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• Object tree navigation language in Java

  - by lewap

  In the system which I'm currently developing I often have to navigate an object tree and based on its state and values take actions. In normal Java this results in tedious for loops, if statements etc... Are there alternative ways to achieve tree navigation, similar to XPath for XML? I know there is JXPath and OGNL, but do you know any other libraries for such purpose? Do you know any libraries which generate bytecodes for specific tree navigation expressions to make the processing as fast as Java native fors and ifs?

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• Should design, architecture and modeling be part of education?

  - by Gabriel Šcerbák

  I often heard, that those things cannot be teached, because you can master them only through good gut feeling fed with years of experience. However various patterns and principles are quite well documented and I start to think, that you can actually learn quite a lot of good stuff from books, training and exercises. What is your uptake?

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• What is the point in using a "real" database modeling tool?

  - by cdeszaq

  We currently have a 10 year old nasty, spaghetti-code-style SQL Server database that we are soon looking to pretty much re-write from scratch as part of a re-write to a large web application. (The existing application will serve as the functional requirements for the next incarnation of the app). Some have suggested we use Visio to do all the diagramming and to generate the DDL, but others have suggested we use a dedicated database design tool, rather than a diagramming tool that is able to export DDL. Is there any benefit to using "real" DB design tools, such as ModelRight, over general tools like Visio? If so, what are those specific benefits? Edit: In a nutshell, what can real/dedicated tools do that something like Visio can't, and how much do these capabilities matter (from a best-practices standpoint, for example)

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• What is the diffference between "data hiding" and "encapsulation"?

  - by john smith optional

  I'm reading "Java concurrency in practice" and there is said: "Fortunately, the same object-oriented techniques that help you write well-organized, maintainable classes - such as encapsulation and data hiding -can also help you crate thread-safe classes." The problem #1 - I never heard about data hiding and don't know what it is. The problem #2 - I always thought that encapsulation is using private vs public, and is actually the data hiding. Can you please explain what data hiding is and how it differs from encapsulation?

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• NHibernate Query object collection issue

  - by Mahesh

  Hi, I am new to NHibernate and need some information regarding the internal working of the engine: I have a table called Student and the design is as follows: RollNo Name City Postcode and there are 5 more columns like this. I have School class and mappings associated with it. I am querying RollNo and Name using session as given below: IQuery query = session.CreateQuery("SELECT RollNo,Name FROM Student); Executing query.List resulting in error because the query is returning object[][]. Now, I changed the query as given below: IQuery query = session.CreateQuery("FROM Student); Executing query.List on this query yeilds the desired results. But, the results contain more data than I want. Could you please let me know the query to which I can get RollNo and Name from Student and castable as Student collection. Thanks, Mahesh

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• (MyClassName)object vs. object as MyClassName

  - by Matthew Doyle

  Hello all, I was wondering what is the better method for Casting objects for C#: MyClassName test = (MyClassName)object; MyClassName test = object as MyClassName; I know already that if you do the first way, you get an exception, and the second way it sets test as null. However, I was wondering why do one over the other? I see the first way a lot, but I like how the second way because then I can check for null... If there isn't a 'better way' of doing it, what are the guidelines for using one way or the other?

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• How are java.lang.Object's protected methods protected from subclasses?

  - by Adrian Lang

  The keyword protected grants access to classes in the same package and subclasses (http://java.sun.com/docs/books/tutorial/java/javaOO/accesscontrol.html). Now, every class has java.lang.Object as superclass (http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Object.html). Hence I conclude that every class may access java.lang.Object's methods even if they are protected. Take a look at the following example: public class Testclass { public Object getOne() throws CloneNotSupportedException { return this.clone(); } public Object getTwo() throws CloneNotSupportedException { return ((Object) this).clone(); } } While getOne() compiles fine, getTwo() gives Testclass.java:6: clone() has protected access in java.lang.Object return ((Object) this).clone(); I neither understand why getTwo() doesn't compile nor what's the difference (regarding the access of java.lang.Objects members) with getOne().

