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• Adobe Air update error "file version doesn't match" but it's the same!...

  - by baroquedub

  I'm using Claus Wahlers' AIR Remote Updater class (codeazur.com.br/lab/airremoteupdater/). All works fine and an update is triggered if the remote version is newer. The newer file is downloaded and the update starts. However I then get "an error has occured" message: "This application cannot be installed because this installer has been mis-configured" (The same file will update without errors when run manually "Would you like to replace the currently installed version?" Choosing 'replace' works fine) I have enabled Air Application Installer logging and I can see that both the app id and the pub id match - this seems to be a common reason for this problem (forums.adobe.com/thread/243421?tstart=60) The error given in the log file is as follows: AIR file version doesn't match Requested version: ; AIR file version: 1.0.2 But if I unzip the new app file and look at META-INF\AIR\application.xml the version designator shows <version>1.0.2</version> As requested! The log file is also showing me where the newer file is being downloaded and unpacked. If I look at the application.xml file in that directory: Unpackaging to C:\Documents and Settings\myusername\Local Settings\Temp\fla893D.tmp the version designator also shows <version>1.0.2</version> I don't get it?! The log tells me that the requested file version doesn't match but it's exactly the same as what's shown in the version designator of the downloaded update package... This is driving me crazy. Can anyone help?

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• java bubblesort with acm dialog

  - by qzar

  Hi, the program gives following exception: Exception in thread "main" java.lang.NullPointerException at myclasses.BubbleSort.run(BubbleSort.java:42) at acm.program.Program.runHook(Program.java:1519) at acm.program.Program.startRun(Program.java:1508) at acm.program.Program.start(Program.java:729) at myclasses.BubbleSort.main(BubbleSort.java:49) what is wrong? thank you very much! package myclasses; import acm.program.DialogProgram; public class BubbleSort extends DialogProgram { int[] array; public int[] getArray() { return array; } public void setArray(int[] array) { this.array = array; } void swap(int firstPos, int secondPos) { int temp = array[firstPos]; array[firstPos] = array[secondPos]; array[secondPos] = temp; } public void bubblesort() { int i, j, k; for (i = 1; i < array.length; i++) { j = i; k = array[i]; while (j > 0 && array[j - 1] > k) { array[j] = array[j - 1]; --j; } array[j] = k; } } public void run() { BubbleSort a = new BubbleSort(); a.setArray(new int[] {1, 3, 5, 7, 6, 2}); a.bubblesort(); StringBuffer sb = new StringBuffer(a.array.length * 2); for (int i = 0; i < getArray().length; i++) sb.append(getArray()[i]).append(" "); println(sb); } public static void main(String[] args) { new BubbleSort().start(args); } }

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• InvalidOperationException: The Undo operation encountered a context that is different from what was

  - by McN

  I got the following exception: Exception Type: System.InvalidOperationException Exception Message: The Undo operation encountered a context that is different from what was applied in the corresponding Set operation. The possible cause is that a context was Set on the thread and not reverted(undone). Exception Stack: at System.Threading.SynchronizationContextSwitcher.Undo() at System.Threading.ExecutionContextSwitcher.Undo() at System.Threading.ExecutionContext.runFinallyCode(Object userData, Boolean exceptionThrown) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteBackoutCodeHelper(Object backoutCode, Object userData, Boolean exceptionThrown) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Net.ContextAwareResult.Complete(IntPtr userToken) at System.Net.LazyAsyncResult.ProtectedInvokeCallback(Object result, IntPtr userToken) at System.Net.Sockets.BaseOverlappedAsyncResult.CompletionPortCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* nativeOverlapped) at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP) Exception Source: mscorlib Exception TargetSite.Name: Undo Exception HelpLink: The application is a Visual Studio 2005 (.Net 2.0) console application. It is a server for multiple TCP/IP connections, doing asynchronous socket reads and synchronous socket writes. In searching for an answer I came across this post which talks about a call to Application.Doevents() which I don't use in my code. I also found this post which has a resolution involved with Component which I also don't use in my code. The application does reference a library that I created that contains custom user controls and components, but they are not being used by the application. Question: What caused this to happen and how do I prevent this from happening again? Or a more realistic question: What does this exception actually mean? How is "context" defined in this situation? Anything that can help me understand what is going on would be very much appreciated.

