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• android use local service to refresh map UI

  - by urobo

  I don't need a strict code related answer I just need somebody to tell me what I am missing. My application has to retrieve from a web service (xmlrpc) the positions of some users I know and update their position on a MapView. So I decided to use a Service and an Activity extending MapActivity to show results. I thought about two solutions: I ) start the service and make it ask every minute for these positions and send them to the activity as a bundle via intent. (This didn't work out well, since once shown I couldn't find a method to let the activity continue refresh itself until she stop receiving intents+data from the service) II ) Incorporate a thread within the activity which starts the service via context.startService(...) every minute. And the MapUI refresh itself once the service send back an intent and stop itself. (Maybe I will fall in the same problem category as before I haven't tryied yet). I am also giving directions (via maps.google ws) in this way I'd like to refresh only users positions on the map and save the route. What Am I missing do you have any suggestions? related to activities/services internal mechanics, don't know launch modes, use broadcast receivers or intent filters? Thanks in advance

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• Java: Using GSon incorrectly? (null pointer exception)

  - by Rosarch

  I'm trying to get the hits of a google search from a string of the query. public class Utils { public static int googleHits(String query) throws IOException { String googleAjax = "http://ajax.googleapis.com/ajax/services/search/web?v=1.0&q="; String json = stringOfUrl(googleAjax + query); JsonObject hits = new Gson().fromJson(json, JsonObject.class); return hits.get("estimatedResultCount").getAsInt(); } public static String stringOfUrl(String addr) throws IOException { ByteArrayOutputStream output = new ByteArrayOutputStream(); URL url = new URL(addr); IOUtils.copy(url.openStream(), output); return output.toString(); } public static void main(String[] args) throws URISyntaxException, IOException { System.out.println(googleHits("odp")); } } The following exception is thrown: Exception in thread "main" java.lang.NullPointerException at odp.compling.Utils.googleHits(Utils.java:48) at odp.compling.Utils.main(Utils.java:59) What am I doing incorrectly? Should I be defining an entire object for the Json return? That seems excessive, given that all I want to do is get one value. For reference: the returned JSON structure.

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• Getting hover text with selenium in java

  - by BinaryEmpire

  I am trying to figure out how to get the product availability text from a page like http://www.walmart.com/browse/TV-Video/TVs/_/N-96v3? (once a store has been selected) I selected 76574 as my zipcode and went to the "In My Store" tab The code I have now is WebElement hoverElement = driver.findElement(By.xpath(".//*[@id='Body_15992428']/span")); WebElement hidden = driver.findElement(By.xpath(".//*[@id='slapInfo_NoVariant_15992428']/div")); Actions builder = new Actions(driver); builder.clickAndHold(hoverElement).build().perform(); System.out.println(hidden.getText()); **Edit: I tried profile.setEnableNativeEvents(false); and the text is now displayed in the automated browser window. I still cannot get to the text I want though. It does not throw an exception, only displays nothing because the driver thinks its still hidden. Any one know how to fix this? I keep getting Exception in thread "main" org.openqa.selenium.InvalidElementStateException: Cannot perform native interaction: Could not load native events component. Even after I do profile.setEnableNativeEvents(true); Are there any other ways I can get the hidden text, or what am I doing wrong here? Additionally while I was inspecting the code with firebug, I saw that there is this code <script type="text/javascript"> WALMART.$(document).ready(function(){ WALMART.$('#Body_15992428').hover(function(){ WALMART.$('#SeeStoreAvailBubble').wmBubble('update',WALMART.$('#bubbleMsgUpdate_15992428').html()); }); }); </script> I dont really know how to do things directly with javascript but is there is any way of getting the message text directly from that with a javascript executor?

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• loop is cut one element of the array

  - by Walaa

  The problem is : Write a program that reads a number n and then declares an array of n elements. The program then fills the array with the first n numbers, where each number is two to the power of the previous. Finally, display array’s contents. My code : import java.util.*; public class Q1 { static Scanner scan = new Scanner (System.in); public static void main(String args [] ) { int num; int i = 0; System.out.println("Enter a number :"); num = scan.nextInt(); double [] a=new double[num]; a[0]= num ; for ( ;i<=a.length-1 ; i++) { a[i+1] = Math.pow(2,a[i]); System.out.println((int)(a[i]) ); } } } The error is : ----jGRASP exec: java Q1 Enter a number : 4 4 16 65536 Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4 at Q1.main(Q1.java:16) ----jGRASP wedge2: exit code for process is 1. why it says that? And the number by user printed twice!

