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  • What is faster- Java or C# (Or good old C)?

    - by Rexsung
    I'm currently deciding on a platform to build a scientific computational product on, and am deciding on either C#, Java, or plain C with Intels compiler on Core2 Quad CPU's. It's mostly integer arithmetic. My benchmarks so far show Java and C are about on par with each other, and dotNET/C# trails by about 5%- however a number of my coworkers are claiming that dotNET with the right optimizations will beat both of these given enough time for the JIT to do its work. I always assume that the JIT would have done it's job within a few minutes of the app starting (Probably a few seconds in my case, as it's mostly tight loops), so I'm not sure whether to believe them Can anyone shed any light on the situation? Would dotNET beat Java? (Or am I best just sticking with C at this point?). The code is highly multithreaded and data sets are several terabytes in size. Haskell/erlang etc are not options in this case as there is a significant quantity of existing legacy C code that will be ported to the new system, and porting C to Java/C# is a lot simpler than to Haskell or Erlang. (Unless of course these provide a significant speedup). Edit: We are considering moving to C# or Java because they may, in theory, be faster. Every percent we can shave off our processing time saves us tens of thousands of dollars per year. At this point we are just trying to evaluate whether C, Java, or c# would be faster.

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  • JAVA Casting error

    - by user1612725
    Im creating a program that uses Dijksrtras algorithm, im using nodes that represent cities on an imported map, and you can create edges between two cities on the map. My problem is every edge has a "weight" where it will represent distance in minutes and i have a function where i want to see the distance between the two edges. But i keep getting the error "Cannot cast from Stad to Edge" at the line Edge<Stad> selectedEdge = (Edge) fvf.visaFörbLista.getSelectedValue(); where "Stad" represents the city and "Edge" an edge. FormVisaförbindelse fvf = new FormVisaförbindelse(); for(;;){ try{ int svar = showConfirmDialog(null, fvf, "Ändra Förbindelser", JOptionPane.OK_CANCEL_OPTION); if (svar != YES_OPTION) return; if (fvf.visaFörbLista.isSelectionEmpty() == true){ showMessageDialog(mainMethod.this, "En Förbindelse måste valjas.","Fel!", ERROR_MESSAGE); return; } Edge<Stad> selectedEdge = (Edge) fvf.visaFörbLista.getSelectedValue(); FormÄndraförbindelse faf = new FormÄndraförbindelse(); faf.setförbNamn(selectedEdge.getNamn()); for(;;){ try{ int svar2 = showConfirmDialog(mainMethod.this, faf, "Ändra Förbindelse", OK_CANCEL_OPTION); if (svar2 != YES_OPTION) return; selectedEdge.setVikt(faf.getförbTid()); List<Edge<Stad>> edges = lg.getEdgesBetween(sB, sA); for (Edge<Stad> edge : edges){ if (edge.getNamn()==selectedEdge.getNamn()){ edge.setVikt(faf.getförbTid()); } } return; } catch(NumberFormatException e){ showMessageDialog(mainMethod.this, "Ogiltig inmatning.","Fel!", ERROR_MESSAGE); }

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  • Object Literals In Java?

    - by jjacquay712
    I am learning GWT for web development and came across a piece of code I can't really understand. helloBtn.addClickHandler(new ClickHandler() { public void onClick(ClickEvent event) { Window.alert("Hello!"); } }); If someone could explain to me what it is doing that would be great. Thanks, John

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  • A linked list with multiple heads in Java

    - by Emile
    Hi, I have a list in which I'd like to keep several head pointers. I've tried to create multiple ListIterators on the same list but this forbid me to add new elements in my list... (see Concurrent Modification exception). I could create my own class but I'd rather use a built-in implementation ;) To be more specific, here is an inefficient implementation of two basic operations and the one wich doesn't work : class MyList <E { private int[] _heads; private List<E _l; public MyList ( int nbHeads ) { _heads = new int[nbHeads]; _l = new LinkedList<E(); } public void add ( E e ) { _l.add(e); } public E next ( int head ) { return _l.get(_heads[head++]); // ugly } } class MyList <E { private Vector<ListIterator<E _iters; private List<E _l; public MyList ( int nbHeads ) { _iters = new Vector<ListIterator<E(nbHeads); _l = new LinkedList<E(); for( ListIterator<E iter : _iters ) iter = _l.listIterator(); } public void add ( E e ) { _l.add(e); } public E next ( int head ) { // ConcurrentModificationException because of the add() return _iters.get(head).next(); } } Emile

