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  • Why thread started by ScheduledExecutorService.schedule() never quits?

    - by moonese
    If I create a scheduled task by calling ScheduledExecutorService.schedule(), it never quits after execution, is it a JDK bug, or I just miss something? note: doSomething() is empty method below. public static void doSomething() { } public static void main(String[] args) { ScheduledFuture scheduleFuture = Executors.newSingleThreadScheduledExecutor().schedule(new Callable() { public Void call() { try { doSomething(); } catch (Exception e) { e.printStackTrace(); } return null; } }, 1, TimeUnit.SECONDS); }

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  • Why System.String's beahaves like a value type?

    - by Sorush Rabiee
    I want to write a 'Date' class that behaves like a Value Type. for example, Instead of writing a Clone method for setting properties safely, make the Date class to pass by value: public Date Birthday { get { return this.birthday; } set { this.birthday = value.Clone(); } //I want to write this.birthday = value; //without changing external value when this.Birthday changes } I know this is possible because System.String is a class and behaves like a value. for example: String s1 = "Hello"; String s2 = "Hi"; s1 = s2; s2="Hello"; Console.WriteLine(s1); //Prints 'Hi' First I thought writers of this class override '=' operator, but now I know that the '=' operator can not be overridden. so how they write String class?

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  • Why is my socket closing?

    - by Tommy3244
    Ok, so I am making a multiplayer game. I am working out the kinks in the server/client connectivity system. I can't seam to work out this error. Mainly, my server code does the following: Accepts Client Using SocketServer Module CLIENT -- SERVER sends Login byte (1 byte) + login username and password (200 bytes) SERVER request for 1 byte by struct.calcsize('b') CLIENT has exception on read SERVER recieves byte from CLIENT and sends CLIENT a struct packed byte with the value of 4 SERVER has exception on send So, it is the client excepting. The client exception is: socket.error: (10054, 'Connection reset by peer') And the server error is this: error: (9, 'Bad file descriptor')

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  • Why are interfaces unusable in PHP?

    - by streetparade
    I mean an interface definition without defining the return type makes it unusable? This makes more Clear Interface run { public function getInteger(); } class MyString implements run { public function myNumber() { } public function getInteger() { return "Not a number"; } } In Java every Interface has a return type like Integer,String,Void I know that PHP is unfortunately a loosly typed Language but isnt there a Solution for that Problem? Is it Possible to defining a Interface with a Return type like Integer?

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  • Why is there no Sum() extension for IEnumerable<uint>

    - by dss539
    It seems that Sum not defined for IEnumerable<uint> (and other unsigned integers, for that matter) var s = new int[] { 1, 2, 3 }; s.Sum(); //works fine var us = new uint[] { 1, 2, 3 }; us.Sum(); //missing method I would like to know: Have I done something fundamentally wrong/misunderstood the situation? What design decisions might cause the omission of IEnumerable<uint>.Sum()? MSDN: Enumerable.Sum

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  • why Haskell can deduce [] type in this function

    - by Sili
    rho x = map (((flip mod) x).(\a -> a^2-1)) (rho x) This function will generate an infinite list. And I tested in GHCi, the function type is *Main> :t rho rho :: Integral b => b -> [b] If I define a function like this fun x = ((flip mod) x).(\a -> a^2-1) The type is *Main> :t fun fun :: Integral c => c -> c -> c My question is, how can Haskell deduce the function type to b - [b]? We don't have any [] type data in this function. Thanks!

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  • Why does java.util.concurrent.ArrayBlockingQueue use 'while' loops instead of 'if' around calls to

    - by theFunkyEngineer
    I have been playing with my own version of this, using 'if', and all seems to be working fine. Of course this will break down horribly if signalAll() is used instead of signal(), but if only one thread at a time is notified, how can this go wrong? Their code here - check out the put() and take() methods; a simpler and more-to-the-point implementation can be seen at the top of the JavaDoc for Condition. Relevant portion of my implementation below. public Object get() { lock.lock(); try { if( items.size() < 1 ) hasItems.await(); Object poppedValue = items.getLast(); items.removeLast(); hasSpace.signal(); return poppedValue; } catch (InterruptedException e) { e.printStackTrace(); return null; } finally { lock.unlock(); } } public void put(Object item) { lock.lock(); try { if( items.size() >= capacity ) hasSpace.await(); items.addFirst(item); hasItems.signal(); return; } catch (InterruptedException e) { e.printStackTrace(); } finally { lock.unlock(); } } P.S. I know that generally, particularly in lib classes like this, one should let the exceptions percolate up.

