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• How to REALLY start thinking in terms of objects?

  - by Mr Grieves

  I work with a team of developers who all have several years of experience with languages such as C# and Java. Most of them are young enough to have been shown OOP as a standard way to develop software in university and are very comfortable with concepts such as inheritance, abstraction, encapsulation and polymorphism. Yet, many of them, and I have to include myself, still tend to create classes which are meant to be used in a very functional fashion. The resulting software is often several smaller classes which correctly represent business objects which get passed through larger classes which only supply ways to modify and use those objects (functions). Large complex difficult-to-maintain classes named Manager are usually the result of such behaviour. I can see two theoretical reasons why people might write this type of code: It's easy to start thinking of everything in terms of the database Deep down, for me, a computer handling a web request feels more like a functional operation than an object oriented operation when you think about Request Handlers, Threads, Processes, CPU Cores and CPU operations... I want source code which is easy to read and easy to modify. I have seen excellent examples of OO code which meet these objectives. How can I start writing code like this? How I can I really start thinking in an object oriented fashion? How can I share such a mentality with my colleagues?

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• What is the best approach to solve a factory method problem which has to be an instance?

  - by Iago

  I have to add new funcionality in a web service legacy project and I'm thinking what is the best approach for a concrete situation. The web service is simple: It receives a XML file, unmarshalling, generates response's objects, marshalling and finally it sends the response as a XML file. For every XML files received, the web service always responds with the same XML structure. What I have to do is to generate a different XML file according to the XML received. So I have a controller class which has all marshalling/unmarshalling operations, but this controller class has to be an instance. Depending on XML received I need some marshalling methods or others. Trying to make few changes on legacy source, what is the best approach? My first approach was to do a factory method pattern with the controller class, but this class has to be an instance. I want to keep, as far as it goes, this structure: classController.doMarshalling(); I think this one is a bit smelly: if(XMLReceived.isTypeOne()) classController.doMarshallingOne(); else if(XMLReceived.isTypeTwo()) classController.doMarshallingTwo(); else if(XMLReceived.isTypeThree()) classController.doMarshallingThree(); else if ... I hope my question is well understood

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• My Only Gripe With Programming

  - by David Espejo

  Is that im having trouble practicing problems. Even if I decide to practice the problems from my C++ book, they dont give any idea of the way the solution(program) should look like, so that I may compare to see if my program is similar in anyway. My book gives me to many generic "Write a program to do "this" " projects without really showing a concrete example of what "this" really is. In other words How Do I Know That I did "that". One problem in my book said to write a program that calculates the sales tax on a given item????? First of all slase tax differs on state(whats the state,) whats the item(a house, a dog,) How can I check this to see if im right. Programming books dont have answer keys! I know that there is no ABSOLUTE answer, thats just silly, programs can be written in many ways, but a sample of what one would look like based of the difficulty of the problem would really help! Is there a solution to this, maby a book that has worked out examples for the problems they give , or online sources that do something similar.(is there such thing as a programming book with an answer key?)

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• Optimal communication pattern to update subscribers

  - by hpc

  What is the optimal way to update the subscriber's local model on changes C on a central model M? ( M + C - M_c) The update can be done by the following methods: Publish the updated model M_c to all subscribers. Drawback: if the model is big in contrast to the change it results in much more data to be communicated. Publish change C to all subscribes. The subscribers will then update their local model in the same way as the server does. Drawback: The client needs to know the business logic to update the model in the same way as the server. It must be assured that the subscribed model stays equal to the central model. Calculate the delta (or patch) of the change (M_c - M = D_c) and transfer the delta. Drawback: This requires that calculating and applying the delta (M + D_c = M_c) is an cheap/easy operation. If a client newly subscribes it must be initialized. This involves sending the current model M. So method 1 is always required. Think of playing chess as a concrete example: Subscribers send moves and want to see the latest chess board state. The server checks validity of the move and applies it to the chess board. The server can then send the updated chessboard (method 1) or just send the move (method 2) or send the delta (method 3): remove piece on field D4, put tower on field D8.

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• Is there a typical career path to learn game development "on the job"?