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• Hibernate -using Table per subclass - how to link an existing superclass object to a sibclass object

  - by Chandni

  Hi, I have a User hibernate class, Clerk class and Consumer class. All these maps to their own tables in database. The User PK also acts as Clerk's and Consumer's PK. So now my problem is that if a user is initially a Clerk, he has a record in Users table and Clerks table. If that user wants to become a consumer, I want to link that User's record to the new Consumer's record. So even if I pass the userId to the consumer's record, it treats it as a new User to be persisted and gives a duplicate_key exception. How do I tell Hiernate to link the same user object with this new Consumer object. Thanks in advance, -Chandni

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• Making a design for a Problem [closed]

  - by Vaibhav Agarwal

  I have written many codes using OOPS and I am still to understand when is a code good enough to be accepted by experts. The thought procedure of every man is different and so is the design. My question is should I do something in particular to design my programs in such a way that they are good enough to be accepted by people. Other thing I have also read Head First Object Oriented Design but at last I feel that the way they design the problems is much different I would have designed them.

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• Converting HTML TAG Object to JSON Object

  - by cooldude

  Hi, I want to convert the html tag objects to json object in the javascript in order to send them to the server from the javascript. As i have to save these objects at the Ruby on Rails server. These HTML objects is the canvas tag object and the graphics objects created using CAKE API. I have used the stringify function but it is not working. Here is my code: var CAKECanvas = new Canvas(document.body, 1000,1000); var canvas=CAKECanvas.canvas; var text=document.createElement('textarea'); text.id="text"; text.rows="100"; text.cols="200"; document.body.appendChild(text); canvas.style.borderStyle="solid"; canvas.style.borderColor="black"; var rect= new Circle(); rect.radius=100; rect.centered=true; rect.cx=Math.random() * 500; rect.cy= Math.random() * 300; rect.stroke= false; rect.fill= "red"; rect.xDir = Math.random() > 0.5?1:-1; rect.yDir = Math.random() > 0.5?1:-1; var obj=new Object; var count = 0,k; for (k in rect) { if (rect.hasOwnProperty(k)) { count++; obj[k]=rect[k]; } } alert(count); rect.addFrameListener(function(t, dt) { this.cx += this.xDir * 50 * dt/1000; this.cy += this.yDir * 50 * dt/1000; if (this.cx > 550) { this.xDir = -1; } if (this.cx < 50) { this.xDir = 1; } if (this.cy > 350) { this.yDir = -1; } if (this.cy < 50) { this.yDir = 1; } } ); CAKECanvas.append(rect); var carAsJSON = JSON.stringify(obj); /////////////////ERROR

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• Are UML class diagrams adequated to design javascript systems?

  - by Vandell

  Given that UML is oriented towards a more classic approach to object orientation, is it still usable in a reliable way to design javascript systems? One specific problem that I can see is that class diagrams are, in fact, a structural view of the system, and javascript is more behaviour driven, how can you deal with it? Please, keep in mind that I'm not talking abot the real world domain here, It's a model for the solution that I'm trying to achieve.

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• Instantiate proper class based on some input

  - by Adam Backstrom

  I'm attempting to understand how "switch as a code smell" applies when the proper code path is determined by some observable piece of data. My Webapp object sets an internal "host" object based on the hostname of the current request. Each Host subclass corresponds to one possible hostname and application configuration: WwwHost, ApiHost, etc. What is an OOP way for a host subclass to accept responsibility for a specific hostname, and for Webapp to get an instance of the appropriate subclass? Currently, the hostname check and Host instantiation exists within the Webapp object. I could move the test into a static method within the Host subclasses, but I would still need to explicitly list those subclasses in Webapp unless I restructure further. It seems like any solution will require new subclasses to be added to some centralized list.

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• Unable to create unmanaged object using new keyword in managed C++

  - by chair79

  Hi all, I've created a class with a boost::unordered_map as a member, Linkage.h #ifndef LINKAGE_H #define LINKAGE_H #include <boost/unordered_map.hpp> class Linkage { private: boost::unordered_map<int, int> m_IOMap; public: .... }; Linkage.cpp #include "stdafx.h" ... // methods and in the managed side of C++, I try to create the pointer of the obj: private: System::Void Form1_Load(System::Object^ sender, System::EventArgs^ e) { Linkage* m_pLink = new Linkage(); ..... } However this produces errors: Error 4 error LNK2005: "private: static unsigned int const boost::detail::type_with_alignment_imp<4>::found" (?found@?$type_with_alignment_imp@$03@detail@boost@@$$Q0IB) already defined in Proj_Test.obj Linkage.obj ..... Error 7 fatal error LNK1169: one or more multiply defined symbols found Could anyone explain to me pls? Thanks.

