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  • java double buffering problem

    - by russell
    Whats wrong with my applet code which does not render double buffering correctly.I am trying and trying.But failed to get a solution.Plz Plz someone tell me whats wrong with my code. import java.applet.* ; import java.awt.* ; import java.awt.event.* ; public class Ball extends Applet implements Runnable { // Initialisierung der Variablen int x_pos = 10; // x - Position des Balles int y_pos = 100; // y - Position des Balles int radius = 20; // Radius des Balles Image buffer=null; //Graphics graphic=null; int w,h; public void init() { Dimension d=getSize(); w=d.width; h=d.height; buffer=createImage(w,h); //graphic=buffer.getGraphics(); setBackground (Color.black); } public void start () { // Schaffen eines neuen Threads, in dem das Spiel l?uft Thread th = new Thread (this); // Starten des Threads th.start (); } public void stop() { } public void destroy() { } public void run () { // Erniedrigen der ThreadPriority um zeichnen zu erleichtern Thread.currentThread().setPriority(Thread.MIN_PRIORITY); // Solange true ist l?uft der Thread weiter while (true) { // Ver?ndern der x- Koordinate repaint(); x_pos++; y_pos++; //x2--; //y2--; // Neuzeichnen des Applets if(x_pos>410) x_pos=20; if(y_pos>410) y_pos=20; try { Thread.sleep (30); } catch (InterruptedException ex) { // do nothing } Thread.currentThread().setPriority(Thread.MAX_PRIORITY); } } public void paint (Graphics g) { Graphics screen=null; screen=g; g=buffer.getGraphics(); g.setColor(Color.red); g.fillOval(x_pos - radius, y_pos - radius, 2 * radius, 2 * radius); g.setColor(Color.green); screen.drawImage(buffer,0,0,this); } public void update(Graphics g) { paint(g); } } what change should i make.When offscreen image is drawn the previous image also remain in screen.How to erase the previous image from the screen??

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  • How to know start and kill processes within Java code (or C or Python) on *nix

    - by recipriversexclusion
    I need to write a process controller module on Linux that handles tasks, which are each made up of multiple executables. The input to the controller is an XML file that contains the path to each executable and list of command line parameters to be passed to each. I need to implement the following functionality: Start each executable as an independent Be able to kill any of the created processes independent of the others In order to do (2), I think I need to capture the pid when I create a process, to issue a system kill command. I tried to get access to pid in Java but saw no easy way to do it. All my other logic (putting info about the tasks in DB, etc) is done in Java so I'd like to stick with that, but if there are solutions you can suggest in C, C++, or Python I'd appreciate those, too.

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  • Java Socket Connection is flooding network OR resulting in high ping

    - by user1461100
    i have a little problem with my java socket code. I'm writing an android client application which is sending data to a java multithreaded socket server on my pc through direct(!) wireless connection. It works fine but i want to improve it for mobile applications as it is very power consuming by now. When i remove two special lines in my code, the cpu usage of my mobile device (htc one x) is totally okay but then my connection seems to have high ping rates or something like that... Here is a server code snippet where i receive the clients data: while(true) { try { .... Object obj = in.readObject(); if(obj != null) { Class clazz = obj.getClass(); String className = clazz.getName(); if(className.equals("java.lang.String")) { String cmd = (String)obj; if(cmd.equals("dc")) { System.out.println("Client "+id+" disconnected!"); Server.connectedClients[id-1] = false; break; } if(cmd.substring(0,1).equals("!")) { robot.keyRelease(PlayerEnum.getKey(cmd,id)); } else { robot.keyPress(PlayerEnum.getKey(cmd,id)); } } } } catch .... Heres the client part, where i send my data in a while loop: private void networking() { try { if(client != null) { .... out.writeObject(sendQueue.poll()); .... } } catch .... when i write it this why, i send data everytime the while loop gets executed.. when sendQueue is empty, a null "Object" will be send. this results in "high" network traffic and in "high" cpu usage. BUT: all send comments are received nearly immediately. when i change the code to following: while(true) ... if(sendQueue.peek() != null) { out.writeObject(sendQueue.poll()); } ... the cpu usage is totally okay but i'm getting some laggs.. the commands do not arrive fast enough.. as i said, it works fine (besides cpu usage) if i'm sending data(with that null objects) every while execution. but i'm sure that this is very rough coding style because i'm kind of flooding the network. any hints? what am i doing wrong?? Thanks for your Help! Sincerly yours, maaft

