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• How to combine two separate unrelated Git repositories into one with single history timeline

  - by Antony

  I have two unrelated (not sharing any ancestor check in) Git repositories, one is a super repository which consists a number of smaller projects (Lets call it repository A). Another one is just a makeshift local Git repository for a smaller project (lets call it repository B). Graphically, it would look like this A0-B0-C0-D0-E0-F0-G0-HEAD (repo A) A0-B0-C0-D0-E0-F0-G0-HEAD (remote/master bare repo pulled & pushed from repo A) A1-B1-C1-D1-E1-HEAD (repo B) Ideally, I would really like to merge repo B into repo A with a single history timeline. So it would appear that I originally started project in repo A. Graphically, this would be the ideal end result A0-A1-B1-B0-D1-C0-D0-E0-F0-G0-E1-H(from repo B)-HEAD (new repo A) A0-A1-B1-B0-D1-C0-D0-E0-F0-G0-E1-H(from repo B)-HEAD (remote/master bare repo pulled & pushed from repo A) I have been doing some reading with submodules and subtree (Pro Git is a pretty good book by the way), but both of them seem to cater solution towards maintaining two separate branch with sub module being able to pull changes from upstream and subtree being slightly less headache. Both solution require additional and specialized git commands to handle check ins and sync between master and sub tree/module branch. Both solution also result in multiple time-lines (with --squash you even get 3 timelines with subtree). The closest solution from SO seems to talk about "graft", but is that really it? The goal is to have a single unified repository where I can pull/push check-ins, so that there are no more repo B, just repo A in the end.

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• error catching exception while System.out.print

  - by user1702633

  I have 2 classes, one that implements a double lookup( int i); and one where I use that lookup(int i) in solving a question, or in this case printing the lookup values. This case is for an array. So I read the exception documentation or google/textbook and come with the following code: public double lookup(int i) throws Exception { if( i > numItems) throw new Exception("out of bounds"); return items[i]; } and take it over to my class and try to print my set, where set is a name of the object type I define in the class above. public void print() { for (int i = 0; i < set.size() - 1; i++) { System.out.print(set.lookup(i) + ","); } System.out.print(set.lookup(set.size())); } I'm using two print()'s to avoid the last "," in the print, but am getting an unhandled exception Exception (my exception's name was Exception) I think I have to catch my exception in my print() but cannot find the correct formatting online. Do I have to write catch exception Exception? because that gives me a syntax error saying invalid type on catch. Sources like http://docs.oracle.com/javase/tutorial/essential/exceptions/ are of little help to me, I'm can't seem to grasp what the text is telling me. I'm also having trouble finding sources with multiple examples where I can actually understand the coding in the examples. so could anybody give me a source/example for the above catch phrase and perhaps a decent source of examples for new Java programmers? my book is horrendous and I cannot seem to find an understandable example for the above catch phrase online.

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• Unit testing a 'legacy' WPF Application

  - by sc_ray

  The product I have been working on has been in development for the past six years. It started as a generic data entry portal into an insanely complex part WPF/part legacy application. The system has been developed for all these years without a single Unit test in its fold. Now, the point has been raised for a comprehensive unit testing framework. I have been recruited recently to work on this product and have been tasked to get the 'Testing' in order. Since the team that worked on the product for the last six years adopted 'Agile', the project lacks any documentation of the business rules or any design documents. I have been trying to write unit tests for some of the modules. But I am not sure what to Mock, how to setup my Test fixture and eventually what to Test for, since a casual glance of the methods does not reveal its intentions. Also, it has come to my attention that the code was not developed with a particular methodology in mind. Given the situation, I was wondering if the good people of Stackoverflow could provide me with some advise on how to salvage this situation. I have heard about the book 'Working with Legacy Code' that has something to say about this general situation but I was thinking about getting some pointers from individuals who have encountered similar situations within the technology stack(C#,VB,C++,.NET 3.5,WCF,SQL Server 2005).

