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• Verification of UML Class Diagram

  - by Jean Carlos Suárez Marranzini

  This is my UML Class Diagram made in Astah Community, for a tennis scoreboard game. Here's a link to the image (I don't have enough rep to post images): http://i47.tinypic.com/2lsxx90.png Points are calculated based on moves. Moves can be either points (for the player's advantage) or errors (for the opponent's advantage). The Time Machine allows you to travel to previous game states (expressed as scoreboards). The storage component should be able to store matches independently of the serialization format. The serializers and deserializers should be able to do their job regardless of where the storage lies. The GameEngine should be able to apply the rules of the game regardless of the particularities of the game (hence, dependency injection through the Settings class). The outcomes of games, sets and matches should be deducible based on the points and the rules to apply (the logic implementations are there to provide the rules). Could you please verify my design and tell me if there's anything wrong with it? Thanks in advance.

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• Class as first-class object

  - by mrpyo

  Could a class be a first-class object? If yes, how would the implementation look? I mean, how could syntax for dynamically creating new classes look like? EDIT: I mean what example syntax could look like (I'm sorry, English is not my native language), but still I believe this question makes sense - how you give this functionality while keeping language consistent. For example how you create reference for new type. Do you make reference first-class object too and then use something like this: Reference<newType> r = new Reference<newType>(); r.set(value); Well this could get messy so you may just force user to use Object type references for dynamically created classes, but then you loose type-checking. I think creating concise syntax for this is interesting problem which solving could lead to better language design, maybe language which is metalanguage for itself (I wonder if this is possible).

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• Writing Acceptance test cases

  - by HH_

  We are integrating a testing process in our SCRUM process. My new role is to write acceptance tests of our web applications in order to automate them later. I have read a lot about how tests cases should be written, but none gave me practical advices to write test cases for complex web applications, and instead they threw conflicting principles that I found hard to apply: Test cases should be short: Take the example of a CMS. Short test cases are easy to maintain and to identify the inputs and outputs. But what if I want to test a long series of operations (eg. adding a document, sending a notification to another user, the other user replies, the document changes state, the user gets a notice). It rather seems to me that test cases should represent complete scenarios. But I can see how this will produce overtly complex test documents. Tests should identify inputs and outputs:: What if I have a long form with many interacting fields, with different behaviors. Do I write one test for everything, or one for each? Test cases should be independent: But how can I apply that if testing the upload operation requires that the connect operation is successful? And how does it apply to writing test cases? Should I write a test for each operation, but each test declares its dependencies, or should I rewrite the whole scenario for each test? Test cases should be lightly-documented: This principles is specific to Agile projects. So do you have any advice on how to implement this principle? Although I thought that writing acceptance test cases was going to be simple, I found myself overwhelmed by every decision I had to make (FYI: I am a developer and not a professional tester). So my main question is: What steps or advices do you have in order to write maintainable acceptance test cases for complex applications. Thank you.

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• Class DIagram Aggregation

  - by GigaPr

  Hi, i came across this definition Aggregation has two properties: antisymmetry, transitivity What does it mean? thanks

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• C++ class initialisation containing class variable initialization

  - by Phil Hannent

  I noticed some code of a colleague today that initialized class variables in the initialization. However it was causing a warning, he says because of the order they are in. My question is why is it better to do variable initialization where it currently is and not within the curly brackets? DiagramScene::DiagramScene( int slideNo, QRectF screenRect, MainWindow* parent ) : QGraphicsScene( screenRect, parent ), myParent( parent ), slideUndoImageCurrentIndex(-1), nextGroupID(0), m_undoInProgress(false), m_deleteItemOnNextUndo(0) line(0), path(0) { /* Setup default brush for background */ scDetail->bgBrush.setStyle(Qt::SolidPattern); scDetail->bgBrush.setColor(Qt::white); setBackgroundBrush(scDetail->bgBrush); }

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• Check if a class is subclass of another class in Java

  - by craesh

  Hi! I'm playing around with Java's reflection API and trying to handle some fields. Now I'm stuck with identifying the type of my fields. Strings are easy, just do myField.getType().equals(String.class). The same applies for other non-derived classes. But how do I check derived classes? E.g. LinkedList as subclass of List. I can't find any isSubclassOf(...) or extends(...) method. Do I need to walk through all getSuperClass() and find my supeclass by my own? Thanks! craesh

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• Static member class - declare class private and class member package-private?

  - by Helper Method

  Consider you have the following class public class OuterClass { ... private static class InnerClass { int foo; int bar; } } I think I've read somewhere (but not the official Java Tutorial) that if I would declare the static member classes attributes private, the compiler had to generate some sort of accessor methods so that the outer class can actually access the static member class's (which is effectively a package-private top level class) attributes. Any ideas on that?

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• XSD: how to use 'unique' & 'key'/'keyref' with element values?

