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  • Java: Inputting text from a file using split

    - by 00PS
    I am inputting an adjacency list for a graph. There are three columns of data (vertex, destination, edge) separated by a single space. Here is my implementation so far: FileStream in = new FileStream("input1.txt"); Scanner s = new Scanner(in); String buffer; String [] line = null; while (s.hasNext()) { buffer = s.nextLine(); line = buffer.split("\\s+"); g.add(line[0]); System.out.println("Added vertex " + line[0] + "."); g.addEdge(line[0], line[1], Integer.parseInt(line[2])); System.out.println("Added edge from " + line[0] + " to " + line[1] + " with a weight of " + Integer.parseInt(line[2]) + "."); } System.out.println("Size of graph = " + g.size()); Here is the output: Added vertex a. Added edge from a to b with a weight of 9. Exception in thread "main" java.lang.NullPointerException at structure5.GraphListDirected.addEdge(GraphListDirected.java:93) at Driver.main(Driver.java:28) I was under the impression that line = buffer.split("\\s+"); would return a 2 dimensional array of Strings to the variable line. It seemed to work the first time but not the second. Any thoughts? I would also like some feedback on my implementation of this problem. Is there a better way? Anything to help out a novice! :)

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  • Should I start with Trac 0.12 ?

    - by mree
    I'm going to start using Trac for the first time. From what I've gathered, the latest 0.12 is capable of supporting multiple project easily (which is something I will need since I got about 5 projects). However, it seems 0.12 is still in the development (0.12-dev). So, my question is, is it good enough for a newbie in Trac like me to use it? Does anyone has any experience using it ? It will be installed on a Linux server. BTW, I'll only be using the basic functions such as svn browser, wiki, tickets and others.

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  • Number of characters recommended for a statement

    - by liaK
    Hi, I have been using Qt 4.5 and so do C++. I have been told that it's a standard practice to maintain the length of each statement in the application to 80 characters. Even in Qt creator we can make a right border visible so that we can know whether we are crossing the 80 characters limit. But my question is, Is it really a standard being followed? Because in my application, I use indenting and all, so it's quite common that I cross the boundary. Other cases include, there might be a error statement which will be a bit explanatory one and which is in an inner block of code, so it too will cross the boundary. Usually my variable names look bit lengthier so as to make the names meaningful. When I call the functions of the variable names, again I will cross. Function names will not be in fewer characters either. I agree a horizontal scroll bar shows up and it's quite annoying to move back and forth. So, for function calls including multiple arguments, when the boundary is reached I will make the forth coming arguments in the new line. But besides that, for a single statement (for e.g a very long error message which is in double quotes " " or like longfun1()->longfun2()->...) if I use an \ and split into multiple lines, the readability becomes very poor. So is it a good practice to have those statement length restrictions? If this restriction in statement has to be followed? I don't think it depends on a specific language anyway. I added C++ and Qt tags since if it might. Any pointers regarding this are welcome.

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  • Arguments against Create or Update

    - by Nix
    Recently someone stated that they thought all Creates should be CreateOrUpdates. Instinctively i thought bad, but now I am trying to find out if I have any grounds. Situation interface IService{ void Create(Object a); void Update(Object a); } or interface IService{ void CreateOrUpdate(Object a); } My first thought is if you implemented everything CreateOrUpdate then you have no control if someone accidentally sends you wrong data, or concurrency issues where someone changes a "primary" field right before you call update.... But if you remove those cases, are there any other cons?

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  • How to pass non-fatal warnings from a library

    - by wRAR
    A library function parses a file and returns an object. If a parser encounters unknown data, missing values etc., it shouldn't throw an exception and stop parsing (because this is not fatal), but there should be a way to pass information about these things to a caller (so that warnings can be displayed in the UI, for example). How can these warning be returned? I'm thinking of passing a callback function/object into the library, are there any other possible solutions?

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  • How to reference a class that implements certain interface?

    - by vikp
    Hi, I have an interface for logging the exceptions, i.e. IExceptionLogger. This interface has 3 implementations: DBExceptionLogger, XMLExceptionLogger, CSVExceptionLogger. I have an application that will make a use of DBExceptionLogger. The application references only IExceptionLogger. How do I create an instance of DBExceptionLogger within the application. I can't reference the DBExceptionLogger directly since it will break the purpose of having IExceptionLogger interface. Thanks

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  • Validation - Data Integrity

    - by Thomas
    A table can only store 10 records in a particular state, 10 users over 30 years for example, the others must be less than 30 years. It is a business rule and as such should be respected. How to ensure that state? Think: multiple users accessing this table.

