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  • Best Persistence choice for J2EE-App with frequently changing Data Model

    - by Ben-G
    Whenever I develop a J2EE-Application, I at some point decide to switch from my dummy Persistence (Simply Using Lists and other Data Structures) to some Sort of Database Persistence. Mostly when I hope the Data Model is more or less complete. From this point on, changes to the data model become exhausting, but unluckily they occur rather often. I've used different Object-Relational-Mappers (iBatis, Hibernate) for my projects. They definitely reduce the pain coming with Data Model changes, but they anyway let me adjust code/configuration at 3 or 4 places for every single change. To me, that's cumbersome and error prone. I made a better experience with DB4O, which simply persists Java Objects as they are, but I believe it's performance does not scale for huge applications. Is there anyway to maintain performance while letting out all the ugly configuration work? I'm seeking a performant framework which really hides persistence from my code. Wish for thinking? Or am I missing out THE technology? Hope you can help.

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  • EL 3.0 Public Review - JSR 341 and Java EE 7 Moving Along

    - by arungupta
    Following closely on the lines of EL 3.0 Early Draft, the specification is now available for a Public Review. The JCP2 Process Document defines different stages of the specifications. This review period closes Jul 30, 2012. Some of the main goals of the JSR are to separate ELContext into parsing and evaluation contexts, adding operators like equality, string concatenation, etc, and integration with CDI. The section A.7 of the specification highlights the difference between Early Draft and Public Review. Download the Public Review and and follow the updates at el-spec.java.net. For more information about EL 3.0 (JSR 341), check out the JSR project on java.net. The archives of EG discussion are available at jsr341-experts and you can subscribe to the users@el-spec and other aliases on the Mailing Lists page.

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  • JavaOne - Java SE Embedded Booth - Digi - Home Health Hub (HHH)

    - by David Clack
    Hi All,  So another exciting platform we will have in the booth at JavaOne is the Digi  Home Health Hub (HHH) platform. http://www.digi.com/products/wireless-wired-embedded-solutions/single-board-computers/idigi-telehealth-application-kit#overview This is a Freescale reference design that has been built by Digi, the system is powered by a Freescale i.MX28 ARM SOC, what's really exciting me is it has every wireless protocol you could ever want on a single motherboard. Ethernet, 802.11b/g/n Wi-Fi, Bluetooth, ZigBee, configurable Sub-GHz radio, NFC plus USB, audio and LCD/touch screen option. I've been experimenting with lots of wireless capable healthcare products in the last few months, plus some Bluetooth Pulse / Oxy meters, we have been looking at how the actual healthcare wireless protocols work. Steve Popovich - Vice President, Digi Internationalwill be doing a talk at the Java Embedded @ JavaOne conference in the Hotel Nikko, right next door to the JavaOne show in the Hilton. If you are registered at JavaOne you can come over to the Java Embedded @ JavaOne for $100 Come see us in booth 5605 See you there Dave

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  • How to solve SocketException: Permission denied: connect

    - by luxinxian
    I recently encountered a problem getting a headache, need help... System consists of: Two subsystems, called A, B (each running on a standalone tomcat instance), currently running on the same machine. A invoke B's service via spring httpInvoker(http). B system also invoke other system's services via http. Symptoms: 1, the system starts to run normally after 10-15 days; 2, the system will run for a period of time after an exception: org.springframework.remoting.RemoteAccessException: Could not access HTTP invoker remote service at [http://xxx.xxx.xxx.xxx/remoting/call]; nested exception is java. net.SocketException: Permission denied: connect 3, when the exception occour, it continues, not only occasional .(it looks like some resources exhausted, but cpu rate < 5%, memory < 15%, network < 5%) 4, A, B when the system call fails, B system via http call to an external service also failed for the same exception. 5, closed two tomcat services, restart, and working properly. So repeatedly (step 1 - 5), has not found the root reason. Emvironment: windows 2008 R2 tomcat7.0.42 x86_64 oralce-jdk-1.7.0_40 Any ideas?

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  • JEE frameworks, a road map to learn? and should I learn them?

