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  • How To Initialize Object Which May Be Used In Catch Clause?

    - by Onorio Catenacci
    I've seen this sort of pattern in code before: //pseudo C# code var exInfo = null; //Line A try { var p = SomeProperty; //Line B exInfo = new ExceptionMessage("The property was " + p); //Line C } catch(Exception ex) { exInfo.SomeOtherProperty = SomeOtherValue; //Line D } Usually the code is structured in this fashion because exInfo has to be visible outside of the try clause. The problem is that if an exception occurs on Line B, then exInfo will be null at Line D. The issue arises when something happens on Line B that must occur before exInfo is constructed. But if I set exInfo to a new Object at line A then memory may get leaked at Line C (due to "new"-ing the object there). Is there a better pattern for handling this sort of code? Is there a name for this sort of initialization pattern? By the way I know I could check for exInfo == null before line D but that seems a bit clumsy and I'm looking for a better approach.

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  • Mono is frequently used to say "Yes, .NET is cross-platform". How valid is that claim?

    - by Thorbjørn Ravn Andersen
    In What would you choose for your project between .NET and Java at this point in time ? I say that I would consider the "Will you always deploy to Windows?" the single most important decision to make up front in a new web project, and if the answer is "no", I would recommend Java instead of .NET. A very common counter-argument is that "If we ever want to run on Linux/OS X/Whatever, we'll just run Mono", which is a very compelling argument on the surface, but I don't agree for several reasons. OpenJDK and all the vendor supplied JVM's have passed the official Sun TCK ensuring things work correctly. I am not aware of Mono passing a Microsoft TCK. Mono trails the .NET releases. What .NET-level is currently fully supported? Does all GUI elements (WinForms?) work correctly in Mono? Businesses may not want to depend on Open Source frameworks as the official plan B. I am aware that with the new governance of Java by Oracle, the future is unsafe, but e.g. IBM provides JDK's for many platforms, including Linux. They are just not open sourced. So, under which circumstances is Mono a valid business strategy for .NET-applications?

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  • Mono is frequently used to say "Yes, .NET is cross-platform". How valid is that claim?

    - by Thorbjørn Ravn Andersen
    In What would you choose for your project between .NET and Java at this point in time? I say that I would consider the "Will you always deploy to Windows?" the single most important (EDIT: technical) decision to make up front in a new web project, and if the answer is "no", I would recommend Java instead of .NET. A very common counter-argument is that "If we ever want to run on Linux/OS X/Whatever, we'll just run Mono", which is a very compelling argument on the surface, but I don't agree for several reasons. OpenJDK and all the vendor supplied JVM's have passed the official Sun TCK ensuring things work correctly. I am not aware of Mono passing a Microsoft TCK. Mono trails the .NET releases. What .NET-level is currently fully supported? Does all GUI elements (WinForms?) work correctly in Mono? Businesses may not want to depend on Open Source frameworks as the official plan B. I am aware that with the new governance of Java by Oracle, the future is unsafe, but e.g. IBM provides JDK's for many platforms, including Linux. They are just not open sourced. So, under which circumstances is Mono a valid business strategy for .NET-applications? Edit: Mark H summarized it as: "If the claim is that "I have a windows application written in .NET, it should run on mono", then not, it's not a valid claim - but Mono has made efforts to make porting such applications simpler.".

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  • How can I make a universal construction more efficient?