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• WPF Binding : Object in a object

  - by Philippe

  I have a form in WPF with 2 textbox : <TextBox Name="txtName" Text="{Binding Contact.Name}"/> <TextBox Name="txtAddressNumber" Text="{Binding Contact.Address.Number}"/> and I have 2 class : public class ContactEntity { public string Name {get;set;} public AddressEntity Address {get;set;} } public class AddressEntity { public int Number {get;set} } The Name property binds fine. But the Number property of the Address object inside the Contact object does not binds. What I'm doing wrong ?

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• What is the difference between "data hiding" and "encapsulation"?

  - by Software Engeneering Learner

  I'm reading "Java concurrency in practice" and there is said: "Fortunately, the same object-oriented techniques that help you write well-organized, maintainable classes - such as encapsulation and data hiding -can also help you create thread-safe classes." The problem #1 - I never heard about data hiding and don't know what it is. The problem #2 - I always thought that encapsulation is using private vs public, and is actually the data hiding. Can you please explain what data hiding is and how it differs from encapsulation?

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• Are UML class diagrams adequate to design javascript systems?

  - by Vandell

  Given that UML is oriented towards a more classic approach to object orientation, is it still usable in a reliable way to design javascript systems? One specific problem that I can see is that class diagrams are, in fact, a structural view of the system, and javascript is more behaviour driven, how can you deal with it? Please, keep in mind that I'm not talking abot the real world domain here, It's a model for the solution that I'm trying to achieve.

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• Is there a way to avoid type-checking in this scenario?

  - by Prog

  I have a class SuperClass with two subclasses SubClassA and SubClassB. I have a method in a different class which takes a SuperClass parameter. The method should do different things depending on the type of the object it receives. To illustrate: public void doStuff(SuperClass object){ // if the object is of type SubClassA, do something. // if it's of type SubClassB, do something else. } I want to avoid type-checking (i.e. instanceof) because it doesn't feel like proper OO design. But I can't figure out how to employ Polymorphism to elegantly solve this problem. How can I solve this problem elegantly?

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• Returning a local object from a function

  - by pocoa

  Is this the right way to return an object from a function? Car getCar(string model, int year) { Car c(model, year); return c; } void displayCar(Car &car) { cout << car.getModel() << ", " << car.getYear() << endl; } displayCar(getCar("Honda", 1999)); I'm getting an error, "taking address of temporary". Should I use this way: Car &getCar(string model, int year) { Car c(model, year); return c; }

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• PHP Value Object auto create

  - by JonoB

  Assume that I have a class value object defined in php, where each variable in the class is defined. Something like: class UserVO { public $id; public $name; } I now have a function in another class, which is expecting an array ($data). function save_user($data) { //run code to save the user } How do I tell php that the $data parameter should be typed as a UserVO? I could then have code completion to do something like: $something = $data->id; //typed as UserVO.id $else = $data->name; //typed as UserVO.name I'm guessing something like the following, but this obviously doesnt work $my_var = $data as new userVO();

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• Creating Objects

  - by user1424667

  I have a general coding standard question. Is it bad practice to initialize and create an object in multiple methods depending on the outcome of a users choice. So for example if the user quits a poker game, create the poker hand with the cards the user has received, even if < 5, and if the user played till the end create object to show completed hand to show outcome of the game. The key is that the object will only be created once in actuality, there are just different paths and parameters is will receive depending on if the user folded, or played on to the showdown.