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  • How do I rewrite binary data in Java

    - by hayato
    I'm trying to figure out how to replace binary data using Java. below is a PHP example of replacing "foo" to "bar" from a swf file. <?php $fp = fopen("binary.swf","rb"); $size = filesize("binary.swf"); $search = bin2hex("foo"); $replace = bin2hex("bar"); $data = fread($fp, $size); $data16 = bin2hex($data); $data16 = str_replace($search, $replace, $data16); $data = pack('H*',$data16); header("Content-Type:application/x-shockwave-flash"); echo $data; ?> How do I do this in Java.

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  • AES acceleration for Java

    - by chris_l
    I want to encrypt/decrypt lots of small (2-10kB) pieces of data. The performance is ok for now: On a Core2Duo, I get about 90 MBytes/s AES256 (when using 2 threads). But I may need to improve that in the future - or at least reduce the impact on the CPU. Is it possible to use dedicated AES encryption hardware with Java (using JCE, or maybe a different API)? Would Java take advantage of special CPU features (SSE5?!), if I get a better CPU? Or are there faster JCE providers? (I tried SunJCE and BouncyCastle - no big difference.) Other possiblilities?

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  • Pet project ideas in Java

    - by Amir Rachum
    I'm looking for a pet project idea in Java. I'm a Software Engineering undergraduate finishing my 3rd year. I have also been working for the past 1.5-2 years programming in C++, and I get enough of that at work. I recently learned Java and I like it very much. Already done some project assignments and some really small console applications, but I'm looking for something to invest my time in. I would like a project that is complex enough to "brag about" (have it open sourced and get people interested, added to resume) and learn while doing it, but also simple enough to be able to at least have a working version in a few months. I know the most common advice is something that I need, but I admit I simply couldn't think of anything like that. Any ideas?

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  • A better way to do XML in Java

    - by jboyd
    There are a lot of questions that ask the best XML parser, I am more interested in what is the XML parser that is the most like Groovy for Java? I want: SomeApiDefinedObject o = parseXml( xml ); for( SomeApiDefinedObject it : o.getChildren() ) { System.out.println( it.getAttributes() ); } The most important things are that I don't want to create an object for every type of filed, I'd rather just deal with them all as strings, and that building the XML doesn't require any converters or anything, just a simple object that is already defined If you have used the Groovy XML parser, you will know what I'm talking about Alternatively, would it be better for me to just use Groovy from Java?

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  • Managing Data Dependecies of Java Classes that Load Data from the Classpath at Runtime

    - by Martin Potthast
    What is the simplest way to manage dependencies of Java classes to data files present in the classpath? More specifically: How should data dependencies be annotated? Perhaps using Java annotations (e.g., @Data)? Or rather some build entries in a build script or a properties file? Is there build tool that integrates and evaluates such information (Ant, Scons, ...)? Do you have examples? Consider the following scenario: A few lines of Ant create a Jar from my sources that includes everything found on the classpath. Then jarjar is used to remove all .class files that are not necessary to execute, say, class Foo. The problem is that all the data files that class Bar depends upon are still there in the Jar. The ideal deployment script, however, would recognize that the data files on which only class Bar depends can be removed while data files on which class Foo depends must be retained. Any hints?

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  • OSX - Update "Java for OS X 2012-002" is not mentioned on support.apple.com, is this ok?

    - by snies
    Straight after installing "Java for OS X 2012-001" Software Update asks me to install "Java for OS X 2012-002", which has the exact same size (66.6 MB) and description (including the same two links: HT5055 and HT1222) as the former, which strikes me as odd. The "Java for OS X 2012-001" is described on the apple support pages, but the "Java for OS X 2012-002" is not mentioned anywhere. Also searching on google does not yield any usable results. What is your opinon? Am i paranoid? Did you also see this update?

