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  • Assigning int to byte in java?

    - by user303218
    int val =233; byte b = (byte)val; System.out.println(b); I have a simple case, like one integer with some value & i want to convert that value & place in the byte type for output. But in this case negative value is coming? How to successfully place the int value to byte type.

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  • Java Timer not working

    - by Jacob
    I have an Image named worldImageToUse and I have a Timer that is supposed to toggle worldImageToUse between two images every 1 second. But it does not seem to work. Help Please? public void startWorldImageFlash() { worldImageFlashTimer = new Timer(); TimerTask task = new TimerTask() { @Override public void run() { if(worldImageToUse == worldImage) setWorldImageBW(); if(worldImageToUse == worldImageBW) setWorldImageColor(); } }; worldImageFlashTimer.scheduleAtFixedRate(task, 0, 1000); } public void stopWorldImageFlash() { worldImageFlashTimer.cancel(); setWorldImageColor(); }

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  • Dynamic, reflective SignalHandler in Java

    - by pilcrow
    How do I install signal handling logic iff sun.misc.Signal is available? Background First generation of my code looked something like this: class MyApp { public static void main(String[] args) { ... Signal.handle(term_sig, new SignalHandler() { public void handle(Signal sig) { ... } }); ... } } I believe I understand how to reflectively test for and use signal handlers -- Class.forName("sun.misc.Signal"), reflectively call Signal.handle, and so forth. My impulse was simply to instantiate another anonymous inner class with the dynamically obtained SignalHandler class, but I think that's just wishful syntax.

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  • How to make sketching kind module in java?

    - by Nitz
    Hey Guys I am trying to make one software on which user can make any sketch and make any drawing kind of thing. i am trying to get reference from this two great software. 1. Notelab 2. Jarnal But both having great and many facility in it. But In my software i want only sketching-drawing, so how to do that? I tried to use Canvas but i don't get how to use it?

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  • When can Java produce a NaN (with specific code question)

    - by Brent
    I'm a bit perplexed by some code I'm currently writing. I am trying to preform a specific gradient descent (main loop included below) and depending on the initial conditions I will alternatively get good looking results (perhaps 20% of the time) or everything becomes NaN (the other 80% of the time). However it seems to me that none of the operations in my code could produce NaN's when given honest numbers! My main loop is: // calculate errors delta = m1 + m2 - M; eta = f1 + f2 - F; for (int i = 0; i < numChildren; i++) { epsilon[i] = p[i]*m1+(1-p[i])*m2+q[i]*f1+(1-q[i])*f2-C[i]; } // use errors in gradient descent // set aside differences for the p's and q's float mDiff = m1 - m2; float fDiff = f1 - f2; // first update m's and f's m1 -= rate*delta; m2 -= rate*delta; f1 -= rate*eta; f2 -= rate*eta; for (int i = 0; i < numChildren; i++) { m1 -= rate*epsilon[i]*p[i]; m2 -= rate*epsilon[i]*(1-p[i]); f1 -= rate*epsilon[i]*q[i]; f2 -= rate*epsilon[i]*(1-q[i]); } // now update the p's and q's for (int i = 0; i < numChildren; i++) { p[i] -= rate*epsilon[i]*mDiff; q[i] -= rate*epsilon[i]*fDiff; } This behavior can be seen when we have rate = 0.01; M = 30; F = 30; C = {15, 25, 35, 45}; with the p[i] and q[i] chosen randomly uniformly between 0 and 1, m1 and m2 chosen randomly uniformly to add to M, and f1 and f2 chosen randomly uniformly to add up to F. Does anyone see anything that could create these NaN's?

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  • What is the use of reflection in Java/C# etc

    - by zengr
    I was just curious, why should we use reflection in the first place? // Without reflection Foo foo = new Foo(); foo.hello(); // With reflection Class cls = Class.forName("Foo"); Object foo = cls.newInstance(); Method method = cls.getMethod("hello", null); method.invoke(foo, null); We can simply create an object and call the class's method, but why do the same using forName, newInstance and getMthod functions? To make everything dynamic?

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  • What are the alternatives for Java authentication?