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• How do repos (SVN, GIT) work?

  - by masfenix

  I read SO nearly everyday and mostly there is a thread about source control. I have a few questions. I am going to use SVN as example. 1) There is a team (small, large dosnt matter). In the morning everyone checks out the code to start working. At noon Person A commits, while person B still works on it. What happens when person B commits? how will person B know that there is an updated file? 2) I am assuming the answer to the first question is "run an update command which tells you", ok so person B finds out that the file they have been working on all morning in changed. When they see the udpated file, it seems like person A has REWRITTEN the file for better performance. What does person B do? Seems like there whole day was a waste of time. Or if they commit their version then its a waste of person A's time? 3) What are branches? thanks, and if anyone knows a laymen terms pdf or something that explains it that would be awesome.

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• Strange problem with simple multithreading program in Java

  - by Elizabeth

  Hello, I am just starting play with multithreading programming. I would like to my program show alternately character '-' and '+' but it doesn't. My task is to use synchronized keyword. As far I have: class FunnyStringGenerator{ private char c; public FunnyStringGenerator(){ c = '-'; } public synchronized char next(){ if(c == '-'){ c = '+'; } else{ c = '-'; } return c; } } class ThreadToGenerateStr implements Runnable{ FunnyStringGenerator gen; public ThreadToGenerateStr(FunnyStringGenerator fsg){ gen = fsg; } @Override public void run() { for(int i = 0; i < 10; i++){ System.out.print(gen.next()); } } } public class Main{ public static void main(String[] args) throws IOException { FunnyStringGenerator FSG = new FunnyStringGenerator(); ExecutorService exec = Executors.newCachedThreadPool(); for(int i = 0; i < 20; i++){ exec.execute(new ThreadToGenerateStr(FSG)); } } } EDIT: I also testing Thread.sleep in run method instead for loop.

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• Updating an application OTA

  - by Bostjan

  I'm developing an application that will be available from a website (market probably as well). The problem I'm having at the moment is how to handle the updates to the app. I know how to check the version against the current one and I know if I need to update it. Question is...how? Is there a way I can download an APK from the website and start the install process? The user will have to confirm of course, but I just want to be able to start it for him. At the moment I'm doing this: private void doUpgrade() { // TODO Auto-generated method stub Builder builder = new AlertDialog.Builder(this); builder.setTitle(getString(R.string.upgrade)); builder.setIcon(R.drawable.help); builder.setMessage(getString(R.string.needUpgrade)); builder.setPositiveButton(getString(R.string.ok), new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { // TODO Auto-generated method stub Map<String, String> data = new HashMap<String, String>(); try { HttpResponse re = Registration.doPost("http://www.android-town.com/appRelease/AndroidTown.apk",data); int statusCode = re.getStatusLine().getStatusCode(); closeApp(); } catch (ClientProtocolException e) { e.printStackTrace(); Toast.makeText(getApplicationContext(), getString(R.string.noURLAccess), Toast.LENGTH_SHORT).show(); closeApp(); } catch (IOException e) { e.printStackTrace(); Toast.makeText(getApplicationContext(), getString(R.string.noURLAccess), Toast.LENGTH_SHORT).show(); closeApp(); } } }); builder.setNegativeButton(getString(R.string.cancel), new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { // TODO Auto-generated method stub dialog.cancel(); closeApp(); } }); builder.show(); } But it doesn't really do anything...should I open a webView with the URL? A new runnable thread? Any other way? Please help :) Cheers

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• How to Parse an XML (using XELement) having multiple Namespace ?

