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  • How would you code an efficient Circular Buffer in Java or C#

    - by Cheeso
    I want a simple class that implements a fixed-size circular buffer. It should be efficient, easy on the eyes, generically typed. EDIT: It need not be MT-capable, for now. I can always add a lock later, it won't be high-concurrency in any case. Methods should be: .Add and I guess .List, where I retrieve all the entries. On second thought, Retrieval I think should be done via an indexer. At any moment I will want to be able to retrieve any element in the buffer by index. But keep in mind that from one moment to the next Element[n] may be different, as the Circular buffer fills up and rolls over. This isn't a stack, it's a circular buffer. Regarding "overflow": I would expect internally there would be an array holding the items, and over time the head and tail of the buffer will rotate around that fixed array. But that should be invisible from the user. There should be no externally-detectable "overflow" event or behavior. This is not a school assignment - it is most commonly going to be used for a MRU cache or a fixed-size transaction or event log.

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  • What does it mean to pass a &variable to a function? E.g., string& insert ( size_t pos1, const strin

    - by Bob Montgomery
    I understand passing a pointer, and returning a pointer: char * strcat ( char * destination, const char * source ); You're passing a variable that contains the address to a char; returning the same. But what does it mean to pass something using the reference operator? Or to return it? string& insert ( size_t pos1, const string& str ); I mean, I understand what actually happens, I just don't understand the notation. Why isn't the notation this instead: string * insert ( size_t pos1, const string * str ); //made up I presume it has something to do with passing/returning the instance of a class, but what? Is this syntax valid; if not why not and if so what does it mean? char & strcat ( char & destination, const char & source ); //made up (all of the function declarations, except the last made-up two, are from http://www.cplusplus.com )

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  • How to add a class to just upper element of trigger with Jquery?

    - by Ahmet Kemal
    Hello, I am working on a Jquery accordion stuff. I want to add a class to the div that contains the accordion trigger <a> tag. You can look at my code. I want to add "first" class name to just first "newsitems" class when clicked "Recession fashion in Japan Video" title. <!-- news items starts--> <div class="newsitems"> <h3 class="business"> <a href="#" title="expand"><img src="images/expand_icon.gif" alt="collapse" class="collpase" /> Recession fashion in Japan Video</a> </h3> <p class="timestamp">0100hrs</p> </div> <!-- news items ends--> <!-- news items starts--> <div class="newsitems"> <h3 class="sports"> <a href="#" title="expand"><img src="images/expand_icon.gif" alt="collapse" class="collpase" /> Murray survives five-set thriller at Wimbledon</a> </h3> <p class="timestamp">0100hrs</p> </div> <!-- news items ends-->

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  • [C++] A minimalistic smart array (container) class template

    - by legends2k
    I've written a (array) container class template (lets call it smart array) for using it in the BREW platform (which doesn't allow many C++ constructs like STD library, exceptions, etc. It has a very minimal C++ runtime support); while writing this my friend said that something like this already exists in Boost called MultiArray, I tried it but the ARM compiler (RVCT) cries with 100s of errors. I've not seen Boost.MultiArray's source, I've just started learning template only lately; template meta programming interests me a lot, although am not sure if this is strictly one, which can be categorised thus. So I want all my fellow C++ aficionados to review it ~ point out flaws, potential bugs, suggestions, optimisations, etc.; somthing like "you've not written your own Big Three which might lead to...". Possibly any criticism that'll help me improve this class and thereby my C++ skills. smart_array.h #include <vector> using std::vector; template <typename T, size_t N> class smart_array { vector < smart_array<T, N - 1> > vec; public: explicit smart_array(vector <size_t> &dimensions) { assert(N == dimensions.size()); vector <size_t>::iterator it = ++dimensions.begin(); vector <size_t> dimensions_remaining(it, dimensions.end()); smart_array <T, N - 1> temp_smart_array(dimensions_remaining); vec.assign(dimensions[0], temp_smart_array); } explicit smart_array(size_t dimension_1 = 1, ...) { static_assert(N > 0, "Error: smart_array expects 1 or more dimension(s)"); assert(dimension_1 > 1); va_list dim_list; vector <size_t> dimensions_remaining(N - 1); va_start(dim_list, dimension_1); for(size_t i = 0; i < N - 1; ++i) { size_t dimension_n = va_arg(dim_list, size_t); assert(dimension_n > 0); dimensions_remaining[i] = dimension_n; } va_end(dim_list); smart_array <T, N - 1> temp_smart_array(dimensions_remaining); vec.assign(dimension_1, temp_smart_array); } smart_array<T, N - 1>& operator[](size_t index) { assert(index < vec.size() && index >= 0); return vec[index]; } size_t length() const { return vec.size(); } }; template<typename T> class smart_array<T, 1> { vector <T> vec; public: explicit smart_array(vector <size_t> &dimension) : vec(dimension[0]) { assert(dimension[0] > 0); } explicit smart_array(size_t dimension_1 = 1) : vec(dimension_1) { assert(dimension_1 > 0); } T& operator[](size_t index) { assert(index < vec.size() && index >= 0); return vec[index]; } size_t length() { return vec.size(); } }; Sample Usage: #include <iostream> using std::cout; using std::endl; int main() { // testing 1 dimension smart_array <int, 1> x(3); x[0] = 0, x[1] = 1, x[2] = 2; cout << "x.length(): " << x.length() << endl; // testing 2 dimensions smart_array <float, 2> y(2, 3); y[0][0] = y[0][1] = y[0][2] = 0; y[1][0] = y[1][1] = y[1][2] = 1; cout << "y.length(): " << y.length() << endl; cout << "y[0].length(): " << y[0].length() << endl; // testing 3 dimensions smart_array <char, 3> z(2, 4, 5); cout << "z.length(): " << z.length() << endl; cout << "z[0].length(): " << z[0].length() << endl; cout << "z[0][0].length(): " << z[0][0].length() << endl; z[0][0][4] = 'c'; cout << z[0][0][4] << endl; // testing 4 dimensions smart_array <bool, 4> r(2, 3, 4, 5); cout << "z.length(): " << r.length() << endl; cout << "z[0].length(): " << r[0].length() << endl; cout << "z[0][0].length(): " << r[0][0].length() << endl; cout << "z[0][0][0].length(): " << r[0][0][0].length() << endl; // testing copy constructor smart_array <float, 2> copy_y(y); cout << "copy_y.length(): " << copy_y.length() << endl; cout << "copy_x[0].length(): " << copy_y[0].length() << endl; cout << copy_y[0][0] << "\t" << copy_y[1][0] << "\t" << copy_y[0][1] << "\t" << copy_y[1][1] << "\t" << copy_y[0][2] << "\t" << copy_y[1][2] << endl; return 0; }

