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  • Can I add and remove elements of enumeration at runtime in Java

    - by Brabster
    It is possible to add and remove elements from an enum in Java at runtime? For example, could I read in the labels and constructor arguments of an enum from a file? @saua, it's just a question of whether it can be done out of interest really. I was hoping there'd be some neat way of altering the running bytecode, maybe using BCEL or something. I've also followed up with this question because I realised I wasn't totally sure when an enum should be used. I'm pretty convinced that the right answer would be to use a collection that ensured uniqueness instead of an enum if I want to be able to alter the contents safely at runtime.

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  • How to show a page after a specific time period?

    - by Mahfuz
    I want to build an online quiz test site. Suppose, exam will start at 10:00 am and a student login to give exam at 9:45 am. Whenever the student clicks 'Take Exam' button, he/she cannot not get access to the question paper because the exam time is 10:00 am and there are still 15 minutes before the exam start. Now I want to put some Javascript or PHP code that will prohibit the students to give exam earlier and if a students come early, it will show a stopwatch which display the remaining time before exam time and when the current time is equal to exam time then he/she will be directly redirected to the question paper page.

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  • Why does std::map operator[] create an object if the key doesn't exist?

    - by n1ck
    Hi, I'm pretty sure I already saw this question somewhere (comp.lang.c++? Google doesn't seem to find it there either) but a quick search here doesn't seem to find it so here it is: Why does the std::map operator[] create an object if the key doesn't exist? I don't know but for me this seems counter-intuitive if you compare to most other operator[] (like std::vector) where if you use it you must be sure that the index exists. I'm wondering what's the rationale for implementing this behavior in std::map. Like I said wouldn't it be more intuitive to act more like an index in a vector and crash (well undefined behavior I guess) when accessed with an invalid key? Refining my question after seeing the answers: Ok so far I got a lot of answers saying basically it's cheap so why not or things similar. I totally agree with that but why not use a dedicated function for that (I think one of the comment said that in java there is no operator[] and the function is called put)? My point is why doesn't map operator[] work like a vector? If I use operator[] on an out of range index on a vector I wouldn't like it to insert an element even if it was cheap because that probably mean an error in my code. My point is why isn't it the same thing with map. I mean, for me, using operator[] on a map would mean: i know this key already exist (for whatever reason, i just inserted it, I have redundancy somewhere, whatever). I think it would be more intuitive that way. That said what are the advantage of doing the current behavior with operator[] (and only for that, I agree that a function with the current behavior should be there, just not operator[])? Maybe it give clearer code that way? I don't know. Another answer was that it already existed that way so why not keep it but then, probably when they (the ones before stl) choose to implement it that way they found it provided an advantage or something? So my question is basically: why choose to implement it that way, meaning a somewhat lack of consistency with other operator[]. What benefit do it give? Thanks

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  • Codesample with bufferoverflow (gets method). Why does it not behave as expected?

    - by citronas
    This an extract from an c program that should demonstrate a bufferoverflow. void foo() { char arr[8]; printf(" enter bla bla bla"); gets(arr); printf(" you entered %s\n", arr); } The question was "How many input chars can a user maximal enter without a creating a buffer overflow" My initial answer was 8, because the char-array is 8 bytes long. Although I was pretty certain my answer was correct, I tried a higher amount of chars, and found that the limit of chars that I can enter, before I get a segmentation fault is 11. (Im running this on A VirtualBox Ubuntu) So my question is: Why is it possible to enter 11 chars into that 8 byte array?

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  • When to use <strong> and when to use <b>?

    - by metal-gear-solid
    When to use <strong> and when to use <b> or other ways to give look of bold? strong has semantic value ( and useful for screen reader while b is presentation (and even valid in HTML 5). my question is not what is the difference between strong and b. The question is when to use semantic tag and when to use just to make text bold Should I always use <strong> if client's content files (MS word files) has some words bold in content paragraphs? How can we know when client want to give emphasis to text and when he just want to make text bold for presentation/aesthetic purpose? If it's client job to tell us, then how to explain this scenario to client to give us clear info on "when he just want to make text bold for presentation/aesthetic purpose" ?

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  • Problem executing with Python+MySQL

    - by Satya
    Hi, I am not getting the reason why my python script is not working though I hv put all the things correctly as my knowledge.The below test I did and it worked fine.But when I import the MySQLdb in my script it gives error as no module name MySQLdb. **C:\Python26python Python 2.6.1 (r261:67517, Dec 4 2008, 16:51:00) [MSC v.1500 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. import MySQLdb ** Kindly let me know the reason for this error. And all the development is going on in windows XP, python 2.6, mysql 4.0.3 Earlier 1 hour back I have posted the question but some mistake was there in the question itself..