    - by VF1
    A "universal construction" is a wrapper class for a sequential object that enables it to be linearized (a strong consistency condition for concurrent objects). For instance, here's an adapted wait-free construction, in Java, from [1], which presumes the existence of a wait-free queue that satisfies the interface WFQ (which only requires one-time consensus between threads) and assumes a Sequential interface: public interface WFQ<T> // "FIFO" iteration { int enqueue(T t); // returns the sequence number of t Iterable<T> iterateUntil(int max); // iterates until sequence max } public interface Sequential { // Apply an invocation (method + arguments) // and get a response (return value + state) Response apply(Invocation i); } public interface Factory<T> { T generate(); } // generate new default object public interface Universal extends Sequential {} public class SlowUniversal implements Universal { Factory<? extends Sequential> generator; WFQ<Invocation> wfq = new WFQ<Invocation>(); Universal(Factory<? extends Sequential> g) { generator = g; } public Response apply(Invocation i) { int max = wfq.enqueue(i); Sequential s = generator.generate(); for(Invocation invoc : wfq.iterateUntil(max)) s.apply(invoc); return s.apply(i); } } This implementation isn't very satisfying, however, since it presumes determinism of a Sequential and is really slow. I attempted to add memory recycling: public interface WFQD<T> extends WFQ<T> { T dequeue(int n); } // dequeues only when n is the tail, else assists other threads public interface CopyableSequential extends Sequential { CopyableSequential copy(); } public class RecyclingUniversal implements Universal { WFQD<CopyableSequential> wfqd = new WFQD<CopyableSequential>(); Universal(CopyableSequential init) { wfqd.enqueue(init); } public Response apply(Invocation i) { int max = wfqd.enqueue(i); CopyableSequential cs = null; int ctr = max; for(CopyableSequential csq : wfq.iterateUntil(max)) if(--max == 0) cs = csq.copy(); wfqd.dequeue(max); return cs.apply(i); } } Here are my specific questions regarding the extension: Does my implementation create a linearizable multi-threaded version of a CopyableSequential? Is it possible extend memory recycling without extending the interface (perhaps my new methods trivialize the problem)? My implementation only reduces memory when a thread returns, so can this be strengthened? [1] provided an implementation for WFQ<T>, not WFQD<T> - one does exist, though, correct? [1] Herlihy and Shavit, The Art of Multiprocessor Programming.

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  • Why is chunk size often a power of two?

    - by danijar
    There are many Minecraft clones out there and I am working on my own implementation. A principle of terrain rendering is tiling the whole world in fixed size chunks to reduce the effort of localized changes. In Minecraft the chunk size is 16 x 16 x 256 as far as I now. And in clones I also always saw chunk sizes of a power of the number 2. Is there any reason for that, maybe performance or memory related? I know that powers of 2 play a special role in binary computers but what has that to do with the chunk size?

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  • Internet of Things (IoT) Thanksgiving Special: Turkey Tweeter (Part 1)

    - by hinkmond
    It's time for the Internet of Things (ioT) Thanksgiving Special. This time we are going to work on a special Do-It-Yourself project to create an Internet of Things temperature probe to connect your Turkey Day turkey to the Internet by writing a Thanksgiving Day Java Embedded app for your Raspberry Pi which will send out tweets as it cooks in your oven. If you're vegetarian, don't worry, you can follow along and just run the simulation of the Turkey Tweeter, or better yet, try a tofu version of the Turkey Tweeter. Here is the parts list: 1 Vernier Go!Temp USB Temperature Probe 1 Uncooked Turkey 1 Raspberry Pi (not Pumpkin Pie) 1 Roll thermal reflective tape You can buy the Vernier Go!Temp USB Temperature Probe for $39 from here: http://www.vernier.com/products/sensors/temperature-sensors/go-temp/. And, you can get the thermal reflective tape from any auto parts store. (Don't tell them what you need it for. Say it's for rebuilding your V-8 engine in your Dodge Hemi. Avoids the need for a long explanation and sounds cooler...) The uncooked turkey can be found in your neighborhood grocery store. But, if you're making a vegetarian Tofurkey, you're on your own... The Java Embedded app will be the same, though (Java is vegan). So, grab all your parts and come back here for the next part of this project... Hinkmond

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  • What is an acceptable GC frequency for a SlimDX/Windows/.NET game?

