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  • Java performance issue

    - by Colby77
    Hi, I've got a question related to java performance and method execution. In my app there are a lot of place where I have to validate some parameter, so I've written a Validator class and put all the validation methods into it. Here is an example: public class NumberValidator { public static short shortValidator(String s) throws ValidationException{ try{ short sh = Short.parseShort(s); if(sh < 1){ throw new ValidationException(); } return sh; }catch (Exception e) { throw new ValidationException("The parameter is wrong!"); } } ... But I'm thinking about that. Is this OK? It's OO and modularized, but - considering performance - is it a good idea? What if I had awful lot of invocation at the same time? The snippet above is short and fast, but there are some methods that take more time. What happens when there are a lot of calling to a static method or an instance method in the same class and the method is not synchronized? All the calling methods have to fall in line and the JVM executes them sequentially? Is it a good idea to have some class that are identical to the above-mentioned and randomly call their identical methods? I think it is not, because "Don't repeat yourself " and "Duplication is Evil" etc. But what about performance? Thanks is advance.

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  • Creating a QMainWindow from Java using JNI

    - by ebasconp
    Hi everybody: I'm trying to create a Qt main windows from Java using JNI directly and I got a threading error. My code looks like this: Test class: public class Test { public static void main(String... args) { System.out.println(System.getProperty("java.library.path")); TestWindow f = new TestWindow(); f.show(); } } TestWindow class: public class TestWindow { static { System.loadLibrary("mylib"); } public native void show(); } C++ impl: void JNICALL Java_testpackage_TestWindow_show (JNIEnv *, jobject) { int c = 0; char** a = NULL; QApplication* app = new QApplication(c, a); QMainWindow* mw = new QMainWindow(); mw->setWindowTitle("Hello"); mw->setGeometry(150, 150, 400, 300); mw->show(); QApplication::exec(); } and I get my window painted but frozen (it does not receive any event) and the following error message when instantiating the QMainWindow object: QCoreApplication::sendPostedEvents: Cannot send posted events for objects in another thread I know all the UI operations must done in the UI thread but in my example I created the QApplication in the only thread I have running, so, everything should work properly. I did some tests executing the code of my "show" method from a QMetaObject::invokeMethod stuff using Qt::QueuedConnection but nothing works properly. I know I could use Jambi... but I know that it could be done natively too and that is what I want to do :) Any ideas on this? Thanks in advance! Ernesto

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  • how to count all distinct records in many-to-many relations in django ORM?

    - by marduk-pl
    hi, i have two models: class Project(models.Model): categories = models.ManyToManyField(Category) class Category(models.Model): name = models.CharField() now, i make some queryset: query = Project.objects.filter(id__in=[1,2,3,4]) and i like to get list of all distinct categories in this queryset with count of projects with refering to these categories - exactly i would like to get that results: category1 - 10 projects category2 - 5 projects that is opposite to this query: query2 = query.annotate(Count('categories')) what return me: project1 - 2categories project2 - 7categories how can i make it in django ORM?

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  • Castle Active Record - Working with the cache

    - by David
    Hi All, im new to the Castle Active Record Pattern and Im trying to get my head around how to effectivley use cache. So what im trying to do (or want to do) is when calling the GetAll, find out if I have called it before and check the cache, else load it, but I also want to pass a bool paramter that will force the cache to clear and requery the db. So Im just looking for the final bits. thanks public static List<Model.Resource> GetAll(bool forceReload) { List<Model.Resource> resources = new List<Model.Resource>(); //Request to force reload if (forceReload) { //need to specify to force a reload (how?) XmlConfigurationSource source = new XmlConfigurationSource("appconfig.xml"); ActiveRecordStarter.Initialize(source, typeof(Model.Resource)); resources = Model.Resource.FindAll().ToList(); } else { //Check the cache somehow and return the cache? } return resources; } public static List<Model.Resource> GetAll() { return GetAll(false); }

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  • JavaScript: using constructor without operator 'new'

    - by GetFree
    Please help me to understand why the following code works: <script> var re = RegExp('\\ba\\b') ; alert(re.test('a')) ; alert(re.test('ab')) ; </script> In the first line there is no new operator. As far as I know, a contructor in JavaScript is a function that initialize objects created by the operator new and they are not meant to return anything.

