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  • Data Aggregation of CSV files java

    - by royB
    I have k csv files (5 csv files for example), each file has m fields which produce a key and n values. I need to produce a single csv file with aggregated data. I'm looking for the most efficient solution for this problem, speed mainly. I don't think by the way that we will have memory issues. Also I would like to know if hashing is really a good solution because we will have to use 64 bit hashing solution to reduce the chance for a collision to less than 1% (we are having around 30000000 rows per aggregation). For example file 1: f1,f2,f3,v1,v2,v3,v4 a1,b1,c1,50,60,70,80 a3,b2,c4,60,60,80,90 file 2: f1,f2,f3,v1,v2,v3,v4 a1,b1,c1,30,50,90,40 a3,b2,c4,30,70,50,90 result: f1,f2,f3,v1,v2,v3,v4 a1,b1,c1,80,110,160,120 a3,b2,c4,90,130,130,180 algorithm that we thought until now: hashing (using concurentHashTable) merge sorting the files DB: using mysql or hadoop or redis. The solution needs to be able to handle Huge amount of data (each file more than two million rows) a better example: file 1 country,city,peopleNum england,london,1000000 england,coventry,500000 file 2: country,city,peopleNum england,london,500000 england,coventry,500000 england,manchester,500000 merged file: country,city,peopleNum england,london,1500000 england,coventry,1000000 england,manchester,500000 The key is: country,city. This is just an example, my real key is of size 6 and the data columns are of size 8 - total of 14 columns. We would like that the solution will be the fastest in regard of data processing.

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  • Looking for a better Factory pattern (Java)

    - by Sam Goldberg
    After doing a rough sketch of a high level object model, I am doing iterative TDD, and letting the other objects emerge as a refactoring of the code (as it increases in complexity). (That whole approach may be a discussion/argument for another day.) In any case, I am at the point where I am looking to refactor code blocks currently in an if-else blocks into separate objects. This is because there is another another value combination which creates new set of logical sub-branches. To be more specific, this is a trading system feature, where buy orders have different behavior than sell orders. Responses to the orders have a numeric indicator field which describes some event that occurred (e.g. fill, cancel). The combination of this numeric indicator field plus whether it is a buy or sell, require different processing buy the code. Creating a family of objects to separate the code for the unique handling each of the combinations of the 2 fields seems like a good choice at this point. The way I would normally do this, is to create some Factory object which when called with the 2 relevant parameters (indicator, buysell), would return the correct subclass of the object. Some times I do this pattern with a map, which allows to look up a live instance (or constructor to use via reflection), and sometimes I just hard code the cases in the Factory class. So - for some reason this feels like not good design (e.g. one object which knows all the subclasses of an interface or parent object), and a bit clumsy. Is there a better pattern for solving this kind of problem? And if this factory method approach makes sense, can anyone suggest a nicer design?

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  • How to solve QPixmap::fromImage memory leak?

    - by dodoent
    Hello everyone! I have a problem with Qt. Here is a part of code that troubles me: void FullScreenImage::QImageIplImageCvt(IplImage *input) { help=cvCreateImage(cvGetSize(input), input->depth, input->nChannels); cvCvtColor(input, help, CV_BGR2RGB); QImage tmp((uchar *)help->imageData, help->width, help->height, help->widthStep, QImage::Format_RGB888); this->setPixmap(QPixmap::fromImage(tmp).scaled(this->size(), Qt::IgnoreAspectRatio, Qt::SmoothTransformation)); cvReleaseImage(&help); } void FullScreenImage::hideOnScreen() { this->hide(); this->clear(); } void FullScreenImage::showOnScreen(IplImage *slika, int delay) { QImageIplImageCvt(slika); this->showFullScreen(); if(delay>0) QTimer::singleShot(delay*1000, this, SLOT(hideOnScreen())); } So, the method showOnScreen uses private method QImageIplImageCvt to create QImage from IplImage (which is used by the openCV), which is then used to create QPixmap in order to show the image in full screen. FullScreenImage class inherits QLabel. After some delay, the fullscreen picture should be hidden, so I use QTimer to trigger an event after some delay. The event handler is the hideOnScreen method which hides the label and should clear the memory. The problem is the following: Whenever I call QPixmap::fromImage, it allocates the memory for the pixmap data and copies the data from QImage memory buffer to the QPixmap memory buffer. After the label is hidden, the QPixmap data still remains allocated, and even worse, after the new QPixmap::fromImage call the new chunk of memory is allocated for the new picture, and the old data is not freed from memory. This causes a memory leak (cca 10 MB per method call with my testing pictures). How can I solve that leak? I've even tried to create a private QPixmap variable, store pixmap created by the QPixmap::fromImage to it, and then tried to call its destructor in hideOnScreen method, but it didn't help. Is there a non-static way to create QPixmap from QImage? Or even better, is there a way to create QPixmap directly from IplImage* ? Thank you in advance for your answers.

