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• How to profile object creation in Java?

  - by gooli

  The system I work with is creating a whole lot of objects and garbage collecting them all the time which results in a very steeply jagged graph of heap consumption. I would like to know which objects are being generated to tune the code, but I can't figure out a way to dump the heap at the moment the garbage collection starts. When I tried to initiate dumpHeap via JConsole manually at random times, I always got results after GC finished its run, and didn't get any useful data. Any notes on how to track down excessive temporary object creation are welcome.

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• Unit Testing - Am I doing it right?

  - by baron

  Hi everyone, Basically I have been programing for a little while and after finishing my last project can fully understand how much easier it would have been if I'd have done TDD. I guess I'm still not doing it strictly as I am still writing code then writing a test for it, I don't quite get how the test becomes before the code if you don't know what structures and how your storing data etc... but anyway... Kind of hard to explain but basically lets say for example I have a Fruit objects with properties like id, color and cost. (All stored in textfile ignore completely any database logic etc) FruitID FruitName FruitColor FruitCost 1 Apple Red 1.2 2 Apple Green 1.4 3 Apple HalfHalf 1.5 This is all just for example. But lets say I have this is a collection of Fruit (it's a List<Fruit>) objects in this structure. And my logic will say to reorder the fruitids in the collection if a fruit is deleted (this is just how the solution needs to be). E.g. if 1 is deleted, object 2 takes fruit id 1, object 3 takes fruit id2. Now I want to test the code ive written which does the reordering, etc. How can I set this up to do the test? Here is where I've got so far. Basically I have fruitManager class with all the methods, like deletefruit, etc. It has the list usually but Ive changed hte method to test it so that it accepts a list, and the info on the fruit to delete, then returns the list. Unit-testing wise: Am I basically doing this the right way, or have I got the wrong idea? and then I test deleting different valued objects / datasets to ensure method is working properly. [Test] public void DeleteFruit() { var fruitList = CreateFruitList(); var fm = new FruitManager(); var resultList = fm.DeleteFruitTest("Apple", 2, fruitList); //Assert that fruitobject with x properties is not in list ? how } private static List<Fruit> CreateFruitList() { //Build test data var f01 = new Fruit {Name = "Apple",Id = 1, etc...}; var f02 = new Fruit {Name = "Apple",Id = 2, etc...}; var f03 = new Fruit {Name = "Apple",Id = 3, etc...}; var fruitList = new List<Fruit> {f01, f02, f03}; return fruitList; }

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• JButton and next/previous object of treemap

  - by supacat

  I have this problem: 1) There are objects placed in the TreeMap through the JTextField. (Phonebook-like program). 2)There are buttons that implement view of available records in TreeMap. When you click on these buttons next / previous available objects of TreeMap displaying in JTextField. (scroll through the available records). I tried this code, but I didn't work :/ btn[4].addActionListener(new ActionListener(){ Iterator iter = tree.keySet().iterator(); public void actionPerformed(ActionEvent e) { if (iter.hasNext()){ String str = iter.next().toString(); fldFio.setText(str); fldNumber.setText(tree.get(str)); } } });

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• Garbage Collection Java

  - by simion

  On the slides i am revising from it says the following; Live objects can be identified either by maintaining a count of the number of references to each object, or by tracing chains of references from the roots. Reference counting is expensive – it needs action every time a reference changes and it doesn’t spot cyclical structures, but it can reclaim space incrementally. Tracing involves identifying live objects only when you need to reclaim space – moving the cost from general access to the time at which the GC runs, typically only when you are out of memory. I understand the principles of why reference counting is expensive but do not understand what "doesn’t spot cyclical structures, but it can reclaim space incrementally." means. Could anyone help me out a little bit please? Thanks

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• Factorial function - design and test.