  - by Subhen

  Hi I , I get the followinng Xresponse after parsing the XML document: <DIDL-Lite xmlns="urn:schemas-upnp-org:metadata-1-0/DIDL-Lite/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:upnp="urn:schemas-upnp-org:metadata-1-0/upnp/" xmlns:dlna="urn:schemas-dlna-org:metadata-1-0/"> <item id="1182" parentID="40" restricted="1"> <title>Hot Issue</title> </item> As per the earlier thread, When there is a default namespace in the document, you must parse it as if it were a named namespace. For example. XNamespace ns = "urn:schemas-upnp-org:metadata-1-0/DIDL-Lite/"; var xDIDL = xResponse.Element(ns + "DIDL-Lite"); But in my case I have four different name space. I am not getting any results after using the following query , I am getting the response , Not Yeilding any results: XNamespace dc = "http://purl.org/dc/elements/1.1/"; var vAudioData = from xAudioinfo in xResponse.Descendants(ns + "DIDL-lite").Elements("item") select new RMSMedia { strAudioTitle = ((string)xAudioinfo.Element(dc + "title")).Trim(), }; I have no clue whats going on as am new to it. Please help

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• Serial port and checkboxes updating

  - by hradecek

  in my app' i'm recieving data from serial port and save them into two bool arrays. And depends on these array i'm setting checkboxes. But checkboxes are not updating only when i change the tabs.... Here's how i'm doin' it(maybe there's better way how to do it) private void comboBoxCommunication_SelectionChanged(object sender, SelectionChangedEventArgs e) { if (serialPort.IsOpen) { recieveThread.Abort(); serialPort.Close(); } ComboBoxItem cbi = (ComboBoxItem)comboBoxCommunication.SelectedItem; portCommunication = cbi.Content.ToString(); serialPort.PortName = portCommunication; try { serialPort.Open(); recieveThread = new Thread(dataRecieving); prijmiThread.Start(); checkBoxI1.IsChecked = vstupy[0] ? true : false; checkBoxI2.IsChecked = inputs[1] ? true : false; checkBoxI3.IsChecked = inputs[2] ? true : false; checkBoxQ2.IsChecked = outputs[3] ? true : false; } catch (IOException ex) { MessageBox.Show(ex.ToString(), "Error!", MessageBoxButton.OK, MessageBoxImage.Error, MessageBoxResult.OK); } } private void dataRecieving() { if (serialPort.IsOpen) { int i = serialPort.ReadChar(); if (i == 'A') { inputs[0] = true; } else if (i == 'a') { inputs[0] = false; } if (i == 'B') { inputs[1] = true; } else if (i == 'b') { inputs[1] = false; } if (i == 'C') { inputs[2] = true; } else if (i == 'c') { inputs[2] = false; } if (i == 'D') { outputs[0] = true; } else if (i == 'd') { outputs[0] = false; } } }

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• python on apache - getting 404

  - by Kirby

  I edited this question after i found a solution... i need to understand why the solution worked instead of my method? This is likely to be a silly question. I tried searching other questions that are related... but to no avail. i am running Apache/2.2.11 (Ubuntu) DAV/2 SVN/1.5.4 PHP/5.2.6-3ubuntu4.5 with Suhosin-Patch mod_python/3.3.1 Python/2.6.2 i have a script called test.py #! /usr/bin/python print "Content-Type: text/html" # HTML is following print # blank line, end of headers print "hello world" running it as an executable works... /var/www$ ./test.py Content-Type: text/html hello world when i run http://localhost/test.py i get a 404 error. What am i missing? i used this resource to enable python parsing on apache. http://ubuntuforums.org/showthread.php?t=91101 From that same thread... the following code worked.. why? #!/usr/bin/python import sys import time def index(req): # Following line causes error to be sent to browser # rather than to log file (great for debug!) sys.stderr = sys.stdout #print "Content-type: text/html\n" #print """ blah1 = """<html> <head><title>A page from Python</title></head> <body> <h4>This page is generated by a Python script!</h4> The current date and time is """ now = time.gmtime() displaytime = time.strftime("%A %d %B %Y, %X",now) #print displaytime, blah1 += displaytime #print """ blah1 += """ <hr> Well House Consultants demonstration </body> </html> """ return blah1