    - by vibhor
    Background Information I have been into programming since past 1 years professionally, my day to day work includes writing BIRT reports, designing and validating forms using JEE (struts/spring, hibernate). I don't have a comp Sci 4 year degree (Electronics), so I have very Limited experience in comp Sci. Question JEE frameworks (struts1/2, spring, hibernate etc) are hot nowadays, however java world have a tendency of building A4j, B4J... mayway4J kind of stuff (and I am tired of it). AFAIK, frameworks are nothing but bunch of XML config files and hundreds of classes built to cram (by developer). And sooner then later a new framework come into picture that says I am the best among all. So My Question is - 1.What will you do to learn a framework (many frameworks) considering that it can be obsolete till you'll be master in it (Learning frameworks can take significant amount of time)? 2.Considering early into your career, will you give a damn that how well someone knows framework (knowing frame work is important but still..) and why/how should I learn a framework knowing I have to (un)learn it in order to learn other one (plenty of of 4Js....)? I am just trying to get a big picture, that, if you're in place of me, what would be your learning/cramming strategy (Road map)? I am not intended to start a holy war between A versus B, (frameworks are more or less essential).

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  • Server-side Architecture for Online Game

    - by Draiken
    Hi, basically I have a game client that has communicate with a server for almost every action it takes, the game is in Java (using LWJGL) and right now I will start making the server. The base of the game is normally one client communicating with the server alone, but I will require later on for several clients to work together for some functionalities. I've already read how authentication server should be sepparated and I intend on doing it. The problem is I am completely inexperienced in this kind of server-side programming, all I've ever programmed were JSF web applications. I imagine I'll do socket connections for pretty much every game communication since HTML is very slow, but I still don't really know where to start on my server. I would appreciate reading material or guidelines on where to start, what architecture should the game server have and maybe some suggestions on frameworks that could help me getting the client-server communication. I've looked into JNAG but I have no experience with this kind of thing, so I can't really tell if it is a solid and good messaging layer. Any help is appreciated... Thanks !

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  • Where to store global enterprise properties?

    - by shylynx
    I'm faced with a crowd of java applications, which need different global enterprise wide properties for operation, for example: hostname of the central RDBMS, hostname and location of the central self-service portal, host location of central LDAP, host location of central mail server etc. Formally we build each application with a properties file, where all this properties are definied. But that's a very bad solution, because if the hostname of the mail server changes, we need to change the properties files for each application and deploy all applications again. Our idea is to centralize this properties, so that each application can ask for each property at runtime, for example: Idea: Put the properties file to an easy accessible file share. So if we need to change a property, each application uses the new properties. Idea: Put the properties to database. Main disadvantage: we need a dependency to database client libraries for each application. Idea: Put all applications into one big application server, that provides system properties for each application. Main disadvantage: needs deployment of each application to one application server. But that isn't a realistic scenario. Idea: Webservice that provides global enterprise wide properties. Main disadvantage: not very secure, because some properties are passwords or user credentials. What other alternatives are recommended? What is state of the art?

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  • program logic of printing the prime numbers

    - by Vignesh Vicky
    can any body help to understand this java program it just print prime n.o ,as you enter how many you want and it works good class PrimeNumbers { public static void main(String args[]) { int n, status = 1, num = 3; Scanner in = new Scanner(System.in); System.out.println("Enter the number of prime numbers you want"); n = in.nextInt(); if (n >= 1) { System.out.println("First "+n+" prime numbers are :-"); System.out.println(2); } for ( int count = 2 ; count <=n ; ) { for ( int j = 2 ; j <= Math.sqrt(num) ; j++ ) { if ( num%j == 0 ) { status = 0; break; } } if ( status != 0 ) { System.out.println(num); count++; } status = 1; num++; } } } i dont understand this for loop condition for ( int j = 2 ; j <= Math.sqrt(num) ; j++ ) why we are taking sqrt of num...which is 3....why we assumed it as 3?