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• Efficient way to remove empty lists from lists without evaluating held expressions?

  - by Alexey Popkov

  In previous thread an efficient way to remove empty lists ({}) from lists was suggested: Replace[expr, x_List :> DeleteCases[x, {}], {0, Infinity}] Using the Trott-Strzebonski in-place evaluation technique this method can be generalized for working also with held expressions: f1[expr_] := Replace[expr, x_List :> With[{eval = DeleteCases[x, {}]}, eval /; True], {0, Infinity}] This solution is more efficient than the one based on ReplaceRepeated: f2[expr_] := expr //. {left___, {}, right___} :> {left, right} But it has one disadvantage: it evaluates held expressions if they are wrapped by List: In[20]:= f1[Hold[{{}, 1 + 1}]] Out[20]= Hold[{2}] So my question is: what is the most efficient way to remove all empty lists ({}) from lists without evaluating held expressions? The empty List[] object should be removed only if it is an element of another List itself. Here are some timings: In[76]:= expr = Tuples[Tuples[{{}, {}}, 3], 4]; First@Timing[#[expr]] & /@ {f1, f2, f3} pl = Plot3D[Sin[x y], {x, 0, Pi}, {y, 0, Pi}]; First@Timing[#[pl]] & /@ {f1, f2, f3} Out[77]= {0.581, 0.901, 5.027} Out[78]= {0.12, 0.21, 0.18} Definitions: Clear[f1, f2, f3]; f3[expr_] := FixedPoint[ Function[e, Replace[e, {a___, {}, b___} :> {a, b}, {0, Infinity}]], expr]; f1[expr_] := Replace[expr, x_List :> With[{eval = DeleteCases[x, {}]}, eval /; True], {0, Infinity}]; f2[expr_] := expr //. {left___, {}, right___} :> {left, right};

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• Java: Inputting text from a file using split

  - by 00PS

  I am inputting an adjacency list for a graph. There are three columns of data (vertex, destination, edge) separated by a single space. Here is my implementation so far: FileStream in = new FileStream("input1.txt"); Scanner s = new Scanner(in); String buffer; String [] line = null; while (s.hasNext()) { buffer = s.nextLine(); line = buffer.split("\\s+"); g.add(line[0]); System.out.println("Added vertex " + line[0] + "."); g.addEdge(line[0], line[1], Integer.parseInt(line[2])); System.out.println("Added edge from " + line[0] + " to " + line[1] + " with a weight of " + Integer.parseInt(line[2]) + "."); } System.out.println("Size of graph = " + g.size()); Here is the output: Added vertex a. Added edge from a to b with a weight of 9. Exception in thread "main" java.lang.NullPointerException at structure5.GraphListDirected.addEdge(GraphListDirected.java:93) at Driver.main(Driver.java:28) I was under the impression that line = buffer.split("\\s+"); would return a 2 dimensional array of Strings to the variable line. It seemed to work the first time but not the second. Any thoughts? I would also like some feedback on my implementation of this problem. Is there a better way? Anything to help out a novice! :)

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• Multithreading for loop while maintaining order

  - by David

  I started messing around with multithreading for a CPU intensive batch process I'm running. Essentially I'm trying to condense multiple single page tiffs into single PDF documents. This works fine with a foreach loop or standard iteration but can be very slow for several 100 page documents. I tried the following based on a some examples I found to use multithreading and it has significant performance improvements however it obliterates the page order instead of 1,2,3,4 it will be 1,3,4,2,6,5 on what thread completes first. My question is how would I utilize this technique while maintaining the page order and if I can will it negate the performance benefit of the multithreading? Thank you in advance. PdfDocument doc = new PdfDocument(); string mail = textBox1.Text; string[] split = mail.Split(new string[] { Environment.NewLine }, StringSplitOptions.None); int counter = split.Count(); // Source must be array or IList. var source = Enumerable.Range(0, 100000).ToArray(); // Partition the entire source array. var rangePartitioner = Partitioner.Create(0, counter); double[] results = new double[counter]; // Loop over the partitions in parallel. Parallel.ForEach(rangePartitioner, (range, loopState) => { // Loop over each range element without a delegate invocation. for (int i = range.Item1; i < range.Item2; i++) { f_prime = split[i].Replace(" " , ""); PdfPage page = doc.AddPage(); XGraphics gfx = XGraphics.FromPdfPage(page); XImage image = XImage.FromFile(f_prime); double x = 0; gfx.DrawImage(image, x, 0); } });