  - by mac

  The extended version of the question is: what is the typical career paths that a developer without specific experience in game development should take if he/she wishes to work in the game development industry? In other words, what are the positions such a programmer might aspire to get hired for, in the game industry? I am asking because it seems to me that - even without direct experience with 3D modelling, physics engines, shaders, etc... - for as much complex as these topics might be - they are still "just" top layers one can learn "on the job" if he/she has already good programming skills and experience in software design (for example during peer-programming sessions). I have no knowledge whatsoever of the game industry, so maybe I am being naïve here, but for all the other programming jobs I previously took, I learnt most of the specificities while working on concrete projects... so I wonder if there is a chance to do the same with game development. Thanks for your time and advice! :) PS: I don't know if this is important or not for answering the question, but scripting languages are the languages I am more proficient in. /mac

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• Should all public methods in an abstract class be marked virtual?

  - by Justin Pihony

  I recently had to update an abstract base class on some OSS that I was using so that it was more testable by making them virtual (I could not use an interface as it combined two). This got me thinking whether I should mark all of the methods that I needed virtual, or if I should mark every public method/property virtual. I generally agree with Roy Osherove that every method should be made virtual, but I came across this article that got me thinking about whether this was necessary or not. I am going to limit this down to abstract classes for simplicity, however (whether all concrete public methods should be virtual is especially debatable, I am sure). I could see where you might want to allow a sub-class to use a method, but not want it overriding the implementation. However, as long as you trust that Liskov's Substitution Principle will be followed, then why would you not allow it to be overriden? By marking it abstract, you are forcing a certain override anyway, so, it seems to me that all public methods inside of an abstract class should indeed be marked virtual. However, I wanted to ask in case there was something I might not be thinking. Should all public methods within an abstract class be made virtual?

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• The Power of Specialization – google ads for SOA & BPM Specialized Partners

  - by JuergenKress

  For SOA & BPM specialized partner we offer free google advertisement to promote your Oracle SOA & BPM service offerings on your website or your SOA & BPM events. We will host the complete campaign management. To create your google campaign please send us below: Your campaign text: 3 lines of text each 35 letters (NOT more letters!) Your campaign link: direct link to the website you want to promote Ideas for the website which we will promote with the google ads: Your Oracle SOA Service offerings with concrete offering e.g. SOA Discovery Workshop Oracle SOA Specialized Logo Your Oracle SOA References Your SOA Implementation consultant with pictures Your SOA sales contact persons Example of an SOA Specialization text ad: Oracle SOA Specialized plan to become more agile? eProseed the Oracle SOA Experts An interview with Griffiths Waite's Business Development Director highlighting the benefits of the Oracle Specialization Programme. SOA & BPM Partner Community For regular information on Oracle SOA Suite become a member in the SOA & BPM Partner Community for registration please visit  www.oracle.com/goto/emea/soa (OPN account required) If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Technorati Tags: Specializaion,Benefits Specialization,marketing,SOA Community,Oracle SOA,Oracle BPM,Community,OPN,Jürgen Kress

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• Obtain reference to Parent object during instantiation

  - by GoldBishop

  I have a situation where a custom class is a property of another class. What i need to be able to do, if it is possible at all, is obtain a reverse to the "parent" class (ie the the class that holds the current class as a property). For Instance: Public Class Class1 ... public readonly property Prop11 as Class2 public property Prop12 as String ... End Class Public Class Class2 ... private _par as Class1 private _var21 as string ... Public Sub New(...) me._par = ???? ... End Sub public readonly property Prop21 as string Get return me._par.Prop12 & me._var21 End Get End Property ... End Class Ultimately, i am trying to access other properties within Class1 from Class2 as they do have substance for information from within Class2. There are several other classes within Class1 that provide descriptive information to other classes contained within it as properties but the information is not extensible to all of the classes through Inheritance, as Class1 is being used as a resource bin for the property classes and the application itself. Diagram, lazy design ;): Application <- Class1.Prop12 Application <- Class1.Prop11.Prop21 Question: Is it possible to get a recursion through this design setup?

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• How do Unity 12.04/Compiz bindings really work?

