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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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• Is this the correct approach to an OOP design structure in php?

  - by Silver89

  I'm converting a procedural based site to an OOP design to allow more easily manageable code in the future and so far have created the following structure: /classes /templates index.php With these classes: ConnectDB Games System User User -Moderator User -Administrator In the index.php file I have code that detects if any $_GET values are posted to determine on which page content to build (it's early so there's only one example and no default): function __autoload($className) { require "classes/".strtolower($className).".class.php"; } $db = new Connect; $db->connect(); $user = new User(); if(isset($_GET['gameId'])) { System::buildGame($gameId); } This then runs the BuildGame function in the system class which looks like the following and then uses gets in the Game Class to return values, such as $game->getTitle() in the template file template/play.php: function buildGame($gameId){ $game = new Game($gameId); $game->setRatio(900, 600); require 'templates/play.php'; } I also have .htaccess so that actual game page url works instead of passing the parameters to index.php Are there any major errors of how I'm setting this up or do I have the general idea of OOP correct?

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• Java word scramble game [closed]

  - by Dan

  I'm working on code for a word scramble game in Java. I know the code itself is full of bugs right now, but my main focus is getting a vector of strings broken into two separate vectors containing hints and words. The text file that the strings are taken from has a colon separating them. So here is what I have so far. public WordApp() { inputRow = new TextInputBox(); inputRow.setLocation(200,100); phrases = new Vector <String>(FileUtilities.getStrings()); v_hints = new Vector<String>(); v_words = new Vector<String>(); textBox = new TextBox(200,100); textBox.setLocation(200,200); textBox.setText(scrambled + "\n\n Time Left: \t" + seconds/10 + "\n Score: \t" + score); hintBox = new TextBox(200,200); hintBox.setLocation(300,400); hintBox.hide(); Iterator <String> categorize = phrases.iterator(); while(categorize.hasNext()) { int index = phrases.indexOf(":"); String element = categorize.next(); v_words.add(element.substring(0,index)); v_hints.add(element.substring(index +1)); phrases.remove(index); System.out.print(index); } The FileUtilities file was given to us by the pofessor, here it is. import java.util.*; import java.io.*; public class FileUtilities { private static final String FILE_NAME = "javawords.txt"; //------------------ getStrings ------------------------- // // returns a Vector of Strings // Each string is of the form: word:hint // where word contains no spaces. // The words and hints are read from FILE_NAME // // public static Vector<String> getStrings ( ) { Vector<String> words = new Vector<String>(); File file = new File( FILE_NAME ); Scanner scanFile; try { scanFile = new Scanner( file); } catch ( IOException e) { System.err.println( "LineInput Error: " + e.getMessage() ); return null; } while ( scanFile.hasNextLine() ) { // read the word and follow it by a colon String s = scanFile.nextLine().trim().toUpperCase() + ":"; if( s.length()>1 && scanFile.hasNextLine() ) { // append the hint and add to collection s+= scanFile.nextLine().trim(); words.add(s); } } // shuffle Collections.shuffle(words); return words; } }

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• Finding the best practice for a game simulating tool

  - by Tougheart

  I'm studying Java right now, and I'm thinking of this tool as my practice project. The game is "League of Legends" in case anyone knows it, I'm not actually simulating the game as in simulating game play, I'm just trying to create a tool that can compare different champions to each other based on their own abilities and items bought inside the game. The game basics are: Every player has a champion in a team of 5 players playing against another team. Each champion has a different set of abilities (usually 4) that s/he uses to do damage to opposing champions. Each champion gets stronger by buying different items, increasing the attack it deals or decreasing the damage received. What I want to do is to create a tool to be used outside the game enabling players to try out different builds for their champions and compare the figures against other champions they usually fight against. The goal is to enable players get a deeper understanding of the different item combinations (builds) that can be used during the games, instead of trying them out in real games which can be somehow very time consuming. What I'm stuck at is the best practice I should follow to make this possible using Java, I can't figure out which classes should inherit from which, should I make champions and items specs in the code or extracted from other files, specially that I'm talking about hundreds of items and champions to use in that tool. I'm self studying Java, and I don't have much practice at it, so I would really appreciate any broad guidelines regarding this, and sorry if my question doesn't fit here, I tried to follow the rules. English isn't my native language, so I'm really sorry if I wasn't clear enough, I would be more than happy to explain anything that's not understood.

