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  • java casting confusion

    - by Stardust
    Could anyone please tell me why the following casting is resulting in compile time error: Long l = (Long)Math.pow(5,2); But why not the following: long l = (long)Math.pow(5,2);

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  • Use cellular emulator with a REAL WinMo device?

    - by Ranhiru
    I don't whether this is even possible which is obviously why I am asking this question :) Is it in any way possible to leverage functionality the Cellular Emulator on a REAL PHYSICAL device?? :) So when I test it on my device, I really do not have to send real SMS(s) to test my MessageInteceptor. On a sidenote, why does MessageInteceptor fails after several messages to intercept messages?? :( Thanx a lot in advance :)

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  • What happens when several Java servlet apps running on the same port ?

    - by Frank
    Something strange happened to my servlets and I think I've figured out why, yet I'm more confused. I used Netbean6.7 to develop a Paypal IPN (Instant Payment Notification) message servlet, it listens on port 8080 by default for Paypal IPN messages. I used some sample Java code from it's web site, but when it ran, only about 1 in 10 messages came through, and they looked correct, but why 1 in 10 ? Not 100% or none ? So I asked some questions here and got some advices, one in particular points me to Google's App Engine, so I downloaded it and ran the demo guestbook while my IPN servlet is still running on Netbeans, the strange thing happened, after I entered "appengine-java-sdk-1.3.2\bin\dev_appserver.cmd appengine-java-sdk-1.3.2\demos\guestbook\war" from the command prompt, I went to the following url on my browser "http://localhost:8080/", I thought I would see the Google demo guestbook page, NO, what I saw was another servlet I developed 2 years ago : "Web Academy", online course registration app. How can that happen ? I never started it, and I haven't touch that project for years. I guess because it's also listening on port 8080, so now I understand why the IPN messages only came through 1 in 10 times, because another servlet was also listening on that port and could have got the messages intended for IPN, or some how those two servlets' processes mixed up and therefore couldn't respond to Paypal properly, and failed. In order to verify some of my guesses, I turn off Netbeans, and ran the Google guestbook again at the prompt, this time on my browser http://localhost:8080/ points to the demo guestbook page. My Urls look like this : [A] Paypal IPN : http://localhost:8080/PayPal_App/PayPal_Servlet [B] Web Academy : http://localhost:8080/ So now, my questions are : <1> Why the "Web Academy" servlet was auto started when I ran the Paypal servlet ? <2> If I change the IPN listening port to 8083, would that mean I can run both of them on my PC at the same time without affecting each other ? <3> But I still don't understand, [A] and [B] look different, if a page for [A] is refreshed, it should show the Paypal content, and another page looking at [B] should show the Web Academy content, and that's exactly what happens when I started Netbeans to run the Paypal servlet, both pages show their respective content correctly side by side without interfering with each other, how come the IPN messages couldn't get through 100% of the time ? <4> In Netbeans how to assign 8080 to servlet [A] and assign port 8083 to servlet [B] ? <5> How to turn off auto start of Web Academy by Netbeans ?

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  • ASP.Net ViewState doesn't work when Control become Enable=False

    - by Daok
    Why when a control does contain value but it's set to .Enable=False that all controls become disable (that's ok) but why that the ViewState doesn't retain the data on the next post back? If I get the UserControl without modifing its Enable state, the ViewState work between post back. How can we disable a UserControl that all its control become disable (this part work) but all of them KEEP use the ViewState (this doesn't work)?

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  • DataAnnotation attributes buddy class strangeness - ASP.NET MVC

    - by JK
    Given this POCO class that was automatically generated by an EntityFramework T4 template (has not and can not be manually edited in any way): public partial class Customer { [Required] [StringLength(20, ErrorMessage = "Customer Number - Please enter no more than 20 characters.")] [DisplayName("Customer Number")] public virtual string CustomerNumber { get;set; } [Required] [StringLength(10, ErrorMessage = "ACNumber - Please enter no more than 10 characters.")] [DisplayName("ACNumber")] public virtual string ACNumber{ get;set; } } Note that "ACNumber" is a badly named database field, so the autogenerator is unable to generate the correct display name and error message which should be "Account Number". So we manually create this buddy class to add custom attributes that could not be automatically generated: [MetadataType(typeof(CustomerAnnotations))] public partial class Customer { } public class CustomerAnnotations { [NumberCode] // This line does not work public virtual string CustomerNumber { get;set; } [StringLength(10, ErrorMessage = "Account Number - Please enter no more than 10 characters.")] [DisplayName("Account Number")] public virtual string ACNumber { get;set; } } Where [NumberCode] is a simple regex based attribute that allows only digits and hyphens: [AttributeUsage(AttributeTargets.Property)] public class NumberCodeAttribute: RegularExpressionAttribute { private const string REGX = @"^[0-9-]+$"; public NumberCodeAttribute() : base(REGX) { } } NOW, when I load the page, the DisplayName attribute works correctly - it shows the display name from the buddy class not the generated class. The StringLength attribute does not work correctly - it shows the error message from the generated class ("ACNumber" instead of "Account Number"). BUT the [NumberCode] attribute in the buddy class does not even get applied to the AccountNumber property: foreach (ValidationAttribute attrib in prop.Attributes.OfType<ValidationAttribute>()) { // This collection correctly contains all the [Required], [StringLength] attributes // BUT does not contain the [NumberCode] attribute ApplyValidation(generator, attrib); } Why does the prop.Attributes.OfType<ValidationAttribute>() collection not contain the [NumberCode] attribute? NumberCode inherits RegularExpressionAttribute which inherits ValidationAttribute so it should be there. If I manually move the [NumberCode] attribute to the autogenerated class, then it is included in the prop.Attributes.OfType<ValidationAttribute>() collection. So what I don't understand is why this particular attribute does not work in when in the buddy class, when other attributes in the buddy class do work. And why this attribute works in the autogenerated class, but not in the buddy. Any ideas? Also why does DisplayName get overriden by the buddy, when StringLength does not?