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  • Networking multiple computers to one brain in Java

    - by Morpheous
    Hello, I was wondering which libraries or API's would be useful in this. what im aiming for is to be able to type a command into a prompt and then specify which computer(out of all of them that are networked together) to execute that command on. the second part is i want to be able to see that command execute and the result on the computer that was specified. for example if i enter "firefox www.google.com, desktop2" i want to be able to see the window open on the monitor of that computer. Do you understand what im trying to do? any help is appreciated. Thanks, Morpheous

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  • Java : HTTP POST Request

    - by SpunkerBaba
    I have to do a http post request to a web-service for authenticating the user with username and password. The Web-service guy gave me following information to construct HTTP Post request. POST /login/dologin HTTP/1.1 Host: webservice.companyname.com Content-Type: application/x-www-form-urlencoded Content-Length: 48 id=username&num=password&remember=on&output=xml The XML Response that i will be getting is <?xml version="1.0" encoding="ISO-8859-1"?> <login> <message><![CDATA[]]></message> <status><![CDATA[true]]></status> <Rlo><![CDATA[Username]]></Rlo> <Rsc><![CDATA[9L99PK1KGKSkfMbcsxvkF0S0UoldJ0SU]]></Rsc> <Rm><![CDATA[b59031b85bb127661105765722cd3531==AO1YjN5QDM5ITM]]></Rm> <Rl><![CDATA[[email protected]]]></Rl> <uid><![CDATA[3539145]]></uid> <Rmu><![CDATA[f8e8917f7964d4cc7c4c4226f060e3ea]]></Rmu> </login> This is what i am doing HttpPost postRequest = new HttpPost(urlString); How do i construct the rest of the parameters?

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  • Java webapp: where/how to automatically set each picture's width/height

    - by NoozNooz42
    For several reasons, a lot of "webmaster guides" (like Google and Yahoo!'s webmaster guides/guidelines) repeats several times that it is better to always put the width and height attribute of the img tag. One of the most obvious reason is that the elements in the page won't seem to be "jumping around" to a new location after every picture is loaded (always setting the correct width/height sure gets rid of this behavior). And there are other reasons to follow these guidelines / best practices. So: if we consider that these are indeed good practices if there are a lot of pictures and they are changing often if pictures aren't changing between two .war re-deploy (that is: there's no user-contributed picture) if we don't want to manually edit all these width/height attributes How do we automatically/programmatically serve HTML pages where every img tag have their width/height attribute correctly set as the best practice recommend?

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  • Java anonymous class efficiency implications

    - by Po
    Is there any difference in efficiency (e.g. execution time, code size, etc.) between these two ways of doing things? Below are contrived examples that create objects and do nothing, but my actual scenarios may be creating new Threads, Listeners, etc. Assume the following pieces of code happen in a loop so that it might make a difference. Using anonymous objects: void doSomething() { for (/* Assume some loop */) { final Object obj1, obj2; // some free variables IWorker anonymousWorker = new IWorker() { doWork() { // do things that refer to obj1 and obj2 } }; } } Defining a class first: void doSomething() { for (/* Assume some loop */) { Object obj1, obj2; IWorker worker = new Worker(obj1, obj2); } } static class Worker implements IWorker { private Object obj1, obj2; public CustomObject(Object obj1, Object obj2) {/* blah blah */} @Override public void doWork() {} }; Thank you :)

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  • Java the little console game won't repeat?

