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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • Should I build a multi-threaded system that handles events from a game and sorts them, independently, into different threads based on priority?

    - by JonathonG
    Can I build a multi-threaded system that handles events from a game and sorts them, independently, into different threads based on priority, and is it a good idea? Here's more info: I am about to begin work on porting a mid-sized game from Flash/AS3 to Java so that I can continue development with multi-threading capabilities. Here's a small bit of background about the game: The game contains numerous asynchronous activities, such as "world updating" (the game environment is constantly changing based on a set of natural laws and forces), procedural generation of terrain, NPCs, quests, items, etc., and on top of that, the effects of all of the player's interactions with his environment are programmatically calculated in real time, based on a set of constantly changing "stats" and once again, natural laws and forces. All of these things going on at once, in an asynchronous manner, seem to lend themselves to multi-threading very well. My question is: Can I build some kind of central engine that handles the "stacking" of all of these events as they are triggered, and dynamically sorts them out amongst the available threads, and would it be a good idea? As an example: Essentially, every time something happens (IE, a magic missile being generated by a spell, or a bunch of plants need to grow to their next stage), instead of just processing that task right then and adding the new object(s) to a list of managed objects, send a reference to that event to a core "event handler" that throws it into a stack of all other currently queued events, which then sorts them out and orders them according to urgency, splits them between a number of available threads for as-fast-as-possible multithreaded execution.

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  • I don't understand how TDD helps me get a good design if I need a design to start testing it

    - by Michael Stum
    I'm trying to wrap my head around TDD, specifically the development part. I've looked at some books, but the ones I found mainly tackle the testing part - the History of NUnit, why testing is good, Red/Green/Refactor and how to create a String Calculator. Good stuff, but that's "just" Unit Testing, not TDD. Specifically, I don't understand how TDD helps me get a good design if I need a Design to start testing it. To illustrate, imagine these 3 requirements: A catalog needs to have a list of products The catalog should remember which products a user viewed Users should be able to search for a product At this points, many books pull a magic rabbit out of a hat and just dive into "Testing the ProductService", but they don't explain how they came to the conclusion that there is a ProductService in the first place. That is the "Development" part in TDD that I'm trying to understand. There needs to be an existing design, but stuff outside of entity-services (that is: There is a Product, so there should be a ProductService) is nowhere to be found (e.g., the second requirement requires me to have some concept of a User, but where would I put the functionality to remind? And is Search a feature of the ProductService or a separate SearchService? How would I know which I should choose?) According to SOLID, I would need a UserService, but if I design a system without TDD, I might end up with a whole bunch of Single-Method Services. Isn't TDD intended to make me discover my design in the first place? I'm a .net developer, but Java resources would also work. I feel that there doesn't seem to be a real sample application or book that deals with a real line of business application. Can someone provide a clear example that illustrates the process of creating a design using TDD?

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  • Multiple vulnerabilities fixed in Java 7U9

    - by RitwikGhoshal
    CVE DescriptionCVSSv2 Base ScoreComponentProduct and Resolution CVE-2012-5086 10.0 Java 7 Solaris 11.1 10/12 SRU 2.5 CVE-2012-5083 10.0 CVE-2012-5087 10.0 CVE-2012-1533 10.0 CVE-2012-1532 10.0 CVE-2012-1531 10.0 CVE-2012-5076 10.0 CVE-2012-3143 10.0 CVE-2012-5088 10.0 CVE-2012-5089 7.6 CVE-2012-5084 7.6 CVE-2012-3159 7.5 CVE-2012-5068 7.5 CVE-2012-4416 6.4 CVE-2012-5074 6.4 CVE-2012-5071 6.4 CVE-2012-5069 5.8 CVE-2012-5067 5.0 CVE-2012-5070 5.0 CVE-2012-5075 5.0 CVE-2012-5073 5.0 CVE-2012-5079 5.0 CVE-2012-5072 5.0 CVE-2012-5081 5.0 CVE-2012-3216 2.6 CVE-2012-5077 2.6 CVE-2012-5085 0.0 This notification describes vulnerabilities fixed in third-party components that are included in Oracle's product distributions. Information about each CVE can be found on Java SE Critical Patch Update - October 2012 Information about vulnerabilities affecting Oracle products can be found on Oracle Critical Patch Updates and Security Alerts page.

