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  • How to Initialise a static Map in Java

    - by fahdshariff
    How would you initialise a static Map in Java? Method one: Static initialiser Method two: instance initialiser (anonymous subclass) or some other method? What are the pros and cons of each? Here is an example illustrating two methods: import java.util.HashMap; import java.util.Map; public class Test { private static final Map<Integer, String> myMap = new HashMap<Integer, String>(); static { myMap.put(1, "one"); myMap.put(2, "two"); } private static final Map<Integer, String> myMap2 = new HashMap<Integer, String>(){ { put(1, "one"); put(2, "two"); } }; }

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  • How to set background image in Java?

    - by Dew
    I am developing a simple platform game using Java using BlueJ as the IDE. Right now I have player/enemy sprites, platforms and other items in the game drawn using polygons and simple shapes. Eventually I hope to replace them with actual images. For now I would like to know what is the simplest solution to setting an image (either URL or from local source) as the 'background' of my game window/canvas? I would appreciate it if it isn't something long or complex as my programming skills aren't very good and I want to keep my program as simple as possible. Kindly provide example codes with comments to elaborate on their function, and also if it's in its own class, how to call on relevant methods used by it on other classes. Thank you very much.

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  • How To Discover RSS Feeds for a given site.

    - by ktolis
    The quest is, given a site url (say http://stackoverflow.com/ ) to return the list of all the feeds available on the site. Methods acceptable: a) use a 3rd party service (google?, yahoo?, ...) programmatically b) using a crawler/spider (and some tips on how to configure the spider to return the rss/xml feeds only) c) programmatically using c/c++/php (any language/library) The task here is not to get the feeds contained on the page returned by the url but ALL the feeds that are available on the server at any depth... in any cases please provide a simple usage example.

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  • Does lamda in List.ForEach leads to memory leaks and performance problems ?

    - by Monomachus
    I have a problem which I could solve using something like this sortedElements.ForEach((XElement el) => PrintXElementName(el,i++)); And this means that I have in ForEach a lambda which permits using parameters like int i. I like that way of doing it, but i read somewhere that anonymous methods and delegates with lambda leads to a lot of memory leaks because each time when lambda is executed something is instantiated but is not released. Something like that. Could you please tell me if this is true in this situation and if it is why?

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  • Why won't this TextArea return to non-Bold format, or is Font.PLAIN just like an "add-on"?

    - by JIM
    I am trying to Create a Simple Notepad in Java, i would post the full code but i didnt think it would be necessary since the problem is here(i think). Please Help. if(cb.getSelectedItem().equals("Plain")){ MainText.setFont(new Font(getFontName(MainText),Font.PLAIN,getFontSize(MainText)));} here are the above used methods public int getFontSize(TextArea t){ return t.getFont().getSize(); } public String getFontName(TextArea t){ return t.getFont().getFontName(); } public int getFontStyle(TextArea t){ return t.getFont().getStyle(); }

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  • What really is the purpose of "base" keyword in c#?

    - by Pandiya Chendur
    Thus for used base class for some commom reusable methods in every page of my application... public class BaseClass:System.Web.UI.Page { public string GetRandomPasswordUsingGUID(int length) { string guidResult = System.Guid.NewGuid().ToString(); guidResult = guidResult.Replace("-", string.Empty); return guidResult.Substring(0, length); } } So if i want to use this method i would just do, public partial class forms_age_group : BaseClass { protected void Page_Load(object sender, EventArgs e) { //i would just call it like this string pass = GetRandomPasswordUsingGUID(10); } } It does what i want but there is a "Base" keyword that deals with base class in c# ... I really want to know when should use base keyword in my derived class.... Any good example...

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  • Interview question: difference between object and object-oriented languages.

    - by Bar
    My friend was asked the following question: what's the difference between object language and object-oriented language? It's a little unintelligible question. What does term «object language» correspond to? Does that mean «pure» object-oriented language, like the Wikipedia article says: Languages called "pure" OO languages, because everything in them is treated consistently as an object, from primitives such as characters and punctuation, all the way up to whole classes, prototypes, blocks, modules, etc. They were designed specifically to facilitate, even enforce, OO methods. Examples: Smalltalk, Eiffel, Ruby, JADE, VB.NET.