    - by Rei Miyasaka
    I understand that the Windows GC is much better than the Xbox/WP7 GC, being that it's generational and multithreaded -- so I don't need to worry quite as much about avoiding memory allocation. SlimDX even has some unavoidable functions that generate some amount of garbage (specifically, MapSubresource creates DataBoxes), yet people don't seem to be too upset about it. I'd like to use some functional paradigms to write my code too, which also means creating objects like closures and monads. I know premature optimization isn't a good thing, but are there rules of thumb or metrics that I can follow to know whether I need to cut down on allocations? Is, say, one gen 0 GC per frame too much? One thing that has me stumped is object promotions. Gen 0 GCs will supposedly finish within a millisecond or two, but if I'm understanding correctly, it's the gen 1 and 2 promotions that start to hurt. I'm not too sure how I can predict/prevent these.

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  • Tomcat + Spring + CI workflow

    - by ex3v
    We're starting our very first project with Spring and java web stack. This project will be mainly about rewriting quite large ERP/CRM from Zend Framework to Java. Important factor in my question is that I come from php territory, where things (in terms of quality) tend to look different than in java world. Fatcs: there will be 2-3 developers, at least one of developers uses Windows, rest uses Linux, there is one remote linux-based machine, which should handle test and production instances, after struggling with buggy legacy code, we want to introduce good programming and development practices (CI, tests, clean code and so on) client: internal, frequent business logic changes, scrum, daily deployments What I want to achieve is good workflow on as many development stages as possible (coding - commiting - testing - deploying). The problem is that I've never done this before, so I don't know what are best practices to do this. What I have so far is: developers code locally, there is vagrant instance on every development machine, managed by puppet. It contains the same linux, jenkins and tomcat versions as production machine, while coding, developer deploys to vagrant machine, after local merge to test branch, jenkins on vagrant handles tests, when everything is fine, developer pushes commits and merges jenkins on remote machine pulls commit from test branch, runs tests and so on, if everything looks green, jenkins deploys to test tomcat instance Deployment to production is manual (altough it can be done using helping scripts) when business logic is tested by other divisions and everything looks fine to client. Now, the real question: does above make any sense? Things that I'm not sure about: Remote machine: won't there be any problems with two (or even three, as jenkins might need one) instances of same app on tomcat? Using vagrant to develop on php environment is just vise. Isn't this overkill while using Tomcat? I mean, is there higher probability that tomcat will act the same on every machine? Is there sense of having local jenkins on vagrant?

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  • How exactly to implement multiple threads in a game

    - by xerwin
    So I recently started learning Java, and having a interest in playing games as well as developing them, naturally I want to create game in Java. I have experience with games in C# and C++ but all of them were single-threaded simple games. But now, I learned how easy it is to make threads in Java, I want to take things to the next level. I started thinking about how would I actually implement threading in a game. I read couple of articles that say the same thing "Usually you have thread for rendering, for updating game logic, for AI, ..." but I haven't (or didn't look hard enough) found example of implementation. My idea how to make implementation is something like this (example for AI) public class AIThread implements Runnable{ private List<AI> ai; private Player player; /*...*/ public void run() { for (int i = 0; i < ai.size(); i++){ ai.get(i).update(player); } Thread.sleep(/* sleep until the next game "tick" */); } } I think this could work. If I also had a rendering and updating thread list of AI in both those threads, since I need to draw the AI and I need to calculate the logic between player and AI(But that could be moved to AIThread, but as an example) . Coming from C++ I'm used to do thing elegantly and efficiently, and this seems like neither of those. So what would be the correct way to handle this? Should I just keep multiple copies of resources in each thread or should I have the resources on one spot, declared with synchronized keyword? I'm afraid that could cause deadlocks, but I'm not yet qualified enough to know when a code will produce deadlock.