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• I can't compile this code

  - by heshim

  #include <stdio.h> #define IN 1 /* inside a word */ #define OUT 0 /* outside a word */ /* count lines, words, and characters in input */ main() { int c, nl, nw, nc, state; state = OUT; nl = nw = nc = 0; while ((c = getchar()) != EOF) { ++nc; if (c == '\n') ++nl; if (c == ' ' || c == '\n' || c = '\t') state = OUT; else if (state == OUT) { state = IN; ++nw; } } printf("%d %d %d\n", nl, nw, nc); } I got K&R book but there are some codes that don't compile ! it gives me - 19 C:\Users\Nom\Desktop\Untitled1.c invalid lvalue in assignment edit: now it works, thanks guys, but now it does nothing ! the printf statement doesn't work. It opens the dos console, I type anything and it just return a new line. I'm using Dev-C++ 4.9.9.2 I put the printf statement inside the while loop and it works now. thanks

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• Threading in Android

  - by virsir

  I am currently developing Android app, it needs download content from internet. I use thread to do that and then call runOnUiThread method to update GUI. I placed a refresh menu on it, if user tried to refresh the content, the download thread will be created and started. The problem is that how can I control the thread order, I need to accept the latest request's response and abandon previous thread requests if there were some other requests still running because the request parameters may have been changed by user. Currently I was using a threadId to do this thing, when a thread finished, it will check its threadId, if it was the latest recored one, it then takes control and render the response. My question is that is there any other proper better solution for this? Do I need to stop threads when user exit the app? I remember that some book said that do not try stop thread manually and wait itself finish is a good practice, is that true? Should I stop them by calling "stop" or "interrupt" method? I read some documents around threading in Android and found the class HandlerThread, what is it? In what kind of situation I need to use it?

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• Selective replication with CouchDB

  - by FRotthowe

  I'm currently evaluating possible solutions to the follwing problem: A set of data entries must be synchonized between multiple clients, where each client may only view (or even know about the existence of) a subset of the data. Each client "owns" some of the elements, and the decision who else can read or modify those elements may only be made by the owner. To complicate this situation even more, each element (and each element revision) must have an unique identifier that is equal for all clients. While the latter sounds like a perfect task for CouchDB (and a document based data model would fit my needs perfectly), I'm not sure if the authentication/authorization subsystem of CouchDB can handle these requirements: While it should be possible to restict write access using validation functions, there doesn't seem to be a way to authorize read access. All solutions I've found for this problem propose to route all CouchDB requests through a proxy (or an application layer) that handles authorization. So, the question is: Is it possible to implement an authorization layer that filters requests to the database so that access is granted only to documents that the requesting client has read access to and still use the replication mechanism of CouchDB? Simplified, this would be some kind of "selective replication" where only some of the documents, and not the whole database is replicated. I would also be thankful for directions to some detailed information about how replication works. The CouchDB wiki and even the "Definite Guide" Book are not too specific about that.

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• uploading database file in assets not returning a record

  - by Alexander

  I have a problem with a database file not being read I have added the database file in assets called mydb but when i run my code it says its not being located. It is calling this toast Toast.makeText(this, "No contact found", Toast.LENGTH_LONG).show(); This is being called because no records are being returned. This is an example form Android Application Development book. public class DatabaseActivity extends Activity { /** Called when the activity is first created. */ TextView quest, response1, response2; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); TextView quest = (TextView) findViewById(R.id.quest); try { String destPath = "/data/data/" + getPackageName() + "/databases/MyDB"; File f = new File(destPath); if (!f.exists()) { CopyDB( getBaseContext().getAssets().open("mydb"), new FileOutputStream(destPath)); } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } DBAdapter db = new DBAdapter(this); //---get a contact--- db.open(); Cursor c = db.getContact(2); if (c.moveToFirst()) DisplayContact(c); else Toast.makeText(this, "No contact found", Toast.LENGTH_LONG).show(); db.close(); } public void CopyDB(InputStream inputStream, OutputStream outputStream) throws IOException { //---copy 1K bytes at a time--- byte[] buffer = new byte[1024]; int length; while ((length = inputStream.read(buffer)) > 0) { outputStream.write(buffer, 0, length); } inputStream.close(); outputStream.close(); } public void DisplayContact(Cursor c) { quest.setText(String.valueOf(c.getString(1))); //quest.setText(String.valueOf("this is a text string")); } }

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• A question about TBB/C++ code

