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  • JAR files, don't they just bloat and slow Java down?

    - by Josamoto
    Okay, the question might seem dumb, but I'm asking it anyways. After struggling for hours to get a Spring + BlazeDS project up and running, I discovered that I was having problems with my project as a result of not including the right dependencies for Spring etc. There were .jars missing from my WEB-INF/lib folder, yes, silly me. After a while, I managed to get all the .jar files where they belong, and it comes at a whopping 12.5MB at that, and there's more than 30 of them! Which concerns me, but it probably and hopefully shouldn't be concerned. How does Java operate in terms of these JAR files, they do take up quite a bit of hard drive space, taking into account that it's compressed and compiled source code. So that can really quickly populate a lot of RAM and in an instant. My questions are: Does Java load an entire .jar file into memory when say for instance a class in that .jar is instantiated? What about stuff that's in the .jar that never gets used. Do .jars get cached somehow, for optimized application performance? When a single .jar is loaded, I understand that the thing sits in memory and is available across multiple HTTP requests (i.e. for the lifetime of the server instance running), unlike PHP where objects are created on the fly with each request, is this assumption correct? When using Spring, I'm thinking, I had to include all those fiddly .jars, wouldn't I just be better off just using native Java, with say at least and ORM solution like Hibernate? So far, Spring just took extra time configuring, extra hard drive space, extra memory, cpu consumption, so I'm concerned that the framework is going to cost too much application performance just to get for example, IoC implemented with my BlazeDS server. There still has to come ORM, a unit testing framework and bits and pieces here and there. It's just so easy to bloat up a project quickly and irresponsibly easily. Where do I draw the line?

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  • What should I use to increase performance. View/Query/Temporary Table

    - by Shantanu Gupta
    I want to know the performance of using Views, Temp Tables and Direct Queries Usage in a Stored Procedure. I have a table that gets created every time when a trigger gets fired. I know this trigger will be fired very rare and only once at the time of setup. Now I have to use that created table from triggers at many places for fetching data and I confirms it that no one make any changes in that table. i.e ReadOnly Table. I have to use this tables data along with multiple tables to join and fetch result for further queries say select * from triggertable By Using temp table select ... into #tx from triggertable join t2 join t3 and so on select a,b, c from #tx --do something select d,e,f from #tx ---do somethign --and so on --around 6-7 queries in a row in a stored procedure. By Using Views create view viewname ( select ... from triggertable join t2 join t3 and so on ) select a,b, c from viewname --do something select d,e,f from viewname ---do somethign --and so on --around 6-7 queries in a row in a stored procedure. This View can be used in other places as well. So I will be creating at database rather than at sp By Using Direct Query select a,b, c from select ... into #tx from triggertable join t2 join t3 join ... --do something select a,b, c from select ... into #tx from triggertable join t2 join t3 join ... --do something . . --and so on --around 6-7 queries in a row in a stored procedure. Now I can create a view/temporary table/ directly query usage in all upcoming queries. What would be the best to use in this case.

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  • Check if web form values has changed. Best practice

    - by Andrew Florko
    Hello everybody, I have multi-step form and user can navigate to any page to modify or add information. There is a menu that shows progress and steps user completed. This menu allows to navigate to any step user completed or going to complete. Inspite of big button "Save and Continue" some users click this menu to navigate further. I have to check - if values have changed in a form and ask: "Save changes? Yes/No". What is the best way (with minimum code) you suggest me to check if form values have changed. Thank you in advance!

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  • Creating an interface and swappable implementations in python

    - by Blankman
    Hi, Would it be possible to create a class interface in python and various implementations of the interface. Example: I want to create a class for pop3 access (and all methods etc.). If I go with a commercial component, I want to wrap it to adhere to a contract. In the future, if I want to use another component or code my own, I want to be able to swap things out and not have things very tightly coupled. Possible? I'm new to python.