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• JSP Problem ussing implicit object (session) in a function

  - by user234666

  Can the object of type HttpSession called session be accessed from a function? In a simple jsp page I have a function(see below) defined in the header of the page, and set to an onclick handle of for a button. When I press this button, I'll never see the second alert message. If I do something in the body of the page (like Session ID: <%= session.getId() % ) I have no trouble accessing it. What newbie mistake am I making? function doTest() { alert('Preforming test 122333232'); String sessionId = session.getId(); alert('After access'); if(sessionId == null) { alert('session id is null?'); } Thanks

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• How to replace an object in an NSMutableArray at a given index with a new object

  - by shakeelw

  Hi guys. I have an NSMutableArray object(retained, synthesized as all) that is initiated just fine and I can easily add objects to it using the 'addObject:' method. But if I want to replace an object at a certain index with a new one in that NSMutableArray, it doesn't work. For example: ClassA.h @interface ClassA : NSObject { NSMutableArray *list; } @property (nonatomic, copy, readwrite) NSMutableArray *list; end ClassA.m import "ClassA.h" @implementation ClassA @synthesize list; (id)init { [super init]; NSMutableArray *localList = [[NSMutableArray alloc] init]; self.list = localList; [localList release]; //Add initial data [list addObject:@"Hello "]; [list addObject:@"World"]; } // Custom set accessor to ensure the new list is mutable (void)setList:(NSMutableArray *)newList { if (list != newList) { [list release]; list = [newList mutableCopy]; } } -(void)updateTitle:(NSString *)newTitle:(NSString *)theIndex { int i = [theIndex intValue]-1; [self.list replaceObjectAtIndex:i withObject:newTitle]; NSLog((NSString *)[self.list objectAtIndex:i]); // gives the correct output } However, the change remains true only inside the method. from any other method, the NSLog((NSString *)[self.list objectAtIndex:i]); gives the same old value. How can I actually get the old object replaced with the new one at a specific index so that the change can be noticed from within any other method as well. I even modified the method like this, but the result is the same: -(void)updateTitle:(NSString *)newTitle:(NSString *)theIndex { int i = [theIndex intValue]-1; NSMutableArray *localList = [[NSMutableArray alloc] init]; localList = [localList mutableCopy]; for(int j = 0; j < [list count]; j++) { if(j == i) { [localList addObject:newTitle]; NSLog(@"j == 1"); NSLog([NSString stringWithFormat:@"%d", j]); } else { [localList addObject:(NSString *)[self.list objectAtIndex:j]]; } } [self.list release]; //self.list = [localList mutableCopy]; [self setList:localList]; [localList release]; } Please help out guys :)

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• Output of System.out.println(object)

  - by Shaarad Dalvi

  I want to know what exactly the output tells when I do the following : class data { int a=5; } class main { public static void main(String[] args) { data dObj=new data(); System.out.println(dObj); } } I know it gives something related to object as the output in my case is data@1ae73783. I guess the '1ae73783' is a hex number. I also did some work around and printed System.out.println(dObj.hashCode()); I got number 415360643. I got an integer value. I don't know what hashCode() returns, still out of curiosity, when I converted 1ae73783 to decimal, I got 415360643! That's why I am curious that what exactly is this number?? Is this some memory location of Java's sandbox or some other thing? Any light on this matter will be helpful..thanks! :)

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• How to print object data in javascript

  - by rxzhang

  I have the following object data: var response = { "response": { "numFound": 7945, "docs": [{ "description": "target", "url": "target", "id": "269653", "score": 6.9186745 }, { "description": "Target Kent", "url": "Target_Kent", "id": "37275", "score": 4.3241715 }] }, "highlighting": { "269653": { "description": ["<em>target</em>"] }, "37275": { "description": ["<em>Target</em> Kent"] } } }; I can use response.response.docs[0].description to print out "target". But I don't know how to print out "<em>target</em>". Thanks.

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• Passing class names or objects?

  - by nischayn22

  I have a switch statement switch ( $id ) { case 'abc': return 'Animal'; case 'xyz': return 'Human'; //many more } I am returning class names,and use them to call some of their static functions using call_user_func(). Instead I can also create a object of that class, return that and then call the static function from that object as $object::method($param) switch ( $id ) { case 'abc': return new Animal; case 'xyz': return new Human; //many more } Which way is efficient? To make this question broader : I have classes that have mostly all static methods right now, putting them into classes is kind of a grouping idea here (for example the DB table structure of Animal is given by class Animal and so for Human class). I need to access many functions from these classes so the switch needs to give me access to the class

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