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  • Domain validates but won't save

    - by marko
    I have the following setup. Class, say, Car that has a CarPart (belongsTo=[car:Car]). When I'm creating a Car I also want to create som default CarParts, so I do def car = new Car(bla bla bla) def part = new CarPart(car:car) Now, when I do car.validate() or part.validate() it seems fine. But when I do if(car.save && part.save() I get this exception: 2012-03-24 14:02:21,943 [http-8080-4] ERROR util.JDBCExceptionReporter - Batch entry 0 insert into car_part (version, car_id, id) values ('0', '297', '298') was aborted. Call getNextException to see the cause. 2012-03-24 14:02:21,943 [http-8080-4] ERROR util.JDBCExceptionReporter - ERROR: value too long for type character varying(6) 2012-03-24 14:02:21,943 [http-8080-4] ERROR events.PatchedDefaultFlushEventListener - Could not synchronize database state with session org.hibernate.exception.DataException: Could not execute JDBC batch update Stacktrace follows: java.sql.BatchUpdateException: Batch entry 0 insert into car_part (version, deal_id, id) values ('0', '297', '298') was aborted. Call getNextException to see the cause. at org.postgresql.jdbc2.AbstractJdbc2Statement$BatchResultHandler.handleError(AbstractJdbc2Statement.java:2621) at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1837) at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:407) at org.postgresql.jdbc2.AbstractJdbc2Statement.executeBatch(AbstractJdbc2Statement.java:2754) at $Proxy20.flush(Unknown Source) at ristretto.DealController$_closure5.doCall(DealController.groovy:109) at ristretto.DealController$_closure5.doCall(DealController.groovy) at java.lang.Thread.run(Thread.java:722) Any ideas?

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  • Learning OOP in PHP, trying to refactor my code. Can't connect to database anymore.

    - by Cortopasta
    Thought I understood how classes work, then I tried this code: class user { var $dbcon; var $dbinfo; var $con; var $error; function dbConnect() { $this->dbinfo['server'] = "localhost"; $this->dbinfo['database'] = "foolish_faith"; $this->dbinfo['user'] = "user"; $this->dbinfo['password'] = "password"; $this->con = "mysql:host=".$dbinfo['server']."; dbname=".$dbinfo['database']; $this->dbcon = new PDO($con, $dbinfo['user'], $dbinfo['password']); $this->dbcon->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); $this->error = $this->dbcon->errorInfo(); if ($error[0] != "") { print "Error!"; print_r($error); } } } Now it just spits out this error: Fatal error: Uncaught exception 'PDOException' with message 'invalid data source name' in E:\PortableApps\xampp\htdocs\dbcon.php:24 Stack trace: #0 E:\PortableApps\xampp\htdocs\dbcon.php(24): PDO-__construct('', NULL, NULL) #1 E:\PortableApps\xampp\htdocs\login.php(4): user-dbConnect() #2 {main} thrown in E:\PortableApps\xampp\htdocs\dbcon.php on line 24 Can anybody see what I'm doing wrong, as I'm sure it has to do with my lack of knowledge when it comes to classes?

