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• Preferred data-format for user-data in java applications?

  - by Frederik Wordenskjold

  I'm currently developing a desktop application in java, which stores user data such as bookmarks for ftp-servers. When deciding how to save these informations, I ended up using xml, simply because I like the way xpath works. I was thinking about json too, which seems more lightweight. What is your preferred way to store data in java desktop applications (in general) and why? What about java-persistence, does that have any advantages worth noting? And how much does the size of user data matter? Its not always possible to store data in a database (or preferable), and in my experience xml does not scale well. Let me know what you think!

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• C++: Why don't I need to check if references are invalid/null?

  - by jbu

  Hi all, Reading http://www.cprogramming.com/tutorial/references.html, it says: In general, references should always be valid because you must always initialize a reference. This means that barring some bizarre circumstances (see below), you can be certain that using a reference is just like using a plain old non-reference variable. You don't need to check to make sure that a reference isn't pointing to NULL, and you won't get bitten by an uninitialized reference that you forgot to allocate memory for. My question is how do I know that the object's memory hasn't been freed/deleted AFTER you've initialized the reference. What it comes down to is that I can't take this advice on faith and I need a better explanation. Can anyone shed some light? Thanks, jbu

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• What happens when a computer program runs?

  - by gaijinco

  I know the general theory but I can't fit in the details. I know that a program resides in the secondary memory of a computer. Once the program begins execution it is entirely copied to the RAM. Then the processor retrive a few instructions (it depends on the size of the bus) at a time, puts them in registers and executes them. I also know that a computer program uses two kinds of memory: stack and heap, which are also part of the primary memory of the computer. The stack is used for non-dynamic memory, and the heap for dynamic memory (for example, everything related to the new operator in C++) What I can't understand is how those two things connect. At what point is the stack used for the execution of the instructions? Instructions go from the RAM, to the stack, to the registers?

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• What's the most scalable way to handle somewhat large file uploads in a Python webapp?

  - by Jason Baker

  We have a web application that takes file uploads for some parts. The file uploads aren't terribly big (mostly word documents and such), but they're much larger than your typical web request and they tend to tie up our threaded servers (zope 2 servers running behind an Apache proxy). I'm mostly in the brainstorming phase right now and trying to figure out a general technique to use. Some ideas I have are: Using a python asynchronous server like tornado or diesel or gunicorn. Writing something in twisted to handle it. Just using nginx to handle the actual file uploads. It's surprisingly difficult to find information on which approach I should be taking. I'm sure there are plenty of details that would be needed to make an actual decision, but I'm more worried about figuring out how to make this decision than anything else. Can anyone give me some advice about how to proceed with this?

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• Choosing the right and learning assembler for compiler-writing

  - by X A

  I'm writing a compiler and I have gone through all the steps (tokenizing, parsing, syntax tree structures, etc.) that they show you in all the compiler books. (Please don't comment with the link to the "Resources for writing a compiler" question!). I have chosen to use NASM together with alink as my backend. Now my problem is: I just can't find any good resources for learning NASM and assembly in general. The wikibook (german) on x86 assembly is horrible. They don't even explain the code they write there, I currently can't even get simple things like adding 1 to 2 and outputting the result working. Where can I learn NASM x86 assembly?

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• The remote server returned an error: (407) Proxy Authentication Required

  - by chris

  I'm getting this error when I call a web service: "The remote server returned an error: (407) Proxy Authentication Required". I get the general idea and I can get the code to work by adding myProxy.Credentials= NetworkCredential("user", "password", "domain"); or by using DefaultCredentials in code. My problem is that the call to the web service works in production without this. It seems like there is a non code solution involving Machine.config, but what is it? At the moment I can't get to the production boxes machine.config file to see what that looks like. I tried updating my machine.config as follows, but I still get the 407 error.

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• How to issue SQL Server lock hints in WCF Entity Framework?