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  • How to solve this nullPointer Exception in jasper report?

    - by Kumar
    Hi, I am new to jasper report, I need to create pdf document with BeanDatasource and subreport. I refer the following blog " http://knol.google.com/k/jasper-reports-working-with-beans-and-sub-report# " . I followed all the steps perfectly. While i am running the report using IReport i can get the pdf document with the content. But when we try to create from java program i m getting exception in the following line Line number 110: " JasperFillManager.fillReportToFile("C:/JasperReports/contacts.jasper", parameters, new JRBeanCollectionDataSource(TestPerson.getBeanCollection())); " and this is the following error i am getting in my Eclipse Console window . java.lang.NullPointerException at net.sf.jasperreports.engine.JRPropertiesMap.readObject(JRPropertiesMap.java:185) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at java.io.ObjectStreamClass.invokeReadObject(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.defaultReadFields(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.readArray(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.defaultReadFields(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.defaultReadFields(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.readObject(Unknown Source) at net.sf.jasperreports.engine.util.JRLoader.loadObject(JRLoader.java:88) at net.sf.jasperreports.engine.util.JRLoader.loadObjectFromLocation(JRLoader.java:257) at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluateSubreport(JRFillSubreport.java:308) at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluate(JRFillSubreport.java:257) at net.sf.jasperreports.engine.fill.JRFillElementContainer.evaluate(JRFillElementContainer.java:275) at net.sf.jasperreports.engine.fill.JRFillBand.evaluate(JRFillBand.java:426) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillColumnBand(JRVerticalFiller.java:1380) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillDetail(JRVerticalFiller.java:692) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportStart(JRVerticalFiller.java:255) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:113) at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:891) at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:814) at net.sf.jasperreports.engine.fill.JRFiller.fillReport(JRFiller.java:89) at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:601) at test.TestJasperReport.main(TestJasperReport.java:110)

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  • Java update/install via group policy

