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  • Why do we need private variables?

    - by rak
    Why do we need private variables in classes in the context of programming? Every book on programming I've read says this is a private variable, this is how you define it but stops there. The wording of these explanations always seemed to me like we really have a crisis of trust in our profession. The explanations always sounded like other programmers are out to mess up our code. Yet, there are many programming languages that do not have private variables. What do private variables help prevent? How do you decide if a particular of properties should be private or not? If by default every field SHOULD be private then why are there public data members in a class? Under what circumstances should a variable be made public?

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  • Android Bitmap: Collision Detecting

    - by Aekasitt Guruvanich
    I am writing an Android game right now and I would need some help in the collision of the Pawns on screen. I figured I could run a for loop on the Player class with all Pawn objects on the screen checking whether or not Width*Height intersects with each other, but is there a more efficient way to do this? And if you do it this way, many of the transparent pixel inside the rectangular area will also be considered as collision as well. Is there a way to check for collision between Bitmap on a Canvas that disregard transparent pixels? The class for player is below and the Pawn class uses the same method of display. Class Player { private Resources res; // Used for referencing Bitmap from predefined location private Bounds bounds; // Class that holds the boundary of the screen private Bitmap image; private float x, y; private Matrix position; private int width, height; private float velocity_x, velocity_y; public Player (Resources resources, Bounds boundary) { res = resources; bounds = boundary; image = BitmapFactory.decodeResource(res, R.drawable.player); width = image.getWidth(); height = image.getHeight(); position = new Matrix(); x = bounds.xMax / 2; // Initially puts the Player in the middle of screen y = bounds.yMax / 2; position.preTranslate(x,y); } public void draw(Canvas canvas) { canvas.drawBitmap(image, position, null); } }

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  • LibGDX onTouch() method kill on touch

    - by johnny-b
    How can I add this on my application. i want to use the onTouch() method from the implementation of the InputProcessor to kill the enemies on screen. how do i do that? do i have to do anything to the enemy class? please help Thank you M @Override public boolean touchDown(int screenX, int screenY, int pointer, int button) { return false; } here is my enemy class public class Bullet extends Sprite { private Vector2 velocity; private float lifetime; public Bullet(float x, float y) { velocity = new Vector2(0, 0); } public void update(float delta) { float targetX = GameWorld.getBall().getX(); float targetY = GameWorld.getBall().getY(); float dx = targetX - getX(); float dy = targetY - getY(); float distToTarget = (float) Math.sqrt(dx * dx + dy * dy); velocity.x += dx * delta; velocity.y += dy * delta; } } i am rendering all graphics in a GameRender class and a gameworld class if you need more info please let me know Thank you

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  • Mahout - Clustering - "naming" the cluster elements

    - by Mark Bramnik
    I'm doing some research and I'm playing with Apache Mahout 0.6 My purpose is to build a system which will name different categories of documents based on user input. The documents are not known in advance and I don't know also which categories do I have while collecting these documents. But I do know, that all the documents in the model should belong to one of the predefined categories. For example: Lets say I've collected a N documents, that belong to 3 different groups : Politics Madonna (pop-star) Science fiction I don't know what document belongs to what category, but I know that each one of my N documents belongs to one of those categories (e.g. there are no documents about, say basketball among these N docs) So, I came up with the following idea: Apply mahout clustering (for example k-mean with k=3 on these documents) This should divide the N documents to 3 groups. This should be kind of my model to learn with. I still don't know which document really belongs to which group, but at least the documents are clustered now by group Ask the user to find any document in the web that should be about 'Madonna' (I can't show to the user none of my N documents, its a restriction). Then I want to measure 'similarity' of this document and each one of 3 groups. I expect to see that the measurement for similarity between user_doc and documents in Madonna group in the model will be higher than the similarity between the user_doc and documents about politics. I've managed to produce the cluster of documents using 'Mahout in Action' book. But I don't understand how should I use Mahout to measure similarity between the 'ready' cluster group of document and one given document. I thought about rerunning the cluster with k=3 for N+1 documents with the same centroids (in terms of k-mean clustering) and see whether where the new document falls, but maybe there is any other way to do that? Is it possible to do with Mahout or my idea is conceptually wrong? (example in terms of Mahout API would be really good) Thanks a lot and sorry for a long question (couldn't describe it better) Any help is highly appreciated P.S. This is not a home-work project :)

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  • Is there any complications or side effects for changing final field access/visibility modifier from private to protected?