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  • Java Matrix Transpose strangeness going on

    - by user1459976
    ok so im making my own Matrix class. and i have a transpose method that transposes a matrix. this is the block in the main method Matrix m1 = new Matrix(4,2); m1.fillMatrix(1,2,3,4,5,6,7,8); System.out.println("before " + m1.toString()); m1.transpose(); System.out.println("after " + m1.toString()); this is where it gets messed up, at m1.transpose(); in the transpose() method public Matrix transpose() { if(isMatrix2) { Matrix tempMatrix = new Matrix(row, col); // matrix2 contents are emptied once this line is executed for(int i=0; i < row; i++) { for(int j=0; j < col; j++) tempMatrix.matrix2[i][j] = matrix2[i][j]; } so for some reason, the tempMatrix.matrix2 has the same id as this.matrix2. so when the codes executes Matrix tempMatrix = new Matrix(row,col); then the contents of this.matrix2 is emptied. anyone know what might be going on here?

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  • Python OOP - object has no attribute

    - by user1744269
    I am attempting to learn how to program. I really do want to learn how to program; I love the building and design aspect of it. However, in Java and Python, I have tried and failed with programs as they pertain to objects, classes, methods.. I am trying to develop some code for a program, but im stumped. I know this is a simple error. However I am lost! I am hoping someone can guide me to a working program, but also help me learn (criticism is not only expected, but APPRECIATED). class Converter: def cTOf(self, numFrom): numFrom = self.numFrom numTo = (self.numFrom * (9/5)) + 32 print (str(numTo) + ' degrees Farenheit') return numTo def fTOc(self, numFrom): numFrom = self.numFrom numTo = ((numFrom - 32) * (5/9)) return numTo convert = Converter() numFrom = (float(input('Enter a number to convert.. '))) unitFrom = input('What unit would you like to convert from.. ') unitTo = input('What unit would you like to convert to.. ') if unitFrom == ('celcius'): convert.cTOf(numFrom) print(numTo) input('Please hit enter..') if unitFrom == ('farenheit'): convert.fTOc(numFrom) print(numTo) input('Please hit enter..')

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  • Is there a language or design pattern that allows the *removal* of object behavior or properties in a class hierarchy?

    - by Sebastien Diot
    A well-know shortcoming of traditional class hierarchies is that they are bad when it comes to model the real world. As an example, trying to represent animals species with classes. There are actually several problems when doing that, but one that I never saw a solution to is when a sub-class "looses" a behavior or properties that was defined in a super-class, like a penguin not being able to fly (there are probably better examples, but that's the first one that comes to my mind, having seen "Madagascar 2" recently). On the one hand, you don't want to define for every property and behavior some flag that specifies if it is at all present, and check it every time before accessing that behavior or property. You would just like to say that birds can fly, simply and clearly, in the Bird class. But then it would be nice if one could define "exceptions" afterward, without having to use some horrible hacks everywhere. This often happens when a system has been productive for a while. You suddenly find an "exception" that doesn't fit in the original design at all, and you don't want to change a large portion of your code to accommodate it. So, is there some language or design patterns that can cleanly handle this problem, without requiring major changes to the "super-class", and all the code that uses it? Even if a solution only handle a specific case, several solutions might together form a complete strategy. [EDIT] Forgot about the Liskov Substitution Principle. That is why you can't do it. Assuming you define "traits/interfaces" for all major "feature groups", you can freely implement traits in different branches of the hierarchy, like the Flying trait could be implemented by Birds, and some special kind of squirrels and fish. So my question could amount to "How could I un-implement a trait?" If your super-class is a Java Serializable, you have to be one too, even if there is no way for you to serialize your state, for example if you contained a "Socket". So one way to do it is to always define all your traits in pair from the start: Flying and NotFlying (which would throw UnsupportedOperationExceiption, if not checked against). The Not-trait would not define any new interface, and could be simply checked for. Sounds like a "cheap" solution, in particular if used from the start.

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  • Is it better to load up a class with methods or extend member functionality in a local subclass?

    - by Calvin Fisher
    Which is better? Class #1: public class SearchClass { public SearchClass (string ProgramName) { /* Searches LocalFile objects, handles exceptions, and puts results into m_Results. */ } DateTime TimeExecuted; bool OperationSuccessful; protected List<LocalFile> m_Results; public ReadOnlyCollection<LocalFile> Results { get { return new ReadOnlyCollection<LocalFile>(m_Results); } } #region Results Filters public DateTime OldestFileModified { get { /* Does what it says. */ } } public ReadOnlyCollection<LocalFile> ResultsWithoutProcessFiles() { return new ReadOnlyCollection<LocalFile> ((from x in m_Results where x.FileTypeID != FileTypeIDs.ProcessFile select x).ToList()); } #endregion } Or class #2: public class SearchClass { public SearchClass (string ProgramName) { /* Searches LocalFile objects, handles exceptions, and puts results into m_Results. */ } DateTime TimeExecuted; bool OperationSuccessful; protected List<LocalFile> m_Results; public ReadOnlyCollection<LocalFile> Results { get { return new ReadOnlyCollection<LocalFile>(m_Results); } } public class SearchResults : ReadOnlyCollection<LocalFile> { public SearchResults(IList<LocalFile> iList) : base(iList) { } #region Results Filters public DateTime OldestFileModified { get { /* Does what it says. */ } } public ReadOnlyCollection<LocalFile> ResultsWithoutProcessFiles() { return new ReadOnlyCollection<LocalFile> ((from x in this where x.FileTypeID != FileTypeIDs.ProcessFile select x).ToList()); } #endregion } } ...with the implication that OperationSuccessful is accompanied by a number of more interesting properties on how the operation went, and OldestFileModified and ResultsWithoutProcessFiles() also have several more siblings in the Results Filters section.