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  • Rapid Opening and Closing System.IO.StreamWriter in C#

    - by ccomet
    Suppose you have a file that you are programmatically logging information into with regards to a process. Kinda like your typical debug Console.WriteLine, but due to the nature of the code you're testing, you don't have a console to write onto so you have to write it somewhere like a file. My current program uses System.IO.StreamWriter for this task. My question is about the approach to using the StreamWriter. Is it better to open just one StreamWriter instance, do all of the writes, and close it when the entire process is done? Or is it a better idea to open a new StreamWriter instance to write a line into the file, then immediately close it, and do this for every time something needs to be written in? In the latter approach, this would probably be facilitated by a method that would do just that for a given message, rather than bloating the main process code with excessive amounts of lines. But having a method to aid in that implementation doesn't necessarily make it the better choice. Are there significant advantages to picking one approach or the other? Or are they functionally equivalent, leaving the choice on the shoulders of the programmer?

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  • MemoryStream instance timing help

    - by rod
    Hi All, Is it ok to instance a MemoryStream at the top of my method, do a bunch of stuff to it, and then use it? For instance: public static byte[] TestCode() { MemoryStream m = new MemoryStream(); ... ... whole bunch of stuff in between ... ... //finally using(m) { return m.ToArray(); } } Updated code public static byte[] GetSamplePDF() { using (MemoryStream m = new MemoryStream()) { Document document = new Document(); PdfWriter.GetInstance(document, m); document.Open(); PopulateTheDocument(document); document.Close(); return m.ToArray(); } } private static void PopulateTheDocument(Document document) { Table aTable = new Table(2, 2); aTable.AddCell("0.0"); aTable.AddCell("0.1"); aTable.AddCell("1.0"); aTable.AddCell("1.1"); document.Add(aTable); for (int i = 0; i < 20; i++) { document.Add(new Phrase("Hello World, Hello Sun, Hello Moon, Hello Stars, Hello Sea, Hello Land, Hello People. ")); } } My point was to try to reuse building the byte code. In other words, build up any kind of document and then send it to TestCode() method.

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  • Should I *always* import my file references into the database in drupal?

    - by sprugman
    I have a cck type with an image field, and a unique_id text field. The file name of the image is based on the unique_id. All of the content, including the image itself is being generated automatically via another process, and I'm parsing what that generates into nodes. Rather than creating separate fields for the id and the image, and doing an official import of the image into the files table, I'm tempted to only create the id field and create the file reference in the theme layer. I can think of pros and cons: 1) Theme Layer Approach Pros: makes the import process much less complex don't have to worry about syncing the db with the file system as things change more flexible -- I can move my images around more easily if I want Cons: maybe not as much The Drupal Way™ not as pure -- I'll wind up with more logic on the theme side. 2) Import Approach Pros: import method is required if we ever wanted to make the files private (we won't.) safer? Maybe I'll know if there's a problem with the image at import time, rather than view time. Since I'll be bulk importing, that might make a difference. if I delete a node through the admin interface, drupal might be able to delete the file for me, as well. Con: more complex import and maintenance All else being equal, simpler is always better, so I'm leaning toward #1. Are there any other issues I'm missing? (Since this is an open ended question, I guess I'll make it a community wiki, whatever that means.)

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  • #Define Compiler Directive in C#

    - by pm_2
    In C, I could declare a compiler directive as follows: #define MY_NUMBER 10 However, in C#, I only appear to be able to do this: #define MY_NUMBER Which is obviously useless in this case. Is this correct, or am I doing something wrong? If not, can anyone suggest a way of doing this, either at namespace or solution level? I thought of maybe creating a static class, but that seems to be overkill for one value.

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  • Is this SQL select code following good practice?

    - by acidzombie24
    I am using sqlite and will port to mysql (5) later. I wanted to know if I am doing something I shouldnt be doing. I tried purposely to design so I'll compare to 0 instead of 1 (I changed hasApproved to NotApproved to do this, not a big deal and I haven't written any code). I was told I never need to write a subquery but I do here. My Votes table is just id, ip, postid (I don't think I can write that subquery as a join instead?) and that's pretty much all that is on my mind. Naming conventions I don't really care about since the tables are created via reflection and is all over the place. select id, name, body, upvotes, downvotes, (select 1 from UpVotes where IPAddr=? AND post=Post.id) as myup, (select 1 from DownVotes where IPAddr=@0 AND post=Post.id) as mydown from Post where flag = '0' limit ?, ?"