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• How can I design my classes to include calendar events stored in a database?

  - by Gianluca78

  I'm developing a web calendar in php (using Symfony2) inspired by iCal for a project of mine. At this moment, I have two classes: a class "Calendar" and a class "CalendarCell". Here you are the two classes properties and method declarations. class Calendar { private $month; private $monthName; private $year; private $calendarCellList = array(); private $translator; public function __construct($month, $year, $translator) {} public function getCalendarCellList() {} public function getMonth() {} public function getMonthName() {} public function getNextMonth() {} public function getNextYear() {} public function getPreviousMonth() {} public function getPreviousYear() {} public function getYear() {} private function calculateDaysPreviousMonth() {} private function calculateNumericDayOfTheFirstDayOfTheWeek() {} private function isCurrentDay(\DateTime $dateTime) {} private function isDifferentMonth(\DateTime $dateTime) {} } class CalendarCell { private $day; private $month; private $dayNameAbbreviation; private $numericDayOfTheWeek; private $isCurrentDay; private $isDifferentMonth; private $translator; public function __construct(array $parameters) {} public function getDay() {} public function getMonth() {} public function getDayNameAbbreviation() {} public function isCurrentDay() {} public function isDifferentMonth() {} } Each calendar day can includes many calendar events (such as appointments or schedules) stored in a database. My question is: which is the best way to manage these calendar events in my classes? I think to add a eventList property in CalendarCell and populate it with an array of CalendarEvent objects fetched by the database. This kind of solution doesn't allow other coders to reuse the classes without db (because I should inject at least a repository services also) just to create and visualize a calendar... so maybe it could be better to extend CalendarCell (for instance in CalendarCellEvent) and add the database features? I feel like I'm missing some crucial design pattern! Any suggestion will be very appreciated!

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• Advice on reconciling discordant data

  - by Justin

  Let me support my question with a quick scenario. We're writing an app for family meal planning. We'll produce daily plans with a target calorie goal and meals to achieve it for our nuclear family. Our calorie goal will be calculated for each person from their attributes (gender, age, weight, activity level). The weight attribute is the simplest example here. When Dad (the fascist nerd who is inflicting this on his family) first uses the application he throws approximate values into it for Daughter. He thinks she is 5'2" (157 cm) and 125 lbs (56kg). The next day Mom sits down to generate the menu and looks back over what the bumbling Dad did, quietly fumes that he can never recall anything about the family, and says the value is really 118 lbs! This is the first introduction of the discord. It seems, in this scenario, Mom is probably more correct that Dad. Though both are only an approximation of the actual value. The next day the dear Daughter decides to use the program and sees her weight listed. With the vanity only a teenager could muster she changes the weight to 110 lbs. Later that day the Mom returns home from a doctor's visit the Daughter needed and decides that it would be a good idea to update her Daughter's weight in the program. Hooray, another value, this time 117 lbs. Now how do you reconcile these data points? Measurement error, confidence in parties, bias, and more all confound the data. In some idealized world we'd have a weight authority of some nature providing the one and only truth. How about in our world though? And the icing on the cake is that this single data point changes over time. How have you guys solved or managed this conflict?