  - by TMN

  I'm just learning the WCF entity framework (and .net in general), and I'm running into a problem specifying lock hints in an embedded SQL query. I'm trying to specify a query that has lock hints in it (e.g., "SELECT * FROM xyz WITH(XLOCK, ROWLOCK)") and I keep getting errors from the runtime that the query syntax is not valid. The query works if I enter it directly into SQL Server. Is there some special syntax for lock hints when creating IQueryable result sets, or do I have to somehow mess with the transaction isolation level (probably not possible, as I need to specify different lock hints on a subquery within the main query).

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• ASP.NET 3.5 Stateless Session Managment and connection pooling?

  - by Norm

  I am designing an ASP.NET (3.5) web application that connects to a Rocket Software UniVerse database. I am in the planning stages right now and need some help in being pointed in the right direction. I am brand new to ASP and C#. I am shooting for a RESTful design and a MVC pattern. Rocket provides a .NET library called UniObjects.NET which handles everything for connecting and retrieving information from the database. What would be the best way to in general to log my users into the database, then use that session via connection pooling? I see that in 3.5 there is the ASP.NET Routing Infrastructure and that looks promising am I in the right direction on this? Also does C# support decorators like Python and Java?

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• Does introducing foreign keys to MySQL reduce performance

  - by Tam

  I'm building Ruby on Rails 2.3.5 app. By default, Ruby on Rails doesn't provide foreign key contraints so I have to do it manually. I was wondering if introducing foreign keys reduces query performance on the database side enough to make it not worth doing. Performance in this case is my first priority as I can check for data consistency with code. What is your recommendation in general? do you recommend using foreign keys? and how do you suggest I should measure this?

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• Detecting Visual Studio Smart-tags events

  - by devoured elysium

  Is it possible to detect with VSX when any (or a particular) smart tag event is happening? I mean, every time we rename a variable, for example, a smart tag is available that allows us to change it through a form. I'd like to know if I can access that "text is changing" event. I don't mean to have to check for myself if the text is being changed and such, I'd like to make use of VS event system (if there is one). I gave this example but I'd like to know the "general system" of how smart tags work with VSX. Thanks

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• In .net, how do I choose between a Decimal and a Double

  - by Ian Ringrose

  We were discussing this the other day at work and I wish there was a Stackoverflow question I would point people at so here goes.) What is the difference between a Double and a Decimal? When (in what cases) should you always use a Double? When (in what cases) should you always use a Decimal? What’s the diver factors to consider in cases that don’t fall into one of the two camps above? (There a lot of questions that overlap this question, but they tend to be asking what someone should do in a given case, not how to decide in the general case)

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• Console App Mouse-Click X Y Coordinate Detection/Comparison

  - by Bloodyaugust

  I have a game that I am working on in a C# console application, purely as practice before going on to better methods. As opposed to using something such as a Windows Forms App, which has button functionality built in, I am endeavoring to grab the cursor position (which I know how to do) and compare it to a number of area's inside a console application as defined by perhaps pixel location, but I also do not know if there is some sort of built in unit of space other than pixels (this last bit is the part I am unable to figure). P.S. I know this is in general terms, with no code already provided, but I do not feel that it is needed as all I am asking for is a brief explanation of how to grab X Y coordinates inside a console application, and stick them in int variables. Many Thanks in advance! :D

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• C++ Header Guard issues

  - by JP

  I am making a small C++ framework, which contains many .h and .cpp. I have created a general include which include all my .h file such as: framework.h #include "A.h" #include "B.h" #include "C.h" each .h header are protected with include guard such as #ifndef A_HEADER #define A_HEADER ... #endif The issues is, I would like to be able to include "framework.h" inside all the sub .h such as, but it cause lots of compiler error: #ifndef A_HEADER #define A_HEADER #include "framework.h" ... #endif If instead I use the real header file for each sub header, and the framework.h for what ever use my framework it works fine.. I would just like to include the main header inside all my sub .h so I dont need to include all the dependency everytime. Thanks :)

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• What's a good way to throw and handle events in PHP?