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  • SceneManagers as systems in entity system or as a core class used by a system?

    - by Hatoru Hansou
    It seems entity systems are really popular here. Links posted by other users convinced me of the power of such system and I decided to try it. (Well, that and my original code getting messy) In my project, I originally had a SceneManager class that maintained needed logic and structures to organize the scene (QuadTree, 2D game). Before rendering I call selectRect() and pass the x,y of the camera and the width and height of the screen and then obtain a minimized list containing only visible entities ordered from back to front. Now with Systems, originally in my first attempt my Render system required to get added all entities it should handle. This may sound like the correct approach but I realized this was not efficient. Trying to optimize It I reused the SceneManager class internally in the Renderer system, but then I realized I needed methods such as selectRect() in others systems too (AI principally) and make the SceneManager accessible globally again. Currently I converted SceneManager to a system, and ended up with the following interface (only relevant methods): /// Base system interface class System { public: virtual void tick (double delta_time) = 0; // (methods to add and remove entities) }; typedef std::vector<Entity*> EntitiesVector; /// Specialized system interface to allow query the scene class SceneManager: public System { public: virtual EntitiesVector& cull () = 0; /// Sets the entity to be used as the camera and replaces previous ones. virtual void setCamera (Entity* entity) = 0; }; class SceneRenderer // Not a system { vitual void render (EntitiesVector& entities) = 0; }; Also I could not guess how to convert renderers to systems. My game separates logic updates from screen updates, my main class have a tick() method and a render() method that may not be called the same times. In my first attempt renderers were systems but they was saved in a separated manager, updated only in render() and not in tick() like all other systems. I realized that was silly and simply created a SceneRenderer interface and give up about converting them to systems, but that may be for another question. Then... something does not feel right, isn't it? If I understood correctly a system should not depend on another or even count with another system exposing an specific interface. Each system should care only about its entities, or nodes (as optimization, so they have direct references to relevant components without having to constantly call the component() or getComponent() method of the entity).

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  • what does composition example vs aggregation

    - by meWantToLearn
    Composition and aggregation both are confusion to me. Does my code sample below indicate composition or aggregation? class A { public static function getData($id) { //something } public static function checkUrl($url) { // something } class B { public function executePatch() { $data = A::getData(12); } public function readUrl() { $url = A::checkUrl('http/erere.com'); } public function storeData() { //something not related to class A at all } } } Is class B a composition of class A or is it aggregation of class A? Does composition purely mean that if class A gets deleted class B does not works at all and aggregation if class A gets deleted methods in class B that do not use class A will work?

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  • How to import or "using" a custom class in Unity script?

    - by Bobbake4
    I have downloaded the JSONObject plugin for parsing JSON in Unity but when I use it in a script I get an error indicating JSONObject cannot be found. My question is how do I use a custom object class defined inside another class. I know I need a using directive to solve this but I am not sure of the path to these custom objects I have imported. They are in the root project folder inside JSONObject folder and class is called JSONObject. Thanks

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  • Why use sealed instead of static on a class?

    - by sq33G
    Our system has several utility classes. Some people on our team use (A) a class with all-static methods and a private constructor. Others use (B) a class with all-static methods (these the juniors). On code analysis, (A) and (B) raise warning CA1052, which recommends marking the class as sealed. Included in the MSDN documentation there is the following advice: If you are targeting .NET Framework 2.0 or earlier, a better approach is to mark the type as static. Why does this make any sense? I would have thought the opposite; AFAIK, previous to 2.0 there was no way to mark a class as static.

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  • Declaring interface in the same file as the base class, is it a good practice?

    - by Louis Rhys
    To be interchangable and testable, normally services with logic needs to have interface, e.g. public class FooService: IFooService { ... } Design-wise, I agree with this, but one of the things that bothers me with this approach is that for one service you will need to declare two things (the class and the interface), and in our team, normally two files (one for the class and one for the interface). Another discomfort is the difficulty in navigation because using "Go to definition" in IDE (VS2010) will point to the interface (since other classes refer to the interface), not the actual class. I was thinking that writing IFooService in the same file as FooService will reduce the above weirdness. After all, IFooService and FooService are very related. Is this a good practice? Is there a good reason that IFooService must be located in its own file?