  - by Daniel

  There is a bewildering array of places to set bindings, all inconsistent with one another. E.g. in Unity's System Settings having the Ctrl-key highlight the mouse position is an on/off choice. I like the feature, but not on such a prominent key where I keep activating it accidentally. The keyboard shortcuts allow only one binding per command, where I might like a convenient one on the external keyboard and an emergency alternative for when I'm on the road. Keyboard custom shortcuts has a nice interface, but allows only key bindings — besides it doesn't seem to work for me. So I activated CCSM Commands. There I have the choice of key-, mouse- and/or edge bindings. Whereas some places in CCSM offers only one or two of these binding possibilities, randomly at the whim of the programmer. I have not found a way to differentiate a mouse-drag from a click. E.g. I want <SuperMouse1-drag anywhere on a window to move it, while if I don't drag, it should be raise-lower. On the title bar I want the same without needing the <Super key. Now I find raise-lower only in System Settings where I can't assign a mouse binding. If therefore in CCSM I fallback to only lower and put move on the same binding, the window already gets lowered on mouse down, and I can then invisibly move it. Very useful! I have <Altasciicircum get in the way of an Emacs binding, with some to me useless popup overlay. I can find it nowhere, so I can't turn it off. So how can I go without these frontends until they have matured, and instruct Compiz directly, for example in the way Emacs or Sawfish have keymaps, and separate ones for each context, with inheritance?

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• SQL language drawbacks, The Third Manifesto

  - by David Portabella

  Sometime ago I read about SQL language drawbacks (the basic language specification, not vendor specific), and one of the drawbacks was that the language does not allow to create a set of tuples that don't come from a table. For instance, SELECT firstName, lastName from people; this creates a set of tuples coming from the table people. Now, if I don't have this table people, and I want to return a constant, I'd need something like this to return a set of two tuples (this would not require to have a table): SELECT VALUES('james', 'dean'), ('tom', 'cruisse'); Why I would need that? Because of the same reasons that we can define constants (not only basic types, but objects and arrays also) in any advanced programming language. Workarounds, Yes, I could create a temporal table, fill the data, and SELECT from that table. This is a hack, to overcome the drawbacks of the poor SQL language. I think that I read about this somewhere in "The Third Manifesto", but I don't find the paragraph/example talking about this concrete drawback anymore. Do you know a reference about it?

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• TCO Models: Oracle invites you to the next webcast dedicated to Partners on Oracle Hardware and Solutions

  - by mseika

  The Oracle Hardware and Solutions Webcast Series is a sequence of one-hour Sales-Oriented Web Seminars, dedicated to Oracle Partners. This is your opportunity to learn about Oracle's Servers, Storage and Solutions strategy and portfolio, and their business value for you and your customers. The next appointment is for Wednesday, June 22, at 9am UKT / 10am CET:Total Cost of Ownership Models Examples: How we can sell Oracle HW and SW together, with better TCO, and benefits for both Oracle and the Partner!with Ilkka Vanhanen, Business Development Manager, Oracle EMEA Hardware Strategy Organization, who will talk about:   Concrete examples of the HW/SW TCO Model   Understand the competitive advantage provided by Oracle-on-Oracle Solutions   How Partners get new business from Oracle-on-Oracle Solutions   How Oracle is changing the game in Enterprise IT   Key benefits for both SW Resellers and HW Resellers   To register click here , then click on the “Servers and Solutions Webcasts” tab.          

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• How far do I take Composition?

  - by whiterook6

  (Although I'm sure this is a common problem I really don't know what to search for. Composition is the only thing I could come up with.) I've read over and over that multiple inheritance and subclassing is really, really bad, especially for game entities. If I have three types of motions, five types of guns, and three types of armoring, I don't want to have to make 45 different classes to get all the possible combinations; I'm going to add a motion behavior, gun behavior, and armor behavior to a single generic object. That makes sense. But how far do I take this? I can have as many different types of behaviors as I can imagine: DamageBehavior, MotionBehavior, TargetableBehavior, etc. If I add a new class of behaviors then I need to update all the other classes that use them. But what happens when I have functionality that doesn't really fit into one class of behaviors? For example, my armor needs to be damageable but also updateable. And should I be able to have use more than one type of behavior on an entity at a time, such as two motion behaviors? Can anyone offer any wisdom or point me in the direction of some useful articles? Thanks!