    - by Maximus
    I trying to deploy the latest Java RE version via GP, Java 7 update 9. I want to update computers that are currently running an older version of Java, a mixture of 7.6 and 7.7, some computers are running versions as old as 6.31. Some are running a mixture of both. I would also like this GP to install Java if it's not installed. Previously I used push out Java updates to users machines as Java didn't remove the old version. So when it was done the user would restart their browser or pc to start using the latest version. Not the best way to manage it as it leaves the old version installed but it worked. I've created group policies before for printer deployment, log on drive mapping scripts, but never software deployment. I've extracted the Java MSI and created a transform file to suppress reboot etc using orca. As described on this site http://ivan.dretvic.com/2011/06/how-to-package-and-deploy-java-jre-1-6-0_26-via-group-policy/. I have also tried saving the edited MSI directly and that didn't work either. But it just won't deploy. I have tried to enable logging as suggested on this site http://openofficetechnology.com/node/32, GPO logging via UserEnvDebugLevel, Software deployment logging via AppmgmtDebugLevel and MSI logging, but there is no log C:\Windows\Debug\UserMode\userenv.log being created. The windows event viewer has the following errors: Error 24/10/2012 11:44:04 AM - "Failed to apply changes to software installation settings. Software changes could not be applied. A previous log entry with details should exist. The error was : %%1612" Information 24/10/2012 11:44:04 AM - "The removal of the assignment of application Java 7 Update 9 - FB Java Transform from policy JavaDeploy succeeded." Error 24/10/2012 11:44:04 AM - "The install of application Java 7 Update 9 - FB Java Transform from policy JavaDeploy failed. The error was : %%1612" There is a log created for MSI logging and it's as below. It says the source is invalid but it exists on the share and the PC that I'm testing has permissions and I've included the recommendation here Group Policy installation failed error 1274 to enable "Always wait for the network at computer startup and logon" === Verbose logging started: 24/10/2012 11:43:59 Build type: SHIP UNICODE 5.00.7601.00 Calling process: C:\Windows\system32\svchost.exe === MSI (c) (9C:EC) [11:43:59:898]: Resetting cached policy values MSI (c) (9C:EC) [11:43:59:898]: Machine policy value 'Debug' is 3 MSI (c) (9C:EC) [11:43:59:898]: ******* RunEngine: ******* Product: {26a24ae4-039d-4ca4-87b4-2f83217009ff} ******* Action: ******* CommandLine: ********** MSI (c) (9C:EC) [11:43:59:898]: Client-side and UI is none or basic: Running entire install on the server. MSI (c) (9C:EC) [11:43:59:898]: Grabbed execution mutex. MSI (c) (9C:EC) [11:44:03:431]: Cloaking enabled. MSI (c) (9C:EC) [11:44:03:431]: Attempting to enable all disabled privileges before calling Install on Server MSI (c) (9C:EC) [11:44:03:439]: Incrementing counter to disable shutdown. Counter after increment: 0 MSI (s) (2C:70) [11:44:03:574]: Running installation inside multi-package transaction {26a24ae4-039d-4ca4-87b4-2f83217009ff} MSI (s) (2C:70) [11:44:03:574]: Grabbed execution mutex. MSI (s) (2C:7C) [11:44:03:607]: Resetting cached policy values MSI (s) (2C:7C) [11:44:03:607]: Machine policy value 'Debug' is 3 MSI (s) (2C:7C) [11:44:03:607]: ******* RunEngine: ******* Product: {26a24ae4-039d-4ca4-87b4-2f83217009ff} ******* Action: ******* CommandLine: ********** MSI (s) (2C:7C) [11:44:03:607]: Machine policy value 'DisableUserInstalls' is 0 MSI (s) (2C:7C) [11:44:03:623]: User policy value 'SearchOrder' is 'nmu' MSI (s) (2C:7C) [11:44:03:624]: User policy value 'DisableMedia' is 0 MSI (s) (2C:7C) [11:44:03:624]: Machine policy value 'AllowLockdownMedia' is 0 MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Media enabled only if package is safe. MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Looking for sourcelist for product {26a24ae4-039d-4ca4-87b4-2f83217009ff} MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Adding {26a24ae4-039d-4ca4-87b4-2f83217009ff}; to potential sourcelist list (pcode;disk;relpath). MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Now checking product {26a24ae4-039d-4ca4-87b4-2f83217009ff} MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Media is enabled for product. MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Attempting to use LastUsedSource from source list. MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Processing net source list. MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Trying source \\server\share\deployment\Java\stable\x32\. MSI (s) (2C:7C) [11:44:03:650]: Note: 1: 2303 2: 5 3: \\server\share\ MSI (s) (2C:7C) [11:44:03:650]: Note: 1: 1325 2: deployment MSI (s) (2C:7C) [11:44:03:650]: ConnectToSource: CreatePath/CreateFilePath failed with: -2147483648 1325 -2147483648 MSI (s) (2C:7C) [11:44:03:650]: ConnectToSource (con't): CreatePath/CreateFilePath failed with: -2147483648 -2147483648 MSI (s) (2C:7C) [11:44:03:650]: SOURCEMGMT: net source '\\server\share\deployment\Java\stable\x32\' is invalid. MSI (s) (2C:7C) [11:44:03:650]: Note: 1: 1706 2: -2147483647 3: jre1.7.0_09.msi MSI (s) (2C:7C) [11:44:03:650]: SOURCEMGMT: Processing media source list. MSI (s) (2C:7C) [11:44:04:668]: Note: 1: 2203 2: 3: -2147287037 MSI (s) (2C:7C) [11:44:04:668]: SOURCEMGMT: Source is invalid due to missing/inaccessible package. MSI (s) (2C:7C) [11:44:04:668]: Note: 1: 1706 2: -2147483647 3: jre1.7.0_09.msi MSI (s) (2C:7C) [11:44:04:668]: SOURCEMGMT: Processing URL source list. MSI (s) (2C:7C) [11:44:04:668]: Note: 1: 1402 2: UNKNOWN\URL 3: 2 MSI (s) (2C:7C) [11:44:04:668]: Note: 1: 1706 2: -2147483647 3: jre1.7.0_09.msi MSI (s) (2C:7C) [11:44:04:668]: Note: 1: 1706 2: 3: jre1.7.0_09.msi MSI (s) (2C:7C) [11:44:04:668]: SOURCEMGMT: Failed to resolve source MSI (s) (2C:7C) [11:44:04:668]: MainEngineThread is returning 1612 MSI (s) (2C:70) [11:44:04:670]: User policy value 'DisableRollback' is 0 MSI (s) (2C:70) [11:44:04:670]: Machine policy value 'DisableRollback' is 0 MSI (s) (2C:70) [11:44:04:670]: Incrementing counter to disable shutdown. Counter after increment: 0 MSI (s) (2C:70) [11:44:04:670]: Note: 1: 1402 2: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer\Rollback\Scripts 3: 2 MSI (s) (2C:70) [11:44:04:671]: Note: 1: 1402 2: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer\Rollback\Scripts 3: 2 MSI (s) (2C:70) [11:44:04:671]: Note: 1: 1402 2: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer\InProgress 3: 2 MSI (s) (2C:70) [11:44:04:671]: Note: 1: 1402 2: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer\InProgress 3: 2 MSI (s) (2C:70) [11:44:04:671]: Decrementing counter to disable shutdown. If counter >= 0, shutdown will be denied. Counter after decrement: -1 MSI (s) (2C:70) [11:44:04:671]: Restoring environment variables MSI (c) (9C:EC) [11:44:04:675]: Decrementing counter to disable shutdown. If counter >= 0, shutdown will be denied. Counter after decrement: -1 MSI (c) (9C:EC) [11:44:04:675]: MainEngineThread is returning 1612 === Verbose logging stopped: 24/10/2012 11:44:04 === I'm not sure what my next approach should be. Any help would be much appreciated. Thanks.