  - by Koohoolinn

  I trying to use and / with element values but I just can't get it to work. If I do it with attrubute values it works like a charm. Test.xml <test:config xmlns:test="http://www.example.org/Test" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.example.org/Test Test.xsd "> <test:location id="id1" path="/path2"> <test:roles> <test:role>role1</test:role> <test:role>role2</test:role> <test:role>role2</test:role> <!-- DUPLICATE: FAIL VALIDATION --> </test:roles> <test:action name="action1"> <test:roles> <test:role>role1</test:role> <test:role>role1</test:role> <!-- DUPLICATE: FAIL VALIDATION --> <test:role>role3</test:role> <!-- NOT DEFINED: FAIL VALIDATION --> </test:roles> </test:action> </test:location> </test:config> I want ensure that roles are only defined once and that the roles defined under the action element are only those defined at the upper level. Test.xsd <xs:element name="config"> <xs:complexType> <xs:sequence> <xs:element ref="test:location" maxOccurs="unbounded" /> </xs:sequence> </xs:complexType> </xs:element> <xs:element name="location" type="test:LocationType"> <xs:key name="keyRole"> <xs:selector xpath="test:roles" /> <xs:field xpath="test:role" /> </xs:key> <xs:keyref name="keyrefRole" refer="test:keyRole"> <xs:selector xpath="test:action/test:roles" /> <xs:field xpath="test:role" /> </xs:keyref> </xs:element> <xs:complexType name="LocationType"> <xs:sequence> <xs:element ref="test:roles" minOccurs="0" /> <xs:element name="action" type="test:ActionType" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> <xs:attribute name="id" type="xs:string" use="required"/> <xs:attribute name="path" type="xs:string" use="required"/> </xs:complexType> <xs:element name="roles" type="test:RolesType"> <xs:unique name="uniqueRole"> <xs:selector xpath="." /> <xs:field xpath="test:role" /> </xs:unique> </xs:element> <xs:complexType name="RolesType"> <xs:sequence> <xs:element name="role" type="xs:string" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> <xs:complexType name="ActionType"> <xs:sequence> <xs:element ref="test:roles" /> </xs:sequence> <xs:attribute name="name" type="xs:string" use="required" /> </xs:complexType> The validation fails with these messages: Description Resource Path Location Type cvc-identity-constraint.3: Field "./test:role" of identity constraint "keyrefRole" matches more than one value within the scope of its selector; fields must match unique values. Test.xml /filebrowser-ejb/src/test/resources line 15 XML Problem cvc-identity-constraint.3: Field "./test:role" of identity constraint "keyrefRole" matches more than one value within the scope of its selector; fields must match unique values. Test.xml /filebrowser-ejb/src/test/resources line 16 XML Problem cvc-identity-constraint.3: Field "./test:role" of identity constraint "keyRole" matches more than one value within the scope of its selector; fields must match unique values. Test.xml /filebrowser-ejb/src/test/resources line 9 XML Problem cvc-identity-constraint.3: Field "./test:role" of identity constraint "keyRole" matches more than one value within the scope of its selector; fields must match unique values. Test.xml /filebrowser-ejb/src/test/resources line 10 XML Problem cvc-identity-constraint.3: Field "./test:role" of identity constraint "uniqueRole" matches more than one value within the scope of its selector; fields must match unique values. Test.xml /filebrowser-ejb/src/test/resources line 9 XML Problem cvc-identity-constraint.3: Field "./test:role" of identity constraint "uniqueRole" matches more than one value within the scope of its selector; fields must match unique values. Test.xml /filebrowser-ejb/src/test/resources line 10 XML Problem cvc-identity-constraint.3: Field "./test:role" of identity constraint "uniqueRole" matches more than one value within the scope of its selector; fields must match unique values. Test.xml /filebrowser-ejb/src/test/resources line 15 XML Problem cvc-identity-constraint.3: Field "./test:role" of identity constraint "uniqueRole" matches more than one value within the scope of its selector; fields must match unique values. Test.xml /filebrowser-ejb/src/test/resources line 16 XML Problem cvc-identity-constraint.4.1: Duplicate unique value [role1] declared for identity constraint "uniqueRole" of element "roles". Test.xml /filebrowser-ejb/src/test/resources line 9 XML Problem cvc-identity-constraint.4.1: Duplicate unique value [role1] declared for identity constraint "uniqueRole" of element "roles". Test.xml /filebrowser-ejb/src/test/resources line 15 XML Problem cvc-identity-constraint.4.2.2: Duplicate key value [role1] declared for identity constraint "keyRole" of element "location". Test.xml /filebrowser-ejb/src/test/resources line 9 XML Problem cvc-identity-constraint.4.3: Key 'keyrefRole' with value 'role3' not found for identity constraint of element 'location'. Test.xml /filebrowser-ejb/src/test/resources line 19 XML Problem If I comment out the lines that should fail, validation still fails now with these messages: Description Resource Path Location Type cvc-identity-constraint.3: Field "./test:role" of identity constraint "keyRole" matches more than one value within the scope of its selector; fields must match unique values. Test.xml /filebrowser-ejb/src/test/resources line 10 XML Problem cvc-identity-constraint.3: Field "./test:role" of identity constraint "uniqueRole" matches more than one value within the scope of its selector; fields must match unique values. Test.xml /filebrowser-ejb/src/test/resources line 10 XML Problem What am I doing wrong?

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• Testing Workflows &ndash; Test-First