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  • Measuring time spent in application / thread

    - by Adamski
    I am writing a simulation in Java whereby objects act under Newtonian physics. An object may have a force applied to it and the resulting velocity causes it to move across the screen. The nature of the simulation means that objects move in discrete steps depending on the time ellapsed between the current and previous iteration of the animation loop; e.g public void animationLoop() { long prev = System.currentTimeMillis(); long now; while(true) { long now = System.currentTimeMillis(); long deltaMillis = now - prev; prev = now; if (deltaMillis > 0) { // Some time has passed for (Mass m : masses) { m.updatePosition(deltaMillis); } // Do all repaints. } } } A problem arises if the animation thread is delayed in some way causing a large amount of time to ellapse (the classic case being under Windows whereby clicking and holding on minimise / maximise prevents a repaint), which causes objects to move at an alarming rate. My question: Is there a way to determine the time spent in the animation thread rather than the wallclock time, or can anyone suggest a workaround to avoid this problem? My only thought so far is to contstrain deltaMillis by some upper bound.

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  • Tool for checking source for dependencies on specific Java versions

    - by Gregor
    Is there a quick way (e.g. tool) to detect, from the source (or maybe even from compiled classes), which parts of an application call Java API methods that are only implemented in a specific Java version? (e.g. which parts of my app are Java6-specific) I don't necessarily want to hop through all ClassMismatchErrors and avoid the trial-and-error-method. Let's say I only want to document which parts of an application won't work if they were writte for, e.g., Java6 and I want to run it in a version 5 JDK. Is there something like this? Google did not help this time, nor did I find any solution here (a rare case indeed:)

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  • Printing out series of numbers in java

    - by Jay
    hi guys i am just doing some reading for myself to learn java and came across this problem and is currently stuck. i need to print out series of number based on the input given by the user. for example, if input = 5, the output should be as follows @1@22@333@4444@55555 import java.util.*; public class ex5{ public static void main(String[] args){ Scanner kb = new Scanner(System.in); System.out.println("Please type a #: "); int input = kb.nextInt(); for(int i=0;i<input;i++){ if(input==1){ System.out.print("@1"); } if(input==2){ System.out.print("@1@22"); } } } } this doesnt seem to be working because this is the output i get Please type a #: 2 @1@22@1@22 im not sure what to put inside the for loop right now and i dont think i am using the for loop here very well either... any help guys?

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  • 'void' type not allowed here error (java) help?

    - by David
    When i try to compile this: import java.awt.* ; class obj { public static void printPoint (Point p) { System.out.println ("(" + p.x + ", " + p.y + ")"); } public static void main (String[]arg) { Point blank = new Point (3,4) ; System.out.println (printPoint (blank)) ; } } i get this error: obj.java:12: 'void' type not allowed here System.out.println (printPoint (blank)) ; ^ 1 error I don't really know how to start asking about this other than to ask: What went wrong here? What does this error message mean?

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  • drawImage in Java applet flickers in Safari

    - by lcvinny
    I'm having a flicker problem in a Java applet in Safari (Mac). However, it's not the usual double buffering problem. I have isolated it down to one single drawImage call (no redundant repaint, no clear is called), which gives a white flicker before painting the image but not on every repaint. In fact, I measured the duration of the drawImage call, which is normally about 1ms, but up to 30ms about every 5th time paint is called, which is when it flickers. Repaints are triggered when I drag a component or when the window is scrolled. Is this a bug in the java implementation on OSX, and is there a fix for it?

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  • Detect file system changes on Samba share with Java on Windows

    - by GHad
    Hi, for a recent project I need to detect file system changes on a mapped Samba share from java on windows: Creates, updates and removes. At the moment I am using a folder poll that maintains a list of files and their modified timestamp to look for events. But my problem is that this folder poll only peeks into the folder at certain times (every 10 seconds for example), so an updated file can be updated twice between two polls without recognizing. Is there any way to get events from windows inside Java whenever a file event occours on that mappep Samba share? Thanks!

