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  • which is better performance, using a disposable local variable or reusing a global one?

    - by petervaz
    This is for an android game. Suppose I have a function that is called several times for second and do some calculations involving an arraylist (or any other complex objects for what matter). Which approach would be preffered? local: private void doStuff(){ ArrayList<Type> XList = new ArrayList<Type>(); // do stuff with list } global: private ArrayList<Type> XList = new ArrayList<Type>(); private void doStuff(){ XList.clear(); // do stuff with list }

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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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  • How can I perform sentiment analysis on extracted text from online sources?

    - by aniket69
    I'm working on extracting the sentiment from YouTube comments, blogs, news content, Facebook wall posts, and Twitter feeds. I'm looking for an automated way to do this: the two third-party solutions I've found have been AlchemyAPI and RapidMiner. Are these the best way to approach this project, or should I be using something else? Is there a more efficient way to approach sentiment analysis? What techniques have worked for you in a project like this?

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  • Multidimensional multiple-choice knapsack problem: find a feasible solution

    - by Onheiron
    My assignment is to use local search heuristics to solve the Multidimensional multiple-choice knapsack problem, but to do so I first need to find a feasible solution to start with. Here is an example problem with what I tried so far. Problem R1 R2 R3 RESOUCES : 8 8 8 GROUPS: G1: 11.0 3 2 2 12.0 1 1 3 G2: 20.0 1 1 3 5.0 2 3 2 G3: 10.0 2 2 3 30.0 1 1 3 Sorting strategies To find a starting feasible solution for my local search I decided to ignore maximization of gains and just try to fit the resources requirements. I decided to sort the choices (strategies) in each group by comparing their "distance" from the multidimensional space origin, thus calculating SQRT(R1^2 + R2^2 + ... + RN^2). I felt like this was a keen solution as it somehow privileged those choices with resouce usages closer to each other (e.g. R1:2 R2:2 R3:2 < R1:1 R2:2 R3:3) even if the total sum is the same. Doing so and selecting the best choice from each group proved sufficent to find a feasible solution for many[30] different benchmark problems, but of course I knew it was just luck. So I came up with the problem presented above which sorts like this: R1 R2 R3 RESOUCES : 8 8 8 GROUPS: G1: 12.0 1 1 3 < select this 11.0 3 2 2 G2: 20.0 1 1 3 < select this 5.0 2 3 2 G3: 30.0 1 1 3 < select this 10.0 2 2 3 And it is not feasible because the resources consmption is R1:3, R2:3, R3:9. The easy solution is to pick one of the second best choices in group 1 or 2, so I'll need some kind of iteration (local search[?]) to find the starting feasible solution for my local search solution. Here are the options I came up with Option 1: iterate choices I tried to find a way to iterate all the choices with a specific order, something like G1 G2 G3 1 1 1 2 1 1 1 2 1 1 1 2 2 2 1 ... believeng that feasible solutions won't be that far away from the unfeasible one I start with and thus the number of iterations will keep quite low. Does this make any sense? If yes, how can I iterate the choices (grouped combinations) of each group keeping "as near as possibile" to the previous iteration? Option 2: Change the comparation term I tried to think how to find a better variable to sort the choices on. I thought at a measure of how "precious" a resource is based on supply and demand, so that an higer demand of a more precious resource will push you down the list, but this didn't help at all. Also I thought there probably isn't gonna be such a comparsion variable which assures me a feasible solution at first strike. I there such a variable? If not, is there a better sorting criteria anyways? Option 3: implement any known sub-optimal fast solving algorithm Unfortunately I could not find any of such algorithms online. Any suggestion?

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  • When attaching AI to a vehicle should I define all steps or try Line of Sight?