  - by Timothy Klenke

  Originally posted on: http://geekswithblogs.net/TimothyK/archive/2014/05/30/testing-workflows-ndash-test-first.aspxThis is the second of two posts on some common strategies for approaching the job of writing tests.  The previous post covered test-after workflows where as this will focus on test-first.  Each workflow presented is a method of attack for adding tests to a project.  The more tools in your tool belt the better.  So here is a partial list of some test-first methodologies. Ping Pong Ping Pong is a methodology commonly used in pair programing.  One developer will write a new failing test.  Then they hand the keyboard to their partner.  The partner writes the production code to get the test passing.  The partner then writes the next test before passing the keyboard back to the original developer. The reasoning behind this testing methodology is to facilitate pair programming.  That is to say that this testing methodology shares all the benefits of pair programming, including ensuring multiple team members are familiar with the code base (i.e. low bus number). Test Blazer Test Blazing, in some respects, is also a pairing strategy.  The developers don’t work side by side on the same task at the same time.  Instead one developer is dedicated to writing tests at their own desk.  They write failing test after failing test, never touching the production code.  With these tests they are defining the specification for the system.  The developer most familiar with the specifications would be assigned this task. The next day or later in the same day another developer fetches the latest test suite.  Their job is to write the production code to get those tests passing.  Once all the tests pass they fetch from source control the latest version of the test project to get the newer tests. This methodology has some of the benefits of pair programming, namely lowering the bus number.  This can be good way adding an extra developer to a project without slowing it down too much.  The production coder isn’t slowed down writing tests.  The tests are in another project from the production code, so there shouldn’t be any merge conflicts despite two developers working on the same solution. This methodology is also a good test for the tests.  Can another developer figure out what system should do just by reading the tests?  This question will be answered as the production coder works there way through the test blazer’s tests. Test Driven Development (TDD) TDD is a highly disciplined practice that calls for a new test and an new production code to be written every few minutes.  There are strict rules for when you should be writing test or production code.  You start by writing a failing (red) test, then write the simplest production code possible to get the code working (green), then you clean up the code (refactor).  This is known as the red-green-refactor cycle. The goal of TDD isn’t the creation of a suite of tests, however that is an advantageous side effect.  The real goal of TDD is to follow a practice that yields a better design.  The practice is meant to push the design toward small, decoupled, modularized components.  This is generally considered a better design that large, highly coupled ball of mud. TDD accomplishes this through the refactoring cycle.  Refactoring is only possible to do safely when tests are in place.  In order to use TDD developers must be trained in how to look for and repair code smells in the system.  Through repairing these sections of smelly code (i.e. a refactoring) the design of the system emerges. For further information on TDD, I highly recommend the series “Is TDD Dead?”.  It discusses its pros and cons and when it is best used. Acceptance Test Driven Development (ATDD) Whereas TDD focuses on small unit tests that concentrate on a small piece of the system, Acceptance Tests focuses on the larger integrated environment.  Acceptance Tests usually correspond to user stories, which come directly from the customer. The unit tests focus on the inputs and outputs of smaller parts of the system, which are too low level to be of interest to the customer. ATDD generally uses the same tools as TDD.  However, ATDD uses fewer mocks and test doubles than TDD. ATDD often complements TDD; they aren’t competing methods.  A full test suite will usually consist of a large number of unit (created via TDD) tests and a smaller number of acceptance tests. Behaviour Driven Development (BDD) BDD is more about audience than workflow.  BDD pushes the testing realm out towards the client.  Developers, managers and the client all work together to define the tests. Typically different tooling is used for BDD than acceptance and unit testing.  This is done because the audience is not just developers.  Tools using the Gherkin family of languages allow for test scenarios to be described in an English format.  Other tools such as MSpec or FitNesse also strive for highly readable behaviour driven test suites. Because these tests are public facing (viewable by people outside the development team), the terminology usually changes.  You can’t get away with the same technobabble you can with unit tests written in a programming language that only developers understand.  For starters, they usually aren’t called tests.  Usually they’re called “examples”, “behaviours”, “scenarios”, or “specifications”. This may seem like a very subtle difference, but I’ve seen this small terminology change have a huge impact on the acceptance of the process.  Many people have a bias that testing is something that comes at the end of a project.  When you say we need to define the tests at the start of the project many people will immediately give that a lower priority on the project schedule.  But if you say we need to define the specification or behaviour of the system before we can start, you’ll get more cooperation.   Keep these test-first and test-after workflows in your tool belt.  With them you’ll be able to find new opportunities to apply them.

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• “It’s only test code…”

  - by Chris George

  “Let me hack this in, it’s only test code”, “Don’t worry about getting it reviewed, it’s only test code”, “It doesn’t have to be elegant or efficient, it’s only test code”… do these phrases sound familiar? Chances are if you’ve working with test automation, at one point or other you will have heard these phrases, you have probably even used them yourself! What is certain is that code written under this “it’s only test code” mantra will come back and bite you in the arse! I’ve recently encountered a case where a test was giving a false positive, therefore hiding a real product bug because that test code was very badly written. Firstly it was very difficult to understand what the test was actually trying to achieve let alone how it was doing it, and this complexity masked a simple logic error. These issues are real and they do happen. Let’s take a step back from this and look at what we are trying to do. We are writing test code that tests product code, and we do this to create a suite of tests that will help protect our software against regressions. This test code is making sure that the product behaves as it should by employing some sort of expected result verification. The simple cases of these are generally not a problem. However, automation allows us to explore more complex scenarios in many more permutations. As this complexity increases then so does the complexity of the test code. It is at this point that code which has not been architected properly will cause problems.   Keep your friends close… So, how do we make sure we are doing it right? The development teams I have worked on have always had Test Engineers working very closely with their Software Engineers. This is something that I have always tried to take full advantage of. They are coding experts! So run your ideas past them, ask for advice on how to structure your code, help you design your data structures. This may require a shift in your teams viewpoint, as contrary to this section title and folklore, Software Engineers are not actually the mortal enemy of Test Engineers. As time progresses, and test automation becomes more and more ingrained in what we do, the two roles are converging more than ever. Over the 16 years I have spent as a Test Engineer, I have seen the grey area between the two roles grow significantly larger. This serves to strengthen the relationship and common bond between the two roles which helps to make test code activities so much easier!   Pair for the win Possibly the best thing you could do to write good test code is to pair program on the task. This will serve a few purposes. you will get the benefit of the Software Engineers knowledge and experience the Software Engineer will gain knowledge on the testing process. Sharing the love is a wonderful thing! two pairs of eyes are always better than one… And so are two brains. Between the two of you, I will guarantee you will derive more useful test cases than if it was just one of you.   Code reviews Another policy which certainly pays dividends is the practice of code reviews. By having one of your peers review your code before you commit it serves two purposes. Firstly, it forces you to explain your code. Just the act of doing this will often pick up errors in your code. Secondly, it gets yet another pair of eyes on your code! I cannot stress enough how important code reviews are. The benefits they offer apply as much to product code as test code. In short, Software and Test Engineers should all be doing them! It can be extended even further by getting test code reviewed by a Software Engineer and a Test Engineer, and likewise product code. This serves to keep both functions in the loop with changes going on within your code base.   Learn from your devs I briefly touched on this earlier but I’d like to go into more detail here. Pairing with your Software Engineers when writing your test code is such an amazing opportunity to improve your coding skills. As I sit here writing this article waiting to be called into court for jury service, it reminds me that it takes a lot of patience to be a Test Engineer, almost as much as it takes to be a juror! However tempting it is to go rushing in and start writing your automated tests, resist that urge. Discuss what you want to achieve then talk through the approach you’re going to take. Then code it up together. I find it really enlightening to ask questions like ‘is there a better way to do this?’ Or ‘is this how you would code it?’ The latter question, especially, is where I learn the most. I’ve found that most Software Engineers will be reluctant to show you the ‘right way’ to code something when writing tests because they perceive the ‘right way’ to be too complicated for the Test Engineer (e.g. not mentioning LINQ and instead doing something verbose). So by asking how THEY would code it, it unleashes their true dev-ness and advanced code usually ensues! I would like to point out, however, that you don’t have to accept their method as the final answer. On numerous occasions I have opted for the more simple/verbose solution because I found the code written by the Software Engineer too advanced and therefore I would find it unreadable when I return to the code in a months’ time! Always keep the target audience in mind when writing clever code, and in my case that is mostly Test Engineers.  