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  • Custom model binder for model inner property

    - by Andrej Kaurin
    My model is like this public class MyModel { string ID {get;set;} string Title {get;set;} MyOtherModel Meta {get;set;} } How to define custom model binder for type (MyOtherModel) so when default binder binds MyModel it calls custom model binder for 'Meta' property. I registered it in App start like: ModelBinders.Binders[typeof(MyOtherModel)] = new MyCustomBinder(); but this doesn't work. Any idea or any good article with more infor regarding to model binders?

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  • NoSuchPortException using RXTX Java library on Windows?

    - by Steve
    I have followed the instructions to setup rxtx on windows from http://www.jcontrol.org/download/readme_rxtx_en.html. What I did exactly was copy rxtxSerial.dll to "C:\Program Files\Java\jdk1.6.0_07\jre\bin" and copied RXTXcomm.jar to "C:\Program Files\Java\jdk1.6.0_07\jre\lib\ext" (my JAVA_HOME variable is set to C:\Program Files\Java\jdk1.6.0_07\jre) I also added RXTXcomm.jar to my eclipse project. But when I run it, it still says "NoSuchPortException" Devel Library ========================================= Native lib Version = RXTX-2.0-7pre1 Java lib Version = RXTX-2.0-7pre1 java.lang.ClassCastException: gnu.io.RXTXCommDriver cannot be cast to gnu.io.CommDriver thrown while loading gnu.io.RXTXCommDriver gnu.io.NoSuchPortException at gnu.io.CommPortIdentifier.getPortIdentifier(CommPortIdentifier.java:218) at TwoWaySerialComm.connect(TwoWaySerialComm.java:20) at TwoWaySerialComm.main(TwoWaySerialComm.java:107) In my java file, I tell it: try { (new TwoWaySerialComm()).connect("COM4"); } and I've also tried the Java Comm API. Both cannot recognize my serial port but I am sure I followed the instruction correctly. There files are there. Does anybody have any idea what it could be?

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  • Actor model to replace the threading model?

    - by prosseek
    I read a chapter in a book (Seven languages in Seven Weeks by Bruce A. Tate) about Matz (Inventor of Ruby) saying that 'I would remove the thread and add actors, or some other more advanced concurrency features'. Why and how an actor model can be an advanced concurrency model that replaces the threading? What other models are the 'advanced concurrency model'?

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  • How do I reference Django Model from another model

    - by user313943
    Im looking to create a view in the admin panel for a test program which logs Books, publishers and authors (as on djangoproject.com) I have the following two models defined. class Author(models.Model): first_name = models.CharField(max_length=30) last_name = models.CharField(max_length=30) email = models.EmailField() def __unicode__(self): return u'%s %s' % (self.first_name, self.last_name) class Book(models.Model): title = models.CharField(max_length=100) authors = models.ManyToManyField(Author) publisher = models.ForeignKey(Publisher) publication_date = models.DateField() def __unicode__(self): return self.title What I want to do, is change the Book model to reference the first_name of any authors and show this using admin.AdminModels. #Here is the admin model I've created. class BookAdmin(admin.ModelAdmin): list_display = ('title', 'publisher', 'publication_date') # Author would in here list_filter = ('publication_date',) date_hierarchy = 'publication_date' ordering = ('-publication_date',) fields = ('title', 'authors', 'publisher', 'publication_date') filter_horizontal = ('authors',) raw_id_fields = ('publisher',) As I understand it, you cannot have two ForeignKeys in the same model. Can anyone give me an example of how to do this? I've tried loads of different things and its been driving me mad all day. Im pretty new to Python/Django. Just to be clear - I'd simply like the Author(s) First/Last name to appear alongside the book title and publisher name. Thanks

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  • "Could not register destruction callback" warn message leads to memory leaks?