  - by lukas

  I'm trying to nail down some interview questions, so I stared with a simple one. Design the factorial function. This function is a leaf (no dependencies - easly testable), so I made it static inside the helper class. public static class MathHelper { public static int Factorial(int n) { Debug.Assert(n >= 0); if (n < 0) { throw new ArgumentException("n cannot be lower that 0"); } Debug.Assert(n <= 12); if (n > 12) { throw new OverflowException("Overflow occurs above 12 factorial"); } //by definition if (n == 0) { return 1; } int factorialOfN = 1; for (int i = 1; i <= n; ++i) { //checked //{ factorialOfN *= i; //} } return factorialOfN; } } Testing: [TestMethod] [ExpectedException(typeof(OverflowException))] public void Overflow() { int temp = FactorialHelper.MathHelper.Factorial(40); } [TestMethod] public void ZeroTest() { int factorialOfZero = FactorialHelper.MathHelper.Factorial(0); Assert.AreEqual(1, factorialOfZero); } [TestMethod] public void FactorialOf5() { int factOf5 = FactorialHelper.MathHelper.Factorial(5); Assert.AreEqual(120,factOf5); } [TestMethod] [ExpectedException(typeof(ArgumentException))] public void NegativeTest() { int factOfMinus5 = FactorialHelper.MathHelper.Factorial(-5); } I have a few questions: Is it correct? (I hope so ;) ) Does it throw right exceptions? Should I use checked context or this trick ( n 12 ) is ok? Is it better to use uint istead of checking for negative values? Future improving: Overload for long, decimal, BigInteger or maybe generic method? Thank you

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• Recognizing synchronization object hanging two 3rd party executables

  - by eran

  I'm using a 3rd party tool, which uses a 4th party plugin. Occasionally, the tool will hang when launched. Looking at the stack traces, I can see a few threads are waiting on WaitForSingleObject, and my bet is that they're blocking each other. Some of the threads start at the 3rt party tool, and some at the 4th party plugin. What I'd like to do is file the most detailed complaint to the 3rd party tool vendor, assuming it's its fault (I don't trust their local support to get those details themselves). For that, I'd like to: Find out what are the synchronization objects currently waited on Find out who has created those synchronization objects Tools currently at hand are VS2005, WinDbg and Process Explorer. OS is Window 7 64 bit. Any suggestions?

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• Xcode automatically converts the object to NSArray

  - by Farrukh Javeid

  I have been working on an app and during the development, I am facing a very strange problem. I have a NSMutableArray tempSortedArray, which is full of objects of Store types. All the objects are valid as I can see them in my GUI, the problem arises when I iterate through the array, at index 90, which can be generally anyone, the XCode converts the Store object to NSMutableArray object. Any idea, why this is happening. This is the code to check out what I am doing: NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"cashBack" ascending:NO]; NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor]; NSArray *sortedArray = [storesArray sortedArrayUsingDescriptors:sortDescriptors]; for (int i = 0; i < [tempSortedArray count]; i++) { Store *currentStore = [tempSortedArray objectAtIndex:i]; NSLog(@"store class: %@", [currentStore.class description]); if (currentStore.cashBackTypeString != (id)[NSNull null]) { //do whatever is required to do here }

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• Why are these lines being skipped? (java)

  - by David

  Here's the relevant bit of the source code: class Dice { String name ; int x ; int[] sum ; ... public Dice (String name) { this.name = name ; this.x = 0 ; this.sum = new int[7] ; } ... public static void main (String[] arg) { Dice a1 = new Dice ("a1") ; printValues (a1) ; } public static void printDice (Dice Dice) { System.out.println (Dice.name) ; System.out.println ("value: "+Dice.x) ; printValues (Dice) ; } public static void printValues (Dice Dice) { for (int i = 0; i<Dice.sum.length; i++) System.out.println ("#of "+i+"'s: "+Dice.sum[i]) ; } } Here is the output: #of 0's: 0 #of 1's: 0 #of 2's: 0 #of 3's: 0 #of 4's: 0 #of 5's: 0 #of 6's: 0 Why didn't these two lines execute inside printDice: System.out.println (Dice.name) ; System.out.println ("value: "+Dice.x) ; if they had then i would expect to see "a1" and "Value: 0" printed at the top of the rows of #of's

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• Nonstatic conversion functions; Casting different types, e.g. DirectX vector to OpenGL vector