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  • Is there a class or id that will cause an ad to be blocked by most major adblockers?

    - by Moak
    Is there a general class or ID for a html element that a high majority of popular adblockers will block on a website it has no information for. My intention is to have my advertisement blocked, avoiding automatic blocking is easy enough... I was thinking of maybe lending some ids or classes from big advertisment companies that area already being fought off quite actively. right now my html <ul id=partners> <li class=advertisment><a href=# class=sponsor><img class=banner></a></li> </ul> Will this work or is there a more solid approach?

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  • What is the disadvantage of using abstract class as a database connectivity in zend framework 2 instead of service locator

    - by arslaan ejaz
    If I use database by creating adapter with drivers, initialize it in some abstract class and extend that abstract class to required model. Then use simple query statement. Like this: namespace My-Model\Model\DB; abstract class MysqliDB { protected $adapter; public function __construct(){ $this->adapter = new \Zend\Db\Adapter\Adapter(array( 'driver' => 'Mysqli', 'database' => 'my-database', 'username' => 'root', 'password' => '' )); } } And use abstract class of database like this in my models: class States extends DB\MysqliDB{ public function __construct(){ parent::__construct(); } protected $states = array(); public function select_all_states(){ $data = $this->adapter->query('select * from states'); foreach ($data->execute() as $row){ $this->states[] = $row; } return $this->states; } } I am new to zend framework, before i have experience of working in YII and Codeigniter. I like the object oriented in zend so i want to use it like this. And don't want to use it through service locater something like this: public function getServiceConfig(){ return array( 'factories' => array( 'addserver-mysqli' => new Model\MyAdapterFactory('addserver-mysqli'), 'loginDB' => function ($sm){ $adapter = $sm->get('addserver-mysqli'); return new LoginDB($adapter); } ) ); } In module. Am i Ok with this approach?

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  • What is a good design model for my new class?

    - by user66662
    I am a beginning programmer who, after trying to manage over 2000 lines of procedural php code, now has discovered the value of OOP. I have read a few books to get me up to speed on the beginning theory, but would like some advice on practical application. So,for example, let's say there are two types of content objects - an ad and a calendar event. what my application does is scan different websites (a predefined list), and, when it finds an ad or an event, it extracts the data and saves it to a database. All of my objects will share a $title and $description. However, the Ad object will have a $price and the Event object will have $startDate. Should I have two separate classes, one for each object? Should I have a 'superclass' with the $title and $description with two other Ad and Event classes with their own properties? The latter is at least the direction I am on now. My second question about this design is how to handle the logic that extracts the data for $title, $description, $price, and $date. For each website in my predefined list, there is a specific regex that returns the desired value for each property. Currently, I have an extremely large switch statement in my constructor which determines what website I am own, sets the regex variables accordingly, and continues on. Not only that, but now I have to repeat the logic to determine what site I am on in the constructor of each class. This doesn't feel right. Should I create another class Algorithms and store the logic there for each site? Should the functions of to handle that logic be in this class? or specific to the classes whos properties they set? I want to take into account in my design two things: 1) I will add different content objects in the future that share $title and $description, but will have their own properties, so, I want to be able to easily grow these as needed. 2) I will add more websites constantly (each with their own algorithms for data extraction) so I would like to plan efficienty managing and working with these now. I thought about extending the Ad or Event class with 'websiteX' class and store its functions there. But, this didn't feel right either as now I have to manage 100s of little website specific class files. Note, I didn't know if this was the correct site or stackoverflow was the better choice. If so, let me know and I'll post there.

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  • May I give a single class multiple responsibilities if only one will ever be reusable?

    - by lnluis
    To the extent that I understand the Single Responsibility Principle, a SINGLE class must only have one responsibility. We use this so that we can reuse other functionalities in other classes and not affect the whole class. My question is: what if the entity has only one purpose that really interacts with the system, and that purpose won't change? Do you have to separate the implementations of your methods into another class and just instantiate those from your entity class? Or to put it another way... Is it ok to break the SRP if you know those functions will not be reusable in the future? Or is it better to assume that we do not know if the functionalities of these methods will be reusable or not, and so just abstract them to other classes?

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  • should I create a new class for a specific piece of business logic?

    - by Riz
    I have a Request class based on the same Entity in my Domain. It currently only has property definitions. I'd like to add a method for checking a duplicate Request which I'll call from my controller. Should I add a method called CheckDuplicate in the Request class? Would I be violating the SRP? The method will need to access a database context to check already existing requests. I'm thinking creating another class altogether for this logic that accepts a datacontext as part of its constructor. But creating a whole new class for just one method seems like a waste too. Any advice?

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  • "Default approach" when creating a class from scratch: getters for everything, or limited access?