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• VS2012 - How to manually convert .NET Class Library to a Portable Class Library

  - by Igor Milovanovic

  The portable libraries are the  response to the growing profile fragmentation in .NET frameworks. With help of portable libraries you can share code between different runtimes without dreadful #ifdef PLATFORM statements or even worse “Add as Link” source file sharing practices. If you have an existing .net class library which you would like to reference from a different runtime (e.g. you have a .NET Framework 4.5 library which you would like to reference from a Windows Store project), you can either create a new portable class library and move the classes there or edit the existing .csproj file and change the XML directly. The following example shows how to convert a .NET Framework 4.5 library to a Portable Class Library. First Unload the Project and change the following settings in the .csproj file: <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" /> to: <Import Project="$(MSBuildExtensionsPath32)\Microsoft\Portable \$(TargetFrameworkVersion)\Microsoft.Portable.CSharp.targets" /> and add the following keys to the first property group in order to get visual studio to show the framework picker dialog: <ProjectTypeGuids>{786C830F-07A1-408B-BD7F-6EE04809D6DB}; {FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>   After that you can select the frameworks in the Library Tab of the Portable Library:   As last step, delete any framework references from the library as you have them already referenced via the .NET Portable Subset.     [1] Cross-Platform Development with the .NET Framework - http://msdn.microsoft.com/en-us/library/gg597391.aspx [2] Framework Profiles in .NET: http://nitoprograms.blogspot.de/2012/05/framework-profiles-in-net.html

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• jQuery how to add class to a parent div which has a 3rd level child div with a specific class name.

  - by Vikram

  Hello friends I have an issue adding a special class to a couple of my divs. My layout is like this. <div class="container"> <div class="grid-6 push-3 equal" style="height: 999px;"> <div class="block"> <div id="mainbody"> <!-- Body content here --> </div> </div> </div> <div class="grid-2 equal" style="height: 999px;"> <div class="block"> <div id="sidebar-a"> <!-- Sidebar-a content here --> </div> </div> </div> <div class="grid-2 equal" style="height: 999px;"> <div class="block"> <div id="sidebar-b"> <!-- Sidebar-b content here --> </div> </div> </div> <div class="grid-2 equal" style="height: 999px;"> <div class="block"> <div id="sidebar-b"> <!-- Sidebar-c content here --> </div> </div> </div> </div> I want to add a different background color to each of my sidebars via CSS and when I code like: #mainbody { background : #fff; } #sidebar-a { background : #eee; } #sidebar-b { background : #ddd; } #sidebar-c { background : #ccc; } It is applying the background only to that specific class but that specific class is not of equal height. I actually need to apply to this <div class="grid-2 equal" style="height: 999px;"> div. Now the issue is that in this <div class="grid-6 push-3 equal" style="height: 999px;"> and class="grid-2 equal" style="height: 999px;"> the class names grid-6 and grid-2 are generated dynamically by my PHP of 960 Grid System and also the style="height: 999px; is generated by a jQuery script for Equal-Columns. What I want is to add a unique class name like this...... Look for a div with a class of .equal which has a child div with a class of .block and which further has a child div with an ID of sidebar-a. IF TRUE then add a class of .sidebar-a to the maindiv which has a class of .equal So that the result looks like this: <div class="grid-6 equal push-3 mainbody" style="height: 999px;"> <div class="grid-2 equal sidebar-a" style="height: 999px;"> <div class="grid-2 equal sidebar-b" style="height: 999px;"> <div class="grid-2 equal sidebar-c" style="height: 999px;"> Then I'll be able to style it like this: .mainbody { background : #fff; } .sidebar-a { background : #eee; } .sidebar-b { background : #ddd; } .sidebar-c { background : #ccc; } Hence I thought since I am anyway using jQuery in my Template, why not use it to deal with this issue. Please feel free to suggest a better way if you have something else in mind.

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• Why is an anonymous inner class containing nothing generated from this code?

  - by Andrew Westberg

  When run through javac on the cmd line Sun JVM 1.6.0_20, this code produces 6 .class files OuterClass.class OuterClass$1.class OuterClass$InnerClass.class OuterClass$InnerClass2.class OuterClass$InnerClass$InnerInnerClass.class OuterClass$PrivateInnerClass.class When run through JDT in eclipse, it produces only 5 classes. OuterClass.class OuterClass$1.class OuterClass$InnerClass.class OuterClass$InnerClass2.class OuterClass$InnerClass$InnerInnerClass.class OuterClass$PrivateInnerClass.class When decompiled, OuterClass$1.class contains nothing. Where is this extra class coming from and why is it created? package com.test; public class OuterClass { public class InnerClass { public class InnerInnerClass { } } public class InnerClass2 { } //this class should not exist in OuterClass after dummifying private class PrivateInnerClass { private String getString() { return "hello PrivateInnerClass"; } } public String getStringFromPrivateInner() { return new PrivateInnerClass().getString(); } }

