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  • Creating instance in java class

    - by aladine
    Please advise me the difference between two ways of declaration of java constructor public class A{ private static A instance = new A(); public static A getInstance() { return instance; } public static void main(String[] args) { A a= A.getInstance(); } } AND public class B{ public B(){}; public static void main(String[] args) { B b= new B(); } } Thanks

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  • Inlining an array of non-default constructible objects in a C++ class

    - by porgarmingduod
    C++ doesn't allow a class containing an array of items that are not default constructible: class Gordian { public: int member; Gordian(int must_have_variable) : member(must_have_variable) {} }; class Knot { Gordian* pointer_array[8]; // Sure, this works. Gordian inlined_array[8]; // Won't compile. Can't be initialized. }; As even beginner C++ users know, the language guarantees that all members are initialized when constructing a class. And it doesn't trust the user to initialize everything in the constructor - one has to provide valid arguments to the constructors of all members before the body of the constructor even starts. Generally, that's a great idea as far as I'm concerned, but I've come across a situation where it would be a lot easier if I could actually have an array of non-default constructible objects. The obvious solution: Have an array of pointers to the objects. This is not optimal in my case, as I am using shared memory. It would force me to do extra allocation from an already contended resource (that is, the shared memory). The entire reason I want to have the array inlined in the object is to reduce the number of allocations. This is a situation where I would be willing to use a hack, even an ugly one, provided it works. One possible hack I am thinking about would be: class Knot { public: struct dummy { char padding[sizeof(Gordian)]; }; dummy inlined_array[8]; Gordian* get(int index) { return reinterpret_cast<Gordian*>(&inlined_array[index]); } Knot() { for (int x = 0; x != 8; x++) { new (get(x)) Gordian(x*x); } } }; Sure, it compiles, but I'm not exactly an experienced C++ programmer. That is, I couldn't possibly trust my hacks less. So, the questions: 1) Does the hack I came up with seem workable? What are the issues? (I'm mainly concerned with C++0x on newer versions of GCC). 2) Is there a better way to inline an array of non-default constructible objects in a class?

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  • call_user_function_array() and __construct

    - by John
    I'm working on a simple framework, and I'm having a slight problem. I'd like to use call_user_function_array() to pass parameters to a function. That's fine, except the function I want to pass it to is __construct. I can't create an instance of an object with cufa(), and by instantiating an object, and then using cufa to call that instance's __construct(), I run into problems with a broken class because I'm calling the constructor twice (and one time it's called wrong.)

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  • CodeContracts: How to fullfill Require in Ctor using this() call?

    - by mafutrct
    I'm playing around with Microsoft's CodeContracts and encountered a problem I was unable to solve. I've got a class with two constructors: public Foo (public float f) { Contracts.Require(f > 0); } public Foo (int i) : this ((float)i) {} The example is simplified. I don't know how to check the second constructor's f for being 0. Is this even possible with Contracts?

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  • C# Strange Behavior

    - by Betamoo
    I have a custom struct : struct A { public int y; } a custom class with empty constuctor: class B { public A a; public B() { } } and here is the main: static void Main(string[] args) { B b = new B(); b.a.y = 5;//No runtime errors! Console.WriteLine(b.a.y); } When I run the above program, it does not give me any errors, although I did not initialize struct A in class B constructor..'a=new A();'

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  • How to define an aspectj pointcut that picks out all constructors of a class that has a specific annotation?

    - by PineForest
    Here is the annotation: @Target(value = ElementType.TYPE) @Retention(value = RetentionPolicy.RUNTIME) @Inherited public @interface MyAnnotation { String name(); } Here is one annotated class: @MyAnnotation(name="foo") public class ClassA { public ClassA() { // Do something } } Here is a second annotated class: @MyAnnotation(name="bar") public class ClassB { public ClassB(String aString) { // Do something } } I am looking for an aspectj pointcut that correctly matches the constructors for ClassA and ClassB while not matching any other constructor for any other class NOT annotated by MyAnnotation.