  - by Jackie

  I am reading The thread building block book. I do not understand this piece of code: FibTask& a=*new(allocate_child()) FibTask(n-1,&x); FibTask& b=*new(allocate_child()) FibTask(n-2,&y); What do these directive mean? class object reference and new work together? Thanks for explanation. The following code is the defination of this class FibTask. class FibTask: public task { public: const long n; long* const sum; FibTask(long n_,long* sum_):n(n_),sum(sum_) {} task* execute() { if(n FibTask& a=*new(allocate_child()) FibTask(n-1,&x); FibTask& b=*new(allocate_child()) FibTask(n-2,&y); set_ref_count(3); spawn(b); spawn_and_wait_for_all(a); *sum=x+y; } return 0; } };

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• When asked "How do I make a website?" how do you answer?

  - by Luke CK

  A (non-technical) friend of mine has asked me how to make a website. I get this question all the time. After a few questions I found out that she has an idea that could turn into a commercial site. I described three options to her: a) Get a book/enroll in a class/follow some online tutorials and learn how to do it. She's pretty smart and her personality seems like a good match for this sort of thing so I'm sure she could learn but she doesn't have a lot of time spare. Maybe if she started with one of those WYSIWYG editors at first? I stressed that this would take a longer than a couple of weekends of playing around. b) Hire someone to build it. Ranges from ultra cheap to ultra expensive, crappy to good and everything in between. I didn't mention sites like Rentacoder because she hasn't worked on a project like this before and doesn't know what to ask for. At this stage she'd likely ask for a Youtube-MySpace-Google for a few hundred bucks because she doesn't yet understand just how much is involved. c) Find someone technical and partner up with them. I explained that this can either work really well or be a disaster because she'd have to give up some of her ownership of the idea. How do you respond in these situations?

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• using action helpers in Zend Framework 1.8

  - by Nasser

  Hi am starting off with Zend Framework and have a question about action helpers. My first application is a simple authentication system (following a tutorial from a book). The registration and authentication seems to work fine but the redirect doesn't. I have a customer controller that has this among others: class CustomerController extends Zend_Controller_Action { // some code here...... public function authenticateAction() { $request = $this->getRequest(); if (!$request->isPost()) { return $this->_helper->redirector('login'); } // Validate $form = $this->_forms['login']; if (!$form->isValid($request->getPost())) { return $this->render('login'); } if (false === $this->_authService->authenticate($form->getValues())) { $form->setDescription('Login failed, please try again.'); return $this->render('login'); } return $this->_helper->redirector('index'); } the authenticate url is http://localhost/customer/authenticate and this seems to work fine but it does not redirect. After authentication I get a blank page which looks like its taking me to the index and just sits there. I tried using '/index' instead but that did not help either. Do I need to do anything special to make the redirector helper work? I have a logout action which behaves the same.

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• File writing problem on Windows 7 Professional in c#

  - by Ummar

  I have an application in C# which I write some data to file. I am facing the problem on windows 7 professional that when I write data to C:\ProgramData, Access denied acception is thrown. If I login from an administrator account this issue vanishes, and if I login from some other account who have administrative previlages this issue comes up. This issue is only produces on windows 7 professional, it is working fine on all other flavors of windows 7 as well as windows vista. try { XmlTextWriter myXmlTextWriter = new XmlTextWriter("Configuration.xml", null); myXmlTextWriter.Formatting = Formatting.Indented; myXmlTextWriter.WriteStartDocument(true); myXmlTextWriter.WriteDocType("ApplicationConfigurations", null, null, null); ////myXmlTextWriter.WriteComment("This file represents another fragment of a book store inventory database"); myXmlTextWriter.WriteStartElement("Configuration"); myXmlTextWriter.WriteElementString("firstElement", pe.ToString()); myXmlTextWriter.WriteEndElement(); myXmlTextWriter.WriteEndDocument(); myXmlTextWriter.Flush(); myXmlTextWriter.Close(); }catch(Exception e) { //Exception is thrown in Win7 professional }

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• Is this a reasonable way to handle getters/setters in a PHP class?