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• FP for simulation and modelling

  - by heaptobesquare

  I'm about to start a simulation/modelling project. I already know that OOP is used for this kind of projects. However, studying Haskell made me consider using the FP paradigm for modelling a system of components. Let me elaborate: Let's say I have a component of type A, characterised by a set of data (a parameter like temperature or pressure,a PDE and some boundary conditions,etc.) and a component of type B, characterised by a different set of data(different or same parameter, different PDE and boundary conditions). Let's also assume that the functions/methods that are going to be applied on each component are the same (a Galerkin method for example). If I were to use an OOP approach, I would create two objects that would encapsulate each type's data, the methods for solving the PDE(inheritance would be used here for code reuse) and the solution to the PDE. On the other hand, if I were to use an FP approach, each component would be broken down to data parts and the functions that would act upon the data in order to get the solution for the PDE. This approach seems simpler to me assuming that linear operations on data would be trivial and that the parameters are constant. What if the parameters are not constant(for example, temperature increases suddenly and therefore cannot be immutable)? In OOP, the object's (mutable) state can be used. I know that Haskell has Monads for that. To conclude, would implementing the FP approach be actually simpler,less time consuming and easier to manage (add a different type of component or new method to solve the pde) compared to the OOP one? I come from a C++/Fortran background, plus I'm not a professional programmer, so correct me on anything that I've got wrong.

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• A few questions about how JavaScript works

  - by KayoticSully

  I originally posted on Stack Overflow and was told I might get some better answers here. I have been looking deeply into JavaScript lately to fully understand the language and have a few nagging questions that I can not seem to find answers to (Specifically dealing with Object Oriented programming. I know JavaScript is meant to be used in an OOP manner I just want to understand it for the sake of completeness). Assuming the following code: function TestObject() { this.fA = function() { // do stuff } this.fB = testB; function testB() { // do stuff } } TestObject.prototype = { fC : function { // do stuff } } What is the difference between functions fA and fB? Do they behave exactly the same in scope and potential ability? Is it just convention or is one way technically better or proper? If there is only ever going to be one instance of an object at any given time, would adding a function to the prototype such as fC even be worthwhile? Is there any benefit to doing so? Is the prototype only really useful when dealing with many instances of an object or inheritance? And what is technically the "proper" way to add methods to the prototype the way I have above or calling TestObject.prototype.functionName = function(){} every time? I am looking to keep my JavaScript code as clean and readable as possible but am also very interested in what the proper conventions for Objects are in the language. I come from a Java and PHP background and am trying to not make any assumptions about how JavaScript works since I know it is very different being prototype based. Also are there any definitive JavaScript style guides or documentation about how JavaScript operates at a low level? Thanks!

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• Two components offering the same functionality, required by different dependencies

  - by kander

  I'm building an application in PHP, using Zend Framework 1 and Doctrine2 as the ORM layer. All is going well. Now, I happened to notice that both ZF1 and Doctrine2 come with, and rely on, their own caching implementation. I've evaluated both, and while each has its own pro's and cons, neither of them stand out as superior to the other for my simple needs. Both libraries also seem to be written against their respective interfaces, not their implementations. Reasons why I feel this is an issue is that during the bootstrapping of my application, I have to configure two caching drivers - each with its own syntax. A mismatch is easily created this way, and it feels inefficient to set up two connections to the caching backend because of this. I'm trying to determine what the best way forward is, and would welcome any insights you may be able to offer. What I've thought up so far are four options: Do nothing, accept that two classes offering caching functionality are present. Create a Facade class to stick Zend's interface onto Doctrine's caching implementation. Option 2, the other way around - create a Facade to map Doctrine's interface on a Zend Framework backend. Use multiple-interface-inheritance to create one interface to rule them all, and pray that there aren't any overlaps (ie: if both have a "save" method, they'll need to accept params in the same order due to PHP's lack of proper polymorphism). What option is best, or is there a "None of the above" variant that I'm not aware of?