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  • 16-bit PNGs in Slick2D

    - by Neglected
    I'm working on a project and I'm using some 3rd party sprites just to get it off the ground; recently I've come into a hitch. Slick2D doesn't seem to want to load my images. That is, it will warn me that images are the wrong bit-depth. All the images are in 16-bit PNG form (PNG is required for transparency). Is there any way I can disable the warning (being the bad guy programmer (the console print for each individual load REALLY SLOWS DOWN the image)) or is there another solution? I was thinking about converting all images (using imagemagick) to .gif (with an alpha channel). Would there be any loss in quality between formats? EDIT: I tried using imagemagick but some of the sprites use pure black so I can't do that without wrecking the image. EDIT2: using "identify" on any of the images show them as being 8-bit.. but Slick2D won't load them. What the hell? D: EDIT3: Issue solved (ish). If you are googling this then just disable the java png loader from slick by sticking this somewhere in your code (like the main method): System.setProperty("org.newdawn.slick.pngloader", "false");

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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 involved with writing a lobby server?

    - by Kira
    So I'm writing a Chess matchmaking system based on a Lobby view with gaming rooms, general chat etc. So far I have a working prototype but I have big doubts regarding some things I did with the server. Writing a gaming lobby server is a new programming experience to me and so I don't have a clear nor precise programming model for it. I also couldn't find a paper that describes how it should work. I ordered "Java Network Programming 3rd edition" from Amazon and still waiting for shipment, hopefully I'll find some useful examples/information in this book. Meanwhile, I'd like to gather your opinions and see how you would handle some things so I can learn how to write a server correctly. Here are a few questions off the top of my head: (may be more will come) First, let's define what a server does. It's primary functionality is to hold TCP connections with clients, listen to the events they generate and dispatch them to the other players. But is there more to it than that? Should I use one thread per client? If so, 300 clients = 300 threads. Isn't that too much? What hardware is needed to support that? And how much bandwidth does a lobby consume then approx? What kind of data structure should be used to hold the clients' sockets? How do you protect it from concurrent modification (eg. a player enters or exists the lobby) when iterating through it to dispatch an event without hurting throughput? Is ConcurrentHashMap the correct answer here, or are there some techniques I should know? When a user enters the lobby, what mechanism would you use to transfer the state of the lobby to him? And while this is happening, where do the other events bubble up? Screenshot : http://imageshack.us/photo/my-images/695/sansrewyh.png/

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  • Sprite batching in OpenGL

    - by Roy T.
    I've got a JAVA based game with an OpenGL rendering front that is drawing a large amount of sprites every frame (during testing it peaked at 700). Now this game is completely unoptimized. There is no spatial partitioning (so a sprite is drawn even if it isn't on screen) and every sprite is drawn separately like this: graphics.glPushMatrix(); { graphics.glTranslated(x, y, 0.0); graphics.glRotated(degrees, 0, 0, 1); graphics.glBegin(GL2.GL_QUADS); graphics.glTexCoord2f (1.0f, 0.0f); graphics.glVertex2d(half_size , half_size); // upper right // same for upper left, lower left, lower right graphics.glEnd(); } graphics.glPopMatrix(); Currently the game is running at +-25FPS and is CPU bound. I would like to improve performance by adding spatial partitioning (which I know how to do) and sprite batching. Not drawing sprites that aren't on screen will help a lot, however since players can zoom out it won't help enough, hence the need for batching. However sprite batching in OpenGL is a bit of mystery to me. I usually work with XNA where a few classes to do this are built in. But in OpenGL I don't know what to do. As for further optimization, the game I'm working on as a few interesting characteristics. A lot of sprites have the same texture and all the sprites are square. Maybe these characteristics will help determine an efficient batching technique?

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  • New Java ME JSRs submitted

    - by heathervc
    Two new Java ME related JSRs were submitted to the JCP program office this week and are now available for review. JSR 360, Connected Limited Device Configuration (CLDC) 8, has been submitted by Oracle for JSR Review.  This review period is open until 15 October.  The ME EC will vote on the JSR Approval Ballot 16-29 October. JSR 361 Java ME Embedded Profile, has been submitted by Oracle for JSR Review. This review period is open until 15 October.  The ME EC will vote on the JSR Approval Ballot 16-29 October.

