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  • Java Concurrency in practice sample question

    - by andy boot
    I am reading "Java Concurrency in practice" and looking at the example code on page 51. According to the book this piece of code is at risk of of failure if it has not been published properly. Because I like to code examples and break them to prove how they work. I have tried to make it throw an AssertionError but have failed. (Leading me to my previous question) Can anyone post sample code so that an AssertionError is thrown? Rule: Do not modify the Holder class. public class Holder{ private int n; public Holder(int n){ this.n = n; } public void assertSanity(){ if (n != n) { throw new AssertionError("This statement is false"); } } } I have modified the class to make it more fragile but I still can not get an AssertionError thrown. class Holder2{ private int n; private int n2; public Holder2(int n) throws InterruptedException{ this.n = n; Thread.sleep(200); this.n2 = n; } public void assertSanity(){ if (n != n2) { throw new AssertionError("This statement is false"); } } } Is it possible to make either of the above classes throw an AssertionError? Or do we have to accept that they may occasionally do so and we can't write code to prove it?

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  • Java Concurrency in practice sample question

    - by andy boot
    I am reading "Java Concurrency in practice" and looking at the example code on page 51. This states that if a thread has references to a shared object then other threads may be able to access that object before the constructor has finished executing. I have tried to put this into practice and so I wrote this code thinking that if I ran it enough times a RuntimeException("World is f*cked") would occur. But it isn't doing. Is this a case of the Java spec not guaranting something but my particular implementation of java guaranteeing it for me? (java version: 1.5.0 on Ubuntu) Or have I misread something in the book? Code: (I expect an exception but it is never thrown) public class Threads { private Widgit w; public static void main(String[] s) throws Exception { while(true){ Threads t = new Threads(); t.runThreads(); } } private void runThreads() throws Exception{ new Checker().start(); w = new Widgit((int)(Math.random() * 100) + 1); } private class Checker extends Thread{ private static final int LOOP_TIMES = 1000; public void run() { int count = 0; for(int i = 0; i < LOOP_TIMES; i++){ try { w.checkMe(); count++; } catch(NullPointerException npe){ //ignore } } System.out.println("checked: "+count+" times out of "+LOOP_TIMES); } } private static class Widgit{ private int n; private int n2; Widgit(int n) throws InterruptedException{ this.n = n; Thread.sleep(2); this.n2 = n; } void checkMe(){ if (n != n2) { throw new RuntimeException("World is f*cked"); } } } }

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  • Concurrency problem with arrays (Java)

    - by Johannes
    For an algorithm I'm working on I tried to develop a blacklisting mechanism that can blacklist arrays in a specific way: If "1, 2, 3" is blacklisted "1, 2, 3, 4, 5" is also considered blacklisted. I'm quite happy with the solution I've come up with so far. But there seem to be some serious problems when I access a blacklist from multiple threads. The method "contains" (see code below) sometimes returns true, even if an array is not blacklisted. This problem does not occur if I only use one thread, so it most likely is a concurrency problem. I've tried adding some synchronization, but it didn't change anything. I also tried some slightly different implementations using java.util.concurrent classes. Any ideas on how to fix this? public class Blacklist { private static final int ARRAY_GROWTH = 10; private final Node root = new Node(); private static class Node{ private volatile Node[] childNodes = new Node[ARRAY_GROWTH]; private volatile boolean blacklisted = false; public void blacklist(){ this.blacklisted = true; this.childNodes = null; } } public void add(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return; else if(currentNode.childNodes.length <= edge) { currentNode.childNodes = Arrays.copyOf(currentNode.childNodes, edge + ARRAY_GROWTH); } if(currentNode.childNodes[edge] == null) { currentNode.childNodes[edge] = new Node(); } currentNode = currentNode.childNodes[edge]; } currentNode.blacklist(); } } public boolean contains(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return true; else if(currentNode.childNodes.length <= edge || currentNode.childNodes[edge] == null) return false; currentNode = currentNode.childNodes[edge]; } return currentNode.blacklisted; } } }

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  • Version Control for developers new to source control

    - by Daisetsu
    I've been writing code for a few years now and our backup strategy has been to zip the entire code directory up every few days and put it somewhere else on your hard drive, or occasionally upload it to some online file hosting service. Unfortunately the file hosting service got canceled without telling me and we lost years of backups. It's come down to the point where I finally have to learn to use version control. The only problems are My boss really doesn't like SVN, he tried it and it had a high learning curve (at least his client). We need a reliable place to host it (we can pay a reasonable amount). Can someone suggest what may be the best version control system and client for a newbie which won't be too annoying. Second what is a good remote version control service?

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  • Ajax Control Toolkit November 2011 Release