    - by Séb
    Hello all, I'm in the exact same situation as this old question: http://stackoverflow.com/questions/2077558/warn-could-not-register-destruction-callback In short: I see a warning saying that a destruction callback could not be registered for some beans. My question is: since the beans whose destruction callback cannot be registered are two persistance beans, could this be the source of a memory leak? I am experiencing a leak in my app. Although the session timeout is set (to 30 minutes), my profiler shows me more instances of the hibernate SessionImpl each time I run a thread dump. The number of instances of SessionImpl is exactly the number of times I tried to login between two thread dumps. Thanks for your help...

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  • bash - how to filter java exception info

    - by Michael Mao
    Hi all: We've got a multi-agent Java environment where different agent would most likely produce all sorts of exceptions thrown to stderr. Here is a sample taken from the huge exception log **java.security.AccessControlException: access denied (java.io.FilePermission ..\tournament\Driver\HotelRoomAnalyser.class read)** at java.security.AccessControlContext.checkPermission(Unknown Source) at java.security.AccessController.checkPermission(Unknown Source) at java.lang.SecurityManager.checkPermission(Unknown Source) at java.lang.SecurityManager.checkRead(Unknown Source) at java.io.File.length(Unknown Source) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClassData(EmarketSandbox.java:218) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClass(EmarketSandbox.java:199) at java.lang.ClassLoader.loadClass(Unknown Source) **java.security.AccessControlException: access denied (java.io.FilePermission ..\tournament\Driver\HotelRoomAnalyser.class read)** at java.security.AccessControlContext.checkPermission(Unknown Source) at java.security.AccessController.checkPermission(Unknown Source) at java.lang.SecurityManager.checkPermission(Unknown Source) at java.lang.SecurityManager.checkRead(Unknown Source) at java.io.File.length(Unknown Source) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClassData(EmarketSandbox.java:218) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClass(EmarketSandbox.java:199) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClassInternal(Unknown Source) at MySmarterAgent.hotelRoomBookings(MySmarterAgent.java:108) fortunately all top-tier exceptions are denoted by no leading spaces, as wrapped by ** above. My concern is to get all of the top-tier exception name (delimited by colon :), together with the first line below which contains something like at emarket.client.EmarketSandbox$SandboxFileLoader.loadClassData(EmarketSandbox.java:218) Basically, something with padded style, starts with "at" and ends with ".java:108" So this info can be forwarded to the owner of that error-prone agent and let him/her fix it. My code in ~/.bashrc is incompleted now : alias startmatch='java -jar "emarket.jar" ../tournament 100'; function geterrors() { startmatch 2>"$1"; a=0; while read line do if true; then a=$(($a+1)); echo $a; fi; done } What it does now is to redirect all stderr to a text file specified by the first argument passed in, and after that, parse that text file line by line, if certain conditions returns true, echo only that line. And I am stuck with what to do inside the loop. Any suggestion is much appreciates, any hint is welcomed.

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  • What is the difference between Java RMI and JMS?

    - by Sanoj
    When designing an distributed application in Java there seams to be a few technologies that address the same kind of problem. I have briefly read about Java Remote Method Invocation and Java Message Service, but it is hard to really see the difference. Java RMI seams to be more tightly coupled than JMS because JMS use asynchronous communication, but otherwise I don't see any big differences. What is the difference between them? Is one of them newer than the other one? Which one is more common/popular in enterprises? What advantages do they have over eachother? When is one preferred over the other? Do they differ much in how difficult they are to implement? I also think that Web Services and CORBA address the same problem.

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  • How to define one-to-many connection between a same model through another model

    - by Mekajiki
    I want to define one-to-many relationship as follows; User has one introducer User has many newcomers(who is introduced by the user) Use "Introduction" model instead of adding a column to users table. My table and model definition is as follows; DB Scheme: create_table "introductions", force: true do |t| t.integer "introducer_id" t.integer "newcomer_id" t.datetime "created_at" t.datetime "updated_at" User model: class User < ActiveRecord::Base has_many :introductions, foreign_key: :introducer_id has_many :newcomers, through: :introductions, source: :newcomer belongs_to :introduction, foreign_key: :newcomer_id belongs_to :introducer end Introduction model: class Introduction < ActiveRecord::Base belongs_to :introducer, class_name: 'User' belongs_to :newcomer, class_name: 'User' end This works fine: user1.newcomers.push user2 but, user2.introducer # => nil How can I define belongs_to relationship correctly?