    - by ThorDivDev
    This problem is related to an intersection simulation I am building for university. I will try to make it as general as possible. I am trying to assign AI to a vehicle using the JMonkeyEngine platform. AIGama_JmonkeyEngine explains that if you wish to create a car that follows a path you can define the path in steps. If there was no physics attached whatsoever then all you need to do is define the x,y,z values of where you want the object to appear in all subsequent steps. I am attaching the vehicleControl that implements jBullet. In this case the author mentions that I would need to define the steering and accelerating behaviors at each step. I was trying to use ghost controls that represented waypoints and when on colliding the car would decide what to do next like stopping at a red light. This didn't work so well. Car doesn't face right. public void update(float tpf) { Vector3f currentPos = aiVehicle.getPhysicsLocation(); Vector3f baseforwardVector = currentPos.clone(); Vector3f forwardVector; Vector3f subsVector; if (currentState == ObjectState.Running) { aiVehicle.accelerate(-800); } else if (currentState == ObjectState.Seeking) { baseforwardVector = baseforwardVector.normalize(); forwardVector = aiVehicle.getForwardVector(baseforwardVector); subsVector = pointToSeek.subtract(currentPos.clone()); System.out.printf("baseforwardVector: %f, %f, %f\n", baseforwardVector.x, baseforwardVector.y, baseforwardVector.z); System.out.printf("subsVector: %f, %f, %f\n", subsVector.x, subsVector.y, subsVector.z); System.out.printf("ForwardVector: %f, %f, %f\n", forwardVector.x, forwardVector.y, forwardVector.z); if (pointToSeek != null && pointToSeek.x + 3 >= currentPos.x && pointToSeek.x - 3 <= currentPos.x) { aiVehicle.steer(0.0f); aiVehicle.accelerate(-40); } else if (pointToSeek != null && pointToSeek.x > currentPos.x) { aiVehicle.steer(-0.5f); aiVehicle.accelerate(-40); } else if (pointToSeek != null && pointToSeek.x < currentPos.x) { aiVehicle.steer(0.5f); aiVehicle.accelerate(-40); } } else if (currentState == ObjectState.Stopped) { aiVehicle.accelerate(0); aiVehicle.brake(40); } }

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  • Matrix loading problems with jbullet and lwjgl

    - by Quintin
    The following code does not load the matrix correctly from jbullet. //box is a RigidBody Transform trans = new Transform(); trans = box.getMotionState().getWorldTransform(trans); float[] matrix = new float[16]; trans.getOpenGLMatrix(matrix); // pass that matrix to OpenGL and render the cube FloatBuffer buffer = ByteBuffer.allocateDirect(4*16).asFloatBuffer().put(matrix); buffer.rewind(); glPushMatrix(); glMultMatrix(buffer); glBegin(GL_POINTS); glVertex3f(0,0,0); glEnd(); glPopMatrix(); the jbullet is configured as so: CollisionConfiguration = new DefaultCollisionConfiguration(); dispatcher = new CollisionDispatcher(collisionConfiguration); Vector3f worldAabbMin = new Vector3f(-10000,-10000,-10000); Vector3f worldAabbMax = new Vector3f(10000,10000,10000); AxisSweep3 overlappingPairCache = new AxisSweep3(worldAabbMin, worldAabbMax); SequentialImpulseConstraintSolver solver = new SequentialImpulseConstraintSolver(); dynamicWorld = new DiscreteDynamicsWorld(dispatcher, overlappingPairCache, solver, collisionConfiguration); dynamicWorld.setGravity(new Vector3f(0,-10,0)); dynamicWorld.getDispatchInfo().allowedCcdPenetration = 0f; CollisionShape groundShape = new BoxShape(new Vector3f(1000.f, 50.f, 1000.f)); Transform groundTransform = new Transform(); groundTransform.setIdentity(); groundTransform.origin.set(new Vector3f(0.f, -60.f, 0.f)); float mass = 0f; Vector3f localInertia = new Vector3f(0, 0, 0); DefaultMotionState myMotionState = new DefaultMotionState(groundTransform); RigidBodyConstructionInfo rbInfo = new RigidBodyConstructionInfo(mass, myMotionState, groundShape, localInertia); RigidBody body = new RigidBody(rbInfo); dynamicWorld.addRigidBody(body); dynamicWorld.clearForces(); Nothing is rendered on the screen. What am I doing wrong?

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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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  • 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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  • Bitmap rotation jitter around pivot

    - by Manderin87
    I am working on a asteriods clone and I have the ship graphic loaded as a 96x96 bitmap. When the player rotates the ship I rotate the bitmap by degree (float). rotation function: if(m_Matrix == null) { m_Matrix = new Matrix(); } else { m_Matrix.reset(); } m_Matrix.setRotate(degree, m_BaseImage.getWidth() / 2, m_BaseImage.getHeight() / 2); m_RotatedImage = Bitmap.createBitmap(m_BaseImage, 0, 0, m_BaseImage.getWidth(), m_BaseImage.getHeight(), m_Matrix, true); draw function: m_Paint.setAntiAlias(true); m_Paint.setFilterBitmap(true); m_Paint.setDither(true); canvas.drawBitmap(m_RotatedImage, (int) posX - m_RotatedImage.getWidth() / 2, (int) posY - m_RotatedImage.getHeight() / 2, m_Paint); When the bitmap is drawn, the bitmap jitters slightly around the pivot. Can anyone fix or tell me why the bitmap is jittering around the pivot? It needs to be smooth.