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  • 2D Image Creator for a video game

    - by user1276078
    I need to make a few images for an arcade video game I'm making in Java. As of right now, I have drawings that animate, but there are two problems. The drawings are horrible, and as a result, the game won't get enough attention. It's a pain to have to change each coordinate for the drawing, as the drawings are fairly complex. I'd like to use images. I feel they could solve my problem. They would look better than the drawings, and it would only have an x and a y coordinate, rather than the many coordinates I need for each drawing. So, in a sense, I have two questions. Would images actually help? Would they solve my 2 problems? I just want to clarify. How would I make these images. I don't think I can copy them off of the internet because I plan on publishing this game. So, is there any software where you can make your own images? (It has to be in an image type that Java can support. I'm working with java). It also, as stated by the header, needs to be a 2D image; not 3D

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  • Can the following Domain Entity contain logic for creating/deleting other entities?

    - by user702769
    a) As far as I understand it, in most cases Domain Model DM doesn't contain code for creating/deleting domain entities, but instead it is the job of layers ( ie service layer or UI layer ) on top of DM to create/delete domain entities? b) Domain entities are modelled after real world entities. Assuming particular real world entity being abstracted does have the functionality of creating/deleting other real world entities, then I assume the domain entity abstracting this real world entity could also contain logic for creating/deleting other entities? class RobotDestroyerCreator { ... void heavyThinking() { ... if(...) unitOfWork.registerDelete(robot); ... if(...) { var robotNew = new Robot(...); unitOfWork.registerNew(robotNew); { ... } } Thank you

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  • The idea of functionN in Scala / Functionaljava

    - by Luke Murphy
    From brain driven development It turns out, that every Function you’ll ever define in Scala, will become an instance of an Implementation which will feature a certain Function Trait. There is a whole bunch of that Function Traits, ranging from Function1 up to Function22. Since Functions are Objects in Scala and Scala is a statically typed language, it has to provide an appropriate type for every Function which comes with a different number of arguments. If you define a Function with two arguments, the compiler picks Function2 as the underlying type. Also, from Michael Froh's blog You need to make FunctionN classes for each number of parameters that you want? Yes, but you define the classes once and then you use them forever, or ideally they're already defined in a library (e.g. Functional Java defines classes F, F2, ..., F8, and the Scala standard library defines classes Function1, ..., Function22) So we have a list of function traits (Scala), and a list of interfaces (Functional-java) to enable us to have first class funtions. I am trying to understand exactly why this is the case. I know, in Java for example, when I write a method say, public int add(int a, int b){ return a + b; } That I cannot go ahead and write add(3,4,5); ( error would be something like : method add cannot be applied to give types ) We simply have to define an interface/trait for functions with different parameters, because of static typing?

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  • the requested resource is not available [closed]