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  • Naming Suggestions For A Function Providing Chaining In A Different Way

    - by sid3k
    I've coded an experimental function which makes passed objects chainable by using high order functions. It's name is "chain" for now, and here is a usage example; chain("Hello World") (print) // evaluates print function by passing "Hello World" object. (console.log,"Optional","Parameters") (returnfrom) // returns "Hello World" It looks lispy but behaves very different since it's coded in a C based language, I don't know if there is a name for this idiom and I couldn't any name more suitable than "chain". Any ideas, suggestions?

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  • doubleton pattern in C++

    - by benjamin button
    I am aware of the singleton pattern in C++. but what is the logic to get two instances of the object? is there any such pattern where we could easily get 2 pattern. for the logic i could think of is that i can change the singleton pattern itself to have two objects created inside the class.this works. but if the requirement grows like if i need only 3 or only 4 what is the deswign pattern that i could think of to qualify such requirement?

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  • How can i add list data in my object?

    - by Phsika
    Below codes run perfectly but i want to re generate simply static void YeniMethodListele() { Calisan calisan = new Calisan(){ ID=1, Ad="yusuf", SoyAd="karatoprak"}; List<Calisan> myList = new List<Calisan>(); myList.Add(calisan); MyCalisan myCalisan = new MyCalisan() { list = myList }; //myCalisan.list.Add(calisan); foreach (Calisan item in myCalisan.list) { Console.WriteLine(item.Ad.ToString()); } } } public class Calisan { public int ID { get; set; } public string Ad { get; set; } public string SoyAd { get; set; } } public class MyCalisan { public List<Calisan> list { get; set; } public MyCalisan() { list = new List<Calisan>(); } } static void YeniMethodListele() { Calisan calisan = new Calisan(){ ID=1, Ad="yusuf", SoyAd="karatoprak"}; MyCalisan myCalisan = new MyCalisan(); myCalisan.list.Add(calisan); foreach (Calisan item in myCalisan.list) { Console.WriteLine(item.Ad.ToString()); } } } public class Calisan { public int ID { get; set; } public string Ad { get; set; } public string SoyAd { get; set; } } public class MyCalisan { public List<Calisan> list { get; set; } public MyCalisan() { list = new List<Calisan>(); } }

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  • Some questions about Vector in STL

    - by skydoor
    I have some questions about vector in STL to clarify..... Where are the objects in vector allocated? heap? does vector have boundary check? If the index out of the boundary, what error will happen? Why array is faster than vector? Is there any case in which vector is not applicable but array is a must?

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  • Parallel.For maintain input list order on output list

    - by romeozor
    I'd like some input on keeping the order of a list during heavy-duty operations that I decided to try to do in a parallel manner to see if it boosts performance. (It did!) I came up with a solution, but since this was my first attempt at anything parallel, I'd need someone to slap my hands if I did something very stupid. There's a query that returns a list of card owners, sorted by name, then by date of birth. This needs to be rendered in a table on a web page (ASP.Net WebForms). The original coder decided he would construct the table cell-by-cell (TableCell), add them to rows (TableRow), then each row to the table. So no GridView, allegedly its performance is bad, but the performance was very poor regardless :). The database query returns in no time, the most time is spent on looping through the results and adding table cells etc. I made the following method to maintain the original order of the list: private TableRow[] ComposeRows(List<CardHolder> queryResult) { int queryElementsCount = queryResult.Count(); // array with the query's size var rowArray = new TableRow[queryElementsCount]; Parallel.For(0, queryElementsCount, i => { var row = new TableRow(); var cell = new TableCell(); // various operations, including simple ones such as: cell.Text = queryResult[i].Name; row.Cells.Add(cell); // here I'm adding the current item to it's original index // to maintain order in the output list rowArray[i] = row; }); return rowArray; } So as you can see, because I'm returning a very different type of data (List<CardHolder> -> TableRow[]), I can't just simply omit the ordering from the original query to do it after the operations. Also, I also thought it would be a good idea to Dispose() the objects at the end of each loop, because the query can return a huge list and letting cell and row objects pile up in the heap could impact performance.(?) How badly did I do? Does anyone have a better solution in case mine is flawed?