    - by Stephen Walther
    I’m happy to announce the November 2011 Release of the Ajax Control Toolkit. This release introduces a new Balloon Popup control and several enhancements to the existing Tabs control including support for on-demand loading of tab content, support for vertical tabs, and support for keyboard tab navigation. We also fixed the top-voted bugs associated with the Tabs control reported at CodePlex.com. You can download the new release by visiting the CodePlex website: http://AjaxControlToolkit.CodePlex.com Alternatively, the fast and easy way to get the latest release of the Ajax Control Toolkit is to use NuGet. Open your Library Package Manager console in Visual Studio 2010 and type: After you install the Ajax Control Toolkit through NuGet, please do a Rebuild of your project (the menu option Build, Rebuild). After you do a Rebuild, the ajaxToolkit prefix will appear in Intellisense: Using the Balloon Popup Control Why a new Balloon Popup control? The Balloon Popup control is the second most requested new feature for the Ajax Control Toolkit according to CodePlex votes: The Balloon Popup displays a message in a balloon when you shift focus to a control, click a control, or hover over a control. You can use the Balloon Popup, for example, to display instructions for TextBoxes which appear in a form: Here’s the code used to create the Balloon Popup: <ajaxToolkit:ToolkitScriptManager ID="tsm1" runat="server" /> <asp:TextBox ID="txtFirstName" Runat="server" /> <asp:Panel ID="pnlFirstNameHelp" runat="server"> Please enter your first name </asp:Panel> <ajaxToolkit:BalloonPopupExtender TargetControlID="txtFirstName" BalloonPopupControlID="pnlFirstNameHelp" BalloonSize="Small" UseShadow="true" runat="server" /> You also can use the Balloon Popup to explain hard to understand words in a text document: Here’s how you display the Balloon Popup when you hover over the link: The point of the conversation was <asp:HyperLink ID="lnkObfuscate" Text="obfuscated" CssClass="hardWord" runat="server" /> by his incessant coughing. <ajaxToolkit:ToolkitScriptManager ID="tsm1" runat="server" /> <asp:Panel id="pnlObfuscate" Runat="server"> To bewilder or render something obscure </asp:Panel> <ajaxToolkit:BalloonPopupExtender TargetControlID="lnkObfuscate" BalloonPopupControlID="pnlObfuscate" BalloonStyle="Cloud" UseShadow="true" DisplayOnMouseOver="true" Runat="server" />   There are four important properties which you need to know about when using the Balloon Popup control: BalloonSize – The three balloon sizes are Small, Medium, and Large. BalloonStyle -- The two built-in styles are Rectangle and Cloud. UseShadow – When true, a drop shadow appears behind the popup. Position – Can have the values Auto, BottomLeft, BottomRight, TopLeft, TopRight. When set to Auto, which is the default, the Balloon Popup will appear where it has the most screen real estate. The following screenshots illustrates how these settings affect the appearance of the Balloon Popup: Customizing the Balloon Popup You can customize the appearance of the Balloon Popup by creating your own Cascading Style Sheet and Sprite. The Ajax Control Toolkit sample site includes a sample of a custom Oval Balloon Popup style: This custom style was created by using a custom Cascading Style Sheet and image. You point the Balloon Popup at a custom Cascading Style Sheet and Cascading Style Sheet class by using the CustomCssUrl and CustomClassName properties like this: <asp:TextBox ID="txtCustom" autocomplete="off" runat="server" /> <br /> <asp:Panel ID="Panel3" runat="server"> This is a custom BalloonPopupExtender style created with a custom Cascading Style Sheet. </asp:Panel> <ajaxToolkit:BalloonPopupExtender ID="bpe1" TargetControlID="txtCustom" BalloonPopupControlID="Panel3" BalloonStyle="Custom" CustomCssUrl="CustomStyle/BalloonPopupOvalStyle.css" CustomClassName="oval" UseShadow="true" runat="server" />   Learn More about the Balloon Popup To learn more about the Balloon Popup control, visit the sample page for the Balloon Popup at the Ajax Control Toolkit sample site: http://www.asp.net/ajaxLibrary/AjaxControlToolkitSampleSite/BalloonPopup/BalloonPopupExtender.aspx Improvements to the Tabs Control In this release, we introduced several important new features for the existing Tabs control. We also fixed all of the top-voted bugs for the Tabs control. On-Demand Loading of Tab Content Here is the scenario. Imagine that you are using the Tabs control in a Web Forms page. The Tabs control displays two tabs: Customers and Products. When you click the Customers tab then you want to see a list of customers and when you click on the Products tab then you want to see a list of products. In this scenario, you don’t want the list of customers and products to be retrieved from the database when the page is initially opened. The user might never click on the Products tab and all of the work to load the list of products from the database would be wasted. In this scenario, you want the content of a tab panel to be loaded on demand. The products should only be loaded from the database and rendered to the browser when you click the Products tab and not before. The Tabs control in the November 2011 Release of the Ajax Control Toolkit includes a new property named OnDemand. When OnDemand is set to the value True, a tab panel won’t be loaded until you click its associated tab. Here is the code for the aspx page: <ajaxToolkit:ToolkitScriptManager ID="tsm1" runat="server" /> <ajaxToolkit:TabContainer ID="tabs" OnDemand="false" runat="server"> <ajaxToolkit:TabPanel HeaderText="Customers" runat="server"> <ContentTemplate> <h2>Customers</h2> <asp:GridView ID="grdCustomers" DataSourceID="srcCustomers" runat="server" /> <asp:SqlDataSource ID="srcCustomers" SelectCommand="SELECT * FROM Customers" ConnectionString="<%$ ConnectionStrings:StoreDB %>" runat="server" /> </ContentTemplate> </ajaxToolkit:TabPanel> <ajaxToolkit:TabPanel HeaderText="Products" runat="server"> <ContentTemplate> <h2>Products</h2> <asp:GridView ID="grdProducts" DataSourceID="srcProducts" runat="server" /> <asp:SqlDataSource ID="srcProducts" SelectCommand="SELECT * FROM Products" ConnectionString="<%$ ConnectionStrings:StoreDB %>" runat="server" /> </ContentTemplate> </ajaxToolkit:TabPanel> </ajaxToolkit:TabContainer> Notice that the TabContainer includes an OnDemand=”True” property. The Tabs control contains two Tab Panels. The first tab panel uses a DataGrid and SqlDataSource to display a list of customers and the second tab panel uses a DataGrid and SqlDataSource to display a list of products. And here is the code-behind for the page: using System; using System.Diagnostics; using System.Web.UI.WebControls; namespace ACTSamples { public partial class TabsOnDemand : System.Web.UI.Page { protected override void OnInit(EventArgs e) { srcProducts.Selecting += new SqlDataSourceSelectingEventHandler(srcProducts_Selecting); } void srcProducts_Selecting(object sender, SqlDataSourceSelectingEventArgs e) { Debugger.Break(); } } } The code-behind file includes an event handler for the Products SqlDataSource Selecting event. The handler breaks into the debugger by calling the Debugger.Break() method. That way, we can know when the Products SqlDataSource actually retrieves the list of products. When the OnDemand property has the value False then the Selecting event handler is called immediately when the page is first loaded. The contents of all of the tabs are loaded (and the contents of the unselected tabs are hidden) when the page is first loaded. When the OnDemand property has the value True then the Selecting event handler is not called when the page is first loaded. The event handler is not called until you click on the Products tab. If you never click on the Products tab then the list of products is never retrieved from the database. If you want even more control over when the contents of a tab panel gets loaded then you can use the TabPanel OnDemandMode property. This property accepts the following three values: None – Never load the contents of the tab panel again after the page is first loaded. Once – Wait until the tab is selected to load the contents of the tab panel Always – Load the contents of the tab panel each and every time you select the tab. There is a live demonstration of the OnDemandMode property here in the sample page for the Tabs control: http://www.asp.net/ajaxLibrary/AjaxControlToolkitSampleSite/Tabs/Tabs.aspx Displaying Vertical Tabs With the November 2011 Release, the Tabs control now supports vertical tabs. To create vertical tabs, just set the TabContainer UserVerticalStripPlacement property to the value True like this: <ajaxToolkit:TabContainer ID="tabs" OnDemand="false" UseVerticalStripPlacement="true" runat="server"> <ajaxToolkit:TabPanel ID="TabPanel1" HeaderText="First Tab" runat="server"> <ContentTemplate> <p> Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas porttitor congue massa. Fusce posuere, magna sed pulvinar ultricies, purus lectus malesuada libero, sit amet commodo magna eros quis urna. </p> </ContentTemplate> </ajaxToolkit:TabPanel> <ajaxToolkit:TabPanel ID="TabPanel2" HeaderText="Second Tab" runat="server"> <ContentTemplate> <p> Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas porttitor congue massa. Fusce posuere, magna sed pulvinar ultricies, purus lectus malesuada libero, sit amet commodo magna eros quis urna. </p> </ContentTemplate> </ajaxToolkit:TabPanel> </ajaxToolkit:TabContainer> In addition, you can use the TabStripPlacement property to control whether the tab strip appears at the left or right or top or bottom of the tab panels: Tab Keyboard Navigation Another highly requested feature for the Tabs control is support for keyboard navigation. The Tabs control now supports the arrow keys and the Home and End keys. In order for the arrow keys to work, you must first move focus to the tab control on the page by either clicking on a tab with your mouse or repeatedly hitting the Tab key. You can try out the new keyboard navigation support by trying any of the demos included in the Tabs sample page: http://www.asp.net/ajaxLibrary/AjaxControlToolkitSampleSite/Tabs/Tabs.aspx Summary I hope that you take advantage of the new Balloon Popup control and the new features which we introduced for the Tabs control. We added a lot of new features to the Tabs control in this release including support for on-demand tabs, support for vertical tabs, and support for tab keyboard navigation. I want to thank the developers on the Superexpert team for all of the hard work which they put into this release.

