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  • Java Static Methods

    - by KP65
    Hello, I am wondering when to use static methods? Say If i have a class with a few getters and setters, a method or two, and i want those methods only to be invokable on an instance object of the class. Does this mean i should use a static method? e.g Obj x = new Obj(); x.someMethod or Obj.someMethod (is this the static way?) I'm rather confused!

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  • C# 4.0: casting dynamic to static

    - by Kevin Won
    This is an offshoot question that's related to another I asked here. I'm splitting it off because it's really a sub-question: I'm having difficulties casting an object of type dynamic to another (known) static type. I have an ironPython script that is doing this: import clr clr.AddReference("System") from System import * def GetBclUri(): return Uri("http://google.com") note that it's simply newing up a BCL System.Uri type and returning it. So I know the static type of the returned object. now over in C# land, I'm newing up the script hosting stuff and calling this getter to return the Uri object: dynamic uri = scriptEngine.GetBclUri(); System.Uri u = uri as System.Uri; // casts the dynamic to static fine Works no problem. I now can use the strongly typed Uri object as if it was originally instantiated statically. however.... Now I want to define my own C# class that will be newed up in dynamic-land just like I did with the Uri. My simple C# class: namespace Entity { public class TestPy // stupid simple test class of my own { public string DoSomething(string something) { return something; } } } Now in Python, new up an object of this type and return it: sys.path.append(r'C:..path here...') clr.AddReferenceToFile("entity.dll") import Entity.TestPy def GetTest(): return Entity.TestPy(); // the C# class then in C# call the getter: dynamic test = scriptEngine.GetTest(); Entity.TestPy t = test as Entity.TestPy; // t==null!!! here, the cast does not work. Note that the 'test' object (dynamic) is valid--I can call the DoSomething()--it just won't cast to the known static type string s = test.DoSomething("asdf"); // dynamic object works fine so I'm perplexed. the BCL type System.Uri will cast from a dynamic type to the correct static one, but my own type won't. There's obviously something I'm not getting about this...

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  • Why aren't static const floats allowed?

    - by Jon Cage
    I have a class which is essentially just holds a bunch of constant definitions used through my application. For some reason though, longs compile but floats do not: class MY_CONSTS { public : static const long LONG_CONST = 1; // Compiles static const float FLOAT_CONST = 0.001f; // C2864 }; Gives the following error: 1>c:\projects\myproject\Constant_definitions.h(71) : error C2864: 'MY_CONSTS::FLOAT_CONST' : only static const integral data members can be initialized within a class Am I missing something?

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  • Calling method on category included from iPhone static library causes NSInvalidArgumentException

    - by Corey Floyd
    I have created a static library to house some of my code like categories. I have a category for UIViews in "UIView-Extensions.h" named Extensions. In this category I have a method called: - (void)fadeOutWithDelay:(CGFloat)delay duration:(CGFloat)duration; Calling this method works fine on the simulator on Debug configuration. However, if try to run the app on the device I get a NSInvalidArgumentException: [UIView fadeOutWithDelay:duration:]: unrecognized selector sent to instance 0x1912b0 *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[UIView fadeOutWithDelay:duration:]: unrecognized selector sent to instance 0x1912b0 It seems for some reason UIView-Extensions.h is not being included in the device builds. What I have checked/tried I did try to include another category for NSString, and had the same issue. Other files, like whole classes and functions work fine. It is an issue that only happens with categories. I did a clean all targets, which did not fix the problem. I checked the static library project, the categories are included in the target's "copy headers" and "compile sources" groups. The static library is included in the main projects "link binary with library" group. Another project I have added the static library to works just fine. I deleted and re-added the static library with no luck -ObjC linker flag is set Any ideas? nm output libFJSCodeDebug.a(UIView-Extensions.o): 000004d4 t -[UIView(Extensions) changeColor:withDelay:duration:] 00000000 t -[UIView(Extensions) fadeInWithDelay:duration:] 000000dc t -[UIView(Extensions) fadeOutWithDelay:duration:] 00000abc t -[UIView(Extensions) firstResponder] 000006b0 t -[UIView(Extensions) hasSubviewOfClass:] 00000870 t -[UIView(Extensions) hasSubviewOfClass:thatContainsPoint:] 000005cc t -[UIView(Extensions) rotate:] 000002d8 t -[UIView(Extensions) shrinkToSize:withDelay:duration:] 000001b8 t -[UIView(Extensions) translateToFrame:delay:duration:] U _CGAffineTransformRotate 000004a8 t _CGPointMake U _CGRectContainsPoint U _NSLog U _OBJC_CLASS_$_UIColor U _OBJC_CLASS_$_UIView U ___CFConstantStringClassReference U ___addsf3vfp U ___divdf3vfp U ___divsf3vfp U ___extendsfdf2vfp U ___muldf3vfp U ___truncdfsf2vfp U _objc_enumerationMutation U _objc_msgSend U _objc_msgSend_stret U dyld_stub_binding_helper

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  • Issue with deserialization of a static property in .Net

    - by Punit Singhi
    I have a class called Test which has four public properties and one of them is static. the problem is after deserialization the static property contains null value. i have debugged the code and found that at server side it contains the value which is a collection , but at client side it becomes null after deserialization. i know static members doesn't serialize and deserialize so obviously it should contain the value.

