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  • Java and Different Types of Stacks

    - by Rarge
    Currently the only stack I know anything about is Vector, I normally use this in place of an array but I understand that there is other types of stacks and they all suit different jobs. The project I am currently working on requires me to be inserting objects in a certain position inside a stack, not always the front of the stack and I am under the impression that a Vector may not be the best class for this job. Could somebody please give me a brief description of the other types of stacks available to me with the Java language and their advantages and disadvantages? Are these names homogeneous? E.g. Are they only used in the Java language or are they used as general terms in Computer Science? Thank you

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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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  • 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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  • Detecting similar words among n text documents

    - by javanes
    Hi; I have n documents and want to find common words that are included in these documents. For example I want to say (n-3) documents include the word "web". Certainly I can do this by basic data structures but there maybe efficient algorithm or a way to handle same words with different suffix. Is there any algorithm for such purposes? I am unfamiliar with datamining world. In general manner is there a term used for efforts of finding similarities between different documents? If there is then I will make my research easily. Thanks.

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  • MySQL Prepared Statements vs Stored Procedures Performance

    - by amardilo
    Hi there, I have an old MySQL 4.1 database with a table that has a few millions rows and an old Java application that connects to this database and returns several thousand rows from this this table on a frequent basis via a simple SQL query (i.e. SELECT * FROM people WHERE first_name = 'Bob'. I think the Java application uses client side prepared statements but was looking at switching this to the server, and in the example mentioned the value for first_name will vary depending on what the user enters). I would like to speed up performance on the select query and was wondering if I should switch to Prepared Statements or Stored Procedures. Is there a general rule of thumb of what is quicker/less resource intensive (or if a combination of both is better)

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  • Can the lock function be used to implement thread-safe enumeration?

    - by Daniel
    I'm working on a thread-safe collection that uses Dictionary as a backing store. In C# you can do the following: private IEnumerable<KeyValuePair<K, V>> Enumerate() { if (_synchronize) { lock (_locker) { foreach (var entry in _dict) yield return entry; } } else { foreach (var entry in _dict) yield return entry; } } The only way I've found to do this in F# is using Monitor, e.g.: let enumerate() = if synchronize then seq { System.Threading.Monitor.Enter(locker) try for entry in dict -> entry finally System.Threading.Monitor.Exit(locker) } else seq { for entry in dict -> entry } Can this be done using the lock function? Or, is there a better way to do this in general? I don't think returning a copy of the collection for iteration will work because I need absolute synchronization.

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  • Is there a good collection library for C-language?

    - by matti
    We have to maintain and even develop C-code of our legacy system. Is there good collection library that would support Java/C# (new versions) style collections. Hashtable, HashSet, etc. Of course without objects, but with structs. The HashTable key limitations to "strings" and ints is not a problem. It wouldn't be bad if it's free even for commercial use. I'm back to C from C# and I must say i'm depressed using our own libraries and the language in general. We're using VS2005 and MS C-compiler if that has nothing to do with anything. Thanks & BR -Matti

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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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  • variable being weirdly deleted

    - by calccrypto
    im having a weird problem with one variable: its not being recognized but its still printing. i would post my code, but it is massive. the basic idea is: # pseudocode def function(stuff): <do stuff> # These are the only 2 conditions if tag == 3: pka = <a string> if tag == 4: pka = <a string> print pka # (1) print pka # (2) <do stuff not modifying pka> print pka # (3) if pka == 'RSA': <do stuff> elif pka == 'DSA': <do stuff> my code will error at (2). however, it will print out (1), (2), and (3), all of which are the same. is there any general explanation of why this is happening? if my code is really needed, i will post it, but otherwise, i would rather not due to its size update: now the code will error at the if statement after (3), saying UnboundLocalError: local variable 'pka' referenced before assignment even though (1),(2),(3) just printed

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  • Security of PHP script, embedded or otherwise

    - by typoknig
    Hi all, I am curious about the security of PHP on an HTML webpage where PHP code is embedded (a webpage that would exist on the server as "webpage.php") or on a PHP script that may be referenced by an HTML page (that is, a PHP script that is not actually part of a webpage that exists on the server as "something.php" and is referenced by "webpage.html"). Getting to the point, let us say that if the source code of my PHP script is known by anyone it would be a very big problem. I know that when you view the source of a PHP page in a browser the PHP script is not shown, but what if the PHP server failed and the HTML still loaded (is this even possible), would a user be able to see the PHP script? To be more general, is there ANY possible way that a user could access the source of a PHP script from a web browser, and if so, how do I prevent it?