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  • purpose of php consutructor

    - by Bharanikumar
    Hi , Am working in the classes and object class structure , but not extream level , Just class and function , then in one place instantiation . that's it , not much big functions like __construct etc , Please tell me very simply , 1.what is th purpose of constructor ad destructor , But i know theoretical explanation school level , But i am expecting something like in real time , which situation we have to use, and is there any example for that please tell me, Regards

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  • What's the proper term for a function inverse to a constructor - to unwrap a value from a data type?

    - by Petr Pudlák
    Edit: I'm rephrasing the question a bit. Apparently I caused some confusion because I didn't realize that the term destructor is used in OOP for something quite different - it's a function invoked when an object is being destroyed. In functional programming we (try to) avoid mutable state so there is no such equivalent to it. (I added the proper tag to the question.) Instead, I've seen that the record field for unwrapping a value (especially for single-valued data types such as newtypes) is sometimes called destructor or perhaps deconstructor. For example, let's have (in Haskell): newtype Wrap = Wrap { unwrap :: Int } Here Wrap is the constructor and unwrap is what? The questions are: How do we call unwrap in functional programming? Deconstructor? Destructor? Or by some other term? And to clarify, is this/other terminology applicable to other functional languages, or is it used just in the Haskell? Perhaps also, is there any terminology for this in general, in non-functional languages? I've seen both terms, for example: ... Most often, one supplies smart constructors and destructors for these to ease working with them. ... at Haskell wiki, or ... The general theme here is to fuse constructor - deconstructor pairs like ... at Haskell wikibook (here it's probably meant in a bit more general sense), or newtype DList a = DL { unDL :: [a] -> [a] } The unDL function is our deconstructor, which removes the DL constructor. ... in The Real World Haskell.

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  • Portable USB drives hidden pertition - New request

    - by ZXC
    This question was made by Francesco on Jul 29 '11 at 17:14. and the replies were not satisfactory due they not point to an important problem that´s: Why could anyone want to make certain data only accesible for a program but not to the users?. For example: If I want to do a safe distribution of original music for demostration purposes I will need several requisites: 1) The music should be heard using a simple procedure like selecting the name of each song on a playlist of a mediaplayer. 2) The portable media, ussually a portable USB drive, must hide for complete and should make unaccesible the files that contain the audio data to anything but the mediaplayer, that must be in the first partition, the one that is visible. 3) Considering that´s impossible to really hide files in a non-hidden partition, a second hidden partition should be created in the USB drive and the audio data will be stored there. 4) The trick is to read the audio data files stored in the hidden partition with a mediaplayer stored in the visible partition, the media player also should be a complete standalone program and independent from any library of the operating system except of the OS audio system. 5) The hidden partition should have a copy protection scheme that could impede to do copies of the data or create working ISO images of it. I know that this description could not be technically accurate but it has a complete logic from the needs of a music producer against the problem of piracy. The philosophy that surrounds the concept is to transform a virtual object like a digital string of audio in a solid object like the analog vinyl discs are.

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  • Synchronizing files between Linux servers, through FTP

    - by Daniel Magliola
    I have the following configuration of servers: 1 central linux server, a VPS 8 satellite linux servers, "crappy shared hostings" I have a bunch of files that I need to have in all servers. Right now i'm copying them everywhere manually, but I want to be able to copy them to the central server, and then have a scheduled process that runs every now and then and synchronizes them (only outwardly, no need to try to find "new" files in the satellite servers). There are a couple of catches though: I can't have any custom software in the satellite servers, or do strange command line things that'll auto connect to them and send the files directly. I know this is the way these kinds of things are normally done, but the satellite servers are crappy shared hosting ones where I have absolutely no control over anything. I need to send the files over FTP I also need to have, in my central server, a list of the files that are available in each of the satellite servers, to make sure they are ready before I send traffic to them. If I were to do this manually, the steps would be: get the list of files in a satellite server compare to my own, and send the files that are missing get the list of files again, and store it in my central database. I'd like to know what tools are out there that can alleviate as much of this as possible, first the syncing, and then the "getting the list of files available in the other server". I'm going to be doing everything from PHP, not sure if there are good tools to "use FTP from PHP", which i'm pretty sure i'll have to do for step 3 at least. Thanks in advance for any ideas! Daniel

