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  • Initialize a static member ( an array) in C++

    - by Jimmy zhang
    I intended to create a class which only have static members and static functions. One of the member variable is an array. Would it be possible to initialize it without using constructors? I am having lots of linking errors right now... Class A{ public: static char a[128]; static void do_something(); } How would you initialize a[128]? Why can't I initialize a[128] by directly specifying its value like in C? a[128={1,2,3,...};

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  • Using static mutex in a class

    - by Dmitry Yudakov
    I have a class that I can have many instances of. Inside it creates and initializes some members from a 3rd party library (that use some global variables) and is not thread-safe. I thought about using static boost::mutex, that would be locked in my class constructor and destructor. Thus creating and destroying instances among my threads would be safe for the 3rd party members. class MyClass { static boost::mutex mx; // 3rd party library members public: MyClass(); ~MyClass(); }; MyClass::MyClass() { boost::mutex::scoped_lock scoped_lock(mx); // create and init 3rd party library stuff } MyClass::~MyClass() { boost::mutex::scoped_lock scoped_lock(mx); // destroy 3rd party library stuff } I cannot link because I receive error: undefined reference to `MyClass::mx` Do I need some special initialization of such static member? Is the whole conception of static mutex wrong?

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  • when does static member gets memory.

    - by vaibhav
    I have a class which have a static member. As I understand all static members are common for all instance of the class. So it means static members would get memory only once. Where is this memory is allocated (Stack or Heap) and when this memory get allocated.

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  • Where do I put javaassist code?

    - by DutrowLLC
    I have an application running on google app engine. I'm using restlets and I have a couple of layers set up including the restlet layer, the model layer, the business layer, and the data layer. I'm attempting to use javaassist to modify some classes, but I'm unsure where to actually put the code. I tried to put the code in the static initialization block: public class Person { String firstName; String getFirstName(){return null;} static{ ClassPool pool = ClassPool.getDefault(); try { CtClass CtPerson = pool.get("Person"); CtMethod CtGetFirstName = CtPerson.getDeclaredMethod("GetFirstName"); CtGetFirstName.setBody("return firstName;"); CtPerson.toClass(); } catch (Exception e) { e.printStackTrace(); } } } ...but that resulted in this error: javassist.CannotCompileException:.....attempted duplicate class definition...". I guess it makes sense that I can't edit the class file in the middle of its generation. I know the code works because I was able to run it correctly by simply putting it in a location that would run when I sent the program a command. (accessed a Restlet resource). The code ran fine if an instance of the class had not already been instantiated, however once I instantiated an instance of the affected class, the javaassist code failed. I assume I need to put this code somewhere that it will only run either: once after the program starts, directly before a class is instantiated for the first time, or even better, during compile time.

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  • Alternatives to static methods on interfaces for enforcing consistency

    - by jayshao
    In Java, I'd like to be able to define marker interfaces, that forced implementations to provide static methods. For example, for simple text-serialization/deserialization I'd like to be able to define an interface that looked something like this: public interface TextTransformable<T>{ public static T fromText(String text); public String toText(); Since interfaces in Java can't contain static methods though (as noted in a number of other posts/threads: here, here, and here this code doesn't work. What I'm looking for however is some reasonable paradigm to express the same intent, namely symmetric methods, one of which is static, and enforced by the compiler. Right now the best we can come up with is some kind of static factory object or generic factory, neither of which is really satisfactory. Note: in our case our primary use-case is we have many, many "value-object" types - enums, or other objects that have a limited number of values, typically carry no state beyond their value, and which we parse/de-parse thousands of time a second, so actually do care about reusing instances (like Float, Integer, etc.) and its impact on memory consumption/g.c. Any thoughts?

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  • Using static variables in Android

    - by michael
    Hi, In android, are using static variables a recommended practice? E.g, implementing a Singleton pattern in Java, I usually do: private static A the_instance; public static A getInstance() { if (the_instance == null) { the_instance = new A(); } return the_instance; } Also, when does this get cleaned up by the Android JVM? Thank you.