    - by Prog
    Until recently I always had getters (and sometimes setters but not always) for all the fields in my class. It was my 'default': very automatic and I never doubted it. However recently some discussions on this site made me realize maybe it's not the best approach. When you create a class, you often don't know exactly how it's going to be used in the future by other classes. So in that sense, it's good to have getters and setter for all of the fields in the class. So other classes could use it in the future any way they want. Allowing this flexibility doesn't require you to over engineer anything, only to provide getters. However some would say it's better to limit the access to a class, and only allow access to certain fields, while other fields stay completely private. What is your 'default' approach when building a class from scratch? Do you make getters for all the fields? Or do you always choose selectively which fields to expose through a getter and which to keep completely private?

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  • Trying to implement pre/post method code: better to use methods or a parent class?

    - by Will
    I'm finding it difficult to frame this question so ... I want to execute code both before and after a method runs in PHP. There are, as far as I know, two ways to implement this: Method One: pre and post methods class Model { function find($id) { $this->_precode(); // ... do stuff $this->post_code(); } } Add the calls to _precode() and _postcode() to each method where I need this functionality. Method Two: __call and method naming class Model extends PrePost { function prepost_find($id) { // ... do stuff ... } } class PrePost { function __call($method,$param) { $method = "prepost_$method"; // .. precode here .. $result = $this->$method($param); // .. postcode here .. } } This relies on naming a method in a specific way in the inheriting class. Is there a preferred way of doing this? The call method can be made to only handle its specific cases and even defer to a child class's call if there is one. I'm not looking for opinions; I'm looking to find out if there are valid reasons to choose one way over another.

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  • DexFile.class error in eclipse

    - by ninjasense
    I get this weird error everytime I debug in eclipse. It just seemed to appear one day and I was wondering if anyone else was running int the same problem. It does not affect my app in anyway visibly and does not cause a crash but it is an annoyance while debugging. Here is the full error: // Compiled from DexFile.java (version 1.5 : 49.0, super bit) public final class dalvik.system.DexFile { // Method descriptor #8 (Ljava/io/File;)V // Stack: 3, Locals: 2 public DexFile(java.io.File file) throws java.io.IOException; 0 aload_0 [this] 1 invokespecial java.lang.Object() [1] 4 new java.lang.RuntimeException [2] 7 dup 8 ldc <String "Stub!"> [3] 10 invokespecial java.lang.RuntimeException(java.lang.String) [4] 13 athrow Line numbers: [pc: 0, line: 4] Local variable table: [pc: 0, pc: 14] local: this index: 0 type: dalvik.system.DexFile [pc: 0, pc: 14] local: file index: 1 type: java.io.File // Method descriptor #18 (Ljava/lang/String;)V // Stack: 3, Locals: 2 public DexFile(java.lang.String fileName) throws java.io.IOException; 0 aload_0 [this] 1 invokespecial java.lang.Object() [1] 4 new java.lang.RuntimeException [2] 7 dup 8 ldc <String "Stub!"> [3] 10 invokespecial java.lang.RuntimeException(java.lang.String) [4] 13 athrow Line numbers: [pc: 0, line: 5] Local variable table: [pc: 0, pc: 14] local: this index: 0 type: dalvik.system.DexFile [pc: 0, pc: 14] local: fileName index: 1 type: java.lang.String // Method descriptor #22 (Ljava/lang/String;Ljava/lang/String;I)Ldalvik/system/DexFile; // Stack: 3, Locals: 3 public static dalvik.system.DexFile loadDex(java.lang.String sourcePathName, java.lang.String outputPathName, int flags) throws java.io.IOException; 0 new java.lang.RuntimeException [2] 3 dup 4 ldc <String "Stub!"> [3] 6 invokespecial java.lang.RuntimeException(java.lang.String) [4] 9 athrow Line numbers: [pc: 0, line: 6] Local variable table: [pc: 0, pc: 10] local: sourcePathName index: 0 type: java.lang.String [pc: 0, pc: 10] local: outputPathName index: 1 type: java.lang.String [pc: 0, pc: 10] local: flags index: 2 type: int // Method descriptor #28 ()Ljava/lang/String; // Stack: 3, Locals: 1 public java.lang.String getName(); 0 new java.lang.RuntimeException [2] 3 dup 4 ldc <String "Stub!"> [3] 6 invokespecial java.lang.RuntimeException(java.lang.String) [4] 9 athrow Line numbers: [pc: 0, line: 7] Local variable table: [pc: 0, pc: 10] local: this index: 0 type: dalvik.system.DexFile // Method descriptor #30 ()V // Stack: 3, Locals: 1 public void close() throws java.io.IOException; 0 new java.lang.RuntimeException [2] 3 dup 4 ldc <String "Stub!"> [3] 6 invokespecial java.lang.RuntimeException(java.lang.String) [4] 9 athrow Line numbers: [pc: 0, line: 8] Local variable table: [pc: 0, pc: 10] local: this index: 0 type: dalvik.system.DexFile // Method descriptor #32 (Ljava/lang/String;Ljava/lang/ClassLoader;)Ljava/lang/Class; // Stack: 3, Locals: 3 public java.lang.Class loadClass(java.lang.String name, java.lang.ClassLoader loader); 0 new java.lang.RuntimeException [2] 3 dup 4 ldc <String "Stub!"> [3] 6 invokespecial java.lang.RuntimeException(java.lang.String) [4] 9 athrow Line numbers: [pc: 0, line: 9] Local variable table: [pc: 0, pc: 10] local: this index: 0 type: dalvik.system.DexFile [pc: 0, pc: 10] local: name index: 1 type: java.lang.String [pc: 0, pc: 10] local: loader index: 2 type: java.lang.ClassLoader // Method descriptor #37 ()Ljava/util/Enumeration; // Signature: ()Ljava/util/Enumeration<Ljava/lang/String;>; // Stack: 3, Locals: 1 public java.util.Enumeration entries(); 0 new java.lang.RuntimeException [2] 3 dup 4 ldc <String "Stub!"> [3] 6 invokespecial java.lang.RuntimeException(java.lang.String) [4] 9 athrow Line numbers: [pc: 0, line: 10] Local variable table: [pc: 0, pc: 10] local: this index: 0 type: dalvik.system.DexFile // Method descriptor #30 ()V // Stack: 3, Locals: 1 protected void finalize() throws java.io.IOException; 0 new java.lang.RuntimeException [2] 3 dup 4 ldc <String "Stub!"> [3] 6 invokespecial java.lang.RuntimeException(java.lang.String) [4] 9 athrow Line numbers: [pc: 0, line: 11] Local variable table: [pc: 0, pc: 10] local: this index: 0 type: dalvik.system.DexFile // Method descriptor #42 (Ljava/lang/String;)Z public static native boolean isDexOptNeeded(java.lang.String arg0) throws java.io.FileNotFoundException, java.io.IOException; } Thanks