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  • DesignTime data not showing in Blend when bound against CollectionViewSource

    - by bitbonk
    I have datatemplate for a viewmodel where an itemscontrol is bound again a CollectionViewSource (to enable sorting in xaml). <DataTemplate x:Key="equipmentDataTemplate"> <Viewbox> <Viewbox.Resources> <CollectionViewSource x:Key="viewSource" Source="{Binding Modules}"> <CollectionViewSource.SortDescriptions> <scm:SortDescription PropertyName="ID" Direction="Ascending"/> </CollectionViewSource.SortDescriptions> </CollectionViewSource> </Viewbox.Resources> <ItemsControl ItemsSource="{Binding Source={StaticResource viewSource}}" Height="{DynamicResource equipmentHeight}" ItemTemplate="{StaticResource moduleDataTemplate}"> <ItemsControl.ItemsPanel> <ItemsPanelTemplate> <StackPanel Orientation="Horizontal" /> </ItemsPanelTemplate> </ItemsControl.ItemsPanel> </ItemsControl> </Viewbox> </DataTemplate> I have also setup the UserControl where all of this is defined to provide designtime data d:DataContext="{x:Static vm:DesignTimeHelper.Equipment}"> This is basically a static property that gives me an EquipmentViewModel that has a list of ModuleViewModels (Equipment.Modules). Now as long as I bind to the CollectionViewSource the designtime data does not show up in blend 3. When I bind to the ViewModel collection directly <ItemsControl ItemsSource="{Binding Modules}" I can see the designtime data. Any idea what I could do?

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  • sem-dynamic cdn

    - by dwi kristianto
    i'm developing couple of websites using php (directory script, etc.) and wordpress as cms. i need to improve its performance, by using cdn for static files (css, js, images). the problem is, css and javascript files are generated on the fly. i did that due to yahoo and some expert advice to combine the files into one file. also changing basic color of css files. for the time being, i use couple of small vps but still its not fast enough. i already contact maxcdn and the support guy said that they dont have such kind of services. what i need is: a cdn that will serve the request from user/visitor and there's no file in local disk, the cdn will redirect/fetch it from another domain/server. in vps, it could be done easily using combination of .htaccess and php, but NOT in the cdn. most of cdn only support purely static files. is there any such cdn that will server semi-dynamic files?

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  • Interface in a dynamic language?

    - by Bryan
    Interface (or an abstract class with all the methods abstract) is a powerful weapon in a static language. It allows different derived types to be used in a uniformed way. However, in a dynamic language, all objects can be used in a uniformed way as long as they define certain methods. Does interface exist in dynamic languages? It seems unnecessary to me.

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  • django - variable declared in base project does not appear in app

    - by unsorted
    I have a variable called STATIC_URL, declared in settings.py in my base project: STATIC_URL = '/site_media/static/' This is used, for example, in my site_base.html, which links to CSS files as follows: <link rel="stylesheet" href="{{ STATIC_URL }}css/site_tabs.css" /> I have a bunch of templates related to different apps which extend site_base.html, and when I look at them in my browser the CSS is linked correctly as <link rel="stylesheet" href="/site_media/static/css/site_tabs.css" /> (These came with a default pinax distribution.) I created a new app called 'courses' which lives in the ...../apps/courses folder. I have a view for one of the pages in courses called courseinstance.html which extends site_base.html just like the other ones. However, when this one renders in my browser it comes out as <link rel="stylesheet" href="css/site_tabs.css" /> as if STATIC_URL were equal to "" for this app. Do I have to make some sort of declaration to get my app to take on the same variable values as the project? I don't have a settings.py file for the app. by the way, the app is listed in my list of INSTALLED_APPS and it gets served up fine, just without the link to the CSS file (so the page looks funny). Thanks in advance for your help.

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  • VB .Net LINQ query to determine whether more than one element has the same value for a property?

    - by Alex Hope O'Connor
    I am trying to write a LINQ query which will return true if there are multiple objects which have a property with the same value. Here is what I have come up with so far: Formatters.Where(Function(f As DataModel.Formatter) _ Formatters.Select(Function(f2 As DataModel.Formatter) f2.Name.ToLower()).Contains(f.Name.ToLower())).Count > 1 However the above always returns true as long as their are more then 1 elements in the list, can someone please give me a hand with this? Thanks, Alex.

