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• C# inherit from a class in a different DLL

  - by Onno

  I need to make an application that needs to be highly modular and that can easily be expanded with new functionality. I've thought up a design where I have a main window and a list of actions that are implemented using a strategy pattern. I'd like to implement the base classes/interfaces in a DLL and have the option of loading actions from DLL's which are loaded dynamically when the application starts. This way the main window can initiate actions without having to recompile or redistribute a new version. I just have to (re)distribute new DLL's which I can update dynamically at runtime. This should enable very easy modular updating from a central online source. The 'action' DLL's all inherit their structure from the code defined in the the DLL which defines the main strategy pattern structure and it's abstract factory. I'd like to know if C# /.Net will allow such a construction. I'd also like to know whether this construction has any major problems in terms of design.

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• Can this word search algorithm be made faster?

  - by Ashwin Singh

  Problem: Find a match of word S in text T Given: S and T are part of spoken and written English. Example: Match 'Math' in 'I love Mathematics' NOTE: Ignore CASES. My algorithm: STEP 1) Convert S, T to char[] STEP 2) for i=0, i < T.length , i++ STEP 3) for j=S.length-1, j>0 , j-- STEP 3 is the magic, instead of going about matching M,A,T,H, this matches M, H, T and finally A. This helps in eliminating a lot of possible partial matches. For example, if I go sequentially like M A as in Boyer Moore's method ... it can match Matter, Mass, Matchstick etc. using M _ _ H will bring down size of partial matches. STEP 4) if S[j]!=T[i] -> break; else if j==i -> PRINT MATCH

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• Where can I find a good Hibernate Criteria tutorial that doesn't use cats and kittens? [closed]

  - by cbmeeks

  I've been using Hibernate a little while (HQL) and want to try Criteria's for a few scenarios we have here. I'm trying to get a few inner joins (2 layers deep) and am struggling a little. I go to the official site and they teach by cats and kittens. I don't care about cats and kittens and find the analogy hard to follow. Orders, details, shipments, etc. Nice, boring business references is what I enjoy. I tried to Google it but all I get are early 2000's websites with so many flashing GIF's, cluttered displays, flash overs and "tummy tuck" ads I want to puke. Why can't the java world have sites like http://guides.rubyonrails.org/? And no, I'm not advocating I volunteer to create a similar site. :-) Anyway, any good site that can give a nice tutorial on Criteria based searches would be appreciated.

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• Session serialization in JavaEE environment

  - by Ionut

  Please consider the following scenario: We are working on a JavaEE project for which the scalability starts to become an issue. Up until now, we were able to scale up but this is no longer an option. Therefore we need to consider scaling out and preparing the App for a clustered environment. Our main concern right now is serializing the user sessions. Sadly, we did not consider from the beginning the issue and we are encountering the following excetion: java.io.WriteAbortedException: writing aborted; java.io.NotSerializableException: org.apache.catalina.session.StandardSessionFacade I did some research and this exception is thrown because there are objects stored on the session which does not implement the Serializable interface. Considering that all over the app there are quite a few custom objects which are stored on the session without implementing this interface, it would require a lot of tedious work and dedication to fix all these classes declaration. We will fix all this declarations but the main concern is that, in the future, there may be a developer which will add a non Serializable object on the session and break the session serialization & replication over multiple nodes. As a quick overview of the project, we are developing using a home grown framework based on Struts 1 with the Servlet 3.0 API. This means that at this point, we are using the standard session.getAttribute() and session.setAttribute() to work with the session and the session handling is scattered all over the code base. Besides updating the classes of the objects stored on session and making sure that they implement the Serializable interface, what other measures of precaution should we take in order to ensure a reliable Session replication capability on the Application layer? I know it is a little bit late to consider this but what would be the best practice in this case? Furthermore, are there any other issues we should consider regarding this transition? Thank you in advance!

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• How do I classify using SVM Classifier in Matlab?

