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  • Creation of Objects: Constructors or Static Factory Methods

    - by Rachel
    I am going through Effective Java and some of my things which I consider as standard are not suggested by the book, for instance creation of object, I was under the impression that constructors are the best way of doing it and books says we should make use of static factory methods, I am not able to few some advantages and so disadvantages and so am asking this question, here are the benefits of using it. Advantages: One advantage of static factory methods is that, unlike constructors, they have names. A second advantage of static factory methods is that, unlike constructors, they are not required to create a new object each time they’re invoked. A third advantage of static factory methods is that, unlike constructors, they can return an object of any subtype of their return type. A fourth advantage of static factory methods is that they reduce the verbosity of creating parameterized type instances. I am not able to understand this advantage and would appreciate if someone can explain this point Disadvantages: The main disadvantage of providing only static factory methods is that classes without public or protected constructors cannot be subclassed. A second disadvantage of static factory methods is that they are not readily distinguishable from other static methods.I am not getting this point and so would really appreciate some explanation. Reference: Effective Java, Joshua Bloch, Edition 2, pg: 5-10 Also, How to decide to use whether to go for Constructor or Static Factory Method for Object Creation ?

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  • How can a static class be resolved by the Unity Framework?

    - by user213988
    I wold like the unity framework to resolve a static class "MyStaticObject" specified in my config file. As my class is static, I am getting an error "The type StaticObject does not have an accessible constructor." My config file looks as below: <unity> <typeAliases> <typeAlias alias="singleton" type="Microsoft.Practices.Unity.ContainerControlledLifetimeManager, Microsoft.Practices.Unity" /> <typeAlias alias="StaticObject" type="MyStaticAssembly.MyStaticObject, MyStaticAssembly, Version=1.0.0.0" /> <typeAlias alias="staticobject" type="MyStaticAssembly.MyStaticObject, MyStaticAssembly" /> </typeAliases> <containers> <container> <types> <type type="StaticObject" mapTo="staticobject" name="My Static Object"> <lifetime type="singleton"/> </type> </types> </container> </containers> </unity> I would highly appreciate any help.

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  • Using static variables for Strings

    - by Vivart
    below content is taken from Best practice: Writing efficient code but i didn't understand why private static String x = "example"; faster than private static final String x ="example"; Can anybody explain this. Using static variables for Strings When you define static fields (also called class fields) of type String, you can increase application speed by using static variables (not final) instead of constants (final). The opposite is true for primitive data types, such as int. For example, you might create a String object as follows: private static final String x = "example"; For this static constant (denoted by the final keyword), each time that you use the constant, a temporary String instance is created. The compiler eliminates "x" and replaces it with the string "example" in the bytecode, so that the BlackBerry® Java® Virtual Machine performs a hash table lookup each time that you reference "x". In contrast, for a static variable (no final keyword), the String is created once. The BlackBerry JVM performs the hash table lookup only when it initializes "x", so access is faster. private static String x = "example"; You can use public constants (that is, final fields), but you must mark variables as private.

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  • javascript : make a new safe class constructor

    - by guilin ??
    sometimes we loss the new keyword when define new object, obj = new Clazz(); //correct obj = Clazz(); //wrong, but no syntax error, hard to debug. I want to write a function to help me create Class and make it new safe. var Class = function(constructor){ //when constructor // if not call by new return new constructor(); // else constructor(); } var MyClazz = Class(function(name){ this.name = name }, SuperClazz1, SuperClass2 ) MyClazz.extend({ show: function(){console.log(this.name)} }) obj1 = new MyClazz(); obj2 = MyClazz(); // obj1 should same as obj2 Is it possible, any exists module?

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  • Windows CE: Changing Static IP Address