    - by Software Engeneering Learner
    I have a private final field in one class and then I want to address that field in a subclass. I want to change field access/visibility modifier from private to protected, so I don't have to call getField() method from subclass and I can instead address that field directly (which is more clear and cohessive). Will there be any side effects or complications if I change private to protected for a final field? UPDATE: from logical point of view, it's obvious that descendant should be able to directly access all predecessor fields, right? But there are certain constraints that are imposed on private final fields by JVM, like 100% initialization guarantee after construction phase(useful for concurrency) and so on. So I would like to know, by changing from private to protected, won't that or any other constraints be compromised?

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  • How to model an address type in DDD?

    - by Songo
    I have an User entity that has a Set of Address where Address is a value object: class User{ ... private Set<Address> addresses; ... public setAddresses(Set<Address> addresses){ //set all addresses as a batch } ... } A User can have a home address and a work address, so I should have something that acts as a look up in the database: tbl_address_type ------------------------------------------------ | address_type_id | address_type | ------------------------------------------------ | 1 | work | ------------------------------------------------ | 2 | home | ------------------------------------------------ and correspondingly tbl_address ------------------------------------------------------------------------------------- | address_id | address_description |address_type_id| user_id | ------------------------------------------------------------------------------------- | 1 | 123 main street | 1 | 100 | ------------------------------------------------------------------------------------- | 2 | 456 another street | 1 | 100 | ------------------------------------------------------------------------------------- | 3 | 789 long street | 2 | 200 | ------------------------------------------------------------------------------------- | 4 | 023 short street | 2 | 200 | ------------------------------------------------------------------------------------- Should the address type be modeled as an Entity or Value type? and Why? Is it OK for the Address Value object to hold a reference to the Entity AdressType (in case it was modeled as an entity)? Is this something feasible using Hibernate/NHibernate? If a user can change his home address, should I expose a User.updateHomeAddress(Address homeAddress) function on the User entity itself? How can I enforce that the client passes a Home address and not a work address in this case? (a sample implementation is most welcomed) If I want to get the User's home address via User.getHomeAddress() function, must I load the whole addresses array then loop it and check each for its type till I found the correct type then return it? Is there a more efficient way than this?

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  • Which jar has JBox2d's p5 package

    - by Brantley Blanchard
    Using eclipse, I'm trying to write a simple hello world program in processing that simply draws a rectangle on the screen then has gravity drop it as seen in this Tutorial. The problem is that when I try to import the p5 package, it's not resolving so I can't declare my Physics object. I tried two things. Download the zip, unzip it, then import the 3 jars (library, serialization, & testbed) a. import org.jbox2d.p5.*; doesn't resolve but the others do b. Physics physics; doesn't resolve Download the older standalone testbed jar then import it a. Physics physics; doesn't resolve; Here is basically where I'm starting import org.jbox2d.util.nonconvex.*; import org.jbox2d.dynamics.contacts.*; import org.jbox2d.testbed.*; import org.jbox2d.collision.*; import org.jbox2d.common.*; import org.jbox2d.dynamics.joints.*; import org.jbox2d.p5.*; import org.jbox2d.dynamics.*; import processing.core.PApplet; public class MyFirstJBox2d extends PApplet { Physics physics; public void setup() { size(640,480); frameRate(60); initScene(); } public void draw() { background(0); if (keyPressed) { //Reset everything physics.destroy(); initScene(); } } public void initScene() { physics = new Physics(this, width, height); physics.setDensity(1.0f); physics.createRect(300,200,340,300); } }