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  • FlockDB - What is it? And best cases for it uses.

    - by Guru
    Just came across FlockDB graph database. Details at github /flockDB. Twitter claims it uses FlockDB for the following: Twitter runs FlockDB on a large cluster of machines. we use it to store social graphs (who follows whom, who blocks whom) and secondary indices at twitter. At first glance, setup and trying it doesn't look straight forward. Have anyone already used it / setup this? If so, please answer the following general queries. What kind of applications is it better suited for? (Twitter claims it is simple and very rough, it remains to see what it meant though) How is FlockDB better than other graph db / noSQL db. Have you setup FlockDB, used it for a application? Early advices any? Note: I am evaluating the FlockDB and other graph databases mainly for learning them. Perhaps, I will build an application for that.

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  • Secure password transmission over unencrypted tcp/ip

    - by academicRobot
    I'm in the designing stages of a custom tcp/ip protocol for mobile client-server communication. When not required (data is not sensitive), I'd like to avoid using SSL for overhead reasons (both in handshake latency and conserving cycles). My question is, what is the best practices way of transmitting authentication information over an unencrypted connection? Currently, I'm liking SRP or J-PAKE (they generate secure session tokens, are hash/salt friendly, and allow kicking into TLS when necessary), which I believe are both implemented in OpenSSL. However, I am a bit wary since I don't see many people using these algorithms for this purpose. Would also appreciate pointers to any materials discussing this topic in general, since I had trouble finding any.

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  • In CQRS (event-sourced), do you need a global sequence counter in the event store?

    - by Jon M
    In trying to get my head around CQRS (and DDD in general) I have come across situations when two events occur on different aggregates but the order of them has domain meaning. If so then they could happen so close together that a timestamp (as used by the sample implementations I have seen) cannot differentiate them, meaning the event store doesn't contain a 'complete' representation of the domain as there is ambiguity over the order in which events occurred. As an example, the domain could fire a CustomerCreatedEvent which applies to the Customer aggregate, and then a CustomerAssignedToAgent event on the Agent aggregate. The CustomerAssignedToAgent event doesn't make sense if it occurs before the CustomerCreatedEvent, but typically both of these might be fired as a result of one operation which makes it likely that the timestamps would effectively be the same. So am I just modelling things badly? Should there ever be a situation where the sequence of events across different aggregates is important? Or should you keep a global sequence number on your event store, so that you can identify the exact sequence in which events occurred?

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  • how to open Gmail View Message Activity?

    - by NickLai
    I want to write an application to List the Gmail message. In the list, if user click one of the message item, it shall link ot Gmail App to see more detial information. Currently I can read the Gmail db with Gmail.java. There are some problems while I want to open Gmail Activity. In general, we can open Activity with Action and parameters. But Gmail App has not release code base. We do not know what Action set to Gmail Activity and what parmeter shall we put the extras. I only know that the Activity of View detial Message is named "HtmlConversationActivity." And the Package is under "com.google.android.gm." please tell me how to open the View detial Message Activity in Gmail APP. thanks a lot.

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  • Is concatenating with an empty string to do a string conversion really that bad?

    - by polygenelubricants
    Let's say I have two char variables, and later on I want to concatenate them into a string. This is how I would do it: char c1, c2; // ... String s = "" + c1 + c2; I've seen people who say that the "" + "trick" is "ugly", etc, and that you should use String.valueOf or Character.toString instead. I prefer this construct because: I prefer using language feature instead of API call if possible In general, isn't the language usually more stable than the API? If language feature only hides API call, then even stronger reason to prefer it! More abstract! Hiding is good! I like that the c1 and c2 are visually on the same level String.valueOf(c1) + c2 suggests something is special about c1 It's shorter. Is there really a good argument why String.valueOf or Character.toString is preferrable to "" +? Trivia: in java.lang.AssertionError, the following line appears 7 times, each with a different type: this("" + detailMessage);

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  • Why Do Programmers Get So Invested in their Favorite Technologies?

