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  • Object desing problem for simple school application

    - by Aragornx
    I want to create simple school application that provides grades,notes,presence,etc. for students,teachers and parents. I'm trying to design objects for this problem and I'm little bit confused - because I'm not very experienced in class designing. Some of my present objects are : class PersonalData() { private String name; private String surename; private Calendar dateOfBirth; [...] } class Person { private PersonalData personalData; } class User extends Person { private String login; private char[] password; } class Student extends Person { private ArrayList<Counselor> counselors = new ArrayList<>(); } class Counselor extends Person { private ArrayList<Student> children = new ArrayList<>(); } class Teacher extends Person { private ArrayList<ChoolClass> schoolClasses = new ArrayList<>(); private ArrayList<Subject> subjects = new ArrayList<>(); } This is of course a general idea. But I'm sure it's not the best way. For example I want that one person could be a Teacher and also a Parent(Counselor) and present approach makes me to have two Person objects. I want that user after successful logging in get all roles that it has (Student or Teacher or (Teacher & Parent) ). I think I should make and use some interfaces but I'm not sure how to do this right. Maybe like this: interface Role { } interface TeacherRole implements Role { void addGrade( Student student, Grade grade, [...] ); } class Teacher implements TeacherRole { private Person person; [...] } class User extends Person{ ArrayList<Role> roles = new ArrayList<>(); } Please if anyone could help me to make this right or maybe just point me to some literature/article that covers practical objects design.

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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 to store multiple requirements with OR and AND?

    - by Cano
    Well I'm working on a personal project that needs to check if a user has met certain requirements, and they come in a form of Requirement: [c1 OR c2] AND [d1 OR d2] Requirement: [c1 AND c2] OR [d1 AND d2] Requirement: c1 AND any dn(n can be any integer) I'm just not sure how to store these sorts of requirements, I'm thinking of using another object to hold c1,c2,d1,d2....dn and OR, but that seems like a roundabout way of doing things. Is there a better method?

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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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  • 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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  • Should I implement an interface directly or have the superclass do it?

    - by c_maker
    Is there a difference between public class A extends AbstractB implements C {...} versus... public class A extends AbstractB {...} AbstractB implements C {...} I understand that in both cases, class A will end up conforming to the interface. In the second case, AbstractB can provide implementation for interface methods in C. Is that the only difference? If I do NOT want to provide an implementation for any of the interface methods in AbstractB, which style should I be using? Does using one or the other have some hidden 'documentation' purpose?

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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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  • 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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  • Handling commands or events that wait for an action to be completed afterwards

    - by virulent
    Say you have two events: Action1 and Action2. When you receive Action1, you want to store some arbitrary data to be used the next time Action2 rolls around. Optimally, Action1 is normally a command however it can also be other events. The idea is still the same. The current way I am implementing this is by storing state and then simply checking when Action2 is called if that specific state is there. This is obviously a bit messy and leads to a lot of redundant code. Here is an example of how I am doing that, in pseudocode form (and broken down quite a bit, obviously): void onAction1(event) { Player = event.getPlayer() Player.addState("my_action_to_do") } void onAction2(event) { Player = event.getPlayer() if not Player.hasState("my_action_to_do") { return } // Do something } When doing this for a lot of other actions it gets somewhat ugly and I wanted to know if there is something I can do to improve upon it. I was thinking of something like this, which wouldn't require passing data around, but is this also not the right direction? void onAction1(event) { Player = event.getPlayer() Player.onAction2(new Runnable() { public void run() { // Do something } }) } If one wanted to take it even further, could you not simply do this? void onPlayerEnter(event) { // When they join the server Player = event.getPlayer() Player.onAction1(new Runnable() { public void run() { // Now wait for action 2 Player.onAction2(new Runnable() { // Do something }) } }, true) // TRUE would be to repeat the event, // not remove it after it is called. } Any input would be wonderful.

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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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  • LIbgdx and android scaling

    - by petervaz
    Following my previous question, I decided to migrate my andengine game to libdgx to have the desktop option. The game assets were planned, at first, to use a 1080x600 resolution and I raised that to 1200x800 which is native for many tablets and would look better on monitors. I followed this blog aproach regarding aspect ratio, which worked nicely on the desktop version, but running the android version (on my smaller tablet), the background would still appear on the original size being cropped by the smaller screen size. How can I force the resize of the background (or for what matter, of everything) on android to fit the screen?