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  • What are the best resources for learning about concurrency and multi-threaded applications?

    - by Zepee
    I realised I have a massive knowledge gap when it comes to multi-threaded applications and concurrent programming. I've covered some basics in the past, but most of it seems to be gone from my mind, and it is definitely a field that I want, and need, to be more knowledgeable about. What are the best resources for learning about building concurrent applications? I'm a very practical oriented person, so if said book contains concrete examples the better, but I'm open to suggestions. I personally prefer to work in pseudocode or C++, and a slant toward game development would be best, but not required.

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  • Concurrency with listeners and upload: is this solution sound?

    - by cbrulak
    I'm working on an Android app. We have listeners for position data and camera capture which is timed on a background thread (not a service). The timer thread dictates when the image is captured and also when the data is cached in a local sqlite db. So, my question is how to properly store the location data as it comes in based on the listeners and pull that data so that the database can be updated as the camera capture is executed. I can't put the location data into the database as it arrives because it is processed more frequently than the camera images and the camera images are what dominates the architecture at the moment. (Location data is supplement). However I need the location data to get a rough location of the where the image is captured. My first thought was to have singleton store the location data. And have a semaphore on the getInstance method so if the database update is happening (after an image is captured) we don't have an error. The location data can wait for the database update or it can be lost for that particular event it doesn't really matter. What are you thoughts? Am I on the right track? (And is this the right sub-site or would this be better on stackoverflow?)

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  • Control convention for circular movement?

    - by Christian
    I'm currently doing a kind of training project in Unity (still a beginner). It's supposed to be somewhat like Breakout, but instead of just going left and right I want the paddle to circle around the center point. This is all fine and dandy, but the problem I have is: how do you control this with a keyboard or gamepad? For touch and mouse control I could work around the problem by letting the paddle follow the cursor/finger, but with the other control methods I'm a bit stumped. With a keyboard for example, I could either make it so that the Left arrow always moves the paddle clockwise (it starts at the bottom of the circle), or I could link it to the actual direction - meaning that if the paddle is at the bottom, it goes left and up along the circle or, if it's in the upper hemisphere, it moves left and down, both times toward the outer left point of the circle. Both feel kind of weird. With the first one, it can be counter intuitive to press Left to move the paddle right when it's in the upper area, while in the second method you'd need to constantly switch buttons to keep moving. So, long story short: is there any kind of existing standard, convention or accepted example for this type of movement and the corresponding controls? I didn't really know what to google for (control conventions for circular movement was one of the searches I tried, but it didn't give me much), and I also didn't really find anything about this on here. If there is a Question that I simply didn't see, please excuse the duplicate.