    - by Bruce Eitman
    A customer contacted me recently and asked me how to change a static IP address at runtime.  Of course this is not something that I know how to do, but with a little bit of research I figure out how to do it. It turns out that the challenge is to request that the adapter update itself with the new IP Address.  Otherwise, the change in IP address is a matter of changing the address in the registry for the adapter.   The registry entry is something like: [HKEY_LOCAL_MACHINE\Comm\LAN90001\Parms\TcpIp]    "EnableDHCP"=dword:0    "IpAddress"="192.168.0.100"     "DefaultGateway"="192.168.0.1"    "Subnetmask"="255.255.255.0" Where LAN90001 would be replace with your adapter name.  I have written quite a few articles about how to modify the registry, including a registry editor that you could use. Requesting that the adapter update itself is a matter of getting a handle to the NDIS driver, and then asking it to refresh the adapter.  The code is: #include <windows.h> #include "winioctl.h" #include "ntddndis.h"   void RebindAdapter( TCHAR *adaptername ) {       HANDLE hNdis;       BOOL fResult = FALSE;       int count;         // Make this function easier to use - hide the need to have two null characters.       int length = wcslen(adaptername);       int AdapterSize = (length + 2) * sizeof( TCHAR );       TCHAR *Adapter = malloc(AdapterSize);       wcscpy( Adapter, adaptername );       Adapter[ length ] = '\0';       Adapter[ length +1 ] = '\0';           hNdis = CreateFile(DD_NDIS_DEVICE_NAME,                   GENERIC_READ | GENERIC_WRITE,                   FILE_SHARE_READ | FILE_SHARE_WRITE,                   NULL,                   OPEN_ALWAYS,                   0,                   NULL);         if (INVALID_HANDLE_VALUE != hNdis)       {             fResult = DeviceIoControl(hNdis,                         IOCTL_NDIS_REBIND_ADAPTER,                         Adapter,                         AdapterSize,                         NULL,                         0,                         &count,                         NULL);             if( !fResult )             {                   RETAILMSG( 1, (TEXT("DeviceIoControl failed %d\n"), GetLastError() ));             }             CloseHandle(hNdis);       }       else       {             RETAILMSG( 1, (TEXT("Failed to open NDIS Handle\n")));       }   }       int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR    lpCmdLine, int       nCmdShow) {     RebindAdapter( TEXT("LAN90001") );     return 0; }   If you don’t want to write any code, but instead plan to use a registry editor to change the IP Address, then there is a command line utility to do the same thing.  NDISConfig.exe can be used: Ndisconfig adapter rebind LAN90001    Copyright © 2012 – Bruce Eitman All Rights Reserved

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  • Inspection, code review - is it really testing?

    - by user970696
    ISTQB, Wikipedia or other sources classify verification acitivities (reviews etc.) as a static testing, yet other do not. If we can say that peer reviews and inspections are actually a kind of a testing, then a lot of standards do not make sense (consider e.g. ISO which say that validation is done by testing, while verification by checking of work products) - it should at least say dynamic testing for validation, shouldn't it? I am completing master thesis dealing with QA and I must admit that I have never seen worse and more ambiguous and contradicting literature than in this field :/ Do you think (and if so, why) that static testing is a good and justifiable term or should we stick to testing and static checks/analysis?

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  • Can I have conditional construction of classes when using IoC.Resolve ?

    - by Corpsekicker
    I have a service class which has overloaded constructors. One constructor has 5 parameters and the other has 4. Before I call, var service = IoC.Resolve<IService>(); I want to do a test and based on the result of this test, resolve service using a specific constructor. In other words, bool testPassed = CheckCertainConditions(); if (testPassed) { //Resolve service using 5 paramater constructor } else { //Resolve service using 4 parameter constructor //If I use 5 parameter constructor under these conditions I will have epic fail. } Is there a way I can specify which one I want to use?

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  • What is the possible benefit (if any) of allowing recursive contructors?

    - by Penang
    In Java, constructors cannot be recursive. Compile time error: "recursive constructor invocation". Let's assume that we did not have this restriction. Things to keep in mind: The return type of a constructor is void. Since it is a void method you can't harness the complete power of recursion. A constructor can invoke itself (or any other constructor) using this(). But a "call to this must be first statement in constructor" We could use non local data between consecutive calls to still have some possible gain from recursive constructors. Would there be any benefit from allowing recursive constructors?

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  • C++ Static Initializer - Is it thread safe

    - by Yan Cheng CHEOK
    Usually, when I try to initialize a static variable class Test2 { public: static vector<string> stringList; private: static bool __init; static bool init() { stringList.push_back("string1"); stringList.push_back("string2"); stringList.push_back("string3"); return true; } }; // Implement vector<string> Test2::stringList; bool Test2::__init = Test2::init(); Is the following code thread safe, during static variable initialization? Is there any better way to static initialize stringlist, instead of using a seperate static function (init)?