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• Class Loading Deadlocks

  - by tomas.nilsson

  Mattis follows up on his previous post with one more expose on Class Loading Deadlocks As I wrote in a previous post, the class loading mechanism in Java is very powerful. There are many advanced techniques you can use, and when used wrongly you can get into all sorts of trouble. But one of the sneakiest deadlocks you can run into when it comes to class loading doesn't require any home made class loaders or anything. All you need is classes depending on each other, and some bad luck. First of all, here are some basic facts about class loading: 1) If a thread needs to use a class that is not yet loaded, it will try to load that class 2) If another thread is already loading the class, the first thread will wait for the other thread to finish the loading 3) During the loading of a class, one thing that happens is that the <clinit method of a class is being run 4) The <clinit method initializes all static fields, and runs any static blocks in the class. Take the following class for example: class Foo { static Bar bar = new Bar(); static { System.out.println("Loading Foo"); } } The first time a thread needs to use the Foo class, the class will be initialized. The <clinit method will run, creating a new Bar object and printing "Loading Foo" But what happens if the Bar object has never been used before either? Well, then we will need to load that class as well, calling the Bar <clinit method as we go. Can you start to see the potential problem here? A hint is in fact #2 above. What if another thread is currently loading class Bar? The thread loading class Foo will have to wait for that thread to finish loading. But what happens if the <clinit method of class Bar tries to initialize a Foo object? That thread will have to wait for the first thread, and there we have the deadlock. Thread one is waiting for thread two to initialize class Bar, thread two is waiting for thread one to initialize class Foo. All that is needed for a class loading deadlock is static cross dependencies between two classes (and a multi threaded environment): class Foo { static Bar b = new Bar(); } class Bar { static Foo f = new Foo(); } If two threads cause these classes to be loaded at exactly the same time, we will have a deadlock. So, how do you avoid this? Well, one way is of course to not have these circular (static) dependencies. On the other hand, it can be very hard to detect these, and sometimes your design may depend on it. What you can do in that case is to make sure that the classes are first loaded single threadedly, for example during an initialization phase of your application. The following program shows this kind of deadlock. To help bad luck on the way, I added a one second sleep in the static block of the classes to trigger the unlucky timing. Notice that if you uncomment the "//Foo f = new Foo();" line in the main method, the class will be loaded single threadedly, and the program will terminate as it should. public class ClassLoadingDeadlock { // Start two threads. The first will instansiate a Foo object, // the second one will instansiate a Bar object. public static void main(String[] arg) { // Uncomment next line to stop the deadlock // Foo f = new Foo(); new Thread(new FooUser()).start(); new Thread(new BarUser()).start(); } } class FooUser implements Runnable { public void run() { System.out.println("FooUser causing class Foo to be loaded"); Foo f = new Foo(); System.out.println("FooUser done"); } } class BarUser implements Runnable { public void run() { System.out.println("BarUser causing class Bar to be loaded"); Bar b = new Bar(); System.out.println("BarUser done"); } } class Foo { static { // We are deadlock prone even without this sleep... // The sleep just makes us more deterministic try { Thread.sleep(1000); } catch(InterruptedException e) {} } static Bar b = new Bar(); } class Bar { static { try { Thread.sleep(1000); } catch(InterruptedException e) {} } static Foo f = new Foo(); }

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• should I extend or create instance of the class

  - by meWantToLearn

  I have two classes Class A and Class B in Class A, i have three methods that perform the save, delete and select operation based upon the object I pass them. in Class B I perform the logic operations, such as modification to the property of the object before being passed to the methods of Class A, My problem is in Class B, should it extend Class A, and call the methods of class A , by parent::methodName or create instance of class A and then call Class A does not includes any property just methods. class A{ public function save($obj){ //code here } public function delete($obj){ //code here } public function select($obj){ //code here } } //Should I extend class A, and call the method by parent::methodName($obj) or create an instance of class A, call the method $instanceOfA-methodName($obj); class B extends A{ public function checkIfHasSaved($obj){ if($obj->saved == 'Yes'){ parent::save($obj); //**should I call the method like this** $instanceOFA = new A(); //**or create instance of class A and call without extending class A** instanceOFA->save($obj); } //other logic operations here } }

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• class __init__ (not instance __init__)

  - by wallacoloo

  Here's a very simple example of what I'm trying to get around: class Test(object): some_dict = {Test: True} The problem is that I cannot refer to Test while it's still being defined Normally, I'd just do this: class Test(object): def __init__(self): self.__class__.some_dict = {Test: True} But I never create an instance of this class. It's really just a container to hold a group of related functions and data (I have several of these classes, and I pass around references to them, so it is necessary for Test to be it's own class) So my question is, how could I refer to Test while it's being defined, or is there something similar to __init__ that get's called as soon as the class is defined? If possible, I want self.some_dict = {Test: True} to remain inside the class definition. This is the only way I know how to do this so far: class Test(object): @classmethod def class_init(cls): cls.some_dict = {Test: True} Test.class_init()

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• Changing multiple objects with a new class name using Jquery