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  • Pattern for loading and handling resources

    - by Enoon
    Many times there is the need to load external resources into the program, may they be graphics, audio samples or text strings. Is there a patten for handling the loading and the handling of such resources? For example: should I have a class that loads all the data and then call it everytime I need the data? As in: GraphicsHandler.instance().loadAllData() ...//and then later: draw(x,y, GraphicsHandler.instance().getData(WATER_IMAGE)) //or maybe draw(x,y, GraphicsHandler.instance().WATER_IMAGE) Or should I assign each resource to the class where it belongs? As in (for example, in a game): Graphics g = GraphicsLoader.load(CHAR01); Character c = new Character(..., g); ... c.draw(); Generally speaking which of these two is the more robust solution? GraphicsHandler.instance().getData(WATER_IMAGE) //or GraphicsHandler.instance().WATER_IMAGE //a constant reference

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  • What is the best practice for reading a large number of custom settings from a text file?

    - by jawilmont
    So I have been looking through some code I wrote a few years ago for an economic simulation program. Each simulation has a large number of settings that can be saved to a file and later loaded back into the program to re-run the same/similar simulation. Some of the settings are optional or depend on what is being simulated. The code to read back the parameters is basically one very large switch statement (with a few nested switch statements). I was wondering if there is a better way to handle this situation. One line of the settings file might look like this: #RA:1,MT:DiscriminatoryPriceKDoubleAuction,OF:Demo Output.csv,QM:100,NT:5000,KP:0.5 //continues... And some of the code that would read that line: switch( Character.toUpperCase( s.charAt(0) ) ) { case 'R': randSeed = Integer.valueOf( s.substring(3).trim() ); break; case 'M': marketType = s.substring(3).trim(); System.err.println("MarketType: " + marketType); break; case 'O': outputFileName = s.substring(3).trim() ; break; case 'Q': quantityOfMarkets = Integer.valueOf( s.substring(3).trim() ); break; case 'N': maxTradesPerRound = Integer.valueOf( s.substring(3).trim() ); break; case 'K': kParameter = Float.valueOf( s.substring(3).trim() ); break; // continues... }

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  • How do I combine the two methods of cryptography, CBC cipher block and Vingenere Chiper [on hold]

    - by Bangpe
    Code Vingenere static String encrypt(String text, final String key) { String res = ""; text = text.toUpperCase(); for (int i = 0, j = 0; i < text.length(); i++) { char c = text.charAt(i); if (c < 'A' || c > 'Z') continue; res += (char)((c + key.charAt(j) - 2 * 'A') % 26 + 'A'); j = ++j % key.length(); } return res; } Code CBC Chiper public CbcBlockCipher( BlockCipher blockCipher ) { super( blockCipher.keySize(), blockCipher.blockSize() ); this.blockCipher = blockCipher; iv = new byte[blockSize()]; zeroBlock( iv ); temp = new byte[blockSize()]; }

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  • How come I cannot make this file executable (chmod permissions)?

    - by bappi48
    I downloaded Android Development Tool for linux (ADT) and placed it in home directory. After unzipping the files, when I double click the "eclipse" executable file; the eclipse works perfectly fine. But If I unzip the ADT in a different directory, in my case directory E: (is shown when I boot in windows 7) There double clicking the same "eclipse" executable file does not run eclipse. It shows error message: Could not display /media/Software/00.AndroidLinux/ADT/eclipse/eclipse. There is no application installed for executable files. Do you want to search for an application to open this file? If I press yes in the Dialog, it finds "Pypar2" which is not my solution. I found that the "eclipse" file permission is following -rw------- 1 tanvir tanvir 63050 Feb 4 19:05 eclipse I tried to change the permission by "chmod +x eclipse" , but no use. This command does not change the file permission at all in this case. what should I do? Relevant output of cat /proc/mounts: /dev/sda6 /media/Software fuseblk rw,nosuid,nodev,relatime,user_id=0,group_id=0,default_permissions,allow_other,blksize=4096 0 0 Please not that I'm new to Ubuntu and still learning day by day.

