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  • What is bootstrap listener in the context of Spring framework?

    - by jillionbug2fix
    I am studying Spring framework, in web.xml I added following which is a bootstrap listener. Can anyone give me a proper idea of what is a bootstrap listener? <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> You can see the doc here: ContextLoadListener Bootstrap listener to start up and shut down Spring's root WebApplicationContext. Simply delegates to ContextLoader as well as to ContextCleanupListener. This listener should be registered after Log4jConfigListener in web.xml, if the latter is used. As of Spring 3.1, ContextLoaderListener supports injecting the root web application context via the ContextLoaderListener(WebApplicationContext) constructor, allowing for programmatic configuration in Servlet 3.0+ environments. See WebApplicationInitializer for usage examples...

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  • Has MyEclipse implicit breakpoint in debugging mode in class URLClassPath [migrated]

    - by MJM
    I am beginner in MyEclipse IDEA. I using 8.6.1 version of it. My issue is: When I execute my program in debug mode, MyEclipse go to sun.misc.URLClassPath class and I must Resume breakpoint(by pressing F8 key) and continue executing my program. MyEclipse stay in URLClassPath class in following thread stack: 1. URLClassPath$JarLoader.<init>(URL, URLStreamHandler, HashMap) line: 581 2. URLClassPath$JarLoader.ensureOpen() line: 631 3. URLClassPath$JarLoader.getJarFile(URL) line: 641 4. URLClassPath$JarLoader.ensureOpen() line: 631 Note: this event happen when some jar file exist in my project Build-Path but when my application is simple this problem don't make and first breakpoint is my first breakpoint. Why this event happened?

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  • Opposite Force to Apply to a Collided Rigid Body?

    - by Milo
    I'm working on the physics for my GTA2-like game so I can learn more about game physics. The collision detection and resolution are working great. I'm now just unsure how to compute the force to apply to a body after it collides with a wall. My rigid body looks like this: /our simulation object class RigidBody extends Entity { //linear private Vector2D velocity = new Vector2D(); private Vector2D forces = new Vector2D(); private float mass; private Vector2D v = new Vector2D(); //angular private float angularVelocity; private float torque; private float inertia; //graphical private Vector2D halfSize = new Vector2D(); private Bitmap image; private Matrix mat = new Matrix(); private float[] Vector2Ds = new float[2]; private Vector2D tangent = new Vector2D(); private static Vector2D worldRelVec = new Vector2D(); private static Vector2D relWorldVec = new Vector2D(); private static Vector2D pointVelVec = new Vector2D(); private static Vector2D acceleration = new Vector2D(); public RigidBody() { //set these defaults so we don't get divide by zeros mass = 1.0f; inertia = 1.0f; setLayer(LAYER_OBJECTS); } protected void rectChanged() { if(getWorld() != null) { getWorld().updateDynamic(this); } } //intialize out parameters public void initialize(Vector2D halfSize, float mass, Bitmap bitmap) { //store physical parameters this.halfSize = halfSize; this.mass = mass; image = bitmap; inertia = (1.0f / 20.0f) * (halfSize.x * halfSize.x) * (halfSize.y * halfSize.y) * mass; RectF rect = new RectF(); float scalar = 10.0f; rect.left = (int)-halfSize.x * scalar; rect.top = (int)-halfSize.y * scalar; rect.right = rect.left + (int)(halfSize.x * 2.0f * scalar); rect.bottom = rect.top + (int)(halfSize.y * 2.0f * scalar); setRect(rect); } public void setLocation(Vector2D position, float angle) { getRect().set(position.x,position.y, getWidth(), getHeight(), angle); rectChanged(); } public Vector2D getPosition() { return getRect().getCenter(); } @Override public void update(float timeStep) { doUpdate(timeStep); } public void doUpdate(float timeStep) { //integrate physics //linear acceleration.x = forces.x / mass; acceleration.y = forces.y / mass; velocity.x += (acceleration.x * timeStep); velocity.y += (acceleration.y * timeStep); //velocity = Vector2D.add(velocity, Vector2D.scalarMultiply(acceleration, timeStep)); Vector2D c = getRect().getCenter(); v.x = getRect().getCenter().getX() + (velocity.x * timeStep); v.y = getRect().getCenter().getY() + (velocity.y * timeStep); setCenter(v.x, v.y); forces.x = 0; //clear forces forces.y = 0; //angular float angAcc = torque / inertia; angularVelocity += angAcc * timeStep; setAngle(getAngle() + angularVelocity * timeStep); torque = 0; //clear torque } //take a relative Vector2D and make it a world Vector2D public Vector2D relativeToWorld(Vector2D relative) { mat.reset(); Vector2Ds[0] = relative.x; Vector2Ds[1] = relative.y; mat.postRotate(JMath.radToDeg(getAngle())); mat.mapVectors(Vector2Ds); relWorldVec.x = Vector2Ds[0]; relWorldVec.y = Vector2Ds[1]; return relWorldVec; } //take a world Vector2D and make it a relative Vector2D public Vector2D worldToRelative(Vector2D world) { mat.reset(); Vector2Ds[0] = world.x; Vector2Ds[1] = world.y; mat.postRotate(JMath.radToDeg(-getAngle())); mat.mapVectors(Vector2Ds); worldRelVec.x = Vector2Ds[0]; worldRelVec.y = Vector2Ds[1]; return worldRelVec; } //velocity of a point on body public Vector2D pointVelocity(Vector2D worldOffset) { tangent.x = -worldOffset.y; tangent.y = worldOffset.x; pointVelVec.x = (tangent.x * angularVelocity) + velocity.x; pointVelVec.y = (tangent.y * angularVelocity) + velocity.y; return pointVelVec; } public void applyForce(Vector2D worldForce, Vector2D worldOffset) { //add linear force forces.x += worldForce.x; forces.y += worldForce.y; //add associated torque torque += Vector2D.cross(worldOffset, worldForce); } @Override public void draw( GraphicsContext c) { c.drawRotatedScaledBitmap(image, getPosition().x, getPosition().y, getWidth(), getHeight(), getAngle()); } public Vector2D getVelocity() { return velocity; } public void setVelocity(Vector2D velocity) { this.velocity = velocity; } } The way it is given force is by the applyForce method, this method considers angular torque. I'm just not sure how to come up with the vectors in the case where: RigidBody hits static entity RigidBody hits other RigidBody that may or may not be in motion. Would anyone know a way (without too complex math) that I could figure out the opposite force I need to apply to the car? I know the normal it is colliding with and how deep it collided. My main goal is so that say I hit a building from the side, well the car should not just stay there, it should slowly rotate out of it if I'm more than 45 degrees. Right now when I hit a wall I only change the velocity directly which does not consider angular force. Thanks!