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  • Is there a java library / package analogous to <stdio.h>?

    - by Roboprog
    I have been doing Java on and off for about 14 years, and almost nothing else the last 6 years or so. I really hate the java.io package -- its legion of subclasses and adapters. I do like exceptions, rather than having to always poll "errno" and the like, but I could surely live without declared exceptions. Is there anything that functions like the Unix/ANSI stdio.h routines in C? I know we will never be rid of java.io and its conventions until java itself is retired, as they have metastasized throughout the many frameworks that have accreted to java. That said, I would like something that works kind of like this (let's call it package javax.stdio): Have a main utility class, perhaps FileStar, that can read and write files (or pipes), either text or binary, either sequentially or random access, with constructors that mimic fopen() and popen(). This class should have a load of useful methods that do things like fread(), fwrite(), fgets(), fputs(), fseek(), and whatever else (fprintf()?). Methods that are incompatible with the open/construct mode simply throw up (just like some of the collections classes/methods do when restricted). Then, have a bunch of interfaces that suggest how you intend to use the stream once you have created it: Sequential, RandomAccess, ReadOnly, WriteOnly, Text, Binary, plus combinations of these that make sense. Perhaps even have methods to return the appropriate type-cast (interface), throwing up if you have asked for something incompatible. For extra flavor, skip the declared exceptions -- e.g. - javax.stdio.IOException extends RuntimeException. Is there an open source project like this floating around?

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  • MVC Rendered Partial, how to get partial/view model in main model post to controller

    - by user1475788
    I have a text file and when users upload the file, the controller action method parses that file using state machine and uses a generic list to store some values. I pass this back to the view in the form of an IEnumerable. Within my main view, based on this ienumerable list I render a partail view to iterate items and display labels and a textarea. Users could add their input in the text area. When the users hit the save button this ienumrable list from the partial view rendered is null. so please advice any solutions. here is my main view @model RunLog.Domain.Entities.RunLogEntry @{ ViewBag.Title = "Create"; Layout = "~/Views/Shared/_Layout.cshtml"; } @using (Html.BeginForm("Create", "RunLogEntry", FormMethod.Post, new { enctype = "multipart/form-data" })) { <div id="inputTestExceptions" style="display: none;"> <table class="grid" style="width: 450px; margin: 3px 3px 3px 3px;"> <thead> <tr> <th> Exception String </th> <th> Comment </th> </tr> </thead> <tbody> @if (Model.TestExceptions != null) { foreach (var p in Model.TestExceptions) { Html.RenderPartial("RunLogTestExceptionSummary", p); } } </tbody> </table> </div> } partial view as follows: @model RunLog.Domain.Entities.RunLogEntryTestExceptionDisplay <tr> <td> @Model.TestException@ </td> <td>@Html.TextAreaFor(Model.Comment, new { style = "width: 200px; height: 80px;" }) </td> </tr> Controller action [HttpPost] public ActionResult Create(RunLogEntry runLogEntry, String ServiceRequest, string Hour, string Minute, string AMPM, string submit, IEnumerable<HttpPostedFileBase> file, String AssayPerformanceIssues1, IEnumerable<RunLogEntryTestExceptionDisplay> models) { } The problem is test exceptions which contains exception string and comment is comming back null.

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  • Using a join model to relate a model to itself

    - by Gabe Hollombe
    I have two models: User MentoringRelationship MentoringRelationship is a join model that has a mentor_id column and a mentee_id column (both of these reference user_ids from the users table). How can I specify a relation called 'mentees' on the User class that will return all of the users mentored by this user, using the MentoringRelationships join table? What relations do we need to declare in the User model and in the MentoringRelationship model?

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  • Problem with relative file path

    - by Richard Knop
    So here is my program, which works ok: import java.io.FileReader; import java.io.BufferedReader; import java.io.IOException; import java.util.Scanner; import java.util.Locale; public class ScanSum { public static void main(String[] args) throws IOException { Scanner s = null; double sum = 0; try { s = new Scanner(new BufferedReader(new FileReader("D:/java-projects/HelloWorld/bin/usnumbers.txt"))); s.useLocale(Locale.US); while (s.hasNext()) { if (s.hasNextDouble()) { sum += s.nextDouble(); } else { s.next(); } } } finally { s.close(); } System.out.println(sum); } } As you can see, I am using absolute path to the file I am reading from: s = new Scanner(new BufferedReader(new FileReader("D:/java-projects/HelloWorld/bin/usnumbers.txt"))); The problem arises when I try to use the relative path: s = new Scanner(new BufferedReader(new FileReader("usnumbers.txt"))); I get an error: Exception in thread "main" java.lang.NullPointerException at ScanSum.main(ScanSum.java:24) The file usnumbers.txt is in the same directory as the ScanSum.class file: D:/java-projects/HelloWorld/bin/ScanSum.class D:/java-projects/HelloWorld/bin/usnumbers.txt How could I solve this?