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  • Continuous integration never results in build errors

    - by Jon
    Hi, I'm working with a variety of Java EE websites which use internal libraries we've developed. For each website, we only upgrade to new versions of our internal libraries as needed, and before committing we make sure that the site compiles fine. What this means is that when TeamCity does a build of one of our sites, the site compiles fine, but later when the site is updated to the latest version of internal libraries, there might be a compile error. Is there a good way to handle this? We're not using Maven yet; would using Maven mean that our websites could automatically use the latest version of internal libraries? Thanks. Clarification: What we sometimes run into is this: Project A depends on a library, and is currently using library version 1.0 Project B also depends on that library. I make changes to the library so that it is now version 1.5. Project B now uses 1.5. Project A and project B have both been built just fine by the CI server (TeamCity) Working on project A again, I update to 1.5 and discover that 1.5 has breaking changes in it. Is there a way for the CI server to discover these kinds of breaking changes?

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  • How can I install oracle-java7 from webupd8 ppa?

    - by Ahmed Zain El Dein
    I installed ppa:webupd8team/java and I get the following error Output from: sudo apt-get install oracle-java7-installer Reading package lists... Done Building dependency tree Reading state information... Done Suggested packages: binfmt-support visualvm ttf-baekmuk ttf-unfonts ttf-unfonts-core ttf-kochi-gothic ttf-sazanami-gothic ttf-kochi-mincho ttf-sazanami-mincho ttf-arphic-uming The following packages will be upgraded: oracle-java7-installer 1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. 1 not fully installed or removed. Need to get 0 B/16.0 kB of archives. After this operation, 64.5 kB of additional disk space will be used. Could not exec dpkg! E: Sub-process /usr/bin/dpkg returned an error code (100) i did afterwords those line of code trying to resolve the issue becuase it is not existed actually in the /usr/bin/dpkg there is no dpkg mkdir /tmp/dpkg cd /tmp/dpkg wget http://archive.ubuntu.com/ubuntu/pool/main/d/dpkg/dpkg_1.15.5.6ubuntu4_i386.deb ar x dpkg*.deb data.tar.gz tar xfvz data.tar.gz ./usr/bin/dpkg sudo cp ./usr/bin/dpkg /usr/bin/ sudo apt-get update sudo apt-get install --reinstall dpkg then i get this $ sudo apt-get install --reinstall dpkg Reading package lists... Done Building dependency tree Reading state information... Done 0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 6 not upgraded. 1 not fully installed or removed. Need to get 0 B/1,814 kB of archives. After this operation, 0 B of additional disk space will be used. dpkg: warning: 'dpkg-deb' not found on PATH. dpkg: 1 expected program(s) not found on PATH. NB: root's PATH should usually contain /usr/local/sbin, /usr/sbin and /sbin. E: Sub-process /usr/bin/dpkg returned an error code (2) How can I fix this?

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  • How do I make time?

    - by SystemNetworks
    I wanted to output a text for a certain amount of time. One way is to use threads. Are there any other ways? I can't use threads for slick2d. This is my code when I use threads for slick: package javagame; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.Image; import java.util.Random; import org.newdawn.slick.Input; import org.newdawn.slick.*; import org.newdawn.slick.state.*; import org.lwjgl.input.Mouse; public class thread1 implements Runnable { String showUp; int timeLeft; public thread1(String s) { s = showUp; } public void run(Graphics g) { try { g.drawString("%s is sleeping %d", 500, 500); Thread.sleep(timeLeft); g.drawString("%s is awake", 600,600); } catch(Exception e) { } } @Override public void run() { // TODO Auto-generated method stub run(); } } It auto generates a new run() And also when I call it to my main class it has stack overflow!

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  • New Java EE/GlassFish Testimonial

    - by reza_rahman
    As you may be aware, we have been making a concerted effort to ask successful Java EE/GlassFish adopters to come forward with their stories. A number of such stories were shared at this year's GlassFish Community event at JavaOne. In addition to Adam Bien's testimonial (which we posted earlier), another story that really stands out is the one from Stephan Janssen. Stephan is one of the main organizers of Devoxx and the webmaster of the popular Parleys e-learning platform. Parleys, which won the Duke's Choice award this year, runs on GlassFish as does the Devoxx CFP/registration website. Stephan's story is particularly interesting because he talks about his reasons and experience of moving from Tomcat to GlassFish and from Spring to Java EE. See what Stephan had to say here.