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  • Need help with this question [closed]

    - by Jaime
    Occasionally, multiplying the sizes of nested loops can give an overestimate for the Big-Oh running time. This result happens when an innermost loop is infrequently executed. Give the Big-O analysis of the running time. Implement the following code and run for several values of N, and compare your analysis with the actual running times. for(int i = 1; i <= n; i++) for(int j = 1; j<=i * i; j++) if(j%i == 0) for(int k = 0; k < j; k++) sum++;

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  • Validating data to nest if or not within try and catch

    - by Skippy
    I am validating data, in this case I want one of three ints. I am asking this question, as it is the fundamental principle I'm interested in. This is a basic example, but I am developing best practices now, so when things become more complicated later, I am better equipped to manage them. Is it preferable to have the try and catch followed by the condition: public static int getProcType() { try { procType = getIntInput("Enter procedure type -\n" + " 1 for Exploratory,\n" + " 2 for Reconstructive, \n" + "3 for Follow up: \n"); } catch (NumberFormatException ex) { System.out.println("Error! Enter a valid option!"); getProcType(); } if (procType == 1 || procType == 2 || procType == 3) { hrlyRate = hrlyRate(procType); procedure = procedure(procType); } else { System.out.println("Error! Enter a valid option!"); getProcType(); } return procType; } Or is it better to put the if within the try and catch? public static int getProcType() { try { procType = getIntInput("Enter procedure type -\n" + " 1 for Exploratory,\n" + " 2 for Reconstructive, \n" + "3 for Follow up: \n"); if (procType == 1 || procType == 2 || procType == 3) { hrlyRate = hrlyRate(procType); procedure = procedure(procType); } else { System.out.println("Error! Enter a valid option!"); getProcType(); } } catch (NumberFormatException ex) { System.out.println("Error! Enter a valid option!"); getProcType(); } return procType; } I am thinking the if within the try, may be quicker, but also may be clumsy. Which would be better, as my programming becomes more advanced?