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  • Pattern for database-wrapper in java

    - by Space_C0wb0y
    I am currently writing a java-class that wraps an SQLite database. This class has two ways to be instantiated: Open an existing database. Create a new database. This is what I cam up with: public class SQLiteDatabaseWrapper { public static SQLiteDatabaseWrapper openExisting(File PathToDB) { return new SQLiteDatabaseWrapper(PathToDB); } public static SQLiteDatabaseWrapper createNew(File PathToDB) { CreateAndInitializeNewDatabase(PathToDB); return new SQLiteDatabaseWrapper(PathToDB); } private SQLiteDatabaseWrapper(File PathToDB) { // Open connection and setup wrapper } } Is this the way to go in Java, or is there any other best practice for this situation?

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  • best practice when referring to a program's name in C

    - by guest
    what is considered best practice when referring to a program's name? i've seen #define PROGRAM_NAME "myprog" printf("this is %s\n", PROGRAM_NAME); as well as printf("this is %s\n", argv[0]); i know, that the second approach will give me ./myprog rather than myprog when the program is not called from $PATH and that the first approach will guarantee consistence regarding the program's name. but is there anything else, that makes one approach superior to the other?

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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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  • One class per file rule in .NET?

    - by Joan Venge
    I follow this rule but some of my colleagues disagree with it and argue that if a class is smaller it can be left in the same file with other class(es). Another argument I hear all the time is "Even Microsoft don't do this, so why should we?" What's the general consensus on this? Are there cases where this should be avoided?

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  • Getting up to speed on modern architecture

    - by Matt Thrower
    Hi, I don't have any formal qualifications in computer science, rather I taught myself classic ASP back in the days of the dotcom boom and managed to get myself a job and my career developed from there. I was a confident and, I think, pretty good programmer in ASP 3 but as others have observed one of the problems with classic ASP was that it did a very good job of hiding the nitty-gritty of http so you could become quite competent as a programmer on the basis of relatively poor understanding of the technology you were working with. When I changed on to .NET at first I treated it like classic ASP, developing stand-alone applications as individual websites simply because I didn't know any better at the time. I moved jobs at this point and spent the next several years working on a single site whose architecture relied heavily on custom objects: in other words I gained a lot of experience working with .NET as a middle-tier development tool using a quite old-fashioned approach to OO design along the lines of the classic "car" class example that's so often used to teach OO. Breaking down programs into blocks of functionality and basing your classes and methods around that. Although we worked under an Agile approach to manage the work the whole setup was classic client/server stuff. That suited me and I gradually got to grips with .NET and started using it far more in the manner that it should be, and I began to see the power inherent in the technology and precisely why it was so much better than good old ASP 3. In my latest job I have found myself suddenly dropped in at the deep end with two quite young, skilled and very cutting-edge programmers. They've built a site architecture which is modelling along a lot of stuff which is new to me and which, in truth I'm having a lot of trouble understanding. The application is built on a cloud computing model with multi-tenancy and the architecture is all loosely coupled using a lot of interfaces, factories and the like. They use nHibernate a lot too. Shortly after I joined, both these guys left and I'm now supposedly the senior developer on a system whose technology and architecture I don't really understand and I have no-one to ask questions of. Except you, the internet. Frankly I feel like I've been pitched in at the deep end and I'm sinking. I'm not sure if this is because I lack the educational background to understand this stuff, if I'm simply not mathematically minded enough for modern computing (my maths was never great - my approach to design is often to simply debug until it works, then refactor until it looks neat), or whether I've simply been presented with too much of too radical a nature at once. But the only way to find out which it is is to try and learn it. So can anyone suggest some good places to start? Good books, tutorials or blogs? I've found a lot of internet material simply presupposes a level of understanding that I just don't have. Your advice is much appreciated. Help a middle-aged, stuck in the mud developer get enthusastic again! Please!