  - by Mark Biek

  I'm going to try something with the format of this question and I'm very open to suggestions about a better way to handle it. I didn't want to just dump a bunch of code in the question so I've posted the code for the class on refactormycode. base-class-for-easy-class-property-handling My thought was that people can either post code snippets here or make changes on refactormycode and post links back to their refactorings. I'll make upvotes and accept an answer (assuming there's a clear "winner") based on that. At any rate, on to the class itself: I see a lot of debate about getter/setter class methods and is it better to just access simple property variables directly or should every class have explicit get/set methods defined, blah blah blah. I like the idea of having explicit methods in case you have to add more logic later. Then you don't have to modify any code that uses the class. However I hate having a million functions that look like this: public function getFirstName() { return $this->firstName; } public function setFirstName($firstName) { return $this->firstName; } Now I'm sure I'm not the first person to do this (I'm hoping that there's a better way of doing it that someone can suggest to me). Basically, the PropertyHandler class has a __call magic method. Any methods that come through __call that start with "get" or "set" are then routed to functions that set or retrieve values into an associative array. The key into the array is the name of the calling method after get or set. So, if the method coming into __call is "getFirstName", the array key is "FirstName". I liked using __call because it will automatically take care of the case where the subclass already has a "getFirstName" method defined. My impression (and I may be wrong) is that the __get & __set magic methods don't do that. So here's an example of how it would work: class PropTest extends PropertyHandler { public function __construct() { parent::__construct(); } } $props = new PropTest(); $props->setFirstName("Mark"); echo $props->getFirstName(); Notice that PropTest doesn't actually have "setFirstName" or "getFirstName" methods and neither does PropertyHandler. All that's doing is manipulating array values. The other case would be where your subclass is already extending something else. Since you can't have true multiple inheritance in PHP, you can make your subclass have a PropertyHandler instance as a private variable. You have to add one more function but then things behave in exactly the same way. class PropTest2 { private $props; public function __construct() { $this->props = new PropertyHandler(); } public function __call($method, $arguments) { return $this->props->__call($method, $arguments); } } $props2 = new PropTest2(); $props2->setFirstName('Mark'); echo $props2->getFirstName(); Notice how the subclass has a __call method that just passes everything along to the PropertyHandler __call method. Another good argument against handling getters and setters this way is that it makes it really hard to document. In fact, it's basically impossible to use any sort of document generation tool since the explicit methods to be don't documented don't exist. I've pretty much abandoned this approach for now. It was an interesting learning exercise but I think it sacrifices too much clarity.

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• Android app with library can't find the library.apk

  - by Dean Schulze

  I'm trying to get the FinchVideo example from the Programming Android book to work. It uses the FinchWelcome library. I've set up FinchWelcome as a Library and in the FinchVideo application I have checked the FinchWelcome library in Properties - Android. When I try to run FinchVideo in the emulator it complains that it cannot find FinchWelcome.apk (output below). I'm building for Android 4.0.3. While Googling for this problem I've found that a lot of people have this problem with Android apps that use libraries. No one seems to have found a solution that works consistently, though. None of the Android books I've seen even talk about how to download libraries. What is the proper way to handle libraries in Android applications? Is this a bug in the Eclipse ADT? Thanks. [FinchVideo] Installing FinchVideo.apk... [FinchVideo] Success! [FinchWelcome] Could not find FinchWelcome.apk! [FinchVideo] Starting activity com.oreilly.demo.pa.finchvideo.FinchVideoActivity on device emulator-5554

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• Should I learn two (or more) programming languages in parallel?

  - by c_maker

  I found entries on this site about learning a new programming language, however, I have not come across anything that talks about the advantages and disadvantages of learning two languages at the same time. Let's say my goal is to learn two new languages in a year. I understand that the definition of learning a new language is different for everyone and you can probably never know everything about a language. I believe in most cases the following things are enough to include the language in your resume and say that you are proficient in it (list is not in any particular order): Know its syntax so you can write a simple program in it Compare its underlying concepts with concepts of other languages Know best practices Know what libraries are available Know in what situations to use it Understand the flow of a more complex program At least know most of what you do not know I would probably look for a good book and pick an open source project for both of these languages to start with. My questions: Is it best to spend 5 months learning language#1 then 5 months learning language#2, or should you mix the two. Mixing them I mean you work on them in parallel. Should you pick two languages that are similar or different? Are there any advantages/disadvantages of let's say learning Lisp in tandem with Ruby? Is it a good idea to pick two languages with similar syntax or would it be too confusing? Please tell me what your experiences are regarding this. Does it make a difference if you are a beginner or a senior programmer?