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  • Ubuntu Software Centre Issue (unity 11.10) after broken sun-java6-jre package installation

    - by Stephen Myall
    I have been installing software packages from USC and I am getting the following error message. Worked fine one minute then the message below. Tried to search but couldn't find a solution Previously I was installing the sun-java6-jre package in terminal and had an connection outage and it didnt complete. I attempted an apt-get -f install with no success. i dont know what to try next. I'm relatively new to Linux. The answer provided with a similar question on this site didnt resolve the issue for meClick on this link An unhandlable error occured There seems to be a programming error in aptdaemon, the software that allows you to install/remove software and to perform other package management related tasks. Details File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 1092, in _simulate_helper return depends, self._cache.required_download, \ File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 235, in required_download pm.get_archives(fetcher, self._list, self._records) SystemError: E:I wasn't able to locate a file for the sun-java6-jre package. This might mean you need to manually fix this package. Terminal Output Link http://dl.dropbox.com/u/48466855/Terminal%20output.odt

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  • Slick2d Spritesheet showing whole image

    - by BotskoNet
    I'm trying to show a single subimage from a sprite sheet. Using slick2d SpriteSheet class, all it's doing is showing me the entire image, but scaled down to fit the cell dimensions. The image is 96x192 and should have cells of 32x32. The code: SpriteSheet spriteSheet = new SpriteSheet("images/"+file, 32, 32 ); System.out.println("Horiz Count: " + spriteSheet.getHorizontalCount()); System.out.println("Vert Count: " + spriteSheet.getVerticalCount()); System.out.println("Height: " + spriteSheet.getHeight()); System.out.println("Width: " + spriteSheet.getWidth()); System.out.println("Texture Width: " + spriteSheet.getTextureWidth()); System.out.println("Texture Height: " + spriteSheet.getTextureHeight()); Prints: Horiz Count: 3 Vert Count: 6 Height: 192 Width: 96 Texture Width: 0.75 Texture Height: 0.75 Not sure what the texture dimensions refer to, but the rest is entirely accurate. However, when I draw the icon, the entire sprite image shows scaled down to 32x32: Image image = spriteSheet.getSprite(1, 0); // a test image.bind(); GL11.glEnable(GL11.GL_BLEND); GL11.glBlendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE_MINUS_SRC_ALPHA); GL11.glBegin(GL11.GL_QUADS); GL11.glTexCoord2f(0,0); GL11.glVertex2f(x,y); GL11.glTexCoord2f(1,0); GL11.glVertex2f(x+image.getWidth(),y); GL11.glTexCoord2f(1,1); GL11.glVertex2f(x+image.getWidth(),y+image.getHeight()); GL11.glTexCoord2f(0,1); GL11.glVertex2f(x,y+image.getHeight()); GL11.glEnd(); GL11.glDisable(GL11.GL_BLEND);

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  • Having to check collisions twice per game tic

    - by user22241
    I have vertically moving elevators (3 solid tiles wide) and static solid tiles. Each are separate entities and therefore have their own respective collision routines (to check for, and resolve, collisions with the main character) I check my vertical collisions after characters vertical movements and then horizontal collisions after horizontal movements. The problem is that I want my platform to kill the player if it squashes him from the top, and also if he's on a moving platform (that is moving up) that squashes him into a solid block. Correct behaviour, player on solid blocks being squashed from above by decending elevator Here is what happens. Gravity pushes character into solid block, solid block collision routine corrects characters position and sits him on the solid block which pushes him into the moving elevator, elevator routine then checks for collision and kills player. This assumes I am checking solid blocks first, then elevator collisions. However, if it's the other way around, this happens.... Incorrect behaviour, player on accending elevator gets pushed into solid blocks above Player is on an elevator moving up, gravity pushes him into the elevator, solid block CD routine detects no collision, no action taken. Elevator CD routine detects character has been pushed into elevator by gravity, corrects this by moving character up and sitting him on the elevator and pushes him into the solid blocks above, however the solid block vertical routine has now already run for this tic, so the game continues and the next solid block collision that is encountered is the horizontal routine. This detects a collision and moves the character out of the collision to the left or right of the block which looks odd to say the least (character should get killed here). The only way I've managed to get this working correctly is by running the solid block CD, then the elevator CD, then the solid block CD again straight after. This is clearly wasteful but I can't figure out how else to do this. Any help would be appreciated.

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  • How can I Implement KeyListeners/ActionListeners into the JFrame?