  - by Markus

  I am currently working on a game "engine" that needs to move values between a 3D engine, a physics engine and a scripting language. Since I need to apply vectors from the physics engine to 3D objects very often and want to be able to control both the 3D, as well as the physics objects through the scripting system, I need a mechanism to convert a vector of one type (e.g. vector3d<float>) to a vector of the other type (e.g. btVector3). Unfortunately I can make no assumptions on how the classes/structs are laid out, so a simple reinterpret_cast probably won't do. So the question is: Is there some sort of 'static'/non-member casting method to achieve basically this: vector3d<float> operator vector3d<float>(btVector3 vector) { // convert and return } btVector3 operator btVector3(vector3d<float> vector) { // convert and return } Right now this won't compile since casting operators need to be member methods. (error C2801: 'operator foo' must be a non-static member)

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• Invoking code both before and after WebControl.Render method

  - by Dirk

  I have a set of custom ASP.NET server controls, most of which derive from CompositeControl. I want to implement a uniform look for "required" fields across all control types by wrapping each control in a specific piece of HTML/CSS markup. For example: <div class="requiredInputContainer"> ...custom control markup... </div> I'd love to abstract this behavior in such a way as to avoid having to do something ugly like this in every custom control, present and future: public class MyServerControl : TextBox, IRequirableField { public IRequirableField.IsRequired {get;set;} protected override void Render(HtmlTextWriter writer){ RequiredFieldHelper.RenderBeginTag(this, writer) //render custom control markup RequiredFieldHelper.RenderEndTag(this, writer) } } public static class RequiredFieldHelper{ public static void RenderBeginTag(IRequirableField field, HtmlTextWriter writer){ //check field.IsRequired, render based on its values } public static void RenderEndTag(IRequirableField field, HtmlTextWriter writer){ //check field.IsRequired , render based on its values } } If I was deriving all of my custom controls from the same base class, I could conceivably use Template Method to enforce the before/after behavior;but I have several base classes and I'd rather not end up with really a convoluted class hierarchy anyway. It feels like I should be able to design something more elegant (i.e. adheres to DRY and OCP) by leveraging the functional aspects of C#, but I'm drawing a blank.

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• C++ containers on classes, returning pointers

  - by otneil

  Hello, I'm having some trouble to find the best way to accomplish what I have in mind due to my inexperience. I have a class where I need to a vector of objects. So my first question will be: is there any problem having this: vector< AnyType container* and then on the constructor initialize it with new (and deleting it on the destructor)? Another question is: if this vector is going to store objects, shouldn't it be more like vector< AnyTipe* so they could be dynamically created? In that case how would I return an object from a method and how to avoid memory leaks (trying to use only STL)?

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• Writing secure java code with RMI

  - by jtnire

  Hi Everyone, This may seem like a very broad question, but any help is appreciated. I have a client/server solution written in java which uses the Cajo project (which uses RMI). I just want to try and make my solution as secure as possible, given the sensitive data that will be transferred between server and client. So far, my ideas are to make all my classes "final" as well as throw a "non-serializable" exception for all my classes in the server (except for the object bound in the RMI registry, and any objects that actually do need to be transferred of course). Can anyone think of any other ideas? I know that someone could write a malicious client - this isn't hard to do as you can find out the remote object's API using reflection. However is there anything I can do to protect a malicious client access classes/objects within the server that they are not supposed to access? Many Thanks

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• When is a try catch not a try catch?

  - by Dearmash

  I have a fun issue where during application shutdown, try / catch blocks are being seemingly ignored in the stack. I don't have a working test project (yet due to deadline, otherwise I'd totally try to repro this), but consider the following code snippet. public static string RunAndPossiblyThrow(int index, bool doThrow) { try { return Run(index); } catch(ApplicationException e) { if(doThrow) throw; } return ""; } public static string Run(int index) { if(_store.Contains(index)) return _store[index]; throw new ApplicationException("index not found"); } public static string RunAndIgnoreThrow(int index) { try { return Run(index); } catch(ApplicationException e) { } return ""; } During runtime this pattern works famously. We get legacy support for code that relies on exceptions for program control (bad) and we get to move forward and slowly remove exceptions used for program control. However, when shutting down our UI, we see an exception thrown from "Run" even though "doThrow" is false for ALL current uses of "RunAndPossiblyThrow". I've even gone so far as to verify this by modifying code to look like "RunAndIgnoreThrow" and I'll still get a crash post UI shutdown. Mr. Eric Lippert, I read your blog daily, I'd sure love to hear it's some known bug and I'm not going crazy. EDIT This is multi-threaded, and I've verified all objects are not modified while being accessed

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• Accommodating null values in a list?