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  • Implmenting RLE into a tilemap or how to create a large 3D array?

    - by Smallbro
    Currently I've been using a 3D array for my tiles in a 2D world but the 3D side comes in when moving down into caves and whatnot. Now this is not memory efficient and I switched over to a 2D array and can now have much larger maps. The only issue I'm having now is that it seems that my tiles cannot occupy the same space as a tile on the same z level. My current structure means that each block has its own z variable. This is what it used to look like: map.blockData[x][y][z] = new Block(); however now it works like this map.blockData[x][y] = new Block(z); I'm not sure why but if I decide to use the same space on say the floor below it wont allow me to. Does anyone have any ideas on how I can add a z-axis to my 2D array? I'm using java but I reckon the concept carries across different languages. Edit: As Will posted, RLE sounds like the best method for achieving a fast 3D array. However I'm struggling to understand how I would even start to implement it? Would I create a 4D array the 4th being something which controls how many to skip? Or would the x-axis simply change altogether and have large gaps in between - for example [5][y][z] would skip 5 tiles? Is there something really obvious here which I am missing? The number of z levels I'm trying to have is around 66, it would be preferably that I can have up to or more than 1000 in x and y.

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  • Can't get sprite to rotate correctly?

    - by rphello101
    I'm attempting to play with graphics using Java/Slick 2d. I'm trying to get my sprite to rotate to wherever the mouse is on the screen and then move accordingly. I figured the best way to do this was to keep track of the angle the sprite is at since I have to multiply the cosine/sine of the angle by the move speed in order to get the sprite to go "forwards" even if it is, say, facing 45 degrees in quadrant 3. However, before I even worry about that, I'm having trouble even getting my sprite to rotate in the first place. Preliminary console tests showed that this code worked, but when applied to the sprite, it just kind twitches. Anyone know what's wrong? int mX = Mouse.getX(); int mY = HEIGHT - Mouse.getY(); int pX = sprite.x; int pY = sprite.y; int tempY, tempX; double mAng, pAng = sprite.angle; double angRotate=0; if(mX!=pX){ tempY=pY-mY; tempX=mX-pX; mAng = Math.toDegrees(Math.atan2(Math.abs((tempY)),Math.abs((tempX)))); if(mAng==0 && mX<=pX) mAng=180; } else{ if(mY>pY) mAng=270; else mAng=90; } //Calculations if(mX<pX&&mY<pY){ //If in Q2 mAng = 180-mAng; } if(mX<pX&&mY>pY){ //If in Q3 mAng = 180+mAng; } if(mX>pX&&mY>pY){ //If in Q4 mAng = 360-mAng; } angRotate = mAng-pAng; sprite.angle = mAng; sprite.image.setRotation((float)angRotate);

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  • Floodfill algorithm for GO

    - by user1048606
    The floodfill algorithm is used in the bucket tool in MS paint and photoshop, but it can also be used for GO and minesweeper. http://en.wikipedia.org/wiki/Flood_fill In go you can capture groups of stones, this website portrays it with two stones. http://www.connectedglobe.com/mindy/cap6.html This is my floodfill method in Java, it is not capturing a group of stones and I have no idea why because to me it makes sense. public void floodfill(int turn, int col, int row){ for(int a = col; a<19; a++){ for(int b = row; b<19; b++){ if(turn == black){ if(stones[col][row] == white){ stones[col][row] = 0; floodfill(black, col-1, row); floodfill(black, col+1, row); floodfill(black, col, row-1); floodfill(black, col, row+1); } } } } } It searches up, down, left, right for all the stones on the board. If the stones are white it captures them by making them 0, which represents empty.