    - by James Pj
    I have written a Java servlet program and run it through local Tomcat 7, But it was showing following error : HTTP Status 404 - /skypark/registration type Status report message /skypark/registration description The requested resource is not available. Apache Tomcat/7.0.33 I don't know what was the reason for it my Html page is <html> <head> <title> User registration </title> </head> <body> <form action="registration" method="post"> <center> <h2><b>Skypark User Registration</b></h2> <table border="0"> <tr><td> First Name </td><td> <input type="text" name="fname"/></br> </td></tr><tr><td> Last Name </td><td> <input type="text" name="lname"/></br> </td></tr><tr><td> UserName </td><td> <input type="text" name="uname"></br> </td></tr><tr><td> Enter Password </td><td> <input type="password" name="pass"></br> </td></tr><tr><td> Re-Type Password </td><td> <input type="password" name="pass1"></br> </td></tr><tr><td> Enter Email ID </td><td> <input type="email" name="email1"></br> </td></tr><tr><td> Phone Number </td><td> <input type="number" name="phone"> </td></tr><tr><td> Gender<br> </td></tr><tr><td> <input type="radio" name="gender" value="Male">Male</input></br> </td></tr><tr><td> <input type="radio" name="gender" value="Female">Female</input></br> </td></tr><tr><td> Enter Your Date of Birth<br> </td><td> <Table Border=0> <tr> <td> Date </td> <td>Month</td> <td>Year</td> </tr><tr> <td> <select name="date"> <option value="1">1</option> <option value="2">2</option> <option value="3">3</option> <option value="4">4</option> <option value="5">5</option> . . . have some code . . . </table> <input type="submit" value="Submit"></br> </center> </form> </body> </html> My servlet is : package skypark; import skypark.*; import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.sql.*; public class Registration extends HttpServlet { public static Connection prepareConnection()throws ClassNotFoundException,SQLException { String dcn="oracle.jdbc.driver.OracleDriver"; String url="jdbc:oracle:thin:@JamesPJ-PC:1521:skypark"; String usname="system"; String pass="tiger"; Class.forName(dcn); return DriverManager.getConnection(url,usname,pass); } public void doPost(HttpServletRequest req,HttpServletResponse resp)throws ServletException,IOException { resp.setContentType("text/html"); PrintWriter out=resp.getWriter(); try { String phone1,uname,fname,lname,dob,address,city,state,country,pin,email,password,gender,lang,qual,relegion,privacy,hobbies,fav; uname=req.getParameter("uname"); fname=req.getParameter("fname"); lname=req.getParameter("lname"); dob=req.getParameter("date"); address=req.getParameter("address"); city=req.getParameter("city"); state=req.getParameter("state"); country=req.getParameter("country"); pin=req.getParameter("pin"); email=req.getParameter("email1"); password=req.getParameter("password"); gender=req.getParameter("gender"); phone1=req.getParameter("phone"); lang=""; qual=""; relegion=""; privacy=""; hobbies=""; fav=""; int phone=Integer.parseInt(phone1); Connection con=prepareConnection(); String Query="Insert into regdetails values(?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)"; PreparedStatement ps=con.prepareStatement(Query); ps.setString(1,uname); ps.setString(2,fname); ps.setString(3,lname); ps.setString(4,dob); ps.setString(5,address); ps.setString(6,city); ps.setString(7,state); ps.setString(8,country); ps.setString(9,pin); ps.setString(10,lang); ps.setString(11,qual); ps.setString(12,relegion); ps.setString(13,privacy); ps.setString(14,hobbies); ps.setString(15,fav); ps.setString(16,gender); int c=ps.executeUpdate(); String query="insert into passmanager values(?,?,?,?)"; PreparedStatement ps1=con.prepareStatement(query); ps1.setString(1,uname); ps1.setString(2,password); ps1.setString(3,email); ps1.setInt(4,phone); int i=ps1.executeUpdate(); if(c==1||c==Statement.SUCCESS_NO_INFO && i==1||i==Statement.SUCCESS_NO_INFO) { out.println("<html><head><title>Login</title></head><body>"); out.println("<center><h2>Skypark.com</h2>"); out.println("<table border=0><tr>"); out.println("<td>UserName/E-Mail</td>"); out.println("<form action=login method=post"); out.println("<td><input type=text name=uname></td>"); out.println("</tr><tr><td>Password</td>"); out.println("<td><input type=password name=pass></td></tr></table>"); out.println("<input type=submit value=Login>"); out.println("</form></body></html>"); } else { out.println("<html><head><title>Error!</title></head><body>"); out.println("<center><b>Given details are incorrect</b>"); out.println(" Please try again</center></body></html>"); RequestDispatcher rd=req.getRequestDispatcher("registration.html"); rd.include(req,resp); return; } } catch(Exception e) { out.println("<html><head><title>Error!</title><body>"); out.println("<b><i>Unable to process try after some time</i></b>"); out.println("</body></html>"); RequestDispatcher rd=req.getRequestDispatcher("registration.html"); rd.include(req,resp); return; } out.flush(); out.close(); } } And the web.xml file is <?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0" metadata-complete="true"> <servlet> <servlet-name>reg</servlet-name> <servlet-class>skypark.Registration</servlet-class> </servlet> <servlet-mapping> <servlet-name>reg</servlet-name> <url-pattern>/registration</url-pattern> </servlet-mapping> This i kept in C:\Program Files\Apache Software Foundation\Tomcat 7.0\webapps\skypark\WEB_INF\web.xml and servlet class in C:\Program Files\Apache Software Foundation\Tomcat 7.0\webapps\skypark\WEB_INF\classes\skypark and registration.html in C:\Program Files\Apache Software Foundation\Tomcat 7.0\webapps\skypark\ if any mistake in this makes above error means please help me.Thanks in advance....