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• How To Deal With Exceptions In Large Code Bases

  - by peter

  Hi All, I have a large C# code base. It seems quite buggy at times, and I was wondering if there is a quick way to improve finding and diagnosing issues that are occuring on client PCs. The most pressing issue is that exceptions occur in the software, are caught, and even reported through to me. The problem is that by the time they are caught the original cause of the exception is lost. I.e. If an exception was caught in a specific method, but that method calls 20 other methods, and those methods each call 20 other methods. You get the picture, a null reference exception is impossible to figure out, especially if it occured on a client machine. I have currently found some places where I think errors are more likely to occur and wrapped these directly in their own try catch blocks. Is that the only solution? I could be here a long time. I don't care that the exception will bring down the current process (it is just a thread anyway - not the main application), but I care that the exceptions come back and don't help with troubleshooting. Any ideas? I am well aware that I am probably asking a question which sounds silly, and may not have a straightforward answer. All the same some discussion would be good.

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• How to display a busy message over a wpf screen

  - by dave

  Hey, I have a WPF application based on Prism4. When performing slow operations, I want to show a busy screen. I will have a large number of screens, so I'm trying to build a single solution into the framework rather than adding the busy indicator to each screen. These long running operations run in a background thread. This allows the UI to be updated (good) but does not stop the user from using the UI (bad). What I'd like to do is overlay a control with a spinning dial sort of thing and have that control cover the entire screen (the old HTML trick with DIVs). When the app is busy, the control would display thus block any further interaction as well as showing the spinny thing. To set this up, I thought I could just have my app screen in a canvas along with the spinny thing (with a greater ZIndex) then just make the spinny thing visible as required. This, however, is getting hard. Canvases do not seem well set up for this and I think I might be barking up the wrong tree. I would appreciate any help. Thanks.

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• Hide Image Title in Slimbox

  - by Stephen

  My issue is a lot like this solved thread, except I'm using Slimbox 2: http://stackoverflow.com/questions/940994/hide-image-title-tool-tip-popup-on-mouse-rollover-or-hover When you hover over an image, the "Title" attribute pops up. I need HTML in my image title in Slimbox. So, of course, when you're hovering, the "Title" attribute shows all the HTML code. The code works perfectly when you're viewing the image in Slimbox so no problems there. I just need the Title attribute to be hidden/modified not to show this HTML code. I tried to change Q.title in slimbox.js to something else (like captionname). Then changed the HTML to call for: <a href="images/team/large.jpg" title="Joe Smith" captionname="URL" rel="lightbox-team"><img src="images/team/small.jpg" class ="headline" border="1" hspace="2" /></a> "Joe Smith" displays as the Title but when you view the image in Slimbox, captionname does not come up at all and neither does the Title. It's just blank where it should be. What do I need to modify in slimbox2.js to make this work?

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• Using JavaMail to send a mail containing Unicode characters

  - by NoozNooz42

  I'm successfully sending emails through GMail's SMTP servers using the following piece of code: Properties props = new Properties(); props.put("mail.smtp.host", "smtp.gmail.com"); props.put("mail.smtp.socketFactory.port", "465"); props.put("mail.smtp.socketFactory.class","javax.net.ssl.SSLSocketFactory"); props.put("mail.smtp.auth", "true"); props.put("mail.smtp.port", "465"); props.put("mail.smtp.ssl", "true"); props.put("mail.smtp.starttls.enable","true"); props.put("mail.smtp.timeout", "5000"); props.put("mail.smtp.connectiontimeout", "5000"); // Do NOT use Session.getDefaultInstance but Session.getInstance // See: http://forums.sun.com/thread.jspa?threadID=5301696 final Session session = Session.getInstance( props, new javax.mail.Authenticator() { protected PasswordAuthentication getPasswordAuthentication() { return new PasswordAuthentication( USER, PWD ); } }); try { final Message message = new MimeMessage(session); message.setFrom( new InternetAddress( USER ) ); message.setRecipients( Message.RecipientType.TO, InternetAddress.parse( TO ) ); message.setSubject( emailSubject ); message.setText( emailContent ); Transport.send(message); emailSent = true; } catch ( final MessagingException e ) { e.printStackTrace(); } where emailContent is a String that does contain Unicode characters (like the euro symbol). When the email arrives (in another GMail account), the euro symbol has been converted to the ASCII '?' question mark. I don't know much about emails: can email use any character encoding? What should I modify in the code above so that an encoding allowing Unicode characters is used?