  - by Gomathi

  I'm on a project of liver tumor segmentation and classification. I used Region Growing and FCM for liver and tumor segmentation respectively. Then, I used Gray Level Co-occurence matrix for texture feature extraction. I have to use Support Vector Machine for Classification. But I don't know how to normalize the feature vectors. Can anyone tell how to program it in Matlab? To the GLCM program, I gave the tumor segmented image as input. Was I correct? If so, I think, then, my output will also be correct. I gave the parameters exactly as in the example provided in the documentation itself. The output I obtained was stats = autoc: [1.857855266614132e+000 1.857955341199538e+000] contr: [5.103143332457753e-002 5.030548650257343e-002] corrm: [9.512661919561399e-001 9.519459060378332e-001] corrp: [9.512661919561385e-001 9.519459060378338e-001] cprom: [7.885631654779597e+001 7.905268525471267e+001] cshad: [1.219440700252286e+001 1.220659371449108e+001] dissi: [2.037387269065756e-002 1.935418927908687e-002] energ: [8.987753042491253e-001 8.988459843719526e-001] entro: [2.759187341212805e-001 2.743152140681436e-001] homom: [9.930016927881388e-001 9.935307908219834e-001] homop: [9.925660617240367e-001 9.930960070222014e-001] maxpr: [9.474275457490587e-001 9.474466930429607e-001] sosvh: [1.847174384255155e+000 1.846913030238459e+000] savgh: [2.332207337361002e+000 2.332108469591401e+000] svarh: [6.311174784234007e+000 6.314794324825067e+000] senth: [2.663144677055123e-001 2.653725436772341e-001] dvarh: [5.103143332457753e-002 5.030548650257344e-002] denth: [7.573115918713391e-002 7.073380266499811e-002] inf1h: [-8.199645492654247e-001 -8.265514568489666e-001] inf2h: [5.643539051044213e-001 5.661543271625117e-001] indnc: [9.980238521073823e-001 9.981394883569174e-001] idmnc: [9.993275086521848e-001 9.993404634013308e-001] The thing is, I run the program for three images. But all three gave me the same output. When I used graycoprops() stat = Contrast: 4.721877658740964e+005 Correlation: -3.282870417955449e-003 Energy: 8.647689474127760e-006 Homogeneity: 8.194621855726478e-003 stat = Contrast: 2.817160447307697e+004 Correlation: 2.113032196952781e-005 Energy: 4.124904827799189e-004 Homogeneity: 2.513567163994905e-002 stat = Contrast: 7.086638436309059e+004 Correlation: 2.459637878221028e-002 Energy: 4.640677159445994e-004 Homogeneity: 1.158305728309460e-002 The images are:

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• When to use identity comparison instead of equals?

  - by maaartinus

  I wonder why would anybody want to use identity comparison for fields in equals, like here (Java syntax): class C { private A a; public boolean equals(Object other) { // standard boring prelude if (other==this) return true; if (other==null) return false; if (other.getClass() != this.getClass()) return false; C c = (C) other; // the relevant part if (c.a != this.a) return false; // more tests... and then return true; } // getter, setters, hashCode, ... } Using == is a bit faster than equals and a bit shorter (due to no need for null tests), too, but in what cases (if any) you'd say it's really better to use == for fields inside equals?

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• What have you seen go wrong when introducing SCRUM?

  - by cringe

  What was the single point of failure encountered when your company decided to replace the current processes with SCRUM? Can you give me some examples of things that have gone really wrong when a company tried to introduce SCRUM? I'd like to hear your anecdotes, something you experienced yourself, the big fail that you saw coming but couldn't prevent. I hear a lot of concern about missing documentation on decisions about the implementation details, and about story sizes and detail level of the stories.

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• Using Domain name in EULA of a software rather than my name in the Licensor field

  - by user17330

  I intend to sell a software solution.I have already registered a domain but i dont have a registered company.Can i use my website/domain name eg:myproduct.com for the licensor field in the EULA rather than using myname.I will renew my domain yearly is there a problem with this.Do you know any software companies that work like this.Im confused about the users point of view will they find it a bit different. Please help me out.

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• Coding a web browser on Windows using a layout engine?

  - by samual johnson

  I've never attempted anything like this before but what I want to do is code a browser for Windows. I know that I can use the web-browser control that Microsoft has released, but I'm interested in seeing how the problem is solved from a lower level. So I want to know what layout engine I should be looking at? Or is a layout engine the best way to go? I've been looking at WebKit, but it seems rather Mac-centric, so I'm wondering if there are any more practical one's for windows? Has Microsoft released the source code for their webbrowser winforms control in the .Net framework? That would be dependent on the CLR anyway, I suppose? Any suggestions?

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• Best Creational Pattern for loggers in a multi-threaded system?