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  • why won't background change in firefox but it will in ie

    - by rod
    <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title></title> <link id="csslink" href="Handler.ashx" rel="stylesheet" type="text/css" /> </head> <body> <form id="form1" runat="server"> <div> <input id="Button1" type="button" value="Blue" /> <input id="Button2" type="button" value="Red" /> </div> </form> <script type="text/javascript"> var pageDefault = { btn1: document.getElementById('Button1'), btn2: document.getElementById('Button2'), csslink: document.getElementById('csslink'), init: function() { this.btn1.onclick = function() { pageDefault.csslink.href = "Handler.ashx?id=1"; } this.btn2.onclick = function() { pageDefault.csslink.href = "Handler.ashx?id=2"; } } } pageDefault.init(); </script> </body> </html> Here's the ashx ProcessRequest public void ProcessRequest(HttpContext context) { context.Response.ContentType = "text/plain"; var id = context.Request.QueryString["id"]; if (id == "1") { context.Response.Write(@" body { background: Blue; } "); } else if (id == "2") { context.Response.Write(@" body { background: Red; } "); } else { } }

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  • why my home page not showing in google ?

    - by user298788
    hello members i have 1 site : http://www.magentocommerceexperts.com/ it is not showing cache in google toolabr also i am not getiing result properly also other pages has been cached and it showing and the site genrated in wordpress so will u show me whats a problem. all seo stuff done completd and i am facing problem since 2 months

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  • why do I need virtual table?

    - by lego69
    I was looking for some information about virtual table, but can't find something easy to understand, can somebody give me good example(not from Wiki, please), with explanations, or link, thanks in advance

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  • Why isn't div centering?

    - by user2898276
    I'm trying to centre a logo in the middle of the browser. I have this so far... <script type="text/javascript"> $(document).ready(function(){ $(window).resize(function(){ $('#theLogo').css({ position:'absolute', left: ($(window).width() - $('#theLogo').outerWidth())/2, top: ($(window).height() - $('#theLogo').outerHeight())/2 }); }); $(window).resize(); }); HTML <div id="theLogo"> <section id="responsiveLogo" class="logo">September</section> </div> I'm trying to centre this bit: <section id="responsiveLogo" class="logo">September</section> Live version here

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  • Why the gtk windows hangs?

    - by httpinterpret
    void forloop2() { int i = 0; while(TRUE) { printf("forloop2\n"); } } int main() { GtkWidget *window; g_thread_init(NULL); gdk_threads_init(); g_thread_create((GThreadFunc)forloop2, NULL, FALSE, NULL); gtk_init(NULL, NULL); window = gtk_window_new(GTK_WINDOW_TOPLEVEL); gtk_widget_show_all (window); gtk_main(); } It seems the created thread affects gtk_window_new(my programe hangs here), how do I do it correctly?

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  • When I do ""+1 I get a String - Why

    - by steve
    Hi, Please understand firstly that I fully understand that Java will return a String when I use ""+int. What I'm really not sure about is what exactly is happening down at the memory aspect. How exactly is java performing this conversion. I mean this in a very indepth way, not 'auto boxing' or anything like that :) I'm hoping someone with a deeper understanding can explain what exactly is done.

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  • Why isn't this working - using :not() with an event handler

    - by james emanon
    I seem to have another issue that I am not conquering. Real simple premise. I have a mousedown event, and basically IF one particular element on the page is clicked, I want nothing to happen, else I want hide() some div. $(function(){ $("document :not(#_ignorelement)").mousedown(function(event){ if($('#_hidethiselement').length){ $('#_hidethiselement').hide(); } }) }) That is not working at all. I also tried the following: $(document).not($("#_ignorelement")).mousedown(function(event){ $(document).not("_ignorelement").mousedown(function(event){ IF I can solve that, curious how I would actually have ":not" encompass the parent div, like so: $().not("_ignoreelement").parent().closest('div').mousedown(function Because the element "_ignorelement" is an anchor tag that is in a div. Wonder how I can use the parent div perhaps, instead of the anchor tag. Anyways, any help would be appreciated.

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  • Why this script is not validating the form