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• Async WebRequest Timeout Windows Phone 7

  - by Tyler

  Hi All, I'm wondering what the "right" way of timing out an HttpWebRequest is on Windows Phone7? I've been reading about ThreadPool.RegisterWaitForSingleObject() but this can't be used as WaitHandles throw a Not implemented exception at run time. I've also been looking at ManualReset events but A) Don't understand them properly and B) Don't understand how blocking the calling thread is an acceptable way to implement a time out on an Async request. Here's my existing code sans timeout, can someone please show me how I would add a timeout to this? public static void Get(Uri requestUri, HttpResponseReceived httpResponseReceivedCallback, ICredentials credentials, object userState, bool getResponseAsString = true, bool getResponseAsBytes = false) { var httpWebRequest = (HttpWebRequest)WebRequest.Create(requestUri); httpWebRequest.Method = "GET"; httpWebRequest.Credentials = credentials; var httpClientRequestState = new JsonHttpClientRequestState(null, userState, httpResponseReceivedCallback, httpWebRequest, getResponseAsString, getResponseAsBytes); httpWebRequest.BeginGetResponse(ResponseReceived, httpClientRequestState); } private static void ResponseReceived(IAsyncResult asyncResult) { var httpClientRequestState = asyncResult.AsyncState as JsonHttpClientRequestState; Debug.Assert(httpClientRequestState != null, "httpClientRequestState cannot be null. Fatal error."); try { var webResponse = (HttpWebResponse)httpClientRequestState.HttpWebRequest.EndGetResponse(asyncResult); } }

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• http_access.log on WebSphere 6.1.0.29

  - by DavidG

  I am running WebSphere 6.1.0.29 and I need to track the requests being made to an Enterprise Application. Previously I did this by routing the requests through a proxy server, but I need to repeat the exercise and I figure there must be a simpler way. Does anyone know how to enable HTTP access logging? I have been through the console an thought I had enabled http_access.log and http_error.log via: Application servers server1 HTTP error and NCSA access logging (where 'server1' is the application server) I've enabled the service at startup, and ticked the boxes to enable access logging and error logging - however... nothing has happened. I have restarted the server, restarted the Enterprise apps and even did a "find . -name" for the log files - but they don't seem to be anywhere on the system. I saw on a JavaRanch thread someone suggested writing a custom filter for requests in an application, but this seems like wild overkill - plus I am doing the logs to test a pre-built binary, so I don't want to mess with the code. Anyone have any ideas/suggestions? Help! :-)

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• Issue with Callback method and maintaining CultureInfo and ASP.Net HttpRuntime

  - by Little Larry Sellers

  Hi All, Here is my issue. I am working on an E-commerce solution that is deployed to multiple European countries. We persist all exceptions within the application to SQL Server and I have found that there are records in the DB that have a DateTime in the future! We define the culture in the web.config, for example pt-PT, and the format expected is DD-MM-YYYY. After debugging I found the issue with these 'future' records in the DB is because of Callback methods we use. For example, in our Caching architecture we use Callbacks, as such - CacheItemRemovedCallback ReloadCallBack = new CacheItemRemovedCallback(OnRefreshRequest); When I check the current threads CultureInfo, on these Callbacks it is en-US instead of pt-PT and also the HttpContext is null. If an exception occurs on the Callback our exception manager reports it as MM-DD-YYYY and thus it is persisted to SQL Server incorrectly. Unfortunately, in the exception manager code, we use DateTime.Now, which is fine if it is not a callback. I can't change this code to be culture specific due to it being shared across other verticals. So, why don't callbacks into ASP.Net maintain context? Is there any way to maintain it on this callback thread? What are the best practices here? Thanks.

