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  • HashMap "WriteOnce" Implementation .. need help

    - by JavaNewbie
    import java.util.*; public class HashMapExample { public static class WriteOnceMap<K, V> extends HashMap<K, V> { public V put(K key, V value) { /* WriteOnceMap is a map that does not allow changing value for a particular key. It means that put() method should throw IllegalArgumentException if the key is already assosiated with some value in the map. Please implement this method to conform to the above description of WriteOnceMap. */ } public void putAll(Map<? extends K, ? extends V> m) { /* Pleaase implement this method to conform to the description of WriteOnceMap above. It should either (1) copy all of the mappings from the specified map to this map or (2) throw IllegalArgumentException and leave this map intact if the parameter already contains some keys from this map. */ } } }

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  • perforce implementation of clearcase like "views"

    - by Pradyot
    I have read through the documentation on perforce and the "branching strategy" advice as well. One thing thats left me baffled, is how a simple concern is does not seem to adequtely adressed. When I am working on a project that touches many parts of our code base , I cannot checkin my code at the end of the day without checking into the trunk. So do I need to branch in this situation? I want to be able to have the ability to have a history of my changes in a long and hard project, so I can go back when I I make a wrong turn.. The problem with branching I see is that I will be creating copies of almost the entire codebase .. Am I missing an obvious solution here? thanks

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  • Abstract Design Pattern implementation

    - by Pathachiever11
    I started learning design patterns a while ago (only covered facade and abstract so far, but am enjoying it). I'm looking to apply the Abstract pattern to a problem I have. The problem is: Supporting various Database systems using one abstract class and a set of methods and properties, which then the underlying concrete classes (inheriting from abstract class) would be implementing. I have created a DatabaseWrapper abstract class and have create SqlClientData and MSAccessData concrete class that inherit from the DatabaseWrapper. However, I'm still a bit confused about how the pattern goes as far as implementing these classes on the Client. Would I do the following?: DatabaseWrapper sqlClient = new SqlClientData(connectionString); This is what I saw in an example, but that is not what I'm looking for because I want to encapsulate the concrete classes; I only want the Client to use the abstract class. This is so I can support for more database systems in the future with minimal changes to the Client, and creating a new concrete class for the implementations. I'm still learning, so there might be a lot of things wrong here. Please tell me how I can encapsulate all the concrete classes, and if there is anything wrong with my approach. Many Thanks! PS: I'm very excited to get into software architecture, but still am a beginner, so take it easy on me. :)

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  • What hash/map based programming language exist?

    - by Davorak
    Much like lisp is often considered a list based programming language what languages are considered map based? I remember reading about one a few years back, but can not longer find a reference to it. It looked something like: [if:test then:<code> else:<more code>] edit: and more where quoted code blocks which would be conditional evaluated. In this fashion if/cond and others would not be special form as they are in lisp/scheme.

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  • Is the below thread pool implementation correct(C#3.0)

    - by Newbie
    Hi Experts, For the first time ever I have implemented thread pooling and I found it to be working. But I am not very sure about the way I have done is the appropriate way it is supposed to be. Would you people mind in spending some valuable time to check and let me know if my approach is correct or not? If you people find that the approach is incorrect , could you please help me out in writing the correct version. I have basicaly read How to use thread pool and based on what ever I have understood I have developed the below program as per my need public class Calculation { #region Private variable declaration ManualResetEvent[] factorManualResetEvent = null; #endregion public void Compute() { factorManualResetEvent = new ManualResetEvent[2]; for (int i = 0; i < 2; i++){ factorManualResetEvent[i] = new ManualResetEvent(false); ThreadPool.QueueUserWorkItem(ThreadPoolCallback, i);} //Wait for all the threads to complete WaitHandle.WaitAll(factorManualResetEvent); //Proceed with the next task(s) NEXT_TASK_TO_BE_EXECUTED(); } #region Private Methods // Wrapper method for use with thread pool. public void ThreadPoolCallback(Object threadContext) { int threadIndex = (int)threadContext; Method1(); Method2(); factorManualResetEvent[threadIndex].Set(); } private void Method1 () { //Code of method 1} private void Method2 () { //Code of method 2 } #endregion }