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• Best practice to collect information from child objects

  - by Markus

  I'm regularly seeing the following pattern: public abstract class BaseItem { BaseItem[] children; // ... public void DoSomethingWithStuff() { StuffCollection collection = new StuffCollection(); foreach(child c : children) c.AddRequiredStuff(collection); // do something with the collection ... } public abstract void AddRequiredStuff(StuffCollection collection); } public class ConcreteItem : BaseItem { // ... public override void AddRequiredStuff(StuffCollection collection) { Stuff stuff; // ... collection.Add(stuff); } } Where I would use something like this, for better information hiding: public abstract class BaseItem { BaseItem[] children; // ... public void DoSomethingWithStuff() { StuffCollection collection = new StuffCollection(); foreach(child c : children) collection.AddRange(c.RequiredStuff()); // do something with the collection ... } public abstract StuffCollection RequiredStuff(); } public class ConcreteItem : BaseItem { // ... public override StuffCollection RequiredStuff() { StuffCollection stuffCollection; Stuff stuff; // ... stuffCollection.Add(stuff); return stuffCollection; } } What are pros and cons of each solution? For me, giving the implementation access to parent's information is some how disconcerting. On the other hand, initializing a new list, just to collect the items is a useless overhead ... What is the better design? How would it change, if DoSomethingWithStuff wouldn't be part of BaseItem but a third class? PS: there might be missing semicolons, or typos; sorry for that! The above code is not meant to be executed, but just for illustration.

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• Java desktop programmer starting to learn Android development: how different is it?

  - by Prog

  I'm a Java programmer. All of my experience is on desktop applications, using Swing for the GUI. I spend a lot of time studying OOP, I have decent understanding of OO concepts and I design and program by the OO approach. I'm thinking of starting to learn Android development soon, and I'm wondering how different it is from desktop development. Obviously the GUI libraries will be different (not Swing), but other than that, I want to know if there are significant differences. I will divide this question to two parts: Apart from the GUI libraries, am I still going to use the standard Java libarary I'm used to? Aka same data structues, same utility classes, etc.? If not, what are the main differences between the libraries I'm used to and the libraries I'll be using? How different is Android development in regard to OO design? Are all of the familiar principles, design patterns, techniques and best pratices just as valid and used? Or is OOP and OOD in Android development significantly different than OO in desktop development? To summarize: apart from GUI design, how different is Java Android development than Java desktop development?

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• Can the Abstract Factory pattern be considered as a case of polymorphism?

  - by rogcg

  I was looking for a pattern/solution that allows me call a method as a runtime exception in a group of different methods without using Reflection. I've recently become aware of the Abstract Factory Pattern. To me, it looks so much like polymorphism, and I thought it could be a case of polymorphism but without the super class WidgetFactory, as you can see in the example of the link above. Am I correct in this assumption?

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• Override methods should call base method?

  - by Trevor Pilley

  I'm just running NDepend against some code that I have written and one of the warnings is Overrides of Method() should call base.Method(). The places this occurs are where I have a base class which has virtual properties and methods with default behaviour but which can be overridden by a class which inherits from the base class and doesn't call the overridden method. For example, in the base class I have a property defined like this: protected virtual char CloseQuote { get { return '"'; } } And then in an inheriting class which uses a different close quote: protected override char CloseQuote { get { return ']'; } } Not all classes which inherit from the base class use different quote characters hence my initial design. The alternatives I thought of were have get/set properties in the base class with the defaults set in the constructor: protected BaseClass() { this.CloseQuote = '"'; } protected char CloseQuote { get; set; } public InheritingClass() { this.CloseQuote = ']'; } Or make the base class require the values as constructor args: protected BaseClass(char closeQuote, ...) { this.CloseQuote = '"'; } protected char CloseQuote { get; private set; } public InheritingClass() base (closeQuote: ']', ...) { } Should I use virtual in a scenario where the base implementation may be replaced instead of extended or should I opt for one of the alternatives I thought of? If so, which would be preferable and why?

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• Combinatorial explosion of interfaces: How many is too many?

