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• What is a good way of coding a file processing program, which accepts multisource data in Java

  - by jjepsuomi

  I'm making a data prosessing system, which currently is using csv-data as input and output form. In the future I might want to add support for example database-, xml-, etc. typed input and output forms. How should I desing my program so that it would be easy to add support for new type of data sources? Should simply make for example an abstract data class (which would contain the basic file prosessing methods) and then inherit this class for database, xml, etc. cases? Hope my question is clear =) In other words my question is: "How to desing a file prosessing system, which can be easily updated to accept input data from different sources (database, XML, Excel, etc.)".

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• Java: ListA.addAll(ListB) fires NullPointerException?

  - by HH

  The err part is Capitalized in the code, it also comes in foreaching. Because of the abstract list, it cannot be initialized, declaration is in a static field. The lists have the same type. import java.util.*; public class Test { public static final List<String> highPrio = Arrays.asList("*","/"); public static List<String> ops; public static void main(String[] args) { //ERROR HERE, why do it throw nullPointer? ops.addAll(highPrio); for(String s : ops) { System.out.println(s); } } }

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• Composite pattern in C++ problem

  - by annouk

  Hello! I have to work with an application in C++ similar to a phone book: the class Agenda with an STL list of Contacts.Regarding the contacts hierarchy,there is a base-class named Contact(an abstract one),and the derived classes Friend and Acquaintance(the types of contact). These classes have,for instance, a virtual method called getName,which returns the name of the contact. Now I must implement the Composite pattern by adding another type of contact,Company(being derived from Contact),which also contains a collection of Contacts(an STL list as well),that can be either of the "leaf" type(Friends or Acquaintances),or they can be Companies as well. Therefore,Company is the Compound type. The question is: how and where can I implement an STL find_if to search the contact with a given name(via getName function or suggest me smth else) both among the "leaf"-type Contact and inside the Company collection? In other words,how do I traverse the tree in order to find possible matches there too,using an uniform function definition? I hope I was pretty clear...

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• Set cookie value before view loaded in MVC?

  - by James123

  I need to set a cookie value before my view called. otherwise I have to refresh the page to get cookie value in the view. The problem here is the value of cookie will get in controller. [HttpGet] [Route("Abstract/{meetingCode}")] [AllowAnonymous] public ActionResult Index(string meetingCode) { var meetingAbstract = new MeetingAbstract(); meetingAbstract.Meeting = _abstractContext.GetMeetingWithMeetingCode(meetingCode); if (meetingAbstract.Meeting != null) { var cookie = new HttpCookie("_culture"); cookie.Value = meetingAbstract.Meeting.language.language_locale_code;//"en-US"; cookie.Expires = DateTime.Now.AddDays(365); cookie.Path = "/"; this.ControllerContext.HttpContext.Response.Cookies.Add(cookie); ... Any other way without refresh the page again to set cookie value?

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• CoreData Model Objects for API

  - by theiOSguy

  I am using CoreData in my application. I want to abstract out all the CoreData related stuff as an API so that the consume can use the API instead of directly using CoreData and its generated model objects. CoreData generates the managed objects model as following @interface Person : NSManagedObject @end I want to define my API for example MyAPI and it has a function called as createPerson:(Person*)p; So the consumer of this createPerson API needs to create a Person data object (like POJO in java world) and invoke this API. But I cannot create Person object using Person *p = [Person alloc] init] because the designated initializer for this Person model created by CoreData does not allow this type of creation. So should I define corresponding user facing data object may be PersonDO and this API should take that instead to carry the data into the API implementation? Is my approach right? Any expert advise if design the API this way is a good design pattern?

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• Using Rails, how can I set my primary key to not be an integer-typed column?

  - by Rudd Zwolinski

  I'm using Rails migrations to manage a database schema, and I'm creating a simple table where I'd like to use a non-integer value as the primary key (in particular, a string). To abstract away from my problem, let's say there's a table employees where employees are identified by an alphanumeric string, e.g. "134SNW". I've tried creating the table in a migration like this: create_table :employees, {:primary_key => :emp_id} do |t| t.string :emp_id t.string :first_name t.string :last_name end What this gives me is what seems like it completely ignored the line t.string :emp_id and went ahead and made it an integer column. Is there some other way to have rails generate the PRIMARY_KEY constraint (I'm using PostgreSQL) for me, without having to write the SQL in an execute call? NOTE: I know it's not best to use string columns as primary keys, so please no answers just saying to add an integer primary key. I may add one anyway, but this question is still valid.