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  • Counting unique values in a column with a shell script

    - by Lilly Tooner
    Hello. I have a tab delimited file with 5 columns and need to retrieve a count of just the number of unique lines from column 2. I would normally do this with Perl/Python but I am forced to use the shell for this one. I have successfully in the past used *nix uniq function piped to wc but it looks like I am going to have to use awk in here. Any advice would be greatly appreciated. (I have asked a similar question previously about column checks using awk but this is a little different and I wanted to separate it so if someone in the future has this question this will be here) Many many thanks! Lilly

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  • List of dependency jar files in Maven

    - by Sindri Traustason
    Using Maven 2, is there a way I can list out the jar dependencies as just the file names? mvn dependency:build-classpath can list the jar files, but that will include the full path to their location in my local repository. What I need is essentially just a list of the file names (or the file names that the copy-dependencies goal copied). So the list I need would be something like activation-1.1.jar,antlr-2.7.6.jar,aopalliance-1.0.jar etc... ideally as a maven property, but I guess, a file such as build-classpath can generate will do. What I am trying to achieve is writing a Bundle-ClassPath to an otherwise manually maintained MANIFEST.MF file for a OSGi bundle. (You shouldn't need to understand this bit to answer the question.) To clarify: The question is not about how to write manifest headers into the MANIFEST.MF file in a jar (that is easily googleble). I am asking about how to get the data I want to write, namely the list shown above.

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  • Do Managers in Python Multiprocessing module lock the shared data?

    - by AnonProcess
    This Question has been asked before: http://stackoverflow.com/questions/2936626/how-to-share-a-dictionary-between-multiple-processes-in-python-without-locking However I have several doubts regarding the program given in the answer: The issue is that the following step isn't atomic d['blah'] += 1 Even with locking the answer provided in that question would lead to random results. Since Process 1 read value of d['blah'] saves it on the stack increments it and again writes it. In Between a Process 2 can read the d['blah'] as well. Locking means that while d['blah'] is being written or read no other process can access it. Can someone clarify my doubts?

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  • How to close a form in UserControl

    - by FJPoort
    I created a UserControl with the buttons Save, Close and Cancel. I want to close the form without saving on the Cancel button, prompt a message to save on the Close button and Save without closing on the Save button. Normally, I would have used this.Close() on the Cancel button, but the UserControl doesn't have such an option. So I guess I have to set a property for that. Scrolling down the "Questions that may already have your answer" section, I came across this question: How to close a ChildWindow from an UserControl button loaded inside it? I used the following C# code: private void btnCancel_Click(object sender, EventArgs e) { ProjectInfo infoScreen = (ProjectInfo)this.Parent; infoScreen.Close(); } This does the job for one screen, but I wonder if I have to apply this code for all the screen I have? I think there should be a more efficient way. So my question is: Do I need to apply this code for every form I have, or is there another (more efficient) way?

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  • An exception to the "only one implementation" rule ?

    - by ereOn
    While I was reading the accepted answer of this question, I had the following question: Typically, methods are defined in header files (.hpp or whatever), and implementation in source files (.cpp or whatever). One of the main reasons it is bad practice to ever include a "source file" (#include <source_file.cpp>) is that its methods implementation would then be duplicated, resulting in linking errors. When one writes: #ifndef BRITNEYSPEARS_HPP #define BRITNEYSPEARS_HPP class BritneySpears { public: BritneySpears() {}; // Here the constructor has implementation. }; #endif /* BRITNEYSPEARS_HPP */ He is giving the implementation of the constructor (here an "empty" implementation, but still). But why then including this header file multiple times (aka. on different source files) will not generate a "duplicate definition" error at link time ?

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  • Delphi developer switching to C#

    - by Dorin Duminica
    Hello, I'm a Delphiholic for quite some time now and lately I was thinking of learning some C# as well, however I'm kinda' "afraid of the unknown", I've done some simple apps as a test drive for C# and I have to admit that I've liked it, HOWEVER I do not really like the IDE... that being said here's the question that I would appreciate if others who went down this path would answer: As a Delphi developer what are the "main basic" changes from the Delphi language(by basic I mean basic -- utility functions, streams, etc.), I'm used to add "System, Classes, Windows" to uses not "use System.XXX.YYY.ZZZ", I'm trying to make a partial equality in my mind from Delphi to C# until I can see where does Delphi go hand-in-hand with C# and so on... I hope the question is pretty clear, if not, do not hesitate to swear me and I'll try to clarify as well as I can :-)

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  • How to change code settings in eclipse

    - by Maven
    Sorry if the question title is confusing. Let me explain further. I am building a Java project with Eclipse. In my Java product I have conditionals that determine what code is included in the product and relies on static final constants for dead stripping. class BuildFlags { public static final boolean SOME_FLAG = true; // Need to set this programmatically } class SomeOtherClass { public void someMethod() { if (BuildFlags.SOME_FLAG) { // flag specific code } } } My question is how can I change BuildFlags.SOME_FLAG (above) so that I can run a special build without changing the source? Is there some way I can pass flags to the jvm (from eclipse) which I can then access to set this flag programatically?