    - by A.K.
    I'll get to the point: I have a player in my game that you control with the keyboard yet the key methods in the player class and ActionListener w/ KeyAdapter in the Board class don't seem to fire. So far I've tried adding these key methods into the JFrame, doesn't seem to let me move him even though other objects that I have (enemies) can move fine. Here's part of the JFrame class with the event listeners: frm.addKeyListener(KeyBoardListener); public void mouseClicked(MouseEvent e) { nSound.play(); StartB.setContentAreaFilled(false); cards.remove(StartB); frm.remove(TitleL); frm.remove(cards); frm.setLayout(new GridLayout(1, 1)); frm.add(nBoard); //Add Game "Tiles" Or Content. x = 1200 nBoard.setPreferredSize(new Dimension(1200, 420)); cards.revalidate(); frm.validate(); } public KeyListener KeyBoardListener = new KeyListener() { @Override public void keyPressed(KeyEvent args0) { int key = args0.getKeyCode(); if(key == KeyEvent.VK_LEFT) { nBoard.S.vx = -4; } if(key == KeyEvent.VK_RIGHT) { nBoard.S.vx = 4; } if(key == KeyEvent.VK_UP) { nBoard.S.vy = -4; } if(key == KeyEvent.VK_DOWN) { nBoard.S.vy = 4; } if(key == KeyEvent.VK_SPACE) { nBoard.S.fire(); } } @Override public void keyReleased(KeyEvent args0) { int key = args0.getKeyCode(); if(key == KeyEvent.VK_LEFT) { nBoard.S.vx = 0; } if(key == KeyEvent.VK_RIGHT) { nBoard.S.vx = 0; } if(key == KeyEvent.VK_UP) { nBoard.S.vy = 0; } if(key == KeyEvent.VK_DOWN) { nBoard.S.vy = 0; } } @Override public void keyTyped(KeyEvent args0) { // TODO Auto-generated method stub } };

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  • Slick2D Rendering Lots of Polygons

    - by Hazzard
    I'm writing an little isometric game using Slick. The world terrain is made up of lots of quadrilaterals. In a small world that is 128 by 128 squares, over 16,000 quadrilaterals need to be rendered. This puts my pretty powerful computer down to 30 fps. I've though about caching "chunks" of the world so only single chunks would ever need updating at a time, but I don't know how to do this, and I am sure there are other ways to optimize it besides that. Maybe I'm doing the whole thing wrong, surely fancy 3D games that run fine on my machine are more intensive than this. My question is how can I improve the FPS and am I doing something wrong? Or does it actually take that much power to render those polygons? -- Here is the source code for the render method in my game state. It iterates through a 2d array or heights and draws polygons based on the height. public void render(GameContainer container, StateBasedGame game, Graphics gfx) throws SlickException { gfx.translate(offsetX * d + container.getWidth() / 2, offsetY * d + container.getHeight() / 2); gfx.scale(d, d); for (int y = 0; y < placeholder.length; y++) {// x & y are isometric // diag for (int x = 0; x < placeholder[0].length; x++) { Polygon poly; int hor = TestState.TILE_WIDTH * (x - y);// hor and ver are orthagonal int W = TestState.TILE_HEIGHT * (x + y) - 1 * heights[y + 1][x];//points to go off of int S = TestState.TILE_HEIGHT * (x + y) - 1 * heights[y + 1][x + 1]; int E = TestState.TILE_HEIGHT * (x + y) - 1 * heights[y][x + 1]; int N = TestState.TILE_HEIGHT * (x + y) - 1 * heights[y][x]; if (placeholder[y][x] == null) { poly = new Polygon();//Create actual surface polygon poly.addPoint(-TestState.TILE_WIDTH + hor, W); poly.addPoint(hor, S + TestState.TILE_HEIGHT); poly.addPoint(TestState.TILE_WIDTH + hor, E); poly.addPoint(hor, N - TestState.TILE_HEIGHT); float z = ((float) heights[y][x + 1] - heights[y + 1][x]) / 32 + 0.5f; placeholder[y][x] = new Tile(poly, new Color(z, z, z)); //ShapeRenderer.fill(placeholder[y][x]); } if (true) {//ONLY draw tile if it's on screen gfx.setColor(placeholder[y][x].getColor()); ShapeRenderer.fill(placeholder[y][x]); //gfx.fill(placeholder[y][x]); //placeholder[y][x]. //DRAW EDGES if (y + 1 == placeholder.length) {//draw South foundation edges gfx.setColor(Color.gray); Polygon found = new Polygon(); found.addPoint(-TestState.TILE_WIDTH + hor, W); found.addPoint(hor, S + TestState.TILE_HEIGHT); found.addPoint(hor, TestState.TILE_HEIGHT * (x + y + 1)); found.addPoint(-TestState.TILE_WIDTH + hor, TestState.TILE_HEIGHT * (x + y)); gfx.fill(found); } if (x + 1 == placeholder[0].length) {//north gfx.setColor(Color.darkGray); Polygon found = new Polygon(); found.addPoint(TestState.TILE_WIDTH + hor, E); found.addPoint(hor, S + TestState.TILE_HEIGHT); found.addPoint(hor, TestState.TILE_HEIGHT * (x + y + 1)); found.addPoint(TestState.TILE_WIDTH + hor, TestState.TILE_HEIGHT * (x + y)); gfx.fill(found); }//*/ } } } }

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  • How do I generate a level randomly?

