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• Which book should I choose?

  - by sebastianlarsson

  Hi guys, I'm looking for a good read on object oriented design. The two books I'm currently looking Head First Design Patterns and Head First Object object-oriented analysis & design. They seem very similar when looking at the contents and browsing through available sample text. Which one would be the best choice? About myself: I have a bachelor in computer science and I am currently studying Msc. Software Quality Engineering (read Software Engineering with focus on Quality). I am already confident in object-oriented design and have a lot of programming courses in my backpack. I have done games in c++, courses in advanced java programming (I am SCJP certified), but my preferred language is C#. I have also worked with Java for the last 7 months while studying. I am currently also studying for certificates in C# (apart from my usual studies). So I believe I have the prerequisites of actually understanding the contents of both books. Reason: I just want to be better and keep evolving as a programmer. I think it is fun. I believe Bert Bates and Kathy Sierra are involved in both these books and I have previously read their SCJP preparation book in java. I really do enjoy their style of writing. Other books which I am considering are: Clean Code: A Handbook Of Agile Software Craftsmanship Thx in advance Sebastian

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• How do I lookup a JNDI Datasource from outside a web container?

  - by masotime

  I have the following environment set up: Java 1.5 Sun Application Server 8.2 Oracle 10 XE Struts 2 Hibernate I'm interested to know how I can write code for a Java client (i.e. outside of a web application) that can reference the JNDI datasource provided by the application server. The ports for the Sun Application Server are all at their defaults. There is a JNDI datasource named jdbc/xxxx in the server configuration, but I noticed that the Hibernate configuration for the web application uses the name java:comp/env/jdbc/xxxx instead. Most of the examples I've seen so far involve code like Context ctx = new InitialContext(); ctx.lookup("jdbc/xxxx"); But it seems I'm either using the wrong JNDI name, or I need to configure a jndi.properties or other configuration file to correctly point to a listener? I have appserv-rt.jar from the Sun Application Server which has a jndi.properties inside of it, but it does not seem to help. There's a similar question here, but it doesn't give any code / refers to having iBatis obtain the JNDI Datasource automatically: http://stackoverflow.com/questions/39053/accessing-datasource-from-outside-a-web-container-through-jndi

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• What software development process do you use and how do you implement it?

  - by clyfe

  Post only what you do use not what you would like to use, so we can see what is the most popular in real life. I am interested only in theese issues: Project Model (waterfall, agile...) How are requirements gathered (and stored)? Revision control - what software, what workflow Build automation, what software, where does it fit ? How is the testing done ? How is the documentation done ? How is the quality assurance done ? Please provide short objective answers, don't speak from the books. EXAMPLE: In my company we are a small team of 5 people and we develop webapps using ruby. agile PM cucumber requirements git SCM - Integration Manager Workflow integrity CI rspec automated tests the project lead creats the documentation skeleton then it is filled by the developers ensure quality by peer reviewing code and manual peer-testing

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• Is it possible to inject a bean into a spring form bean

  - by Mike

  I tried to do it 2 different ways, but neither way worked. @Component public class EmailForm{ ... private QuestionDAO questionDAO; ... @Autowired public void setQuestionDAO(QuestionDAO questionDAO) { this.questionDAO = questionDAO; } ... Another way: @Component public class EmailForm implements ApplicationContextAware { ... public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { this.questionDAO = (QuestionDAO)applicationContext.getBean("questionDAO"); } ... Neither way results in questionDAO being injected Form bean is populated by spring: @RequestMapping(method = RequestMethod.POST) public String submit(@Valid final EmailForm emailForm, BindingResult result, final Model model) {

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• Ruby and duck typing: design by contract impossible?

