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  • Java Interfaces Methodology: Should every class implement an interface?

    - by Amir Rachum
    I've been programming in Java for a few courses in the University and I have the following question: Is it methodologically accepted that every class should implement an interface? Is it considered bad practice not to do so? Can you describe a situation where it's not a good idea to use interfaces? Edit: Personally, I like the notion of using Interfaces for everything as a methodology and habit, even if it's not clearly beneficial. Eclipse automatically created a class file with all the methods, so it doesn't waste any time anyway.

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  • Why this friend function can't access a private member of the class?

    - by Alceu Costa
    I am getting the following error when I try to access bins private member of the GHistogram class from within the extractHistogram() implementation: error: 'QVector<double> MyNamespace::GHistogram::bins' is private error: within this context Where the 'within this context' error points to the extractHistogram() implementation. Does anyone knows what's wrong with my friend function declaration? Here's the code: namespace MyNamespace{ class GHistogram { public: GHistogram(qint32 numberOfBins); qint32 getNumberOfBins(); /** * Returns the frequency of the value i. */ double getValueAt(qint32 i); friend GHistogram * Gbdi::extractHistogram(GImage *image, qint32 numberOfBins); private: QVector<double> bins; }; GHistogram * extractHistogram(GImage * image, qint32 numberOfBins); }

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  • Wrap a list to add an empty row for UI binding.

    - by TheSean
    I am binding a List to a UI Control. My list does not contain a blank row, but I need to add one to allow the user to select blank. However, I'm using the same list in other parts of the application (users can edit/add/delete items) where it doesn't make sense to show a blank row. My idea is to create a wrapper around the list which adds a blank row just for the UI. The wrapper would hold a reference so that updates to the list (from other parts of the app) would be reflected in UI without any extra work. I have tried a few different ways, but nothing has worked out for me yet. Can anyone solve this problem?

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  • 2 compareTo method overriden in the same class definition, how could I force to use the second?

    - by jayjaypg22
    I want to sort a list List<Blabla> donnees by a criterion on one of its field. My problem is that compareTo is already overriden for this Class. So I've got something like : Blabla { public int compareTo(Object other) { ... } public int compareTo(Blabla other) { ... } } In a business layer class I call : Business { method (){ Collections.sort(List<Blabla > donnees); } } But this call N°1 compareTo method with object parameter. How could I sort my list with the N°2 method?

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  • How do i change Object to String in a class which extends AsyncTask?

    - by Filip V.
    I'm learning from Google's Android developing tutorial and i came across a problem. On this link https://developer.android.com/training/basics/network-ops/connecting.html#AsyncTask it says to create a class that extends AsyncTask. So when i write the class it automatically implements the method as follows: private Object doInBackground(Object... args) {..} //it's fine but when i try writing just as it says in the tutorial: private String doInBackground(String... args) {..} //it gives an error and the error says: The method doInBackground(String...) of type MainActivity.DownloadWebpageText must override a superclass method. So how do i change Object to String without getting an error there?

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  • Is possible to set generic type by another class?

    - by Soul_Master
    I use ASP.NET MVC for serving web application and I want to create something like the following code. <% using(HTML.Form(Model)) { %> <% HTML.CreateTextBox('txt1', x => x.Property1); <% } From the above code, Form extension method will receive object that represent type of current Model object in current View page. Next, CreateTextBox method will receive type from Form method and I can bind textbox to some property of this model. Update 1 The following code is code of CreateTextBox method that will create instance of TextBox class. public static CreateTextBox(string value, Expression<Func<object>> bindedProperty) { // T should be receive from HTML.Form method or class return new TextBox<T>(value); } Is it possible to creating some code that doing something like the above code? Thanks,

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  • How can I find out how much memory an instance of a C++ class consumes?

    - by Shadow
    Hi, I am developing a Graph-class, based on boost-graph-library. A Graph-object contains a boost-graph, so to say an adjacency_list, and a map. When monitoring the total memory usage of my program, it consumes quite a lot (checked with pmap). Now, I would like to know, how much of the memory is exactly consumed by a filled object of this Graph-class? With filled I mean when the adjacency_list is full of vertices and edges. I found out, that using sizeof() doesn't bring me far. Using valgrind is also not an alternative as there is quite some memory allocation done previously and this makes the usage of valgrind impractical for this purpose. I'm also not interested in what other parts of the program cost in memory, I want to focus on one single object. Thank you.

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  • How can I find out how much memory an object of a C++ class consumes?

    - by Shadow
    Hi, I am developing a Graph-class, based on boost-graph-library. A Graph-object contains a boost-graph, so to say an adjacency_list, and a map. When monitoring the total memory usage of my program, it consumes quite a lot (checked with pmap). Now, I would like to know, how much of the memory is exactly consumed by a filled object of this Graph-class? With filled I mean when the adjacency_list is full of vertices and edges. I found out, that using sizeof() doesn't bring me far. Using valgrind is also not an alternative as there is quite some memory allocation done previously and this makes the usage of valgrind impractical for this purpose. I'm also not interested in what other parts of the program cost in memory, I want to focus on one single object. Thank you.

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  • how to call a php class function directly using ajax?

    - by payling
    Is it possible to call a php class function DIRECTLY using ajax? Something like below... except ajax... myclass::myfunction(); I've been using the jquery library to work with AJAX. $.get('control.php', {func: funcName, arg1: arg1}); The above is similar to what I'm trying to achieve MINUS the control.php; I'm not sure if this is even possible, but I just thought it would be nice to skip the landing page (control.php) that recieves the funcName. I have a bunch of conditional statements that sort out what class function to run based on the funcName recieved. It seems kind of silly to do this, to have a separate page just to handle function calls. Is there a better way?