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  • Android game scrolling background

    - by Stevanicus
    Hi There, I'm just trying to figure out the best approach for running a scolling background on an android device. The method I have so far.... its pretty laggy. I use threads, which I believe is not the best bet for android platforms @Override public void run() { // Game Loop while(runningThread){ //Scroll background down bgY += 1; try { this.postInvalidate(); t.sleep(10); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } } where postinvalidate in the onDraw function simply pushings the background image down canvas.drawBitmap(backgroundImage, bgX, bgY, null); Thanks in advance

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  • using NetBeans for rotate a figure in a label [migrated]

    - by user134812
    I was reading this post: http://forums.netbeans.org/post-8864.html and what I have done so far is to make a jFrame in NetBeans, on it I have drawn a jPanel and inisde the panel I have drawn a jLabel on it and use the icon property to put an image on it; until now all is so far so good. I would like to make a program that everytime I click on the figure it rotates it to the right. Actually I have found the following code: public class RotateImage extends JPanel{ // Declare an Image object for us to use. Image image; // Create a constructor method public RotateImage(){ super(); // Load an image to play with. image = Toolkit.getDefaultToolkit().getImage("Duke_Blocks.gif"); } public void paintComponent(Graphics g){ Graphics2D g2d=(Graphics2D)g; // Create a Java2D version of g. g2d.translate(170, 0); // Translate the center of our coordinates. g2d.rotate(1); // Rotate the image by 1 radian. g2d.drawImage(image, 0, 0, 200, 200, this); } but for what I see this code is for making the panel and other components from scratch, for my purposes it is not so good because I need to put several figures on my jFrame. Could somebody can give me a hint how to do this?

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  • Advice needed on Process - Service Design

    - by user99314
    Need some advice from experts on designing a flow. Create a service that will read a csv file which may contain anywhere over 6000+ rows of individual ids as shown in the sample below. Need to read that file and go to oracle database and fetch a vname,vnumber,vid of each id in the csv and then go to document repository i.e. Oracle UCM and download all documents matching vname,vnumber,vid there can be =0 documents for each vname,vnumber,vid and save them on a file system. UCM exposes a webservice to dowload the documents. Finally create a new csv appending the filenames that are downloaded for each id. Need to keep track of any errors but need to make sure to go over the whole ids in the csv to download the documents and skip in case of errors. Need some advice on how to go about designing this as there may be over 6000+ rows in a csv file and looping it and hitting the database for each individual id and then hitting a UCM may be a bit expensive so open for any idea. How to go by designing this solution. Wondering if messaging can be helpful here or offloading process of getting the vname,vnumber,vid to pl/sql packages, creating staging tables etc. Initial csv that contains ids: **ID** 12345a 12s345 3456fr we9795 we9797 Final csv output: **ID Files Downloaded from UCM** 12345a a.pdf,b.doc,d.txt 12s345 a1.pdf,s2.pdf,f4.gif 3456fr b.xls we9795 we9797 x.doc Thanks

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  • How to stop reducing life? [closed]

    - by SystemNetworks
    CODE Input input = gc.getInput(); int xpos = Mouse.getX(); int ypos = Mouse.getY(); emu = "Enemy Life : " + enemyLife; Life = "Your Life Is" + life; Mousepos = "X:" + xpos + "Y:" + ypos; //test test1 = "Test INT" + test1int; if(!repeatStop) { //if this button is press, the damage will add up. When //pressed fight, it would start reducing the enemy health. if(input.isKeyPressed(Input.KEY_1)) { test1int += 1; } } if((xpos>1007 &xpos<1297)&&(ypos>881 && ypos<971)) { //Fight button if(Mouse.isButtonDown(0)){ finishTurn=true; } } //fight has started if(finishTurn==true) { //this would reduce the enemy life if(floodControl1==false) { enemyLife-=test1int; } //PROBLEM: Does not stop reducing! //the below code was not successful. It did not stop it // from reducing further. if(test1int>10) { floodControl1=true; } } QUESTION: Ok now, this is what is does. When I press the key, 1, it adds up the damage to the enemy. When I press fight, It will then start to reduce the enemy's health. Now my problem is, it kept on reducing and deducting it until negative! How do I deduct it to my desired damage (My desired damage is the one when press key 1)?

