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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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  • 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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  • Java-Powered Robot Named NAO Wows Crowds

    - by Tori Wieldt
    He drew a crowd where he went at JavaOne. And only being 22.5 inches/573 mm tall, that's pretty impressive. Nao (pronounced now) is an autonomous, programmable humanoid robot developed by Aldebaran Robotics, a French robotics company. Over 200 academic institutions worldwide have made use of the robot. In this video from JavaOne, Nicolas Rigaud shows off the NAO robot which you can control with Java. We are eager to see what Java developers can do with a robot that can walk, talk, see, hear, and dance. &amp;amp;amp;amp;amp;amp;lt;span id=&amp;amp;amp;amp;amp;amp;quot;XinhaEditingPostion&amp;amp;amp;amp;amp;amp;quot;&amp;amp;amp;amp;amp;amp;gt;&amp;amp;amp;amp;amp;amp;lt;/span&amp;amp;amp;amp;amp;amp;gt; You can see several pictures in the blog Aldebaran Robotics at JavaOne. Learn more about the Aldebaran robotics developer program.

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  • "Programming error" exceptions - Is my approach sound?

    - by Medo42
    I am currently trying to improve my use of exceptions, and found the important distinction between exceptions that signify programming errors (e.g. someone passed null as argument, or called a method on an object after it was disposed) and those that signify a failure in the operation that is not the caller's fault (e.g. an I/O exception). As far as I understand, it makes little sense for an immediate caller to actually handle programming error exceptions, he should instead assure that the preconditions are met. Only "outer" exception handlers at task boundaries should catch them, so they can keep the system running if a task fails. In order to ensure that client code can cleanly catch "failure" exceptions without catching error exceptions by mistake, I create my own exception classes for all failure exceptions now, and document them in the methods that throw them. I would make them checked exceptions in Java. Now I have a few questions: Before, I tried to document all exceptions that a method could throw, but that sometimes creates an unwiedly list that needs to be documented in every method up the call chain until you can show that the error won't happen. Instead, I document the preconditions in the summary / parameter descriptions and don't even mention what happens if they are not met. The idea is that people should not try to catch these exceptions explicitly anyway, so there is no need to document their types. Would you agree that this is enough? Going further, do you think all preconditions even need to be documented for every method? For example, calling methods in IDisposable objects after calling Dispose is an error, but since IDisposable is such a widely used interface, can I just assume a programmer will know this? A similar case is with reference type parameters where passing null makes no conceivable sense: Should I document "non-null" anyway? IMO, documentation should only cover things that are not obvious, but I am not sure where "obvious" ends.

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  • Une vulnérabilité importante de Java vient d'être découverte par un ingénieur de Google, Oracle la m

    Une faille de Java permettrait de prendre le contrôle d'une machine Oracle minimise la vulnérabilité découverte par un ingénieur de Google Un ingénieur de Google, Tavis Ormandy, vient de mettre à jour une faille de Java qui touche les versions Windows depuis la 6 update 10. Après avoir contacté Oracle, Ormandy a reçu pour réponse que la société "ne considère pas cette vulnérabilité suffisamment importante pour rompre le cycle trimestriel de réalisation des patchs". Une appréciation avec laquelle "il n'est pas d'accord". L'attaque que permet la faille est pourtant sérieuse puisqu'elle permet à un tiers de lancer un code malveillant et de pr...

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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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  • 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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  • Video: Coherence Community on Java.net - 4 Projects available under CDDL-1.0

    - by OTN ArchBeat
    If you work with Oracle Coherence and you're not familiar with the Coherence Community on Java.net you're missing out. The Coherence Community was launched on Java.net in June 2013, operating under the Open Source Initiative's Common Development and Distribution License (CDDL-1.0). Four projects are currently available for your participation: Coherence Hibernate Integration Coherence Spring Integration Oracle Tools The Coherence Incubator You'll learn a lot more about the Coherence Community in the video above, which features my conversation with Oracle Coherence Senior Principal Solutions Architect Brian Oliver and Oracle Coherence Consulting Solutions Architect Randy Stafford, two of the people behind the creation and management of the Community and it's projects.

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  • How can I draw crisp per-pixel images with OpenGL ES on Android?