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  • priority queue implementation

    - by davit-datuashvili
    i have implemented priority queue and i am interested if it is correct public class priqueue { private int n,maxsize; int x[]; void swap(int i,int j){ int t=x[i]; x[i]=x[j]; x[j]=t; } public priqueue(int m){ maxsize=m; x=new int [maxsize+1]; n=0; } void insert(int t){ int i,p; x[++n]=t; for (i=n;i>1 && x[p=i/2] >x[i];i=p) swap(p,i); } public int extramin(){ int i,c; int t=x[1]; x[1]=x[n--]; for (i=1;(c=2*i)<=n;i=c){ if (c+1<=n && x[c+1]<x[c]) c++; if (x[i]<=x[c]) break; swap(c,i); } return t; } public void display(){ for (int j=0;j<x.length;j++){ System.out.println(x[j]); } } } public class priorityqueue { public static void main(String[] args) { priqueue pr=new priqueue(12); pr.insert(20); pr.insert(12); pr.insert(22); pr.insert(15); pr.insert(35); pr.insert(17); pr.insert(40); pr.insert(51); pr.insert(26); pr.insert(19); pr.insert(29); pr.insert(23); pr.extramin(); pr.display(); } } //result: 0 12 15 17 20 19 22 40 51 26 35 29 23

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  • Force the use of interface instead of concrete implementation in declaration (.NET)

    - by gammelgul
    In C++, you can do the following: class base_class { public: virtual void do_something() = 0; }; class derived_class : public base_class { private: virtual void do_something() { std::cout << "do_something() called"; } }; The derived_class overrides the method do_something() and makes it private. The effect is, that the only way to call this method is like this: base_class *object = new derived_class(); object->do_something(); If you declare the object as of type derived_class, you can't call the method because it's private: derived_class *object = new derived_class(); object->do_something(); // --> error C2248: '::derived_class::do_something' : cannot access private member declared in class '::derived_class' I think this is quite nice, because if you create an abstract class that is used as an interface, you can make sure that nobody accidentally declares a field as the concrete type, but always uses the interface class. Since in C# / .NET in general, you aren't allowed to narrow the access from public to private when overriding a method, is there a way to achieve a similar effect here?

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  • Efficient implementation of exclusive execution

    - by n0weak
    I have an ObjectManager class that is used to process payments. It is wrapped over the Order entities, so new instance has to be created when processing is required. I need to prevent the situation when several ObjectManager instances are dealing with the same order simultaneously (it happend once because of some errors on the remote payment processing center, somehow they called our callback urls twice). I'd love to get an advice how to implement it more efficiently. For now, I am thinking about something like that: public class OrderManager{ private static final CopyOnWriteArrayList<Integer> LOCKER = new CopyOnWriteArrayList<Integer>(); private static synchronized boolean tryLock(Integer key) { return LOCKER.addIfAbsent(key); } private static void releaseLock(Integer key) { LOCKER.remove(key); } public void processPayment(Integer orderId) throws Exception{ if (!tryLock(orderId)) { return; } try { //operate } finally { releaseLock(orderId); } } //remainder omitted }

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  • Problem in thread pool implementation(C#3.0)