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  • Ubuntu gets slower by the day

    - by Doug
    Ive noticed that Ubuntu has been getting slower and slower to boot, launch programs, etc. I installed 12.04 about 4 months ago,now 12.10, running on a quad-core Q8300 Intel, 4GB Ram, and an 80GB WD IDE drive. For some reason (ever since 11.04), Ive noticed after installation, the speed is good. The longer I have the OS installed, every bootup gets slower and slower, launching programs get slower, frame rates change radically(onboard GF9400 gets anywhere from 60fps down to 12 in worst cases). I would think maybe the HD is the issue, however I installed 11.10 on a 160GB SATA, and the same thing occurred. Looking at system resources, I'm holding steady at 1GB memory usage (I have 4GB, but it's actually showing 3.6GB, dunno why), no swap usage, and using right around 4% on cpu currently. HD capacity is only 28% used. Has anyone else ran into this issue? I love Ubuntu to death, but using other distros other than Ubuntu, I dont have this problem.

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  • PAE on Ubuntu 12.04

    - by JamesStewy
    I am having trouble using PAE on Ubuntu 12.04 LTS 32bit. I recently upgraded from 4 to 8gb of RAM but PAE doesn't appear to have picked this up. When I run "grep --color=always -i PAE /proc/cpuinfo" I get pae in the list. When I run "dmidecode | grep Size | grep MB" Installed Size is 3825 but the Maximum Total Memory Size: 8192 MB. When I check the BIOS it says there is 8192 MB available and the computer fully supports I have followed everything I can find on the internet (including this https://help.ubuntu.com/community/EnablingPAE) and nothing is working. My Computer is a Toshiba Portege m750. It has an Intel Centrino Core 2 Duo processor. Bought in 2009 Thanks, JamesStewy

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  • Finding the best practice for a game simulating tool

    - by Tougheart
    I'm studying Java right now, and I'm thinking of this tool as my practice project. The game is "League of Legends" in case anyone knows it, I'm not actually simulating the game as in simulating game play, I'm just trying to create a tool that can compare different champions to each other based on their own abilities and items bought inside the game. The game basics are: Every player has a champion in a team of 5 players playing against another team. Each champion has a different set of abilities (usually 4) that s/he uses to do damage to opposing champions. Each champion gets stronger by buying different items, increasing the attack it deals or decreasing the damage received. What I want to do is to create a tool to be used outside the game enabling players to try out different builds for their champions and compare the figures against other champions they usually fight against. The goal is to enable players get a deeper understanding of the different item combinations (builds) that can be used during the games, instead of trying them out in real games which can be somehow very time consuming. What I'm stuck at is the best practice I should follow to make this possible using Java, I can't figure out which classes should inherit from which, should I make champions and items specs in the code or extracted from other files, specially that I'm talking about hundreds of items and champions to use in that tool. I'm self studying Java, and I don't have much practice at it, so I would really appreciate any broad guidelines regarding this, and sorry if my question doesn't fit here, I tried to follow the rules. English isn't my native language, so I'm really sorry if I wasn't clear enough, I would be more than happy to explain anything that's not understood.

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  • Can I copy large files faster without using the file cache?

