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  • Should I create protected constructor for my singleton classes?

    - by Vijay Shanker
    By design, in Singleton pattern the constructor should be marked private and provide a creational method retuning the private static member of the same type instance. I have created my singleton classes like this only. public class SingletonPattern {// singleton class private static SingletonPattern pattern = new SingletonPattern(); private SingletonPattern() { } public static SingletonPattern getInstance() { return pattern; } } Now, I have got to extend a singleton class to add new behaviors. But the private constructor is not letting be define the child class. I was thinking to change the default constructor to protected constructor for the singleton base class. What can be problems, if I define my constructors to be protected? Looking for expert views....

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  • Throwing cats out of windows

    - by AndrewF
    Imagine you're in a tall building with a cat. The cat can survive a fall out of a low story window, but will die if thrown from a high floor. How can you figure out the longest drop that the cat can survive, using the least number of attempts? Obviously, if you only have one cat, then you can only search linearly. First throw the cat from the first floor. If it survives, throw it from the second. Eventually, after being thrown from floor f, the cat will die. You then know that floor f-1 was the maximal safe floor. But what if you have more than one cat? You can now try some sort of logarithmic search. Let's say that the build has 100 floors and you have two identical cats. If you throw the first cat out of the 50th floor and it dies, then you only have to search 50 floors linearly. You can do even better if you choose a lower floor for your first attempt. Let's say that you choose to tackle the problem 20 floors at a time and that the first fatal floor is #50. In that case, your first cat will survive flights from floors 20 and 40 before dying from floor 60. You just have to check floors 41 through 49 individually. That's a total of 12 attempts, which is much better than the 50 you would need had you attempted to use binary elimination. In general, what's the best strategy and it's worst-case complexity for an n-storied building with 2 cats? What about for n floors and m cats? Assume that all cats are equivalent: they will all survive or die from a fall from a given window. Also, every attempt is independent: if a cat survives a fall, it is completely unharmed. This isn't homework, although I may have solved it for school assignment once. It's just a whimsical problem that popped into my head today and I don't remember the solution. Bonus points if anyone knows the name of this problem or of the solution algorithm.

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  • How could it happen that version control software emerged so lately?

    - by sharptooth
    According to Wikipedia (the table at the page bottom), the earliest known version control systems were CVS and TeamWare both known from year 1990. How can it be? Software development has been here from at most 1960's and I honestly can't imagine working with codebase without version control. How could it happen that version control software emerged so lately compared to software development?

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  • Do you use ASCII art to decorate your code?

    - by CiNN
    Do you use ASCII art to decorate your code? .-"""-. ' \ |,. ,-. | |()L( ()| | license goes here |,' `".| | |.___.',| ` .j `--"' ` `. / ' ' \ / / ` `. / / ` . / / l | . , | | ,"`. .| | _.' ``. o | `..-'l | `.`, | `. | `. __.j ) |__ |--""___| ,-' `"--...,+"""" `._,.-' mh www /n n\ /\ |/^\| / \ warning notes | , | ^||^ \_/ || _U_ || /` `''-----'P3 / |. .|''-----"|| \'| | || \| | || E | || /#####\ || /#####\ || ||| || ||| || ||| || ||| gem || molom Ll /~~~\/~~\/~~~\/~~~\/~~\/~~~\ /~~~\/~~\/~~~\/~~~\/~~\/~~~\ | /\/ /\/ /\ || /\/ /\/ /\ | | /\ \/\ \/\ || /\ \/\ \/\ | \ \/ /\/ /\/ /\ \/ /\/ /\/ / function name \ \/\ \/\ \/ /\ \/\ \/\ \/ / \ \/\ \/\ \/ \ \/\ \/\ \/ \/ /\/ /\/ / \/ /\/ /\/ / ,_/\ \/\ \/\ \__/\ \/\ \/\ \______________________/ /\/ /\/ /\__/ /\/ /\/ /\_, (__/\__/\__/\____/\__/\__/\________________________/\__/\__/\____/\__/\__/\__)

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  • To what extent should code try to explain fatal exceptions?

    - by Andrzej Doyle
    I suspect that all non-trivial software is likely to experience situations where it hits an external problem it cannot work around and thus needs to fail. This might be due to bad configuration, an external server being down, disk full, etc. In these situations, especially if the software is running in non-interactive mode, I expect that all one can really do is log an error and wait for the admin to read the logs and fix the problem. If someone happens to interact with the software in the meantime, e.g. a request comes in to a server that failed to initialize properly, then perhaps an appropriate hint can be given to check the logs and maybe even the error can be echoed (depending on whether you can tell if they're a technical guy as opposed to a business user). For the moment though let's not think too hard about this part. My question is, to what extent should the software be responsible for trying to explain the meaning of the fatal error? In general, how much competence/knowledge are you allowed to presume on administrators of the software, and how much should you include troubleshooting information and potential resolution steps when logging fatal errors? Of course if there's something that's unique to the runtime context this should definitely be logged; but lets assume your software needs to talk to Active Directory via LDAP and gets back an error "[LDAP: error code 49 - 80090308: LdapErr: DSID-0C090334, comment: AcceptSecurityContext error, data 525, vece]". Is it reasonable to assume that the maintainers will be able to Google the error code and work out what it means, or should the software try to parse the error code and log that this is caused by an incorrect user DN in the LDAP config? I don't know if there is a definitive best-practices answer for this, so I'm keen to hear a variety of views.