    - by Crusader
    Preferably something that integrates well with a Flex front end. Yes the Spring Security guys say this is possible, but all examples seem to use legacy jsp tag libraries making them half useless as examples. I don't want to spend a month setting up and learning how to use a security tool. I would like a tool which supports using annotations (@RolesAllowed etc), MINIMAL XML, and 'remember-me' features (not cookie based). Apache Shiro seems to support Flex/Silverlight/Swing as well but I'd like to know if there are any other alternatives that are NOT container specific.

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  • Java - Syntax Question: What is <? super T>

    - by aloh
    I'm having trouble understanding the following syntax: public class SortedList< T extends Comparable< ? super T> > extends LinkedList< T > I see that class SortedList extends LinkedList. I just don't know what T extends Comparable< ? super T> means. My understanding of it so far is that type T must be a type that implements Comparable...but what is "< ? super T "?

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  • Help with float numbers in Java

    - by Alvin
    Hi, Could anyone please me why the output of the following programme is not " different different"? public static void main(String[] args) { float f1=3.2f; float f2=6.5f; if(f1==3.2) System.out.println("same"); else System.out.println("different"); if(f2==6.5) System.out.println("same"); else System.out.println("different"); } o/p :different same

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  • Maven easyb plugin java heap space settings?

    - by vinnu
    Hi, I attempted to change my heap size for maven easyb plugin http://www.easyb.org/maven-easyb-plugin/. In my easyb test I added standard code to print the heap size using the code Runtime.getFreeMemory() and Runtime.getTotalMemory(). I tried setting the MAVEN_OPTS=-Xmx1024m -Xms1024m and also set the maven opts in Maven surefire plugin. Now when I run the same class from the Junit I can see the getTotalMemory() displaying a number close 1Gig but the when the same classes are invoked from easyb plugin they do not reflect the memory size. Shouldn't there be a way of passing JVM opts to maven easyb plugin when it runs these easyb tests? At the very minimum it should atleast pick up the MAVEN_OPTS settings from the environment. Has someone bumped into problems like this? (A search on this group's archive does not reveal much)

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  • java overloaded method

    - by Sean Nguyen
    Hi, I have an abstract template method: class abstract MyTemplate { public void something(Object obj) { doSomething(obj) } protected void doSomething(Object obj); } class MyImpl extends MyTemplate { protected void doSomething(Object obj) { System.out.println("i am dealing with generic object"); } protected void doSomething(String str) { System.out.println("I am dealing with string"); } } public static void main(String[] args) { MyImpl impl = new MyImpl(); impl.something("abc"); // --> this return "i am dealing with generic object" } How can I print "I am dealing with string" w/o using instanceof in doSomething(Object obj)? Thanks,

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  • What is an Enterprise Java Bean really?

    - by HDave
    On the Tomcat FAQ it says: "Tomcat is not an EJB server. Tomcat is not a full J2EE server." But if I: use Spring to supply an application context annotate my entities with JPA annotations (and use Hibernate as a JPA provider) configure C3P0 as a connection pooling data source annotate my service methods with @Transactional (and use Atomikos as JTA provider) Use JAXB for marshalling and unmarshalling and possibly add my own JNDI capability then don't I effectively have a JEE application server? And then aren't my beans EJBs? Or is there some other defining characteristic? What is it that a JEE compliant app server gives you that you can't easily/readily get from Tomcat with some 3rd party subsystems?

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  • Java BCEL creating method with sipush?

    - by user1446924
    Well, I'm trying to recreate this method : public int getBaseX() { return this.x + 10000; } and it returns these instructions 0 aload_0 1 getfield #18 <TestClass.x> 4 sipush 10000 7 iadd 8 ireturn Now I'm having trouble withe the sipush, iadd. ClassGen injCG = cg; ConstantPoolGen cpg = injCG.getConstantPool(); InstructionList il = new InstructionList(); MethodGen mg = new MethodGen(Constants.ACC_PUBLIC, f.getType(), Type.NO_ARGS, null, name, injCG.getClassName(), il, cpg); InstructionFactory instrF = new InstructionFactory(injCG, cpg); if (!f.isStatic()) il.append(new org.apache.bcel.generic.ALOAD(0)); il.append(instrF.createFieldAccess(cg.getClassName(), f.getName(), f.getType(), (f.isStatic() ? Constants.GETSTATIC : Constants.GETFIELD))); il.append(InstructionFactory.createPop(1000)); il.append(InstructionFactory.createReturn(f.getType())); //il.append(InstructionFactory.createReturn(f.getType()), InstructionFactory.createDup(1000)); mg.setMaxLocals(); mg.setMaxStack(); injCG.addMethod(mg.getMethod()); that's what I have tried, but failed.