  - by davetron5000

  Method signature in Java: public List<String> getFilesIn(List<File> directories) similar one in ruby def get_files_in(directories) In the case of Java, the type system gives me information about what the method expects and delivers. In Ruby's case, I have no clue what I'm supposed to pass in, or what I'll expect to receive. In Java, the object must formally implement the interface. In Ruby, the object being passed in must respond to whatever methods are called in the method defined here. This seems highly problematic: Even with 100% accurate, up-to-date documentation, the Ruby code has to essentially expose its implementation, breaking encapsulation. "OO purity" aside, this would seem to be a maintenance nightmare. The Ruby code gives me no clue what's being returned; I would have to essentially experiment, or read the code to find out what methods the returned object would respond to. Not looking to debate static typing vs duck typing, but looking to understand how you maintain a production system where you have almost no ability to design by contract. Update No one has really addressed the exposure of a method's internal implementation via documentation that this approach requires. Since there are no interfaces, if I'm not expecting a particular type, don't I have to itemize every method I might call so that the caller knows what can be passed in? Or is this just an edge case that doesn't really come up?

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• IPC speed and compare

  - by Lily

  I am trying to implement a real-time application which involves IPC across different modules. The modules are doing some data intensive processing. I am using message queue as the backbone(Activemq) for IPC in the prototype, which is easy(considering I am a totally IPC newbie), but it's very very slow. Here is my situation: I have isolated the IPC part so that I could change it other ways in future. I have 3 weeks to implement another faster version. ;-( IPC should be fast, but also comparatively easy to pick up I have been looking into different IPC approaches: socket, pipe, shared memory. However, I have no experience in IPC, and there is definitely no way I could fail this demo in 3 weeks... Which IPC will be the safe way to start with? Thanks. Lily

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• Is there a recommended way to use the Observer pattern in MVP using GWT?

  - by Tomislav Nakic-Alfirevic

  I am thinking about implementing a user interface according to the MVP pattern using GWT, but have doubts about how to proceed. These are (some of) my goals: - the presenter knows nothing about the UI technology (i.e. uses nothing from com.google.*) - the view knows nothing about the model or the presenter - the model knows nothing of the view or the presenter (...obviously) I would place an interface between the view and the presenter and use the Observer pattern to decouple the two: the view generates events and the presenter gets notified. What confuses me is that java.util.Observer and java.util.Observable are not supported in GWT. This suggests that what I'm doing is not the recommended way to do it, as far as GWT is concerned, which leads me to my questions: what is the recommended way to implement MVP using GWT, specifically with the above goals in mind? How would you do it?

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• Release objects before returning a value based on those object?

  - by Moshe

  Consider the following method, where I build a string and return it. I would like to release the building blocks of the sting, but then the string is based on values that no longer exists. Now what? Am I leaking memory and if so, how can I correct it? - (NSString) getMiddahInEnglish:(int)day{ NSArray *middah = [[NSArray alloc] initWithObjects:@"Chesed", @"Gevurah", @"Tiferes", @"Netzach", @"Hod", @"Yesod", @"Malchus"]; NSString *firstPartOfMiddah = [NSString stringWithFormat: @"%@", [middah objectAtIndex: ((int)day% 7)-1]]; NSString *secondPartOfMiddah = [NSString stringWithFormat: @"%@", [middah objectAtIndex: ((int)day / 7)]]; NSString *middahStr = [NSString string@"%@ She'bi@%", firstPartOfMiddah, secondPartOfMiddah]; [middah release]; [firstPartOfMiddah release]; [secondPartOfMiddah release]; return middahStr; }

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• Total Order between !different! volatile variables?

  - by andreas

  Hi all, Consider the following Java code: volatile boolean v1 = false; volatile boolean v2 = false; //Thread A v1 = true; if (v2) System.out.println("v2 was true"); //Thread B v2 = true; if (v1) System.out.println("v1 was true"); If there was a globally visible total order for volatile accesses then at least one println would always be reached. Is that actually guaranteed by the Java Standard? Or is an execution like this possible: A: v1 = true; B: v2 = true; A: read v2 = false; B: read v1 = false; A: v2 = true becomes visible (after the if) B: v1 = true becomes visible (after the if) I could only find statements about accesses to the same volatile variable in the Standard (but I might be missing something). "A write to a volatile variable (§8.3.1.4) v synchronizes-with all subsequent reads of v by any thread (where subsequent is defined according to the synchronization order)." http://java.sun.com/docs/books/jls/third_edition/html/memory.html#17.4.4 Thanks!