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• Creating a OS X Cocoa App Web View in Xcode 5.0.1

  - by user1822824

  I created a HTML5 web app that I’m trying to wrap in a web view and submit to the Mac App Store. I’ve done the following: 1) Opened Xcode 5.0.1 and selected “Create a new Xcode project” 2) Under “OS X” I selected “Application” then I selected “Cocoa Application” then “Next” 3) I entered a “Product Name” and a “Company Identifier” then selected “Next” (I left all the other settings untouched) then “Create” 4) Under “General” “Deployment Info” “Deployment Target” I selected 10.6 — because I want the app to be compatible with all versions of OS X that support the Mac App Store 5) I clicked “MainMenu.xib” and selected “Window - My App” 6) From the “Object library” I drug the “Web View” object into my window and made it fill the window size 7) I saved my project and click the Play button in the upper left corner of Xcode The app tries to open but freezes. I don’t get an error in Xcode but it does open “main.m” and highlight “return NSApplicationMain(argc, argv);” in green and says “Thread 1: signal SIGABRT” I was hoping that someone could clarify why this isn’t working? And provide me with the last step to link the web view object? I searched Google and found tutorials for iOS and a few for OS X but for different versions of Xcode.

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• Trouble with go tour crawler exercise

  - by David Mason

  I'm going through the go tour and I feel like I have a pretty good understanding of the language except for concurrency. On slide 71 there is an exercise that asks the reader to parallelize a web crawler (and to make it not cover repeats but I haven't gotten there yet.) Here is what I have so far: func Crawl(url string, depth int, fetcher Fetcher, ch chan string) { if depth <= 0 { return } body, urls, err := fetcher.Fetch(url) if err != nil { ch <- fmt.Sprintln(err) return } ch <- fmt.Sprintf("found: %s %q\n", url, body) for _, u := range urls { go Crawl(u, depth-1, fetcher, ch) } } func main() { ch := make(chan string, 100) go Crawl("http://golang.org/", 4, fetcher, ch) for i := range ch { fmt.Println(i) } } The issue I have is where to put the close(ch) call. If I put a defer close(ch) somewhere in the Crawl method, then I end up writing to a closed channel in one of the spawned goroutines, since the method will finish execution before the spawned goroutines do. If I omit the call to close(ch), as is shown in my example code, the program deadlocks after all the goroutines finish executing but the main thread is still waiting on the channel in the for loop since the channel was never closed.

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• C# WinForms populating TreeView from List<myObj>

  - by user743354

  I have this structure of classes: public class L3Message { public int Number { get; set; } public string MessageName { get; set; } public string Device { get; set; } public string Time { get; set; } public string ScramblingCode { get; set; } public List<Parameter> Parameters { get; set; } public L3Message() { Parameters = new List<Parameter>(); } } public class Parameter { public int numOfWhitespaces { get; set; } public string ParameterName { get; set; } public string ParameterValue { get; set; } public Parameter Parent { get; set; } public List<Parameter> SubParameters { get; set; } public Parameter() { SubParameters = new List<Parameter>(); } } So, as return type from one of my Methods I have List of L3Messages (List < L3Message ), and I need to map that to TreeView in WinForms (populate TreeView from that List). If possible, I would like to that in separate thread. How can I achieve that?