    - by Pierreten
    I've noticed this culture surrounding Ruby where developers truly believe that they are somehow more gifted than developers of other languages, regardless of experience and talent (even when that isn't the case, I've met some extremely junior Ruby developers come up with some pretty basic constructs, and pass them off as some sort of revolutionary idea). The derision of strongly typed languages seems to be a common theme as well; regardless of its merits. Is there something particular to the Ruby syntax in general that is to account for this? Is there a sociological component to it?

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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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  • Good File Organization Suggestions for Developer

    - by Paul
    I am struggling a little with folder organization to organize the many projects that I work on. I work on OS X - right now I am using ~/Development/ as the root folder, and I have many types of projects. For example, I have my iPhone apps under ~/Development/Xcode I develop in many languages, from PHP, to Ruby, to Python, to Objective-C. So, for example, I might have a couple of open-source apps based on PHP where I am using the Zend framework. Some of these projects are for clients, others are tests/experiments when learning a new language or general experimenting. I am really interested in how other developers have organized code/projects and could pass along some advice to make it very easy to navigate through code/projects related to many languages and types of projects.

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  • Can functions like sin() be redefined, in Fortran, C or Java?

    - by EOL
    Can a mathematical function like sin() be redefined, in Fortran, C or Java code, while preserving the default behavior of other mathematical functions like cos()? Or can another function named sin() but that accepts different argument types be defined in addition to the built-in sin()? I am interested in general features of these languages (I am thinking of applications like the implementation of non-usual number algebras). I tried to define a sin() function in a Fortran 95 program, but the intrinsic sin() function was called instead… Is there a way around this? what about C and Java?

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  • Binding to object properties in C++

    - by Rich.Carpenter
    I've seen in WPF where you can bind control values to properties of other controls. How is that binding accomplished in C++? For example, if I have a class called Car and a guage control called RPM, how do I tie the value of RPM to the member variable Car.RPM, so that when Car.RPM changes, it is automatically (as in without a specific update call coded by me) reflected by the RPM control? General answers or directions to pertinent resources would be fine also, as I'm just beginning to dabble in C++ and haven't had much Google luck with this particular question.

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  • Do you use another language instead of english ?

    - by Luc M
    Duplicate Should identifiers and comments be always in English or in the native language of the application and developers? For people who are not native English speakers, which language do you use to declare variables, classes, etc. ? I had to continue a project from a Spanish guy. Everything was written in Spanish. Since this time, I have decided to use English identifiers ( variables, classes, file names) and write comments in french. Everything was in french before that. What are the general recommendations about that practice? Do you use English everywhere knowing that no English people will work on your project ? Edit : Here's a post from Jeff Atwood about this subject: The Ugly American Programmer

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  • What reasons are there to place member functions before member variables or vice/versa?

    - by Cory Klein
    Given a class, what reasoning is there for either of the two following code styles? Style A: class Foo { private: doWork(); int bar; } Style B: class Foo { private: int bar; doWork(); } For me, they are a tie. I like Style A because the member variables feel more fine-grained, and thus would appear past the more general member functions. However, I also like Style B, because the member variables seem to determine, in a OOP-style way, what the class is representing. Are there other things worth considering when choosing between these two styles?

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  • Getting a "summary" of a webpage

    - by MattiasK
    I have something of a a hairy problem, I'd like to generate a couple of paragraphs of "description" of a given url, normally the start of an article. The Meta description field is one way to go but it isn't always good or set properly. It's fair to say it's a bit problematic to accomplish this from the screenscraped HTML. I had a general idea that perhaps one could scan the HTML for the first "appropriate" segment but it's hard to say what that is, perhaps something like the first paragraph containing a certain amount of text... Anyone have any good ideas? :) It doesn't have to be foolproof

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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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  • Mac OS X: Best way to do runtime check for retina display?

    - by Todd Ditchendorf
    Given a Cocoa application which runs on Mac OS X 10.7 and later: What is the best way to check, at runtime, if your app is currently running on a Mac with at least one retina display attached? If checking for this sort of thing is just really wrong-headed, I fully welcome a well-reasoned explanation of why. But I'd still like to know :). It seems likely you could just do a check specifically for the new Mac Book Pro "Retina" hardware (the only Mac at this time which currently has a retina display), but ideally, I'd really prefer a more general/generic/future-proof way to check than this. Ideally, I'd like to know how to detect the retina display, not the specific Mac model which currently happens to ship with a retina display.

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