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  • Concurrency Utilities for Java EE 6: JSR 236 Rebooting

    - by arungupta
    JSR 166 added support for concurrency utilities in the Java platform. The JSR 236's, a.k.a Concurrency Utilities for Java EE, goal was to extend that support to the Java EE platform by adding asynchronous abilities to different application components. The EG was however stagnant since Dec 2003. Its coming back to life with the co-spec lead Anthony Lai's message to the JSR 236 EG (archived here). The JSR will be operating under JCP 2.8's transparency rules and can be tracked at concurrency-spec.java.net. All the mailing lists are archived here. The final release is expected in Q1 2013 and the APIs will live in the javax.enterprise.concurrent package. Please submit your nomination if you would like to join this EG.

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  • Self-updating collection concurrency issues

    - by DEHAAS
    I am trying to build a self-updating collection. Each item in the collection has a position (x,y). When the position is changed, an event is fired, and the collection will relocate the item. Internally the collection is using a “jagged dictionary”. The outer dictionary uses the x-coordinate a key, while the nested dictionary uses the y-coordinate a key. The nested dictionary then has a list of items as value. The collection also maintains a dictionary to store the items position as stored in the nested dictionaries – item to stored location lookup. I am having some trouble making the collection thread safe, which I really need. Source code for the collection: public class PositionCollection<TItem, TCoordinate> : ICollection<TItem> where TItem : IPositionable<TCoordinate> where TCoordinate : struct, IConvertible { private readonly object itemsLock = new object(); private readonly Dictionary<TCoordinate, Dictionary<TCoordinate, List<TItem>>> items; private readonly Dictionary<TItem, Vector<TCoordinate>> storedPositionLookup; public PositionCollection() { this.items = new Dictionary<TCoordinate, Dictionary<TCoordinate, List<TItem>>>(); this.storedPositionLookup = new Dictionary<TItem, Vector<TCoordinate>>(); } public void Add(TItem item) { if (item.Position == null) { throw new ArgumentException("Item must have a valid position."); } lock (this.itemsLock) { if (!this.items.ContainsKey(item.Position.X)) { this.items.Add(item.Position.X, new Dictionary<TCoordinate, List<TItem>>()); } Dictionary<TCoordinate, List<TItem>> xRow = this.items[item.Position.X]; if (!xRow.ContainsKey(item.Position.Y)) { xRow.Add(item.Position.Y, new List<TItem>()); } xRow[item.Position.Y].Add(item); if (this.storedPositionLookup.ContainsKey(item)) { this.storedPositionLookup[item] = new Vector<TCoordinate>(item.Position); } else { this.storedPositionLookup.Add(item, new Vector<TCoordinate>(item.Position)); // Store a copy of the original position } item.Position.PropertyChanged += (object sender, PropertyChangedEventArgs eventArgs) => this.UpdatePosition(item, eventArgs.PropertyName); } } private void UpdatePosition(TItem item, string propertyName) { lock (this.itemsLock) { Vector<TCoordinate> storedPosition = this.storedPositionLookup[item]; this.RemoveAt(storedPosition, item); this.storedPositionLookup.Remove(item); } } } I have written a simple unit test to check for concurrency issues: [TestMethod] public void TestThreadedPositionChange() { PositionCollection<Crate, int> collection = new PositionCollection<Crate, int>(); Crate crate = new Crate(new Vector<int>(5, 5)); collection.Add(crate); Parallel.For(0, 100, new Action<int>((i) => crate.Position.X += 1)); Crate same = collection[105, 5].First(); Assert.AreEqual(crate, same); } The actual stored position varies every time I run the test. I appreciate any feedback you may have.

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  • Techniques for modeling a dynamic dataflow with Java concurrency API

    - by Maian
    Is there an elegant way to model a dynamic dataflow in Java? By dataflow, I mean there are various types of tasks, and these tasks can be "connected" arbitrarily, such that when a task finishes, successor tasks are executed in parallel using the finished tasks output as input, or when multiple tasks finish, their output is aggregated in a successor task (see flow-based programming). By dynamic, I mean that the type and number of successors tasks when a task finishes depends on the output of that finished task, so for example, task A may spawn task B if it has a certain output, but may spawn task C if has a different output. Another way of putting it is that each task (or set of tasks) is responsible for determining what the next tasks are. Sample dataflow for rendering a webpage: I have as task types: file downloader, HTML/CSS renderer, HTML parser/DOM builder, image renderer, JavaScript parser, JavaScript interpreter. File downloader task for HTML file HTML parser/DOM builder task File downloader task for each embedded file/link If image, image renderer If external JavaScript, JavaScript parser JavaScript interpreter Otherwise, just store in some var/field in HTML parser task JavaScript parser for each embedded script JavaScript interpreter Wait for above tasks to finish, then HTML/CSS renderer (obviously not optimal or perfectly correct, but this is simple) I'm not saying the solution needs to be some comprehensive framework (in fact, the closer to the JDK API, the better), and I absolutely don't want something as heavyweight is say Spring Web Flow or some declarative markup or other DSL. To be more specific, I'm trying to think of a good way to model this in Java with Callables, Executors, ExecutorCompletionServices, and perhaps various synchronizer classes (like Semaphore or CountDownLatch). There are a couple use cases and requirements: Don't make any assumptions on what executor(s) the tasks will run on. In fact, to simplify, just assume there's only one executor. It can be a fixed thread pool executor, so a naive implementation can result in deadlocks (e.g. imagine a task that submits another task and then blocks until that subtask is finished, and now imagine several of these tasks using up all the threads). To simplify, assume that the data is not streamed between tasks (task output-succeeding task input) - the finishing task and succeeding task won't exist together, so the input data to the succeeding task will not be changed by the preceeding task (since it's already done). There are only a couple operations that the dataflow "engine" should be able to handle: A mechanism where a task can queue more tasks A mechanism whereby a successor task is not queued until all the required input tasks are finished A mechanism whereby the main thread (or other threads not managed by the executor) blocks until the flow is finished A mechanism whereby the main thread (or other threads not managed by the executor) blocks until certain tasks have finished Since the dataflow is dynamic (depends on input/state of the task), the activation of these mechanisms should occur within the task code, e.g. the code in a Callable is itself responsible for queueing more Callables. The dataflow "internals" should not be exposed to the tasks (Callables) themselves - only the operations listed above should be available to the task. Note that the type of the data is not necessarily the same for all tasks, e.g. a file download task may accept a File as input but will output a String. If a task throws an uncaught exception (indicating some fatal error requiring all dataflow processing to stop), it must propagate up to the thread that initiated the dataflow as quickly as possible and cancel all tasks (or something fancier like a fatal error handler). Tasks should be launched as soon as possible. This along with the previous requirement should preclude simple Future polling + Thread.sleep(). As a bonus, I would like to dataflow engine itself to perform some action (like logging) every time task is finished or when no has finished in X time since last task has finished. Something like: ExecutorCompletionService<T> ecs; while (hasTasks()) { Future<T> future = ecs.poll(1 minute); some_action_like_logging(); if (future != null) { future.get() ... } ... } Are there straightforward ways to do all this with Java concurrency API? Or if it's going to complex no matter what with what's available in the JDK, is there a lightweight library that satisfies the requirements? I already have a partial solution that fits my particular use case (it cheats in a way, since I'm using two executors, and just so you know, it's not related at all to the web browser example I gave above), but I'd like to see a more general purpose and elegant solution.

