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• How to Get Myself Up to Speed in Building a Java Web App

  - by Damian Wells

  I'm a new developer at a fairly large company and I'm working on a Java Web Application with a senior developer there. The Web App is built on top of an IBM stack (RAD, DB2, WebSphere) and basically uses JSPs and Servlets. The Web App is an internal tool to be used by employees to manage data coming from Excel files. So, there are lots of database interaction going around like SQL commands. My question is: I don't know much about JavaEE as a whole and only know a little about JSPs and Servlets and I would like to get myself up to speed so I can understand and contribute to the Web App as fast as I could. What resources (tutorials, links, etc) should I be looking at? Am I supposed to get a book about JavaEE or something that focuses just on JSPs and Servlets?

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• Changing my Sun SCJP certification to an Oracle one?

  - by Gugussee

  I hold a Sun SCJP from ten years ago or so. At first it was supposed to be a temporary certification (valid for a few years, I don't remember exactly: all I remember is that I had an expiration date on my certification card) then Sun changed their mind and decided the SCJP was lifetime valid. Another SCJP programmer told me I could change my cert so I contacted Sun (there was a procedure for that that I don't remember either) and received my new SCJP (without any expiration date). Now that Oracle bought Sun I was wondering: can I get somehow a Oracle/Sun SCJP paper/card/badge whatever knowing that I do own a SCJP? If anyone here holding an old SCJP changed it to an Oracle/Sun one (if such a thing exist), I'd be interested to hear what can be done. (btw I'm new here so I cannot create a new tag: maybe someone with more rep could create a Sun tag?)

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• How can I approach creating an efficient algorithm for maximizing value with these specific constraints?

  - by sway

  I'm having trouble coming up with an approach that isn't n^2 for this problem. Here's a contrived, simplified version I've come up with: Let's say you're a company that needs 4 employees to launch in a new city, a manager, two salespeople, and a customer support rep, and you magically know how much impact every candidate will have and how much salary they require to take the job. Your table of potential employees looks something like this: Name Position Salary Impact Adam Smith Manager 60,000 11 Allison Brown Salesperson 40,000 9 Brad Stewart Manager 55,000 9 ...etc (thousands of records) What algorithmic approach can be taken to find the maximum "impact" while still filling all the positions and remaining under, say, a 200,000 budget? Thanks!

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• Developing configuration syntax - best practise/rules/methods?

  - by Isaac

  I am currently developing a small application, which checks if provided data meets certain requirements. The requirements are actually a long list, and might be changing, so I defined a syntax which allows me to state all of the requirements briefly and in a seperate file. Now the overall requirements for the application have changed, and I need to change my configuration syntax. Which leeds me to wonder if there is methodoloy or best practise for developing such syntaxes. Currently what I do is I think about the requirements and come up with an initial syntax, start configuring the first few items and see how it works. If I come upon something that does not work well or not at all with the current syntax, I change the syntax, if possible in a backward compatible way. This somehow works for me, but it feels a bit like fishing in troubled water. Also I feel it does not nessessarly lead to the most concise and easy to understand/use syntax. So I was wondering what other people do, especially if there is a better approach to this.

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• C# Algorithms for * Operator

  - by Harsha

  I was reading up on Algorithms and came across the Karatsuba multiplication algorithm and a little wiki-ing led to the Schonhage-Strassen and Furer algorithms for multiplication. I was wondering what algorithms are used on the * operator in C#? While multiplying a pair of integers or doubles, does it use a combination of algorithms with some kind of strategy based on the size of the numbers? How could I find out the implementation details for C#?

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• Liskov substitution and abstract classes / strategy pattern

  - by Kolyunya

  I'm trying to follow LSP in practical programming. And I wonder if different constructors of subclasses violate it. It would be great to hear an explanation instead of just yes/no. Thanks much! P.S. If the answer is no, how do I make different strategies with different input without violating LSP? class IStrategy { public: virtual void use() = 0; }; class FooStrategy : public IStrategy { public: FooStrategy(A a, B b) { c = /* some operations with a, b */ } virtual void use() { std::cout << c; } private: C c; }; class BarStrategy : public IStrategy { public: BarStrategy(D d, E e) { f = /* some operations with d, e */ } virtual void use() { std::cout << f; } private: F f; };

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• If I implement a web-service, how do I respond to POST requests with JSON?