  - by liquilife

  I'd like to click on a trigger and show a specific image. There are multiple triggers which would show a specific image related to it within a set. There are 4 sets The challenge for me is toggling the other images to hide only in this 'set' when one of these triggers are clicked, as there can only be one image showing at a time in each set. Here is the HTML I've put together thus far: <!-- Thumbnails which can be clicked on to toggle the larger preview image --> <div class="materials"> <a href="javascript:;" id="shirtgrey"><img src="/grey_shirt.png" height="122" width="122" /></a> <a href="javascript:;" id="shirtred"><img src="red_shirt.png" height="122" width="122" /></a> <a href="javascript:;" id="shirtblue"><img src="hblue_shirt.png" height="122" width="122" /></a> <a href="javascript:;" id="shirtgreen"><img src="green_shirt.png" height="122" width="122" /></a> </div> <div class="collars"> <a href="javascript:;" id="collargrey"><img src="grey_collar.png" height="122" width="122" /></a> <a href="javascript:;" id="collarred"><img src="red_collar.png" height="122" width="122" /></a> <a href="javascript:;" id="collarblue"><img src="blue_collar.png" height="122" width="122" /></a> <a href="javascript:;" id="collargreen"><img src="green_collar.png" height="122" width="122" /></a> </div> <div class="cuffs"> <a href="javascript:;" id="cuffgrey"><img src="grey_cuff.png" height="122" width="122" /></a> <a href="javascript:;" id="cuffred"><img src="red_cuff.png" height="122" width="122" /></a> <a href="javascript:;" id="cuffblue"><img src="blue_cuff.png" height="122" width="122" /></a> <a href="javascript:;" id="cuffgreen"><img src="/green_cuff.png" height="122" width="122" /></a> </div> <div class="pockets"> <a href="javascript:;" id="pocketgrey"><img src="grey_pocket.png" height="122" width="122" /></a> <a href="javascript:;" id="pocketred"><img src=".png" height="122" width="122" /></a> <a href="javascript:;" id="pocketblue"><img src="blue_pocket.png" height="122" width="122" /></a> <a href="javascript:;" id="pocketgreen"><img src="green_pocket.png" height="122" width="122" /></a> </div> <!-- The larger images where one from each set should be viewable at one time, triggered by the thumb clicked above --> <div class="selectionimg"> <div class="selectShirt"> <img src="grey_shirt.png" height="250" width="250" class="selectShirtGrey show" /> <img src="red_shirt.png" height="250" width="250" class="selectShirtRed hide" /> <img src="blue_shirt.png" height="250" width="250" class="selectShirtBlue hide" /> <img src="green_shirt.png" height="250" width="250" class="selectShirtGreen hide" /> </div> <div class="selectCollar"> <img src="grey_collar.png" height="250" width="250" class="selectCollarGrey show" /> <img src="red_collar.png" height="250" width="250" class="selectCollarRed hide" /> <img src="blue_collar.png" height="250" width="250" class="selectCollarBlue hide" /> <img src="green_collar.png" height="250" width="250" class="selectCollarGreen hide" /> </div> <div class="selectCuff"> <img src="grey_cuff.png" height="250" width="250" class="selectCuffGrey show" /> <img src="red_cuff.png" height="250" width="250" class="selectCuffRed hide" /> <img src="blue_cuff.png" height="250" width="250" class="selectCuffBlue hide" /> <img src="green_cuff.png" height="250" width="250" class="selectCuffGreen hide" /> </div> <div class="selectPocket"> <img src="grey_pocket.png" height="250" width="250" class="selectPocketGrey show" /> <img src="hred_pocket.png" height="250" width="250" class="selectPocketRed hide" /> <img src="blue_pocket.png" height="250" width="250" class="selectPocketBlue hide" /> <img src="green_pocket.png" height="250" width="250" class="selectPocketGreen hide" /> </div> </div> How can jQuery be used to change a class of an image to "show" and ensure that all other images in that same div are set to a class of "hide"? First time posting here. I'm very efficient with HTML and CSS and have a basic understanding of jQuery. I'm learning and this just seems a little bit beyond my abilities at the moment. I hope this all makes sense. Thanks for any help.

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• Getting an object from a 2d array inside of a class

  - by user36324

  I am have a class file that contains two classes, platform and platforms. platform holds the single platform information, and platforms has an 2d array of platforms. Im trying to render all of them in a for loop but it is not working. If you could kindly help me i would greatly appreciate. void Platforms::setUp() { for(int x = 0; x < tilesW; x++){ for(int y = 0; y < tilesH; y++){ Platform tempPlat(x,y,true,renderer,filename,tileSize/scaleW,tileSize/scaleH); platArray[x][y] = tempPlat; } } } void Platforms::show() { for(int x = 0; x < tilesW; x++){ for(int y = 0; y < tilesH; y++){ platArray[x][y].show(renderer,scaleW,scaleH); } } }

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• How can I load class's part using linq to sql without anonymous class or additional class?

  - by ais

  class Test { int Id{get;set;} string Name {get;set;} string Description {get;set;} } //1)ok context.Tests.Select(t => new {t.Id, t.Name}).ToList().Select(t => new Test{Id = t.Id, Name = t.Name}); //2)ok class TestPart{ int Id{get;set;} string Name {get;set;} } context.Tests.Select(t => new TestPart{Id = t.Id, Name = t.Name}).ToList().Select(t => new Test{Id = t.Id, Name = t.Name}); //3)error Explicit construction of entity type 'Test' in query is not allowed. context.Tests.Select(t => new Test{Id = t.Id, Name = t.Name}).ToList(); Is there any way to use third variant?

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• C# new class with only single property : derive from base or encapsulate into new ?

  - by Gobol

  I've tried to be descriptive :) It's rather programming-style problem than coding problem in itself. Let's suppose we have : A: public class MyDict { public Dictionary<int,string> dict; // do custom-serialization of "dict" public void SaveToFile(...); // customized deserialization of "dict" public void LoadFromFile(...); } B: public class MyDict : Dictionary<int,string> { } Which option would be better in the matter of programming style ? class B: is to be de/serialized externally. Main problem is : is it better to create new class (which would have only one property - like opt A:) or to create a new class derived - like opt B: ? I don't want any other data processing than adding/removing and de/serializing to stream. Thanks in advance!

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• Static class vs Singleton class in C# [closed]

  - by Floradu88

  Possible Duplicate: What is the difference between all-static-methods and applying a singleton pattern? I need to make a decision for a project I'm working of whether to use static or singleton. After reading an article like this I am inclined to use singleton. What is better to use static class or singleton? Edit 1 : Client Server Desktop Application. Please provide code oriented solutions.

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• polymorphism, inheritance in c# - base class calling overridden method?

