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  • 12c und keine Ahnung? - Experten stehen Rede und Antwort auf Oracle-12c-Launch-Events

    - by Anne Manke
    Jetzt ist sie raus - die neue Oracle Datenbankversion 12c ist veröffentlicht. Auf unseren Oracle-12c-Launch-Events im Juli und August können Sie sich mit dieser neuen und innovativen Datenbankversion vertraut machen, und alles über die neuesten Funktionen und Features erfahren.  Referenten und Datenbankexperten stehen Ihnen Rede und Antwort zum Thema Oracle 12c. Melden Sie sich gleich hier für die kostenlosen Workshops an!  Datum  Stadt Anmeldung & Agenda 18. Juli 2013 Köln Event in Köln - hier anmelden! 13. August 2013 Hamburg Event in Hamburg - hier anmelden!

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  • Whether to separate out methods or not

    - by Skippy
    I am new to java and want to learn best coding practices and understand why one method is better than another, in terms of efficiency and as the coding becomes more complicated. This is just an example, but I can take the principles from here to apply elsewhere. I have need an option to display stuff, and have put the method stuff separately from the method to ask if the user wants to display the stuff, as stuff has a lot of lines of code. For readability I have done this: public static void displayStuff () { String input = getInput ("Display stuff? Y/N \n"); if (input..equalsIgnoreCase ("Y")) { stuff (); } else if (input.equalsIgnoreCase ("N")) { //quit program } else { //throw error System.out.print("Error! Enter Y or N: \n"); } } private static String stuff () { //to lots of things here return stuff (); } Or public static void displayStuff () { String input = getInput ("Display stuff? Y/N \n"); if (input..equalsIgnoreCase ("Y")) { //to lots of things here stuff; } else if (input.equalsIgnoreCase ("N")) { //quit program } else { //throw error System.out.print("Error! Enter Y or N: \n"); } } Is it better to keep them together and why? Also, should the second method be private or public, if I am asking for data within the class? I am not sure if this is on topic for here. please advise.

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  • Designing business objects, and gui actions

    - by fozz
    Developing a product ordering system using Java SE 6. The previous implementations used combo boxes, text fields, and check boxes. Preforming validation on action events from the GUI. The validation includes limiting existing combo boxes items, or even availability. The issue in the old system was that the action was received and all rules were applied to the entire business object. This resulted in a huge event change as options were changed multiple times. To be honest I have no idea how an infinite loop wasn't produced. Through the next iteration I stepped in and attempted to limit the chaos by controlling the order in which the selections could be made. Making configuration of BO's a top down approach. I implemented custom box models, action events, beans/binding, and an MVC pattern. However I still am unable to fully isolate action even chains. I'm thinking that I've approached the whole concept backwards in an attempt to stay closest to what was already in place. So the question becomes what do I design instead? I'm currently considering an implementation of Interfaces, Beans, Property Change Listeners to manage the back and forth. Other thoughts were validation exceptions, dynamic proxies.... I'm sure there are a ton of different ways. To say that one way is right is crazy, and I'm sure it will take a blending of multiple patterns. My knowledge of swing/awt validation is limited, previously I did backend logic only. Other considerations are were some sort of binding(jgoodies or otherwise) to directly bind GUI state to BO's.

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  • How to focus on one topic? [closed]

    - by Brian
    I have a huge problem while reading computer books. Every couple pages I'll end up googling something I want to learn more about, but then I'll find something on that page that I'll want to learn more about and google that (sometimes programming related, sometime hardware related). Normally after wasting around 3 hours going into different subjects I'll return to the original text only to repeat the process a few pages later. Any advice for sticking to one subject and learning that in-depth? I have tons of programming books I've read half-way through since I'll become interested in other languages/topics (not that I'm not interested in the books I've started). Also, what would be worth focusing on in depth? I've gone into Python in the most depth but for classes I'm learning Java and assembly (ARM and Motorola 68000). Also, I've taken a class on C++. Lately I've been spending most of my time learning about Linux instead of programming though. I'm not sure what would be worth focusing on the most to get a job. In other words, how can you focus on one topic and not let curiosity about everything else get in the way? Thanks in advance, Brian

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  • MVC: How to Implement Linked Views?