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• How do I troubleshoot system slowness seen when viewing PDFs or videos?

  - by asp

  Whenever I watch videos, either online of local via Totem and/or open PDF files using evince. The system gets really, really bogged down. All apps get really slow, menus take forever to display, switching windows gives me time to make a coffee, etc. I have a couple of bug reports open on this, but what do I need to do to really troubleshoot the issue? I've purged Adobe Flash from the system, but YouTube HTML5 videos still have the issue. A bunch of PDFs saved locally trigger the problem. And to (temporarily) remove the slowness, I need to shutdown the computer, breath for a few minutes, then restart. A simple reboot does not do the trick. How can I identify the cause? This only started on 13.04. I've had Ubuntu on this machine for a year without a problem until "upgrading" to 13.04. I am not a programmer, but I suspect an issue with the Intel video driver. Is there something I can run which will diagnose this, or are there concrete steps I can follow to find the culprit?

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• @staticmethod vs module-level function

  - by darkfeline

  This is not about @staticmethod and @classmethod! I know how staticmethod works. What I want to know is the proper use cases for @staticmethod vs. a module-level function. I've googled this question, and it seems there's some general agreement that module-level functions are preferred over static methods because it's more pythonic. Static methods have the advantage of being bound to its class, which may make sense if only that class uses it. However, in Python functionality is usually organized by module not class, so usually making it a module function makes sense too. Static methods can also be overridden by subclasses, which is an advantage or disadvantage depending on how you look at it. Although, static methods are usually "functionally pure" so overriding it may not be smart, but it may be convenient sometimes (though this may be one of those "convenient, but NEVER DO IT" kind of things only experience can teach you). Are there any general rule-of-thumbs for using either staticmethod or module-level functions? What concrete advantages or disadvantages do they have (e.g. future extension, external extension, readability)? If possible, also provide a case example.

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• Interfaces on an abstract class

  - by insta

  My coworker and I have different opinions on the relationship between base classes and interfaces. I'm of the belief that a class should not implement an interface unless that class can be used when an implementation of the interface is required. In other words, I like to see code like this: interface IFooWorker { void Work(); } abstract class BaseWorker { ... base class behaviors ... public abstract void Work() { } protected string CleanData(string data) { ... } } class DbWorker : BaseWorker, IFooWorker { public void Work() { Repository.AddCleanData(base.CleanData(UI.GetDirtyData())); } } The DbWorker is what gets the IFooWorker interface, because it is an instantiatable implementation of the interface. It completely fulfills the contract. My coworker prefers the nearly identical: interface IFooWorker { void Work(); } abstract class BaseWorker : IFooWorker { ... base class behaviors ... public abstract void Work() { } protected string CleanData(string data) { ... } } class DbWorker : BaseWorker { public void Work() { Repository.AddCleanData(base.CleanData(UI.GetDirtyData())); } } Where the base class gets the interface, and by virtue of this all inheritors of the base class are of that interface as well. This bugs me but I can't come up with concrete reasons why, outside of "the base class cannot stand on its own as an implementation of the interface". What are the pros & cons of his method vs. mine, and why should one be used over another?

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• Web dev/programmer with 4.5 yrs experience. Better for career: self-study or master's degree? [closed]

  - by Anonymous Programmer

  I'm a 28 year-old web developer/programmer with 4.5 years of experience, and I'm looking to jump-start my career. I'm trying to decide between self-study and a 1-year master's program in CS at a top school. I'm currently making 65K in a high cost-of-living area that is NOT a hot spot for technology firms. I code almost exclusively in Ruby/Rails, PHP/CodeIgniter, SQL, and JavaScript. I've slowly gained proficiency with Git. Roughly half the time I am architecting/coding, and half the time I am pounding out HTML/CSS for static brochureware sites. I'd like to make more more money while doing more challenging/interesting work, but I don't know where to start. I have an excellent academic record (math major with many CS credits, 3.9+ GPA), GRE scores, and recommendations, so I am confident that I could be admitted to a great CS master's program. On the other hand, there is the tuition and opportunity cost to consider. I feel like there are a number of practical languages/tools/skills worth knowing that I could teach myself - shell scripting, .NET, Python, Node.js, MongoDB, natural language processing techniques, etc. That said, it's one thing to read about a subject and another thing to have experience with it, which structured coursework provides. So, on to the concrete questions: What programming skills/knowledge should I develop to increase my earning potential and make me competitive for more interesting jobs? Will a master's degree in CS from a top school help me develop the above skills/knowledge, and if so, is it preferable to self-study (possibly for other reasons, e.g., the degree's value as a credential)?