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  • Problems with Optimistic Concurrency through an ObjectDataSource and a GridView

    - by Bloodsplatter
    Hi I'm having a problem in an ASP .NET 2.0 Application. I have a GridView displaying data from an ObjectDataSource (connected to a BLL class which connects to a TabledAdapter (Typed Dataset using optimistic concurrency). The select (displaying the data) works just fine, however, when I update a row the GridView does pass the old values to the ObjectDataSource. <DataObjectMethod(DataObjectMethodType.Update, True)> _ Public Function UpdateOC(ByVal original_id As Integer, ByVal original_fotonummer As Integer, ByVal original_inhoud As String, ByVal original_postdatum As Date?, ByVal fotonummer As Integer, ByVal inhoud As String, ByVal postdatum As Date?) As Boolean Dim tweets As TwitpicOC.TweetsDataTable = adapterOC.GetTweetById(original_id) If tweets.Rows.Count = 0 Then Return False Dim row As TwitpicOC.TweetsRow = tweets(0) SmijtHetErIn(row, original_fotonummer, original_inhoud, original_postdatum) row.AcceptChanges() SmijtHetErIn(row, fotonummer, inhoud, postdatum) Return adapterOC.Update(row) = 1 End Function Public Sub SmijtHetErIn(ByVal row As TwitpicOC.TweetsRow, ByVal original_fotonummer As Integer, ByVal original_inhoud As String, ByVal original_postdatum As Date?) With row .fotonummer = original_fotonummer If String.IsNullOrEmpty(original_inhoud) Then .SetinhoudNull() Else .inhoud = original_inhoud If Not original_postdatum.HasValue Then .SetpostdatumNull() Else .postdatum = original_postdatum.Value End With End Sub And this is the part of the page: <div id='Overzicht' class='post'> <div class='title'> <h2> <a href='javascript:;'>Tweetsoverzicht</a></h2> <p> Overzicht</p> </div> <div class='entry'> <p> <asp:ObjectDataSource ID="odsGebruiker" runat="server" OldValuesParameterFormatString="" SelectMethod="GetAll" TypeName="TakeHomeWeb.BLL.GebruikersBLL"></asp:ObjectDataSource> <asp:ObjectDataSource ID="odsFoto" runat="server" SelectMethod="GetFotosByGebruiker" TypeName="TakeHomeWeb.BLL.FotosBLL"> <SelectParameters> <asp:ControlParameter ControlID="ddlGebruiker" DefaultValue="0" Name="userid" PropertyName="SelectedValue" Type="Int32" /> </SelectParameters> </asp:ObjectDataSource> <form id="form1" runat="server"> <asp:Label runat="server" AssociatedControlID="ddlGebruiker">Gebruiker:&nbsp;</asp:Label> <asp:DropDownList ID="ddlGebruiker" runat="server" AutoPostBack="True" DataSourceID="odsGebruiker" DataTextField="naam" DataValueField="userid" AppendDataBoundItems="True"> <asp:ListItem Text="Kies een gebruiker" Value="-1" /> </asp:DropDownList> <br /> <asp:Label runat="server" AssociatedControlID="ddlFoto">Foto:&nbsp;</asp:Label> <asp:DropDownList ID="ddlFoto" runat="server" AutoPostBack="True" DataSourceID="odsFoto" DataTextField="url" DataValueField="id" AppendDataBoundItems="True"> <asp:ListItem Value="-1">Kies een foto...</asp:ListItem> </asp:DropDownList> <br /> <div style="float: left"> <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="id" DataSourceID="odsTweets"> <Columns> <asp:CommandField ShowDeleteButton="True" ShowEditButton="True" /> <asp:BoundField DataField="id" HeaderText="id" InsertVisible="False" ReadOnly="True" SortExpression="id" /> <asp:BoundField DataField="fotonummer" HeaderText="fotonummer" SortExpression="fotonummer" /> <asp:BoundField DataField="inhoud" HeaderText="inhoud" SortExpression="inhoud" /> <asp:BoundField DataField="postdatum" HeaderText="postdatum" SortExpression="postdatum" /> </Columns> </asp:GridView> <asp:ObjectDataSource ID="odsTweets" runat="server" ConflictDetection="CompareAllValues" DeleteMethod="DeleteOC" OldValuesParameterFormatString="original_{0}" SelectMethod="GetTweetsByFotoId" TypeName="TakeHomeWeb.BLL.TweetsOCBLL" UpdateMethod="UpdateOC"> <DeleteParameters> <asp:Parameter Name="original_id" Type="Int32" /> <asp:Parameter Name="original_fotonummer" Type="Int32" /> <asp:Parameter Name="original_inhoud" Type="String" /> <asp:Parameter Name="original_postdatum" Type="DateTime" /> </DeleteParameters> <UpdateParameters> <asp:Parameter Name="original_id" Type="Int32" /> <asp:Parameter Name="original_fotonummer" Type="Int32" /> <asp:Parameter Name="original_inhoud" Type="String" /> <asp:Parameter Name="original_postdatum" Type="DateTime" /> <asp:Parameter Name="fotonummer" Type="Int32" /> <asp:Parameter Name="inhoud" Type="String" /> <asp:Parameter Name="postdatum" Type="DateTime" /> </UpdateParameters> <SelectParameters> <asp:ControlParameter ControlID="ddlFoto" Name="foto" PropertyName="SelectedValue" Type="Int32" /> </SelectParameters> </asp:ObjectDataSource> </div> </form> </p> </div> </div> I've got a feeling there's huge fail involved or something, but I've been staring at it for hours now and I just can't find it.