    - by cw'
    I'm developing a java application to visualize time series. I need (at least) three linked views, meaning that interaction with one of them updates the others. The views are: A list represents the available and currently selected time series. The selected time series are used as input for subsequent computations. Changing the selection should update the other views. A line chart displays the available and selected time series. Time series should be selectable from here by clicking on them. A bar chart shows aggregated data on time series. When zooming in to a period of time, the line chart should zoom in to the same period (and vice versa). How to implement this nicely, from a software engineering point of view? I.e. I'd like to write reusable and clear, maintainable code. So I thought of the MVC pattern. At first I liked the idea of having the three view components observing my model class and to refresh views upon being notified. But then, it didn't feel right to store view related data in the model. Storing e.g. the time series selection or plot zoom level in the model makes implications about the view which I wouldn't want in a reusable model. On the other hand, having the controllers observe each other results in a lot of dependencies. When adding another view, I'd have to register all other views as observer of the new view and vice versa, passing around many references and introducing dependencies. Maybe another "model" storing only view-related data would be the solution?

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  • Proper method to update and draw from game loop?

    - by Lost_Soul
    Recently I've took up the challenge for myself to create a basic 2d side scrolling monster truck game for my little brother. Which seems easy enough in theory. After working with XNA it seems strange jumping into Java (which is what I plan to program it in). Inside my game class I created a private class called GameLoop that extends from Runnable, then in the overridden run() method I made a while loop that handles time and such and I implemented a targetFPS for drawing as well. The loop looks like this: @Override public void run() { long fpsTime = 0; gameStart = System.currentTimeMillis(); lastTime = System.currentTimeMillis(); while(game.isGameRunning()) { currentTime = System.currentTimeMillis(); long ellapsedTime = currentTime - lastTime; if(mouseState.leftIsDown) { que.add(new Dot(mouseState.getPosition())); } entities.addAll(que); game.updateGame(ellapsedTime); fpsTime += ellapsedTime; if(fpsTime >= (1000 / targetedFPS)) { game.drawGame(ellapsedTime); } lastTime = currentTime; } The problem I've ran into is adding of entities after a click. I made a class that has another private class that extends MouseListener and MouseMotionListener then on changes I have it set a few booleans to tell me if the mouse is pressed or not which seems to work great but when I add the entity it throws a CME (Concurrent Modification Exception) sometimes. I have all the entities stored in a LinkedList so later I tried adding a que linkedlist where I later add the que to the normal list in the update loop. I think this would work fine if it was just the update method in the gameloop but with the repaint() method (called inside game.drawGame() method) it throws the CME. The only other thing is that I'm currently drawing directly from the overridden paintComponent() method in a custom class that extends JPanel. Maybe there is a better way to go about this? As well as fix my CME? Thanks in advance!!!

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  • To PHP or Not to PHP? [closed]

    - by Vad
    Should I learn PHP in depth for my smaller projects or not? My main knowledge is Java/JavaScript for the web. My old small projects were written in classic ASP. However, ASP had its days. Now I am looking into going deeper with another scripting language which I can use for small website projects. Though I know PHP on a basic level I never liked PHP. But I have to admit it is so widely used that I better start liking it. And all hosting services offer mostly PHP solutions. However, there is quite a number of issues with PHP when I google for it. Developers seem to not like it a lot. I wish I would use server-side JavaScript for all my needs, but hosting is an issue plus many small businesses already want to improve their existing PHP sites. And lastly, say I want to create a web app for distribution. PHP sounds like the best bet. Or am I wrong?

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  • Unit testing to prove balanced tree

    - by Darrel Hoffman
    I've just built a self-balancing tree (red-black) in Java (language should be irrelevant for this question though), and I'm trying to come up with a good means of testing that it's properly balanced. I've tested all the basic tree operations, but I can't think of a way to test that it is indeed well and truly balanced. I've tried inserting a large dictionary of words, both pre-sorted and un-sorted. With a balanced tree, those should take roughly the same amount of time, but an unbalanced tree would take significantly longer on the already-sorted list. But I don't know how to go about testing for that in any reasonable, reproducible way. (I've tried doing millisecond tests on these, but there's no noticeable difference - probably because my source data is too small.) Is there a better way to be sure that the tree is really balanced? Say, by looking at the tree after it's created and seeing how deep it goes? (That is, without modifying the tree itself by adding a depth field to each node, which is just wasteful if you don't need it for anything other than testing.)