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  • How can I implement the same behavior as Dictionary.TryGetValue

    - by pblasucci
    So, given then following code type MyClass () = let items = Dictionary<string,int>() do items.Add ("one",1) items.Add ("two",2) items.Add ("three",3) member this.TryGetValue (key,value) = items.TrygetValue (key,value) let c = MyClass () let d = Dictionary<string,int> () d.Add ("one",1) d.Add ("two",2) d.Add ("three",3) And the following test code let r1,v1 = d.TryGetValue "one" let r2,v2 = c.TryGetValue "one" The r1,v1 line works fine. The r2,v2 line bombs; complaining c.TryGetValue must be given a tuple. Interestingly, in each line the signature of TryGetValue is different. How can I get my custom implementation to exhibit the same behavior as the BCL version? Or, asked another way, since F# has (implicitly) the concept of tuple parameters, curried parameters, and BCL parameters, and I know how to distinguish between curried and tuple-style, how can I force the third style (a la BCL methods)? Let me know if this is unclear.

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  • Keeping Computer Science Writing Accessible and Eloquent

    - by Federer
    This question is particularly aimed at descriptions and explanations of what is happening in a computer program, as well as any general advice or approaches for undertaking technical reports in Computer Science at both undergraduate and graduate levels. You see, I am having particular difficulty in the best way to explain what is happening. As in, given any given program from a multi-agent system to a standard webservice, the best and most eloquent way to say exactly what is going on, the logic behind it and it's respective justifications. Should I avoid saying class names? Avoid specifying methods? Keep referring to class variables and any particular references? I'm banging my head against the wall at trying to keep a solid technical foundation and making it accessible to people of all backgrounds. Apologies for the rather vague question. Cheers.

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  • jQuery variables and scope

    - by Peuge
    I am writing a jQuery plugin and am running into a few problems with regard to variables. For example I have the following skeleton structure for my plugin, which is going to act on a textbox. In my init function I want to set a variable and bind a keypress event to my textbox. That keypress event needs to call another function, in which I need the variable. Is this possible? (function($){ var methods = { init : function(options){ return this.each(function(){ var $this = $(this); var someVar = 'somevar'; $this.keypress(function(event){ //I want to call my customFunction }); }); }, customFunction : function(){ //I am wanting to access 'someVar' here }; $.fn.mynamespace = function(method){ //handle which method to call here }; })(jQuery); Many thanks in advance.

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  • How to pass a linc to class function and call it?

    - by Kabumbus
    So I have a class like class mySafeData { public: void Set( int i ) { myMutex.lock(); myData = i; myMutex.unlock(); } void Get( int& i) { myMutex.lock(); i = myData; myMutex.unlock(); } private: int myData; boost::mutex myMutex; }; its instance is running. Lets call instance A. I want to create a new class that would take as a start up argument some kind of link to Getter from A and would be capable to somehow save link to thet getter for calling it inside its private methods vhen needed. how to do such thing?

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  • ASP.NET MVC - How to Preserve ModelState Errors Across RedirectToAction?

    - by RPM1984
    Hi Guys, I have the following two action methods (simplified for question): [HttpGet] public ActionResult Create(string uniqueUri) { // get some stuff based on uniqueuri, set in ViewData. return View(); } [HttpPost] public ActionResult Create(Review review) { // validate review if (validatedOk) { return RedirectToAction("Details", new { postId = review.PostId}); } else { ModelState.AddModelError("ReviewErrors", "some error occured"); return RedirectToAction("Create", new { uniqueUri = Request.RequestContext.RouteData.Values["uniqueUri"]}); } } So, if the validation passes, i redirect to another page (confirmation). If an error occurs, i need to display the same page with the error. If i do return View(), the error is displayed, but if i do return RedirectToAction (as above), it loses the Model errors. I'm not surprised by the issue, just wondering how you guys handle this? I could of course just return the same View instead of the redirect, but i have logic in the "Create" method which populates the view data, which i'd have to duplicate. Any suggestions?