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• Using `<List>` when dealing with pointers in C#.

  - by Gorchestopher H

  How can I add an item to a list if that item is essentially a pointer and avoid changing every item in my list to the newest instance of that item? Here's what I mean: I am doing image processing, and there is a chance that I will need to deal with images that come in faster than I can process (for a short period of time). After this "burst" of images I will rely on the fact that I can process faster than the average image rate, and will "catch-up" eventually. So, what I want to do is put my images into a <List> when I acquire them, then if my processing thread isn't busy, I can take an image from that list and hand it over. My issue is that I am worried that since I am adding the image "Image1" to the list, then filling "Image1" with a new image (during the next image acquisition) I will be replacing the image stored in the list with the new image as well (as the image variable is actually just a pointer). So, my code looks a little like this: while (!exitcondition) { if(ImageAvailabe()) { Image1 = AcquireImage(); ImgList.Add(Image1); } if(ImgList.Count 0) { ProcessEngine.NewImage(ImgList[0]); ImgList.RemoveAt(0); } } Given the above, how can I ensure that: - I don't replace all items in the list every time Image1 is modified. - I don't need to pre-declare a number of images in order to do this kind of processing. - I don't create a memory devouring monster. Any advice is greatly appreciated.

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• TransactionRequiredException on OptimisticLockException

  - by João Madureira Pires

  Hi there. I have the following class that generates sequencial Card Numbers. I'm trying to recover from OptimisticLockException, by calling recursively the same method. however, i'm getting TransactionRequiredException. Dows anyone knows how to recover from OptimisticLockException in my case? Thanks a lot in advance @Name("simpleAutoIncrementGenerator") public class SimpleAutoIncrementGenerator extends CardNumberGenerator{ private static final long serialVersionUID = 2869548248468809665L; private int numberOfRetries = 0; @Override public String generateNextNumber(CardInstance cardInstance, EntityManager entityManager) { try{ EntityCard card = (EntityCard)entityManager.find(EntityCard.class, cardInstance.getId()); if(card != null){ String nextNumber = ""; String currentNumber = card.getCurrentCardNumber(); if(currentNumber != null && !currentNumber.isEmpty()){ Long numberToInc = Long.parseLong(currentNumber); numberToInc ++; nextNumber = String.valueOf(numberToInc); card.setCurrentCardNumber(nextNumber); // this is just to cause a OptimisticLock Exception try { Thread.sleep(4000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } entityManager.persist(card); entityManager.flush(); return nextNumber; } } }catch (OptimisticLockException oLE) { System.out.println("\n\n\n\n OptimisticLockException \n\n\n\n"); if(numberOfRetries < CentralizedConfig.CARD_NUMBER_GENERATOR_MAX_TRIES){ numberOfRetries ++; return generateNextNumber(cardInstance,entityManager); } }catch (TransactionRequiredException trE) { System.out.println("\n\n\n\n TransactionRequiredException \n\n\n\n"); if(numberOfRetries < CentralizedConfig.CARD_NUMBER_GENERATOR_MAX_TRIES){ numberOfRetries ++; return generateNextNumber(cardInstance,entityManager); } }catch (StaleObjectStateException e) { System.out.println("\n\n\n\n StaleObjectStateException \n\n\n\n"); if(numberOfRetries < CentralizedConfig.CARD_NUMBER_GENERATOR_MAX_TRIES){ numberOfRetries ++; return generateNextNumber(cardInstance,entityManager); } } return null; } }

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• static variable lose its value