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• Packaging reference documentation with jar file

  - by soren.enemaerke

  We are porting our .NET library to a java equivalent and is now looking at how to distribute this port. Packaging the classes into a jar-file seems like best practice and we would then ship this jar file in a zip along with some license terms. But what about the documentation? In .NET land it seems like best practice to distribute the xml file that can be consumed by tooling (Visual Studio) but we can't seem to find such best practices for java. We have javadoc comments on our public classes and interfaces, so we are just looking for a way to generate and distribute these comments in a way that is developer friendly (we're thinking easily consumed from various IDEs). What are developers expecting and how do you best deliver this? We would really prefer to bundle the documentation along with the jar file and not have to host the documentation on our website EDIT: We would like for our documentation to appear inside the java IDEs so we want to provide the documentation in a way that integrates into the IDEs as gracefully as possible. In .NET land this is as an xml file placed next to the .dll file, but is there a similar concept for jar files that enables the integration into tooling? PS: We are developing in Eclipse and have an ant task doing the building and jar-file packaing in our automated build.

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• Set fields with instrospection - Problem with String.valueOf(String)

  - by fabb

  Hey there! I'm setting public fields of the Object 'this' via reflection. Both the field name and the value are given as String. I use several various field types: Boolean, Integer, Float, Double, an own enum, and a String. It works with all of them except with a String. The exception that gets thrown is that no method with the Signature String.valueOf(String) exists... Now I use a dirty instanceof workaround to detect if each field is a String and in that case just copy the value to the field. private void setField(String field, String value) throws Exception { Field wField = this.getClass().getField(field); if(wField.get(this) instanceof String){ //TODO dirrrrty hack //stupid workaround as java.lang.String.valueOf(java.lang.String) fails... wField.set(this, value); }else{ Method parseMethod = wField.getType().getMethod("valueOf", new Class[]{String.class}); wField.set(this, parseMethod.invoke(wField, value)); } } Any ideas how to avoid that workaround? Do you think java.lang.String should support the method valueOf(String)? thanks, fabb

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• Improving field get and set performance with ASM or Javassist

  - by ng

  I would like to avoid reflection in an open source project I am developing. Here I have classes like the following. public class PurchaseOrder { @Property private Customer customer; @Property private String name; } I scan for the @Property annotation to determine what I can set and get from the PurchaseOrder reflectively. There are many such classes all using java.lang.reflect.Field.get() and java.lang.reflect.Field.set(). Ideally I would like to generate for each property an invoker like the following. public interface PropertyAccessor<S, V> { public void set(S source, V value); public V get(S source); } Now when I scan the class I can create a static inner class of PurchaseOrder like so. static class customer_Field implements PropertyAccessor<PurchaseOrder, Customer> { public void set(PurchaseOrder order, Customer customer) { order.customer = customer; } public Customer get(PurchaseOrder order) { return order.customer; } } With these I totally avoid the cost of reflection. I can now set and get from my instances with native performance. Can anyone tell me how I would do this. A code example would be great. I have searched the net for a good example but can find nothing like this. The ASM and Javasist examples are pretty poor also. The key here is that I have an interface that I can pass around. So I can have various implementations, perhaps one with Java Reflection as a default, one with ASM, and one with Javassist? Any help would be greatly appreciated.