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  • Using Single Image for Map in 2D Platformer

    - by Jon
    I'm fairly new to game development, and have been messing around with Slick2D. Currently, my map consists of objects that are represented as rectangles. If I wanted to use am image simlar to: How would I be able to use this image to make a level? That question is a bit vague, but like I said, I'm new to game development and am not familiar with terminology or procedures. But going along with this question, how would I also use non-rectangular objects/platforms? Thanks

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  • How do I make a dialog box? [on hold]

    - by bill
    By dialog box I mean when player talks to someone, a box shows up with text on it. I haven't found much about this topic online, so I created a basic dialog box: //in dialog box i have only two methods public void createBox(int x, int y, int width, int height, String txt) { this.x = x; this.y = y; this.width = width; this.height = height; this.txt = txt; } //draw dialog box public void draw(Graphics2D g) { if (txt != null) { g.setColor(Color.red); g.drawRect(x,y,width,height); g.setColor(Color.black); g.fillRect(x, y, width, height); g.setColor(Color.white); g.drawString(txt, x + 10, y + 10); } } I wanted to now can I make this better?

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  • Where are the values of java.library.path being set?

    - by lmestre
    This one could be a WebLogic Server question, but this post is general for any java environment.We were getting  at the very beginning  java library path something like this: /home/lmestre/jdk1.6/jre/lib/amd64/server:/home/lmestre/jdk1.6/jre/lib/amd64:/home/lmestre/jdk1.6/jre/../lib/amd64So, the question was: Where WebLogic Server is setting java.library.path?I never found the answer, so why don't we try to try to answerWhere the JVM is setting java.library.path?public class LibraryPathPrinter {   public static void main(String[] args) {       String javaLibraryPath= System.getProperty("java.library.path");       System.out.println("java.library.path "+javaLibraryPath );   }}after a simplejavac LibraryPathPrinter.javaand then an easyjava LibraryPathPrintervoila!The program printed something like thisjava.library.path  /home/lmestre/jdk1.6/jre/lib/amd64/server:/home/lmestre/jdk1.6/jre/lib/amd64:/home/lmestre/jdk1.6/jre/../lib/amd64So the JVM was the culprit.Enjoy!

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  • Legality of modifying and distributing the JRE

    - by herpylderp
    I see that Google App Engine apps run on a so-called secured sandbox JRE; that is, a JRE that Google modified and that makes changes to certain JRE types. This is how GAE prevents developers from writing apps that can do things like: Access the local file system via File Make remote JDBC calls Use JNDI Lots of other restrictions We have a similar need where we have an app that developers will be able to write plugins for. These plugins will need to utilize an API (a JAR) that we distribute with our app. We cannot afford for plugins to do certain things, particularly on the end user's file system, and need to modify the File class in a similar manner that GAE does. Long back-story short, this means we'll need to ship our app with a custom, modified JRE. My question: is this legal to do, or did Google likely pay Oracle some fee to modify/distribute their own JRE for app engine?

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  • Use constructor or setter method?