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  • NullPointerException with static variables

    - by tomekK
    I just hit very strange (to me) behaviour of java. I have following classes: public abstract class Unit { public static final Unit KM = KMUnit.INSTANCE; public static final Unit METERS = MeterUnit.INSTANCE; protected Unit() { } public abstract double getValueInUnit(double value, Unit unit); protected abstract double getValueInMeters(double value); } And: public class KMUnit extends Unit { public static final Unit INSTANCE = new KMUnit(); private KMUnit() { } //here are abstract methods overriden } public class MeterUnit extends Unit { public static final Unit INSTANCE = new MeterUnit(); private MeterUnit() { } ///abstract methods overriden } And my test case: public class TestMetricUnits extends TestCase { @Test public void testConversion() { System.out.println("Unit.METERS: " + Unit.METERS); System.out.println("Unit.KM: " + Unit.KM); double meters = Unit.KM.getValueInUnit(102.11, Unit.METERS); assertEquals(0.10211, meters, 0.00001); } } 1) MKUnit and MeterUnit are both singletons initialized statically, so during class loading. Constructors are private, so they can't be initialized anywhere else. 2) Unit class contains static final references to MKUnit.INSTANCE and MeterUnit.INSTANCE I would expect that: KMUnit class is loaded and instance is created. MeterUnit class is loaded and instance is created. Unit class is loaded and both KM and METERS variable are initialized, they are final so they cant be changed. But when I run my test case in console with maven my result is: T E S T S Running de.audi.echargingstations.tests.TestMetricUnits Unit.METERS: m Unit.KM: null Tests run: 3, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.089 sec <<< FAILURE! - in de.audi.echargingstations.tests.TestMetricUnits testConversion(de.audi.echargingstations.tests.TestMetricUnits) Time elapsed: 0.011 sec <<< ERROR! java.lang.NullPointerException: null at de.audi.echargingstations.tests.TestMetricUnits.testConversion(TestMetricUnits.java:29) Results : Tests in error: TestMetricUnits.testConversion:29 NullPointer And the funny part is that, when I run this test from eclipse via JUnit runner everything is fine, I have no NullPointerException and in console I have: Unit.METERS: m Unit.KM: km So the question is: what can be the reason that KM variable in Unit is null (and in the same time METERS is not null)

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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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  • 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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  • Using nested classes for constants?

    - by antirysm
    What's wrong with using nested classes to group constants? Like so: public static class Constants { public static class CategoryA { public const string ValueX = "CatA_X"; public const string ValueY = "CatA_Y"; } public static class CategoryB { public const string ValueX = "CatB_X"; public const string ValueY = "CatB_Y"; } } Used like so: Console.WriteLine(Constants.CategoryA.ValueY); Console.WriteLine(Constants.CategoryB.ValueX); You could also make the "Constants"-class partial...

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  • Reflection: get Static method from the parent class.

    - by jitm
    Hello, I have task to get static method using reflection like this : myType.GetMethod("MyMethod",BindingFlags.Static | BindingFlags.Public | BindingFlags.InvokeMethod); In case if class contains MyMethod all works correctly, but in case if parent class contains MyMethod I receive null :(. How can I call static method from the parent using reflection like code that I describe above? Thanks.

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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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  • 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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  • PHP5: restrict access to function to certain classes

    - by Tim
    Is there a way in PHP5 to only allow a certain class or set of classes to call a particular function? For example, let's say I have three classes ("Foo", "Bar", and "Baz"), all with similarly-named methods, and I want Bar to be able to call Foo::foo() but deny Baz the ability to make that call: class Foo { static function foo() { print "foo"; } } class Bar { static function bar() { Foo::foo(); print "bar"; } // Should work } class Baz { static function baz() { Foo::foo; print "baz"; } // Should fail } Foo::foo(); // Should also fail There's not necessarily inheritance between Foo, Bar, and Baz, so the use of protected or similar modifiers won't help; however, the methods aren't necessarily static (I made them so here for the simplicity of the example).

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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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  • 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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