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  • How to control overlapping Alpha fades on iPhone...

    - by ReduxDJ
    I have two animation methods, basically the just repeat... How do I prevent them from overlapping and flickering, is there a convenient way to do this? Thanks, -(void) doPowerChangeAnimUp { powerIconChange .alpha = 0; [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDidStopSelector:@selector(animationDidStop:)]; [UIView setAnimationDelegate:self] ; [UIView setAnimationDuration:2]; [powerIconChange setAlpha:1]; [UIView commitAnimations]; } -(void)animationDidStop:(NSString *)animationID { [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDelegate:self] ; [UIView setAnimationDidStopSelector:@selector(doPowerChangeAnimUp)]; [UIView setAnimationDuration:2]; [powerIconChange setAlpha:0]; [UIView commitAnimations]; }

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  • How do I construct a 3D model of a room from 2 stereo cameras? What is the determining factor to an

    - by yasumi
    Currently, I have extracted depth points to construct a 3D model from 2 stereo cameras. The methods I have used are openCV graphCut method and a software from http://sourceforge.net/projects/reconststereo/. However, the generated 3D models are not very accurate, which leads me to question: 1) What is the problem with pixel-based method? 2) Should I change my pixel-based method to feature-based or object-recognition-based method? Is there a best method? 3) Are there any other ways to do such reconstruction? Additionally, the depth extracted comes only from 2 images. What if I am turning the camera 360 degrees to obtain a video? Looking forward to suggestion on how to combine this depth information. Thank you very much :)

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  • NSURLConnection shown as leaking in instruments

    - by Gyozo Kudor
    Hello another stupid question regarding leaks and also NSURLConnection. How do i release it? Is it enough if i release in the following 2 methods? (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error (void)connectionDidFinishLoading:(NSURLConnection *)connection Because in instruments it shows me the line where I alloc my connection as the source of leaking. OK I don't get it. After the following code my urlConnection has a retain count of 2. WTF? NSURLConnection *urlConnection = [[NSURLConnection alloc] initWithRequest: urlRequest delegate: self]; This is the line that instruments points me to. I find this very weird.

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  • With the attachment_fu rails plugin, is there any way to delete files uploaded to Amazon S3?

    - by Eric Nguyen
    Let's say I'm using attachment_fu to attach profile pics to user profiles in a system, with Amazon S3 used as the actual file storage. When users upload new profile pics, I'd like to replace the attached file with the new one. I can do this within my database (i.e. the file metadata) easily, but attachment_fu doesn't seem to provide methods for deleting the files from S3. Am I missing something, or am I approaching this the wrong way? Many thanks!

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  • Overloading Controller Actions

    - by DaveDev
    Hi Guys I was a bit surprised a few minutes ago when I tried to overload an Action in one of my Controllers I had public ActionResult Get() { return PartialView(/*return all things*/); } I added public ActionResult Get(int id) { return PartialView(/*return 1 thing*/); } .... and all of a sudden neither were working I fixed the issue by making 'id' nullable and getting rid of the other two methods public ActionResult Get(int? id) { if (id.HasValue) return PartialView(/*return 1 thing*/); else return PartialView(/*return everything*/); } and it worked, but my code just got a little bit ugly! Any comments or suggestions? Do I have to live with this blemish on my Controllers? Thanks Dave

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  • Accessing entire netflix catalog via API v1.5

    - by Stone
    Netflix recently updated their API methods for obtaining the full Netflix catalog. I'm curious if anyone has had any success accessing these new xml documents and downloading them via API v1.5 (9/2012). Previously, you could download the entire Netflix catalog via one API call (which I had working perfectly). Now, there are supposedly two calls to make: one for dvd's and one for streaming movies. I cannot make these calls return anything except for an empty array. Please don't offer an answer unless you have personally downloaded the entire catalog via these new API's. Bonus points if you can tell me how to do it in Ruby. http://developer.netflix.com/blog/read/Update_Changes_for_the_Public_API

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  • Avoiding class_eval in Ruby metaprogramming

    - by Peter
    I want to have a return_empty_set class method in Ruby, similar to the attr_reader methods. My proposed implementation is class Class def return_empty_set *list list.each do |x| class_eval "def #{x}; Set.new; end" end end end and example usage: class Foo return_empty_set :one end Foo.new.one # returns #<Set: {}> but resorting to a string seems like quite a hack. Is there a cleaner or better way to write this, perhaps avoiding class_eval? Or is this the best way to go?