  - by user542719

  I have helper class with this static variable that is used for passing data between two classes. public class Helper{ public static String paramDriveMod;//this is the static variable in first calss } this variable is used in following second class mathod public void USB_HandleMessage(char []USB_RXBuffer){ int type=USB_RXBuffer[2]; MESSAGES ms=MESSAGES.values()[type]; switch(ms) { case READ_PARAMETER_VALUE: // read parameter values switch(prm){ case PARAMETER_DRIVE_MODE: // paramet drive mode Helper.paramDriveMod =(Integer.toString(((USB_RXBuffer[4]<< 8)&0xff00))); System.out.println(Helper.paramDriveMod+"drive mode is selectd ");//here it shows the value that I need. ..........}}//let say end switch and method and the following is an third class method use the above class method public void buttonSwitch(int value) throws InterruptedException{ boolean bool=true; int c=0; int delay=(int) Math.random(); while(bool){ int param=3; PARAMETERS prm=PARAMETERS.values()[param]; switch(value){ case 0: value=1; while(c<5){ Thread.sleep(delay); protocol.onSending(3,prm.PARAMETER_DRIVE_MODE.ordinal(),dataToRead,dataToRead.length);//read drive mode System.out.println(Helper.paramDriveMod+" drive mode is ..........in wile loop");//here it shows null value }}//let say end switch and method what is the reason that this variable lose its value?

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• Sharing a COM port over TCP

  - by guinness

  What would be a simple design pattern for sharing a COM port over TCP to multiple clients? For example, a local GPS device that could transmit co-ordinates to remote hosts in realtime. So I need a program that would open the serial port and accept multiple TCP connections like: class Program { public static void Main(string[] args) { SerialPort sp = new SerialPort("COM4", 19200, Parity.None, 8, StopBits.One); Socket srv = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); srv.Bind(new IPEndPoint(IPAddress.Any, 8000)); srv.Listen(20); while (true) { Socket soc = srv.Accept(); new Connection(soc); } } } I would then need a class to handle the communication between connected clients, allowing them all to see the data and keeping it synchronized so client commands are received in sequence: class Connection { static object lck = new object(); static List<Connection> cons = new List<Connection>(); public Socket socket; public StreamReader reader; public StreamWriter writer; public Connection(Socket soc) { this.socket = soc; this.reader = new StreamReader(new NetworkStream(soc, false)); this.writer = new StreamWriter(new NetworkStream(soc, true)); new Thread(ClientLoop).Start(); } void ClientLoop() { lock (lck) { connections.Add(this); } while (true) { lock (lck) { string line = reader.ReadLine(); if (String.IsNullOrEmpty(line)) break; foreach (Connection con in cons) con.writer.WriteLine(line); } } lock (lck) { cons.Remove(this); socket.Close(); } } } The problem I'm struggling to resolve is how to facilitate communication between the SerialPort instance and the threads. I'm not certain that the above code is the best way forward, so does anybody have another solution (the simpler the better)?

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• ExecutorSerrvice memory leak on exception

  - by TofuBeer

  I am having a hard time tracking this down since the profiler keeps crashing (hotspot error). Before I go too deep into figuring it out I'd like to know if I really have a problem or not :-) I have a few thread pools created via: Executors.newFixedThreadPool(10); The threads connect to different web sites and, on occasion, I get connection refused and wind up throwing an exception. When I later on call Future.get() to get the result it will then catch the ExecutionException that wraps the exception that was thrown when the connection could not be made. The program uses a fairly constant amount of memory up until the point in time that the exceptions get thrown (they tend to happen in batches when a particular site is overloaded). After that point the memory again remains constant but at a higher level. So my question is along the lines of is the memory behaviour (reported by "top" on Unix) expected because the exceptions just triggered something or do I probably have an actual leak that I'll need to track down? Additionally when Future.get() throws an exception is there anything else I need to do besides catch the exception (such as call Future.cancel() on it)?

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• Using sigprocmask to implement locks

  - by EpsilonVector

  I'm implementing user threads in Linux kernel 2.4, and I'm using ualarm to invoke context switches between the threads. We have a requirement that our thread library's functions should be uninterruptable, so I looked into blocking signals and learned that using sigprocmask is the standard way to do this. However, it looks like I need to do quite a lot to implement this: sigset_t new_set, old_set; sigemptyset(&new_set); sigaddset(&new_set, SIGALRM); sigprocmask(SIG_BLOCK, &new_set, &old_set); This blocks SIGALARM but it does this with 3 function invocations! A lot can happen in the time it takes for these functions to run, including the signal being sent. The best idea I had to mitigate this was temporarily disabling ualarm, like this: sigset_t new_set, old_set; time=ualarm(0,0); sigemptyset(&new_set); sigaddset(&new_set, SIGALRM); sigprocmask(SIG_BLOCK, &new_set, &old_set); ualarm(time, 0); Which is fine except that this feels verbose. Isn't there a better way to do this?