  - by Dipan Mehta

  This is a follow up question on my past questions : Concurrency pattern of logger in multithreaded application As suggested by others, I am putting this question separately. As the learning from the last question. In a multi-threaded environment, the logger should be made thread safe and probably asynchronous (where in messages are queued while a background thread does writing releasing the requesting object thread). The logger could be signleton or it can be a per-group logger which is a generalization of the above. Now, the question that arise is how does logger should be assigned to the object? There are two options I can think of: 1. Object requesting for the logger: Should each of the object call some global API such as get_logger()? Such an API returns "the" singleton or the group logger. However, I feel this involves assumption about the Application environment to implement the logger -which I think is some kind of coupling. If the same object needs to be used by other application - this new application also need to implement such a method. 2. Assign logger through some known API The other alternative approach is to create a kind of virtual class which is implemented by application based on App's own structure and assign the object sometime in the constructor. This is more generalized method. Unfortunately, when there are so many objects - and rather a tree of objects passing on the logger objects to each level is quite messy. My question is there a better way to do this? If you need to pick any one of the above, which approach is would you pick and why? Other questions remain open about how to configure them: How do objects' names or ID are assigned so that will be used for printing on the log messages (as the module names) How do these objects find the appropriate properties (such as log levels, and other such parameters) In the first approach, the central API needs to deal with all this varieties. In the second approach - there needs to be additional work. Hence, I want to understand from the real experience of people, as to how to write logger effectively in such an environment.

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• Open source projects, how to choose?!

  - by Dhaivat Pandya

  I would like to join an open source project since I think I am good enough at programming to progress onto reading others code and to modify it. But the proble mis, how would I choose an open source project to work on? I know many languages and chief ones that I am good are python, C++ (not really very good at C, the lack of object orientation is difficult for me) and Java. For c++, I am proficient wit Qt. I would like to start with something that isn't huge, and hasn't reached a phase where the bugs are so complicated it would take me a month to understand what affects the bug. Any suggestions? At the current time, I don't use any libraries in either of the mentioned libraries that I would need to modify (AFAIK).

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• How does session middleware generally verify browser sessions?

  - by BBnyc

  I've been using session middleware to build web apps for years: from PHP's built-in session handling layer to node's connect session middleware. However, I've never tried (or needed) to roll my own session handling layer. How would one go about it? What sort of checks are necessary to provide at least some modicum of security against HTTP session highjacking? I figure setting a cookie with a token to keep track of the session, and then perhaps some check to see that the originating IP address of the session doesn't change and that the client browser software remains consistent. Hoping to hear about current best-practices...

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• Recommened design pattern to handle multiple compression algorithms for a class hierarchy

  - by sgorozco

  For all you OOD experts. What would be the recommended way to model the following scenario? I have a certain class hierarchy similar to the following one: class Base { ... } class Derived1 : Base { ... } class Derived2 : Base { ... } ... Next, I would like to implement different compression/decompression engines for this hierarchy. (I already have code for several strategies that best handle different cases, like file compression, network stream compression, legacy system compression, etc.) I would like the compression strategy to be pluggable and chosen at runtime, however I'm not sure how to handle the class hierarchy. Currently I have a tighly-coupled design that looks like this: interface ICompressor { byte[] Compress(Base instance); } class Strategy1Compressor : ICompressor { byte[] Compress(Base instance) { // Common compression guts for Base class ... // if( instance is Derived1 ) { // Compression guts for Derived1 class } if( instance is Derived2 ) { // Compression guts for Derived2 class } // Additional compression logic to handle other class derivations ... } } As it is, whenever I add a new derived class inheriting from Base, I would have to modify all compression strategies to take into account this new class. Is there a design pattern that allows me to decouple this, and allow me to easily introduce more classes to the Base hierarchy and/or additional compression strategies?

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• How to get that first development job

  - by cju

  I have been in QA for 10 years, trying to get into developement for about 5 of them. I have taken classes in C++, Java and C#. I was able to write some tools and unit tests in C# at my current job and (by all accounts) did a good job of it. However, 8 months ago, my employer tasked me with the responsibility of establishing the new QA group. Now, I'm doing manual testing and deployment with no promise of returning to development. I have looked at the job boards and there are a lot of jobs for Web developers and wondered how I could break into that. I've picked up some books on Ruby on Rails that I plan to work through on the Mac at home, but I'm not sure employers would be interested in anything but commercial web development. Do you have any suggestions on how I can use my experience to get a job as a junior developer? And I mean one that entailes programming...the postings I've seen for junior developer amount to doing all the grunt work besides coding. They should just call them "Technical Secretaries".

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• What ever happened to the Google AJAX Search API

  - by John

  I am looking to query the main Google search however all references including stackoveflow point to the Google AJAX Search API. The odd thing is that it does not seem to exist any more not even a note to say it is depreciated? The old links point to main Google code site. If I look at the list of API's on that site the API it replaced is there Web Search API (Deprecated) which links back to same page but not the Google AJAX Search API. Further Google searching is not being helpful either, many blog posts pointing to the same Google site (http://code.google.com/apis/ajaxsearch/) that has no content and redirects to the same place? Just to prove it did exist I have found it on the way back machine however the last snapshot did not show any special unusual message.