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  • A Custom Copy Control - Copies any ASP.NET control

    A custom control that targets any ASP.NET control and renders it...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • How can a gamepad control THE mouse?

    - by Boris
    There are many questions about this subject: Remapping both mouse and keyboard to a gamepad How do I configure a joystick or gamepad? How to control the mouse pointer via my keyboard? ... But the purpose of these questions/answers is to be able to use the gamepad for playing a game. I would a like a solution to use the gamepad to control THE mouse. To replace the mouse by the gamepad in all applications. That way I could control my computer in the living-room from my couch with a wireless gamepad.

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  • Which useful alternative control structures do you know?

    - by bigown
    Similar question was closed on SO. Sometimes when we're programming, we find that some particular control structure would be very useful to us, but is not directly available in our programming language. What alternative control structures do you think are a useful way of organizing computation? The goal here is to get new ways of thinking about structuring code, in order to improve chunking and reasoning. You can create a wishful syntax/semantic not available now or cite a less known control structure on an existent programming language. Answers should give ideas for a new programming language or enhancing an actual language. Think of this as brainstorming, so post something you think is a crazy idea but it can be viable in some scenario. It's about imperative programming.

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  • How to encourage version control adoption

    - by Man Wa kileleshwa
    I have recently started working in a team where there is no version control. Most of the team members are not used to any kind of version control. I've been using mercurial privately to track my work. I would like to encourage others to adopt it, and at the very least start to version their code as they develop changes. Can anyone give me advice on how I can encourage adoption of a distributed version control such as mercurial. Any advice on how to win people including managers to DVCS would be much appreciated.

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  • How to manage/control software versions?

    - by Zwie
    I'm facing a problem to create a version control outline for several already existing software parts for my company. Until now no one - expect for the developers - knows that there are different versions, which is the reason for the outline. In fact, I'm supposed to set up the future version control and communicate all this with our management... So, the question is how to create such a outline. Are there principles to follow to make software versioning easier or even a good program to map all versions and there compatibility? And are there generally good approaches to control software versions?

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  • XFCE4 Empty Volume Control Applet

    - by adamt
    I just wanted to ask, what could I mess up? My situation is this: In XFCE4.10 (!) on the panel0 I put the Indicator Applet. It always showed me the volume control and network icons. When I updated to 13.10 and after cleaned some stuff, removed some orphaned package, I noticed, the volume control applet is showing mute and if I clicked on it there is an empty drowdown menu like 10x5 px.. Now it became completely useless. So my question is WHAT should I reinstall or change to get the control work?.. :/ Thanks.

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  • September 2012 Release of the Ajax Control Toolkit