    - by Charlton Santana
    I am currently hard coding 10 different instances like the code below, but but I'd like to create many more. Instead of having the same layout for the new level, I was wondering if there is anyway to generate a random X value for each block (this will be how far into the level it is). A level 100,000 pixels wide would be good enough but if anyone knows a system to make the level go on and on, I'd like to know that too. This is basically how I define a block now (with irrelevant code removed): block = new Block(R.drawable.block, 400, platformheight); block2 = new Block(R.drawable.block, 600, platformheight); block3 = new Block(R.drawable.block, 750, platformheight); The 400 is the X position, which I'd like to place randomly through the level, the platformheight variable defines the Y position which I don't want to change.

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  • How do I implement smooth movement in a Box2D platform game?

    - by Romeo
    I have implemented a character in JBox2D which moves with the help of a wheel rotating at the bottom of it. The movement is the best result I've had 'till now but it's a little glitchy when the character stands on the edge. So I am thinking should I use five smaller wheels instead of a big wheel. The wheel/wheels will not be visible in the finished product, now they are drawn for debugging. Here is a video. Is there a better way to do this using JBox2D?

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  • Synchronizing local and remote cache in distributed caching

    - by ltfishie
    With a distributed cache, a subset of the cache is kept locally while the rest is held remotely. In a get operation, if the entry is not available locally, the remote cache will be used and and the entry is added to local cache. In a put operation, both the local cache and remote cache are updated. Other nodes in the cluster also need to be notified to invalidate their local cache as well. What's a simplest way to achieve this if you implemented it yourself, assuming that nodes are not aware of each other. Edit My current implementation goes like this: Each cache entry contains a time stamp. Put operation will update local cache and remote cache Get operation will try local cache then remote cache A background thread on each node will check remote cache periodically for each entry in local cache. If the timestamp on remote is newer overwrite the local. If entry is not found in remote, delete it from local.

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  • Libgdx ParallaxScrolling and TiledMaps

    - by kirchhoff
    I implemented ParallaxScrolling for my SideScroller project, everything is working but the tiled map (the most important part!). I've been trying out everything but it doesn't work (see the code below). I'm using ParallaxCamera from GdxTests, it's working perfectly for the background layers. I can't explain myself properly in english, so I recorded 2 videos: Before parallaxScrolling After parallaxScrolling As you can see, now the platforms appear in the middle of the Y-axis. I've got a Map class with 2 tiled maps, so I need two renderers too: private TiledMapRenderer renderer1; private TiledMapRenderer renderer2; public void update(GameCamera camera) { renderer1.setView(camera.calculateParallaxMatrix(1f, 0f), camera.position.x - camera.viewportWidth / 2, **camera.position.y - camera.viewportHeight/2**, camera.viewportWidth, camera.viewportHeight); renderer2.setView(camera.calculateParallaxMatrix(1f, 0f), camera.position.x - camera.viewportWidth / 2, **camera.position.y - camera.viewportHeight/2**, camera.viewportWidth, camera.viewportHeight); } In bold, the code I think I should change. I've tried changing parameters, even adding hardcoded values, etc, but one of two: 1. Nothing happens. 2. Platforms disappear. Here is some aditional code. The render method: world.update(delta); parallaxBackground.update(camera); clear(0.5f, 0.7f, 1.0f, 1); batch.setProjectionMatrix(camera.calculateParallaxMatrix(0, 0)); batch.disableBlending(); batch.begin(); batch.draw(background, -(int)background.getRegionWidth()/2, -(int)background.getRegionHeight()/2); batch.end(); batch.enableBlending(); parallaxBackground.draw(batch, camera); renderer.render(batch);

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  • Concurrency with listeners and upload: is this solution sound?