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  • The input doesn't recognize that I release the key?

    - by joapet99
    I'm creating a window (JOptionPane), in response to a collision. However, if the player is holding a key down when the window pops up, the input doesn't trigger a key release when the key is released. I don't think you can just check it with a isRelease function in the input, since the input is kind of corrupt. Can you help me? The way I check if the key is down: if(input.isKeyDown(Input.KEY_A)&& TestLevel.isFighting == false){ if(owner.canMoveLeft){ position.x -= speed * delta; } } I am not handling the key release by myself, but if I check if the key is down it should work. But it doesn't.

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  • Do threads delete themselves?

    - by Prog
    Let's say I was working on a Swing application. Most of it is run on the EDT using SwingUtilities.invokeLater() inside the main method, because I heard (please correct me if I'm wrong) that that's what you need to do with Swing. However, some parts of it shouldn't run on the EDT. These parts are parts that take long to complete (I assume that this is because long tasks on the EDT will interfere with GUI stuff the EDT should be doing, and thus these kinds of tasks should be run on parallel, on a different thread. Is this assumption correct?) To do this, when I need to perform a task that takes long to complete and thus can't be run on the EDT like the rest of the program, I create a new thread and run that task inside it. My question is: When the run() method of that new thread finishes, aka the thread finished it's job. Does it delete itself? Or does it keep existing in the memory?

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  • How to choose between Tell don't Ask and Command Query Separation?

    - by Dakotah North
    The principle Tell Don't Ask says: you should endeavor to tell objects what you want them to do; do not ask them questions about their state, make a decision, and then tell them what to do. The problem is that, as the caller, you should not be making decisions based on the state of the called object that result in you then changing the state of the object. The logic you are implementing is probably the called object’s responsibility, not yours. For you to make decisions outside the object violates its encapsulation. A simple example of "Tell, don't Ask" is Widget w = ...; if (w.getParent() != null) { Panel parent = w.getParent(); parent.remove(w); } and the tell version is ... Widget w = ...; w.removeFromParent(); But what if I need to know the result from the removeFromParent method? My first reaction was just to change the removeFromParent to return a boolean denoting if the parent was removed or not. But then I came across Command Query Separation Pattern which says NOT to do this. It states that every method should either be a command that performs an action, or a query that returns data to the caller, but not both. In other words, asking a question should not change the answer. More formally, methods should return a value only if they are referentially transparent and hence possess no side effects. Are these two really at odds with each other and how do I choose between the two? Do I go with the Pragmatic Programmer or Bertrand Meyer on this?

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  • Best Practice: What can be the hashCode() method implementation if custom field used in equals() method are null?

    - by goodspeed
    What is the best practice to return a value for hashCode() method if custom field used in equals are null ? I have a situation, where equals() override is implemented using custom fields. Usually it it is better to override hashCode() also using that custom fields used in equals(). But if all the custom fields used in equals() are null, then what would be the best implementation for hashCode()? Example: class Person { private String firstName; private String lastName; public String getFirstName() { return firstName; } public String getLastName() { return lastName; } @Override public boolean equals(Object object) { boolean result = false; if (object == null || object.getClass() != getClass()) { result = false; } else { Person person = (Person) object; if (this.firstName == person.getFirstName() && this.lastName == tiger.getLastName()) { result = true; } } return result; } @Override public int hashCode() { int hash = 3; if(this.firstName == null || this.lastName == null) { // <b>What is the best practice here, </b> // <b>is return super.hashCode() better ?</b> } hash = 7 * hash + this.firstName.hashCode(); hash = 7 * hash + this.lastName.hashCode(); return hash; } } is it required to check for null in hashCode() ? If yes, what should be returned if custom values are null ?

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  • Algorithms for Data Redundancy and Failover for distributed storage system?

    - by kennetham
    I'm building a distributed storage system that works with different storage sizes. For instance, my storage devices have sizes of 50GB, 70GB, 150GB, 250GB, 1000GB, 5 storage systems in one system. My application will store any files to the storage system. Question: How can I build a distributed storage with the idea of data redundancy and fail-over to store documents, videos, any type of files at the same time ensuring that should one of any storage devices fail, there would be another copy of these files on another storage device. However, the concern is, 50GB of storage can only store this maximum number of files as compared to 70GB, 150GB etc. With one storage in mind, bringing 5 storage systems like a cloud storage, is there any logical way to distribute or store the files through my application? How do I ensure data redundancy through different storage sizes? Is there any algorithm to collate multiple blob files into a single file archive? What is the best solution for one cloud storage with multiple different storage sizes? I open this topic with the objective of discussing the best way to implement this idea, assuming simplicity, what are the issues of this implementation, performance measurements and discussion of the limitations.