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• How do you plan your asynchronous code?

  - by NullOrEmpty

  I created a library that is a invoker for a web service somewhere else. The library exposes asynchronous methods, since web service calls are a good candidate for that matter. At the beginning everything was just fine, I had methods with easy to understand operations in a CRUD fashion, since the library is a kind of repository. But then business logic started to become complex, and some of the procedures involves the chaining of many of these asynchronous operations, sometimes with different paths depending on the result value, etc.. etc.. Suddenly, everything is very messy, to stop the execution in a break point it is not very helpful, to find out what is going on or where in the process timeline have you stopped become a pain... Development becomes less quick, less agile, and to catch those bugs that happens once in a 1000 times becomes a hell. From the technical point, a repository that exposes asynchronous methods looked like a good idea, because some persistence layers could have delays, and you can use the async approach to do the most of your hardware. But from the functional point of view, things became very complex, and considering those procedures where a dozen of different calls were needed... I don't know the real value of the improvement. After read about TPL for a while, it looked like a good idea for managing tasks, but in the moment you have to combine them and start to reuse existing functionality, things become very messy. I have had a good experience using it for very concrete scenarios, but bad experience using them broadly. How do you work asynchronously? Do you use it always? Or just for long running processes? Thanks.

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• The Power of Specialization &ndash; google ads for WebLogic Specialized Partners

  - by JuergenKress

  For WebLogic specialized partner we offer free google advertisement to promote your Oracle WebLogic service offerings on your website or your WebLogic events. We will host the complete campaign management. To create your google campaign please send Jürgen Kress below: Your campaign text: 3 lines of text each 35 letters (NOT more letters!) Your campaign link: direct link to the website you want to promote Ideas for the website which we will promote with the google ads: Your Oracle WebLogic Service offerings with concrete offering e.g. WebLogic Innovation Workshop Oracle WebLogic Specialized Logo Your Oracle WebLogic References Your WebLogic Implementation consultant with pictures Your WebLogic sales contact persons Example of an WebLogic Specialization text ad: Oracle SOA Specialized plan to become more agile? eProseed the Oracle SOA Experts An interview with Griffiths Waite's Business Development Director highlighting the benefits of the Oracle Specialization Programme. WebLogic Partner Community For regular information become a member in the WebLogic Partner Community please visit: http://www.oracle.com/partners/goto/wls-emea ( OPN account required). If you need support with your account please contact the Oracle Partner Business Center. BlogTwitterLinkedInMixForumWiki Technorati Tags: Specialization,Google ads,Specialization benefits,WebLogic Specialization,WebLogic Community,Oracle,OPN,Jürgen Kress

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• Classes as a compilation unit

  - by Yannbane

  If "compilation unit" is unclear, please refer to this. However, what I mean by it will be clear from the context. Edit: my language allows for multiple inheritance, unlike Java. I've started designing+developing my own programming language for educational, recreational, and potentially useful purposes. At first, I've decided to base it off Java. This implied that I would have all the code be written inside classes, and that code compiles to classes, which are loaded by the VM. However, I've excluded features such as interfaces and abstract classes, because I found no need for them. They seemed to be enforcing a paradigm, and I'd like my language not to do that. I wanted to keep the classes as the compilation unit though, because it seemed convenient to implement, familiar, and I just liked the idea. Then I noticed that I'm basically left with a glorified module system, where classes could be used either as "namespaces", providing constants and functions using the static directive, or as templates for objects that need to be instantiated ("actual" purpose of classes in other languages). Now I'm left wondering: what are the benefits of having classes as compilation units? (Also, any general commentary on my design would be much appreciated.)