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  • Technical non-terminating condition in a loop

    - by Snarfblam
    Most of us know that a loop should not have a non-terminating condition. For example, this C# loop has a non-terminating condition: any even value of i. This is an obvious logic error. void CountByTwosStartingAt(byte i) { // If i is even, it never exceeds 254 for(; i < 255; i += 2) { Console.WriteLine(i); } } Sometimes there are edge cases that are extremely unlikeley, but technically constitute non-exiting conditions (stack overflows and out-of-memory errors aside). Suppose you have a function that counts the number of sequential zeros in a stream: int CountZeros(Stream s) { int total = 0; while(s.ReadByte() == 0) total++; return total; } Now, suppose you feed it this thing: class InfiniteEmptyStream:Stream { // ... Other members ... public override int Read(byte[] buffer, int offset, int count) { Array.Clear(buffer, offset, count); // Output zeros return count; // Never returns -1 (end of stream) } } Or more realistically, maybe a stream that returns data from external hardware, which in certain cases might return lots of zeros (such as a game controller sitting on your desk). Either way we have an infinite loop. This particular non-terminating condition stands out, but sometimes they don't. A completely real-world example as in an app I'm writing. An endless stream of zeros will be deserialized into infinite "empty" objects (until the collection class or GC throws an exception because I've exceeded two billion items). But this would be a completely unexpected circumstance (considering my data source). How important is it to have absolutely no non-terminating conditions? How much does this affect "robustness?" Does it matter if they are only "theoretically" non-terminating (is it okay if an exception represents an implicit terminating condition)? Does it matter whether the app is commercial? If it is publicly distributed? Does it matter if the problematic code is in no way accessible through a public interface/API? Edit: One of the primary concerns I have is unforseen logic errors that can create the non-terminating condition. If, as a rule, you ensure there are no non-terminating conditions, you can identify or handle these logic errors more gracefully, but is it worth it? And when? This is a concern orthogonal to trust.

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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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  • Why is 'virtual' optional for overridden methods in derived classes?

    - by squelart
    When a method is declared as virtual in a class, its overrides in derived classes are automatically considered virtual as well, and the C++ language makes this keyword virtual optional in this case: class Base { virtual void f(); }; class Derived : public Base { void f(); // 'virtual' is optional but implied. }; My question is: What is the rationale for making virtual optional? I know that it is not absolutely necessary for the compiler to be told that, but I would think that developers would benefit if such a constraint was enforced by the compiler. E.g., sometimes when I read others' code I wonder if a method is virtual and I have to track down its superclasses to determine that. And some coding standards (Google) make it a 'must' to put the virtual keyword in all subclasses.

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  • Truth tables in code? How to structure state machine?

    - by HanClinto
    I have a (somewhat) large truth table / state machine that I need to implement in my code (embedded C). I anticipate the behavior specification of this state machine to change in the future, and so I'd like to keep this easily modifiable in the future. My truth table has 4 inputs and 4 outputs. I have it all in an Excel spreadsheet, and if I could just paste that into my code with a little formatting, that would be ideal. I was thinking I would like to access my truth table like so: u8 newState[] = decisionTable[input1][input2][input3][input4]; And then I could access the output values with: setOutputPin( LINE_0, newState[0] ); setOutputPin( LINE_1, newState[1] ); setOutputPin( LINE_2, newState[2] ); setOutputPin( LINE_3, newState[3] ); But in order to get that, it looks like I would have to do a fairly confusing table like so: static u8 decisionTable[][][][][] = {{{{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }}, {{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }}}, {{{ 0, 0, 1, 1 }, { 0, 1, 1, 1 }}, {{ 0, 1, 0, 1 }, { 1, 1, 1, 1 }}}}, {{{{ 0, 1, 0, 1 }, { 1, 1, 1, 1 }}, {{ 0, 1, 0, 1 }, { 1, 1, 1, 1 }}}, {{{ 0, 1, 1, 1 }, { 0, 1, 1, 1 }}, {{ 0, 1, 0, 1 }, { 1, 1, 1, 1 }}}}; Those nested brackets can be somewhat confusing -- does anyone have a better idea for how I can keep a pretty looking table in my code? Thanks! Edit based on HUAGHAGUAH's answer: Using an amalgamation of everyone's input (thanks -- I wish I could "accept" 3 or 4 of these answers), I think I'm going to try it as a two dimensional array. I'll index into my array using a small bit-shifting macro: #define SM_INPUTS( in0, in1, in2, in3 ) ((in0 << 0) | (in1 << 1) | (in2 << 2) | (in3 << 3)) And that will let my truth table array look like this: static u8 decisionTable[][] = { { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 1, 1 }, { 0, 1, 1, 1 }, { 0, 1, 0, 1 }, { 1, 1, 1, 1 }, { 0, 1, 0, 1 }, { 1, 1, 1, 1 }, { 0, 1, 0, 1 }, { 1, 1, 1, 1 }, { 0, 1, 1, 1 }, { 0, 1, 1, 1 }, { 0, 1, 0, 1 }, { 1, 1, 1, 1 }}; And I can then access my truth table like so: decisionTable[ SM_INPUTS( line1, line2, line3, line4 ) ] I'll give that a shot and see how it works out. I'll also be replacing the 0's and 1's with more helpful #defines that express what each state means, along with /**/ comments that explain the inputs for each line of outputs. Thanks for the help, everyone!