    - by Newbie
    Hi Experts, I have done the below thread pool program but the problem is that the WaitCallBackMethod(here ThreadPoolCallback) is getting called 2 times(which ideally should be called 1ce). what is the misktake I am making? public class Calculation { #region Private variable declaration ManualResetEvent[] factorManualResetEvent = null; #endregion public void Compute() { factorManualResetEvent = new ManualResetEvent[2]; for (int i = 0; i < 2; i++){ factorManualResetEvent[i] = new ManualResetEvent(false); ThreadPool.QueueUserWorkItem(ThreadPoolCallback, i);} //Wait for all the threads to complete WaitHandle.WaitAll(factorManualResetEvent); //Proceed with the next task(s) NEXT_TASK_TO_BE_EXECUTED(); } #region Private Methods // Wrapper method for use with thread pool. public void ThreadPoolCallback(Object threadContext) { int threadIndex = (int)threadContext; Method1(); Method2(); factorManualResetEvent[threadIndex].Set(); } private void Method1 () { //Code of method 1} private void Method2 () { //Code of method 2 } #endregion } I am using C#3.0 Thanks

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  • managed object subclasses are not generating implementation files and are incorrectly named

    - by mkc842
    In Xcode 4.6, I generated plenty of managed object subclass files without any problem. But now that I'm trying to do it in Xcode 5, it generates only a .h file. The header file has the correct properties, but it takes the name of my project, rather than the name of the core data entity I selected. Just to be sure I hadn't forgotten something, I carefully followed these steps . What could be going on? Thanks

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  • How to change the language of driver interface for Canon Pixma printers?

    - by Sammy
    Is there a way to change the language of the driver interface for Canon Pixma printers? Which language is used seems to be determined by the language of the OS or the Windows localization settings. I really don't want that, I want to be able to set the language manually to my own liking, either during the driver installation or afterwards. I have found a workaround for Pixma IP2770 where you edit the setup.ini file by replacing the language names and the DLL search paths with <SELECT> under the LANGUAGES section. So instead of... 0000=<SELECT> 0001=Arabic,RES\STRING\IJInstAR.ini,RES\DLL\IJInstAR.dll 0804=Simplified Chinese,RES\STRING\IJInstCN.ini,RES\DLL\IJInstCN.dll 0404=Traditional Chinese,RES\STRING\IJInstTW.ini,RES\DLL\IJInstTW.dll 0005=Czech,RES\STRING\IJInstCZ.ini,RES\DLL\IJInstCZ.dll 0006=Danish,RES\STRING\IJInstDK.ini,RES\DLL\IJInstDK.dll 0007=German,RES\STRING\IJInstDE.ini,RES\DLL\IJInstDE.dll 0008=Greek,RES\STRING\IJInstGR.ini,RES\DLL\IJInstGR.dll 0009=English,RES\STRING\IJInstUS.ini,RES\DLL\IJInstUS.dll 000A=Spanish,RES\STRING\IJInstES.ini,RES\DLL\IJInstES.dll 000B=Finnish,RES\STRING\IJInstFI.ini,RES\DLL\IJInstFI.dll 000C=French,RES\STRING\IJInstFR.ini,RES\DLL\IJInstFR.dll 000E=Hungarian,RES\STRING\IJInstHU.ini,RES\DLL\IJInstHU.dll 0010=Italian,RES\STRING\IJInstIT.ini,RES\DLL\IJInstIT.dll 0011=Japanese,RES\STRING\IJInstJP.ini,RES\DLL\IJInstJP.dll 0012=Korean,RES\STRING\IJInstKR.ini,RES\DLL\IJInstKR.dll 0013=Dutch,RES\STRING\IJInstNL.ini,RES\DLL\IJInstNL.dll 0014=Norwegian,RES\STRING\IJInstNO.ini,RES\DLL\IJInstNO.dll 0015=Polish,RES\STRING\IJInstPL.ini,RES\DLL\IJInstPL.dll 0016=Portuguese,RES\STRING\IJInstPT.ini,RES\DLL\IJInstPT.dll 0019=Russian,RES\STRING\IJInstRU.ini,RES\DLL\IJInstRU.dll 001D=Swedish,RES\STRING\IJInstSE.ini,RES\DLL\IJInstSE.dll 001E=Thai,RES\STRING\IJInstTH.ini,RES\DLL\IJInstTH.dll 001F=Turkish,RES\STRING\IJInstTR.ini,RES\DLL\IJInstTR.dll 0021=Indonesian,RES\STRING\IJInstID.ini,RES\DLL\IJInstID.dll You get.... 0000=<SELECT> 0001=<SELECT> 0804=<SELECT> 0404=<SELECT> 0005=<SELECT> 0006=<SELECT> 0007=<SELECT> 0008=<SELECT> 0009=English,RES\STRING\IJInstUS.ini,RES\DLL\IJInstUS.dll 000A=<SELECT> 000B=<SELECT> 000C=<SELECT> 000E=<SELECT> 0010=<SELECT> 0011=<SELECT> 0012=<SELECT> 0013=<SELECT> 0014=<SELECT> 0015=<SELECT> 0016=<SELECT> 0019=<SELECT> 001D=<SELECT> 001E=<SELECT> 001F=<SELECT> 0021=<SELECT> .... in case English is the preferred language. It's a way to force the installation program to only install the English language support. IP2770 is a model for the Asian market, so if you want to check this out you need to go to the Canon India download page (for instance) to get the driver. Unfortunately this method is not possible with my IP4000. There is no driver even available for it to download for Windows Vista. But is there really no way of changing the language of the UI in any normal way, you know... without having to hack it? Besides, the driver for my printer comes with Windows Vista, so I don't even have to install any drivers. And little do I get the chance to set the language, knowing that the installation never happens. Any ideas?...