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• How do I access a value of a nested Perl hash?

  - by st

  I am new to Perl and I have a problem that's very simple but I cannot find the answer when consulting my Perl book. When printing the result of Dumper($request); I get the following result: $VAR1 = bless( { '_protocol' => 'HTTP/1.1', '_content' => '', '_uri' => bless( do{\(my $o = 'http://myawesomeserver.org:8081/counter/')}, 'URI::http' ), '_headers' => bless( { 'user-agent' => 'Mozilla/5.0 (X11; U; Linux i686; en; rv:1.9.0.4) Gecko/20080528 Epiphany/2.22 Firefox/3.0', 'connection' => 'keep-alive', 'cache-control' => 'max-age=0', 'keep-alive' => '300', 'accept' => 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8', 'accept-language' => 'en-us,en;q=0.5', 'accept-encoding' => 'gzip,deflate', 'host' => 'localhost:8081', 'accept-charset' => 'ISO-8859-1,utf-8;q=0.7,*;q=0.7' }, 'HTTP::Headers' ), '_method' => 'GET', '_handle' => bless( \*Symbol::GEN0, 'FileHandle' ) }, 'HTTP::Server::Simple::Dispatched::Request' ); How can I access the values of '_method' ('GET') or of 'host' ('localhost:8081'). I know that's an easy question, but Perl is somewhat cryptic at the beginning.

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• PNG's In Mac on Java cause massive CPU usage

  - by alexganose

  Hey, I've been having this problem for a while now and I was hoping someone could help. I make small games using Java on Mac OSX 1.6.3 and if I use PNG's as the image format my CPU usage by Java skyrockets to say 50% (on a very small 2D game). However if I use GIF as the format my CPU usage by Java stays constant at 10% which is reasonable. What is causing this problem?? It occurs on every game I develop using PNG's so I always just switch to GIF's. The problem is now that i need to use a PNG for its variable alpha properties rather than just plain transparency. This is not available using GIF's. The problem is present on Java SE 6 and previous versions. I am using an early 2009 Mac Book Pro 15". The problem does not occur on a Windows PC running the same game. The CPU usage due to Java using PNG's on a Windows PC (I have tried XP, Vista and 7) is always constantly low at ~10%. Any help would be greatly appreciated. Thanks :)

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• How to tell if leaving iOS app entered foreground from fast-app switching or manually?

  - by JPK

  Is there a way to tell if an iOS app enters the foreground from fast-app switching or manually? I need to know by the time applicationWillEnterForeground is called, so some specific code can be executed (or not executed) depending on the condition in which the app entered the foreground. EDIT: It turned out that this was more of a design issue for me. I moved my code to applicationDidBecomeActive. I also added a BOOL property to the appDelegate called fastAppSwitching (probably the wrong name for it). I set this to YES in application:handleOpenURL and application:openURL:sourceApplication:annotation. Then I added the following code to application:didFinishLaunchingWithOptions: if (launchOptions) { self.fastAppSwitching = YES; } else { self.fastAppSwitching = NO; } In applicationDidBecomeActive, I used the following code: if (fastAppSwitching == YES) { self.fastAppSwitching = NO; //stop, don't go any further } else { ... } EDIT2: MaxGabriel makes a good point below: "Just a warning to others taking the solution described here, applicationDidBecomeActive: is called when the user e.g. ignores a phone call or text message, unlike applicationWillEnterForeground". This is actually also true for in-app purchases and Facebook in-app authorization (new in iOS 6). So, with some further testing, this is the current solution: Add a new Bool called passedThroughWillEnterForeground. In applicationWillResignActive: self.passedThroughWillEnterForeground = NO; In applicationDidEnterBackground: self.passedThroughWillEnterForeground = NO; In applicationWillEnterForeground: self.passedThroughWillEnterForeground = YES; In applicationDidBecomeActive: if (passedThroughWillEnterForeground) { //we are NOT returning from 6.0 (in-app) authorization dialog or in-app purchase dialog, etc //do nothing with this BOOL - just reset it self.passedThroughWillEnterForeground = NO; } else { //we ARE returning from 6.0 (in-app) authorization dialog or in-app purchase dialog - IE //This is the same as fast-app switching in our book, so let's keep it simple and use this to set that self.fastAppSwitching = YES; } if (fastAppSwitching == YES) { self.fastAppSwitching = NO; } else { ... } EDIT3: I think we also need a bool to tell if app was launched from terminated.