  - by mga

  I'm a relative newcomer to OOP, and I'm having a bit of trouble creating good designs when it comes to interfaces. Consider a class A with N public methods. There are a number of other classes, B, C, ..., each of which interacts with A in a different way, that is, accesses some subset (<= N) of A's methods. The maximum degree of encapsulation is achieved by implementing an interface of A for each other class, i.e. AInterfaceForB, AInterfaceForC, etc. However, if B, C, ... etc. also interact with A and with each other, then there will be a combinatorial explosion of interfaces (a maximum of n(n-1), to be precise), and the benefit of encapsulation becomes outweighed by a code-bloat. What is the best practice in this scenario? Is the whole idea of restricting access to a class's public functions in different ways for other different classes just silly altogether? One could imagine a language that explicitly allows for this sort of encapsulation (e.g. instead of declaring a function public, one could specify exactly which classes it is visible to); Since this is not a feature of C++, maybe it's misguided to try to do it through the back door with interaces?

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• should singleton be life-time available or should it be destroyable?

  - by Manoj R

  Should the singleton be designed so that it can be created and destroyed at any time in program or should it be created so that it is available in life-time of program. Which one is best practice? What are the advantages and disadvantages of both? EDIT :- As per the link shared by Mat, the singleton should be static. But then what are the disadvantages of making it destroyable? One advantage is it memory can be saved when it is not useful.

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• What are startups expecting when they ask you to solve a programming challenge before interviewing? [closed]

  - by Swapnil Tailor

  I have applied to couple of startups and most of them are asking to solve programming challenge before they start on the interviewing candidate. I have submitted couple of the solutions and all the time getting rejected in the initial screening. Now what I think is, they will see my coding style, algorithm and OOD concepts that I have used to solve the problem. Can you guys input more on it as what other details are taken into consideration and how can I improve my coding for getting selected. By the way, I did all my coding in either Java/Perl. EDIT I feel the biggest reason for rejection is code didn't work for couple of use cases.

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• Proper library for enums

  - by Bobson

  I'm trying to refactor some code such that the display is separate from the implementation, and I'm not sure where to put the existing enums. My project is currently structured as follows: Utilities RemoteData (Depends on: Utilities) LocalData (Depends on: RemoteData, Utilities) RemoteWeb (Depends on: RemoteData, Utilities) LocalWeb (Depends on: RemoteData, LocalData, Utilities) I'm now trying to add "ViewLibrary (Depends on: Utilities)" to this list, and then adding it as a new dependency to both RemoteWeb and LocalWeb. It will contain a set of interfaces which the other two projects will implement, use to populate the view, and then consume the result. There's an enum which is currently used in all the projects except Utilities. It thus lives in the RemoteData project, because everything else depends on it. But this new ViewLibrary won't depend on either data project. So how will it know about this enum? Some options I see: Create a new project just for shared enum values. Add it to Utilities, even though it is related to data. Define it a second time in ViewLibrary, and require both RemoteWeb and LocalWeb to convert the one type into the other when they access the shared views. Add a dependency on RemoteData to the ViewLibrary, even though it's supposed to be independent of data-source. Are there any better options? Is this structure flawed to begin with?

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• Should I create an Enum mapping to my database table

  - by CrazyHorse

  I have a database table containing a list of systems relevant to the tool I am building, mostly in-house applications, or third-party systems we receive data from. This table is added to infrequently, approx every 2 months. One of these systems is Windows itself, which is where we store our users' LANs, and I now need to explicitly reference the ID relating to Windows to query for user name, team etc. I know it would be bad practice to embed the ID itself into the code, so my question is what would be the best way to avoid this? I'm assuming my options are: create a global constant representing this ID create a global enum containing all systems now create a global enum and add systems to it as & when they are required in the code retrieve the ID from the database based on system name I appreciate this may seem a trivial question, but I am going to have many situations like this during the course of this build, and although we are in complete control of the database I would like to conform to best practice as far as possible. Many thanks!