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• return an ArrayList method

  - by Bopeng Liu

  This is a drive method for two other classes. which i posted here http://codereview.stackexchange.com/questions/33148/book-program-with-arraylist I need some help for the private static ArrayList getAuthors(String authors) method. I am kind a beginner. so please help me finish this drive method. or give me some directions. Instruction some of the elements of the allAuthors array contain asterisks “*” between two authors names. The getAuthors method uses this asterisk as a delimiter between names to store them separately in the returned ArrayList of Strings. import java.util.ArrayList; public class LibraryDrive { public static void main(String[] args) { String[] titles = { "The Hobbit", "Acer Dumpling", "A Christmas Carol", "Marley and Me", "Building Java Programs", "Java, How to Program" }; String[] allAuthors = { "Tolkien, J.R.", "Doofus, Robert", "Dickens, Charles", "Remember, SomeoneIdont", "Reges, Stuart*Stepp, Marty", "Deitel, Paul*Deitel, Harvery" }; ArrayList<String> authors = new ArrayList<String>(); ArrayList<Book> books = new ArrayList<Book>(); for (int i = 0; i < titles.length; i++) { authors = getAuthors(allAuthors[i]); Book b = new Book(titles[i], authors); books.add(b); authors.remove(0); } Library lib = new Library(books); System.out.println(lib); lib.sort(); System.out.println(lib); } private static ArrayList<String> getAuthors(String authors) { ArrayList books = new ArrayList<String>(); // need help here. return books; } }

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• Why does Jcreator show iIlegal start of expression?

  - by Inusual Whisper Sinclair

  I am new at programming and currently in our classes we are learning java. I am trying to create a routine in which I need to use String variables only. Below it is the code in which I am working with: public static void main(String[] args) throws java.io.IOException { BufferedReader in = new BufferedReader(new InputStreamReader(System. in )); PrintStream out = System.out; String hair.equals("damagedHair"); cutHair(marvin); cleanHair(michelle); for (int i = 0; i < 2; i++) { static void cutHair(String marvin) { String cabello; marvin.equals(hair); if (marvin.equals("damagedHair")) { cabello.equals("newHaircut"); result(hair); } static void cleanHair(String michelle) { String hair; michelle.equals(hair); if (michelle.equals(newHaircut)) { hair.equals("putShampooAndConditioner"); result(hair); } static void result(String pHair) {; PrintStream out = System.out; out.println("============="); out.println(pHair); out.println("============="); } } Jcreator is giving me an error that says Illegal start of expression and also java 50 error ';' expected. I am not sure why is this coming up and I am a little confused as to whether I am doing something I am not supposed to and how to correct it. Sorry about the double posting, this is the right message. Need some help from you guys to figure this out. Thanks in advanced!

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• Best Practice With JFrame Constructors?

  - by David Barry

  In both my Java classes, and the books we used in them laying out a GUI with code heavily involved the constructor of the JFrame. The standard technique in the books seems to be to initialize all components and add them to the JFrame in the constructor, and add anonymous event handlers to handle events where needed, and this is what has been advocated in my class. This seems to be pretty easy to understand, and easy to work with when creating a very simple GUI, but seems to quickly get ugly and cumbersome when making anything other than a very simple gui. Here is a small code sample of what I'm describing: public class FooFrame extends JFrame { JLabel inputLabel; JTextField inputField; JButton fooBtn; JPanel fooPanel; public FooFrame() { super("Foo"); fooPanel = new JPanel(); fooPanel.setLayout(new FlowLayout()); inputLabel = new JLabel("Input stuff"); fooPanel.add(inputLabel); inputField = new JTextField(20); fooPanel.add(inputField); fooBtn = new JButton("Do Foo"); fooBtn.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { //handle event } }); fooPanel.add(fooBtn); add(fooPanel, BorderLayout.CENTER); } } Is this type of use of the constructor the best way to code a Swing application in java? If so, what techniques can I use to make sure this type of constructor is organized and maintainable? If not, what is the recommended way to approach putting together a JFrame in java?