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• C++ enforce conditions on inherited classes

  - by user231536

  I would like to define an abstract base class X and enforce the following: a) every concrete class Y that inherits from X define a constructor Y(int x) b) it should be possible to test whether two Y objects are equal. For a, one not very good solution is to put a pure virtual fromInt method in X which concrete class will have to define. But I cannot enforce construction. For b), I cannot seem to use a pure virtual method in X bool operator == (const X& other) const =0; because in overridden classes this remains undefined. It is not enough to define bool operator == (const Y& other) const { //stuff} because the types don't match. How do I solve these problems?

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• New to threading in C#, can you make thread methods generic and what are the dangers?

  - by ibarczewski

  Hey all, I'm just now starting to get into the idea of threading, and wanted to know if I could make this more abstract. Both foo and bar derive methods from a base class, so I'd like to pass in one or the other and be able to do work using a method that was derived. I'd also like to know how you properly name threads and the methods inside threads. if (ChkFoo.Checked) { Thread fooThread = new Thread(new ThreadStart(this.ThreadedFooMethod)); fooThread.Start(); } if (ChkBar.Checked) { Thread barThread = new Thread(new ThreadStart(this.ThreadedBarMethod)); barThread.Start(); } . . . public void ThreadedFooMethod() { Foo newFoo = new Foo(); //Do work on newFoo } public void ThreadedBarMethod() { Bar newBar = new Bar(); //Do similar work } Thanks all!

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• Getting all inner classes by reflection

  - by Roman

  I have the following problem. I have this pretty class and now I want to get all the classes that extend that class (inner classes ) and fill 'classList' with it. ( in an automatic way of course ) public abstract class CompoundReference { private static List<Class<? extends CompoundReference>> classList = new ArrayList<Class<? extends CompoundReference>>(); @CompoundKey(gsType = User.class, dbType = UserDetailsMappings.class) public static class CUser extends CompoundReference { } @CompoundKey(gsType = Catalog.class, dbType = CatalogDetailsMappings.class) public static class CCatalog extends CompoundReference { } @CompoundKey(gsType = Product.class, dbType = ProductDetailsMappings.class) public static class CProduct extends CompoundReference { } @CompoundKey(gsType = Category.class) public static class CCategory extends CompoundReference { } @CompoundKey(gsType = Poll.class, dbType = PollDetailsMappings.class) public static class CPoll extends CompoundReference { } // much mroe inner classes Some manual solution would be just to main such a static block , that is something that I dont want to do. static { classList.addAll(Arrays.asList(CUser.class, CCatalog.class, CProduct.class, CCategory.class, CPoll.class, CComment.class, CWebPage.class, CReview.class, CPost.class, CMessage.class, CStory.class,CPicture.class)); }

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• Create object of unknown class (two inherited classes)

  - by Paul

  I've got the following classes: class A { void commonFunction() = 0; } class Aa: public A { //Some stuff... } class Ab: public A { //Some stuff... } Depending on user input I want to create an object of either Aa or Ab. My imidiate thought was this: A object; if (/*Test*/) { Aa object; } else { Ab object; } But the compiler gives me: error: cannot declare variable ‘object’ to be of abstract type ‘A’ because the following virtual functions are pure within ‘A’: //The functions... Is there a good way to solve this?

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• How to filter/sort/rank object model nodes?

  - by BCS

  I have some kind of object model and I need to filter and sort it's nodes for some kind of property. What kinds of automated systems exist to generate and select properties of the object model that correlate to what I want? (I'm intentionally being abstract and non-specific) I'm thinking of a system that works kind of like spam filters or supervised classification systems in that given an example data set it identifies rules that find nodes of interest. However I'm looking for a more general system in that it shouldn't require any design time information about the object model. It should work equality well as a spam filter on e-mail, a bug finder on a code base, an interest filter in a newsgroup or bot accounts finder on a social networking site. As long as it can explore the object model via reflection and be given a set of "interesting" nodes, it should be able to find rules that will find more nodes like them.

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• How to step into the world of J2EE?