  - by h259bws

  Hi, I'm new to Java and Groovy and am running into trouble with the following Groovy script. I created this whittled down version of a larger script to facilitate debugging. The script is iterating through a list trying to calc a running total of the values of all objects in the list. Some or all of these objects' values may be null. Script import org.apache.commons.lang.math.NumberUtils class Field { def name def value } def fields = [ new Field(name:'Annuities %', value:75), new Field(name:'Other %', value:null), ] //def totalFunding = fields.inject(0) {int total, Field myField - // total + NumberUtils.toInt(myField.value,0) as Integer def totalFunding = fields.inject(0) {int total, Field myField - total + myField?.value as Integer } It gets this error: Exception thrown: java.lang.NullPointerException java.lang.NullPointerException at Script3$_run_closure1.doCall(Script3:15) at Script3.run(Script3:14) What is the correct way to accomodate null values? Thanks, Betsy

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• FormStartPosition.CenterParent does not work

  - by kol

  In the following code, only the second method works for me (.NET 4.0). FormStartPosition.CenterParent does not center the child form over its parent. Why? Source: this SO question using System; using System.Drawing; using System.Windows.Forms; class Program { private static Form f1; public static void Main() { f1 = new Form() { Width = 640, Height = 480 }; f1.MouseClick += f1_MouseClick; Application.Run(f1); } static void f1_MouseClick(object sender, MouseEventArgs e) { Form f2 = new Form() { Width = 400, Height = 300 }; switch (e.Button) { case MouseButtons.Left: { // 1st method f2.StartPosition = FormStartPosition.CenterParent; break; } case MouseButtons.Right: { // 2nd method f2.StartPosition = FormStartPosition.Manual; f2.Location = new Point( f1.Location.X + (f1.Width - f2.Width) / 2, f1.Location.Y + (f1.Height - f2.Height) / 2 ); break; } } f2.Show(f1); } }

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• Pushing app to heroku error

  - by Ryan Max

  Hello, I am getting the following error when I try to push my app to heroku. I saw a similar thread on here, but the issues seemed related to OSX. I am running windows 7 $ git push heroku master Counting objects: 1652, done. Delta compression using up to 4 threads. fatal: object 91f5d3ee9e2edcd42e961ed2eb254d5181cbc734 inconsistent object lengt h (476 vs 8985) error: pack-objects died with strange error error: failed to push some refs to '[email protected]:floating-stone-94.git I'm not sure what this means. I can't find any consistent answers on the internet. I tried re-creating my ssh public key but still the same.

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• Direct flow depending on incoming dynamic type

  - by Improfane

  I have a listener class that accepts GUI change events in one method. The incoming event objects have a superclass of a type of GUI Event, the behaviour should depend on the dynamic type of the incoming variable. I wanted to do do lots of methods like: handleGUIEvent(EventChangedX event) handleGUIEvent(EventChangedY event) I am using a single event listener and receiving objects of various types but the behaviour should be different for each. What would you do? I do not want to use a switch statement as this would get unmaintainable.

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• Why is PLINQ slower than LINQ for this code?

