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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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  • WCF: What happens if a channel is established but no method is called?

    - by mafutrct
    In my specific case: A WCF connection is established, but the only method with "IsInitiating=true" (the login method) is never called. What happens? In case the connection is closed due to inactivity after some time: Which setting configures this timeout? Is there still a way for a client to keep the connection alive? Reason for this question: I'm considering the above case as a possible security hole. Imagine many clients connecting to a server without logging in thus preventing other clients from connecting due to bandwidth problems or port shortage or lack of processing power or ... Am I dreaming, or is this an actual issue?

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  • Is it possible to use Data Annotations to validate parameters passed to an Action method of a Contro

    - by dannie.f
    I am using Data Annotations to validate my Model in ASP.NET MVC. This works well for action methods that has complex parameters e.g, public class Params { [Required] string Param1 {get; set;} [StringLength(50)] string Param2 {get; set;} } ActionResult MyAction(Params params) { If(ModeState.IsValid) { // Do Something } } What if I want to pass a single string to an Action Method (like below). Is there a way to use Data Annotations or will I have to wrap the string into a class? ActionResult MyAction(string param1, string param2) { If(ModeState.IsValid) { // Do Something } }

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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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  • In Python, is there a way to call a method on every item of an iterable? [closed]

    - by Thane Brimhall
    Possible Duplicate: Is there a map without result in python? I often come to a situation in my programs when I want to quickly/efficiently call an in-place method on each of the items contained by an iterable. (Quickly meaning the overhead of a for loop is unacceptable). A good example would be a list of sprites when I want to call draw() on each of the Sprite objects. I know I can do something like this: [sprite.draw() for sprite in sprite_list] But I feel like the list comprehension is misused since I'm not using the returned list. The same goes for the map function. Stone me for premature optimization, but I also don't want the overhead of the return value. What I want to know is if there's a method in Python that lets me do what I just explained, perhaps like the hypothetical function I suggest below: do_all(sprite_list, draw)

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  • How to create a generic C# method that can return either double or decimal?

    - by CrimsonX
    I have a method like this: private static double ComputePercentage(ushort level, ushort capacity) { double percentage; if(capacity == 1) percentage = 1; // do calculations... return percentage; } Is it possible to make it of a generic type like "type T" where it can return either decimal or double, depending on the type of method expected (or the type put into the function?) I tried something like this and I couldn't get it to work, because I cannot assign a number like "1" to a generic type. I also tried using the "where T :" after ushort capacity) but I still couldn't figure it out. private static T ComputePercentage<T>(ushort level, ushort capacity) { T percentage; if(capacity == 1) percentage = 1; // error here // do calculations... return percentage; } Is this even possible? I wasn't sure, but I thought this post might suggest that what I'm trying to do is just plain impossible.

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  • Can I add a custom method to Core Data-generated classes?

    - by Andy
    I've got a couple of Core Data-generated class files that I'd like to add custom methods to. I don't need to add any instance variables. How can I do this? I tried adding a category of methods: // ContactMethods.h (my category on Core Data-generated "Contact" class) #import "Contact.h" @interface Contact (ContactMethods) -(NSString*)displayName; @end ... // ContactMethods.m #import "ContactMethods.h" @implementation Contact (ContactMethods) -(NSString*)displayName { return @"Some Name"; // this is test code } @end This doesn't work, though. I get a compiler message that "-NSManagedObject may not respond to 'displayName' " and sure enough, when I run the app, I don't get "Some Name" where I should be seeing it.

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  • How to pass a file (read from Java) most effectively to a native method?

    - by soc
    Hi, I have approx. 30000 files (1MB each) which I want to put into a native method, which requires just an byte array and the size of it as arguments. I looked through some examples and benchmarks (like http://nadeausoftware.com/articles/2008/02/java_tip_how_read_files_quickly) but all of them do some other fancy things. Basically I don't care about the contents of the file, I don't want to access something in that file or the byte array or do anything else with it. I just want to put a file into a native method which accepts an byte array as fast as possible. At the moment I'm using RandomAccessFile, but that's horribly slow (10MB/s). Is there anything like byte[] readTheWholeFile(File file){ ... } which I could put into native void fancyCMethod(readTheWholeFile(myFile), myFile.length()) What would you suggest?

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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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  • 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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  • How is push()ing and pop()ping defined?

    - by Helper Method
    I know how the push() and pop() methods in a typical implementation of a Queue/Linked List work but what I do want to know is what you actually define as a push or a pop? When can you name a method push()/pop()? What makes the insert()/add() method in a typical Tree implementation not a push()? My understanding is that push()ing means putting something to a position some special pointer is pointing to, and pop()ping an element means putting some object away some pointer is pointing to, but it doesn't seem to be clearly defined. Or does the naming matter at all?