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  • c# string formatting

    - by user177883
    I m curious why would i use string formatting while i can use concatenation such as Console.WriteLine("Hello {0} !", name); Console.WriteLine("Hello "+ name + " !"); Why to prefer the first one over second?

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  • JS regex and angle brackets

    - by chaz
    Seriously, why can't I parse a string with angle brackets using the Javascript regular expression object? var r = new RegExp(), r; r.compile("\\<div\\>", "g"); r = r.exec("<div>Hello</div>"); //Equals null yo Why does that not work?

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  • bounding java generics by 'super' keyword

    - by mohsenof
    Why I can use 'super' just with wildcards and not with type parameters? for example why in Collection interface they've not written toArray method like this interface Collection"<"T{ public "< S super T S[] toArray(S[] a){ } } (sorry, I don't know how to deal with "<")

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  • Impossible to use ref and out in Extension methods?

    - by Hun1Ahpu
    Why is it forbidden to call Extension method with ref modifier? This one is possible: public static void Change(ref TestClass testClass, TestClass testClass2) { testClass = testClass2; } And this one not: public static void ChangeWithExtensionMethod(this ref TestClass testClass, TestClass testClass2) { testClass = testClass2; } But why?

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  • How come .net 4.0 and .net 2.0 CLR's can exist in a same machine

    - by Vinni
    I have a basic doubt that, How can we have both CLR's on a same machine. If this is possible, When I refer few dll's of 4.0 and setting application pool to 2.0 why Cant I run the website(I am getting errors).When we refer the dll's from web.config it means it searches for GAC when that particular 4.0 dll is available in GAC Why dont it load (How come it is not loading).. Please clarify my doubts

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  • Rails activerecord attributes=

    - by vinhboy
    Hi, I am doing this: @person.attributes = params[:person] Can anyone give me a clue as to why doing an attributes= would cause a bunch of SQL to show in my logs? I see a couple of SELECT and even an UPDATE. I swear I am not doing a "save" -- so I have no idea why setting attributes would trigger queries. Is there a before_ of after_ filter I am missing? Thanks.

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  • Java - Interfaces

    - by RayAllen
    I had a doubt .. Why do we need interface in Java ? Instead of interface can't we write the methods in the class itself ? Why do we need seperate interface?

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  • Cocoa for the non-techinical

    - by annoyed
    How would you describe and explain Cocoa in non-technical terms, with lots of analogies to common, everyday things. For example, imagine you are describing it to a 5-year-old who keeps asking why? at the end if each explanation. This would invariable delve into the theory of OO so it could get lengthy, but the concept is important to the 'why' of Cocoa.

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  • Pointer Arithmetic & Signed / Unsigned Conversions!

    - by Jay
    Incase of pointer arithmetic, are the integers automatically converted to their signed variants? If yes, why? Suppose I do pointer + uiVal where pointer is a pointer to int and uiVal is initialized to -1, then I find that the address in pointers get decremented by 4. Why is the unsigned value of -1 not considered here?

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  • Save object states in .data or attr - Performance vs CSS?