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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 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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  • Why do I get a blinking screen when running lwjgl?

    - by SystemNetworks
    I didn't have any errors. But When I run my lwjgl game, it gives me a blinking screen. Here is the code: package L1F3; import org.lwjgl.opengl.Display; import org.lwjgl.opengl.DisplayMode; import org.lwjgl.LWJGLException; import static org.lwjgl.opengl.GL11.*; public class Main { public static void main(String[] args) { try { Display.setDisplayMode(new DisplayMode(640, 480)); Display.setTitle("A fresh display!"); Display.create(); } catch (LWJGLException e) { e.printStackTrace(); Display.destroy(); System.exit(1); } while(!Display.isCloseRequested()) { Display.update(); } Display.destroy(); System.exit(0); } } How do I stop the blinking screen? I was thinking its my framerate. I deleted Display.sync but it still gives me all white and black. Last time it didn't give me a blinking screen. EDIT When I remove Display.update() , it gives me a perfect screen, no blinking or no white. Will my game work without it? I can also close it perfectly.

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  • Really weird GL Behaviour, uniform not "hitting" proper mesh? LibGdx

    - by HaMMeReD
    Ok, I got some code, and you select blocks on a grid. The selection works. I can modify the blocks to be raised when selected and the correct one shows. I set a color which I use in the shader. However, I am trying to change the color before rendering the geometry, and the last rendered geometry (in the sequence) is rendered light. However, to debug logic I decided to move the block up and make it white, in which case one block moves up and another block becomes white. I checked all my logic and it knows the correct one is selected and it is showing in, in the correct place and rendering it correctly. When there is only 1 it works properly. Video Of the bug in action, note how the highlighted and elevated blocks are not the same block, however the code for color and My Renderer is here (For the items being drawn) public void render(Renderer renderer) { mGrid.render(renderer, mGameState); for (Entity e:mGameEntities) { UnitTypes ut = UnitTypes.valueOf((String)e.getObject(D.UNIT_TYPE.ordinal())); if (ut == UnitTypes.Soldier) { renderer.testShader.begin(); renderer.testShader.setUniformMatrix("u_mvpMatrix",mEntityMatrix); renderer.texture_soldier.bind(0); Vector2 pos = (Vector2) e.getObject(D.COORDS.ordinal()); mEntityMatrix.set(renderer.mCamera.combined); if (mSelectedEntities.contains(e)) { mEntityMatrix.translate(pos.x, 1f, pos.y); renderer.testShader.setUniformf("v_color", 0.5f,0.5f,0.5f,1f); } else { mEntityMatrix.translate(pos.x, 0f, pos.y); renderer.testShader.setUniformf("v_color", 1f,1f,1f,1f); } mEntityMatrix.scale(0.2f, 0.2f, 0.2f); renderer.model_soldier.render(renderer.testShader,GL20.GL_TRIANGLES); renderer.testShader.end(); } else if (ut == UnitTypes.Enemy_Infiltrator) { renderer.testShader.begin(); renderer.testShader.setUniformMatrix("u_mvpMatrix",mEntityMatrix); renderer.testShader.setUniformf("v_color", 1.0f,1,1,1.0f); renderer.texture_enemy_infiltrator.bind(0); Vector2 pos = (Vector2) e.getObject(D.COORDS.ordinal()); mEntityMatrix.set(renderer.mCamera.combined); mEntityMatrix.translate(pos.x, 0f, pos.y); mEntityMatrix.scale(0.2f, 0.2f, 0.2f); renderer.model_enemy_infiltrator.render(renderer.testShader,GL20.GL_TRIANGLES); renderer.testShader.end(); } } }

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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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  • 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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  • How to dynamically override a method in an object