    - by cbrulak
    I'm working on an Android app. We have listeners for position data and camera capture which is timed on a background thread (not a service). The timer thread dictates when the image is captured and also when the data is cached in a local sqlite db. So, my question is how to properly store the location data as it comes in based on the listeners and pull that data so that the database can be updated as the camera capture is executed. I can't put the location data into the database as it arrives because it is processed more frequently than the camera images and the camera images are what dominates the architecture at the moment. (Location data is supplement). However I need the location data to get a rough location of the where the image is captured. My first thought was to have singleton store the location data. And have a semaphore on the getInstance method so if the database update is happening (after an image is captured) we don't have an error. The location data can wait for the database update or it can be lost for that particular event it doesn't really matter. What are you thoughts? Am I on the right track? (And is this the right sub-site or would this be better on stackoverflow?)

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  • Is Play Framework good for doing some logic parallely?

    - by pmichna
    I'm going to build a web application that's going to host urban games. A user visits my website, clicks "Start game" and starts receiving some SMS messages when gets to some location and has to answer them to get points. My question: is Play suitable for this kind of application? From what I've read I know for sure it's ok for traditional web applications: user interface for same data storage and manipulation. But what if after clicking the "start button" some logic has to go on its own course? How would I handle parallely checking geolocation of the players (I have API for that)? I guess in some threads that would ping them every ~5 sec. and do some processing but is it possible to just "disconnect" them from the main user interface? So to sum up: I want an application written in Play that starts a separate thread for a game after clicking "start game" and other users are able to view their data (statisctics etc.), while the threads work their way with the game logic. I found something like jobs but they are documented for version 1.2 (current one is 2.2). Sorry for my somewhat fuzzy explenation, I tried to do my best.

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  • Documenting mathematical logic in code

    - by Kiril Raychev
    Sometimes, although not often, I have to include math logic in my code. The concepts used are mostly very simple, but the resulting code is not - a lot of variables with unclear purpose, and some operations with not so obvious intent. I don't mean that the code is unreadable or unmaintainable, just that it's waaaay harder to understand than the actual math problem. I try to comment the parts which are hardest to understand, but there is the same problem as in just coding them - text does not have the expressive power of math. I am looking for a more efficient and easy to understand way of explaining the logic behind some of the complex code, preferably in the code itself. I have considered TeX - writing the documentation and generating it separately from the code. But then I'd have to learn TeX, and the documentation will not be in the code itself. Another thing I thought of is taking a picture of the mathematical notations, equations and diagrams written on paper/whiteboard, and including it in javadoc. Is there a simpler and clearer way? P.S. Giving descriptive names(timeOfFirstEvent instead of t1) to the variables actually makes the code more verbose and even harder too read.

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  • Doubts about several best practices for rest api + service layer

    - by TheBeefMightBeTough
    I'm going to be starting a project soon that exposes a restful api for business intelligence. It may not be limited to a restful api, so I plan to delegate requests to a service layer that then coordinates multiple domain objects (each of which have business logic local to the object). The api will likely have many calls as it is a long-term project. While thinking about the design, I recalled a few best practices. 1) Use command objects at the controller layer (I'm using Spring MVC). 2) Use DTOs at the service layer. 3) Validate in both the controller and service layer, though for different reasons. I have my doubts about these recommendations. 1) Using command objects adds a lot of extra single-purpose classes (potentially one per request). What exactly is the benefit? Annotation based validation can be done using this approach, sure. What if I have two requests that take the same parameters, but have different validation requirements? I would have to have two different classes with exactly the same members but different annotations? Bleh. 2) I have heard that using DTOs is preferable to parameters because it makes for more maintainable code down the road (say, e.g., requirements change and the service parameters need to be altered). I don't quite understand this. Shouldn't an api be more-or-less set in stone? I would understand that in the early phases of a project (or, especially, an entire company) the domain itself will not be well understood, and thus core domain objects may change along with the apis that manipulate these objects. At this point however the number of api methods should be small and their dependents few, so changes to the methods could easily be tolerated from a maintainability standpoint. In a large api with many methods and a substantial domain model, I would think having a DTO for potentially each domain object would become unwieldy. Am I misunderstanding something here? 3) I see validation in the controller and service layer as redundant in most cases. Why would I validate that parameters are not null and are in general well formed in the controller if the service is going to do exactly the same (and more). Couldn't I just do all the validation in the service and throw a runtime exception with a list of bad parameters then catch that in the controller to make the error messages more presentable? Better yet, couldn't I just make the error messages user-friendly in the service and let the exception trickle up to a global handler (ControllerAdvice in spring, for example)? Is there something wrong with either of these approaches? (I do see a use case for controller validation if the input does not map one-to-one with the service input, but since the controllers are for a rest api and not forms, the api parameters will probably map directly to service parameters.) I do also have a question about unchecked vs checked exceptions. Namely, I'm not really sure why I'd ever want to use a checked exception. Every time I have seen them used they just get wrapped into general exceptions (DomainException, SystemException, ApplicationException, w/e) to reduce the signature length of methods, or devs catch Exception rather than dealing with the App1Exception, App2Exception, Sys1Exception, Sys2Exception. I don't see how either of these practices is very useful. Why not just use unchecked exceptions always and catch the ones you actually do care about? You could just document what unchecked exceptions the method throws.