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  • updating system's time using .Net

    - by user62958
    I am trying to update my system time using the following: [StructLayout(LayoutKind.Sequential)] private struct SYSTEMTIME { public ushort wYear; public ushort wMonth; public ushort wDayOfWeek; public ushort wDay; public ushort wHour; public ushort wMinute; public ushort wSecond; public ushort wMilliseconds; } [DllImport("kernel32.dll", EntryPoint = "GetSystemTime", SetLastError = true)] private extern static void Win32GetSystemTime(ref SYSTEMTIME lpSystemTime); [DllImport("kernel32.dll", EntryPoint = "SetSystemTime", SetLastError = true)] private extern static bool Win32SetSystemTime(ref SYSTEMTIME lpSystemTime); public void SetTime() { TimeSystem correctTime = new TimeSystem(); DateTime sysTime = correctTime.GetSystemTime(); // Call the native GetSystemTime method // with the defined structure. SYSTEMTIME systime = new SYSTEMTIME(); Win32GetSystemTime(ref systime); // Set the system clock ahead one hour. systime.wYear = (ushort)sysTime.Year; systime.wMonth = (ushort)sysTime.Month; systime.wDayOfWeek = (ushort)sysTime.DayOfWeek; systime.wDay = (ushort)sysTime.Day; systime.wHour = (ushort)sysTime.Hour; systime.wMinute = (ushort)sysTime.Minute; systime.wSecond = (ushort)sysTime.Second; systime.wMilliseconds = (ushort)sysTime.Millisecond; Win32SetSystemTime(ref systime); } When I debug everything looks good and all the values are correct but when it calles the Win32SetSystemTime(ref systime) th actual time of system(display time) doesn't change and stays the same. The strange part is that when I call the Win32GetSystemTime(ref systime) it gives me the new updated time. Can someone give me some help on this?

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  • What is Object Decomposition?

    - by Mustafa
    Hi everyone, I was trying to understand what object decomposition means and read a lot of stuff on internet but every resource talks in terms of lots of keywords that i couldn't understand. So these resources expect you to know a few terms. I need something that lists the basics of decomposition from scratch. Is it anything more than breaking the design into objects? If no, any description will be appreciated. Thanks in advance

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  • Error while compiling the Xcode project (IPhone)

    - by Sridhar
    Hello, I added ffmpeg iphone port into my library and I can able to use a few of its functions like avcodec_init(),.. without any errors. But when I include this function call "avcodec_register_all" Xcode is giving error after compilation The error message is : *--------------- ld: ldr 12-bit displacement out of range (4276 max +/-4096) in _CFRelease$stub in _CFRelease$stub from /Users/foxit/Documents/CameraTest/build/CameraTest.build/Debug-iphoneos/CameraTest.build/Objects-normal/armv6/CameraTest Command /Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc-4.2 failed with exit code 1 *------------- Does anyone know whats wrong with this ? Regards, Raghu

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  • Implementing dynamic scope when using CPS as intermediate language

    - by asandroq
    I am currently studying the implementation of programming languages and became interested in using Continuation-Passing Style as the intermediate language of the compiler. I also want to implement limited dynamic scope (for exception-handling or Scheme parameter objects) but I cannot find the relevant literature. I think it can be done with a separate environment passed as a variable to every closure, but this solution seems ugly to me. Could anyone point me to the relevant literature, or give me an idea of how this can be done?

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  • how to extend wpf combo box to bind data?

    - by Shaihan
    i need to bind a collection of objects to a combo box which i can use in different forms. so i want create a custom control which binds the collection to the combo box? how t do it by extending combo box? also how can i define the ItemData template?

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  • Beginner: Restore previously serialized JFrame-object, how?

    - by elementz
    Hi all. I have managed to serialize my very basic GUI-object containing a JTextArea and a few buttons to a file 'test.ser'. Now, I would like to completely restore the previously saved state from 'test.ser', but seem to have a misconception of how to properly deserialize an objects state. The class MyFrame creates the JFrame and serializes it. Now I tried to deserialize like so: public class Deserialize { static Deserialize ds; MyFrame frame; public static void main(String[] args) { try { ds.deserialize(); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public void deserialize() throws ClassNotFoundException { try { ObjectInputStream ois = new ObjectInputStream(new FileInputStream("test.ser")); frame = (MyFrame) ois.readObject(); ois.close(); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } Maybe somebody could point me into the direction where my misconception is? Thx in advance!

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  • Protobuf-net Deserialize Open Street Maps

    - by jonperl
    For the life of me I cannot deserialize the protobuf file from Open Street Maps. I am trying to deserialize the following extract: http://download.geofabrik.de/osm/north-america/us-northeast.osm.pbf to get Nodes and I am using http://code.google.com/p/protobuf-net/ as the library. I have tried to deserialize a bunch of different objects but they all come up null. The proto files can be found here: http://trac.openstreetmap.org/browser/applications/utils/export/osm2pgsql/protobuf Any suggestions?

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