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  • Is there any self-improving compiler around?

    - by JohnIdol
    I am not aware of any self-improving compiler, but then again I am not much of a compiler-guy. Is there ANY self-improving compiler out there? Please note that I am talking about a compiler that improves itself - not a compiler that improves the code it compiles. Any pointers appreciated! Side-note: in case you're wondering why I am asking have a look at this post. Even if I agree with most of the arguments I am not too sure about the following: We have programs that can improve their code without human input now — they’re called compilers. ... hence my question.

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  • Bi-directional communication with 1 socket - how to deal with collisions?

    - by Zwei Steinen
    Hi, I have one app. that consists of "Manager" and "Worker". Currently, the worker always initiates the connection, says something to the manager, and the manager will send the response. Since there is a LOT of communication between the Manager and the Worker, I'm considering to have a socket open between the two and do the communication. I'm also hoping to initiate the interaction from both sides - enabling the manager to say something to the worker whenever it wants. However, I'm a little confused as to how to deal with "collisions". Say, the manager decides to say something to the worker, and at the same time the worker decides to say something to the manager. What will happen? How should such situation be handled? P.S. I plan to use Netty for the actual implementation. Thank you very much in advance!

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  • Common Programming Jargon

    - by jdk
    What programming terms have you coined (or heard) that have taken off in your own circles (i.e. have heard others repeat it)? It might be within your own team, workplace or garnered greater popularity on the Internet. Write your programming term, word or phrase in bold text followed by an explanation, citation and/or usage example so we can use it in appropriate context. Please no repeats of common jargon already ingrained in the programming culture like: "kludge", "automagically", "cruft", etc. (unless you coined it). Stealing from the comments: "A shared vocabulary is the basis of communication, not just among programmers [...]"

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  • What turns away users/prospective users?

    - by Zach Johnson
    In your experience, what kinds of things have turned away users and prospective users from using your programs? Also, what kinds of things turn you away from using someone else's programs? For example, one thing that really bugs me is when someone provides free software, but requires you to enter your name and email address before you download it. Why do they need my name and email address? I just want to use the program! I understand that the developer(s) may want to get a feel for how many users they have, etc, but the extra work I have to do really makes me think twice about downloading their software, even if it does really great things.

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  • In what situations is octal base used?

    - by Bob
    I've seen binary and hex used quite often but never octal. Yet octal has it's own convention for being used in some languages (ie, a leading 0 indicating octal base). When is octal used? What are some typical situations when one would use octal or octal would be easier to reason about? Or is it merely a matter of taste?

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  • How do game companies handle programming for multiple platforms?

    - by stormist
    You often see that a new game will be released on Xbox 360, PS3 and Windows PC. How do gaming companies do this? Is it a common source code compiled using different compilers? Are actual different source codes required? example news article announcing this: http://www.gameranx.com/updates/id/502/article/dungeon-siege-3-announced-to-be-developed-by-obsidian/

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  • View artifacts leaking into the model of MVC

    - by Jono
    In an ASP.NET MVC application (which has very little chance of having its view technology ported to something non-HTML, but whose functional requirements evolve weekly,) how much HTML should ideally be allowed to be directly represented in the Model? I might come across as a design bigot for this, but I regard it as bad practice to allow any view constructs to "leak" into the model in an MVC application (and vice versa). For example, a Model that represents an item you're about to purchase should know nothing about the HTML check box that says "add giftwrap/message", nor should it know about any HTML drop down lists for payment card types. Conversely the View shouldn't be doing work like figuring out button text by translating keys into values (by looking in resource files.)

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  • What is recursion? -- In plain english.

    - by Christopher Altman
    I hear this word everyday, but cannot give a meaningful, concise, or plain-english answer to what it is. Recursion is defined by the bastian of knowledge as: Recursion in computer science is a method where the solution to a problem depends on solutions to smaller instances of the same problem.1 The approach can be applied to many types of problems, and is one of the central ideas of computer science.[2] Source Is recursion simply something that repeats itself to get a solution? I am looking for a "Recursion for Dummies" definition, and maybe simple examples. My goal is to be able to understand and explain recursion in my own words. I do not like simply thinking I know the meaning of something because I hear it referenced daily, but have not paused to form my own understanding.

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  • Any ideas for developing a Risc Processor friendly string allocator?

    - by Richard Fabian
    I'm working on some tools to enable high throughput data-oriented development, and one thing that I've not got an immediate answer for is how you go about allocating strings quickly. On risc processors you've got another problem of implementation that the CPU doesn't like branching, which is what I'm trying to minimise or avoid. Also, cache coherence is important on most CPUs, so that's gotta be influential in the design too. So, how would you go about reducing the overhead for a generic string allocator? Sometimes it's easier to solve a more explicit problem, so any ideas for string sizes of 5-30?