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  • Why Aren't Programs Written In Assembly More Often?

    - by mudge
    It seems to be a mainstream opinion that assembly programming takes longer and is more difficult to program in than a higher level language such as C. Therefore it seems to be recommend or assumed that it is better to write in a higher level language for these reasons and for the reason of better portability. Recently I've been writing in x86 assembly and it has dawned on me that perhaps these reasons are not really true, except perhaps portability. Perhaps it is more of a matter of familiarity and knowing how to write assembly well. I also noticed that programming in assembly is quite different than programming in an HLL. Perhaps a good and experienced assembly programmer could write programs just as easily and as quickly as an experienced C programmer writing in C. Perhaps it is because assembly programming is quite different than HLLs, and so requires different thinking, methods and ways, which makes it seem very awkward to program in for the unfamiliar, and so gives it its bad name for writing programs in. If portability isn't an issue, then really, what would C have over a good assembler such as NASM?

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  • How to read and write UTF-8 to disk on the Android?

    - by Rob Kent
    I cannot read and write extended characters (French accented characters, for example) to a text file using the standard InputStreamReader methods shown in the Android API examples. When I read back the file using: InputStreamReader tmp = new InputStreamReader(in); BufferedReader reader = new BufferedReader(tmp); String str; while ((str = reader.readLine()) != null) { ... the string read is truncated at the extended characters instead of at the end-of-line. The second half of the string then comes on the next line. I'm assuming that I need to persist my data as UTF-8 but I cannot find any examples of that, and I'm new to Java. Can anyone provide me with an example or a link to relevant documentation?

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  • Login or Register (Ruby on rails)

    - by DanielZ
    Hello stackoverflow, I'm working on an Ruby on Rails application (2.3.x) and i want to make a form that lets the user login or register. I want to do this in the same form. I have a JS function that replaces the form elements like this: Login form: <% form_for @user do |f| %> <div id="form"> <%= f.label :email, "E-mail" %> <%= f.text_field :email %> <%= f.label :password, "Password" %> <%= f.password_field :password %> <%= link_to "I don't have an account, "#", :id => "changeForm"%> <%= f.submit "Login" %> </div> <% end %> The id "changeForm" triggers a JS function that changes the form elements. So if you press the url the html looks like this: <% form_for @user do |f| %> <div id="form"> <%= f.label :name, "Name" %> <%= f.text_field :name %> <%= f.label :email, "E-mail" %> <%= f.text_field :email %> <%= f.label :password, "Password" %> <%= f.password_field :password %> <%= f.label :password_confirmation, "Password confirmation" %> <%= f.password_field :password_confirmation %> <%= link_to "I do have an account, "#", :id => "changeForm"%> <%= f.submit "Register" %> </div> <% end %> I added the neccesary validations to my user model: class User < ActiveRecord::Base attr_reader :password validates_presence_of :name, :email, :password validates_format_of :email, :with => /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i validates_confirmation_of :password But what happens when you fill in the email / password you get the errors that the name is missing and that the password fields aren't confirmed. So i could do some nasty programming in my user model like this: #if password_conf or the name are present the user has tried to register... if params[:user][:password_confirmation].present? || params[:user][:name].present? #so we'll try to save the user if @user.save #if the user is saved authenticate the user current_session.user = User.authenticate(params[:user]) #if the user is logged in? if current_session.user.present? flash[:notice] = "succesvully logged redirect_to some_routes_path else #not logged in... flash[:notice] = "Not logged in" render :action => "new" end else #user not saved render :action => "new" end else #So if the params[:user][:password_confirmation] or [:user][:name] weren't present we geuss the user wants to login... current_session.user = User.authenticate(params[:user]) #are we logged_in? if current_session.user.present? flash[:notice] = "Succesvully logged in" redirect_to some_routes_path else #errors toevoegen @user.errors.add(:email, "The combination of email/password isn't valid") @user.errors.add(:password," ") render :action => "new" end end end Without validations this (imho dirty code and should not be in the controller) works. But i want to use the validates_presence_of methods and i don't want to slap the "conventions over configurations" in the face. So another thing i have tried is adding a hidden field to the form: #login form <%= f.hidden_field :login, :value => true %> # and ofcourse set it to false if we want to register. And then i wanted to use the method: before_validation before_validation_on_create do |user| if params[:user].login == true #throws an error i know... validates_presence_of :email, :password validates_format_of :email, :with => /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i else validates_presence_of :name, :email, :password validates_format_of :email, :with => /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i validates_confirmation_of :password end end But this doesn't work because i can't access the params. And login isn't a attribute for the user object. But i thought that in this way i could validate the email and password params if the user wants to login. And all the other attrs if the user want to register. So all i could think of doesn't work how i want it to work. So my main goal is this: 1 form for login/register with the use of the validation methods in the user model. So if we want to login but don't fill in any information = give validation errors. And if the user wants to login but the email/password combination doens't match give the "@user.errors.add(:email, "the combination wasn't found in the db...")". And the same goes for user register... Thanks in advance!