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  • VDC Research Webcast: Engineering Business Value in the IoT with Java 8

    - by tangelucci
    Date: Thursday, June 19, 2014 Time: 9:30 AM PDT, 12:30 PM EDT, 17:30 GMT The growth of the Internet of Things (IoT) opens up new service-driven opportunities, delivering increased efficiencies, better customer value, and improved quality of life. Realizing the full potential of the Internet of Things requires that we change how we view and build devices. These next-generation systems provide the core foundation of the services, rapidly transforming data to information to value. From healthcare to building control systems to vehicle telematic systems, the IoT focuses on how conneted devices can become more intelligent, enhance interoperability with other devices, systems and services, and drive timely decisions while delivering real business return for all. Join this webcast to learn about: Driving both revenue opportunities and operational efficiencies for the IoT value chain Leveraging Java to make devices more secure How Java can help overcome resource gaps around intelligent connected devices Suggestions on how to better manage fragmentation in embedded devices Register here: http://event.on24.com/r.htm?e=793757&s=1&k=4EA8426D0D31C60A2EDB139635FF75AB

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  • How to load chunks of 2d map segments when player reaches a certain point?

    - by 2kan
    In my 2d platformer (made with Java and Slick2d), random maps are made by combining different segments together and displaying them one after the other. My problem is that I can't load too many segments or the game will run out of memory, so I want to load n number of segments at a time in chunks, then load the next chunk when the player comes near the end of one. I've attempted to do this for a couple of hours now, but I just can't get it to work at all. This is my chunk generation function where chunkLoad is the number of segments to load and BLOCK_WIDTH is the number of blocks/tiles each segment is across. Chunk1 and map are arrays of segments. Random r = new Random(); for(int i=0; i<chunkLoad; i++) { int id = r.nextInt(4)+2; chunk1[i] = new BlockMap("res/window/map"+id+".tmx", i*BLOCK_WIDTH); } map = chunk1; chunksLoaded++; The map is then drawn on the screen like this. tmap is a TiledMap object and each block/tile is 16 pixels wide for(int i=0; i<chunkLoad; i++) { map[i].tmap.render((i * BLOCK_WIDTH * 16) + (cameraX), 0); } I can successfully load new chunks, but I can't display them in the correct position, nor the hitboxes. Any suggestions? Thanks.

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  • Multiple vulnerabilities fixed in Java 6U37

    - by RitwikGhoshal
    CVE DescriptionCVSSv2 Base ScoreComponentProduct and Resolution CVE-2012-5083 10.0 Java 6 Solaris 11.1 10/12 SRU 2.5 CVE-2012-1531 10.0 CVE-2012-5086 10.0 CVE-2012-1533 10.0 CVE-2012-1532 10.0 CVE-2012-3143 10.0 CVE-2012-5089 7.6 CVE-2012-5084 7.6 CVE-2012-3159 7.5 CVE-2012-5068 7.5 CVE-2012-4416 6.4 CVE-2012-5071 6.4 CVE-2012-5069 5.8 CVE-2012-5075 5.0 CVE-2012-5073 5.0 CVE-2012-5079 5.0 CVE-2012-5072 5.0 CVE-2012-5081 5.0 CVE-2012-3216 2.6 CVE-2012-5077 2.6 CVE-2012-5085 0.0 This notification describes vulnerabilities fixed in third-party components that are included in Oracle's product distributions. Information about each CVE can be found on Java SE Critical Patch Update - October 2012 Information about vulnerabilities affecting Oracle products can be found on Oracle Critical Patch Updates and Security Alerts page.