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  • Technology Choice for a Client Application [on hold]

    - by AK_
    Not sure this is the right place to ask... I'm involved in the development of a new system, and now we are passing the demos stage. We need to build a proper client application. The platform we care most about is Windows, for now at least, but we would love to support other platforms, as long as it's free :-). Or at least very cheap. We anticipate two kinds of users: Occasional, coming mostly from the web. Professional, who would probably require more features, and better performance, and probably would prefer to see a native client. Our server exposes two APIs: A SOAP API, WCF behind the scenes, that supports 100% of the functionality. A small and very fast UDP + Binary API, that duplicates some of the functionality and is intended for the sake of performance for certain real-time scenarios. Our team is mostly proficient in .Net, C#, C++ development, and rather familiar with Web development (HTML, JavaScript). We are probably intending to develop two clients (for both user profiles), a web app, and a native app. Architecturally, we would like to have as many common components as possible. We would like to have several layers: Communication, Client Model, Client Logic, shared by both of the clients. We would also like to be able to add features to both clients when only the actual UI is a dual cost, and the rest is shared. We are looking at several technologies: WPF + Silverlight, Pure HTML, Flash / Flex (AIR?), Java (JavaFx?), and we are considering poking at WinRT(or whatever the proper name is). The question is which technology would you recommend and why? And which advantages or disadvantages will it have regarding our requirements?

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  • My first time in the gambling industry

    - by sfrj
    I am a Java enterprise developer with almost 3 years of professional experience. Soon i am going to have a face to face interview with a company in the gambling industry. I already did successfully a phone screening and now for the personal interview i suppose they will ask me about some kind of white board problem or system design task. I think i am in the right place to ask about this, and would appreciate a lot if someone would give me some tips or share something related to his own experience. The things i am more interested in regarding my interview are: What are the most common challenges for programmers, in this industry? Any idea or suggestion on a white board problem they may ask me? Could you point me to some links where i can find information on the topic or sample problems in this industry?. I personally find this question very interesting not just for me. Also i think, the given answers can help also others in a similar situation. Just what i want to say whit this last comment is: Please avoid, answers like: www.google.com and so on...

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  • Compiled code spreadsheet-like cell management? (auto-updating)

    - by proGrammar
    Okay so I am fully aware how spreadsheets manage cells, they build dependency graphs where when one cell changes it tells all the other cells that are dependent on it that it changed. So they can from there update. How they update I think involves either re-evaluating the formulas stored as strings, or re-evaluating the abstract syntax tree which I think is stored differently and might be faster. Something like that. What I'm looking to do is manage a few variables in my code so I don't have to update them in the correct way, which would be a nightmare. But I also want it much faster than spreadsheets. And since I'm not looking for any functionality as great as are in these spreadsheets, I just figured from that thought point that there has to be a way to have a very fast implementation of this functionality. Especially since I don't have to modify cells after compiling unless that would be an option. I'm very new to programming so I have no idea. One example might be to have a code-generator that generates code that does this for me. But I have no clue what the generated code would look like. Specifically, how exactly would variables inform others that they need to update, and what do those variables do to update? I'm looking for any kind of ideas. Programming is not my job but nonetheless I was hoping to have some kind of system like this that would greatly help me with some stuff. Of course I have been programming plenty lately so I can still program. I just don't have the full scope on things. I'm looking for any kind of ideas, thank you very much in advance! Also, please help me with the tags. I know C# and Java mainly and I'm hoping to implement this in either of those languages and I'm hoping this can stay in those tags. Forcing this into some kind of spreadsheet tag wouldn't be accurate.

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  • Materialized View vs POJO View based on Objects representing Oracle tables

    - by Zack Macomber
    I have about 12 Oracle tables that represent data that's being integrated from an external system into my web application. This data is going to be used in an informational and comparative manner for the clients using my web application. On one particular page of my web application, I need to combine data from 3 - 5 Oracle tables for display as an HTML table on the page. We are NOT currently using a framework (Apache Struts for instance) and we're not in a position to move this Java web application into one at this moment (I'm trying to get us there...). I am certainly not an architect, but I see one of two ways that I can effectively build this page (I know there are other ways, but these seem like they would be good ones...): 1. Create an Oracle Materialized View that represents what the HTML table should look like and then create a POJO based on the View that I can then integrate into my JSP. 2. Create POJOs that represent the Oracle tables themselves and then create another POJO that is the View used for the HTML table and then integrate that POJO into my JSP. To me, it seems the Materialized View would possibly offer quicker results which is always what we strive for in web applications. But, if I just create 12 POJOs that represent the Oracle tables and then build POJO Views off of those, I have the advantage of keeping all the code in one place for this and possibility for creating any number of different views and reusable components in my web application. Any thoughts on which one might be the better route? Or, maybe you know of an even better one?