  - by Vova Stajilov

  I have to make a rather complex system for my diploma work. Logically it will consist of the following components: Database Web-service Management with web interface Client iOS application that will consume web-service I decided to implement all the first three components under .NET. Firstly I will create a database depending on the information load - this is clear. But then I need a web-service that will return data in JSON format for iOS clients to consume - that's obvious and not that hard to implement. For this I will use WCF technology. Now I have a question, if I implement the web-service, how will I be able to respond to POST requests with JSON? It probably involves WCF JSON or something related? But I also need some web pages as admin part, so will this web-application be able to consume my centralized web-services as well or I should develop it separately? I just want my web service to act like a set of controllers. There is a related question here but this doesn't quite reflect my question.

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• Why not have a High Level Language based OS? Are Low Level Languages more efficient?

  - by rtindru

  Without being presumptuous, I would like you to consider the possibility of this. Most OS today are based on pretty low level languages (mainly C/C++) Even the new ones such as Android uses JNI & underlying implementation is in C In fact, (this is a personal observation) many programs written in C run a lot faster than their high level counterparts (eg: Transmission (a bittorrent client on Ubuntu) is a whole lot faster than Vuze(Java) or Deluge(Python)). Even python compilers are written in C, although PyPy is an exception. So is there a particular reason for this? Why is it that all our so called "High Level Languages" with the great "OOP" concepts can't be used in making a solid OS? So I have 2 questions basically. Why are applications written in low level languages more efficient than their HLL counterparts? Do low level languages perform better for the simple reason that they are low level and are translated to machine code easier? Why do we not have a full fledged OS based entirely on a High Level Language?

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• Euler Problem 1 : Code Optimization / Alternatives [on hold]

  - by Sudhakar

  I am new bee into the world of Datastructures and algorithms from ground up. This is my attempt to learn. If the question is very plain/simple . Please bear with me. Problem: Find the sum of all the multiples of 3 or 5 below 1000. Code i worte: package problem1; public class Problem1 { public static void main(String[] args) { //******************Approach 1**************** long start = System.currentTimeMillis(); int total = 0; int toSubtract = 0; //Complexity N/3 int limit = 10000; for(int i=3 ; i<limit ;i=i+3){ total = total +i; } //Complexity N/5 for(int i=5 ; i<limit ;i=i+5){ total = total +i; } //Complexity N/15 for(int i=15 ; i<limit ;i=i+15){ toSubtract = toSubtract +i; } //9N/15 = 0.6 N System.out.println(total-toSubtract); System.out.println("Completed in "+(System.currentTimeMillis() - start)); //******************Approach 2**************** for(int i=3 ; i<limit ;i=i+3){ total = total +i; } for(int i=5 ; i<limit ;i=i+5){ if ( 0 != (i%3)) total = total +i; } } } Question 1 - Which best approach from the above code and why ? 2 - Are there any better alternatives ?

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• What is bootstrap listener in the context of Spring framework?

  - by jillionbug2fix

  I am studying Spring framework, in web.xml I added following which is a bootstrap listener. Can anyone give me a proper idea of what is a bootstrap listener? <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> You can see the doc here: ContextLoadListener Bootstrap listener to start up and shut down Spring's root WebApplicationContext. Simply delegates to ContextLoader as well as to ContextCleanupListener. This listener should be registered after Log4jConfigListener in web.xml, if the latter is used. As of Spring 3.1, ContextLoaderListener supports injecting the root web application context via the ContextLoaderListener(WebApplicationContext) constructor, allowing for programmatic configuration in Servlet 3.0+ environments. See WebApplicationInitializer for usage examples...