  - by Andrew Johns

  This code doesn't work, but hopefully you'll get what I'm trying to achieve here. I've got a Money class, which I've taken from http://www.noticeablydifferent.com/CodeSamples/Money.aspx, and extended it a little to include currency conversion. The implementation for the actual conversion rate could be different in each project, so I decided to move the actual method for retrieving a conversion rate (GetCurrencyConversionRate) into a derived class, but the ConvertTo method contains code that would work for any implementation assuming the derived class has overriden GetCurrencyConversionRate so it made sense to me to keep it in the parent class? So what I'm trying to do is get an instance of SubMoney, and be able to call the .ConvertTo() method, which would in turn use the overriden GetCurrencyConversionRate, and return a new instance of SubMoney. The problem is, I'm not really understanding some concepts of polymorphism and inheritance yet, so not quite sure what I'm trying to do is even possible in the way I think it is, as what is currently happening is that I end up with an Exception where it has used the base GetCurrencyConversionRate method instead of the derived one. Something tells me I need to move the ConvertTo method down to the derived class, but this seems like I'll be duplicating code in multiple implementations, so surely there's a better way? public class Money { public CurrencyConversionRate { get { return GetCurrencyConversionRate(_regionInfo.ISOCurrencySymbol); } } public static decimal GetCurrencyConversionRate(string isoCurrencySymbol) { throw new Exception("Must override this method if you wish to use it."); } public Money ConvertTo(string cultureName) { // convert to base USD first by dividing current amount by it's exchange rate. Money someMoney = this; decimal conversionRate = this.CurrencyConversionRate; decimal convertedUSDAmount = Money.Divide(someMoney, conversionRate).Amount; // now convert to new currency CultureInfo cultureInfo = new CultureInfo(cultureName); RegionInfo regionInfo = new RegionInfo(cultureInfo.LCID); conversionRate = GetCurrencyConversionRate(regionInfo.ISOCurrencySymbol); decimal convertedAmount = convertedUSDAmount * conversionRate; Money convertedMoney = new Money(convertedAmount, cultureName); return convertedMoney; } } public class SubMoney { public SubMoney(decimal amount, string cultureName) : base(amount, cultureName) {} public static new decimal GetCurrencyConversionRate(string isoCurrencySymbol) { // This would get the conversion rate from some web or database source decimal result = new Decimal(2); return result; } }

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• jQuery only firing last class in multiple-class click

  - by user1134644

  I have a set of links like so: <a href="#internalLink1" class="classA">This has Class A</a> <a href="#internalLink2" class="classB">This has Class B</a> <a href="#internalLink3" class="classA classB">This has Class A and Class B</a> And here's the corresponding jQuery: $('.classA').click(function(){ // do class A stuff }); $('.classB').click(function(){ // do class B stuff }); Currently, when I click on the first link with Class A, it does the Class A stuff like it's supposed to. Similarly, when I click on the second link with Class B, it does the Class B stuff like it's supposed to. No worries there. My issue is, when I click on the third link with BOTH classes, it only fires the function for whichever class comes last (in this case, class B. If I put class A at the end instead, it performs class A's function). I want it to fire both. What am I doing wrong? Thanks in advance. EDIT: To those posting fiddles, nearly all of them work, so as many have said, it's most likely not my code, but the way it displays in my file. For a little more clarification, I was teaching myself some jQuery and decided to try making a (very) simple "Choose Your Own Adventure" type game. Here's a jsfiddle containing the opening of my bare-bones-please-don't-laugh game. Click on "Hide in the bushes", then "Examine the victim", then "Take any valuables and leave, he's dead already" <-- THIS is where the issue is. It's supposed to add 98 gold ("hawks") to your inventory, AND tell you that your alignment has shifted 1 point towards Chaotic. At the moment, it only does the chaotic alert, and no gold gets added to your inventory. The other option (refresh the fiddle to restart) that adds money to your inventory, but DOES NOT make you chaotic, works just fine (if you select "Search him for identification" instead of "take the money and run") Sorry this is so long!

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• Test Driven Development (TDD) in Visual Studio 2010- Microsoft Mondays

  - by Hosam Kamel

  November 14th , I will be presenting at Microsoft Mondays a session about Test Driven Development (TDD) in Visual Studio 2010 . Microsoft Mondays is program consisting of a series of Webcasts showcasing various Microsoft products and technologies. Each Monday we discuss a particular topic pertaining to development, infrastructure, Office tools, ERP, client/server operating systems etc. The webcast will be broadcast via Lync and can viewed from a web client. The idea behind the “Microsoft Mondays” program is to help you become more proficient in the products and technologies that you use and help you utilize their full potential.   Test Driven Development in Visual Studio 2010 Level – 300 (  Intermediate – Advanced ) Test Driven Development (TDD), also frequently referred to as Test Driven Design, is a development methodology where developers create software by first writing a unit test, then writing the actual system code to make the unit test pass.  The unit test can be viewed as a small specification around how the system should behave; writing it first helps the developer to focus on only writing enough code to make the test pass, thereby helping ensure a tight, lightweight system which is specifically focused meeting on the documented requirements. TDD follows a cadence of “Red, Green, Refactor.” Red refers to the visual display of a failing test – the test you write first will not pass because you have not yet written any code for it. Green refers to the step of writing just enough code in your system to make your unit test pass – your test runner’s UI will now show that test passing with a green icon. Refactor refers to the step of refactoring your code so it is tighter, cleaner, and more flexible. This cycle is repeated constantly throughout a TDD developer’s workday. Date:   November 14, 2011 Time:  10:00 a.m. – 11:00 a.m. (GMT+3)  http://www.eventbrite.com/event/2437620990/efbnen?ebtv=F   See you there! Hosam Kamel Originally posted at

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• Load and Web Performance Testing using Visual Studio Ultimate 2010-Part 2