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  • (Django) Trim whitespaces from charField

    - by zardon
    How do I strip whitespaces (trim) from the end of a charField in Django? Here is my Model, as you can see I've tried putting in clean methods but these never get run. I've also tried doing name.strip(), models.charField().strip() but these do not work either. Is there a way to force the charField to trim automatically for me? Thanks. class Employee(models.Model): """(Workers, Staff, etc)""" name = models.CharField(blank=True, null=True, max_length=100) # This never gets run def clean_variable(self): data = self.cleaned_data['variable'].strip() return data def __unicode__(self): return self.name class Meta: verbose_name_plural = 'Employees' # This never gets run either class EmployeesForm(forms.ModelForm): class Meta: model = Employee def clean_description(self): #if not self.cleaned_data['description'].strip(): # raise forms.ValidationError('Your error message here') self.cleaned_data['name'].strip()

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  • Error handling and polymorphism

    - by Neeraj
    I have an application with some bunch of code like this: errCode = callMainSystem(); switch (errCode){ case FailErr: error("Err corresponding to val1\n"); case IgnoreErr: error("Err corresponding to val2\n"); ... ... default: error("Unknown error\n"); } The values are enum constants. Will it make some sense to have something like: // Error* callMainSystem() ... Some code return FaileErr(); // or some other error // handling code Error* err = callMainSystem(); err->toString(); The Error class may be made singleton as it only has to print error messages. What are the pros and cons of above methods,size is an important criteria as the application needs to be supported on embedded devices as well. P.S: I don't want to use exception handling because of portability issues and associated overheads.

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  • Good code architecture for this problem?

    - by RCIX
    I am developing a space shooter game with customizable ships. You can increase the strength of any number of properties of the ship via a pair of radar charts*. Internally, i represent each ship as a subclassed SpaceObject class, which holds a ShipInfo that describes various properties of that ship. I want to develop a relatively simple API that lets me feed in a block of relative strengths (from minimum to maximum of what the radar chart allows) for all of the ship properties (some of which are simplifications of the underlying actual set of properties) and get back a ShipInfo class i can give to a PlayerShip class (that is the object that is instantiated to be a player ship). I can develop the code to do the transformations between simplified and actual properties myself, but i would like some recommendations as to what sort of architecture to provide to minimize the pain of interacting with this translator code (i.e. no methods with 5+ arguments or somesuch other nonsense). Does anyone have any ideas? *=not actually implemented yet, but that's the plan.

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