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  • What are the constraints on Cocoa Framework version numbers?

    - by Joe
    We're distributing a Cocoa framework with regular updates. We'll be updating the version numbers with each release. The Apple documentation appears to suggest that version numbers should be consecutive incrementing integers. We are distributing output in several formats, and the framework is only one of them. We would rather not have to maintain a separate numbering system just for our frameworks. We don't really care about the precise format of the version numbers of the framework, so long as they change whenever the product changes, and behave in a correct and expected manner. I'm looking for a sensible and correct way of avoiding having to run a separate version number counter. One suggestion is that for product version 12.34.56 we could simply remove the dots and say the framework version is 123456. Is there a constraint on the type of number that can be represented (uint? long?) Does it have to be a number? Could it be a string? Do the numbers have to be consecutive? Is there a standard way of doing things in this situation?

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  • Best ways to reuse Java methods

    - by carillonator
    I'm learning Java and OOP, and have been doing the problems at Project Euler for practice (awesome site btw). I find myself doing many of the same things over and over, like: checking if an integer is prime/generating primes generating the Fibonacci series checking if a number is a palindrome What is the best way to store and call these methods? Should I write a utility class and then import it? If so, do I import a .class file or the .java source? I'm working from a plain text editor and the Mac terminal. Thanks!

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  • How to handle too many files in Qt

    - by mree
    I'm not sure how to ask this, but here goes the question: I'm migrating from J2SE to Qt. After creating some small applications in Qt, I noticed that I've created way too many files compared to what I would've create if I was developing in Java (I use Netbeans). For an example, for a GUI to Orders, I'd have to create Main Order Search Window Edit Order Dialog Manage Order Dialog Maybe some other dialogs... For Java, I don't have to create a new file for every new Dialog, the Dialog will be created in the JFrame class itself. So, I will only be seeing 1 file for Orders which has other Dialogs in it. However, in Qt, I'd have to create 1 ui file, 1 header file, 1 cpp file for each of the Dialog (I know I can just put the cpp in the header, but it's easier to view codes in seperate files). So, in the end, I might end up with 3 (if there are 3 dialogs) x3 files = 9 files for the GUI in Qt, compared to Java which is only 1 file. I do know that I can create a GUI by coding it manually. But it seems easy on small GUIs but not some on complicated GUIs with lots of inputs, tabs and etc. So, is there any suggestion on how to minimize the file created in Qt?

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  • Could this be considered a well-written PHP5 class?