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• Can I migrate a clone of Google Code repository into Github?

  - by David Conde

  I want to create a clone of a Google Code repository, which I cannot download due to Country restrictions and I want to migrate that clone into Github, which I can use without any problem. The thing is I have a Github account and I can browse through GoogleCode but I cannot take my TortoiseHg and clone a repo just like that because I'm from Cuba and I get a lovely Google page saying that I cannot go into Google code. I'm guessing you know how I manage to browse :) I would like to import a mercurial repository into my Github repo, my questions: Is it possible? How can I do it?

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• What are the algorithms that are used for working with large data in popular web applications

  - by Moss Farmer

  I am looking for some well known algorithms that can be considered while handling very large amount of data.(Edit- By large amount of data I refer to records in a database excluding blobs). These algorithms if not in totality but in parts may be used in big web applications like Twitter, Last.fm , Amazon ,etc. Specifically, I'm looking for names or links to such algorithms. My primary interest lies in developing a very deep understanding on working with large database records and writing efficient code for working with the same.

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• The cost of longer delay between development and QA

  - by Neil N

  At my current position, QA has become a bottleneck. We have had the unfortunate occurence of features being held out of the current build so that QA could finish testing. This means features that are done being developed may not get tested for 2-3 weeks after the developer has already moved on. With dev moving faster thean QA, this time gap is only going to get bigger. I keep flipping through my copy of Code Compelte, looking for a "Hard Data" snippet that shows the cost of fixing defects grows exponentially the longer it exists. Can someone point me to some studies that back up this concept? I am trying to convince the powers that be that the QA bottleneck is a lot more costly than they think.

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• Producer-consumer pattern with consumer restrictions

  - by Dan

  I have a processing problem that I am thinking is a classic producer-consumer problem with the two added wrinkles that there may be a variable number of producers and there is the restriction that no more than one item per producer may be consumed at any one time. I will generally have 50-100 producers and as many consumers as CPU cores on the server. I want to maximize the throughput of the consumers while ensuring that there are never more than one work item in process from any single producer. This is more complicated than the classic producer-consumer problem which I think assumes a single producer and no restriction on which work items may be in progress at any one time. I think the problem of multiple producers is relatively easily solved by enqueuing all work items on a single work queue protected by a critical section. I think the restriction on simultaneously processing work items from any single producer is harder because I cannot think of any solution that does not require each consumer to notify some kind of work dispatcher that a particular work item has been completed so as to lift the restriction on work items from that producer. In other words, if Consumer2 has just completed WorkItem42 from Producer53, there needs to be some kind of callback or notification from Consumer2 to a work dispatcher to allow the work dispatcher to release the next work item from Producer53 to the next available consumer (whether Consumer2 or otherwise). Am I overlooking something simple here? Is there a known pattern for this problem? I would appreciate any pointers.

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• AJAX driven "page complete" function? Am I doing it right?

  - by Julian H. Lam

  This one might get me slaughtered, since I'm pretty sure it's bad coding practice, so here goes: I have an AJAX driven site which loads both content and javascript in one go using Mootools' Request.HTML. Since I have initialization scripts that need to be run to finish "setting up" the template, I include those in a function called pageComplete(), on every page Visiting one page to another causes the previous pageComplete() function to no longer apply, since a new one is defined. The javascript function that loads pages dynamically calls pageComplete() blindly when the AJAX call is completed and is loaded onto the page: function loadPage(page, params) { // page is a string, params is a javascript object if (pageRequest && pageRequest.isRunning) pageRequest.cancel(); pageRequest = new Request.HTML({ url: '<?=APPLICATION_LINK?>' + page, evalScripts: true, onSuccess: function(tree, elements, html) { // Empty previous content and insert new content $('content').empty(); $('content').innerHTML = html; pageComplete(); pageRequest = null; } }).send('params='+JSON.encode(params)); } So yes, if pageComplete() is not defined in one the pages, the old pageComplete() is called, which could potentially be disastrous, but as of now, every single page has pageComplete() defined, even if it is empty. Good idea, bad idea?

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• How do you track bugs in your personal projects?

  - by bedwyr

  I'm trying to decide if I need to reassess my defect-tracking process for my home-grown projects. For the last several years, I really just track defects using TODO tags in the code, and keeping track of them in a specific view (I use Eclipse, which has a decent tagging system). Unfortunately, I'm starting to wonder if this system is unsustainable. The defects I find are typically associated with a snippet of code I'm working on; bugs which are not immediately understood tend to be forgotten, or ignored. I wrote an application for my wife which has had a severe defect for almost 9 months, and I keep forgetting to fix it. What mechanism do you use to track defects in your personal projects? Do you have a specific system, or a process for prioritizing and managing them?