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  • Paste textbox from Powerpoint to Word as an editable control

    - by George Harris
    I have a Powerpoint 2007 file that contains a number of textboxes and shapes with text on them. I can edit, resize, change the text, etc. in these boxes in Powerpoint. However, if I select an item, copy it, and paste it into a Word 2007 document, I can't edit it. I can resize the entire thing, but it acts more like an image than a text box. I've tried the paste special options and keep source formatting options, but still can't edit it. Is there a way to be able to paste the editable content from Powerpoint and still have it editable in Word? Update I found this question that appears to get to the root of the problem: The MS Office Art graphics engine (aka Escher 2) is new to MS Office 2007 and while fully implemented in Excel and Powerpoint is only partially implemented in Word 2007 for backwards compatibility with the MS Office Drawing/Graphics engine (aka Escher) still available in Word It should work in earlier versions of Word and Word 2010, but not Word 2007. This is quite frustrating as I have to edit the slide in Powerpoint before copying it into Word. While doable, it adds another step, but the problem is that everyone who wants to update the Word document will have to do the same thing, adding complexity and steps for everyone. If I embed the Powerpoint slide in the document, I can edit the controls, but they don't scale the same way and takes a lot of work.

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  • Visual Studio build fails: unable to copy exe-file from obj\debug to bin\debug

    - by Nailuj
    This is a question asked before, both here on Stack Overflow and other places, but none of the suggestions I've found this far has helped me, so I just have to try asking a new question. Scenario: I have a simple Windows Forms application (C#, .NET 4.0, Visual Studio 2010). It has a couple of base forms that most other forms inherit from, it uses Entity Framework (and POCO classes) for database access. Nothing fancy, no multi-threading or anything. Problem: All was fine for a while. Then, all out of the blue, Visual Studio failed to build when I was about to launch the application. I got the warning "Unable to delete file '...bin\Debug\[ProjectName].exe'. Access to the path '...bin\Debug\[ProjectName].exe' is denied." and the error "Unable to copy file 'obj\x86\Debug\[ProjectName].exe' to 'bin\Debug\[ProjectName].exe'. The process cannot access the file 'bin\Debug\[ProjectName].exe' because it is being used by another process." (I get both the warning and the error when running Rebuild, but only the error when running Build - don't think that is relevant?) I understand perfectly fine what the warning and error message says: Visual Studio is obviously trying to overwrite the exe-file while it the same time has a lock on it for some reason. However, this doesn't help me find a solution to the problem... The only thing I've found working is to shut down Visual Studio and start it again. Building and launching then works, untill I make a change in some of the forms, then I have the same problem again and have to restart... Quite frustrating! As I mentioned above, this seems to be a known problem, so there are lots of suggested solutions. I'll just list what I've already tried here, so people know what to skip: Creating a new clean solution and just copy the files from the old solution. Adding the following to the following to the project's pre-build event: if exist "$(TargetPath).locked" del "$(TargetPath).locked"   if not exist "$(TargetPath).locked" if exist "$(TargetPath)" move "$(TargetPath)" "$(TargetPath).locked" Adding the following to the project properties (.csproj file): <GenerateResourceNeverLockTypeAssembliestrue</GenerateResourceNeverLockTypeAssemblies However, none of them worked for me, so you can probably see why I'm starting to get a bit frustrated. I don't know where else to look, so I hope somebody has something to give me! Is this a bug in VS, and if so is there a patch? Or has I done something wrong, do I have a circular reference or similar, and if so how could I find out? Any suggestions are highly appreciated :)

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  • Dependency Injection Constructor Madness

    - by JP
    I find that my constructors are starting to look like this: public MyClass(Container con, SomeClass1 obj1, SomeClass2, obj2.... ) with ever increasing parameter list. Since "Container" is my dependency injection container, why can't I just do this: public MyClass(Container con) for every class? What are the downsides? If I do this, it feels like I'm using a glorified static. Please share your thoughts on IoC and Dependency Injection madness. Thanks in advance. -JP