    - by danishjan
    This is registration form code. i wrote script in one i have accessed every element by Id and in One by name but both donot validation it. <div id="form"> <form action="" method="get" id="formdata" > <p> <label for="firstName" class="labels">&nbsp; &nbsp;First Name </label> <input type="text" name="firstName" id="firstName" placeholder="First Name" /> <label for="firstName" id="errorfirstName" style="color:red; font- size:14px; visibility:hidden;"> Please Enter First Name </label> </p> <p> <label for="lastName" class="labels">&nbsp; &nbsp;Last Name </label> <input type="text" name="lastName" id="lastName" placeholder="Last Name" /> <label for="lastName" id="errorlastName" style="color:red; font-size:14px; visibility:hidden;"> Please Enter Last Name</label> </p> <p> <label for="fatherName" class="labels">Father Name</label> <input type="text" name="fatherName" id="fatherName" placeholder="Father Name" /> <label for="fatherName" id="errorfatherName" style="color:red; font- size:14px; visibility:hidden;"> Please Enter Father Name </label> </p> <p> <label for="classNo" class="labels">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Class </label> <input type="text" name="classNo" id="classNo" placeholder="Class" /> <label for="classNo" id="errorclassNo" style="color:red; font-size:14px; visibility:hidden;"> Please Enter Class </label> </p> <p> <label for="address" class="labels">&nbsp; &nbsp; &nbsp; &nbsp;Address </label> <input type="text" name="address" id="address" placeholder="Address" /> <label for="address" id="erroraddress" style="color:red; font-size:14px; visibility:hidden;"> Please Enter Address </label> </p> <p> <input type="submit" value="Submit" onSubmit="return validate()" /> </p> </form> And the JavaScript Code is here. What is wrong with this code. This code is through accessing by Element Id. <script type="text\javascript"> function validate(){ var valid=true; var fname=document.getElementById("firstName"); var lname=document.getElementById("lastName"); var fathname=document.getElementById("fatherName"); var classno=document.getElementById("classNo"); var address=document.getElementById("address"); var errfname=document.getElementById("errorfirstName"); var errlname=document.getElementById("errorlastName"); var errfathname=document.getElementById("errorfatherName"); var errclass=document.getElementById("errorclass"); var erraddress=document.getElementById("erroraddress"); if(fname.value == ""){ errfname.style.visibility="visible"; valid=false; } if(lname.value == ""){ errlname.style.visibility="visible"; valid=false; } if(fathname.value == ""){ errfathname.style.visibility="visible"; valid=false; } if(classno.value == ""){ errclass.style.visibility="visible"; valid=false; } if(address.value == ""){ erraddress.style.visibility="visible"; valid=false; } return valid; } </script>

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  • Why do @synthesize variable names begin with an _?

    - by mcjoejoe0911
    I'm just starting to use Objective-C and I need to clarify something When I @synthesize a @property, it is common convention to do the following: @interface Class : ParentClass @property propertyName @end @implementation @synthesize propertyName = _propertyName; @end I've seen plenty of questions and answers suggesting that "_propertyName" is widely accepted as the "correct" way to synthesize properties. However, does it serve ANY purpose? Or is it merely to increase readability and identify instance variables?

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  • On mobile is there a reason why processes are often short lived and must persist their state explicitly?

    - by Alexandre Jasmin
    Most mobile platforms (such as Android, iOS, Windows phone 7 and I believe the new WinRT) can kill inactive application processes under memory pressure. To prevent this from affecting the user experience applications are expected to save and restore their state as their process is killed and restarted. Having application processes killed in this way makes the developers job harder. On various occasions I've seen a mobile app that would: Return to the welcome screen each time I switch back to it. Crash when I switch back to it (possibly accessing some state that no longer exists after the process was killed) Misbehave when I switch back to it (sometimes requiring a restart or tasks killer to fix) Otherwise misbehave in some hard to reproduce way (e.g. android service killed and restarted at the wrong time) I don't really understand why these mobile operating systems are designed to kill tasks in this way especially since it makes application development more difficult and error prone. Desktop operating systems don't kill processes like that. They swap out unused pages of memory to mass storage. Is there a reason why the same approach isn't used on mobile? Mobile hardware is only a few years behind PC hardware in term of performance. I'm sure there are very good reasons why mobile operating systems are designed this way. If you can point me to a paper or blog post that explain these reasons or can give me some insight I'd very much appreciate it.

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  • 2D platformers: why make the physics dependent on the framerate?

    - by Archagon
    "Super Meat Boy" is a difficult platformer that recently came out for PC, requiring exceptional control and pixel-perfect jumping. The physics code in the game is dependent on the framerate, which is locked to 60fps; this means that if your computer can't run the game at full speed, the physics will go insane, causing (among other things) your character to run slower and fall through the ground. Furthermore, if vsync is off, the game runs extremely fast. Could those experienced with 2D game programming help explain why the game was coded this way? Wouldn't a physics loop running at a constant rate be a better solution? (Actually, I think a physics loop is used for parts of the game, since some of the entities continue to move normally regardless of the framerate. Your character, on the other hand, runs exactly [fps/60] as fast.) What bothers me about this implementation is the loss of abstraction between the game engine and the graphics rendering, which depends on system-specific things like the monitor, graphics card, and CPU. If, for whatever reason, your computer can't handle vsync, or can't run the game at exactly 60fps, it'll break spectacularly. Why should the rendering step in any way influence the physics calculations? (Most games nowadays would either slow down the game or skip frames.) On the other hand, I understand that old-school platformers on the NES and SNES depended on a fixed framerate for much of their control and physics. Why is this, and would it be possible to create a patformer in that vein without having the framerate dependency? Is there necessarily a loss of precision if you separate the graphics rendering from the rest of the engine? Thank you, and sorry if the question was confusing.

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