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  • hadoop mapper static initialisation

    - by rakeshr
    Hi, I have a code fragment in which I am using a static code block to initialize a variable. public static class JoinMap extends Mapper<IntWritable, MbrWritable, LongWritable, IntWritable> { ....... public static RTree rt = null; static { String rtreeFileName = "R.rtree"; rt = new RTree(rtreeFileName); } public void map(IntWritable key, MbrWritable mbr,Context context) throws IOException, InterruptedException { ......... List elements = rt.overlaps(mbr.getRect()); ....... } } My problem is that the variable rt in the above code fragment is not getting initialised. Can anybody suggest a fix or an alternate way to initialise the variable. I don't want to initialise it inside my map function since that slows down the entire process.

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  • Large static arrays are slowing down class load, need a better/faster lookup method

    - by Visualize
    I have a class with a couple static arrays: an int[] with 17,720 elements a string[] with 17,720 elements I noticed when I first access this class it takes almost 2 seconds to initialize, which causes a pause in the GUI that's accessing it. Specifically, it's a lookup for Unicode character names. The first array is an index into the second array. static readonly int[] NAME_INDEX = { 0x0000, 0x0001, 0x0005, 0x002C, 0x003B, ... static readonly string[] NAMES = { "Exclamation Mark", "Digit Three", "Semicolon", "Question Mark", ... The following code is how the arrays are used (given a character code). [Note: This code isn't a performance problem] int nameIndex = Array.BinarySearch<int>(NAME_INDEX, code); if (nameIndex > 0) { return NAMES[nameIndex]; } I guess I'm looking at other options on how to structure the data so that 1) The class is quickly loaded, and 2) I can quickly get the "name" for a given character code. Should I not be storing all these thousands of elements in static arrays?

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  • GridView ObjectDataSource LINQ Paging and Sorting using multiple table query.

    - by user367426
    I am trying to create a pageing and sorting object data source that before execution returns all results, then sorts on these results before filtering and then using the take and skip methods with the aim of retrieving just a subset of results from the database (saving on database traffic). this is based on the following article: http://www.singingeels.com/Blogs/Nullable/2008/03/26/Dynamic_LINQ_OrderBy_using_String_Names.aspx Now I have managed to get this working even creating lambda expressions to reflect the sort expression returned from the grid even finding out the data type to sort for DateTime and Decimal. public static string GetReturnType<TInput>(string value) { var param = Expression.Parameter(typeof(TInput), "o"); Expression a = Expression.Property(param, "DisplayPriceType"); Expression b = Expression.Property(a, "Name"); Expression converted = Expression.Convert(Expression.Property(param, value), typeof(object)); Expression<Func<TInput, object>> mySortExpression = Expression.Lambda<Func<TInput, object>>(converted, param); UnaryExpression member = (UnaryExpression)mySortExpression.Body; return member.Operand.Type.FullName; } Now the problem I have is that many of the Queries return joined tables and I would like to sort on fields from the other tables. So when executing a query you can create a function that will assign the properties from other tables to properties created in the partial class. public static Account InitAccount(Account account) { account.CurrencyName = account.Currency.Name; account.PriceTypeName = account.DisplayPriceType.Name; return account; } So my question is, is there a way to assign the value from the joined table to the property of the current table partial class? i have tried using. from a in dc.Accounts where a.CompanyID == companyID && a.Archived == null select new { PriceTypeName = a.DisplayPriceType.Name}) but this seems to mess up my SortExpression. Any help on this would be much appreciated, I do understand that this is complex stuff.