    - by user633600
    I am working on a UI code where I have an Action class, something like this - public class MyAction extends Action { public MyAction() { setText("My Action Text"); setToolTip("My Action Tool tip"); setImage("Some Image"); } } When this Action class was created it was pretty much assumed that the Action class wont be customizable (in a sense- its text, tooltip or image will be not be changed anywhere in the code). Of late, now we are in need of changing the action text at some location in code. So I suggested my co-worker to remove the hardcoded action text from the constructor and accept it as an argument, so that everybody is forced to pass the action text. Something like this code below - public class MyAction extends Action { public MyAction(String actionText) { setText(actionText); setTooltip("My Action tool tip); setImage("My Image"); } } He however thinks that since setText() method belongs to base class. It can be flexibly used to pass the action text wherever action instance is created. That way, there is no need to change the existing MyAction class. So his code would look something like this. MyAction action = new MyAction(); //this creates action instance with the hardcoded text action.setText("User required new action text"); //overwrite the exisitng text. I am not sure if that is a correct way to deal with problem. I think in above mentioned case user is anyway going to change the text, so why not force him while constructing the action. The only benefit I see with the original code is that user can create Action class without much thinking about setting text.

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  • Netbeans 7.0.1 installed but won't run

    - by Dave M G
    I installed Netbeans 7.0.1, and I've made sure to install all the JDKs and JREs I could find. It installed without errors. I also saw this question and made sure I followed all the instructions there as well. I never got any error messages of any kind. So far as I know, it installed okay. However, when I try to run Netbeans, I get no response. If I run it from the command line, after about 30 seconds, the prompt just comes back. There's no error message of any kind to let me know what's wrong. $ /bin/sh "/home/dave/netbeans-7.0.1/bin/netbeans" $ What's the issue, and how do I get Netbeans to run?

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  • Collision Detection within Player/Enemy Class

    - by user1264811
    I'm making a 2D platform game. Right now I'm just working on making a very generic Player class. I'm wondering if it would be more efficient/better practice to have an ActionListener within the Player class to detect collisions with Enemy objects (also have an ActionListener) or to handle all the collisions in the main world. Furthermore, I'm thinking ahead about how I will handle collisions with the platforms themselves. I've looked into the double boolean arrays to see which tiles players can go to and which they can't. I don't understand how to use this class and the player class at the same time. Thank you.

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  • Greenfoot project is read-only

    - by AzharHafiz.com
    I received this message when starting greenfoot on ubuntu 11.10 I'm a newbie and not sure where does the file located (greenfoot) The project is read-only.How and where do I change the permission? You will not be able to create objects or execute methods. Either the access rights of the project directory are set as 'read only' for you, or the whole file system is not writable (is it a CD?). To fully use this project, you must ensure that it is on a writable file system (usually your hard disk), and that you have write permission in the project directory and each file within it. This can often be accomplished by choosing "save as" from the Project menu after closing this dialog.

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  • Split up a screen into regions

    - by nexen
    My task: I want to split up a screen into 3 regions for buffs-bar (with picked items), score-info and a game-map. It doesn't matter are regions intersect with each other or not. For example: I have a screen with width=1; height=1 and the origin of coordinates (0;0) is the left bottom point. I have 3 functions: draw items, draw info, draw map. If I use it without any matrix transformations, it draws fullscreen, because it's vertex coordinates are from 0;0 to 1;1. (pseudo-code) drawItems(); drawInfo(); drawMap(); And after that I see only map onto info onto items. My goal: I have some matrixes for transformation vertexes with 0;0-1;1 coordinates to strict regions. There is only one thing, what I need to do - set matrix before drawing. So my call of drawItems-function is like: (pseudo-code) adjustViewMatrixes_andSomethingElse(items.position_of_the_region_there_it_should_be_drawn, items.sizes_of_region_to_draw); setItemsMatrix(); drawItems(); //the same function with vertex coordinates 0;0->1;1, //but it draws in other coordinates, //because I have just set the matrix for region I know only some people will understand me, so there is a picture with regions which I need to make. Every region has 0;0 - 1;1 inner coordinates.

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  • Android real time multiplayer over LAN

    - by Heigo
    I've developed several games for the android platform and now planning to create my first multiplayer game. What I have in mind is basically just a 2-player game witch you can play with 2 phones over local area connection/WiFi. Both phones need to be able to pass 3 integer values to the other phone in real time. So far I have considered using Socket's, but before I dig into it too deep I wanted to ask if there might be a better approach? Thanks!

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