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• So You Want To Build a SPARC Cloud

  - by user12601629

  Did you ever wish you could get the industrial strength power of UNIX/RISC with the flexibility of cloud computing?  Well, now you can!  With recent advances from Oracle it's possible to build an incredibly high-performance, flexible, available virtualized infrastructure based on Solaris and SPARC.  Here's the recipe! Authored in collaboration across the Oracle "Systems Group" team, we now have a complete best practice guide for you.  Click below to download it: Best Practices for Building a Virtualized SPARC Computing Environment Inside you'll find recommendations for how and when to leverage technologies like: SPARC T4 OVM for SPARC hypervisor (version 2.2 and newer) Solaris 11 Ops Center 12c ZFS Storage Appliance Oracle network switches Based on following these best practices, you'll be able to construct a dynamic, virtualized infrastructure that allows for: Easy, GUI-based provisioning on new VMs Automated HA failover in the event of physical server failures Automatic load balancing across a cluster of VM hosts Complete end-to-end monitoring You should download this paper and check it out.  Even if you aren't planning on buying all new hardware, and instead want to transform some existing gear into a dynamic virtualized environment then this paper will give you concrete info on what to do and the trade-offs you'll make. Have fun getting started on your journey to build a SPARC cloud!

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• Could a singleton type replace static methods and classes?

  - by MKO

  In C# Static methods has long served a purpose allowing us to call them without instantiating classes. Only in later year have we became more aware of the problems of using static methods and classes. They can’t use interfaces They can’t use inheritance They are hard to test because you can’t make mocks and stubs Is there a better way ? Obviously we need to be able to access library methods without instantiated classes all the time otherwise our code would become pretty cluttered One possibly solution is to use a new keyword for an old concept: the singleton. Singleton’s are global instances of a class, since they are instances we can use them as we would normal classes. In order to make their use nice and practical we'd need some syntactic sugar however Say that the Math class would be of type singleton instead of an actual class. The actual class containing all the default methods for the Math singleton is DefaultMath, which implements the interface IMath. The singleton would be declared as singleton Math : IMath { public Math { this = new DefaultMath(); } } If we wanted to substitute our own class for all math operations we could make a new class MyMath that inherits DefaultMath, or we could just inherit from the interface IMath and create a whole new Class. To make our class the active Math class, you'd do a simple assignment Math = new MyMath(); and voilá! the next time we call Math.Floor it will call your method. Note that for a normal singleton we'd have to write something like Math.Instance.Floor but the compiler eliminates the need for the Instance property Another idea would be to be able to define a singletons as Lazy so they get instantiated only when they're first called, like lazy singleton Math : IMath What do you think, would it have been a better solution that static methods and classes? Is there any problems with this approach?

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• How to quickly search through a very large list of strings / records on a database

  - by Giorgio

  I have the following problem: I have a database containing more than 2 million records. Each record has a string field X and I want to display a list of records for which field X contains a certain string. Each record is about 500 bytes in size. To make it more concrete: in the GUI of my application I have a text field where I can enter a string. Above the text field I have a table displaying the (first N, e.g. 100) records that match the string in the text field. When I type or delete one character in the text field, the table content must be updated on the fly. I wonder if there is an efficient way of doing this using appropriate index structures and / or caching. As explained above, I only want to display the first N items that match the query. Therefore, for N small enough, it should not be a big issue loading the matching items from the database. Besides, caching items in main memory can make retrieval faster. I think the main problem is how to find the matching items quickly, given the pattern string. Can I rely on some DBMS facilities, or do I have to build some in-memory index myself? Any ideas? EDIT I have run a first experiment. I have split the records into different text files (at most 200 records per file) and put the files in different directories (I used the content of one data field to determine the directory tree). I end up with about 50000 files in about 40000 directories. I have then run Lucene to index the files. Searching for a string with the Lucene demo program is pretty fast. Splitting and indexing took a few minutes: this is totally acceptable for me because it is a static data set that I want to query. The next step is to integrate Lucene in the main program and use the hits returned by Lucene to load the relevant records into main memory.

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