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  • Backbone inheritance - deep copying

    - by Ed .
    I've seen this question regarding inheritance in Backbone: Backbone.js view inheritance. Useful but doesn't answer my question. The problem I'm experiencing is this: Say I have a class Panel (model in this example); var Panel = Backbone.Model.extend({ defaults : { name : 'my-panel' } }); And then an AdvancedPanel; var AdvancedPanel = Panel.extend({ defaults : { label : 'Click to edit' } }); The following doesn't work: var advancedPanel = new AdvancedPanel(); alert(advancedPanel.get('name')); // Undefined :( JSFiddle here: http://jsfiddle.net/hWmnb/ I guess I can see that I can achieve this myself through some custom extend function that creates a deep copy of the prototype, but this seems like a common thing that people might want from Backbone inheritance, is there a standard way of doing it?

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  • How long does a MailItem.Property[myProperty] live?

    - by Darien Ford
    I'm writing a TransportAgent for Exchange and want to tag a MailItem with some identifying information. The MailItem class seems to have this functionality with the MailItem.Properties property; however, my question is to the length of time an entry would remain available. e.g. e.MailItem.Properties.Add(new KeyValuePair<string,object>("MyKey", "myValue")); After this MailItem is delivered to the correct mailbox, if someone were to reply to the email, would the newly created reply retain that set value? I think while writing this question out I have answered it for myself (which rationally would be no) but any practical experience and insight would be appreciated.

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  • understanding memory mapping in directx

    - by numerical25
    So my question is ... " When your using the mapping feature to write into a memory buffer, are you really just saving the whole procedure into a queue so directX executes it when finished with other tasks???" I ask this question because this is my perception of mapping when writing to a buffer. I just want to make sure my perception is correct. I understand that the monitor moves extremely slow in compared to the processor, and I am sure the processor can execute 10 times the amount the screen can refresh. So is this one of the reason you should map when writing to a buffer. so each procedure can be done in a orderly fashion. If someone could elaborate, that would be great. thanks

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  • MVC - Sanitizing data, where?

    - by dierre
    I'm using CakePHP but it's a question about the MVC pattern. I have in my form the input-text for the tags (separated by commas). To add the tags I've created a Tag model method that basically check if the tag exists and then add the new tag or just a new unit in the tag counter (the Tag model has these fields: id, name, slug, count). In the controller I explode the tags field and pass one tag at a time. The question is: where do I sanitize data? In the controller or in the model method? I think it should be in the controller because that's where I explode but in term of reusability I think I should sanitize data in the model. What do you think?

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  • client computer name

    - by Anup Prakash
    After getting the client(Website user) IP address. Now i want to go one step ahead by knowing the Computer name of the user. So, agian i need help from my question viewer to help me regarding computer name of the client(website user). I tried it by myself using google. But at last i thought it is better to ask to all of you who have better and best answers. Thanx again to see my query. And much much thanx for them who are answering this question.

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  • Why does PHP 5.2 disallow abstract static class methods?

    - by Artem Russakovskii
    After enabling strict warnings in PHP 5.2, I saw a load of strict standards warnings from a project that was originally written without strict warnings: Strict Standards: Static function Program::getSelectSQL() should not be abstract in Program.class.inc The function in question belongs to an abstract parent class Program and is declared abstract static because it should be implemented in its child classes, such as TVProgram. I did find references to this change here: Dropped abstract static class functions. Due to an oversight, PHP 5.0.x and 5.1.x allowed abstract static functions in classes. As of PHP 5.2.x, only interfaces can have them. My question is: can someone explain in a clear way why there shouldn't be an abstract static function in PHP?

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  • Is it possible to apply inheritance to a Singleton class?

    - by Bragaadeesh
    Hi, Today I faced one question in interview. Is it possible to apply inheritance concept on Singleton Classes. I said since the constructor is private, we cannot extend that Singleton class (can someone please validate this). Next thing he asked me is to apply inheritance on that Singleton class. So, I made the Singleton's constructor as protected thinking that child's constructor also has be protected. But I was wrong the child can have a modifier either equal to or higher than that. So, I asked him to give a real world example on such a case. He was not able to give me one and said that I cant ask questions and wanted me to tell whether this scenario is possible or not. I went kind of blank. My question here is, Is this possible? Even if its possible, what is the use of it? What real world scenario would demand such a use. Thanks

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  • How to use sound and images in a Java applet?

