of any system realistically, in nearly every use case, will be to manipulate those domain objects. Otherwise there's no real effect or purpose. Modifying an immutable object will cause it to generate a new record after the object is persisted which creates massive bloat in the datasource (unless you delete previous records after modifications). I can see the benefit of using immutable objects, but in this sense, I can't ever see a useful case for using immutable objects. Is this wrong?

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• How can I create a square 10x10 grid using nested for loops in Java? [migrated]

  - by help

  I'm trying to create a 10x10 grid using for loops in Java. I'm able to create rows going up and down but not repeating. for(int i = 1; i < temperatures.length; i++) { temperatures[i] = (temperatures[i-1] + 12) / 2; //takes average of 12 and previous temp } } public void paint(Graphics g) { for(int y = 1; y < 9; y++) { g.setColor(Color.black); g.drawRect(10, 10, 10, 10); g.drawRect(10, 10, 10, 20); g.drawRect(10, 10, 10, 30); g.drawRect(10, 10, 10, 40); g.drawRect(10, 10, 10, 50); g.drawRect(10, 10, 10, 60); g.drawRect(10, 10, 10, 70); g.drawRect(10, 10, 10, 80); g.drawRect(10, 10, 10, 90); g.drawRect(10, 10, 10, 100); for(int x = 1; x < 9; x++) { g.setColor(Color.black); g.drawRect(10, 10, 10, 10); g.drawRect(10, 10, 20, 10); g.drawRect(10, 10, 30, 10); g.drawRect(10, 10, 40, 10); g.drawRect(10, 10, 50, 10); g.drawRect(10, 10, 60, 10); g.drawRect(10, 10, 70, 10); g.drawRect(10, 10, 80, 10); g.drawRect(10, 10, 90, 10); g.drawRect(10, 10, 100, 10); } } } }

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• Is it OK to learn an algorithm from an open source project, and then implement it in a closed source project?

  - by Chris Barry

  Reference The post that started it all In order to clear up the original question I asked in a provocative manner, I have posed this question. If you learn an algorithm from an open source project, is it OK to use that algorithm in a separate closed sourced project? And if not, does that imply that you cannot use that knowledge ever again? If you can use it, what circumstance could that be? Just to clarify, I am not trying to evade a licence, otherwise I would not have asked the question in the first place. I believe this presents a difficult question and it is interesting to know where the debate can end up.

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• How does the ? make a quantifier lazy in regex

  - by Uriel Katz

  I've been looking into regex lately and figured that the ? operator makes the *,+, or ? lazy. My question is how does it do that? Is it that *? for example is a special operator, or does the ? have an effect on the *? In other words, does regex recognize *? as one operator in itself, or does regex recognize *? as the two separate operators * and ?? If it is the case that *? is being recognized as two separate operators, how does the ? affect the * to make it lazy. If ? means that the * is optional, shouldn't this mean that the * doesn't have to exists at all. If so, then in a statement .*? wouldn't regex just match separate letters and the whole string instead of the shorter string? Please explain, I'm desperate to understand.

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• Is there a best practice / standard approach to a free trial for a web app

  - by wobbily_col

  I have an idea for a web app, and would be interested in implementing it, and offering a free trial of say 5 uses before asking people to sign up. I can think of numerous ways of doing this (using cookies , logging IP adresses off the top of my head, limiting functionality). Is there a standard approach to this? Are there best practices? Are there any good tutorials on this? (I would prefer not to go the liited functionality route, as it will not show what the app is capable of).

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• Should I use Ruby version 1.8.7 or 1.9.2 to start developing Rails apps?

  - by BeachRunnerJoe

  Hello. I'm diving into RoR and I see that the current version of Rails (3.0.5) works with both 1.8.7 and 1.9.2. Currently, I have both versions of Ruby installed using RVM, but I'm wondering which version I should be using as I dive into Rails and start developing apps. I suppose I'd prefer to use the newest version (1.9.2), but I don't know the technologies well enough to know pros/cons of using either. Thanks so much!

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• how do you manage application performance reviews

  - by CoolBeans

  I have been trying to figure out ways to effectively do performance reviews before an install happens for all releases done by our team. Do you usually make this a part of code review process or do you handle it as a separate review task? FYI - we do not have a dedicated performance testing team. It is up to the developers to make sure the app performs well. The apps I am referring to are web applications.

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• Linux Learning curve for a 'Lifetime' windows user [closed]

  - by gary

  I am using windows for almost 8-10 years and have never worked on linux. Mostly i used to work in VB, VC++ MFC and little bit of .NET(C# and VB) so i didn't bother about Linux. But now when i got an opportunity to work with linux i dont want to miss it, here are my questions : Where can i find useful resources for Linux newbies? Which books/Tutorials will you suggest to start? Which distro shall i use? What was your experience while moving from Windows to Linux?

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