  - by Rob Packwood

  First off, I am running this on a dual core 2.66Ghz processor machine. I am not sure if I have the .AsParallel() call in the correct spot. I tried it directly on the range variable too and that was still slower. I don't understand why... Here are my results: Process non-parallel 1000 took 146 milliseconds Process parallel 1000 took 156 milliseconds Process non-parallel 5000 took 5187 milliseconds Process parallel 5000 took 5300 milliseconds using System; using System.Collections.Generic; using System.Diagnostics; using System.Linq; namespace DemoConsoleApp { internal class Program { private static void Main() { ReportOnTimedProcess( () => GetIntegerCombinations(), "non-parallel 1000"); ReportOnTimedProcess( () => GetIntegerCombinations(runAsParallel: true), "parallel 1000"); ReportOnTimedProcess( () => GetIntegerCombinations(5000), "non-parallel 5000"); ReportOnTimedProcess( () => GetIntegerCombinations(5000, true), "parallel 5000"); Console.Read(); } private static List<Tuple<int, int>> GetIntegerCombinations( int iterationCount = 1000, bool runAsParallel = false) { IEnumerable<int> range = Enumerable.Range(1, iterationCount); IEnumerable<Tuple<int, int>> integerCombinations = from x in range from y in range select new Tuple<int, int>(x, y); return runAsParallel ? integerCombinations.AsParallel().ToList() : integerCombinations.ToList(); } private static void ReportOnTimedProcess( Action process, string processName) { var stopwatch = new Stopwatch(); stopwatch.Start(); process(); stopwatch.Stop(); Console.WriteLine("Process {0} took {1} milliseconds", processName, stopwatch.ElapsedMilliseconds); } } }

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• How to catch unintentional function interpositioning with GCC?

  - by SiegeX

  Reading through my book Expert C Programming, I came across the chapter on function interpositioning and how it can lead to some serious hard to find bugs if done unintentionally. The example given in the book is the following: my_source.c mktemp() { ... } main() { mktemp(); getwd(); } libc mktemp(){ ... } getwd(){ ...; mktemp(); ... } According to the book, what happens in main() is that mktemp() (a standard C library function) is interposed by the implementation in my_source.c. Although having main() call my implementation of mktemp() is intended behavior, having getwd() (another C library function) also call my implementation of mktemp() is not. Apparently, this example was a real life bug that existed in SunOS 4.0.3's version of lpr. The book goes on to explain the fix was to add the keyword static to the definition of mktemp() in my_source.c; although changing the name altogether should have fixed this problem as well. This chapter leaves me with some unresolved questions that I hope you guys could answer: Should our software group adopt the practice of putting the keyword static in front of all functions that we don't want to be exposed? Does GCC have a way to warn about function interposition? We certainly don't ever intend on this happening and I'd like to know about it if it does. Can interposition happen with functions introduced by static libraries? Thanks for the help.

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• What is a recommended Android utility class collection?

  - by Sebastian Roth

  I often find myself writing very similar code across projects. And more often than not, I copy stuff over from old projects. Things like: Create images with round corners read density into a static variable & re-use. 4 lines.. disable / hide multiple views / remote views at once. Example: } public static void disableViews(RemoteViews views, int... ids) { for (int id : ids) { views.setInt(id, SET_VISIBILITY, View.GONE); } } public static void showViews(RemoteViews views, int... ids) { for (int id : ids) { views.setInt(id, SET_VISIBILITY, View.VISIBLE); } } I'd love to package these kind of functions into 1 letter / 2 letter class names, i.e. V.showViews(RemoteViews views, int... ids) would be easy to write & remember I hope. I'm searching for Github recommendations, links and if nothing is found, I perhaps will start a small project on github to collect.

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• nhibernate sessionfactory instance more than once on web service

  - by Manuel

  Hello, i have a web service that use nhibernate. I have a singleton pattern on the repositorry library but on each call the service, it creates a new instance of the session factory wich is very expensive. What can i do? region Atributos /// <summary> /// Session /// </summary> private ISession miSession; /// <summary> /// Session Factory /// </summary> private ISessionFactory miSessionFactory; private Configuration miConfiguration = new Configuration(); private static readonly ILog log = LogManager.GetLogger(typeof(NHibernatePersistencia).Name); private static IRepositorio Repositorio; #endregion #region Constructor private NHibernatePersistencia() { //miConfiguration.Configure("hibernate.cfg.xml"); try { miConfiguration.Configure(); this.miSessionFactory = miConfiguration.BuildSessionFactory(); this.miSession = this.SessionFactory.OpenSession(); log.Debug("Se carga NHibernate"); } catch (Exception ex) { log.Error("No se pudo cargar Nhibernate " + ex.Message); throw ex; } } public static IRepositorio Instancia { get { if (Repositorio == null) { Repositorio = new NHibernatePersistencia(); } return Repositorio; } } #endregion #region Propiedades /// <summary> /// Sesion de NHibernate /// </summary> public ISession Session { get { return miSession.SessionFactory.GetCurrentSession(); } } /// <summary> /// Sesion de NHibernate /// </summary> public ISessionFactory SessionFactory { get { return this.miSessionFactory; } } #endregion In wich way can i create a single instance for all services?