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  • Java - JPA - @Version annotation

    - by Yatendra Goel
    I am new to JPA. I am cofused about the @Version annotation. How it works? I have googled it and found various answers whose extract is as follows: JPA uses a version field in your entities to detect concurrent modifications to the same datastore record. When the JPA runtime detects an attempt to concurrently modify the same record, it throws an exception to the transaction attempting to commit last. But still I am not sure how it works? ================================================================================== Also as from the following lines: You should consider version fields immutable. Changing the field value has undefined results. Does it mean that we should declare our version field as final

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  • Java File manipulation

    - by user69514
    So I have an application with a JFileChooser from which I select a file to read. Then I change some words and write a new file. The problem that I am having is that when I write the new file it's saved in the project directory. How do I save it in the same directory as the file that I chose using the JFileChooser. Note: I don't want to use the JFileChooser to choose the location. I just need to save the file in the same directory as the original file that I read.

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  • java: how to parse html-like xml

    - by Yang
    I have an html-like xml, basically it is html. I need to get the elements in each . Each element looks like this: <line tid="744476117"> <attr>1414</attr> <attr>31</attr><attr class="thread_title">title1</attr><attr>author1</attr><attr>date1</attr></line> My code is as below, it does recognize that there are 50 in the file, but it gives me NULLPointException when parsing NodeList fstNmElmntLst = fstElmnt.getElementsByTagName("attr"); Any idea why this is happening? The same code has been used for other applications without problems. DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); DocumentBuilder db = dbf.newDocumentBuilder(); InputSource is = new InputSource(); is.setCharacterStream(new StringReader(cleanxml)); Document doc = db.parse(is); doc.getDocumentElement().normalize(); System.out.println("Root element " + doc.getDocumentElement().getNodeName()); NodeList nodeLst = doc.getElementsByTagName("line"); for (int s = 0; s < nodeLst.getLength(); s++) { System.out.println(nodeLst.getLength()); Node fstNode = nodeLst.item(s); if (fstNode.getNodeType() == Node.ELEMENT_NODE) { Element fstElmnt = (Element) fstNode; NodeList fstNmElmntLst = fstElmnt.getElementsByTagName("attr"); Element fstNmElmnt = (Element) fstNmElmntLst.item(0); NodeList fstNm = fstNmElmnt.getChildNodes(); System.out.println("attr : " + ((Node) fstNm.item(0)).getNodeValue()); } }

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  • Java Recursion Triangle Standing on Tip

    - by user1629075
    I was wondering how to create triangle out of asterisks on its tip rather than on its base. I have the code for making it stand on its base: public static String printTriangle (int count) { if( count <= 0 ) return ""; String p = printTriangle(count - 1); p = p + "*"; System.out.print(p); System.out.print("\n"); return p; } But then I'm stuck on how to have the greatest number of stars on the top, and then the next least, and so on. I was thinking something along the terms of having (count - p) to have the input of rows be subtracted from the amount of decrease, but then i was confused by this idea because p is string. EDIT: I tried changing the position of printTriangle(count - 1) using my original method without iterations and got 1 star per each line; how can I fix this? public class triangles { public static void main(String[] args) { printTriangle(5); } public static String printTriangle (int count) { if( count <= 0 ) return ""; String p = ""; p = p + "*"; System.out.print(p); System.out.print("\n"); p = printTriangle(count - 1); return p; } }

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  • Java - Regex problem

    - by Yatendra Goel
    I have a list of urls of type http://www.abc.com/pk/ca and http://www.abc.com/pk Now, I want to find out only those urls that ends with /pk or /pk/ and don't have anything in between .com and /pk

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  • Java - Regex problem

    - by Yatendra Goel
    I have list of urls of types: http://www.abc.com/pk/etc http://www.abc.com/pk/etc/ http://www.abc.com/pk/etc/etc where etc can be anything. So I want to search only those urls that contains www.abc.com/pk/etc or www.abc.com/pk/etc/

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