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• How do I get my Windows Forms application to use a custom main function and get access to the Applic

  - by burble

  Hi Folks I am trying to use a Main () function in a class to control the program flow in my vb .net Windows Forms application. I have added a splash screen component and a login screen, and customised my main sdi form. I have set the startup form to be my main function in the Application Page of the Project Designer, and everything seems to work fine(ish). However, I would like to use: Me.MinimumSplashScreenDisplayTime = 5000 to ensure that the splash screen is visible, but it is not recognised by the system unless I tick the Enable Application Framework check box on the Project Designer. If I do this, on startup the program ignores the login and splash screens and all my customisation and just displays a default Form1, even though I have also specified my splash screen in the AF dropdown list. Of course, there are alternative ways to delay a splash screen, such as putting the thread temporarily to sleep (which didn't seem to work), but I suspect that there are other things in the AF that I may want to use. Any suggestions on how I can get round this please, and get a sensible means of controlling program flow? Any thoughts on the best overall structure for organising program flow would also be helpful too. I am concerned both about going down a Microsoft or an alternative custom route that may cause me problems later, as the application becomes more complex. Thankses.

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• Why does Perl lose foreign characters on Windows; can this be fixed (if so, how)?

  - by Alex R

  Note below how ã changes to a. NOTE2: Before you blame this on CMD.EXE and Windows pipe weirdness, see Experiment 2 below which gets a similar problem using File::Find. The particular problem I'm trying to fix involves working with image files stored on a local drive, and manipulating the file names which may contain foreign characters. The two experiments shown below are intermediate debugging steps. The ã character is common in latin languages. e.g. http://pt.wikipedia.org/wiki/Cão Experiment 1 Experiment 2 To get around my particular problem, I tried using File::Find instead of piped input. The issue actually gets worse: Debugging update: I tried some of the tricks listed at http://perldoc.perl.org/perlunicode.html, e.g. use utf8, use feature 'unicode_strings', etc, to no avail. Environment and Version Info The OS is Windows 7, 64-bit. The Perl is: This is perl 5, version 12, subversion 2 (v5.12.2) built for MSWin32-x64-multi-thread (with 8 registered patches, see perl -V for more detail) Copyright 1987-2010, Larry Wall Binary build 1202 [293621] provided by ActiveState http://www.ActiveState.com Built Sep 6 2010 22:53:42

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• .NET: bool vs enum as a method parameter

  - by Julien Lebosquain

  Each time I'm writing a method that takes a boolean parameter representing an option, I find myself thinking: "should I replace this by an enum which would make reading the method calls much easier?". Consider the following with an object that takes a parameter telling whether the implementation should use its thread-safe version or not (I'm not asking here if this way of doing this is good design or not, only the use of the boolean): public void CreateSomeObject(bool makeThreadSafe); CreateSomeObject(true); When the call is next to the declaration the purpose of the parameter seems of course obvious. When it's in some third party library you barely know, it's harder to immediately see what the code does, compared to: public enum CreationOptions { None, MakeThreadSafe } public void CreateSomeObject(CreationOptions options); CreateSomeObject(CreationOptions.MakeThreadSafe); which describes the intent far better. Things get worse when there's two boolean parameters representing options. See what happened to ObjectContext.SaveChanges(bool) between Framework 3.5 and 4.0. It has been obsoleted because a second option has been introduced and the whole thing has been converted to an enum. While it seems obvious to use an enumeration when there's three elements or more, what's your opinion and experiences about using an enum instead a boolean in these specific cases?

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• Could someone help me debug my app (not very big)?

  - by Alex

  Not sure if this kind of help is accepted to ask for here, tell me if it isn't. It has to get done before tomorrow, it's not entirerly finished but it should work somewhat ok by now. I'm trying to use the Eclipse debugger (not very used to it). I have my top-level or main class, which is Game, in which I have a constructor and a main method. In the main method I create a new "Game", initiating the constructor. public static void main(String[] args){ Game chess = new Game(); } public Game(){ Board board = new Board(); That's the first thing the debugger reacts to: Thread [main] (Suspended) ClassNotFoundException(Object).<init>() line: 20 [local variables unavailable] ClassNotFoundException(Throwable).<init>(String, Throwable) line: 217 ClassNotFoundException(Exception).<init>(String, Throwable) line: not available ClassNotFoundException.<init>(String) line: not available URLClassLoader$1.run() line: not available AccessController.doPrivileged(PrivilegedExceptionAction<T>, AccessControlContext) line: not available [native method] Launcher$ExtClassLoader(URLClassLoader).findClass(String) line: not available Launcher$ExtClassLoader.findClass(String) line: not available Launcher$ExtClassLoader(ClassLoader).loadClass(String, boolean) line: not available Launcher$AppClassLoader(ClassLoader).loadClass(String, boolean) line: not available Launcher$AppClassLoader.loadClass(String, boolean) line: not available Launcher$AppClassLoader(ClassLoader).loadClass(String) line: not available Game.<init>() line: 15 Game.main(String[]) line: 11 Line 11 is the one line in my main method, line 15 is the instantiation of "board".