  - by techexpert

  Hi everyone, I am just trying to get a general idea about the event prcessing mechanism in PHP5 in as neat way as possible. First of all I understand that a PHP application is not exactly a persistent type, so the events may not make a lot of sense, but from the OO perspective it might be a very elegant way to "communicate" between the objects. So I am thinking that it would make sense to separate the events on the external events, such as $_POST & $_GET and the internal ones, i.e. function callbacks. As far as the external ones, is it a good idea to process the $_GETs and $_POSTs directly, or is it better to wrap them into an event of some sort? Also, in order to process the internal events, do you have to pass the reference to the event handler/dispatcher to each class so they know how to throw them? I was thinking to use the PEAR EventDispatcher to do the work, but I am open to other suggestions. Thank you!

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• Choosing between assembler and COBOL

  - by Azares Cob

  I have to rewrite and greatly modify parts of a legacy COBOL application. The COBOL source-code is available (around 100.000 lines of copy & pasted code mixed with GOTOs). Some more details on the system: It is a general management system controlling transactions, bank management, customer data and employees of the company I work for. The COBOL-powered database is about 4 Terabytes distributed over 50 old HDDs. (But messing around with them is the sysadmins job) They are using COBOL85 only. Now I have two options: Rewrite and refactor 50% of the old COBOL system, or use X86 assembly. Should I use X86 assembler or COBOL?

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• How do you make your Java application memory efficient?

  - by Boune

  How do you optimize the heap size usage of an application that has a lot (millions) of long-lived objects? (big cache, loading lots of records from a db) Use the right data type Avoid java.lang.String to represent other data types Avoid duplicated objects Use enums if the values are known in advance Use object pools String.intern() (good idea?) Load/keep only the objects you need I am looking for general programming or Java specific answers. No funky compiler switch. Edit: Optimize the memory representation of a POJO that can appear millions of times in the heap. Use cases Load a huge csv file in memory (converted into POJOs) Use hibernate to retrieve million of records from a database Resume of answers: Use flyweight pattern Copy on write Instead of loading 10M objects with 3 properties, is it more efficient to have 3 arrays (or other data structure) of size 10M? (Could be a pain to manipulate data but if you are really short on memory...)

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• How easy would it be to refactor a small JSP/Servlet/JDBC project to SpringMVC/Hibernate

  - by John

  With reference to this post, I am considering starting a new web-based Java project. Since I don't know Spring/Hibernate I was concerned if it's a bad plan to start learning them while creating a new project, especially since it will slow down the early development. One idea I had was to write a prototype using tech I do know, namely JSP/Servlets/JDBC, since I can get this running much quicker with my current knowledge. I could then throw the whole thing away and start over with Spring, etc, but I'd like to consider how easy it would be to refactor a smallish project from JSP/Servlets/JDB to SpringMVC/Hibernate? My DB could of course be re-used but what about other code... would I expect to save most of it plugged into an MVC framework, or is the paradigm shift big enough this would cause more trouble than it avoids? Please use the other question for more general advice on choosing technologies

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• Creating An Utilities Class?

  - by Soo

  Hello SO, I'm very new to OOP and am trying my hardest to keep things strictly class based, while using good coding priciples. I'm a fair ways into my project now and I have a lot of general use methods I want to put into an utilities class. Is there a best way to create an utilities class? public class Utilities { int test; public Utilites() { } public int sum(int number1, int number2) { test = number1+number2; } return test; } After creating this Utilities class, do I just create an Utilities object, and run the methods of my choosing? Do I have this Utilities class idea correct?

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• How can I ignore C comments when I process a C source file with Perl?

  - by YoDar

  I'm running a code that read files, do some parsing, but need to ignore all comments. There are good explanations how to conduct it, like the answer to How can I strip multiline C comments from a file using Perl? $/ = undef; $_ = <>; s#/\*[^*]*\*+([^/*][^*]*\*+)*/|("(\\.|[^"\\])*"|'(\\.|[^'\\])*'|.[^/"'\\]*)#defined $2 ? $2 : ""#gse; print; My first problem is that after run this line $/ = undef; my code doesn't work properly. Actually, I don't know what it does. But if I could turn it back after ignoring all comments it will be helpful. In general, What is the useful way to ignore all comments without changing the rest of the code?

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• How Two Programs Can Talk To Each Other In Java?