    - by Ben Dauphinee
    I have been learning OOP principals on my own for a while, and taken a few cracks at writing classes. What I really need to know now is if I am actually using what I have learned correctly, or if I could improve as far as OOP is concerned. I have chopped a massive portion of code out of a class that I have been working on for a while now, and pasted it here. To all you skilled and knowledgeable programmers here I ask: Am I doing it wrong? class acl extends genericAPI{ // -- Copied from genericAPI class protected final function sanityCheck($what, $check, $vars){ switch($check){ case 'set': if(isset($vars[$what])){return(1);}else{return(0);} break; } } // --------------------------------- protected $db = null; protected $dataQuery = null; public function __construct(Zend_Db_Adapter_Abstract $db, $config = array()){ $this->db = $db; if(!empty($config)){$this->config = $config;} } protected function _buildQuery($selectType = null, $vars = array()){ // Removed switches for simplicity sake $this->dataQuery = $this->db->select( )->from( $this->config['table_users'], array('tf' => '(CASE WHEN count(*) > 0 THEN 1 ELSE 0 END)') )->where( $this->config['uidcol'] . ' = ?', $vars['uid'] ); } protected function _sanityRun_acl($sanitycheck, &$vars){ switch($sanitycheck){ case 'uid_set': if(!$this->sanityCheck('uid', 'set', $vars)){ throw new Exception(ERR_ACL_NOUID); } $vars['uid'] = settype($vars['uid'], 'integer'); break; } } private function user($action = null, $vars = array()){ switch($action){ case 'exists': $this->_sanityRun_acl('uid_set', $vars); $this->_buildQuery('user_exists_idcheck', $vars); return($this->db->fetchOne($this->dataQuery->__toString())); break; } } public function user_exists($uid){ return($this->user('exists', array('uid' => $uid))); } } $return = $acl_test->user_exists(1);

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  • Best practice for near reuse of model components?

    - by Chris Knight
    I have a requirement to use a Fund model in my code. It will contain a fund name and fund code. In the interest of reuse I've poked around the package containing the other models used and found an existing Fund model. However the issue here is that, in addition to fund name and code, it also contains an amount. Amount isn't directly relevant in my context. So, do I: 1) Use the existing Fund model as is, ignoring the setters/getters for fund amount. 2) Put a FundDescription interface onto the existing Fund model for accessing only the information I'm interested in. 3) Make a FundDescription base class from which the existing Fund model could now extend 4) Create a whole new seperate model since the two are slightly contextually different

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  • Manipulate data in the DB query or in the code

    - by DrDro
    How do you decide on which side you perform your data manipulation when you can either do it in the code or in the query ? When you need to display a date in a specific format for example. Do you retrieve the desired format directly in the sql query or you retrieve the date then format it through the code ? What helps you to decide : performance, best practice, preference in SQL vs the code language, complexity of the task... ?

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  • Is it good practice to initialize array in C/C++?

    - by sand
    I recently encountered a case where I need to compare two files (golden and expected) for verification of test results and even though the data written to both the files were same, the files does not match. On further investigation, I found that there is a structure which contains some integers and a char array of 64 bytes, and not all the bytes of char array were getting used in most of the cases and unused fields from the array contain random data and that was causing the mismatch. This brought me ask the question whether it is good practice to initialize the array in C/C++ as well, as it is done in Java?

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  • What the reasons for/against returning 0 from main in ISO C++?

    - by Maulrus
    I know that the C++ standard says that return 0 is inserted at the end of main() if no return statement is given; however, I often see recently-written, standard-conforming C++ code that explicitly returns 0 at the end of main(). For what reasons would somebody want to explicitly return 0 if it's automatically done by the compiler?

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  • C++ Singleton design pattern.

    - by Artem Barger
    Recently I've bumped into realization/implementation of Singleton design pattern for C++. It has looked in the following way (I have adopted it from real life example): // a lot of methods is omitted here class Singleton { public: static Singleton* getInstance( ); ~Singleton( ); private: Singleton( ); static Singleton* instance; }; From this declaration I can deduce that instance field is initiated on the heap, that means there is a memory allocation. That is completely unclear for me is when does exactly memory is going to be deallocated? Or there is a bug and memory leak? It seems like there is a problem in implementation. PS. And main question how to implement it in the right way?

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