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  • JRuby wrong element type class java.lang.String(array contains char) related to JAVA_HOME

    - by Daryl
    I am on Ubuntu x64 bit running: java version "1.6.0_18" OpenJDK Runtime Environment (IcedTea6 1.8) (6b18-1.8-0ubuntu1) OpenJDK 64-Bit Server VM (build 14.0-b16, mixed mode) and jruby 1.4.0 (ruby 1.8.7 patchlevel 174) (2010-02-11 6586) (OpenJDK 64-Bit Server VM 1.6.0_18) [amd64-java] I have this code running on my Windows 7 computer at home. I recently copied over my whole folder over to Ubuntu, installed java, jruby, and associated gems but I get this error when I run my main file: jruby run.rb test =================Processing FREDERICKSBURG_1.1======================= ERROR IN TESTING wrong element type class java.lang.String(array contains char) /home/daryl/Desktop/work/Code/geografikos/lib/sentence_splitter/splitter.rb:21:in `to_java' /home/daryl/Desktop/work/Code/geografikos/lib/sentence_splitter/splitter.rb:21:in `split' /home/daryl/Desktop/work/Code/geografikos/lib/models/page.rb:103:in `sentences' /home/daryl/Desktop/work/Code/geografikos/lib/extractor/lingpipe_svm.rb:34:in `extract' /home/daryl/Desktop/work/Code/geografikos/lib/extractor/geo_controller.rb:9:in `process' /home/daryl/Desktop/work/Code/geografikos/lib/extractor/geo_controller.rb:8:in `each' /home/daryl/Desktop/work/Code/geografikos/lib/extractor/geo_controller.rb:8:in `process' /home/daryl/Desktop/work/Code/geografikos/lib/extractor/geo_controller.rb:6:in `each' /home/daryl/Desktop/work/Code/geografikos/lib/extractor/geo_controller.rb:6:in `process' /home/daryl/Desktop/work/Code/geografikos/lib/statistics.rb:111:in `generate_all' /home/daryl/Desktop/work/Code/geografikos/lib/statistics.rb:105:in `each' /home/daryl/Desktop/work/Code/geografikos/lib/statistics.rb:105:in `generate_all' run.rb:56 The focus of the error is: ERROR IN TESTING wrong element type class java.lang.String(array contains char) Everything works fine on my windows machine. I figured I was getting this error because I did not have JAVA_HOME set however I added this to bashrc as: export JAVA_HOME=/usr/lib/jvm/java-1.6.0-openjdk and have confirmed: echo $JAVA_HOME /usr/lib/jvm/java-1.6.0-openjdk I can produce a similar error by removing my JAVA_HOME variable on windows: =================Processing FREDERICKSBURG_1.3======================= ERROR IN TESTING cannot convert instance of class org.jruby.RubyString to char C:/work/Code/geografikos/lib/sentence_splitter/splitter.rb:21:in `to_java' C:/work/Code/geografikos/lib/sentence_splitter/splitter.rb:21:in `split' C:/work/Code/geografikos/lib/models/page.rb:103:in `sentences' C:/work/Code/geografikos/lib/extractor/lingpipe_svm.rb:34:in `extract' C:/work/Code/geografikos/lib/extractor/geo_controller.rb:9:in `process' C:/work/Code/geografikos/lib/extractor/geo_controller.rb:8:in `each' C:/work/Code/geografikos/lib/extractor/geo_controller.rb:8:in `process' C:/work/Code/geografikos/lib/extractor/geo_controller.rb:6:in `each' C:/work/Code/geografikos/lib/extractor/geo_controller.rb:6:in `process' C:/work/Code/geografikos/lib/statistics.rb:111:in `generate_all' C:/work/Code/geografikos/lib/statistics.rb:105:in `each' C:/work/Code/geografikos/lib/statistics.rb:105:in `generate_all' run.rb:56 It is obviously not exactly the same but I have a feeling this has to do with the java path. You can probably derive from the error that I am just trying to convert a ruby variable to java using to_java. This works fine on my windows machine and I have confirmed the gems are the same but I don't think this has to do with gems. I lied. I changed my JAVA_HOME back on my windows machine and this error still occurs. So now the code doesn't run on either machine. I recently installed git on my windows machine and added the code to a repository. But I haven't really done anything with it. All it said was it will convert all LF to CRLF...That shouldn't change anything though should it? Any ideas on why I am now getting these errors? I haven't changed anything on my windows machine in months except for installing git.