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  • MVVM- View Model-View Model Communications

    - by user275561
    How do I go about having two view models communicate with one another using MVVM Light. I know how to use the messenger class and register etc.. Here is my Scenario A Settings View ---> a Settings View Model . . . A MainPage View ---> A MainPage ViewModel If something changes in the Settings View it will Message back to the Settings View Model. So then I want the Settings View Model to communicate to the MainPage View Model about what changed. THe MainPage ViewModel will then tell the View.

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  • Does a CPU assigns a value atomically to memory?

    - by Poni
    Hi! A quick question I've been wondering about for some time; Does the CPU assign values atomically, or, is it bit by bit (say for example a 32bit integer). If it's bit by bit, could another thread accessing this exact location get a "part" of the to-be-assigned value? Think of this: I have two threads and one shared "unsigned int" variable (call it "g_uiVal"). Both threads loop. On is printing "g_uiVal" with printf("%u\n", g_uiVal). The second just increase this number. Will the printing thread ever print something that is totally not or part of "g_uiVal"'s value? In code: unsigned int g_uiVal; void thread_writer() { g_uiVal++; } void thread_reader() { while(1) printf("%u\n", g_uiVal); }

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  • google calendar api (java) authentication error in dynamic web project

    - by HazProblem
    org.springframework.web.util.NestedServletException: Handler processing failed; nested exception is java.lang.NoClassDefFoundError: com/google/gdata/util/AuthenticationException org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:823) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644) org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560) javax.servlet.http.HttpServlet.service(HttpServlet.java:641) javax.servlet.http.HttpServlet.service(HttpServlet.java:722) org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88) org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) The class i have written works fine as a normal java application, but when i try to use the code in an dynamic web project i get this authentication failure. Where´s the difference?

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  • Java: Best approach to have a long list of variables needed all the time without consuming memory?

    - by evilReiko
    I wrote an abstract class to contain all rules of the application because I need them almost everywhere in my application. So most of what it contains is static final variables, something like this: public abstract class appRules { public static final boolean IS_DEV = true; public static final String CLOCK_SHORT_TIME_FORMAT = "something"; public static final String CLOCK_SHORT_DATE_FORMAT = "something else"; public static final String CLOCK_FULL_FORMAT = "other thing"; public static final int USERNAME_MIN = 5; public static final int USERNAME_MAX = 16; // etc. } The class is big and contains LOTS of such variables. My Question: Isn't setting static variables means these variables are floating in memory all the time? Do you suggest insteading of having an abstract class, I have a instantiable class with non-static variables (just public final), so I instantiate the class and use the variables only when I need them. Or is what am I doing is completely wrong approach and you suggest something else?

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  • class hierarchy design for small java project