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  • Java + Eclipse + Pulpcore

    - by cable729
    I've never programmed in java or eclipse before, although I have used c# and visual studio. I'm trying to get started with java development, and develop 2d games, but I can't get the project to run. I've followed the tutorial here: http://cloningtheclassics.com/getting-started-with-pulpcore/ I've retried the tutorial at least 5 times, and I still can't get it to work. The error it displays is: Buildfile: C:\workspace\javapulp\project\build.xml [taskdef] Could not load definitions from resource tasks.properties. It could not be found. [taskdef] Could not load definitions from resource tasks.properties. It could not be found. -init: BUILD FAILED C:\workspace\javapulp\project\build.xml:127: Required file not found: ../../build/pulpcore-applet-debug-0.11.jar Total time: 1 second Thanks in advance!

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  • Hibernate Communications Link Failure in Restlet-Hibernate Based Java application powered by MySQL

    - by Vatsala
    Let me describe my question - I have a Java application - Hibernate as the DB interfacing layer over MySQL. I get the communications link failure error in my application. The occurence of this error is a very specific case. I get this error , When I leave mysql server unattended for more than approximately 6 hours (i.e. when there are no queries issued to MySQL for more than approximately 6 hours). I am pasting a top 'exception' level description below, and adding a pastebin link for a detailed stacktrace description. javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: Cannot open connection - Caused by: org.hibernate.exception.JDBCConnectionException: Cannot open connection - Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure - The last packet successfully received from the server was 1,274,868,181,212 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago. - Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure - The last packet successfully received from the server was 1,274,868,181,212 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago. - Caused by: java.net.ConnectException: Connection refused: connect the link to the pastebin for further investigation - http://pastebin.com/4KujAmgD What I understand from these exception statements is that MySQL is refusing to take in any connections after a period of idle/nil activity. I have been reading up a bit about this via google search, and came to know that one of the possible ways to overcome this is to set values for c3p0 properties as c3p0 comes bundled with Hibernate. Specifically, I read from here http://www.mchange.com/projects/c3p0/index.html that setting two properties idleConnectionTestPeriod and preferredTestQuery will solve this for me. But these values dont seem to have had an effect. Is this the correct approach to fixing this? If not, what is the right way to get over this? The following are related Communications Link Failure questions at stackoverflow.com, but I've not found a satisfactory answer in their answers. http://stackoverflow.com/questions/2121829/java-db-communications-link-failure http://stackoverflow.com/questions/298988/how-to-handle-communication-link-failure Note 1 - i dont get this error when I am using my application continuosly. Note 2 - I use JPA with Hibernate and hence my hibernate.dialect,etc hibernate properties reside within the persistence.xml in the META-INF folder (does that prevent the c3p0 properties from working?)

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  • Java/C++ communication via pipe on Windows

    - by Warlax
    Hi, I have two separate programs, one in Java and one in C++, both running on Windows. We need to do bidirectional interprocess communication between the two. Up until now, we were using this awkward solution of writing to text files and reading them on the other side, where the producer would generate a .lock file when it's done writing and the consumer would remove that when it's done reading... like I said, awkward. If we were on *nix, we would use a pipe using popen() on the C++ and RadomAccessFile on the Java side. It seems to work well. What can we do on Windows? Can we use named pipes? Thank you.

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  • Console class in java Exception in reading password

    - by satheesh
    Hi, i am trying to use Console class in java. with this code import java.io.Console; public class ConsoleClass { public static void main(String[] args){ Console c=System.console(); char[] pw; pw=c.readPassword("%s","pw :"); for(char ch:pw){ c.format("%c",ch); } c.format("\n"); MyUtility mu =new MyUtility(); while(true){ String name=c.readLine("%s", "input?: "); c.format("output: %s \n",mu.doStuff(name)); } } } class MyUtility{ String doStuff(String arg1){ return "result is " +arg1; } } here i am getting NullPointerException when i tried to run in netbeans but i am not getting any Exception when tried to run in cmd with out netbeans IDE.Why?

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