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• Saving and restoring OpenGL model-view

  - by Tom

  I am a new-comer to OpenGL, and much of it remains mysterious to my feeble brain. I have been studying the NeHe demos as well as the Red Book. I am writing an Android application that displays the Earth in the center of the screen. The user can rotate the Earth about any axis (much like a very simple "Google Earth"). This code is working (I based it on the NeHe examples). Now I want to add a feature; the user should be able to save the current model orientation, then later return to that same orientation. For example, the user may save the Earth orientation such that the viewer is looking down at her hometown, and north-east is "up". How do I do this with OpenGL-ES? To capture and save the current orientation, my code could get the current model-view transformation matrix - I think I understand how to do that. But later on how do I apply that saved matrix to restore the view?

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• Need help/guidance about creating a desktop application with gui

  - by Somebody still uses you MS-DOS

  I'm planning to do an Desktop application using Python, to learn some Desktop concepts. I'm going to use GTK or Qt, I still haven't decided which one. Fact is: I would like to create an application with the possibility to be called from command line, AND using a GUI. So it would be useful for cmd fans, and GUI users as well. It would be interesting to create a web interface too in the future, so it could be run in a server somewhere using an html interface created with a template language. I'm thinking about two approaches: - Creating a "model" with a simple interface which is called from a desktop/web implementation; - Creating a "model" with an html interface, and embeb a browser component so I could reuse all the code in both desktop/web scenarios. My question is: which exactly concepts are involved in this project? What advantages/disadvantages each approach has? Are they possible? By naming "interface", I'm planning to just do some interfaces.py files with def calls. Is this a bad approach? I would like to know some book recommendations, or resources to both options - or source code from projects which share the same GUI/cmd/web goals I'm after. Thanks in advance!

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• Problem with Java FX Look and Feel

  - by drachenfels

  Hi, I was looking at some of the examples from the Deitel and Deitel's book for Programming in Java, and one of the first examples is a very simple Swing display. Hence this snippet of code : import javax.swing.*; public class cdea { public static void main(String args[]){ JOptionPane.showMessageDialog(null,"\"Welcome to Java Programming!\""); System.exit(0); //end method main } } I read some stuff regarding how one can get native UI look and feel by using UIManager.setLookAndFeel( UIManager.getSystemLookAndFeelClassName()); to the program. However, when I just add this to my main method, it gives me a host of errors. Specifically : Multiple markers at this line - Unhandled exception type IllegalAccessException - Unhandled exception type InstantiationException - Unhandled exception type ClassNotFoundException - Unhandled exception type UnsupportedLookAndFeelException However when I use it as part of a try/catch exception loop (is that what it is called?) as detailed on http://stackoverflow.com/questions/1590863/getting-java-applications-to-look-native-on-windows-how , I get the program running properly. Could anyone tell me in simple language why this is so? As in, why can't I directly get the System look and feel; why do I have to use it with exception handling? I'm new to Java, and OOP in general, so I'm sorry if I'm being too simplistic.

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• How can I exclude LEFT JOINed tables from TOP in SQL Server?

  - by Kalessin

  Let's say I have two tables of books and two tables of their corresponding editions. I have a query as follows: SELECT TOP 10 * FROM (SELECT hbID, hbTitle, hbPublisherID, hbPublishDate, hbedID, hbedDate FROM hardback LEFT JOIN hardbackEdition on hbID = hbedID UNION SELECT pbID, pbTitle, pbPublisher, pbPublishDate, pbedID, pbedDate FROM paperback Left JOIN paperbackEdition on pbID = pbedID ) books WHERE hbPublisherID = 7 ORDER BY hbPublishDate DESC If there are 5 editions of the first two hardback and/or paperback books, this query only returns two books. However, I want the TOP 10 to apply only to the number of actual book records returned. Is there a way I can select 10 actual books, and still get all of their associated edition records? In case it's relevant, I do not have database permissions to CREATE and DROP temporary tables. Thanks for reading! Update To clarify: The paperback table has an associated table of paperback editions. The hardback table has an associated table of hardback editions. The hardback and paperback tables are not related to each other except to the user who will (hopefully!) see them displayed together.