    - by Veazer
    After adding the preload package, my applications seem to speed up but if I copy a large file, the file cache grows by more than double the size of the file. By transferring a single 3-4 GB virtualbox image or video file to an external drive, this huge cache seems to remove all the preloaded applications from memory, leading to increased load times and general performance drops. Is there a way to copy large, multi-gigabyte files without caching them (i.e. bypassing the file cache)? Or a way to whitelist or blacklist specific folders from being cached?

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  • HW resources for the device driver [closed]

    - by VladimirLenin
    Need to provide memory and IRQ resources to the Linux kernel in order to bring up the CAN controller. Have no idea how to get them. Below is the structure I need to fill in. This structure I have taken for example, this is for the Run-Time Clock, but I need for CAN controller. Both are on the same board, and there are constants for RT Clock (and all other devices), but not for my CAN chip. When looking at the subject chip driver's code (sp_probe() function), I see it needs the same type resources. struct resource tegra_rtc_resources[] = { [0] = { .start = ???, .end = ???, .flags = IORESOURCE_MEM, }, [1] = { .start = ???, .end = ???, .flags = IORESOURCE_IRQ, }, };

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  • How to identify web development benchmarking questions? [closed]

    - by GenericJam
    I am in my final year of college and I have to put forward some sort of thesis for my final year project. The project is a web based attendance system that I am building for the college. I have it about 70% complete in Java. After completing it in Java, the plan is for me to rewrite the server bit in Erlang and then release the bitter rivals in a head to head cage match. The idea being that there is some sort of grounds for comparison. There are a few hurdles along the way, such as me learning Erlang. I understand that a performance comparison like this isn't strictly scientific as there are many factors such as the programmer (myself); the hardware it runs on; etc... but it is meant to be a reasonable comparison of the merits of using Java vs. Erlang for web development. I need help in identifying what the relevant questions are that my project could address. Even though the project scope is fixed, I am trying to shoehorn in some worthwhile scientific inquiries.

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  • JSR 308 Moves Forward

    - by abuckley
    I am pleased to announce a number of recent milestones for JSR 308, Annotations on Java Types: Adoption of JCP 2.8 Thanks to the agreement of the Expert Group, JSR 308 operates under JCP 2.8 from September 2012. There is a publicly archived mailing list for EG members, and a companion list for anyone who wishes to follow EG traffic by email. There is also a "suggestion box" mailing list where anyone can send feedback to the E.G. directly. Feedback will be discussed on the main EG list. Co-spec lead Prof. Michael Ernst maintains an issue tracker and a document archive. Early-Access Builds of the Reference Implementation Oracle has published binaries for all platforms of JDK 8 with support for type annotations. Builds are generated from OpenJDK's type-annotations/type-annotations forest (notably the langtools repo). The forest is owned by the Type Annotations project. Integration with Enhanced Metadata On the enhanced metadata mailing list, Oracle has proposed support for repeating annotations in the Java language in Java SE 8. For completeness, it must be possible to repeat annotations on types, not only on declarations. The implementation of repeating annotations on declarations is already in the type-annotations/type-annotations forest (and hence in the early-access builds above) and work is underway to extend it to types.

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  • Lazy Processing of Streams