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  • General Session: Building and Managing a Private Oracle Java and Middleware Cloud

    - by Ruma Sanyal
    If you are developing, managing, or planning enterprise Java and business application deployments on Oracle WebLogic Server with Oracle Coherence or Oracle GlassFish Server applications or continue to have deployments of Oracle Application Server, this session will give you the roadmap of how Oracle is evolving this infrastructure to be the next-generation application foundation for its customers to build on in a private cloud setting. In the session, Ajay Patel, VP of Product Management, and the product management team shares Oracle's vision, product plans, and roadmap for this server infrastructure and how it will be used in the rapidly maturing cloud infrastructure space. The presentation will help you make key decisions about running your enterprise applications on Oracle's enterprise Java server foundation. For more information about this and other Cloud Application Foundation sessions, review the Cloud Application Foundation Focus On document. Details: Monday, 10/1; 4.45-5.45pm; Moscone West Room 3014

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  • Breakout ball collision detection, bouncing against the walls

    - by Sri Harsha Chilakapati
    I'm currently trying to program a breakout game to distribute it as an example game for my own game engine. http://game-engine-for-java.googlecode.com/ But the problem here is that I can't get the bouncing condition working properly. Here's what I'm using. public void collision(GObject other){ if (other instanceof Bat || other instanceof Block){ bounce(); } else if (other instanceof Stone){ other.destroy(); bounce(); } //Breakout.HIT.play(); } And here's by bounce() method public void bounce(){ boolean left = false; boolean right = false; boolean up = false; boolean down = false; if (dx < 0) { left = true; } else if (dx > 0) { right = true; } if (dy < 0) { up = true; } else if (dy > 0) { down = true; } if (left && up) { dx = -dx; } if (left && down) { dy = -dy; } if (right && up) { dx = -dx; } if (right && down) { dy = -dy; } } The ball bounces the bat and blocks but when the block is on top of the ball, it won't bounce and moves upwards out of the game. What I'm missing? Is there anything to implement? Please help me.. Thanks

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  • Good practice or service for monitoring unhandled application errors for a small organization

    - by palto
    I'm working with multiple software with varying ways of monitoring for errors. When I make software, I usually send email with the stack trace to admins(usually me). Some customer software is monitored by a team who check that a particular batch run was successfull. Other software might not have any monitoring at all(someone will call when things go wrong horribly). Sending emails is good, except when things start going wrong, my mail gets filled fast. Also I don't want to solve the same problem in code for every software. Is there some relatively cheap and low maintenance software or practice to handle this. I want it to be cheap/low maintenance because usually I work alone or in teams of 5 or smaller. For example it would be great if errors would be aggregated so I don't get 10 000 emails when something unexpected happens... For clarification: By unhandled errors I mean Exceptions that were unhandled by application code that were propagated to Tomcat or Jboss. I don't need help with how to catch those errors. I need help with what to do with them. Is there any cloud application that I could send my errors to? Or some simple server to install? Or some library that can handle errors using configuration files. I use Java if that is any help.

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  • Compressing 2D level data

    - by Lucius
    So, I'm developing a 2D, tile based game and a map maker thingy - all in Java. The problem is that recently I've been having some memory issues when about 4 maps are loaded. Each one of these maps are composed of 128x128 tiles and have 4 layers (for details and stuff). I already spent a good amount of time searching for solutions and the best thing I found was run-length enconding (RLE). It seems easy enough to use with static data, but is there a way to use it with data that is constantly changing, without a big drop in performance? In my maps, supposing I'm compressing the columns, I would have 128 rows, each with some amount of data (hopefully less than it would be without RLE). Whenever I change a tile, that whole row would have to be checked and I'm affraid that would slow down too much the production (and I'm in a somewhat tight schedule). Well, worst case scenario I work on each map individually, and save them using RLE, but it would be really nice if I could avoind that. EDIT: What I'm currently using to store the data for the tiles is a 2D array of HashMaps that use the layer as key and store the id of the tile in that position - like this: private HashMap< Integer, Integer [][]

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