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  • Apply [ThreadStatic] attribute to a method in external assembly

    - by Sen Jacob
    Can I use an external assembly's static method like [ThreadStatic] method? Here is my situation. The assembly class (which I do not have access to its source) has this structure public class RegistrationManager() { private RegistrationManager() {} public static void RegisterConfiguration(int ID) {} public static object DoWork() {} public static void UnregisterConfiguration(int ID) {} } Once registered, I cannot call the DoWork() with a different ID without unregistering the previously registered one. Actually I want to call the DoWork() method with different IDs simultaneously with multi-threading. If the RegisterConfiguration(int ID) method was [ThreadStatic], I could have call it in different threads without problems with calls, right? So, can I apply the [ThreadStatic] attribute to this method or is there any other way I can call the two static methods same time without waiting for other thread to unregister it? If I check it like the following, it should work. for(int i=0; i < 10; i++) { new Thread(new ThreadStart(() => Checker(i))).Start(); } public string Checker(int i) { public static void RegisterConfiguration(i); // Now i cannot register second time public static object DoWork(i); Thread.Sleep(5000); // DoWork() may take a little while to complete before unregistered public static void UnregisterConfiguration(i); }

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  • Extract object (*.o) files from an iPhone static library

    - by Brett
    I have a set of iPhone static libraries (a *.a file) in which I only call a few of the classes from. I have used AR in the past (with linux libraries) to extract the object files from the static library, remove the unwanted object files and rearchive. However, when I try this with an iPhone compliled static library, I get the following error: ar: CustomiPhoneLib.a is a fat file (use libtool(1) or lipo(1) and ar(1) on it) ar: CustomiPhoneLib.a: Inappropriate file type or format Does anyone know how to extract the object files from an iphone compiled static library? Doing thie could potentially reduce the final file size.

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  • interface variables are final and static by default and methods are public and abstract

    - by sap
    The question is why it's been decided to have variable as final and static and methods as public and abstract by default. Is there any particular reason for making them implicit,variable as final and static and methods as public and abstract. Why they are not allowing static method but allowing static variable? We have interface to have feature of multiple inheritance in Java and to avoid diamond problem. But how it solves diamond problem,since it does not allow static methods. In the following program, both interfaces have method with the same name..but while implementing only one we implement...is this how diamond problem is solved? interface testInt{ int m = 0; void testMethod(); } interface testInt1{ int m = 10; void testMethod(); } public class interfaceCheck implements testInt, testInt1{ public void testMethod(){ System . out . println ( "m is"+ testInt.m ); System . out . println ( "Hi World!" ); } }

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  • Combining several static archives into a new one

    - by knight666
    I'm making a game engine for mobile devices. I want to compile my code, link it against a few static libraries and then combine my compiled code with those static libraries to form a new static library. However, my Google Fu is abandoning me. Suppose I have static libraries a.a, b.a and c.a and my code. I want to compile all that into awesome.a. How can I do that? I'm using CodeSourcery's arm-none-linux-gnueabi-ar by the way. Thanks in advance.

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  • Javascript: Static member variable containing object instances

    - by tom
    I have the following: function Preferences() { } Preferences.players = { 'player1': new Player() } players is a static member variable of Preferences and I'm trying to make it an object containing an instance of a Player. However, it doesn't appear to let me do this. It seems like it will allow me to define players if I make it a non-static member variable however. Like so: function Preferences() { var players = { 'player1' : new Player() } } Is it possible to create a static member variable containing instances of an object in JS?

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  • Get the parent class of a null object (C# Reflection)

    - by Nick
    How would I get the parent class of an object that has a value of null? For example... 'Class A' contains 'int? i' which is not set to any value when the class is created. Then in some other place in the code I want to pass in 'i' as a parameter to some function. Using 'i' as the only info, I want to be able to figure out that 'Class A' "owns" 'i'. The reason for this is because 'Class A' also contains some other object, and I want to call this other object's value from that same function mentioned in the above paragraph. Could also be: public class A { public class B { public int? i; public int? j; } B classBInstance = new B(); public string s; } { ... A someClassAInstance = new A(); ... doSomething(someClassAInstance.classBInstance.i); ... } public static bool doSomething(object theObject) { string s = /* SOMETHING on theObject to get to "s" from Class A */; int someValue = (int)theObject; }