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• Teacher confused about MVC?

  - by Gideon

  I have an assignment to create a game in java using MVC as a pattern. The thing is that stuff I read about MVC aren't really what the teacher is telling me. What I read is that the Model are the information objects, they are manipulated by the controllers. So in a game the controller mutates the placement of the objects and check if there is any collision etc. What my teacher told me is that I should put everything that is universal to the platform in the models and the controllers should only tell the model which input is given. That means the game loop will be in a model class, but also collision checks etc. So what I get from his story is that the View is the screen, the Controller is the unput handeler, and the Model is the rest. Can someone point me in the right direction?

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• How should flushing be handled in a doctrine EntityManager instance shared across different services in symfony2?

  - by Jbm

  I have defined several services in symfony 2 which persist changes to the database. These services have the doctrine instance as one of their dependencies: a.given.service: class: Acme\TestBundle\Service\AGivenService arguments: [@doctrine] If I have two different services and both of them persist objects through the EntityManager, which is obtained like this from the doctrine instance: $em = $doctrine->getEntityManager(); Would all services always share the same EntityManager? If so, how should I handle flushing if I wanted to handle all the changes in a single transaction? I have checked this: http://docs.doctrine-project.org/projects/doctrine-orm/en/2.0.x/reference/transactions-and-concurrency.html and it explains how to handle different transactions in a request, but I want to achieve the opposite, which is having different changes in different services handled as a single transaction. Is there a better approach to handle multiple changes in different services? For now my best bet is having a front-end service in charge of calling the other services and doing the flushing afterwards. Backend services would persist objects but would not do any flushing.

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• gwt - Using List<Serializable> in a RPC call?

  - by Garagos

  I have a RPC service with the following method: public List<Serializable> myMethod(TransactionCall call) {...} But I get a warning when this method is analyzed, and then the rpc call fails Analyzing 'my.project.package.myService' for serializable types Analyzing methods: public abstract java.util.List<java.io.Serializable> myMethod(my.project.package.TransactionCall call) Return type: java.util.List<java.io.Serializable> [...] java.io.Serializable Verifying instantiability (!) Checking all subtypes of Object wich qualify for serialization It seems I can't use Serializable for my List... I could use my own interface instead (something like AsyncDataInterface, wich implements the Serializable interface) but the fact is that my method will return a list custom objects AND basic objects (such as Strings, int....). So my questions are: Is it a standart behaviour? (I can't figure out why I can't use this interface in that case) Does anyone have a workaround for that kind of situation?

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• Run code before class instanciation in ActionScript 3

  - by soow.fr

  I need to run code in a class declaration before its instanciation. This would be especially useful to automatically register classes in a factory. See: // Main.as public class Main extends Sprite { public function Main() : void { var o : Object = Factory.make(42); } } // Factory.as public class Factory { private static var _factory : Array = new Array(); public static function registerClass(id : uint, c : Class) : void { _factory[id] = function () : Object { return new c(); }; } public static function make(id : uint) : Object { return _factory[id](); } } // Foo.as public class Foo { // Run this code before instanciating Foo! Factory.registerClass(42, Foo); } AFAIK, the JIT machine for the ActionScript language won't let me do that since no reference to Foo is made in the Main method. The Foo class being generated, I can't (and don't want to) register the classes in Main: I'd like to register all the exported classes in a specific package (or library). Ideally, this would be done through package introspection, which doesn't exist in ActionScript 3. Do you know any fix (or other solution) to my design issue?

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