    - by Ace Takwas
    If this is possible, how can I change what a method does after I might have created an instance of that class and wish to keep the reference to that object but override a public method in it's class' definition? Here's my code: package time_applet; public class TimerGroup implements Runnable{ private Timer hour, min, sec; private Thread hourThread, minThread, secThread; public TimerGroup(){ hour = new HourTimer(); min = new MinuteTimer(); sec = new SecondTimer(); } public void run(){ hourThread.start(); minThread.start(); secThread.start(); } /*Please pay close attention to this method*/ private Timer activateHourTimer(int start_time){ hour = new HourTimer(start_time){ public void run(){ while (true){ if(min.changed)//min.getTime() == 0) changeTime(); } } }; hourThread = new Thread(hour); return hour; } private Timer activateMinuteTimer(int start_time){ min = new MinuteTimer(start_time){ public void run(){ while (true){ if(sec.changed)//sec.getTime() == 0) changeTime(); } } }; minThread = new Thread(min); return min; } private Timer activateSecondTimer(int start_time){ sec = new SecondTimer(start_time); secThread = new Thread(sec); return sec; } public Timer addTimer(Timer timer){ if (timer instanceof HourTimer){ hour = timer; return activateHourTimer(timer.getTime()); } else if (timer instanceof MinuteTimer){ min = timer; return activateMinuteTimer(timer.getTime()); } else{ sec = timer; return activateSecondTimer(timer.getTime()); } } } So for example in the method activateHourTimer(), I would like to override the run() method of the hour object without having to create a new object. How do I go about that?

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  • Lwjgl camera causing movement to be mirrored

    - by pangaea
    I'm having a problem in that everything is rendered and the movement is fine. However, everything seems to be mirrored. In the sense that the TriangleMob should move towards me, but it doesn't instead it mirrors my action. I move forward the TriangleMob moves backwards. I move left, it moves right. I move backwards, it moves forward. The code works if I do this glPushMatrix(); glTranslatef(-position.x, -position.y, -position.z); glCallList(objectDisplayList); glPopMatrix(); However, I'm scared this will cause a problem later on. I suppose the code works. However, shouldn't the call be glPushMatrix(); glTranslatef(position.x, position.y, position.z); glCallList(objectDisplayList); glPopMatrix(); I think the problem could be caused by how I'm doing the camera, which is this glLoadIdentity(); glRotatef(player.getRotation().x, 1.0f, 0.0f, 0.0f); glRotatef(player.getRotation().y, 0.0f, 1.0f, 0.0f); glRotatef(player.getRotation().z, 0.0f, 0.0f, 1.0f); glTranslatef(player.getPosition().x, player.getPosition().y, player.getPosition().z);

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  • Common Substring of two strings

    - by Chander Shivdasani
    This particular interview-question stumped me: Given two Strings S1 and S2. Find the longest Substring which is a Prefix of S1 and suffix of S2. Through Google, I came across the following solution, but didnt quite understand what it was doing. public String findLongestSubstring(String s1, String s2) { List<Integer> occurs = new ArrayList<>(); for (int i = 0; i < s1.length(); i++) { if (s1.charAt(i) == s2.charAt(s2.length()-1)) { occurs.add(i); } } Collections.reverse(occurs); for(int index : occurs) { boolean equals = true; for(int i = index; i >= 0; i--) { if (s1.charAt(index-i) != s2.charAt(s2.length() - i - 1)) { equals = false; break; } } if(equals) { return s1.substring(0,index+1); } } return null; }

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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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  • Grid collision - finding the location of an entity in each box

    - by Gregg1989
    I am trying to implement grid-based collision in a 2d game with moving circles. The canvas is 400x400 pixels. Below you can see the code for my Grid class. What I want it to do is check inside which box the entities are located and then run a collision check if there are 2 or more entities in the same box. Right now I do not know how to find the position of an entity in a specific box. I know there are many tutorials online, but I haven't been able to find an answer to my question, because they are either written in C/C++ or use the 2d array approach. Code snippets and other help is greatly appreciated. Thanks. public class Grid { ArrayList<ArrayList<Entity>> boxes = new ArrayList<>(); double boxSize = 40; double boxesAmount = 10; ... ... public void checkBoxLocation(ArrayList<Entity> entities) { for (int i = 0; i < entities.size(); i++) { // Get top left coordinates of each entity double entityLeft = entities.get(i).getLayoutX() - entities.get(i).getRadius(); double entityTop = entities.get(i).getLayoutY() + entities.get(i).getRadius(); // Divide coordinate by box size to find the approximate location of the entity for (int j = 0; j < boxesAmount; j++) { //Select each box if ((entityLeft / boxSize <= j + 0.7) && (entityLeft / boxSize >= j)) { if ((entityTop / boxSize <= j + 0.7) && (entityTop / boxSize >= j)) { holdingBoxes.get(j).add(entities.get(i)); System.out.println("Entity " + entities.get(i) + " added to box " + j); } } } } } }

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