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• Is this a pattern? Proxy/delegation of interface to existing concrete implementation

  - by Ian Newson

  I occasionally write code like this when I want to replace small parts of an existing implementation: public interface IFoo { void Bar(); } public class Foo : IFoo { public void Bar() { } } public class ProxyFoo : IFoo { private IFoo _Implementation; public ProxyFoo(IFoo implementation) { this._Implementation = implementation; } #region IFoo Members public void Bar() { this._Implementation.Bar(); } #endregion } This is a much smaller example than the real life cases in which I've used this pattern, but if implementing an existing interface or abstract class would require lots of code, most of which is already written, but I need to change a small part of the behaviour, then I will use this pattern. Is this a pattern or an anti pattern? If so, does it have a name and are there any well known pros and cons to this approach? Is there a better way to achieve the same result? Rewriting the interfaces and/or the concrete implementation is not normally an option as it will be provided by a third party library.

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• Computer Engineer in CS Interview

  - by blasteye

  As a Computer Engineering student, while in school I've primarily dealt with C, Matlab, and VHDL. On my own though, i learned a bit about OOP (Polymorphism, inheritance, encapsulation), and have done quite a bit of web development using JavaScript/PHP/Node.js While at coding interviews I've be asked academia CS questions such as "abstract vs interface". The problem is that I didn't know the official terminology, but I have dealt with this type of programming decisions/concepts. Could anyone recommend a good resource for me to learn these academia CS terms?

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• How to learn to deliver quality software designs when working on a tight deadline?

  - by chester89

  I read many books about how to design great software, but I kind of struggle to come up with a good design decisions when it comes to business apps, especially when the timeframe is tough. In the company I currently work for, the following situation happen all the time: my teamlead tells me that there's a task to do, I call some guy or a girl from business who tells me exactly what is it they want, and then I start coding. The task always fits in some existing application (we do only web apps or web services), usually it's purpose is to pull data from one datasource and put into the other one, with some business logic attached in the process. I start coding and then, after spending some time on a problem, my code didn't work as expected - either because of technical mistake or my lack of knowledge of the domain. The business is ringing me 2-3 times a day to hurry me up. I ask my team lead to help, he comes up, sees my code and goes like 'What's this?'. Then he throws away about half of my code, including all the design decisions I made, writes 2-3 methods that does the job (each of them usually 200-300 lines long or more, by the way), and task is complete, code works as it should have. The guy is smarter than me, obviously, and I'm aware of that. My goal is to be better software developer, that means write better code, not finish the job quicker with some crappy code. And the thing is, when I have enough time to tackle a problem, I can come up with a design that is good (in my opinion, of course), but I fall short to do so when I'm on a tight deadline. What should I do? I am fully aware that it's rather vague explanation, but please bear with me

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• Testing my model for hybrid scheduling in Embedded Systems

  - by markusian

  I am working on a project for school, where I have to analyze the performances of a few fixed-priority servers algorithms (polling server, deferrable server, priority exchange) using a simulator in the case of hybrid scheduling, where we have both hard periodic tasks and soft aperiodic tasks. In my model I consider that: the hard tasks have a period equal to their deadline, with a known worst case execution time (wcet). The actual execution time could be smaller than the wcet. the soft tasks have a known wcet and random interarrival times. The actual execution time could be smaller than the wcet. In order to test those algorithms I need realistic case studies. For this reason I'm digging in the scientific literature but I am facing different problems: Sometimes I find a list of hard tasks with wcet, but it is not specified how the soft tasks parameters are found. Given the wcet of a task, how can I model its actual execution time? This means, what random distribution should I use considering the wcet? How can I model the random interarrival times of soft aperiodic tasks?

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• How can I design my classes for a calendar based on database events?