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  • Enabling OUD Entry Cache for large static groups

    - by Sylvain Duloutre
    Oracle Unified Directory can take advantage of several caches to improve performances. especially the so-called database cache and the file system cache. In addition to that, it is possible to use an entry cache to cache LDAP entries. By default, the entry cache is not used. In specific deployements involving large static groups, it may worth loading the group entries to the entry cache to speed up group membership and group-based aci evaluation. To do so, run the following commands: First, specify which entries should reside in the entry cache. In the commad below, only entries matching the LDAP filter " (|(objctclass=groupOfNames)(objectclass=groupOfUniqueNames)) " will be stored in the entry cache. dsconfig set-entry-cache-prop \          --cache-name FIFO \          --add include-filter:\(\|\(objctclass=groupOfNames\)\(objectclass=groupOfUniqueNames\)\)          --port <ADMIN_PORT> \          --bindDN cn=Directory\ Manager \          --bindPassword ****** \          --no-prompt Then enable the entry cache: dsconfig set-entry-cache-prop \          --cache-name FIFO \          --set enabled:true \          --port <ADMIN_PORT> \          --bindDN cn=Directory\ Manager \          --bindPassword ****** \          --no-prompt In addition to that, you can control how much memory the entry cache can use: oud@s96sec1d0-v3:/application/oud : dsconfig -X -n -p <ADMIN PORT> -D "cn=Directory Manager" -w <password> get-entry-cache-prop --cache-name FIFO Property           : Value(s) -------------------:----------------------------------------------------------- cache-level        : 1 enabled            : true exclude-filter     : - include-filter     : (|(objctclass=groupOfNames)(objectclass=groupOfUniqueNames)) max-entries        : 2147483647 max-memory-percent : 90 You can change the max-entries amd max-memory-percent properties to control the entry cache size using the dsconfig set-entry-cache-prop command.

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  • Facebook: Sending private messages to FB profile from a static website [migrated]

    - by Frondor
    I need to setup a static website for people to: Complete a form. And using anything from Facebook API, GET the form output via message to a Facebook Profile. I've been punching my head against "facebook developers" page all night long and can't find out how to do it. Seems quite easy, but the problem is that I don't know if you'll get my point :) Like the Send Dialog feature, you can set a certain user as recipient which will be displayed on the "To:" field once the dialog appears. FB.ui({ method: 'send', to: 'UserID', link: 'http://www.nytimes.com/2011/06/15/arts/people-argue-just-to-win-scholars-assert.html', }); Ok, All I need is to be able to use the same behavior but instead of setting a "to:" parameter, I'd like to set a "message:" parameter. I don't know how I can solve this becuase there's no parameter like this on the API actually. This is what I need to build (It's a prototype, this code won't work) <form action="mysite.com" id="order"> <input type="radio" name="chocolate" value="white">White <br/> <input type="radio" name="chocolate" value="black">Black <br/> <input type="submit" value="Order" /> </form> jQuery gets the values $(document).ready(function() { $("#order").on("submit", function(e) { e.preventDefault(); var formOutput = $(this).serialize(); var order = "I'd like to eat" + formOutput + "chocolate"; }); }); Facebook sdk sends this output ('order' string) FB.ui({ method: 'send', //or whatever to: 'UserID', message: order, //Its just an example, note the variable coming from the form link: 'http://www.nytimes.com/2011/06/15/arts/people-argue-just-to-win-scholars-assert.html', }); As we all know, what I wrote isn't possible, so I'm asking for any alternative solution if somebody can give me, I'm not very friendly with facebook APIs :) I though in another solution which consist in using the form output directly on the 'link:' parameter of FB.ui and then reading it with jQuery on some landing page. For example, on the message sent, the linked content redirects to this URL: http://mysite.com/dashboard.html?chocolate=white and the dashboard page source code: <script> var choco = getUrlParameter('chocolate'); $("#dashboard").text("This person wants" + choco + "chocolate") </script> <div id="dashboard"></div> And this way, I will be able to see which kind of chocolate the person selected by parsing some parameters on the URL when clicking on the link section of the message: using a code like this: FB.ui({ method: 'send', //or whatever to: 'MyUserID', link: 'http://mysite.com/dashboard.html?chocolate=white', }); But no this try, my biggest problem is that I don't know how to dynamically "customize" that "link:" paramenter with jQuery. I think the best solution is to use a code like this along with the dashboard page in order to "translate" the shared URLs and see what kind of chocolate people are demanding xD FB.ui({ //declaring a variable (example) var string = getFormData().serialize; var orderString = "mysite.com/dashboard.html?" + string; // end the variables // start facebook API code method: 'send', //or whatever to: 'MyUserID', link: orderString, }); I was working here until I gave up and started to post this http://jsfiddle.net/Frondor/sctepn06/2/ Thanks in advance, I'll love you for ever if you help me solving this :D

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  • Class constructor in java

    - 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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  • Why is it preferable to call a static method statically from within an instance of the method's clas

    - by javanix
    If I create an instance of a class in Java, why is it preferable to call a static method of that same class statically, rather than using this.method()? I get a warning from Eclipse when I try to call static method staticMethod() from within the custom class's constructor via this.staticMethod(). public MyClass() { this.staticMethod(); } vs public MyClass() { MyClass.staticMethod(); } Can anyone explain why this is a bad thing to do? It seems to me like the compiler should already have allocated an instance of the object, so statically allocating memory would be unneeded overhead.