  - by Tarun Arora

  Welcome back, in part 1 of Load and Web Performance Testing using Visual Studio 2010 I talked about why Performance Testing the application is important, the test tools available in Visual Studio Ultimate 2010 and various test rig topologies. In this blog post I’ll get into the details of web performance & load tests as well as why it’s important to follow a goal based pattern while performance testing your application. Tools => Options => Test Tools Have you visited the treasures of Visual Studio Menu bar tools => Options => Test Tools lately? The options to enable disable prompts on creating, editing, deleting or running manual/automated tests can be controller from here. The default test project language and default test types created on a new test project creation could be selected/unselected from here. Ever wondered how you can change the default limit of 25 test results, this can again be changed from here. If you record a lot of Web Tests and wish for the web test recorder to start with “that” URL populated, well this again can be specified from here. If you haven’t so far, I would urge you to spend 2 minutes in the test tools options.   Test Menu => Ready Steady Test Action! The Test tools are under the Test Menu in Visual Studio, apart from being able to create a new Test and Test List you can also load an existing vsmdi file. You can also manage your test controllers from here. A solution can have one or more test setting files, but there can only be one active test settings file at any time. Again, this selection can be done from here.  You can open the various test windows from under the windows option from the test menu. If you open the Test view window you will see that you have the option to group the tests by work items, project, test type, etc. You can set these properties by right clicking a test in the test list and choosing properties from the context menu.    So, what is a vsmdi file? vsmdi stands for Visual Studio Test Metadata File. Placed under the Solution Items this file keeps track of the list of unit tests in your solution. If you open the vsmdi file as an xml file you will see a series of Test Links nested with in the list Test List tags along with the Run Configuration tag. When in visual studio you run tests, the IDE looks at the vsmdi file to see what tests need to be run. You also have the option of using the vsmdi file in your team builds to specify which tests need to run as part of the build. Refer here for a walkthrough from a fellow blogger on how to use the vsmdi file in the team builds. Web Performance Test – The Truth! In Visual Studio 2010 “Web Tests” have been renamed to “Web Performance Tests”. Apart from renaming this test type there have been several improvements to this test type in visual studio 2010. I am very active on the MSDN Visual Studio And Load Testing forum and a frequent question from many users is “Do Web Tests support Pages that run JavaScript?” I will start with a little bit of background before answering this question. Web Performance Tests operate at the HTTP Layer, but why? To enable you to generate high loads with a relatively low amount of hardware, Web performance tests are driven at the protocol layer rather than instantiating a browser.The most common source of confusion is that users do not realize Web Performance Tests work at the HTTP layer. The tool adds to that misconception. After all, you record in IE, and when running a Web test you can select which browser to use, and then the result viewer shows the results in a browser window. So that means the tests run through the browser, right? NO! The Web test engine works at the HTTP layer, and does not instantiate a browser. What does that mean? In the diagram below, you can see there are no browsers running when the engine is sending and receiving requests. Does that mean I can’t test pages that use Java script? The best example for java script generating HTTP traffic is AJAX calls. The most common example of browser plugins are Silverlight or Flash. The Web test recorder will record HTTP traffic from AJAX calls and from most (but not all) browser plugins. This means you will still be able to web performance test pages that use java script or plugin and play back the results but the playback engine will not show the java script or plug in results in the ‘browser control’. If you want to test the page behaviour as a result of the java script or plug in consider using Coded UI Tests. This page looks like it failed, when in fact it succeeded! Looking closely at the response, and subsequent requests, it is clear the operation succeeded. As stated above, the reason why the browser control is pasting this message is because java script has been disabled in this control. So, to reiterate, the web performance test recorder: - Sends and receives data at the HTTP layer. - Does NOT run a browser. - Does NOT run java script. - Does NOT host ActiveX controls or plugins. There is a great series of blog posts from Ed Glas, i would highly recommend his blog to any one performing Load/Performance testing through Visual Studio. Demo – Web Performance Test [Demo] - Visual Studio Ultimate 2010: Test Settings and Configuration   [Demo]–Visual Studio Ultimate 2010: Web Performance Test   In this short video I try and answer the following questions, Why is performance Testing important? How does Visual Studio Help you performance Test your applications? How do i record a web performance test? How do make a web performance test data driven, transaction driven, loop driven, convert to code, add validations? Best practices for recording Web Performance Tests. I have a web performance test, what next? Creating the Web Performance Test was the first step towards load testing your application. Now that we have the base test we can test the page behaviour when N-users access the page. Have you ever had the head of business call you and mention that the marketing team has done a fantastic job and are expecting increased traffic on the web site, can the website survive the weekend with that additional load? This is the perfect opportunity to capacity test your application to see how your website holds up under various levels of load, you can work the results backwards to see how much hardware you may need to scale up your application to survive the weekend. Apart from that it is always a good idea to have some benchmarks around how the application performs under light loads for short duration, under heavy load for long duration and soak test the application run a constant load for a very week or two to record the effects of constant load for really long durations, this is a great way of identifying how your application handles the default IIS application pool reset which by default is configured to once every 25 hours. These bench marks will act as the perfect yard stick to measure performance gains when you start making improvements. BUT there are some best practices! => Goal Based Load Testing Approach Since the subject is vast and there are a lot of things to measure and analyse, … it is very easy to get distracted from the real goal!  You can optimize your application once you know where the pain points are. There is no point performing a load test of 5000 users if your intranet application will only have a 100 simultaneous users, it is important to keep focussed on the real goals of the project. So the idea is to have a user story around your load testing scenarios and test realistically. So it is recommended that you follow the below outline, It is an Iterative process, refine your objectives, identify the key scenarios, what is the expected workload, key metrics you want to report, record the web performance tests, simulate load and analyse results. Is your application already deployed in Production? This is great! You can analyse the IIS Logs to understand the user behaviour… But what are IIS LOGS? The IIS logs allow you to record events for each application and Web site on the Web server. You can create separate logs for each of your applications and Web sites. Logging information in IIS goes beyond the scope of the event logging or performance monitoring features provided by Windows. The IIS logs can include information, such as who has visited your site, what the visitor viewed, and when the information was last viewed. You can use the IIS logs to identify any attempts to gain unauthorized access to your Web server. How to configure IIS LOGS? For those Ninjas who already have IIS Logs configured (by the way its on by default) and need a way to analyse the IIS Logs, can use the Windows IIS Utility – Log Parser. Log Parser is a very powerful tool that provides a generic SQL-like language on top of many types of data like IIS Logs, Event Viewer entries, XML files, CSV files, File System and others; and it allows you to export the result of the queries to many output formats such as CSV, XML, SQL Server, Charts and others; and it works well with IIS 5, 6, 7 and 7.5. Frequently used Log Parser queries. Demo – Load Test [Demo]–Visual Studio Ultimate 2010: Load Testing   In this short video I try and answer the following questions, - Types of Performance Testing? - Perform Goal driven Load Testing, analyse Test Run Result and Generate a report? Recap A quick recap of what we have covered so far,     Thank you for taking the time out and reading this blog post, in part III of this blog series I’ll be getting into the details of Test Result Analysis, Test Result Drill through, Test Report Generation, Test Run Comparison, and the Asp.net Profiler. If you enjoyed the post, remember to subscribe to http://feeds.feedburner.com/TarunArora. Questions/Feedback/Suggestions, etc please leave a comment. See you on in Part III   Share this post : CodeProject

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