  - by Michael Lai

  I am new to J2ee. I have experience in Java core, JSP,Servlet, XML, HTML, What should i learn to step into the world of J2EE? Framework(Spring, Hibernate, Struts)? But the framework is too abstract for me.I saw lots of job post which requires frameworks, some jobs require EJB,JPA. I do not where to start. Any experts can give me hints on that? I found the tutorial of J2EE 5 published by ORACLE is not easy to understand. Too much jargon....

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• EntityFramework 4.0: can you return different types depending on data in the database?

  - by user200341

  I have a Media table in the database. I also have an IMedia interface. I have two different media types that implements the same interface: 1) AudioMedia 2) PictureMedia What I wonder here, is if I can use EntityFramework (I'm using an EDMX file but I have my models in a separate library, with automatic code generation turned off), and depending on the data in the database, select what type to get (AutioMedia or PictureMedia). Since they are both implementing the same interface (could be changed to an abstract class if needed I suppose), I'm thinking that somewhere along the way you could specify what class it should be. I should perhaps point out that I have a class that inherits from ObjectContext to access the objects. Perhaps there is something that that can be done?

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• Why isn't the new() generic constraint satisfied by a class with optional parameters in the construc

  - by Joshua Flanagan

  The following code fails to compile, producing a "Widget must be a non-abstract type with a public parameterless constructor" error. I would think that the compiler has all of the information it needs. Is this a bug? An oversight? Or is there some scenario where this would not be valid? public class Factory<T> where T : new() { public T Build() { return new T(); } } public class Widget { public Widget(string name = "foo") { Name = name; } public string Name { get; set; } } public class Program { public static void Main() { var widget = new Widget(); // this is valid var factory = new Factory<Widget>(); // compiler error } }

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• Calling inheriting class methods via interface.

  - by Stacey

  Given the scenario... interface IBase{ void Process(int value); } abstract class Base : IBase { public virtual void Process(int value){ throw new NotImplementedException(); } } class Implemented: Base, IBase { public void Process(int value) { // .. some code here.. } } I'm trying to write a loop similar to the following. foreach( Base b in CollectionOfImplemented ) { b.Process( // something will go here // ); } Trying this, it keeps calling Base.Process, instead of Implemented.Process; but the type in the collection is Implemented, not Base. Boxing it seems to work, but I was hoping to see if I could find a more intelligent approach to it, since the Collection will contain other types of objects that also inherit from Base.

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• .NET CF 2.0: Stream implements IDisposable ... kind of?

  - by mvanbem

  I've run into something odd in a .NET CF 2.0 project for Pocket PC 2003 (Visual Studio 2005). I was dealing with a System.IO.Stream object and found that the IDE wouldn't auto-complete the Dispose() method. I typed it in manually and received: 'System.IO.Stream.Dispose(bool)' is inaccessible due to its protection level The error is referring to the protected Dispose(bool) method. Dispose() is either private or not present. Question 1: How is this possible? Stream implements IDisposable: public abstract class Stream : MarshalByRefObject, IDisposable ... and IDisposable requires a Dispose() method: public interface IDisposable { void Dispose(); } I know the compiler won't let me get away with that in my code. Question 2: Will I cause problems by working around and disposing my streams directly? IDisposable idisp = someStream; idisp.Dispose(); The implicit cast is accepted by the compiler.

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• Core Data: Detecting the type and casting it

  - by Tim Sullivan

  I have set up a Core Data model that includes an entity, Item with a 1-M relationship with the abstract entity Place, so that an item has many places. There are several entities with the parent set to Place. I want to set up several UI elements depending on the descendent place types. I have a loop that looks something like this: for (Place *place in item.places) { } ... but I'm not sure how to detect what type the place is, and how to cast it to the proper type so that I can access its properties. Thanks for any help!

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• Using ANTLR with Left-Recursive Rules

  - by CNevin561

  Basically Ive written a Parse for a language with just basic arithmetic operators ( +, -, * / ) etc, but for the minus and plus cases, the Abstract Syntax Tree which is generated has parsed them as right associative when they need to be left associative. Having a googled for a solution, i found a tutorial that suggests rewriting the rule from: Expression ::= Expression <operator> Term | Term as Expression ::= Term <operator> Expression*. However in my head this seems to generate the tree the wrong way round. Any pointers on a way to resolve this issue?