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• Is it OK to use dynamic typing to reduce the amount of variables in scope?

  - by missingno

  Often, when I am initializing something I have to use a temporary variable, for example: file_str = "path/to/file" file_file = open(file) or regexp_parts = ['foo', 'bar'] regexp = new RegExp( regexp_parts.join('|') ) However, I like to reduce the scope my variables to the smallest scope possible so there is less places where they can be (mis-)used. For example, I try to use for(var i ...) in C++ so the loop variable is confined to the loop body. In these initialization cases, if I am using a dynamic language, I am then often tempted to reuse the same variable in order to prevent the initial (and now useless) value from being used latter in the function. file = "path/to/file" file = open(file) regexp = ['...', '...'] regexp = new RegExp( regexp.join('|') ) The idea is that by reducing the number of variables in scope I reduce the chances to misuse them. However this sometimes makes the variable names look a little weird, as in the first example, where "file" refers to a "filename". I think perhaps this would be a non issue if I could use non-nested scopes begin scope1 filename = ... begin scope2 file = open(filename) end scope1 //use file here //can't use filename on accident end scope2 but I can't think of any programming language that supports this. What rules of thumb should I use in this situation? When is it best to reuse the variable? When is it best to create an extra variable? What other ways do we solve this scope problem?

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• Single Responsibility Principle Implementation

  - by Mike S

  In my spare time, I've been designing a CMS in order to learn more about actual software design and architecture, etc. Going through the SOLID principles, I already notice that ideas like "MVC", "DRY", and "KISS", pretty much fall right into place. That said, I'm still having problems deciding if one of two implementations is the best choice when it comes to the Single Responsibility Principle. Implementation #1: class User getName getPassword getEmail // etc... class UserManager create read update delete class Session start stop class Login main class Logout main class Register main The idea behind this implementation is that all user-based actions are separated out into different classes (creating a possible case of the aptly-named Ravioli Code), but following the SRP to a "tee", almost literally. But then I thought that it was a bit much, and came up with this next implementation class UserView extends View getLogin //Returns the html for the login screen getShortLogin //Returns the html for an inline login bar getLogout //Returns the html for a logout button getRegister //Returns the html for a register page // etc... as needed class UserModel extends DataModel implements IDataModel // Implements no new methods yet, outside of the interface methods // Haven't figured out anything special to go here at the moment // All CRUD operations are handled by DataModel // through methods implemented by the interface class UserControl extends Control implements IControl login logout register startSession stopSession class User extends DataObject getName getPassword getEmail // etc... This is obviously still very organized, and still very "single responsibility". The User class is a data object that I can manipulate data on and then pass to the UserModel to save it to the database. All the user data rendering (what the user will see) is handled by UserView and it's methods, and all the user actions are in one space in UserControl (plus some automated stuff required by the CMS to keep a user logged in or to ensure that they stay out.) I personally can't think of anything wrong with this implementation either. In my personal feelings I feel that both are effectively correct, but I can't decide which one would be easier to maintain and extend as life goes on (despite leaning towards Implementation #1.) So what about you guys? What are your opinions on this? Which one is better? What basics (or otherwise, nuances) of that principle have I missed in either design?

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• Where can I find design exercises to work on?

  - by Oak

  I feel it's important to continue practicing my problem-solving skills. Writing my own mini-projects is one way, but another is to try and solve problems posted online. It's easy to find interesting programming quizzes online that require applying clever algorithms to solve - Project Euler is one well-known example. However, in a lot of real-life projects the design of the software - especially in the initial phases - has a large impact and at later stages it cannot be tweaked as easily as plain algorithms. In order to improve these skills, I'm looking for any collection of design problems. When I say "design", I mean the abstract design of a software solution - for example what modules will there be and what are the dependencies between them, how data will flow in the program, what sort of data needs to be saved in the database, etc. Design problems are those problems that are critical to solve in the early stages of any project, but their solution is a whiteboard diagram without a single line of code. Of course these sort of problems do not have a single correct solution, but I'll be especially happy with any place that also displays pros and cons of the typical solutions that might be used to approach the problem.

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• Relationship DAO, Servlet, JSP and POJO

  - by John Hendrik

  I want to implement a JSP, POJO, DAO and Servlet in my J2EE program. However, I don't fully understand how the relationship between these elements should be. Is the following (MVC) setup the right way to do it? Main class creates servlet(controller) Servlet has a DAO defined in its class DAO has a POJO defined in its class Servlet communicates with the view (JSP page) Please give your feedback.

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