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• How to perform a Depth First Search iteratively using async/parallel processing?

  - by Prabhu

  Here is a method that does a DFS search and returns a list of all items given a top level item id. How could I modify this to take advantage of parallel processing? Currently, the call to get the sub items is made one by one for each item in the stack. It would be nice if I could get the sub items for multiple items in the stack at the same time, and populate my return list faster. How could I do this (either using async/await or TPL, or anything else) in a thread safe manner? private async Task<IList<Item>> GetItemsAsync(string topItemId) { var items = new List<Item>(); var topItem = await GetItemAsync(topItemId); Stack<Item> stack = new Stack<Item>(); stack.Push(topItem); while (stack.Count > 0) { var item = stack.Pop(); items.Add(item); var subItems = await GetSubItemsAsync(item.SubId); foreach (var subItem in subItems) { stack.Push(subItem); } } return items; } EDIT: I was thinking of something along these lines, but it's not coming together: var tasks = stack.Select(async item => { items.Add(item); var subItems = await GetSubItemsAsync(item.SubId); foreach (var subItem in subItems) { stack.Push(subItem); } }).ToList(); if (tasks.Any()) await Task.WhenAll(tasks); UPDATE: If I wanted to chunk the tasks, would something like this work? foreach (var batch in items.BatchesOf(100)) { var tasks = batch.Select(async item => { await DoSomething(item); }).ToList(); if (tasks.Any()) { await Task.WhenAll(tasks); } } The language I'm using is C#.

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• NullPointerException on Activity Testint Tutorial

  - by Bendik

  Hello, I am currently trying the activity testing tutorial (Found here), and have a problem. It seems that whenever I try to call something inside the UIThread, I get a java.lang.NullPointerException. public void testSpinnerUI() { mActivity.runOnUiThread( new Runnable() { public void run() { mSpinner.requestFocus(); } }); } This gives me: Incomplete: java.lang.NullPointerException and nothing else. I have tried this on two different samples now, with the same result. I tried with a try/catch clause around the mSpinner.requestFocus() call, and it seems that mSpinner is null inside the thread. I have set it properly up with the setUp() function found in the same sample, and a quick assertNotNull( mSpinner ) shows me that mSpinner is in fact not null after the setUp() function. What can be the cause of this? EDIT; ok, some more testing has been done. It seems that the application that is being tested resets between each test. This essentially makes me have to reinstantiate all variables between each test. Is this normal?

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• Reading PDF form field data from Flex 4 ( via php or coldfusion )

  - by Brian Russel Davis

  Been searching web for an answer for this for a MONTH. I am not an expert in Coldfusion. So supposedly this is easy in CF -- but the mark-up confuses the HECK out of me. So here I am. I have managed to import and read a PDF using the CF Proxy for Actionscript: http://forums.adobe.com/thread/754629?tstart=0 --- BUT --- After all my trouble there, the precious form filed information that I was looking for was not there in the PDF info object. GRRRR. So I am back to looking for a way to do this with CFC's or CFM's or PHP. All I want is this: Read the PDF from a Flex app. GET the form field information. WRITE a new PDF with the form field values. I have found so many close but no cigar options ... and I have tried so many that failed. There are so many free PDF this and that out there. But Adobe seems to reserve the real functionality for themselves. All the free options don't seem to have access to the form data? Anyways I am so exhausted with looking for ways to do this. I need help!

