02 · java ee - Page 420

MCP 1.7.10 Java class navigation

- by Elias Benevedes

So, I'm new to the Minecraft modding community and trying to understand where to start. I've attempted to do it before, but dropped it to the complexity of starting and the lack of a site like this to help (Mind that I'm also semi-new to Java, but have worked extensively in Javascript and Python. I understand how Java is different from the two). I have downloaded MCP 9.08 (Decompiles 1.7.10), and decompiled Minecraft. I'm looking to mod client, so I didn't supply it with a server jar. Everything seemed to work fine in decompile (Only error was it couldn't find the server jar). I can find my files in /mcp908/src/minecraft/net/minecraft. However, if I open up one of the classes in, say, block, I see a bunch of variables starting with p_ and ending with _. Is there any way to make these variables more decipherable, to understand what's going on so I can learn by example? Thank you.

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What did Rich Hickey mean when he said, "All that specificity [of interfaces/classes/types] kills your reuse!"

- by GlenPeterson

In Rich Hickey's thought-provoking goto conference keynote "The Value of Values" at 29 minutes he's talking about the overhead of a language like Java and makes a statement like, "All those interfaces kill your reuse." What does he mean? Is that true? In my search for answers, I have run across: The Principle of Least Knowledge AKA The Law of Demeter which encourages airtight API interfaces. Wikipedia also lists some disadvantages. Kevlin Henney's Imperial Clothing Crisis which argues that use, not reuse is the appropriate goal. Jack Diederich's "Stop Writing Classes" talk which argues against over-engineering in general. Clearly, anything written badly enough will be useless. But how would the interface of a well-written API prevent that code from being used? There are examples throughout history of something made for one purpose being used more for something else. But in the software world, if you use something for a purpose it wasn't intended for, it usually breaks. I'm looking for one good example of a good interface preventing a legitimate but unintended use of some code. Does that exist? I can't picture it.

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Adjusting the rate of movement of different objects on the same timer

- by theUg

I have a series of objects moving along the straight lines. I want to implement slight changes of velocity of each of the object. Constraint is existing model of animation. I am new to this, and not sure if it is the best way to accommodate varying speeds, but what do I know? It is a Java application that repaints the panel every time the timer expires. Timer is set via swing.Timer object that is set by timer delay constant. Every time the game is stepped objects’ coordinates advanced by an increment constant. Most of the objects are of the same class. Is there fairly easy way to refactor existing system to allow changing velocity for an individual object? Is there some obvious common solution I am not aware about? Idea I am having right now is to set timer delay fairly small, and only move objects every so many cycles of animation so that the apparent speed can be adjusted by varying how often they get moved. But that seems fairly involved, and I do not think it is the most elegant solution in terms of performance what with repainting the whole frame every 3-5 milliseconds. Can it be done by advancing the objects so many (varying) times during the certain interval (let’s say 35ms for something like 28fps), and use repaint() method to redraw just individual object? Do I need to mess with pausing animation for smoothness at higher redraw rates? Is it common practise to check for collision at larger step interval, but draw animation a lot more frequently?

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How to keep track of previous scenes and return to them in libgdx

- by MxyL

I have three scenes: SceneTitle, SceneMenu, SceneLoad. (The difference between the title scene and the menu scene is that the title scene is what you see when you first turn on the game, and the menu scene is what you can access during the game. During the game, meaning, after you've hit "play!" in the title scene.) I provide the ability to save progress and consequently load a particular game. An issue that I've run into is being able to easily keep track of the previous scene. For example, if you enter the load scene and then decide to change your mind, the game needs to go back to where you were before; this isn't something that can be hardcoded. Now, an easy solution off the top of my head is to simply maintain a scene stack, which basically keeps track of history for me. A simple transaction would be as follows I'm currently in the menu scene, so the top of the stack is SceneMenu I go to the load scene, so the game pushes SceneLoad onto the stack. When I return from the load scene, the game pops SceneLoad off the stack and initializes the scene that's currently at the top, which is SceneMenu I'm coding in Java, so I can't simply pass around Classes as if they were objects, so I've decided implemented as enum for eac scene and put that on the stack and then have my scene managing class go through a list of if conditions to return the appropriate instance of the class. How can I implement my scene stack without having to do too much work maintaining it?

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The JavaFX Community Site on Java.net

- by Tori Wieldt

Community activity surrounding JavaFX has been steadily growing, with tweets, blog posts, and projects increasing in number. We are pleased to announce that there is now a JavaFX community site on Java.net at the following URL: javafxcommunity.com This site is an aggregator of JavaFX information, where you can find links to JavaFX blog posts, tweets, and other resources. Gerrit Grunwald and Jim Weaver are the community leaders for this site, and they welcome your feedback on how to make the JavaFX Community site more useful to you! Learn more on Jim Weaver’s Rich-Client Java Blog.

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JDK8 New Build Infrastructure

- by kto

I unintentionally posted this before I verified everything, so once I have verified it all works, I'll updated this post. But this is what should work... Most Interesting Builder in the World: "I don't always build the jdk, but when I do, I prefer The New JDK8 Build Infrastructure. Stay built, my friends." So the new Build Infrastructure changes have been integrated into the jdk8/build forest along side the older Makefiles (newer in makefiles/ and older ones in make/). The default is still the older makefiles. Instructions can be found in the Build-Infra Project User Guide. The Build-Infra project's goal is to create the fastest build possible and correct many of the build issues we have been carrying around for years. I cannot take credit for much of this work, and wish to recognize the people who do so much work on this (and will probably still do more), see the New Build Infrastructure Changeset for a list of these talented and hard working JDK engineers. A big "THANK YOU" from me. Of course, every OS and system is different, and the focus has been on Linux X64 to start, Ubuntu 11.10 X64 in particular. So there are at least a base set of system packages you need. On Ubuntu 11.10 X64, you should run the following after getting into a root permissions situation (e.g. have run "sudo bash"): apt-get install aptitude aptitude update aptitude install mercurial openjdk-7-jdk rpm ssh expect tcsh csh ksh gawk g++ build-essential lesstif2-dev Then get the jdk8/build sources: hg clone http://hg.openjdk.java.net/jdk8/build jdk8-build cd jdk8-build sh ./get_source.sh Then do your build: cd common/makefiles bash ../autoconf/configure make We still have lots to do, but this is a tremendous start. -kto

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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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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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Knowing state of game in real time

- by evthim

I'm trying to code a tic tac toe game in java and I need help figuring out how to efficiently and without freezing the program check if someone won the game. I'm only in the design stages now, I haven't started programming anything but I'm wondering how would I know at all times the state of the game and exactly when someone wins? Response to MarkR: (note: had to place comment here, it was too long for comment section) It's not a homework problem, I'm trying to get more practice programming GUI's which I've only done once as a freshman in my second introductory programming course. I understand I'll have a 2D array. I plan to have a 2D integer array where x would equal 1 and o would equal 0. However, won't it take too much time if I check after every move if someone won the game? Is there a way or a data structure or algorithm I can use so that the program will know the state (when I say state I mean not just knowing every position on the board, the int array will take care of that, I mean knowing that user 1 will win if he places x on this block) of the game at all times and thus can know automatically when someone won?

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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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Will Oracle Help Java Regain Its Status?

Oracle promises Java SE 7 release this year with increased developer productivity, modularization, and support for more than 200 languages.

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Will Oracle Help Java Regain Its Status?

Oracle promises Java SE 7 release this year with increased developer productivity, modularization, and support for more than 200 languages.

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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);