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• J2ME Reduce Image color-depth/ Compress Image size

  - by updateraj

  Hi, I need to transmit the image from the mobile phone to the server. I am able to reduce the image screen size but not the memory size. I understand i have to deal with the color depth. J2ME does not seem to offer any scaling method which is available in J2SE: image rescaled = image.getScaledInstance(thumbWidth, thumbHeight, Image.SCALE_AREA_AVERAGING); BufferedImage biRescaled = toBufferedImage(rescaled, thumbWidth, thumbHeight, BufferedImage.TYPE_INT_RGB); How i would i tackle this ? I would like to reduce the image memory size before i transmit to the server. Thank you

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• A very basic auto-expanding list/array

  - by MainMa

  Hi, I have a method which returns an array of fixed type objects (let's say MyObject). The method creates a new empty Stack<MyObject>. Then, it does some work and pushes some number of MyObjects to the end of the Stack. Finally, it returns the Stack.ToArray(). It does not change already added items or their properties, nor remove them. The number of elements to add will cost performance. There is no need to sort/order the elements. Is Stack a best thing to use? Or must I switch to Collection or List to ensure better performance and/or lower memory cost?

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• Releasing NSData causes exception...

  - by badmanj

  Hi, Can someone please explain why the following code causes my app to bomb? NSData *myImage = UIImagePNGRepresentation(imageView.image); : [myImage release]; If I comment out the 'release' line, the app runs... but a few times calling the function containing this code and I get a crash - I guess caused by a memory leak. Even if I comment EVERYTHING else in the function out and just leave those two lines, when the release executes, the app crashes. I'm sure this must be a newbie "you don't know how to clean up your mess properly" kind of thing ;-) Cheers, Jamie.

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• NullPointerException with static variables

  - by tomekK

  I just hit very strange (to me) behaviour of java. I have following classes: public abstract class Unit { public static final Unit KM = KMUnit.INSTANCE; public static final Unit METERS = MeterUnit.INSTANCE; protected Unit() { } public abstract double getValueInUnit(double value, Unit unit); protected abstract double getValueInMeters(double value); } And: public class KMUnit extends Unit { public static final Unit INSTANCE = new KMUnit(); private KMUnit() { } //here are abstract methods overriden } public class MeterUnit extends Unit { public static final Unit INSTANCE = new MeterUnit(); private MeterUnit() { } ///abstract methods overriden } And my test case: public class TestMetricUnits extends TestCase { @Test public void testConversion() { System.out.println("Unit.METERS: " + Unit.METERS); System.out.println("Unit.KM: " + Unit.KM); double meters = Unit.KM.getValueInUnit(102.11, Unit.METERS); assertEquals(0.10211, meters, 0.00001); } } 1) MKUnit and MeterUnit are both singletons initialized statically, so during class loading. Constructors are private, so they can't be initialized anywhere else. 2) Unit class contains static final references to MKUnit.INSTANCE and MeterUnit.INSTANCE I would expect that: KMUnit class is loaded and instance is created. MeterUnit class is loaded and instance is created. Unit class is loaded and both KM and METERS variable are initialized, they are final so they cant be changed. But when I run my test case in console with maven my result is: T E S T S Running de.audi.echargingstations.tests.TestMetricUnits Unit.METERS: m Unit.KM: null Tests run: 3, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.089 sec <<< FAILURE! - in de.audi.echargingstations.tests.TestMetricUnits testConversion(de.audi.echargingstations.tests.TestMetricUnits) Time elapsed: 0.011 sec <<< ERROR! java.lang.NullPointerException: null at de.audi.echargingstations.tests.TestMetricUnits.testConversion(TestMetricUnits.java:29) Results : Tests in error: TestMetricUnits.testConversion:29 NullPointer And the funny part is that, when I run this test from eclipse via JUnit runner everything is fine, I have no NullPointerException and in console I have: Unit.METERS: m Unit.KM: km So the question is: what can be the reason that KM variable in Unit is null (and in the same time METERS is not null)

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• In Django, how to create tables from an SQL file when syncdb is run

  - by Sidney

  Hi, How do I make syncdb execute SQL queries (for table creation) defined by me, rather then generating tables automatically. I'm looking for this solution as some particular models in my app represent SQL-table-views for a legacy-database table. So, I've created their SQL-views in my django-DB like this: CREATE VIEW legacy_series AS SELECT * FROM legacy.series; I have a reverse engineered model that represents the above view/legacytable. But whenever I run syncdb, I have to create all the views first by running sql scripts, otherwise syncdb simply creates tables for them (if a view is not found). How do I make syncdb run the above mentioned SQL?