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• Looping through a method without for/foreach/while

  - by RichK

  Is there a way of calling a method/lines of code multiple times not using a for/foreach/while loop? For example, if I were to use to for loop: int numberOfIterations = 6; for(int i = 0; i < numberOfIterations; i++) { DoSomething(); SomeProperty = true; } The lines of code I'm calling don't use 'i' and in my opinion the whole loop declaration hides what I'm trying to do. This is the same for a foreach. I was wondering if there's a looping statement I can use that looks something like: do(6) { DoSomething(); SomeProperty = true; } It's really clear that I just want to execute that code 6 times and there's no noise involving index instantiating and adding 1 to some arbitrary variable. As a learning exercise I have written a static class and method: Do.Multiple(int iterations, Action action) Which works but scores very highly on the pretentious scale and I'm sure my peers wouldn't approve. I'm probably just being picky and a for loop is certainly the most recognisable, but as a learning point I was just wondering if there (cleaner) alternatives. Thanks. (I've had a look at this thread, but it's not quite the same) http://stackoverflow.com/questions/2248985/using-ienumerable-without-foreach-loop

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• BackgroundWorker acting bizarrely...

  - by vdh_ant

  Hi guys I'm working on some code that calls a service. This service call could fail and if it does I want the system to try again until it works or too much time has passed. I am wondering where I am going wrong as the following code doesn't seem to be working correctly... It randomly only does one to four loops... protected virtual void ProcessAsync(object data, int count) { var worker = new BackgroundWorker(); worker.DoWork += (sender, e) => { throw new InvalidOperationException("oh shiznit!"); }; worker.RunWorkerCompleted += (sender, e) => { //If an error occurs we need to tell the data about it if (e.Error != null) { count++; System.Threading.Thread.Sleep(count * 5000); if (count <= 10) { if (count % 5 == 0) this.Logger.Fatal("LOAD ERROR - The system can't load any data", e.Error); else this.Logger.Error("LOAD ERROR - The system can't load any data", e.Error); this.ProcessAsync(data, count); } } }; worker.RunWorkerAsync(); } Cheers Anthony

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• Is a web-server (e.g servlets) a good solution for an IM server?

  - by John

  I'm looking at a new app, broadly speaking an IM application with a strong client-server model - all communications go through a server so they can be logged centrally. The server will be Java in some form, clients could at this point be anything from a .NET Desktop app to Flex/Silverlight, to a simple web-interface using JS/AJAX. I had anticipated doing the server using standard J2EE so I get a thread-safe, multi-user server for 'free'... to make things simple let's say using Servlets (but in practice SpringMVC would be likely). This all seemed very neat but I'm concerned if the stateless nature of Servlets is the best approach. If my memory of servlets (been a year or two) is right, each time a client sent a HTTP request, typically a new message entered by the user, the servlet could not assume it had the user/chat in memory and might have to get it from the DB... regardless it has to look it up. Then it either has to use some PUSH system to inform other members of the chat, or cache that there are new messages, for other clients who poll the server using AJAX or similar - and when they poll it again has to lookup the chat, including new messages, and send the new data. I'm wondering if a better system would be the server is running core Java, and implements a socket-based communication with clients. This allows much more immediate data transfer and is more flexible if say the IM client included some game you could play. But then you're writing a custom server and sockets don't sound very friendly to a browser-based client on current browsers. Am I missing some big piece of the puzzle here, it kind of feels like I am? Perhaps a better way to ask the question would simply be "if the client was browser-based using HTML/JS and had to run on IE7+,FF2+ (i.e no HTML5), how would you implement the server?" edit: if you are going to suggest using XMPP, I have been trying to get my head around this in another question, so please consider if that's a more appropriate place to discuss this specifically.

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• How do I insert XML into another XML file with XSLT?

  - by Sandra

  Hello, I looked at this thread to find out how to insert XML into XML with XSLT http://stackoverflow.com/questions/862954/insert-xml-node-at-a-specific-position-of-an-existing-document But I have a problem since I need to insert XML between two grand child nodes. For example I want to insert <s>...</s> between <r>...</r> and <t>...</t> in this file <root> <child1> <a>...</a> <r>...</r> <t>...</t> <z>...</z> </child1> </root> to create this file <root> <child1> <a>...</a> <r>...</r> <s>...</s> <t>...</t> <z>...</z> </child1> </root> Thanks for your help.