    - by Giorgio
    I have the following problem scenario: I have a text file and I have to read it and split it into lines. Some lines might need to be dropped (according to criteria that are not fixed). The lines that are not dropped must be parsed into some predefined records. Records that are not valid must be dropped. Duplicate records may exist and, in such a case, they are consecutive. If duplicate / multiple records exist, only one item should be kept. The remaining records should be grouped according to the value contained in one field; all records belonging to the same group appear one after another (e.g. AAAABBBBCCDEEEFF and so on). The records of each group should be numbered (1, 2, 3, 4, ...). For each group the numbering starts from 1. The records must then be saved somewhere / consumed in the same order as they were produced. I have to implement this in Java or C++. My first idea was to define functions / methods like: One method to get all the lines from the file. One method to filter out the unwanted lines. One method to parse the filtered lines into valid records. One method to remove duplicate records. One method to group records and number them. The problem is that the data I am going to read can be too big and might not fit into main memory: so I cannot just construct all these lists and apply my functions one after the other. On the other hand, I think I do not need to fit all the data in main memory at once because once a record has been consumed all its underlying data (basically the lines of text between the previous record and the current record, and the record itself) can be disposed of. With the little knowledge I have of Haskell I have immediately thought about some kind of lazy evaluation, in which instead of applying functions to lists that have been completely computed, I have different streams of data that are built on top of each other and, at each moment, only the needed portion of each stream is materialized in main memory. But I have to implement this in Java or C++. So my question is which design pattern or other technique can allow me to implement this lazy processing of streams in one of these languages.

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  • The better way to ask for input?

    - by Skippy
    I am wondering which is the best way to go with java code. I need to create a class with simple prompts for input.. I have tried using both classes and cannot work out the particular benefits for each. Is this because I am still in the early stages of programming or are there situations that will occur as it becomes more complex?? import java.util.Scanner; public class myClass { Scanner stdin = new Scanner(System.in); public String getInput(String prompt) { System.out.print(prompt); return stdin.nextLine(); } ... or import java.io.*; public class myClass { public static void main(String[] args) throws IOException { BufferedReader stdin = new BufferedReader (new InputStreamReader (System.in)); System.out.print("Input something: "); String name = stdin.readLine(); I know these examples are showing different methods within these classes, but thought this might serve well for the discussion. I'm really not sure which site is the best to ask this on.

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  • Why am I seeing so many instantiable classes without state?

    - by futlib
    I'm seeing a lot of instantiable classes in the C++ and Java world that don't have any state. I really can't figure out why people do that, they could just use a namespace with free functions in C++, or a class with a private constructor and only static methods in Java. The only benefit I can think of is that you don't have to change most of your code if you later decide that you want a different implementation in certain situations. But isn't that a case of premature design? It could be turned into a class later, when/if it becomes appropriate. Am I getting this wrong? Is it not OOP if I don't put everything into objects (i.e. instantiated classes)? Then why are there so many utility namespaces and classes in the standard libraries of C++ and Java? Update: I've certainly seen a lot examples of this in my previous jobs, but I'm struggling to find open source examples, so maybe it's not that common after all. Still, I'm wondering why people do it, and how common it is.

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  • ubuntu freezes daily

    - by alme1304
    I have been using ubuntu daily for about 2 weeks now. I really like it but I have noticed that it freezes daily when I have things like chromium and firefox open or when I start watching videos. I realize these might be memory intensive apps/actions but I doubt that with my comps specs they would cause it to freeze. When I installed ubuntu, I remember that it warned me about installing it in a ext2 partition and not in a ext4 one. Could that be the issue? and is there a way to fix it without reinstalling? edit: specs are, 1.9gb ram & Intel® Core™2 CPU 6400 @ 2.13GHz × 2; ubuntu 12.04x64

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  • Separate update and render

    - by NSAddict
    I'm programming a simple Snake in Java. I'm a complete newbie when it comes to Java and Game Developing, so please bear with me ;) Until now, I have been using a UI thread, as well as a update-thread. The update thread just set the position, set the GameObjects, and so on. I didn't think much of concurrency, but now I've come to a problem. I wanted to modify the ArrayList<GameObject>, but it throws a java.util.ConcurrentModificationException. With a little research I found out that this happens because the two threads are trying to access the variables at the same time. But I didn't really find a way to prevent this. I thought about copying the array and swapping them out when the rendering is finished, but I would have to deep-copy them, which isn't really the best solution in my opinion. It probably eats up more CPU resources than a single-threaded game. Are there any other ways to prevent this? Thanks a lot for your help!

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