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• How to improve multi-threaded access to Cache (custom implementation)

  - by Andy

  I have a custom Cache implementation, which allows to cache TCacheable<TKey> descendants using LRU (Least Recently Used) cache replacement algorithm. Every time an element is accessed, it is bubbled up to the top of the LRU queue using the following synchronized function: // a single instance is created to handle all TCacheable<T> elements public class Cache() { private object syncQueue = new object(); private void topQueue(TCacheable<T> el) { lock (syncQueue) if (newest != el) { if (el.elder != null) el.elder.newer = el.newer; if (el.newer != null) el.newer.elder = el.elder; if (oldest == el) oldest = el.newer; if (oldest == null) oldest = el; if (newest != null) newest.newer = el; el.newer = null; el.elder = newest; newest = el; } } } The bottleneck in this function is the lock() operator, which limits cache access to just one thread at a time. Question: Is it possible to get rid of lock(syncQueue) in this function while still preserving the queue integrity?

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• Would an immutable keyword in Java be a good idea?

  - by berry120

  Generally speaking, the more I use immutable objects in Java the more I'm thinking they're a great idea. They've got lots of advantages from automatically being thread-safe to not needing to worry about cloning or copy constructors. This has got me thinking, would an "immutable" keyword go amiss? Obviously there's the disadvantages with adding another reserved word to the language, and I doubt it will actually happen primarily for the above reason - but ignoring that I can't really see many disadvantages. At present great care has to be taken to make sure objects are immutable, and even then a dodgy javadoc comment claiming a component object is immutable when it's in fact not can wreck the whole thing. There's also the argument that even basic objects like string aren't truly immutable because they're easily vunerable to reflection attacks. If we had an immutable keyword the compiler could surely recursively check and give an iron clad guarantee that all instances of a class were immutable, something that can't presently be done. Especially with concurrency becoming more and more used, I personally think it'd be good to add a keyword to this effect. But are there any disadvantages or implementation details I'm missing that makes this a bad idea?

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• Ruby syntax error: unexpected $end, expecting keyword_end

  - by user2839246

  I am supposed to: Capitalize the first letter of string. Capitalize every word except articles (the, a, an), conjunctions (and), and prepositions (in). Capitalize i (as in "I am male."). Specify the first word of a string (I actually have no idea what this means. I'm trying to run the spec file to test other functions). Here's my code: class Book def initialize(string) title(string) end def title(string) arts_conjs_preps = %w{ a an the and but or nor for yet so although because since unless despite in to } array = string.downcase.split array.each do |word| if (word == array[0] || word == "i") then word = word.capitalize if arts_conjs_preps !include?(word) then word = word.capitalize end puts array.join(' ') end end puts Book.new("inferno") Ruby says I'm messing up at: puts Book.new("inferno") <--(right after the last line of code) I get exactly the same error message with this test code: def title(string) array = string.downcase.split array.each do |word| if word == array[0] then word = word.capitalize end array.join(' ') end puts title("dante's inferno") The only other Stack Overflow thread regarding this particular syntax error that did not suggest trailing or missing ends or .s as the root of the problem is here. The last comment recommends deleting and recreating the gemset, Which sounds scary. And I'm not sure how to do. Any thoughts? Simple solution? Resources to help? Solution class Book def initialize(string) title(string) end def title(string) arts_conjs_preps = %w{ a an the and but or nor for yet so although because since unless despite of in to } array = string.downcase.split title = array.map do |word| if (word == array[0] || word == "i") || !arts_conjs_preps.include?(word) word = word.capitalize else word end end puts title.join(' ') end end Book.new("dante's the inferno")

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