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  • MultiThreading question

    - by TiGer
    Hi, I am developing on Android but the question might be just as valid on any other Java platform. I have developed a multi-threaded app. Lets say I have a first class that needs to do a time-intensive task, thus this work is done in another Thread. When it's done that same Thread will return the time-intensive task result to another (3rd) class. This last class will do something and return it's result to the first-starting class. I have noticed though that the first class will be waiting the whole time, maybe because this is some kind of loop ? Also I'd like the Thread-class to stop itself, as in when it has passed it's result to the third class it should simply stop. The third class has to do it's work without being "incapsulated" in the second class (the Thread one). Anyone knows how to accomplish this ? right now the experience is that the first one seems to be waiting (hanging) till the second and the third one are done :(

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  • Java: Is it possible to have a generic class that only takes types that can be compared?

    - by mr popo
    I wanted to do something along the lines of: public class MyClass<T implements Comparable> { .... } But I can't, since, apparently, generics only accept restrictions with subclasses, and not interfaces. It's important that I'm able to compare the types inside the class, so how should I go about doing this? Ideally I'd be able to keep the type safety of Generics and not have to convert the T's to Object as well, or just not write a lot of code overall. In other words, the simplest the better.

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  • Unit Testing Example, on a class with required fields?

    - by Mastro
    I'm new to developing Unit test and I can't find an example of how to test an existing class I have. The class has a save method which does an insert or update in the database when the user clicks Save in the UI. But the save method has required fields that need to be populated. And has other fields that do not. So how can I run this test properly? Was trying to write it out.. Give a user When user saves object Then Field1 is required then Field2 is required Then Field3 is required WhenUserSavesObject() object = new object object.field1 IsNot Nothing something like that right? And what about the other fields that are optional? How would I test the save method to make sure it takes all those values properly? Was trying to use BDD but not sure if I should try it or not. Can't find any example of classes with many properties that are needed when calling a test method.

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  • C#: How to unit test a method that relies on another method within the same class?

    - by michael paul
    I have a class similar to the following: public class MyProxy : ClientBase<IService>, IService { public MyProxy(String endpointConfiguration) : base(endpointConfiguration) { } public int DoSomething(int x) { int result = DoSomethingToX(x); //This passes unit testing int result2 = ((IService)this).DoWork(x) //do I have to extract this part into a separate method just //to test it even though it's only a couple of lines? //Do something on result2 int result3 = result2 ... return result3; } int IService.DoWork(int x) { return base.Channel.DoWork(x); } } The problem lies in the fact that when testing I don't know how to mock the result2 item without extracting the part that gets result3 using result2 into a separate method. And, because it is unit testing I don't want to go that deep as to test what result2 comes back as... I'd rather mock the data somehow... like, be able to call the function and replace just that one call.

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  • How to call method written in C# class library from Silverlight application(xaml.cs file) ?

    - by Shyju
    Can a Silverlight application call a method in a full .NET c# class library? I am trying to add a Silverlight control to my Existing ASP.NET project where i used to add reference to my Business Logic Project and access methods from My UI pages of ASP.NET Web application. Now I have added one Silverlight project to my solution. How can I use the already existing BL method which is in a C# class library ? When tried to add reference, it is saying that "You can only add project reference to other silver light projects in the solution". Should i give up ? Is there any way to get rid of this ?

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  • jQuery selector to target any CSS name (of multiple present) starting with a prefix?

    - by John K
    I'm considering one selection statement that would target one of many css class names in a single class attribute value based on a string prefix. For example, I want any detail- prefixed class names to get targeted from the following sample links. <a href="eg.html" class="detail-1 pinkify another"> <a href="eg.html" class="something detail-55 minded"> <a href="eg.html" class="swing narrow detail-Z"> <a href="eg.html" class="swing narrow detail-Z detail-88 detail-A"> It's reminiscent of how [class|="detail"] prefix selector works on a scalar attribute value, and also of .hasClass(className), but my question needs both concepts applied simultaneously. Note: The detail- prefix won't necessarily be the first class name of the bunch.

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  • Sliding doors radio button, how to enable click / checked?

    - by Plexus81
    How to enable radio button click on a button with 3 pictures? http://jsfiddle.net/eeda6/8/ <div class="newsRadioButtons"> <div class="radioAll"> <div class="radioAllLeft"></div> <div class="radioAllMiddle"> <imput type="radio" checked="true" value="all" name="filter" />ALL </div> <div class="radioAllRight"></div> </div> <div class="radioImportant"> <div class="radioImportantLeft"></div> <div class="radioImportantMiddle"> <imput type="radio" checked="true" value="all" name="filter" />Important </div> <div class="radioImportantRight"></div> </div> ??? Sorry for the typo error

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  • How to select first empty value option in a select menu??

    - by alex
    Hi there, The following always preselects the last option, but i like the first option to be preselected? <select name="filter"> <option value="" selected>Make a choice</option> <option value="1">1</option> <option value="3">3</option> <option value="7">7</option> <option value="">all</option> </select> even with the first selected?? Can this be done??

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  • Why do C# and Java require everything to be in a class?

    - by Javier Badia
    It seemed like this question should have been asked before, but searching found nothing. I've always wondered what's the point of making us put every bit of code inside a class or interface. I seem to remember that there were some advantages to requiring a main() function like C, but nothing for classes. Languages like Python are, in a way, even more object oriented than Java since they don't have primitives, but you can put code wherever you want. Is this some sort of "misinterpretation" of OOP? After all, you can write procedural code like you would in C and put it inside a class, but it won't be object oriented.

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