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  • Finding out if an IP address is static or dynamic?

    - by Joshua
    I run a large bulletin board and I get spammers every now and again. My moderation team does a good job filtering them out but every time I IP ban them they seem to come back (I'm pretty sure it's the same person on some occasions, as the post patterns are exactly the same as are the usernames) but I'm afraid to ban them by IP address every time. If they are on a dynamic IP address, I could be banning innocent users later down the line when they try to get to my forum through SERPs, but if I ban only via static IPs I know that I'm only banning that one person. So, is there a way to properly determine if an IP address is static or dynamic? Thanks.

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  • Which format does static library (*.lib) files use? Where can I find "Official" specifications of *.

    - by claws
    Just now I found that static libraries in *nix systems, in other words *.a libraries are nothing but archives of relocatables(*.o files) in ar fromat. What about static libraries(*.lib files) in windows? Which format are they in? I found an article: http://www.microsoft.com/msj/0498/hood0498.aspx which explains *.lib file structure. But Where can I find "Official" specifications of *.lib file structure/format? Other than ar.exe of mingw is there any tool from Microsoft which extracts relocatable objects of *.lib & *.a files? EDIT: I wonder why I'm unable to get to this question. If there are no official specifications. Then how does the compiler ('linker' to be more correct) writers work with *.LIB files?

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  • What does static linking against a library actually do?

    - by Salgar
    Say I had a library called libfoo which contained a class, a few static variables, possibly something with 'C' linkage, and a few other functions. Now I have a main program which looks like this: int main() { return 5+5; } When I compile and link this, I link against libfoo. Will this have any effect? Will my executable increase in size? If so, why? Do the static variables or their addresses get copied into my executable? Apologies if there is a similar question to this or if I'm being particularly stupid in any way.

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  • Does a static object within a function introduce a potential race condition?

    - by Jeremy Friesner
    I'm curious about the following code: class MyClass { public: MyClass() : _myArray(new int[1024]) {} ~MyClass() {delete [] _myArray;} private: int * _myArray; }; // This function may be called by different threads in an unsynchronized manner void MyFunction() { static const MyClass _myClassObject; [...] } Is there a possible race condition in the above code? Specifically, is the compiler likely to generate code equivalent to the following, "behind the scenes"? void MyFunction() { static bool _myClassObjectInitialized = false; if (_myClassObjectInitialized == false) { _myClassObjectInitialized = true; _myClassObject.MyClass(); // call constructor to set up object } [...] } ... in which case, if two threads were to call MyFunction() nearly-simultaneously, then _myArray might get allocated twice, causing a memory leak? Or is this handled correctly somehow?

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  • how to raise warning if return value is disregarded - gcc or static code check?

    - by Drakosha
    I'd like to see all the places in my code (C++) which disregard return value of a function. How can I do it - with gcc or static code analysis tool? Bad code example: int f(int z) { return z + (z*2) + z/3 + z*z + 23; } int main() { int i = 7; f(i); ///// <<----- here I disregard the return value return 1; } Update: it should work even if the function and its use are in different files free static check tool

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  • Class decorator to declare static member (e.g., for log4net)?

    - by Ken
    I'm using log4net, and we have a lot of this in our code: public class Foo { private static readonly ILog log = LogManager.GetLogger(typeof(Foo)); .... } One downside is that it means we're pasting this 10-word section all over, and every now and then somebody forgets to change the class name. The log4net FAQ also mentions this alternative possibility, which is even more verbose: public class Foo { private static readonly ILog log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType); ... } Is it possible to write a decorator to define this? I'd really like to say simply: [LogMe] // or perhaps: [LogMe("log")] public class Foo { ... } I've done similar things in other languages, but never a statically-compiled language like C#. Can I define class members from a decorator?

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  • Are static members of a generic class tied to the specific instance?

    - by mafutrct
    This is more of a documentation than a real question. I noticed the principle it is not described on SO yet (did I miss it?), so here goes: Imagine a generic class that contains a static member: class Foo<T> { public static int member; } Is there a new instance of the member for each specific class, or is there only a single instance for all Foo-type classes? It can easily be verified by code like this: Foo<int>.member = 1; Foo<string>.member = 2; Console.WriteLine (Foo<int>.member); What is the result, and where is this behavior documented?

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