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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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  • Help with Meshes, and Shading

    - by Brian Diehr
    In a game I'm making in LibGdx, I wish to incorporate a ripple effect. I'm confused as to how I get access to the individual pixels on the screen, or any way to influence them (apart from what I can do with sprite batch). I have my suspicions that I have to do it through openGL, and it has something to do with apply a mesh? This brings me to my question, what exactly is a mesh? I've been working on my game for about half a year, and am doing great with the other aspects of the game, but I find this more advance stuff isn't as well documented. 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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  • 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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  • How to disguise a serverside mob as another?

    - by Shaun Wild
    I've been working a Minecraft sever mod and i want to be able to add a new entity to the server, but then make the server send the packets to the client, imitating another mob, for example.. Lets say say i have EntityPlayerNPC.class, what i want to do is have all of the packets that get sent to the client look like they are from that of another player which is on the player, therefore allowing me to add custom NPC's... Thinking about the theory i'm sure this can be done. I've tried looking around for where the packets are being sent from and whatnot, can anyone think up a solution? edit: i tried adding a new constructor to the Packet20NamedEntitySpawn class like so: public Packet20NamedEntitySpawn(String username, EntityLiving e){ this.entityId = 0; this.name = username; this.xPosition = MathHelper.floor_double(e.posX * 32.0D); this.yPosition = MathHelper.floor_double(e.posY * 32.0D); this.zPosition = MathHelper.floor_double(e.posZ * 32.0D); this.rotation = (byte)((int)(e.rotationYaw * 256.0F / 360.0F)); this.pitch = (byte)((int)(e.rotationPitch * 256.0F / 360.0F)); this.metadata = e.getDataWatcher(); } unfortunatley, that didn't work :(

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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 manage the images for my Desktop Application

    - by NonExistent
    What's the better way to manage the image files of my app? i've been thinking about the way that i do right now (save the image as a BLOB IN db), and i ask myself if would be better to manage the image as text in my DB, i mean, convert the image to hex(length of 500), then save in the db as text, and when calling it convert it from hex to image, or something like that, but what do you consider as an Experienced Progammer that is the better way? Maybe the question is too broad, but i need to know that, and nobody answers me anywhere...

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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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  • 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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  • Access Token Verification

    - by DecafCoder
    I have spent quite a few days reading up on Oauth and token based security measures for REST API's and I am currently looking at implementing an Oauth based authentication approach almost exactly like the one described in this post (OAuth alternative for a 2 party system). From what I understand, the token is to be verified upon each request to the resource server. This means the resource server would need to retrieve the token from a datastore to verify the clients token. Given this would have to happen upon every request I am concerned about the speed implications of hitting a datastore like MySQL or NoSQL upon every request just to verify the token. Is this the standard way to verify tokens by having them stored in a RDBMS or NoSQL database and retrieved upon each request? Or is it a suitable solution to have them cached (baring in mind that we are talking millions of users)?

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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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  • Where Are Multiple JUnit Test Methods Typically Placed in Code?

    - by Thunderforge
    I've just read the Vogella JUnit tutorial and found it very helpful in understanding how to use JUnit. However, I'm a bit confused about what the convention is for placing multiple test methods in code. The tutorial only places one test method in a class, then describes how you can use a test suite to group multiple test classes together. Does this mean that it's common practice for each test class to only have one test method and then test suites are used to chain them together? Or was that just unintended and instead common practice is to put multiple test methods in a class?

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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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  • What OO Design to use ( is there a Design Pattern )?

    - by Blundell
    I have two objects that represent a 'Bar/Club' ( a place where you drink/socialise). In one scenario I need the bar name, address, distance, slogon In another scenario I need the bar name, address, website url, logo So I've got two objects representing the same thing but with different fields. I like to use immutable objects, so all the fields are set from the constructor. One option is to have two constructors and null the other fields i.e: class Bar { private final String name; private final Distance distance; private final Url url; public Bar(String name, Distance distance){ this.name = name; this.distance = distance; this.url = null; } public Bar(String name, Url url){ this.name = name; this.distance = null; this.url = url; } // getters } I don't like this as you would have to null check when you use the getters In my real example the first scenario has 3 fields and the second scenario has about 10, so it would be a real pain having two constructors, the amount of fields I would have to declare null and then when the object are in use you wouldn't know which Bar you where using and so what fields would be null and what wouldn't. What other options do I have? Two classes called BarPreview and Bar? Some type of inheritance / interface? Something else that is awesome?

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