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  • Code Golf: Print the entire "12 Days of Christmas" song in the fewest lines of code.

    - by fizzer
    Print all 12 verses of the popular holiday song. By 12 verses I mean the repetition of each line as is sung in the song, ie Verse One: On the first day of Christmas my true love gave to me a partridge in a pear tree. Verse Two On the second day of Christmas my true love gave to me two turtle doves and a partridge in a pear tree. ... Verse N: On the nth day of Christmas my true love gave to me (Verse N-1 without the first line) (line added in verse N)

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  • Is there such a thing as too many tables?

    - by Stacey
    I've been searching stackoverflow for about an hour now and couldn't find any topics related, so I apologize if this is a duplicate question. My inquery is this. Is there a point at which there are too many tables in a database? Even if the structure is well organized, thought out, and perfectly facilitates the design intent? I have a database that is quickly approaching 40 tables - about 10 main ones, and over 30 ancillary tables (junction tables, 'enumeration' tables, etc). Am I just a bad developer - or should I be trying something different? It seems like so many to me, I'm really afraid at how it will impact the performance of the project. I have done a lot of condensing where possible, grouped similar things where possible, etc. The database is built in MS-SQL 2008.

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  • OOP App Architecture: Which layer does a lazy loader sit in?

    - by JW
    I am planning the implemention an Inheritance Mapper pattern for an application component http://martinfowler.com/eaaCatalog/inheritanceMappers.html One feature it needs to have is for a domain object to reference a large list of aggreageted items (10,000 other domain objects) So I need some kind of lazy loading collection to be passed out of the aggregate root domain object to other domain objects. To keep my (php) model scripts organised i am storing them in two folders: MyComponent\ controllers\ models\ domain\ <- domain objects, DDD repository, DDD factory daccess\ <- PoEAA data mappers, SQL queries etc views\ But now I am racking my brains wondering where my lazy loading collection sits. Any suggestions / justifications for putting it in one place over another another? DDD = Domain Driven Design Patterns, Eric Evans - book PoEAA = Patterns of Application Architecture Patterns, Martin Fowler - book

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  • Why are compilers so stupid?

    - by martinus
    I always wonder why compilers can't figure out simple things that are obvious to the human eye. They do lots of simple optimizations, but never something even a little bit complex. For example, this code takes about 6 seconds on my computer to print the value zero (using java 1.6): int x = 0; for (int i = 0; i < 100 * 1000 * 1000 * 1000; ++i) { x += x + x + x + x + x; } System.out.println(x); It is totally obvious that x is never changed so no matter how often you add 0 to itself it stays zero. So the compiler could in theory replace this with System.out.println(0). Or even better, this takes 23 seconds: public int slow() { String s = "x"; for (int i = 0; i < 100000; ++i) { s += "x"; } return 10; } First the compiler could notice that I am actually creating a string s of 100000 "x" so it could automatically use s StringBuilder instead, or even better directly replace it with the resulting string as it is always the same. Second, It does not recognize that I do not actually use the string at all, so the whole loop could be discarded! Why, after so much manpower is going into fast compilers, are they still so relatively dumb? EDIT: Of course these are stupid examples that should never be used anywhere. But whenever I have to rewrite a beautiful and very readable code into something unreadable so that the compiler is happy and produces fast code, I wonder why compilers or some other automated tool can't do this work for me.

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  • Why does C++ mandate that complex only be instantiated for float, double, or long double?

    - by templatetypedef
    According to the C++ ISO spec, §26.2/2: The effect of instantiating the template complex for any type other than float, double or long double is unspecified. Why would the standard authors explicitly add this restriction? This makes it unspecified, for example, what happens if you make complex<int> or a complex<MyCustomFixedPointType> and seems like an artificial restriction. Is there a reason for this limitation? Is there a workaround if you want to instantiate complex with your own custom type? I'm primarily asking this question because of this earlier question, in which the OP was confused as to why abs was giving bizarre outputs for complex<int>. That said, this still doesn't quite make sense given that we also might want to make complex numbers out of fixed-points types, higher-precision real numbers, etc. Thanks!

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  • Getting specific values with regex [JAVA, ANDROID]

    - by David
    I need to knowingly isolate each row of the vcard and get its value. For instance, I want to get "5555" from X-CUSTOMFIELD. So far, my thoughts are: "X-CUSTOMFIELD;\d+" I have been looking at some tutorials and I am a little confused with what function to use? What would my regex above return? Would it give me the whole line or just the numerical part (5555)? I was thinking I i get the whole row, I can use substring to get the digits? BEGIN:VCARD VERSION:2.1 N:Last;First; FN:First Last TEL;HOME;VOICE:111111 TEL;MOBILE;VOICE:222222 X-CUSTOMFIELD;5555 END:VCARD

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