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  • How to properly multi thread an RPG

    - by Nagrom_17
    I am working on an RPG type game in Java and I would like to know a few things relating to threading, What is the best way to implement a "wait for this then do this" without hanging the whole thread? Like waiting for a player to move to a location then pick up an item? or to wait one second then attack? Currently I am spawning new threads every time I need to wait for something, but that doesn't feel like the best solution. Any help is appreciated. EDIT: Clarification and an example of how I currently do things. User clicks on an item The function walkToAndPickUp(item) is called which is basically this: Make a new thread so we don't freeze the thread handling input while the player moves. Tell player to move to the item While the player is not at the item(The player moves through an update() function called in a different thread, I don't know how else to do it without freezing threads) Repeat until the player is at the item If the player is at the item then call delete item from map and add to inventory.

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  • Making a class pseudo-immutable by setting a flag

    - by scott_fakename
    I have a java project that involves building some pretty complex objects. There are quite a lot (dozens) of different ones and some of them have a HUGE number of parameters. They also need to be immutable. So I was thinking the builder pattern would work, but it ends up require a lot of boilerplate. Another potential solution I thought of was to make a mutable class, but give it a "frozen" flag, a-la ruby. Here is a simple example: public class EqualRule extends Rule { private boolean frozen; private int target; public EqualRule() { frozen = false; } public void setTarget(int i) { if (frozen) throw new IllegalStateException( "Can't change frozen rule."); target = i; } public int getTarget() { return target; } public void freeze() { frozen = true; } @Override public boolean checkRule(int i) { return (target == i); } } and "Rule" is just an abstract class that has an abstract "checkRule" method. This cuts way down on the number of objects I need to write, while also giving me an object that becomes immutable for all intents and purposes. This kind of act like the object was its own Builder... But not quite. I'm not too excited, however, about having an immutable being disguised as a bean however. So I had two questions: 1. Before I go too far down this path, are there any huge problems that anyone sees right off the bat? For what it's worth, it is planned that this behavior will be well documented... 2. If so, is there a better solution? Thanks

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  • Updating the jump in game

    - by Luka Tiger
    I am making a Java game and I want my game to run the same on any FPS so I'm using time delta between each update. This is the update method of the Player: public void update(long timeDelta) { //speed is the movement speed of a player on X axis //timeDelta is expressed in nano seconds so I'm dividing it with 1000000000 to express it in seconds if (Input.keyDown(37)) this.velocityX -= speed * (timeDelta / 1000000000.0); if (Input.keyDown(39)) this.velocityX += speed * (timeDelta / 1000000000.0); if(Input.keyPressed(38)) { this.velocityY -= 6; } velocityY += g * (timeDelta/1000000000.0); //applying gravity move(velocityX, velocityY); /*this is method which moves a player according to velocityX and velocityY, and checking the collision */ this.velocityX = 0.0; } The strange thing is that when I have unlimited FPS (and update number) my player is jumping about 10 blocks. It jumps even higher when the FPS is increasing. If I limit FPS it is jumping 4 blocks. (BLOCK: 32x32) I have just realized that the problem is this: if(Input.keyPressed(38)) { this.velocityY -= 6; } I add -6 to velocityY which increases player's Y proportionally to the update number and not to the time. But I don't know how to fix this.

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  • Storing Tiled Level Data in J2ME game

    - by Alex
    I'm developing a J2ME game which uses tiled backgrounds for the levels. My question is how do I store this tile information in my game. At the moment it is stored as an array; with each number representing a different tile from the tile-sheet. This works well enough, however I don't like the fact that it is 'hard-coded' into the game because (at least in my opinion) it is harder to edit the levels, or design new ones. I was also thinking that it would be difficult if you wanted to add a 'level pack', I'm not sure on how this would be achieved though; it's not something I was planning on doing, I'm just curious. I was wondering if there was a way I could store level data in some external file and then load this in to the game. The problem is I don't know what the limitations are for J2ME regarding file I/O, can it read in any file like Java? I am aware of the RMS, but from my experience I don't think this would work (unless I am mistaken). Also, would loading the data in this way be too big a performance hit? Or is there another way I can achieve what I am trying to do. As I said, the way I have it at the moment works fine, and if this is the only viable option then it will suffice.