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• Pushing complete notifications to client

  - by ton.yeung

  So with cqrs, we accept that consistency is eventual. However, that doesn't mean that the user has to continually poll, or that eventual means an update has to take more then 500ms to sync. For the sake of UX, we want to at least give the illusion of consistency, or if not possible, be as transparent as possible. With that in mind, I have this setup: angularjs web client, consumes webapi restful services, sends commands to nservicebus command handlers, saves to neventstore, dispatches events to nservicebus event handlers, sends message to signalr hub, sends notifications to angularjs web client so with that setup, theoretically some initiates a request the server validates the request sends out the necessary commands In the mean time the client gets a 200 response updates the view: working on it gets message sometime later: done, here's the updated data Here's where things get interesting, each command could spawn multiple events. Not sure if this is a serious no, no, or not, but that's how it is currently. For example, a new customer spawns CustomerIDCreated, CustomerNameUpdated, CustomerAddressUpdated, etc... Which event handler needs to notify the client? Should all of them in a progress bar style update?

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• Configurable tables in sql database

  - by dot

  I have the following tables in my database: Config Table: ====================================== Start_Range | End Range | Config_id 10 | 15 | 1 ====================================== Available_UserIDs ========================== ID | UserID | Used_YN | 1 | 10 | t | 1 | 11 | f | 1 | 12 | f | 1 | 13 | f | 1 | 14 | f | 1 | 15 | f | ========================== Users ========================== UserId | FName | LName | 10 |John | Doe | ========================== This is used in a reservation system of sorts... which lets an administrator specify a range of numbers that will be assigned to users in the config table. Once the range has been defined, the system then populates the Available_userIDs table with all the numbers in between the range, and sets the Used_YN flag to false As users sign up, they grab the next user_id number that's not in use... and reserve it. Then the system adds a record to the Users table. Once the admin has specified a range, it is possible that they can change it. For example, they can start with 10-15... and then when the range is used up, they should be able to specify another range like 16 - 99. I've put a unique constraint on the Available_UserIDs table, as well as on the Users table - to ensure that UserIds can't be duplicated. My questions are as follows: What's the best way to prevent the admins from using a range that's already in use? I thought of the following options: -- check either the Users table to see if the start range or ending range numbers are being used. If they are, assume that all the numbers in between are in use too, and reject the range. -- let them specify whatever they want, try to populate the Available_UserIDs table. If there are duplicates, just ignore that specific error message from the database and continue on. How do I find gaps in the number ranges? For example, if they specify 10-15, and then 20-25, it'd be nice to be able to somehow suggest on my web page that 16-19 is currently available. I found this article: http://stackoverflow.com/questions/1312101/how-to-find-a-gap-in-running-counter-with-sql But it only seems to return the first available number... so in my example above, it would only return the number 16. I'm sure there's a simpler way to do things that I'm overlooking!

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• How to organize continuous code reviews?

  - by yegor256

  We develop in branches. Before a branch gets merged into the main stream (master branch) we review the changes made, by creating a new "code review" in Crucible. Reviewers add their comments to the code review and the ticket/branch gets bounced back to the author, if it needs to be improved. After the improvements are made we get this branch/ticket again back to the code review. We again create a new code review in Crucible, loosing all previously made comments. We simply start from scratch. It's a big waste of time. Do you know any tools that support a continuous mode for reviews, where we don't need to start from scratch every time, but can pick up the comments already made (re-start the review, so to speak).

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• Isn't MVC anti OOP?

  - by m3th0dman

  The main idea behind OOP is to unify data and behavior in a single entity - the object. In procedural programming there is data and separately algorithms modifying the data. In the Model-View-Controller pattern the data and the logic/algorithms are placed in distinct entities, the model and the controller respectively. In an equivalent OOP approach shouldn't the model and the controller be placed in the same logical entity?

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• When not to use Spring to instantiate a bean?

  - by Rishabh

  I am trying to understand what would be the correct usage of Spring. Not syntactically, but in term of its purpose. If one is using Spring, then should Spring code replace all bean instantiation code? When to use or when not to use Spring, to instantiate a bean? May be the following code sample will help in you understanding my dilemma: List<ClassA> caList = new ArrayList<ClassA>(); for (String name : nameList) { ClassA ca = new ClassA(); ca.setName(name); caList.add(ca); } If I configure Spring it becomes something like: List<ClassA> caList = new ArrayList<ClassA>(); for (String name : nameList) { ClassA ca = (ClassA)SomeContext.getBean(BeanLookupConstants.CLASS_A); ca.setName(name); caList.add(ca); } I personally think using Spring here is an unnecessary overhead, because The code the simpler to read/understand. It isn't really a good place for Dependency Injection as I am not expecting that there will be multiple/varied implementation of ClassA, that I would like freedom to replace using Spring configuration at a later point in time. Am I thinking correct? If not, where am I going wrong?