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  • C#: An object reference is required for the non-static field, method, or Property

    - by Omin
    I feel bad for asking this when there are so many questions that are related but I was not able to find/understand the answer I am looking for. // 2. Develop a program to convert currency X to currency Y and visa versa. using System; class Problem2 { static void Main (string[] args) { while (true) { Console.WriteLine ("1. Currency Conversion from CAD to Won"); Console.WriteLine ("2. Currency Conversion from Won to Cad"); Console.Write ("Choose from the Following: (1 or 2)? "); int option = int.Parse( Console.ReadLine() ); //double x; if (option == 1) { Console.WriteLine ("Type in the amount you would like to Convert CAD to Won: "); //double y =double.Parse( Console.ReadLine()); //Console.WriteLine( cadToWon( y ) ); Console.WriteLine( cadToWon( double.Parse( Console.ReadLine() ) )); } if (option == 2) { Console.WriteLine ("Type in the amount you would like to Convert Won to CAD: "); Console.WriteLine( wonToCad (double.Parse( Console.ReadLine()))); } } } double cadToWon( double x ) { return x * 1113.26; } double wonToCad( double x) { return x / 1113.26; } } This give me the Error messgae "An object reference is required for the non-static field, method, or property 'Problem2..." I know that I'll be able to run the program if I add static infront of the methods but I'm wondering why I need it (I think it's because Main is static?) and what do I need to change in order to use these methods without adding static to them? Thank you

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  • Why should Java ThreadLocal variables be static

    - by kellyfj
    I was reading that JavaDoc for Threadlocal here http://java.sun.com/j2se/1.5.0/docs/api/java/lang/ThreadLocal.html and it says "ThreadLocal instances are typically private static fields in classes that wish to associate state with a thread (e.g., a user ID or Transaction ID). " But my question is why did they choose to make it static (typically) - it makes it a bit confusing to have "per thread" state but its static?

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  • Using static variable in android

    - by michael
    Hi, In android, is it recommend to use static variable? E.g, implement a Singleton pattern in Java, I usually do: private static A the_instance; public static A getInstance() { if (the_instance == null) { the_instance = new A(); } return the_instance; } My question is when do that get free by android JVM? Thank you.

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  • Declare a Dictionary inside a static class

    - by Ngu Soon Hui
    How to declare a static dictionary object inside a static class? I tried public static class ErrorCode { public const IDictionary<string , string > ErrorCodeDic =new Dictionary<string, string>() { {"1","User name or password problem"} }; } But the compiler complains that "A const field of a reference type other than string can only be initialized with null".

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  • Static member variable containing object instances

    - by tom
    I have the following: function Preferences() { } Preferences.players = { 'player1': new Player() } players is a static member variable of Preferences and I'm trying to make it an object containing an instance of a Player. However, it doesn't appear to let me do this. It seems like it will allow me to define players if I make it a non-static member variable however. Like so: function Preferences() { var players = { 'player1' : new Player() } } Is it possible to create a static member variable containing instances of an object in JS?

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  • turning a project into a static library

    - by numerical25
    I checked out the microsoft documents. it shows how to create a static library upon creation of the project. but not necessarily on how to convert a previously made project, into a static library. So my question is, where do I go to turn my previously made project, into a static lib. so I can include it in my other projects

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  • Extension methods on a static object

    - by Max Malygin
    I know (or so I hear) that writing extension methods for a single stand alone .net class (not an implementation of IEnumerable) is potential code smell. However, for the sake of making the life easier I need to attach a method to the ConfigurationManager class in asp.net. It's a static object so this won't work: public static List<string> GetSupportedDomains(this ConfigurationManager manager) { //the manager needs to be static. } So the question is - is it possible to write an extension method for a static class in .net?

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