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  • Why IDE has to be made in the language they are designed for?

    - by Em Ae
    Look at IntellijIDEA IDE, its a pretty sick ide but its made in Java and we all know that Java suck at GUI. Same goes for Eclipse. Though its way better and adopted SWT but it could have been best if it was developed in C/C++. We have really good systems now and thats why we don't feel that these IDES are nothing much but a memory hog. Why the IDE's have to be written in the language they are designed for ? Okay i know that IDE is a cool way to show how strong a language can be but even then someitmes, that specific language might not be best for a particular tastk.

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  • Is sticking to one language on a particular project a good practice?

    - by Ans
    I'm developing a pipeline for processing text that will go into production. The question I keep asking myself is: should I stick to one language for the project when I'm looking for a tool to do a particular task (e.g. NLTK, PDFMiner, CLD, CRFsuite, etc.)? Or is it OK to mix and match languages on the project? So I pick the best tool regardless of what language it's written in (e.g. OpenNLP, ParsCit, poppler, CFR++, etc.) and warp (wrap) my code around it? Note, I am not asking about should a developer stick to just one language for their career.

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  • Have you ever used a non mainstream language in a project? Why?

    - by EpsilonVector
    I was thinking about my academic experience with Smalltalk (well, Squeak) a while ago and whether I would like to use it for something, and it got me thinking: sure, it's as good and capable as any popular language, and it has some nice ideas, but there are certain languages that are already well entrenched in certain niches of programming (C is for systems programming, Java is for portability, and so on...), and Smalltalk and co. don't seem to have any obvious differentiating features to make them the right choice under certain circumstances, or at least not as far as I can tell, and when you add to it the fact that it's harder to find programmers who know it it adds all sorts of other problems for the organization itself. So if you ever worked on a project where a non-mainstream language (like Smalltalk) was used over a more mainstream one, what was the reason for it? To clarify: I'd like to focus this on imperative languages, since other paradigms like functional and logic programming language, while not necessarily mainstream, can still be good choices for certain projects for obvious reasons.

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  • How much time takes to a new language like D to become popular? [closed]

    - by Adrián Pérez
    I was reading about new languages for me to learn and I find very good comments about D, like it's the new C or what C++ should have been. Knowing that many people say wonders about the language, I'm wondering how much time usually takes to a language to become popular. This is, having libraries ported or written natively for this language and being used in serious software development. I have read about the history of Java, and Python to figure it out, but may be they are too high level complexity to say their development could take the same time as will take for D.