  - by Gianluca78

  I'm developing a web calendar in php (using Symfony2) inspired by iCal for a project of mine. At this moment, I have two classes: a class "Calendar" and a class "CalendarCell". Here you are the two classes properties and method declarations. class Calendar { private $month; private $monthName; private $year; private $calendarCellList = array(); private $translator; public function __construct($month, $year, $translator) {} public function getCalendarCells() {} public function getMonth() {} public function getMonthName() {} public function getNextMonth() {} public function getNextYear() {} public function getPreviousMonth() {} public function getPreviousYear() {} public function getYear() {} private function calculateDaysPreviousMonth() {} private function calculateNumericDayOfTheFirstDayOfTheWeek() {} private function isCurrentDay(\DateTime $dateTime) {} private function isDifferentMonth(\DateTime $dateTime) {} } class CalendarCell { private $day; private $month; private $dayNameAbbreviation; private $numericDayOfTheWeek; private $isCurrentDay; private $isDifferentMonth; private $translator; public function __construct(array $parameters) {} public function getDay() {} public function getMonth() {} public function getDayNameAbbreviation() {} public function isCurrentDay() {} public function isDifferentMonth() {} } Each calendar day can includes many events stored in a database. My question is: which is the best way to manage these events in my classes? I think to add a eventList property in CalendarCell and populate it with an array of CalendarEvent objects fetched by the database. This kind of solution doesn't allow other coders to reuse the classes without db (because I should inject at least a repository services also) just to create and visualize a calendar... so maybe it could be better to extend CalendarCell (for instance in CalendarCellEvent) and add the database features? I feel like I'm missing some crucial design pattern! Any suggestion will be very appreciated!

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• How to insert images using labels in NetBeans IDE, Java? [migrated]

  - by Vaishnavi Kanduri

  I'm making a virtual mall using NetBeans IDE 7.3.1 I inserted images using the following steps: Drag and drop label onto frame Go to label properties Click on ellipsis of 'icon' option Import to project, select desired image Resize or reposition it accordingly. Then, I saved the project, copied the project folder into a pendrive, tried to 'Open Project' in mate's laptop, using the same Java Netbeans IDE version. When I tried to open the frames, they displayed empty labels, without images. What went wrong?

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• Should interface only be used for behavior and not to show logical data grouped together?

  - by jags

  Should an interface only be used to specify certain behavior? Would it be wrong to use interface to group logically related data? To me it looks like we should not use interface to group logically related data as structure seems a better fit. A class may be used but class name should indicate something like DTO so that user gets the impression that class does not have any behavior. Please let me know if my assumption is correct. Also, are there any exceptions where interface can be used to group logically related data?

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• Figuring out the Call chain

  - by BDotA

  Let's say I have an assemblyA that has a method which creates an instance of assemblyB and calls its MethodFoo(). Now assemblyB also creates an instance of assemblyC and calls MethodFoo(). So no matter if I start with assemblyB in the code flow or with assemlyA, at the end we are calling that MethodFoo of AssemblyC(). My question is when I am in the MethodFoo() how can I know who has called me? Has it been a call originally from assemblyA or was it from assemlyB? Is there any design pattern or a good OO way of solving this?

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• Determining Object Access Using SQL Server Profiler

  Deanna Dicken examines an SQL Server Profiler event to determine object access...who is using the object, when, and how. This gives the SQL developer or database administrator much needed information for impact analysis prior to a change or the decommissioning of a SQL Server object.

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• Is wrapping a third party code the only solution to unit test its consumers? [closed]

  - by Songo

  I'm doing unit testing and in one of my classes I need to send a mail from one of the methods, so using constructor injection I inject an instance of Zend_Mail class which is in Zend framework. Now some people argue that if a library is stable enough and won't change often then there is no need to wrap it. So assuming that Zend_Mail is stable and won't change and it fits my needs entirely, then I won't need a wrapper for it. Now take a look at my class Logger that depends on Zend_Mail: class Logger{ private $mailer; function __construct(Zend_Mail $mail){ $this->mail=$mail; } function toBeTestedFunction(){ //Some code $this->mail->setTo('some value'); $this->mail->setSubject('some value'); $this->mail->setBody('some value'); $this->mail->send(); //Some } } However, Unit testing demands that I test one component at a time, so I need to mock the Zend_Mail class. In addition I'm violating the Dependency Inversion principle as my Logger class now depends on concretion not abstraction. Now is wrapping Zend_Mail the only solution or is there a better approach to this problem? The code is in PHP, but answers doesn't have to be. This is more of a design issue than a language specific feature

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