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  • Navigation to call action for bean class

    - by Muthu
    I am using JSF 2.0 and PrimeFaces 3.0. I have uploaded the images and have to crop the image. The images are uploaded and successfully displayed in the upload pages. When I select the images and click the crop button the corresponding crop bean is not called. If I don't select the image and click the crop button the corresponding crop bean class is called but a NullPointerException occurred. What is the problem? The Facelet view is: <h:form> <p:panel header="FILE UPLOAD WITH CROPPER" style="width:900px; margin: 0 auto; margin-top:0px"> <p:fileUpload fileUploadListener="#{photoUploadAction.handleImageUpload}" mode="advanced" update="getImageId,messages" auto="false" allowTypes="/(\.|\/)(gif|jpe?g|png)$/"/> <p:growl id="messages" showDetail="true"/> <p:growl id="uploadMessages" showSummary="true" showDetail="true"/> <h:panelGrid columns="2" > <p:imageCropper value="#{photoUploadAction.croppedImage}" id="getImageId" image="images/#{photoUploadVO.imageName}"/> </h:panelGrid> <p:commandButton value="Crop" update="getImageId" action="#{imageCropperBean.crop}" /> </p:panel> </h:form> BACKING BEAN for ImageCropper: @ManagedBean(name="imageCrop") @RequestScoped public class ImageCropperBean { private CroppedImage croppedImage; private String newFileName; private String imageName; public String getImageName() { return imageName; } public void setImageName(String imageName) { System.out.println("TEH IMAGE NAME ===="+imageName); this.imageName = imageName; } public String getNewFileName() { return newFileName; } public void setNewFileName(String newFileName) { System.out.println("AAAAAAAAAAAAAA"+this.newFileName); this.newFileName = newFileName; } public CroppedImage getCroppedImage() { return croppedImage; } public void setCroppedImage(CroppedImage croppedImage) { System.out.println("cRRRRRRRRRRRRR"+croppedImage); this.croppedImage = croppedImage; } public ImageCropperBean(){ } public String crop() { System.out.println("WELCOMEMMMMMMMMMMMMMM"); FacesContext context = FacesContext.getCurrentInstance(); ImageCropperBean imageCropperBean = (ImageCropperBean) context.getApplication().evaluateExpressionGet(context, "#{imageCropperBean}", ImageCropperBean.class); ServletContext servletContext = (ServletContext) FacesContext.getCurrentInstance().getExternalContext().getContext(); newFileName = servletContext.getRealPath("") + File.separator + "cropImage" + File.separator+ "croppedImage.jpg"; System.out.println("FILE NAME NAME NAME NAME "+newFileName); String file = new File(newFileName).getName(); System.out.println("DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD"+file); imageCropperBean.setImageName(file); File fileFolder = new File("e:/Mecherie_project/image_web/WebContent/cropImages",file); System.out.println("FILE ANE"+file); // String target=null; FileImageOutputStream imageOutput; try { imageOutput = new FileImageOutputStream(fileFolder); System.out.println("HHHHHHHHHH=="+imageOutput); imageOutput.write(croppedImage.getBytes(), 0, croppedImage.getBytes().length); imageOutput.close(); FacesMessage msg = new FacesMessage("Succesful", file + " is cropped."); FacesContext.getCurrentInstance().addMessage(null, msg); } catch (FileNotFoundException e) { FacesMessage error = new FacesMessage(FacesMessage.SEVERITY_ERROR, "The files were not Cropped!", ""); FacesContext.getCurrentInstance().addMessage(null, error); e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); FacesMessage error = new FacesMessage(FacesMessage.SEVERITY_ERROR, "The files were not Cropped!", ""); FacesContext.getCurrentInstance().addMessage(null, error); } // System.out.println("ghfhgfghgh"+target); return "success"; } }

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