    - by Qasim
    I have made many Android applications and games in Java before, however I am very new to OpenGL ES. Using guides online, I have made simple things in OpenGL ES, including a simple triangle and a cube. I would like to make a 2D game with OpenGL ES, but what I've been doing isn't working quite so well, as the images I draw aren't to scale, and no matter what guide I use, the image is always choppy and not the right size (I'm debugging on my Nexus S). How can I draw crisp, HD images to the screen with GL ES? Here is an example of what happens when I try to do it: And the actual image: Here is how my texture is created: //get id int id = -1; gl.glGenTextures(1, texture, 0); id = texture[0]; //get bitmap Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.ball); //parameters gl.glBindTexture(GL10.GL_TEXTURE_2D, id); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_NEAREST); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, GL10.GL_CLAMP_TO_EDGE); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, GL10.GL_CLAMP_TO_EDGE); gl.glTexEnvf(GL10.GL_TEXTURE_ENV, GL10.GL_TEXTURE_ENV_MODE, GL10.GL_REPLACE); GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap, 0); //crop image mCropWorkspace[0] = 0; mCropWorkspace[1] = height; mCropWorkspace[2] = width; mCropWorkspace[3] = -height; ((GL11) gl).glTexParameteriv(GL10.GL_TEXTURE_2D, GL11Ext.GL_TEXTURE_CROP_RECT_OES, mCropWorkspace, 0);

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  • Approach to retrieve files from server

    - by Aerus
    I'm in the process of making a Java application with a corresponding update application. At any given time the user may want to update the application and the updater will ask for a list of files of the latest release. Based on this list, the updater can determine which files need to be downloaded to complete the update. I now have 2 approaches to solve this, but i would like to know what approach will put the least stress on my application and server. I could send a list of files i want to download to my server and the server zips the files and simply returns this compressed file to the application. The updater sents a request for each seperate file to the server, which simply returns the file The application will be used mainly in Belgium and The Netherlands and connections/bandwidth tend to be pretty decent in here. The average size of a single file should be around 100Kb and at most 1Mb. I expect an update to have anywhere between 10 to 50 new files. I expect at most 100 persons/day to update the application, i.e. in the week when a new version is released. I hope this is enough information to sketch my problem and any advice is welcome. If there is another common way to tackle this, i'd be glad to hear it.

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  • Gigaom Article on Oracle, Freescale, and the push for Java on Internet of Things (IoT)

    - by hinkmond
    Here's an interesting article that came out during JavaOne which talks about the Oracle and Freescale partnership, where we are putting Java technology onto the Freescale i.MX6 based "one box" gateway. See: Oracle and Prosyst team up Here's a quote: When it comes to connected devices, there’s still plenty of debate over the right operating system, the correct protocols for sending data and even the basics of where processing will take place — on premise or in the cloud. This might seem esoteric, but if you’re waiting for your phone to unlock your front door, that round trip to the cloud or a fat OS isn’t going to win accolades if you’re waiting in the rain. With all of this in mind, Oracle and Freescale have teamed up to offer an appliance and a Java-based software stack for the internet of things. The first version of the "one box" will work in the connected smart home, but soon after that, Oracle and Freescale will develop later boxes for other industries ranging from healthcare, smart grid to manufacturing. Hinkmond

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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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  • [WebLogic, Java] WebLogic Developer/Production Web Profile, Full Java EE 6 Platform - Chat Transcript and Slides from OTN Virtual Developer Day

    - by yosuke.arai(at)oracle.com
    ????????????????????????WebLogic Server Virtual Developer Days??JavaEE6???????QA???????????????????(FireFox???????????????????????????????????????) ?????????????????????????????! > Q1) WLS10.3.4??JavaEE6????????????? > Q4) Java EE6 ???????IDE????????? > Q12) Jdeveloper?Java EE 6?????????????? > Q26) managed beans?EJB????????????????EJB??????????????????????managed beans?????????????????????Managed Beans?????????? > Q29) XML???????????????????????????????

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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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  • 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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  • How should a JEE application store credentials for logging in to an external system?

    - by FGreg
    I am in a situation where I have a Web Application (WAR) that is accessing a REST service provided by another application. The REST service uses Basic HTTP Authentication. So that means the application calling the REST service needs to store user credentials somehow. To further complicate things, this is an enterprise, so there are different 'regions' the application moves through which will have different credentials for the same service (think local development, development region, integration region, user test region, production, etc...) My first instinct is that the credentials should be stored by the JEE container and the application should ask the container for the credentials (probably via JNDI?). I'm beginning to read about Java Authentication and Authorization Service (JAAS) but I'm not sure if that is the appropriate solution to this problem. How should a JEE application store credentials for logging in to an external system? A few more details about my WAR. It is a Spring-Integration project that has no front-end. The container I am working with is Websphere. I am using JEE 5 and Spring 4.0.1. To this point I have not needed to consider spring-security... does this situation mean I should re-evaluate that decision?

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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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  • 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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