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  • Question on methods in Object Oriented Programming

    - by mal
    I’m learning Java at the minute (first language), and as a project I’m looking at developing a simple puzzle game. My question relates to the methods within a class. I have my Block type class; it has its many attributes, set methods, get methods and just plain methods. There are quite a few. Then I have my main board class. At the moment it does most of the logic, positioning of sprites collision detection and then draws the sprites etc... As I am learning to program as much as I’m learning to program games I’m curious to know how much code is typically acceptable within a given method. Is there such thing as having too many methods? All my draw functionality happens in one method, should I break this into a few ‘sub’ methods? My thinking is if I find at a later stage that the for loop I’m using to cycle through the array of sprites searching for collisions in the spriteCollision() method is inefficient I code a new method and just replace the old method calls with the new one, leaving the old code intact. Is it bad practice to have a method that contains one if statement, and place the call for that method in the for loop? I’m very much in the early stages of coding/designing and I need all the help I can get! I find it a little intimidating when people are talking about throwing together a prototype in a day too! Can’t wait until I’m that good!

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  • JCP Elections, JUG Candidates

    - by Tori Wieldt
    The JCP elections for the JCP Executive Committee (EC) have started today. The ratified candidates are:  Cinterion, Credit Suisse, Fujitsu and HP.The elected candidates are (9 candidates, 2 open seats):  Cisco Systems, CloudBees, Giuseppe Dell'Abate, Liferay, London Java Community, MoroccoJUG, North Sixty-One, Software AG, and Zero Turnaround. For community representation, the London Java Community is running for re-election. They have helped with JUGs participation on the JCP, and they need community votes to stay there doing great work! Also, the Morroco JUG is running for election for the first time.  Learn more about the JCP Elections, read the JCP Program Office blog "2012 EC Election Ballot open; Meet the Candidates Call Tomorrow." So, please, if you are a registered JCP member, don't forget to cast your vote!

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  • Android Game Development problem whith size and speed

    - by Charlton Santana
    I have been coding speed for an object. I have made it so the object will move from one end of the screen to another at a speed depending on the screen size, at the monemt I have made it so it will take one second to pass the screen. So i have worked out the speed in code but when I go to assign the speed it tells me to force close and i do not understand why. Here is the code: MainGame Code: @Override protected void onDraw(Canvas canvas) { setBlockSpeed(getWidth()); } private int blockSpeed; private void setBlockSpeed(int screenWidth){ Log.d(TAG, "screenWidth " + screenWidth); blockSpeed = screenWidth / 100; // 100 is the FPS.. i want it to take 1 second to pass the screen Math.round(blockSpeed); // to make it a whole number block.speed = blockSpeed; // if i dont put blockSpeed and put eg 8 it still tells me to force close } Block.java Code: public int speed; public void draw(Canvas canvas) { canvas.drawBitmap(bitmap, x - (bitmap.getWidth() / 2), y - (bitmap.getHeight() / 2), null); if(dontmove == 0){ this.x -= speed; } }

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  • KC Java Users Group Presentation

    - by rodelljr
    Originally posted on: http://geekswithblogs.net/rodelljr/archive/2014/08/22/kc-java-users-group-presentation.aspxI would like to thank the KC Java Users Group for allowing me to do my presentation; Supporting Multiple Devices Part 2. In this talk, I discussed a Master/Detail application that runs on Android 2.2 devices and forward. I used the Actionbar compat Android library to allow the older devices to have an actionbar. I also used a SQLite database for my data. And just to add one last thing, I also incorporated the use of custom fonts. If you are interesting in looking at this sample application, I have uploaded it to my GitHub account here. I also have a Power Point presentation which you can get here.

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  • Why can't WARs share session info?