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• Dynamic data validation in ASP.NET MVC

  - by user252160

  I've recently read about the model validation capabilities of ASP.NET MVC which are all very cool until a certain point. What happens if the application doesn't know the data that it works with because it is all stored in DB and built together at runtime. Just like in Drupal, I'd like to be able to define custom types at runtime, and assign runtime validation rules as well. Obviously, the idea of assigning attributes to well established models is now gone. What else could be done ? I am thinking in terms of rules being stored as JSON objects in the DB fields or something like that.

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• Are there any modern platforms with non-IEEE C/C++ float formats?

  - by Patrick Niedzielski

  Hi all, I am writing a video game, Humm and Strumm, which requires a network component in its game engine. I can deal with differences in endianness easily, but I have hit a wall in attempting to deal with possible float memory formats. I know that modern computers have all a standard integer format, but I have heard that they may not all use the IEEE standard for floating-point integers. Is this true? While certainly I could just output it as a character string into each packet, I would still have to convert to a "well-known format" of each client, regardless of the platform. The standard printf() and atod() would be inadequate. Please note, because this game is a Free/Open Source Software program that will run on GNU/Linux, *BSD, and Microsoft Windows, I cannot use any proprietary solutions, nor any single-platform solutions. Cheers, Patrick

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• Combining Two Models in Rails for a Form

  - by matsko

  Hey Guys. I'm very new with rails and I've been building a CMS application backend. All is going well, but I would like to know if this is possible? Basically I have two models: @page { id, name, number } @extended_page { id, page_id, description, image } The idea is that there are bunch of pages but NOT ALL pages have extended_content. In the event that there is a page with extended content then I want to be able to have a form that allows for editing both of them. In the controller: @page = Page.find(params[:id]) @extended= Extended.find(:first, :conditions = ["page_id = ?",@page.id]) @combined = ... #merge the two somehow So in the view: <%- form_for @combined do |f| % <%= f.label :name % <%= f.text_field :name % ... <%= f.label :description % <%= f.text_field :description % <%- end This way in the controller, there only has to be one model that will be updated (which will update to both). Is this possible?

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• iPhone: custom UITableViewCell with Interface Builder -> how to release cell objects?

  - by Stefan Klumpp

  The official documentation tells me I've to do these 3 things in order to manage the my memory for "nib objects" correctly. @property (nonatomic, retain) IBOutlet UIUserInterfaceElementClass *anOutlet; "You should then either synthesize the corresponding accessor methods, or implement them according to the declaration, and (in iPhone OS) release the corresponding variable in dealloc." - (void)viewDidUnload { self.anOutlet = nil; [super viewDidUnload]; } That makes sense for a normal view. However, how am I gonna do that for a UITableView with custom UITableViewCells loaded through a .nib-file? There the IBOutlets are in MyCustomCell.h (inherited from UITableViewCell), but that is not the place where I load the nib and apply it to the cell instances, because that happens in MyTableView.m So do I still release the IBOutlets in the dealloc of MyCustomCell.m or do I have to do something in MyTableView.m? Also MyCustomCell.m doesn't have a - (void)viewDidUnload {} where I can set my IBOutlets to nil, while my MyTableView.m does.

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• Efficient data structure design

  - by Sway

  Hi there, I need to match a series of user inputed words against a large dictionary of words (to ensure the entered value exists). So if the user entered: "orange" it should match an entry "orange' in the dictionary. Now the catch is that the user can also enter a wildcard or series of wildcard characters like say "or__ge" which would also match "orange" The key requirements are: * this should be as fast as possible. * use the smallest amount of memory to achieve it. If the size of the word list was small I could use a string containing all the words and use regular expressions. however given that the word list could contain potentially hundreds of thousands of enteries I'm assuming this wouldn't work. So is some sort of 'tree' be the way to go for this...? Any thoughts or suggestions on this would be totally appreciated! Thanks in advance, Matt

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