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• Make object by it's name

  - by Ockonal

  Hello, is it possible to return exemplar of object using passed type name (string) in c++? I have some base abstract class Base and a few derivates. Example code: class Base { /* ... */ }; class Der1 : public Base { /* ... */ }; class Der2 : public Base { /* ... */ }; And I need function like: Base *objectByType(const std::string &name); Number of derivates classes are changeable and I don't want to make something like switching of name and returning by hands new object type. Is it possible in c++ to do that automatically anyway? p.s. usage should looks like: dynamic_cast<Der1>(objectByType("Der1")); I need pure c++ code (crossplatform). Using boost is permissible.

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• Just how much do I want to make virtual?

  - by Alex

  I am writing an abstract superclass where literally every method is going to be overridden. There is some default functionality I could implement, but most of the time it's enough to leave the implementation to the subclass writer. Since just about every method is going to be overwritten, how much should I make virtual and how much should I just leave as regular methods? In the current incarnation, everything is virtual, but I still haven't let this loose to anyone to use, so the design is flexible. What advantages/disadvantages are there to virtual functions? Links to good reading material about this would be appreciated.

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• How can I pass a type as a parameter in scala?

  - by rsan

  I'm having a really hard time trying to figure out how can I store or pass a type in scala. What I want to achive is something like this: abstract class Foo( val theType : type ) object Foo{ case object Foo1 extends Foo(String) case object Foo2 extends Foo(Long) } So at some point I can do this: theFoo match{ case String => "Is a string" case Long => "Is a long" } and when obtaining the object being able to cast it: theFoo.asInstanceOf[Foo1.theType] Is this possible? If is possible, is a good aproach? What I'm trying to achieve ultimately is writing a pseudo schema for byte stream treatment. E.g if I have an schema Array(Foo1,Foo1,Foo2,Foo3,Foo1) I could parse Arrays of bytes that complain with that schema, if at some point I have a different stream of bytes I could just write a new schema Array(Foo3, Foo4, Foo5) without having to reimplement parsing logic. Regards,

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• Printing a list using reflection

  - by TFool

  public class Service{ String serviceName; //setter and getter } public class Version{ String VersionID; //setter and getter } public void test(Object list){ //it shd print the obtained list } List< Service list1; //Service is a Bean List< Version list2; //Version is a Bean test(list1); test(list2); Now the test method shd print the obtained list - (i.e) If the list is of type Service ,then serviceName should be printed using its getter. If the list type is Version versionID should be printed. Is it possible to achieve this without using Interface or abstract class?

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• Fastest method for SQL Server inserts, updates, selects

  - by Ian

  I use SPs and this isn't an SP vs code-behind "Build your SQL command" question. I'm looking for a high-throughput method for a backend app that handles many small transactions. I use SQLDataReader for most of the returns since forward only works in most cases for me. I've seen it done many ways, and used most of them myself. Methods that define and accept the stored procedure parameters as parameters themselves and build using cmd.Parameters.Add (with or without specifying the DB value type and/or length) Assembling your SP params and their values into an array or hashtable, then passing to a more abstract method that parses the collection and then runs cmd.Parameters.Add Classes that represent tables, initializing the class upon need, setting the public properties that represent the table fields, and calling methods like Save, Load, etc I'm sure there are others I've seen but can't think of at the moment as well. I'm open to all suggestions.

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• Dependency Injection. Assign values to IENUMERABLE

  - by Boss

  public interface IFeature { string FeatureName { get; set; } } public interface IFeatureRegistry { IEnumerable<IFeature> Features { get; set; } bool IsEnabled(IEnumerable<string> featurePath); } public interface IApplicationTenant { string ApplicationName { get; } IFeatureRegistry EnabledFeatures { get; } } public abstract class AbstractApplicationTenant : IApplicationTenant { public string ApplicationName { get; protected set; } public IFeatureRegistry EnabledFeatures { get; protected set; } } public class SampleTenant : AbstractApplicationTenant { public SampleTenant() { ApplicationName = "Sample 1"; EnabledFeatures = null; } } I am new to this field. My question is how to assign values to EnabledFeatures? Thanks Jeco

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• How can I remove the numeration of some titles in LaTeX?

  - by Tae

  Hi: I'm writing my degree project report using the article class and I want a structure like this: Abstract Introduction 1. What 2. Where 3. Etc. I was searching and I found that using \setcounter{secnumdepth}{-1} the complete numeration is eliminated. And if I use * these sections don't appear in the table of content. So what can I do? Can this be done without installing packages (like memoir)?

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