    - by Stephen.Walther
    I’m excited to announce the September 2012 release of the Ajax Control Toolkit! This is the first release of the Ajax Control Toolkit which supports the .NET 4.5 framework. We also continue to support ASP.NET 3.5 and ASP.NET 4.0. With this release, we’ve made several important bug fixes. The Superexpert team focused on fixing the highest voted issues associated with the CascadingDropDown control. I’ve created a list of these bug fixes later in this blog post. You can download the latest release of the Ajax Control Toolkit by visiting the following page at CodePlex: http://AjaxControlToolkit.CodePlex.com Alternatively, you can install the latest version of the Ajax Control Toolkit using NuGet by firing off the following command from the Package Manager Console: Install-Package AjaxControlToolkit Using the Ajax Control Toolkit with ASP.NET 4.5 Let me walk through the steps for using the Ajax Control Toolkit with ASP.NET 4.5. First, I’ll create a new ASP.NET 4.5 website with Visual Studio 2012. I’ll create the new website with the ASP.NET Web Forms Application template: When you create a new ASP.NET 4.5 site with the ASP.NET Web Forms Application template, you get a starter website. If you run the site, then you get a page with default content: Let me show you how you can add the Ajax Control Toolkit Calendar control to the homepage of this starter site. The first step is to use NuGet to install the Ajax Control Toolkit. Right-click the References folder in the Solution Explorer window and select the menu option Manage NuGet Packages. In the Manage NuGet Packages dialog, use the search box to search for the Ajax Control Toolkit (enter “AjaxControlToolkit”). After you find it, click the Install button to add the Ajax Control Toolkit to your project. That’s all you have to do to install the Ajax Control Toolkit! Now we are ready to start using the Ajax Control Toolkit controls. Open the default.aspx page so we can modify the contents of the page. Erase everything contained in the Content control with the ID of BodyContent. After erasing the content, declare the following two controls: <asp:TextBox ID="vacationDate" runat="server" /> <ajaxToolkit:CalendarExtender TargetControlID="vacationDate" runat="server" /> The first control is a standard ASP.NET TextBox control and the second control is an Ajax Control Toolkit Calendar control. You should get intellisense as you type out the Ajax Control Toolkit Calendar control. If you don’t, then close and re-open the Default.aspx page. Now, let’s run our app. Hit the F5 button or select Debug, Start Debugging from the Visual Studio menu. You will get the error message “MsAjaxBundle is not a valid script name”. Don’t despair! We need to update the Master Page so it uses the ToolkitScriptManager instead of the default ScriptManager. Open the Site.Master file and find where the ScriptManager is declared. The ScriptManager should look like this: <asp:ScriptManager runat="server"> <Scripts> <%--Framework Scripts--%> <asp:ScriptReference Name="MsAjaxBundle" /> <asp:ScriptReference Name="jquery" /> <asp:ScriptReference Name="jquery.ui.combined" /> <asp:ScriptReference Name="WebForms.js" Assembly="System.Web" Path="~/Scripts/WebForms/WebForms.js" /> <asp:ScriptReference Name="WebUIValidation.js" Assembly="System.Web" Path="~/Scripts/WebForms/WebUIValidation.js" /> <asp:ScriptReference Name="MenuStandards.js" Assembly="System.Web" Path="~/Scripts/WebForms/MenuStandards.js" /> <asp:ScriptReference Name="GridView.js" Assembly="System.Web" Path="~/Scripts/WebForms/GridView.js" /> <asp:ScriptReference Name="DetailsView.js" Assembly="System.Web" Path="~/Scripts/WebForms/DetailsView.js" /> <asp:ScriptReference Name="TreeView.js" Assembly="System.Web" Path="~/Scripts/WebForms/TreeView.js" /> <asp:ScriptReference Name="WebParts.js" Assembly="System.Web" Path="~/Scripts/WebForms/WebParts.js" /> <asp:ScriptReference Name="Focus.js" Assembly="System.Web" Path="~/Scripts/WebForms/Focus.js" /> <asp:ScriptReference Name="WebFormsBundle" /> <%--Site Scripts--%> </Scripts> </asp:ScriptManager> We need to make three changes to the ScriptManager: 1) We need to replace the asp:ScriptManager with the ajaxToolkit:ToolkitScriptManager 2) We need to remove the MsAjaxBundle bundle from the ScriptReferences 3) We need to remove the Assembly=”System.Web” attributes from the ScriptReferences After you make these three changes, the ToolkitScriptManager should looks like this: <ajaxToolkit:ToolkitScriptManager runat="server"> <Scripts> <%--Framework Scripts--%> <asp:ScriptReference Name="jquery" /> <asp:ScriptReference Name="jquery.ui.combined" /> <asp:ScriptReference Name="WebForms.js" Path="~/Scripts/WebForms/WebForms.js" /> <asp:ScriptReference Name="WebUIValidation.js" Path="~/Scripts/WebForms/WebUIValidation.js" /> <asp:ScriptReference Name="MenuStandards.js" Path="~/Scripts/WebForms/MenuStandards.js" /> <asp:ScriptReference Name="GridView.js" Path="~/Scripts/WebForms/GridView.js" /> <asp:ScriptReference Name="DetailsView.js" Path="~/Scripts/WebForms/DetailsView.js" /> <asp:ScriptReference Name="TreeView.js" Path="~/Scripts/WebForms/TreeView.js" /> <asp:ScriptReference Name="WebParts.js" Path="~/Scripts/WebForms/WebParts.js" /> <asp:ScriptReference Name="Focus.js" Path="~/Scripts/WebForms/Focus.js" /> <asp:ScriptReference Name="WebFormsBundle" /> <%--Site Scripts--%> </Scripts> </ajaxToolkit:ToolkitScriptManager> After we make these changes, the app should run successfully. You’ll get a page which contains a text field. When you click inside the text field, a popup calendar is displayed. Ajax Control Toolkit and jQuery You might have noticed that the ScriptManager includes a reference to jQuery by default. We did not remove that reference when we converted the ScriptManager to a ToolkitScriptManager. You can use the Ajax Control Toolkit and jQuery side-by-side. Here’s how you can modify the Default.aspx page so that it contains two popup calendars. The first popup calendar is created with the Ajax Control Toolkit and the second popup calendar is created with jQuery: <asp:TextBox ID="vacationDate" runat="server" /> <ajaxToolkit:CalendarExtender TargetControlID="vacationDate" runat="server" /> <input id="birthDate" /> <script> $("#birthDate").datepicker(); </script> Before you can start using jQuery UI plugins, you need to complete one more step. You need to add the jQuery UI themes bundle to the HEAD of the Site.Master page like this: <head runat="server"> <meta charset="utf-8" /> <title><%: Page.Title %> - My ASP.NET Application</title> <asp:PlaceHolder runat="server"> <%: Scripts.Render("~/bundles/modernizr") %> </asp:PlaceHolder> <webopt:BundleReference runat="server" Path="~/Content/css" /> <webopt:BundleReference runat="server" Path="~/Content/themes/base/css" /> <link href="~/favicon.ico" rel="shortcut icon" type="image/x-icon" /> <meta name="viewport" content="width=device-width" /> <asp:ContentPlaceHolder runat="server" ID="HeadContent" /> </head> The markup above includes a reference to the jQuery UI themes bundle: <webopt:BundleReference runat="server" Path="~/Content/themes/base/css" /> Now that we have made these changes, we can use the Ajax Control Toolkit and jQuery at the same time. When you run your app, you get two popup calendars. When you click in the first text field, the Ajax Control Toolkit calendar appears. When you click in the second text field, the jQuery UI popup calendar appears: Bug Fixes in this Release We made several important bug fixes with this release of the Ajax Control Toolkit and integrated several Pull Requests contributed by the community. Our primary focus during this sprint was fixing issues with the CascadingDropDown control. We fixed the following issues associated with the CascadingDropDown: · 9490 – Don’t disable dropdowns in CascadingDropDown · 14223 – CascadingDropDown Reset or Setting SelectedValue from WebMethod · 12189 – CascadingDropDown not obeying disabled state of DropDownList · 22942 – CascadingDropDown infinite loop (with solution) · 8671 – CascadingDropdown options is null or undefined · 14407 – CascadingDropDown: populated client event happens too often · 17148 – CascadingDropDown – Add “UseHttpGet” property · 10221 – No NotNull check in CascadingDropDown · 12228 – Provide property for case-insensitive DefaultValue lookup in CascadingDropdown We also fixed the following two issues which are not directly related to the CascadingDropDown control: · 27108 – CalendarExtender: Bug when selecting December shifts to January. · 27041 – Input controls with HTML5 types do not post back in Firefox, Chrome, Safari Finally, we integrated several Pull Requests submitted by the community (Thank you community!): · Added French localized resources for the AjaxFileUpload · Resolved an issue which prevented the AjaxFileUpload control from working with pages that require query string variables. · Extended the AjaxFileUploadEventArgs class to include the current file index in the queue and the total number of files in the queue. · Fixed an issue with TabContainer and TabPanel which caused the OnActiveTabChanged event to fire too often. Summary I’m happy to see the Ajax Control Toolkit move forward into the brave new world of ASP.NET 4.5! In this latest release, we focused on ensuring that the Ajax Control Toolkit works smoothly with ASP.NET 4.5 applications. We also fixed the highest voted bugs associated with the CascadingDropDown control and integrated several Pull Request submitted by the community. Once again, I want to thank the Superexpert team for their hard work on this release!