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• How to set up an environment for android app development?

  - by The Dark Knight

  I have been researching for sometime now regarding the process to install android sdk and associated tools . After visiting Android Developers page, i first installed the android sdk and then installed eclipse plugins for my indigo version from the install softwares options.However, it is mentioned in the developers page : Download the Android SDK. Install the ADT plugin for Eclipse (if you’ll use the Eclipse IDE). Download the latest SDK tools and platforms using the SDK Manager. I have downloaded the sdk and installed the adt plugins for eclipse.I just need to point the eclipse towards the location of the sdk. However, i am stuck at the last step which is asking me to download the latest tools using the sdk manager. The manager interface pops up and i see a lot of options there. I don't know which ones i must select and install. If some one can help me out here and tell me which options to choose and install(if possible, with a screen shot), it will be very beneficial for me.

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• Java - What methods to put in an interface and what to keep out

  - by lewicki

  I'm designing a file handler interface: public interface FileHandler { public void openFileHandler(String fileName); public void closeFileHandler(); public String readLine(); public String [] parseLine(String line); public String [] checkLine(String line[]); public void incrementLineCount(); public void incrementLineSuccessCount(); public void incrementLineErrorCount(); public int getLineCount(); public int getLineSuccessCount(); public int getLineErrorCount(); } It is soon apparent to me that these methods can't be made private. I don't want incrementLineCount to be public. What is proper way to design an interface like this?

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• Thread safe GUI programming

  - by James

  I have been programming Java with swing for a couple of years now, and always accepted that GUI interactions had to happen on the Event Dispatch Thread. I recently started to use GTK+ for C applications and was unsurprised to find that GUI interactions had to be called on gtk_main. Similarly, I looked at SWT to see in what ways it was different to Swing and to see if it was worth using, and again found the UI thread idea, and I am sure that these 3 are not the only toolkits to use this model. I was wondering if there is a reason for this design i.e. what is the reason for keeping UI modifications isolated to a single thread. I can see why some modifications may cause issues (like modifying a list while it is being drawn), but I do not see why these concerns pass on to the user of the API. Is there a limit imposed by an operating system? Is there a good reason these concerns are not 'hidden' (i.e. some form of synchronization that is invisible to the user)? Is there any (even purely conceptual) way of creating a thread safe graphics library, or is such a thing actually impossible? I found this http://blogs.operationaldynamics.com/andrew/software/gnome-desktop/gtk-thread-awareness which seems to describe GTK differently to how I understood it (although my understanding was the same as many people's) How does this differ to other toolkits? Is it possible to implement this in Swing (as the EDT model does not actually prevent access from other threads, it just often leads to Exceptions)

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• How does affliate marketing work, technically?

  - by Ron Gonzales

  There are lots of companies like Commision Junction that let you sell other people's products for a commission. How do these programs work, technically? Ie, are you simply given a link to the product you want to sell with an embedded ID in the URL? Does it involve cookies somehow? Do you take the order yourself and forward the information to the actual supplier of the goods/services? And how do you know if the program or the 'affliate network' isn't ripping you off by not creditting you for a sale?

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• How could there still not be a mysqldb module for Python 3?

  - by itsadok

  This SO question is now more than two years old. MySQL is an incredibly popular database engine, Python is an incredibly popular programming language, and Python 3 has been officially released two years ago, and was available even before that. What's more, the whole mysqldb module is just a layer translating Python's db-api to MySQL's API. It's not that big of a library. I must be missing something here. How come almost* nobody in the entire open source community has spent the (I'm guessing) two weeks it takes to port this lib? Is Python 3 that unpopular? Is the combination of python and mysql not as common as I assume? Or maybe it's just a lot harder to port mysqldb than I assume? Anyone know the inside story on this? * Now I see that this guy has done it, which takes some of the wind out of my question, but it still seems to little and too late to make sense.

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• How to write a product definition?