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  • Implementing Explosions

    - by Xkynar
    I want to add explosions to my 2D game, but im having a hard time with the architecture. Several game elements might be responsible for explosions, like, lets say, explosive barrels and bullets (and there might be chain reactions with close barrels). The only options i can come up with are: 1 - Having an array of explosions and treat them as a game element as important as any other Pros: Having a single array which is updated and drawn with all the other game element arrays makes it more organized and simple to update, and the explosive barrels at a first glance would be easy to create, simply by passing the explosion array as a pointer to each explosive barrel constructor Cons: It might be hard for the bullets to add an explosion to the vector, since bullets are shot by a Weapon class which is located in every mob, so lets say, if i create a new enemy and add it to the enemy array, that enemy will have a weapon and functions to be able to use it, and if i want the weapon (rocket launcher in this case) to have access to the explosions array to be able to add a new one, id have to pass the explosion array as a pointer to the enemy, which would then pass it to the weapon, which would pass it to the bullets (ugly chain). Another problem I can think of is a little more weird: If im checking the collisions between explosions and barrels (so i create a chain reaction) and i detect an explosion colliding with a barrel, if i add a new explosion while im iterating the explosions java will trow an exception. So this is kinda annoying, i cant iterate through the explosions and add a new explosion, i must do it in another way... The other way which isnt really well thought yet is to just add an explosive component to every element that might explode so that when it dies, it explodes or something, but i dont have good ways on implementing this theory either Honestly i dont like either the solutions so id like to know how is it usually done by actual game developers, sorry if my problem seems trivial and dumb.

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  • Error Setting Java Environment Variables

    - by Cherie Riesberg
    Problem:  Not exactly SharePoint, but the issue is when setting the %JAVA_HOME% environment variable, Java installs to the Program Files directory by default.  The space in the path seems to stop the variable from being read.  You get an error. Solution:  Change Program Files to Progra~1, so the path now looks like this: C:\Progra~1\Java\jdk1.6.0_23\bin\; You can type %JAVA_HOME%\bin\javac to test.  Output should look like this: Usage: javac <options> <source files> where possible options include: ...

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  • How to handle notifications to several partial views of the same model?

    - by Seki
    I am working on refactoring an old simulation of a Turing machine. The application uses a class that contains the state and the logic of program execution, and several panels to display the tape representation and show the state, messages, and the GUI controls (start, stop, program listing, ...). I would like to refactor it using the MVC architecture that was not used originaly: the Frame is the only way to get access to the different panels and there is also a strong coupling between the "engine" class and the GUI updates in the way of frame.displayPanel.state.setText("halted"); or frame.outputPanel.messages.append("some thing"); It looks to me that I should put the state related code into an observable model class and make the different panels observers. My problem is that the java Observable class only provides a global notification to the Observers, while I would prefer not to refresh every Observers everytime, but only when the part that specificaly observe has changed. I am thinking of implementing myself several vectors of listeners (for the state / position, for the output messages, ...) but I feel like reinventing the wheel. I though also about adding some flags that the observers could check like isNewMessageAvailable(), hasTapeMoved(), etc but it sounds also approximative design. BTW, is it ok to keep the fetch / execute loop into the model or should I move it in another place? We can think in a theorical ideal way as I am completely revamping this small application.

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  • Dynamic object creation with HashMap

    - by Salor
    I want to use a HashMap to dynamically create objects based on the key. I have a Random Map Generator that stores the maps in 3D Arrays of Type Integer[][][]. Upon creation of the actual map I iterate through this array and based on the Integer I want to create the right block. Example: Integer[][][] map ... map[6][6][6] = 3; 3 is a Earth-Block and now I want to initialize a new Block of this type and give it the right coordinates. Currently I store my Bindings from Integer to Class in a HashMap(Integer, String) and create my objects like that: int id = array[x][y][z]; String block_name = Blocks.map.get(id); Block block = (Block) Class.forName(block_name).newInstance(); block.setPosition(x,y,z); But I want to avoid newInstance() if possible. I've never worked that dynamically with Java before and I couldn't find a solution like changing the HashMap to (Integer, Class) or something. I just need to create a new Object based upon the Integer. Any ideas/solutions? Thanks in advance and have a wonderful day!

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  • How to get the level and position of the player from an extern program? [on hold]

    - by user3727174
    I want to write a program that needs the current level and position of the player (primary single player). This should work for potentially every game installed and running on the computer my program is running on. The data I need is basically one integer value for the level (if there are any) and three integer values for x, y and optimal z for the position of the player. In which relation/scale or where the null point is does not matter, because this information is going to be interpreted game dependent, I will use this information to read information out of a database created for the game currently running. Currently I'm using C++, but if there is a better option for Java I´m willing to port my program. My thoughs so far are: make a mod for every game that should be supported, get the position/level from there, write this information to the disk and read it from my program tracking mouse/keyboard events and reconstructing the movement won't work Are there any general APIs for something like this? Any Tool to find this data? Or maybe engines that provide APIs to get this data directly from the game?

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