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  • Keep a programming language backwards compatible vs. fixing its flaws

    - by Radu Murzea
    First, some context (stuff that most of you know anyway): Every popular programming language has a clear evolution, most of the time marked by its version: you have Java 5, 6, 7 etc., PHP 5.1, 5.2, 5.3 etc. Releasing a new version makes new APIs available, fixes bugs, adds new features, new frameworks etc. So all in all: it's good. But what about the language's (or platform's) problems? If and when there's something wrong in a language, developers either avoid it (if they can) or they learn to live with it. Now, the developers of those languages get a lot of feedback from the programmers that use them. So it kind of makes sense that, as time (and version numbers) goes by, the problems in those languages will slowly but surely go away. Well, not really. Why? Backwards compatibility, that's why. But why is this so? Read below for a more concrete situation. The best way I can explain my question is to use PHP as an example: PHP is loved thousands of people and hated by just as many thousands. All languages have flaws, but apparently PHP is special. Check out this blog post. It has a very long list of so called flaws in PHP. Now, I'm not a PHP developer (not yet), but I read through all of it and I'm sure that a big chunk of that list are indeed real issues. (Not all of it, since it's potentially subjective). Now, if I was one of the guys who actively develops PHP, I would surely want to fix those problems, one by one. However, if I do that, then code that relies on a particular behaviour of the language will break if it runs on the new version. Summing it up in 2 words: backwards compatibility. What I don't understand is: why should I keep PHP backwards compatible? If I release PHP version 8 with all those problems fixed, can't I just put a big warning on it saying: "Don't run old code on this version !"? There is a thing called deprecation. We had it for years and it works. In the context of PHP: look at how these days people actively discourage the use of the mysql_* functions (and instead recommend mysqli_* and PDO). Deprecation works. We can use it. We should use it. If it works for functions, why shouldn't it work for entire languages? Let's say I (the developer of PHP) do this: Launch a new version of PHP (let's say 8) with all of those flaws fixed New projects will start using that version, since it's much better, clearer, more secure etc. However, in order not to abandon older versions of PHP, I keep releasing updates to it, fixing security issues, bugs etc. This makes sense for reasons that I'm not listing here. It's common practice: look for example at how Oracle kept updating version 5.1.x of MySQL, even though it mostly focused on version 5.5.x. After about 3 or 4 years, I stop updating old versions of PHP and leave them to die. This is fine, since in those 3 or 4 years, most projects will have switched to PHP 8 anyway. My question is: Do all these steps make sense? Would it be so hard to do? If it can be done, then why isn't it done? Yes, the downside is that you break backwards compatibility. But isn't that a price worth paying ? As an upside, in 3 or 4 years you'll have a language that has 90 % of its problems fixed.... a language much more pleasant to work with. Its name will ensure its popularity. EDIT: OK, so I didn't expressed myself correctly when I said that in 3 or 4 years people will move to the hypothetical PHP 8. What I meant was: in 3 or 4 years, people will use PHP 8 if they start a new project.

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  • How do I pick up a new language quickly, given I know several others?

    - by Mark Trapp
    One type of question that keeps coming up on Programmers.SE is how to learn a specific language, given you know several others (usually through a lot of experience or education). In some cases, however, one might need to get up to speed quickly for a job, or for personal development, or even to check out a hot new platform. In your experience, what general strategies have you used to pick up a new language quickly? Are there specific aspects of a language you try to focus on when starting cold? What types of resources do you find helpful in this process?

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  • How important is using the same language for client and server?

    - by Makita
    I have been evaluating architecture solutions for a mobile project that will have a web-service/app in addition to native apps and have been looking at various libraries, frameworks, and stacks like Meteor, this being a sort of "open stack package framework", is tightly bound with Node.js. There is a lot of talk about the benefits of using the same language both client and server side, and I'm not getting it. I could understand if you want to mirror the entire state of a web application on both client and server but struggling to find other wins... Workflow efficiency? I'm trying to understand why client/server language parity is considered to be a holy grail. Why does client/server language parity matter in software development?

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