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  • Patterns for avoiding jQuery silent fails

    - by Matias
    Is there any good practice to avoid your jQuery code silently fail? For example: $('.this #is:my(complexSelector)').doSomething(); I know that every time this line get executed, the selector is intended to match at least one element, or certain amount of elements. Is there any standard or good way to validate that? I thought about something like this: var $matchedElements = $('.this #is:my(complexSelector)'); if ($matchedElements.length < 0) throw 'No matched elements'; $matchedElements.doSomething(); Also I think unit testing would be a valid option instead of messing the code. My question may be silly, but I wonder whether there is a better option than the things that I'm currently doing or not. Also, maybe I'm in the wrong way checking if any element match my selector. However, as the page continues growing, the selectors could stop matching some elements and pieces of functionality could stop working inadvertently.

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  • Does MVC replace traditional manually created BLL?

    - by used2could
    I'm used to creating the UI, BLL, DAL by hand (some times I've used LINQ-to-SQL or SubSonic for the DAL). I've done several small projects using MVC since its release. On these projects I've still continued to write a BLL and DAL by hand and then incorporate those into the MVC's models/controllers. I'm looking to optimize my time on projects this seems like overkill and a potential waste of time. Question Would it be acceptable to roll a DAL such as SubSonic and directly use it in the Models/Controllers of my MVC web app? Now the models & controllers would act as the BLL. I just see this as a major timesaver to not have to worry about another tier. UPDATE: I just wanted to add that my concern isn't really with the DAL (I frequently use SubSonic and NH) but rather focus on the BLL. Sorry for the confusion.

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  • What's the best way to return different cells depending on position in a UITableView

    - by Robert Conn
    I have a grouped UITableView that has 3 sections and a number of cells in each section that each need to be a different custom cell, with different display requirements. I currently have a large if statement in cellForRowAtIndexPath, with each branch instantiating and returning the appropriate custom cell based on interrogating the indexPath's section and row properties. e.g. if (indexPath.section == 0 && indexPath.row == 0) { // instantiate and return cell A } else if (indexPath.section == 1 && indexPath.row == 2) { // instantiate and return cell B } //etc etc What is best practice for this scenario? A large if statement does the job, but is it the best implementation?

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  • Is there a case for parameterising using Abstract classes rather than Interfaces?

    - by Chris
    I'm currently developing a component based API that is heavily stateful. The top level components implement around a dozen interfaces each. The stock top-level components therefore sit ontop of a stack of Abstract implementations which in turn contain multiple mixin implementations and implement multiple mixin interfaces. So far, so good (I hope). The problem is that the base functionality is extremely complex to implement (1,000s of lines in 5 layers of base classes) and therefore I do not wish for component writers to implement the interfaces themselves but rather to extend my base classes (where all the boiler plate code is already written). If the API therefore accepts interfaces rather than references to the Abstract implementation that I wish for component writers to extends, then I have a risk that the implementer will not perform the validation that is both required and assumed by other areas of code. Therefore, my question is, is it sometimes valid to paramerise API methods using an abstract implementation reference rather than a reference to the interface(s) that it implements? Do you have an example of a well-designed API that uses this technique or am I trying to talk myself into bad-practice?

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  • what if i keep my class members are public?

    - by anish
    In c++ instance variables are private by default,in Python variables are public by default i have two questions regarding the same:- 1: why Python have all the members are public by default? 2: People say you should your member data should be private what if i make my data to be public? what are the disadvantages of this approch? why it is a bad design?

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  • jquery: How to deal with 'this' in ajax callbacks

    - by Svish
    I currently have code similar to this for a form: $('#some-form') .submit(function() { // Make sure we are not already busy if($(this).data('busy')) return false; $(this).data('busy', true); // Do post $.post("some/url", $(this).serialize(), function(data) { if(data.success) // Success is a boolean I set in the result on the server { // Deal with data } else { // Display error } $('#some-form') .removeData('busy'); }); return false; }); My issue is that I would like to somehow remove the need for knowing the form id in the post callback. In the end where I remove the busy data from the form, I'd like to somehow not have that hard coded. Is there any way I can do this? Is there a way I can hand whatever is in this to the post callback function? Since I know the id right now, I can get around it by doing what I have done, but I'd like to know how to not be dependant on knowing the id, since often I don't have an id. (For example if I have a link in each row in a table and all the rows have the same click handler.

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  • 'goto' usage

    - by Landon
    I've long been under the impression that 'goto' should never be used if possible. While perusing libavcodec (which is written in C) the other day, I noticed multiple uses of it. Is it ever advantageous to use 'goto' in a language that supports loops and functions? If so, why?

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  • Is there any difference between var name = function() {} & function name() {} in Javascript?

    - by Fletcher Moore
    Suppose we are inside a function and not in the global namespace. function someGlobalFunction() { var utilFunction1 = function() { } function utilFunction2 () { } utilFunction1(); utilFunction2(); } Are these synonymous? And do these functions completely cease to exist when someGlobalFunction returns? Should I prefer one or the other for readability or some other reason?

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