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  • Novice prototyping a massive multiplayer webpage based gaming system

    - by Sean Hendlin
    I'm trying to build a website based game in which various pages of the site act as different areas of the game. I am wondering what you would recommended as a design structure. Which languages would be best if building what will hopefully becomes a massive system able to scale to massive amounts of users. I am wondering if and how various elements from differing languages could be meshed to interact with each other. For example could I use html5, javascript, and PHP? What about asp.net how might that factor in? I'm a newbie programmer but I've been working on this idea for years and I want to build it to reality. Your comments and suggestions are appreciated. P.S.: The game is not all graphics and animation (though flash like appearance and some animation would be nice). What I am thinking of is essentially a heavily gamified system of forms. And LOTS of data in many different categories cross referencing each-other. I'm not sure how to go about structuring the collection of data. Also while I know javascript can be used to process some functions, I'm wondering what sort of base system I would need to handle the server side processing of what I am expecting to be some pretty significant algorithm processing. That is to say I expect to have many many many functions and I'm not sure how to mange this using javascript. I feel like they would be forgotten, mixed up, disorganizes as they essentially only exist where they are coded. I guess I need to learn something of libraries? OK, Thank you! Is enough from me for now.

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  • If-Else V.S. Switch end of flow

    - by Chris Okyen
    I was wondering the if if-else statements, is like a switch statement that does not have a break statement.To clarify with an example, will the if-else statement go through all the boolean expressions even if comes to one that is true before the final one... I.E., if boolean_expression_1 was true, would it check if boolean_expression_2 is true? If not, why do switch statements need break statements but if-else statements do not? And if they do, I ask the opposite sort question proposed in the previous sentence. if( boolean_expression_1 ) statement_1 else if( boolean_expression_2 ) statement_2 else default_statement switch( controlling_expression ) { case: ( A ) .... case: ( z ) }

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  • Euler angles to Cartesian Coordinates for use with gluLookAt

    - by notrodash
    I have searched all of the internet but just couldn't find the answer. I am using LibGDX and this is part of my code that loops over and over: public void render() { GL11 gl = Gdx.gl11; float centerX = (float)Math.cos(yaw) * (float)Math.cos(pitch); float centerY = (float)Math.sin(yaw) * (float)Math.cos(pitch); float centerZ = (float)Math.sin(pitch); System.out.println(centerX+" "+centerY+" "+centerZ+" ~ "+GDXRacing.camera.position.x+" "+GDXRacing.camera.position.y+" "+GDXRacing.camera.position.z); Gdx.glu.gluLookAt(gl, GDXRacing.camera.position.x, GDXRacing.camera.position.y, GDXRacing.camera.position.z, centerX, centerY, centerZ, 0, 1, 0); if(Gdx.input.isKeyPressed(Keys.A)) { yaw--; } if(Gdx.input.isKeyPressed(Keys.D)) { yaw++; } } I might just be bad at the math, but I dont get it. Does someone have a good explanation and an idea about how to deal with this? I am trying to make a first person camera. By the way, the camera is translated by +10 on the Z axis. Currently when I run the application, this is what I get: Watch video in browser | Download video (for those who cant download the video, everything shakes in a clockwise/anticlockwise action, depending on if I increase or decrease the Yaw value) -Thank you. [edit] and with this code: public void render() { GL11 gl = Gdx.gl11; float centerX = (float)(MathUtils.cosDeg(yaw)*4); float centerY = 0; float centerZ = (float)(MathUtils.sinDeg(yaw)*4); System.out.println(centerX+" "+centerY+" "+centerZ+" ~ "+GDXRacing.camera.position.x+" "+GDXRacing.camera.position.y+" "+GDXRacing.camera.position.z); Gdx.glu.gluLookAt(gl, GDXRacing.camera.position.x, GDXRacing.camera.position.y, GDXRacing.camera.position.z, centerX, centerY, centerZ, 0, 1, 0); if(Gdx.input.isKeyPressed(Keys.A)) { yaw--; } if(Gdx.input.isKeyPressed(Keys.D)) { yaw++; } } it slowly swings from the left to the right. This approach worked for turning left and right for 2d games though. What am I doing wrong?