    - by rvcoutinho
    I have seen several developers looking for a solution for this problem: accessing session information from a different WAR (even when inside the same EAR) - here are some samples: Any way to share session state between different applications in tomcat?, Access session of another web application, different WAR files, shared resources, Tomcat: How to share data between two applications?, What does the crossContext attribute do in Tomcat? Does it enable session sharing? and so on... From all I have searched, there are some specific solutions depending on the container, but it is somehow 'contrary to the specification'. I have also looked through Java EE specification without any luck on finding an answer. Some developers talk about coupling between web applications, but I tend to disagree. What is the reason one would keep WARs inside the same EAR if not coupling? EJBs, for instance, can be accessed locally (even if inside another EJB JAR within the same EAR). More specifically, one of my WARs handles authentication and authorization, and I would like to share this information with other WARs (in the same EAR). I have managed to work around similar problems before by packaging WARs as JARs and putting them into a singular WAR project (WEB-INF/lib). Yet I do not like this solution (it requires a huge effort on servlet naming and so on). And no solution has answered the first (and most important) question: Why can't WARs share session information?

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  • More efficient in range checking

    - by Mob
    I am going to use a specific example in my question, but overall it is pretty general. I use java and libgdx. I have a ship that moves through space. In space there is debris that the ship can tractor beam in and and harvest. Debris is stored in a list, and the object contains it own x and y values. So currently there is no way to to find the debris's location without first looking at the debris object. Now at any given time there can be a huge (1000+) amount of debris in space, and I figure that calculating the distance between the ship and every single piece of debris and comparing it to maximum tractor beam length is rather inefficient. I have thought of dividing space into sectors, and have each sector contain a list of every object in it. This way I could only check nearby sectors. However this essentially doubles memory for the list. (I would reference the same object so it wouldn't double overall. I am not CS major, but I doubt this would be hugely significant.) This also means anytime an object moves it has to calculate which sector it is in, again not a huge problem. I also don't know if I can use some sort of 2D MAP that uses x and y values as keys. But since I am using float locations this sounds more trouble than its worth. I am kind of new to programming games, and I imagined there would be some eloquent solution to this issue.

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  • Quaternions, Axis Angles and Rotation Matrices. Which of these should I use for FP Camera?

    - by Afonso Lage
    After 2 weeks of reading many math formulas and such I know what is a Quaternion, an Axis Angles and Matrices. I have made my own math libary (Java) to use on my game (LWJGL). But I'm really confused about all this. I want to have a 3D first person camera. The move (translation) is working fine but the rotation isnt working like I need. I need a camera to rotate arround world Axis and not about its own axis. But even using Quaternions, this doesnt work and no matter how much I read about Euler Angles, everybody says to me dont touch on it! This is a little piece of code that i'm using to make the rotation: Quaternion qPitch = Quaternion.createFromAxis(cameraRotate.x, 1.0f, 0.0f, 0.0f); Quaternion qYaw = Quaternion.createFromAxis(cameraRotate.y, 0.0f, 1.0f, 0.0f); this.multiplicate(qPitch.toMatrix4f().toArray()); this.multiplicate(qYaw.toMatrix4f().toArray()); Where this is a Matrix4f view matrix and cameraRotate is a Vector3f that just handle the angles to rotate obtained from mouse move. So I think I'm doing everything right: Translate the view Matrix Rotate the Move Matrix So, after reading all this, I just want to know: To obtain a correct first person camera rotate, I must need to use Quaternios to make the rotations, but how to rotate around world axis? Thanks for reading it. Best regards, Afonso Lage

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  • What is the most efficient way to add and remove Slick2D sprites?

    - by kirchhoff
    I'm making a game in Java with Slick2D and I want to create planes which shoots: int maxBullets = 40; static int bullet = 0; Missile missile[] = new Missile[maxBullets]; I want to create/move my missiles in the most efficient way, I would appreciate your advise: public void shoot() throws SlickException{ if(bullet<maxBullets){ if(missile[bullet] != null){ missile[bullet].resetLocation(plane.getCenterX(), plane.getCenterY(), plane.image.getRotation()); }else{ missile[bullet] = new Missile("resources/missile.png", plane.getCenterX(), plane.getCenterY(), plane.image.getRotation()); } }else{ bullet = 0; missile[bullet].resetLocation(plane.getCenterX(), plane.getCenterY(), plane.image.getRotation()); } bullet++; } I created the method resetLocation in my Missile class in order to avoid loading again the resource. Is it correct? In the update method I've got this to move all the missiles: if(bullet > 0 && bullet < maxBullets){ float hyp = 0.4f * delta; if(bullet == 1){ missile[0].move(hyp); }else{ for(int x = 0; x<bullet; x++){ missile[x].move(hyp); } } }

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