  - by Skarab

  I would like to learn how to write a software product definition. Therefore I am looking for online materials or books, which would help me to learn more about this topic. I would like to learn: what must be in what must not to be in how to make a product definition to sell internally the product finding balance between use case descriptions (the why), and feature descriptions (the how). ... I am aware that it is not something that can learn in 15 minutes but I think such a discussion could help me to have a good start.

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• When does the "Do One Thing" paradigm become harmful?

  - by Petr

  For the sake of argument here's a sample function that prints contents of a given file line-by-line. Version 1: void printFile(const string & filePath) { fstream file(filePath, ios::in); string line; while (file.good()) { getline(file, line); cout << line << endl; } } I know it is recommended that functions do one thing at one level of abstraction. To me, though code above does pretty much one thing and is fairly atomic. Some books (such as Robert C. Martin's Clean Code) seem to suggest breaking the above code into separate functions. Version 2: void printLine(const string & line) { cout << line << endl; } void printLines(fstream & file) { string line; while (file.good()) { getline(file, line); printLine(line); } } void printFile(const string & filePath) { fstream file(filePath, ios::in); printLines(file); } I understand what they want to achieve (open file / read lines / print line), but isn't it a bit of overkill? The original version is simple and in some sense already does one thing - prints a file. The second version will lead to a large number of really small functions which may be far less legible than the first version. Wouldn't it be, in this case, better to have the code at one place? At which point does the "Do One Thing" paradigm become harmful?

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• Is big (as much as big) size display (Monitor) always better for Development?

  - by Jitendra Vyas

  Is bigger size display ( Monitor) always better for Development? I'm going to buy a new LCD Monitor. I mostly work in Adobe Photoshop, HTML, CSS, jQuery and Wordpress. Budget is not a problem. Many options are there for LCD Monitor SIZE My questions are Would it better for maximum size, or large size monitor are not good always? Would it better to buy 21.5 inch x 2 than one 30 inch monitor? Which monitor size would you would prefer between the size of 21.5 inch - 30 inch, if bugdet is not a problem?

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• How to hire support people?

  - by Martin

  I manage a tech support team at a mid-sized software company. We are the last line of support, so issues that we can't fix need to be escalated to the development team. When I joined the company, our team wasn't capable of much beyond using a specific set of troubleshooting steps to solve known issues and escalating anything else to the developers. It's always been a goal of mine for our team to shoulder as much of the support burden as possible without ever bothering a developer. Over the past few years, I, along with several new hires I've made, have made pretty good progress in that direction. We've coded our own troubleshooting tools which now ship with several of our products. When users have never-before-seen issues, we analyze stack traces and troubleshoot down to the code level, and if we need to submit a bug, half the time we've already identified in the code where in the code the bug is and offered a patch to fix it. Here's the problem I've always had: finding support people capable of the work I've described above is really difficult. I've hired 3 people in the past 3 years, and I've probably looked at several thousand resumes and conducted several hundred phone screens to do so. I know it's pretty well accepted that hiring good people is tough in the tech industry, but it seems that support is especially difficult -- there are clearly thousands of people walking around calling themselves support analysts, but 99%+ of them seemingly aren't capable of anything beyond reading a script. I'm curious if anyone has experience recruiting the sort of folks I'm talking about, and if you have any suggestions to share. We've tried all sorts of things -- different job titles/descriptions, using headhunters, etc. And while we've managed to hire a few good folks, it's basically taken us a year to find an appropriate candidate for each opening we've had, and I can't help but wonder if there's something we could be doing differently.

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• Do you think code is self documenting?

  - by Desolate Planet

  This is a question that was put to me many years ago as a gradute in a job interview and it's kind of picked at my brain now and again and I've never really found a good answer that satisfies me. The interviewer in question was looking for a black and white answer, there was no middle ground. I never got the chance to ask about the rationale behind the question, but I'm curious why that question would be put to a developer and what you would learn from a yes or no answer? From my own point of view, I can read Java, Python, Delphi etc, but if my manager comes up to me and asks me how far along in a project I am and I say "The code is 80% complete" (and before you start shooting me down, I've heard this uttered in a couple of offices by developers), how exactly is that self documenting? Apologies if this question seems strange, but I'd rather ask and get some opinions on it to gain a better understanding of why it would be put to someone in an interview.

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