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• Using multiple Qt (SQL) Models

  - by radix07

  I have a near real-time application that I am using Qt and an SQLite database to run. I am curious if it is safe to have two separate models access a database at once. I know 2 separate views can access a model just fine, but I can't find any document addressing this. I also realize that SQLite is thread safe for reading, so I don't see a real issue to doing this from the SQLite part of things... Basically I want to use a QSqlTableModel to do the real-time read and write in the background and at the same time use a QSqlQueryModel to give the user desired data. Since I may be doing lots of filtering in the background using the table model I can't use it as the main view as well. I have gotten this to work for the most part, but am not sure if this is the best way to do this. If the models act like multiple SQL queries I don't believe this should be an issue, but I would like to know from someone I bit more knowledgeable about this stuff since this is pretty new to me. Thanks

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• Does the Java Memory Model (JSR-133) imply that entering a monitor flushes the CPU data cache(s)?

  - by Durandal

  There is something that bugs me with the Java memory model (if i even understand everything correctly). If there are two threads A and B, there are no guarantees that B will ever see a value written by A, unless both A and B synchronize on the same monitor. For any system architecture that guarantees cache coherency between threads, there is no problem. But if the architecture does not support cache coherency in hardware, this essentially means that whenever a thread enters a monitor, all memory changes made before must be commited to main memory, and the cache must be invalidated. And it needs to be the entire data cache, not just a few lines, since the monitor has no information which variables in memory it guards. But that would surely impact performance of any application that needs to synchronize frequently (especially things like job queues with short running jobs). So can Java work reasonably well on architectures without hardware cache-coherency? If not, why doesn't the memory model make stronger guarantees about visibility? Wouldn't it be more efficient if the language would require information what is guarded by a monitor? As i see it the memory model gives us the worst of both worlds, the absolute need to synchronize, even if cache coherency is guaranteed in hardware, and on the other hand bad performance on incoherent architectures (full cache flushes). So shouldn't it be more strict (require information what is guarded by a monitor) or more lose and restrict potential platforms to cache-coherent architectures? As it is now, it doesn't make too much sense to me. Can somebody clear up why this specific memory model was choosen? EDIT: My use of strict and lose was a bad choice in retrospect. I used "strict" for the case where less guarantees are made and "lose" for the opposite. To avoid confusion, its probably better to speak in terms of stronger or weaker guarantees.

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• Response Redirect - Open Link in New Window

  - by bacis09

  First, I've taken the time to review this question which seems to be the most similar, however, the solution that seems to have been selected will not work in my scenario.Not to mention I worry about some of the comments claiming it to be brittle or an inadequate solution. http://stackoverflow.com/questions/104601/asp-net-response-redirect-to-new-window -We have an XML document which basically contains all of the information for a Side menu. -We have numerous URLS which are stored in a constants class. -One of the elements in a string of XML (well call it label) is used to determine if the menu item is created as a LinkButton or a Label. -Links use a custom user control that is used standard for all links across the application (why suggestion on similar thread doesn't work - I don't want all links to open in a new window - just one) -One of the elements in a string of XML (well call it function) is used in a Switch statement to generate our links using Response Redirect. It may look something like this. switch (function) { case goto 1: string url; if (user_group == 1) { url = Constants.CONSTANT1 } else { url = Constants.CONSTANT2 } Response.Redirect(url) case goto 2: ...... default: ...... break; } Given this scenario, I'm trying to find the best way to quickly open a New Window, when a specific case in this switch statement is met. Can it be done with Response Redirect (this seems to be arguable - people say no it can't, yet other people say they have made it work)? If not, what alternative can work here?

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• [java] tcp socket communication [send and recieve help]

  - by raven

  hello, I am creating a Chat in java. I have a method (onMouseRelease) inside an object that creates a tcp server and waits for a socket ServerSocket server = new ServerSocket(port); Socket channel = server.accept(); now I want to make a thread that will loop and read data from the socket, so that once the user on the other side sent me a string, I will extract the data from the socket [or is it called packet? sry I am new to this], and update a textbox to add the additional string from the socket [or packet?]. I have no idea how to READ (extract) the information from the scoket [/packet] and then update it into a JTextArea which is called userOutput. And how to Send a string to the other client, so that it will also could read the new data and update its JTextArea. (from what I know, for a 2 sided tcp communication you need one computer to host a server and the other to connect [as a client] and once the connection is set the client can also recieve new information from the socket. Is that true? and please tell me how ) Any help appreciated !! I know this is abit long but I have searched allot and didn't understand [I saw something like printwriter but failed to understand].

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