  - by Arnon

  My first time here... I want to ?reduce? the CPU usage/ROM usage/RAM usage - in general ?speaking?, all system resources that my App use - how doesn't? :) For this reason i want to split the preferences window from the rest of the application, and let the preferences window to run as ?independent? program. The preferences program ?should? write to a Property file(not a problem at all) and to send a "update signal" to the main program - which mean, to call the update method(that i wrote) that found in the Main class. How can i call the update method in the Main program from the preferences program? Or in the other hand... There is a way to build preferences window that take system resources just when it's appear? Is this approach - of separating programs and let them talk to each other(somehow) - is a right approach for speeding up my programs? tnx

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• How to use GWT on mobile devices?

  - by Chris

  hi I have a fairly large web application developed with GWT (and EJB). However on mobile devices (like windows mobile, black berry and such) the GWT start page remains simply white. I'm using GWT 1.6 and also tried 1.7 but nothing helps. It seems that the java script isn't executing and also isn't the noscript tag. Do you know how to make it working without rewriting the whole application in e.g. PHP?? I think it may be a general prob with GWT apps and not with my specific app. thx

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• sql insert statement with a lot of same where clause and one different where cluase

  - by william

  I m sry if the title is not clear. Here's my proble. I created a new table which will show total, average and maximum values. I have to insert the results into that table. That table will have only 4 rows. No Appointment, Appointment Early, Appointment Late and Appointment Punctual. So.. I have sth like.. insert into newTable select 'No Appointment' as 'Col1', avg statement, total statement, max statement from orgTable where (general conditions) and (unique condition to check NO APPOINTMENT); I have to do that same thing for another 3 rows.. where only the unique condition is different to check early, punctual or late.. So..the statement is super long. I wanna reduce the size.. How can I achieve that?

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• Optional parens in Ruby for method with uppercase start letter?

  - by RasmusKL

  I just started out using IronRuby (but the behaviour seems consistent when I tested it in plain Ruby) for a DSL in my .NET application - and as part of this I'm defining methods to be called from the DSL via define_method. However, I've run into an issue regarding optional parens when calling methods starting with an uppercase letter. Given the following program: class DemoClass define_method :test do puts "output from test" end define_method :Test do puts "output from Test" end def run puts "Calling 'test'" test() puts "Calling 'test'" test puts "Calling 'Test()'" Test() puts "Calling 'Test'" Test end end demo = DemoClass.new demo.run Running this code in a console (using plain ruby) yields the following output: ruby .\test.rb Calling 'test' output from test Calling 'test' output from test Calling 'Test()' output from Test Calling 'Test' ./test.rb:13:in `run': uninitialized constant DemoClass::Test (NameError) from ./test.rb:19:in `<main>' I realize that the Ruby convention is that constants start with an uppercase letter and that the general naming convention for methods in Ruby is lowercase. But the parens are really killing my DSL syntax at the moment. Is there any way around this issue?

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• Putting a simple if-then statement on one line

  - by Abizern

  I'm just getting into Python and I really like the terseness of the syntax. However; is there an easier way of writing an if-then statement so it fits on one line? For example; say I have the simple test: if count == N: count = 0 else: count = N + 1 is there a simpler way of writing this? I mean, in Objective-C I would write this as: count = count == N ? count = 0 : count = N + 1; Is there something similar for python? Edit I know that in this instance I can use count == count % N. I'm asking about the general syntax.

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• IOS SDK : first advices for beginners

  - by VdesmedT

  I too often answer the same kind of questions regarding basic topics like memory management, UITableView, Interface Orientation, MVC, etc... I understand very well that everyone starting with that SDK is too exited about getting its hand on it but a few reading would save them hours of debugging and the frustration that come along with the feeling that "We miss something here". I'd like experience users to share the few small articles, white papers, docs, book chapters that helps other save their time and avoid frustration. My first vote would be for : IOS Memory Management Guide View Controller Programming Guide Table View Guide And as a General recommendation, read the Overview section that come along with every class documention in the reference library, they contains most of what you need to know to avoid big traps !

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