    - by Click Upvote
    Question 1: How should I structure my project so the sound and images files can be loaded most easily? Right now, I have the folder: C:\java\pacman with the sub-directory C:\java\pacman\src containing all the code, and C:\java\pacman\assets containing the images and .wav files. Is this the best structure or should I put the assets somewhere else? Question 2: What's the best way to refer to the images/sounds without using the full path e.g C:\java\pacman\assets\something.png to them? If I use the getCodeBase() function it seems to refer to the C:\java\pacman\bin instead of C:\java\pacman\. I want to use such a function/class which would work automatically when i compile the applet in a jar as well as right now when I test the applet through eclipse. Question 3: How should I load the images/sounds? This is what I'm using now: 1) For general images: import java.awt.Image; public Image getImg(String file) { //imgDir in this case is a hardcoded string containing //"C:\\java\\pacman\\assets\\" file=imgDir + file; return new ImageIcon(file).getImage(); } The images returned from this function are used in the drawImage method of the Graphics class in the paint method of the applet. 2) For a buffered image, which is used to get subImages and load sprites from a sprite sheet: public BufferedImage getSheet() throws IOException { return ImageIO.read(new File(img.getPath("pacman-sprites.png"))); } Later: public void loadSprites() { BufferedImage sheet; try { sheet=getSheet(); redGhost.setNormalImg(sheet.getSubimage(0, 60, 20, 20)); redGhost.setUpImg(sheet.getSubimage(0, 60, 20, 20)); redGhost.setDownImg(sheet.getSubimage(30, 60, 20, 20)); redGhost.setLeftImg(sheet.getSubimage(30, 60, 20, 20)); redGhost.setRightImg(sheet.getSubimage(60, 60, 20, 20)); } catch (IOException e) { System.out.println("Couldnt open file!"); System.out.println(e.getLocalizedMessage()); } } 3) For sound files: import sun.audio.*; import java.io.*; public synchronized void play() { try { InputStream in = new FileInputStream(filename); AudioStream as = new AudioStream(in); AudioPlayer.player.start(as); } catch (IOException e) { e.printStackTrace(); } }

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  • Saving data that is in a table efficiently and also is easy to retrieve and echo back out

    - by Harry
    Information I currently have a table which image is below, Problem I have made this table using ul & li Here is the code http://jsfiddle.net/8j2qe/1/ Question What would be the best way of storing the data in the image and easily displaying it? Keeping in mind that each column can only have 1 entry. Thank you! And any questions will be answered ASAP! EDIT Sorry, I dont think I was clear enough in my initial question. What I am asking is, what is the best way to store and then display this type of data. I want to DISPLAY data from my database to show like it would in the image. Should I have a column in my database for each column on the table, then say either A,B,C or D depending on what column it is in but then how would I display it using PHP in my code provided? Im struggling to find a good way of explaining this, I am sorry.

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  • Insert new row with data computed from other rows

    - by Tyler McHenry
    Suppose I have a MySQL table called MyTable, that looks like this: +----+------+-------+ | Id | Type | Value | +----+------+-------+ | 0 | A | 1 | | 0 | B | 1 | | 1 | A | 2 | | 1 | B | 3 | | 2 | A | 5 | | 2 | B | 8 | +----+------+-------+ And, for each Id, I want to insert a new row with type C whose Value is the sum of the type A and B values for the rows of the same Id. The primary key on this table is (Id, Type), so there's no question of duplication of Id,Type pairs. I can create the rows I want with this query: SELECT MyTable_A.Id AS Id, 'C' AS Type, (A_Val + B_Val) AS Value FROM (SELECT Id, Value AS A_Val FROM MyTable WHERE Type='A') AS MyTable_A JOIN (SELECT Id, Value AS B_Val FROM MyTable WHERE Type='B') AS MyTable_B ON MyTable_A.Id = MyTable_B.Id Giving: +----+------+-------+ | Id | Type | Value | +----+------+-------+ | 0 | C | 2 | | 1 | C | 5 | | 2 | C | 13 | +----+------+-------+ But the question is: How do I use this result to insert the generated type-C rows into MyTable? Is there a relatively simple way to do this with a query, or do I need to write a stored procedure? And if the latter, guidance would be helpful, as I'm not too well versed in them.

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  • Rails routing: how to mix "GET" and "PUT"

    - by thermans
    Not sure how to frame this question (I'm still wrapping my head around Rails). Let's try this: Say I wanted to implement the user side of Ryan Bates' excellent railscast on nested models. (He shows how to implement a survey where you can add and remove questions and answers dynamically). I want the user's side of this: to be able to answer questions and, not in the tutorial, be able to add comments. It seems to me that you have to implement a view that shows the questions and answers, allow selection of the answers, and the input of comments. So there would need to be a way to show the information, but also update the model on input, right? I know I'm not explaining this very well. I hope you understand what I'm getting at. Is it just a question of setting up the right routes? Or is there some controller mojo that needs to happen?

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