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• Meaning of NEXT in Linked List creation in perl

  - by seleniumnewbie

  So I am trying to learn Linked Lists using Perl. I am reading "Mastering Algorithms with Perl" by Job Orwant. In the book he explains how to create a linked list I understand most of it, but I just simply fail to understand the command/index/key NEXT in the second last line of the code snippet. $list=undef; $tail=\$list; foreach (1..5){ my $node = [undef, $_ * $_]; $$tail = $node; $tail = \${$node->[NEXT]}; # The NEXT on this line? } What is he trying to do there? Isn $node a scalar, which stores the address of the unnamed array. Also even if we are de-referencing $node, should we not refer to the individual elements by an index number example (0,1). If we do use "NEXT" as a key, is $node a reference to a hash? I am very confused. Something in plain English will be highly appreciated.

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• Serializing a class containing a custom class

  - by Netfangled

  I want to serialize an object as xml that contains other custom classes. From what I understand (I've been reading MSDN and SO mostly), the XmlSerializer doesn't take this into account. This is the line that's confusing me: XML serialization serializes only the public fields and property values of an object into an XML stream. XML serialization does not include type information. For example, if you have a Book object that exists in the Library namespace, there is no guarantee that it will be deserialized into an object of the same type. Taken from MSDN, here For example, I want to serialize an object of type Order, but it contains a list of Products, and each one contains an object of type Category: class Order { List<Product> products; } class Product { Category type; } class Category { string name; string description; } And I want my Order object to be serialized like so: <Order> <Product> <Category Name=""> <Description></Description> </Category> </Product> <Product> <Category Name=""> <Description></Description> </Category> </Product> <Order> Does the XmlSerializer already do this? If not, is there another class that does or do I have to define the serialization process myself?

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• checking is username exists on two tables PHP PDO?

  - by PHPLOVER

  Me again. I have a users table and a users_banlist table. On my registration form i want to check all in one query whether the username someone entered on form exists in the users table and see if it also exists on the users_banlist table. I can do them on there own in individual queries but would rather do it all in one. Here is what i got, but even thou i enter a username that is taken it does not tell me its already taken. $stmt = $dbh->prepare(" SELECT users.user_login, users_banlist.user_banlist FROM users , users_banlist WHERE users.user_login = ? OR users_banlist.user_banlist = ?"); // checker if username exists in users table or users_banlist table $stmt->execute(array($username, $username)); if ( $stmt->rowCount() > 0 ) { $error[] = 'Username already taken'; } Basically i think it is something to do with the execute or rowCount(), could anyone tell me where i am going wrong ? being new to pdo im finding it a little confusing at the moment until i get my pdo book delivered to learn pdo. Thank you as always, phplover

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• IS operator behaving a bit strangely

  - by flockofcode

  1) According to my book, IS operator can check whether expression E (E is type) can be converted to the target type only if E is either a reference conversion, boxing or unboxing. Since in the following example IS doesn’t check for either of the three types of conversion, the code shouldn’t work, but it does: int i=100; if (i is long) //returns true, indicating that conversion is possible l = i; 2) a) B b; A a = new A(); if (a is B) b = (B)a; int i = b.l; class A { public int l = 100; } class B:A { } The above code always causes compile time error “Use of unassigned variable”. If condition a is B evaluates to false, then b won’t be assigned a value, but if condition is true, then it will. And thus by allowing such a code compiler would have no way of knowing whether the usage of b in code following the if statement is valid or not ( due to not knowing whether a is b evaluates to true or false) , but why should it know that? Intsead why couldn’t runtime handle this? b) But if instead we’re dealing with non reference types, then compiler doesn’t complain, even though the code is identical.Why? int i = 100; long l; if (i is long) l = i; thank you

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