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  • XmlSerializer giving FileNotFoundException at constructor

    - by Irwin
    An application I've been working with is failing when i try to serialize types. A statement like this: XmlSerialzer lizer = new XmlSerializer(typeof(MyType)); Produces: System.IO.FileNotFoundException occurred Message="Could not load file or assembly '[Containing Assembly of MyType].XmlSerializers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified." Source="mscorlib" FileName="[Containing Assembly of MyType].XmlSerializers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" FusionLog="" StackTrace: at System.Reflection.Assembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection) at System.Reflection.Assembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection) I don't define any special serializers for my class.

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  • Using reflection to retrieve constructor used to instantiate attribute

    - by summatix
    How can I retrieve information about how an attribute was instantiated? Consider I have the following class definitions: [AttributeUsage(AttributeTargets.Class)] public class ExampleAttribute : Attribute { public ExampleAttribute(string value) { Value = value; } public string Value { get; private set; } } [ExampleAttribute("test")] public class Test { } The new .NET 4.0 MemberInfo.GetCustomAttributesData method: foreach (var attribute in typeof(Test).GetCustomAttributesData()) { Console.WriteLine(attribute); } outputs [Example.ExampleAttribute("test")]. Is there another way to retrieve this same information, preferably using the MemberInfo.GetCustomAttributes method?

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  • java IO to copy one File to another

    - by Aly
    I have two Java.io.File objects file1 and file2. I want to copy the contents from file1 to file2. Is there an standard way to do this without me having to create a method that reads file1 and write to file2

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  • How to get identities of inserted data records using SQL bulk copy

    - by Olga
    Hello I have a ADO.NET dataTable with about 100.000 records. In this table there is a column "xyID" which has no values in it, because they are generated by insertion into my MSSQL Database. Now i have the problem, that i need this IDs for other processes. I am looking for a way to bulk copy this dataTable into the MSSQL database, and within the same "step" to "fill" my dataTable with the generated IDs. Thank you for your answers!

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  • WPF MVVM ViewModel constructor designmode

    - by Snake
    Right, I've got a main wpf window: <Window x:Class="NorthwindInterface.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:ViewModels="clr-namespace:NorthwindInterface.ViewModels" Title="MainWindow" Height="350" Width="525"> <Window.DataContext> <ViewModels:MainViewModel /> </Window.DataContext> <ListView ItemsSource="{Binding Path=Customers}"> </ListView> </Window> And the MainViewModel is this: class MainViewModel : INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged = delegate { }; public MainViewModel() { Console.WriteLine("test"); using (NorthwindEntities northwindEntities = new NorthwindEntities()) { this.Customers = (from c in northwindEntities.Customers select c).ToList(); } } public List<Customer> Customers { get;private set; } Now the problem is that in designermode I can't see my MainViewModel, it highlights it saying that it can't create an instance of the MainViewModel. It is connecting to a database. That is why (when I comment the code the problem is solved). But I don't want that. Any solutions on best practices around this?

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  • Ambiguous function/constructor call in C#

    - by Ahmed Said
    The following code causes a compiler error, as it is ambiguous call but the problem if we use object instead of ArrayList no error happens and the string version works fine; Do you have an explanation for that? class A { public A(string x) { Console.WriteLine("string"); } public A(ArrayList x) { Console.WriteLine("ArrayList"); } } static void Main(string[] args) { A o = new A(null); }

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  • Unable to copy a file from obj\Debug to bin\Debug

    - by M.H
    I have a project in C# and I get this error every time I try to compile the project : (Unable to copy file "obj\Debug\Project1.exe" to "bin\Debug\Project1.exe". The process cannot access the file 'bin\Debug\Project1.exe' because it is being used by another process.), so I have to close the process from the task manager. my project is only one form and there is no multithreading. what is the solution (without restarting VS or Killing the process)?

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