    - by Neysor
    In response to my answer yesterday about rotating an Image, Jamund told me to use .data() instead of .attr() First I thought that he is right, but then I thought about a bigger context... Is it always better to use .data() instead of .attr()? I looked in some other posts like what-is-better-data-or-attr or jquery-data-vs-attrdata The answers were not satisfactory for me... So I moved on and edited the example by adding CSS. I thought it might be useful to make a different Style on each image if it rotates. My style was the following: .rp[data-rotate="0"] { border:10px solid #FF0000; } .rp[data-rotate="90"] { border:10px solid #00FF00; } .rp[data-rotate="180"] { border:10px solid #0000FF; } .rp[data-rotate="270"] { border:10px solid #00FF00; } Because design and coding are often separated, it could be a nice feature to handle this in CSS instead of adding this functionality into JavaScript. Also in my case the data-rotate is like a special state which the image currently has. So in my opinion it make sense to represent it within the DOM. I also thought this could be a case where it is much better to save with .attr() then with .data(). Never mentioned before in one of the posts I read. But then i thought about performance. Which function is faster? I built my own test following: <!DOCTYPE HTML> <html> <head> <title>test</title> <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> <script type="text/javascript"> function runfirst(dobj,dname){ console.log("runfirst "+dname); console.time(dname+"-attr"); for(i=0;i<10000;i++){ dobj.attr("data-test","a"+i); } console.timeEnd(dname+"-attr"); console.time(dname+"-data"); for(i=0;i<10000;i++){ dobj.data("data-test","a"+i); } console.timeEnd(dname+"-data"); } function runlast(dobj,dname){ console.log("runlast "+dname); console.time(dname+"-data"); for(i=0;i<10000;i++){ dobj.data("data-test","a"+i); } console.timeEnd(dname+"-data"); console.time(dname+"-attr"); for(i=0;i<10000;i++){ dobj.attr("data-test","a"+i); } console.timeEnd(dname+"-attr"); } $().ready(function() { runfirst($("#rp4"),"#rp4"); runfirst($("#rp3"),"#rp3"); runlast($("#rp2"),"#rp2"); runlast($("#rp1"),"#rp1"); }); </script> </head> <body> <div id="rp1">Testdiv 1</div> <div id="rp2" data-test="1">Testdiv 2</div> <div id="rp3">Testdiv 3</div> <div id="rp4" data-test="1">Testdiv 4</div> </body> </html> It should also show if there is a difference with a predefined data-test or not. One result was this: runfirst #rp4 #rp4-attr: 515ms #rp4-data: 268ms runfirst #rp3 #rp3-attr: 505ms #rp3-data: 264ms runlast #rp2 #rp2-data: 260ms #rp2-attr: 521ms runlast #rp1 #rp1-data: 284ms #rp1-attr: 525ms So the .attr() function did always need more time than the .data() function. This is an argument for .data() I thought. Because performance is always an argument! Then I wanted to post my results here with some questions, and in the act of writing I compared with the questions Stack Overflow showed me (similar titles) And true enough, there was one interesting post about performance I read it and run their example. And now I am confused! This test showed that .data() is slower then .attr() !?!! Why is that so? First I thought it is because of a different jQuery library so I edited it and saved the new one. But the result wasn't changing... So now my questions to you: Why are there some differences in the performance in these two examples? Would you prefer to use data- HTML5 attributes instead of data, if it represents a state? Although it wouldn't be needed at the time of coding? Why - Why not? Now depending on the performance: Would performance be an argument for you using .attr() instead of data, if it shows that .attr() is better? Although data is meant to be used for .data()? UPDATE 1: I did see that without overhead .data() is much faster. Misinterpreted the data :) But I'm more interested in my second question. :) Would you prefer to use data- HTML5 attributes instead of data, if it represents a state? Although it wouldn't be needed at the time of coding? Why - Why not? Are there some other reasons you can think of, to use .attr() and not .data()? e.g. interoperability? because .data() is jquery style and HTML Attributes can be read by all... UPDATE 2: As we see from T.J Crowder's speed test in his answer attr is much faster then data! which is again confusing me :) But please! Performance is an argument, but not the highest! So give answers to my other questions please too!

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  • Get EXEC_BAD_ACCESS when I get the NSFileModificationDate

    - by Toto
    Hi everyone, I try to get the last modification date of a file: NSFileManager *fm = [[NSFileManager alloc] init]; NSError *err; NSDate *lastModif = [[fm attributesOfItemAtPath:filename error:&err] objectForKey:NSFileModificationDate];//filename is ok ;-) if(err == nil) { [lastModif retain]; //I can put a NSLog of lastModif here, it works !! NSTimeInterval lastModifDiff = [lastModif timeIntervalSinceNow];//crash here } I don't understand why the NSDate seems to be released, why the retain does not retain it. Thank you if you have any idea...

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  • Rails new vs create

    - by Senthil
    Why is there a need to define a new method in RESTful controller, follow it up with a create method? Google search didn't provide me the answer I was looking for. I understand the different, but need to know why they are used the way they are.

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  • inheritance from str or int

    - by wiso
    Why I have problem creating a class the inherite from str (or also int) class C(str): def __init__(self, a, b): str.__init__(self,a) self.b = b C("a", "B") TypeError: str() takes at most 1 argument (2 given) tha same appened if I try to use int instead of str, but it works with custom classes. I need to use __new__ instead of __init__? why?

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  • Using memcpy in the STL

    - by wowus
    Why does C++'s vector class call copy constructors? Why doesn't it just memcpy the underlying data? Wouldn't that be a lot faster, and remove half of the need for move semantics? I can't imagine a use case where this would be worse, but then again, maybe it's just because I'm being quite unimaginative.

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