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  • The clean coders videos [closed]

    - by Sebastian
    As many others, I have been reading Uncle Bob Martins books. More specifically, clean code and then "the clean coder". Now, over the last year he has been producing "code casts" that you can buy for ~20USD a piece. I bought the first episode sometime in mid 2011 and wasnt that impressed, as I really learned nothing new after reading his books. Last night I bought the first episode of test driven development with more or less the same result as last time. Now tonight I gave it one more go and bought TDD part 2 and this one was, IMO, really good. With this post I would like to tip others about his videos and would also like to know what others think. BR Sebastian

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  • Studies on code documentation productivity gains/losses

    - by J T
    Hi everyone, After much searching, I have failed to answer a basic question pertaining to an assumed known in the software development world: WHAT IS KNOWN: Enforcing a strict policy on adequate code documentation (be it Doxygen tags, Javadoc, or simply an abundance of comments) adds over-head to the time required to develop code. BUT: Having thorough documentation (or even an API) brings with it productivity gains (one assumes) in new and seasoned developers when they are adding features, or fixing bugs down the road. THE QUESTION: Is the added development time required to guarantee such documentation offset by the gains in productivity down-the-road (in a strictly economical sense)? I am looking for case studies, or answers that can bring with them objective evidence supporting the conclusions that are drawn. Thanks in advance!

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  • How to manage my model

    - by Christophe Debove
    I have in my model, a list of Classes : Player, NonPlayerCharacter, Monster, Item, NonMovableItem etc With AndEngine I've a list of sprite for each piece of my model, How can I manage the relashionship between my model's classes and the graphical elements, what is the degree of abstaction recommended for my problem? One sprite for one Model or one Model for one Sprite or n for n for exemple If I do drag&drop have I to make abstraction of the Sprite Class, another exemple a map is a List of sprite or a list of element of my model?

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  • Get coordinates of arraylist

    - by opiop65
    Here's my map class: public class map{ public static final int CLEAR = 0; public static final ArrayList<Integer> STONE = new ArrayList<Integer>(); public static final int GRASS = 2; public static final int DIRT = 3; public static final int WIDTH = 32; public static final int HEIGHT = 24; public static final int TILE_SIZE = 25; // static int[][] map = new int[WIDTH][HEIGHT]; ArrayList<ArrayList<Integer>> map = new ArrayList<ArrayList<Integer>>(WIDTH * HEIGHT); enum tiles { air, grass, stone, dirt } Image air, grass, stone, dirt; Random rand = new Random(); public Map() { /* default map */ /*for(int y = 0; y < WIDTH; y++){ map[y][y] = (rand.nextInt(2)); System.out.println(map[y][y]); }*/ /*for (int y = 18; y < HEIGHT; y++) { for (int x = 0; x < WIDTH; x++) { map[x][y] = STONE; } } for (int y = 18; y < 19; y++) { for (int x = 0; x < WIDTH; x++) { map[x][y] = GRASS; } } for (int y = 19; y < 20; y++) { for (int x = 0; x < WIDTH; x++) { map[x][y] = DIRT; } }*/ for (int y = 0; y < HEIGHT; y++) { for(int x = 0; x < WIDTH; x++){ map.set(x * WIDTH + y, STONE); } } try { init(null, null); } catch (SlickException e) { e.printStackTrace(); } render(null, null, null); } public void init(GameContainer gc, StateBasedGame sbg) throws SlickException { air = new Image("res/air.png"); grass = new Image("res/grass.png"); stone = new Image("res/stone.png"); dirt = new Image("res/dirt.png"); } public void render(GameContainer gc, StateBasedGame sbg, Graphics g) { for (int x = 0; x < WIDTH; x++) { for (int y = 0; y < HEIGHT; y++) { switch (map.get(x * WIDTH + y)) { case CLEAR: air.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case STONE: stone.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case GRASS: grass.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case DIRT: dirt.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; } } } } public static boolean blocked(float x, float y) { return map[(int) x][(int) y] == STONE; } public static Rectangle blockBounds(int x, int y) { return (new Rectangle(x, y, TILE_SIZE, TILE_SIZE)); } } Specifically I am looking at this: for (int x = 0; x < WIDTH; x++) { for (int y = 0; y < HEIGHT; y++) { switch (map.get(x * WIDTH + y).intValue()) { case CLEAR: air.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case STONE: stone.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case GRASS: grass.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case DIRT: dirt.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; } } } How can I access the coordinates of my arraylist map and then draw the tiles to the screen? Thanks!

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