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  • I can get access to object's properties if method is called from anonymous function, but I can't do

    - by Kirzilla
    Hello, $.Comment = function() { this.alertme = "Alert!"; } $.Comment.prototype.send = function() { var self = this; $.post( self.url, { 'somedata' : self.somedata }, function(data) { //using anonymous function to call object's method self.callback(data); } ); } $.Comment.prototype.callback = function(data) { alert(this.alertme); } This code works great when I'm calling $.Comment.send(), but this code won't work... $.Comment.prototype.send = function() { var self = this; $.post( self.url, { 'somedata' : self.somedata }, self.callback //using direct access to method ); } Please, could you explain me why? Thank you

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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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  • What is the purpose of Process class in Java?

    - by Nitesh Panchal
    Runtime objRuntime = Runtime.getRuntime(); String strBackupString = "mysqldump -u " + userName + " -p" + password + " " + dbName; Process objProcess = objRuntime.exec(strBackupString); This is used for backup of database. But what exactly happens? Can anybody make me explain, what is the purpose of Runtime and Process class? Is this class used to act as if we are typing command from command prompt? Then what should i pass to objRuntime.exec() if i want to open notepad? And is the command executed as soon as we call exec method? If yes, then what purpose does Process serve here? I really can't understand these two classes. Please make me understand. Thanks in advance :)

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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 to use AOP to intercept a method call in super on an argument?

    - by hleinone
    I'm extending a class and overriding a method. All I want to do is to call super, but with a modified argument that gets intercepted upon one of its methods is called. An example makes it more clear: // Foo is an interface and also this method is part of an interface @Override public void foo(Foo foo) { // I want to intercept the call to foo.bar() in super super.foo(foo); } I'd rather use a tool that doesn't require a compiler of its own. What would be the optimal one?

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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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  • Delphi 2010 - Why can't I declare an abstract method with a generic type parameter?

    - by James
    I am trying to do the following in Delphi 2010: TDataConverter = class abstract public function Convert<T>(const AData: T): string; virtual; abstract; end; However, I keep getting the following compiler error: E2533 Virtual, dynamic and message methods cannot have type parameters I don't quite understand the reason why I can't do this. I can do this in C# e.g. public abstract class DataConverter { public abstract string Convert<T>(T data); } Anyone know the reasoning behind this?

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  • Objective-C inheritance; calling overriden method from superclass?

    - by anshuchimala
    Hello, I have an Objective-C class that has a method that is meant to be overridden, which is uses in a different method. Something like this: @interface BaseClass - (id)overrideMe; - (void)doAwesomeThings; @end @implementation BaseClass - (id)overrideMe { [self doesNotRecognizeSelector:_cmd]; return nil; } - (void)doAwesomeThings { id stuff = [self overrideMe]; /* do stuff */ } @end @interface SubClass : BaseClass @end @implementation SubClass - (id)overrideMe { /* Actually do things */ return <something>; } @end However, when I create a SubClass and try to use it, it still calls overrideMe on the BaseClass and crashes due to doesNotRecognizeSelector:. (I'm not doing a [super overrideMe] or anything stupid like that). Is there a way to get BaseClass to call the overridden overrideMe?

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  • How can I change this method to get rid of the warning without anything changing?

    - by user3591323
    So this question:Warning-used as the name of the previous parameter rather than as part of the selector answers part of my problem, but I really don't want anything to change inside this method and I'm a bit confused on how this works. Here's the whole method: -(void) SetRightWrong:(sqzWord *)word: (int) rightWrong { if (self.mastered==nil) { self.mastered = [[NSMutableArray alloc]initWithCapacity:10]; } //if right change number right if (rightWrong == 1) { word.numberCorrect++; //if 3 right move to masterd list [self.onDeck removeObject:word]; if(word.numberCorrect >= 3 ) { [self.mastered addObject:word]; } else { //if not 3 right move to end of ondeck [self.onDeck addObject:word]; } } else if(rightWrong == 0) { //if wrong remove one from number right unless 0 NSUInteger i; i=[self.onDeck indexOfObject:word]; word = [self.onDeck objectAtIndex:i]; if (word.numberCorrect >0) { word.numberCorrect--; } } } The warning I am getting is: 'word' used as the name of the previous parameter than as part of the selector.

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  • LINQ to SQL, how to write a method which checks if a row exists when we have multiple tables

    - by Beles
    Hi, I'm trying to write a method in C# which can take as parameter a tabletype, column and a columnvalue and check if the got a row with a with value the method looks like: public object GetRecordFromDatabase(Type tabletype, string columnname, string columnvalue) I'm using LINQ to SQL and need to to this in a generic way so I don't need to write each table I got in the DB. I have been doing this so far for each table, but with more than 70 of these it becomes cumbersome and boring to do. Is there a way to generate the following code dynamically, And swap out the hardcoded tablenames with the values from the parameterlist? In this example I have a table in the DB named tbl_nation, which the DataContext pluralizes to tbl_nations, and I'm checking the column for the value if (DB.tbl_nations.Count(c => c.code.Equals(columnvalue)) == 1) { return DB.tbl_nations.Single(c => c.code.Equals(columnvalue)); }

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