    - by user523956
    I have written a java code which does following:- Main goal is to fetch emails from (inbox, spam) folders and store them in database. It fetches emails from gmail,gmx,web.de,yahoo and Hotmail. Following attributes are stored in mysql database. Slno, messagedigest, messageid, foldername, dateandtime, receiver, sender, subject, cc, size and emlfile. For gmail,gmy and web.de, I have used javamail API, because email form it can be fetched with IMAP. For yahoo and hotmail, I have used html parser and httpclient to fetch emails form spam folder and for inbox folder, I have used pop3 javamail API. I want to have proper class hierarchy which makes my code efficient and easily reusable. As of now I have designed class hierarchy as below: I am sure it can still be improved. So I would like to have different opinions on it. I have following classes and methods as of now. MainController:- Here I pass emailid, password and foldername from which emails have to be fetched. Abstract Class :-EmailProtocol Abstract Methods of it (All methods except executeParser contains method definition):- connectImap() // used by gmx,gmail and web.de email ids connectPop3() // used by hotmail and yahoo to fetch emails of inbox folder createMessageDigest // used by every email provider(gmx, gmail,web.de,yahoo,hotmail) establishDBConnection // used by every email emailAlreadyExists // used by every email which checks whether email already exists in db or not, if not then store it. storeemailproperties // used by every email to store emails properties to mysql database executeParser // nothing written in it. Overwridden and used by just hotmail and yahoo to fetch emails form spam folder. Imap extends EmailProtocol (nothing in it. But I have to have it to access methods of EmailProtocol. This is used to fetch emails from gmail,gmx and web.de) I know this is really a bad way but don't know how to do it other way. Hotmsil extends EmailProtocol Methods:- executeParser() :- This is used by just hotmail email id. fetchjunkemails() :- This is also very specific for only hotmail email id. Yahoo extends EmailProtocol Methods:- executeParser() storeEmailtotemptable() MoveEmailtoInbox() getFoldername() nullorEquals() All above methods are specific for yahoo email id. public DateTimeFormat(class) format() //this formats datetime of gmax,gmail and web.de emails. formatYahoodate //this formats datetime of yahoo email. formatHotmaildate // this formats datetime of hotmail email. public StringFormat ConvertStreamToString() // Accessed by every class except DateTimeFormat class. formatFromTo() // Accessed by every class except DateTimeFormat class. public Class CheckDatabaseExistance public static void checkForDatabaseTablesAvailability() (This method checks at the beginnning whether database and required tables exist in mysql or not. if not it creates them) Please see code of my MainController class so that You can have an idea about how I use different classes. public class MainController { public static void main(String[] args) throws Exception { ArrayList<String> web_de_folders = new ArrayList<String>(); web_de_folders.add("INBOX"); web_de_folders.add("Unbekannt"); web_de_folders.add("Spam"); web_de_folders.add("OUTBOX"); web_de_folders.add("SENT"); web_de_folders.add("DRAFTS"); web_de_folders.add("TRASH"); web_de_folders.add("Trash"); ArrayList<String> gmx_folders = new ArrayList<String>(); gmx_folders.add("INBOX"); gmx_folders.add("Archiv"); gmx_folders.add("Entwürfe"); gmx_folders.add("Gelöscht"); gmx_folders.add("Gesendet"); gmx_folders.add("Spamverdacht"); gmx_folders.add("Trash"); ArrayList<String> gmail_folders = new ArrayList<String>(); gmail_folders.add("Inbox"); gmail_folders.add("[Google Mail]/Spam"); gmail_folders.add("[Google Mail]/Trash"); gmail_folders.add("[Google Mail]/Sent Mail"); ArrayList<String> pop3_folders = new ArrayList<String>(); pop3_folders.add("INBOX"); CheckDatabaseExistance.checkForDatabaseTablesAvailability(); EmailProtocol imap = new Imap(); System.out.println("CHECKING FOR NEW EMAILS IN WEB.DE...(IMAP)"); System.out.println("*********************************************************************************"); imap.connectImap("[email protected]", "pwd", web_de_folders); System.out.println("\nCHECKING FOR NEW EMAILS IN GMX.DE...(IMAP)"); System.out.println("*********************************************************************************"); imap.connectImap("[email protected]", "pwd", gmx_folders); System.out.println("\nCHECKING FOR NEW EMAILS IN GMAIL...(IMAP)"); System.out.println("*********************************************************************************"); imap.connectImap("[email protected]", "pwd", gmail_folders); EmailProtocol yahoo = new Yahoo(); Yahoo y=new Yahoo(); System.out.println("\nEXECUTING YAHOO PARSER"); System.out.println("*********************************************************************************"); y.executeParser("http://de.mc1321.mail.yahoo.com/mc/welcome?ymv=0","[email protected]","pwd"); System.out.println("\nCHECKING FOR NEW EMAILS IN INBOX OF YAHOO (POP3)"); System.out.println("*********************************************************************************"); yahoo.connectPop3("[email protected]","pwd",pop3_folders); System.out.println("\nCHECKING FOR NEW EMAILS IN INBOX OF HOTMAIL (POP3)"); System.out.println("*********************************************************************************"); yahoo.connectPop3("[email protected]","pwd",pop3_folders); EmailProtocol hotmail = new Hotmail(); Hotmail h=new Hotmail(); System.out.println("\nEXECUTING HOTMAIL PARSER"); System.out.println("*********************************************************************************"); h.executeParser("https://login.live.com/ppsecure/post.srf","[email protected]","pwd"); } } I have kept DatetimeFormat and StringFormat class public so that I can access its public methods by just (DatetimeFormat.formatYahoodate for e.g. from different methods). This is the first time I have developed something in java. It serves its purpose but of course code is still not so efficient I think. I need your suggestions on this project.

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