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  • Installing Ajax Control Toolkit in Visual Studio 2010

    - by nannette
    I needed to install the Ajax Control Toolkit for Visual Studio 2010 4.0 Framework, so I googled "install ajax control toolkit visual studio 2010" and found this step by step guide: http://www.asp.net/ajaxlibrary/act.ashx It installed perfectly for me the first time, so I'd recommend following the above link. There were just a few steps and voila! I'm including this link here, because a in February 2008, I posted a blog for installing the toolkit in Visual Web Developer. http://weblogs.asp.net/nannettethacker...(read more)

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  • Version control and data provenance in charts, slides, and marketing materials that derive from code ouput

    - by EMS
    I develop as part of a small team that mostly does research and statistics stuff. But from the output of our code, other teams often create promotional materials, slides, presentations, etc. We run into a big problem because the marketing team (non-programmers) tend to use Excel, Adobe products, or other tools to carry out their work, and just want easy-to-use data formats from us. This leads to data provenance problems. We see email chains with attachments from 6 months ago and someone is saying "Hey, who generated this data. Can you generate more of it with the recent 6 months of results added in?" I want to help the other teams effectively use version control (my team uses it reasonably well for the code, but every other team classically comes up with many excuses to avoid it). For version controlling a software project where the participants are coders, I have some reasonable understanding of best practices and what to do. But for getting a team of marketing professionals to version control marketing materials and associate metadata about the software used to generate the data for the charts, I'm a bit at a loss. Some of the goals I'd like to achieve: Data that supported a material should never be associated with a person. As in, it should never be the case that someone says "Hey Person XYZ, I see you sent me this data as an attachment 6 months ago, can you update it for me?" Rather, data should be associated with the code and code-version of any code that was used to get it, and perhaps a team of many people who may maintain that code. Then references for data updates are about executing a specific piece of code, with a known version number. I'd like this to be a process that works easily with the tech that the marketing team already uses (e.g. Excel files, Adobe file, whatever). I don't want to burden them with needing to learn a bunch of new stuff just to use version control. They are capable folks, so learning something is fine. Ideally they could use our existing version control framework, but there are some issues around that. I think knowing some general best practices will be enough though, and I can handle patching that into the way our stuff works now. Are there any goals I am failing to think about? What are the time-tested ways to do something like this?

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  • Should generated documentation go in version control history?

    - by dukeofgaming
    I'm against compiled stuff going into version control, specially when it comes to compiled binaries, however, my principles are now in question after adding doxygen support for a project. Should the hundreds of files generated by doxygen go into version control?, what is the recommended practice here?, I think the ideal would be automating the process in a server that publishes that documentation at the same time, however, there is no such server now nor there will be for some time.

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  • The QueryExtender web server control

    - by nikolaosk
    In this post I am going to present a hands on example on how to use the QueryExtender web server control. It is built into ASP.Net 4.0 and it is available from the Toolbox in VS 2010.Before we move on with our example let me explain what this control does and why we need it. Its goal is to extend the functionality of the LINQ to Entities and LINQ to SQL datasources.Most of the times when we have data coming out from a datasource we want some sort of filtering. We do achieve that by using a Where...(read more)

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  • ubuntu lite volume control

    - by idio
    i've recently gave up on the main ubuntu, especially since new updates ruined Quantal and Raring is just a mess and went on to install a more friendly version: Ubuntu Lite. while i am quite happy with most functionalities of this lite version of 12.04, one of the modifications volume control is totally ridiculos, there is an applet that is completely counter-intutitive. So my question is: is there a way to install back the ubuntu classic volume control so i can let go of this applet alltogether? thanx

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