    - by Jony Kale
    Okay, what I have so far is: You enter the game, and write "spin" to the console. Program will enter the while loop. In the while loop, if entered int is -1, return to the back (Set console input back to "", and let the user select what game he would like to play). Problem: Instead of going back, and selecting "spin" again, the program exits? Why is it happening? How can I fix this? private static Scanner console = new Scanner(System.in); private static Spin spin = new Spin(); private static String inputS = ""; private static int inputI = 0; private static String[] gamesArray = new String[] {"spin", "tof"}; private static boolean spinWheel = false; private static boolean tof = false; public static void main (String[] args) { if (inputS.equals("")) { System.out.println("Welcome to the system!"); System.out.print("Please select a game: "); inputS = console.nextLine(); } while (inputS.equals("spin")) { System.out.println("Welcome to the spin game! Please write 1 to spin. and -1 to exit back"); inputI = console.nextInt(); switch (inputI) { case 1: break; case -1: inputI = 0; inputS = ""; break; } } }

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  • Detecting incorrect key using AES/GCM in JAVA

    - by 4r1y4n
    I'm using AES to encrypt/decrypt some files in GCM mode using BouncyCastle. While I'm proving wrong key for decryption there is no exception. How should I check that the key is incorrect? my code is this: SecretKeySpec incorrectKey = new SecretKeySpec(keyBytes, "AES"); IvParameterSpec ivSpec = new IvParameterSpec(ivBytes); Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding", "BC"); byte[] block = new byte[1048576]; int i; cipher.init(Cipher.DECRYPT_MODE, incorrectKey, ivSpec); BufferedInputStream fis=new BufferedInputStream(new ProgressMonitorInputStream(null,"Decrypting ...",new FileInputStream("file.enc"))); BufferedOutputStream ro=new BufferedOutputStream(new FileOutputStream("file_org")); CipherOutputStream dcOut = new CipherOutputStream(ro, cipher); while ((i = fis.read(block)) != -1) { dcOut.write(block, 0, i); } dcOut.close(); fis.close(); thanks

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  • java serialization and final fields

    - by mdma
    I have an class defining an immutable value type that I now need to serialize. The immutability comes from the final fields which are set in the constructor. I've tried serializing, and it works (surprisingly?) - but I've no idea how. Here's an example of the class public class MyValueType implements Serializable { private final int value; private transient int derivedValue; public MyValueType(int value) { this.value = value; this.derivedValue = derivedValue(value); } // getters etc... } Given that the class doesn't have a no arg constructor, how can it be instantiated and the final field set? (An aside - I noticed this class particularly because IDEA wasn't generating a "no serialVersionUID" inspection warning for this class, yet successfully generated warnings for other classes that I've just made serializable.)

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  • Issues while downloading document from Sharepoint using JAVA

    - by Deepak Singh Rawat
    I am trying to download a file from Sharepoint 2007 sp2 document library using GetItem method of the Copy webservice. I am facing the following issues : In the local instance ( Windows Vista ) I can save only 10.5 Kb of any file. The webservice is returning only 10.5 Kb of data for any file. On the production server, I am able to List the documents using some credentials but when I am trying to download a document using the same credentials I get a 401 : Unauthorized message. I can download the document using the Sharepoint website successfully.

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  • Static variables in Java for a test oObject creator

    - by stevebot
    Hey, I have something like the following TestObjectCreator{ private static Person person; private static Company company; static { person = new Person() person.setName("Joe"); company = new Company(); company.setName("Apple"); } public Person createTestPerson(){ return person; } public Person createTestCompany(){ return company; } } By applying static{} what am I gaining? I assume the objects are singletons as a result. However, if I did the following: Person person = TestObjectCreator.createTestPerson(); person.setName("Jill"); Person person2 = TestObjectCreator.createTestPerson(); would person2 be named Jill or Joe?

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  • Java Scanner won't follow file

    - by Steve Renyolds
    Trying to tail / parse some log files. Entries start with a date then can span many lines. This works, but does not ever see new entries to file. File inputFile = new File("C:/test.txt"); InputStream is = new FileInputStream(inputFile); InputStream bis = new BufferedInputStream(is); //bis.skip(inputFile.length()); Scanner src = new Scanner(bis); src.useDelimiter("\n2010-05-01 "); while (true) { while(src.hasNext()){ System.out.println("[ " + src.next() + " ]"); } } Doesn't seem like Scanner's next() or hasNext() detects new entries to file. Any idea how else I can implement, basically, a tail -f with custom delimiter. ok - using Kelly's advise i'm checking & refreshing the scanner, this works. Thank you !! if anyone has improvement suggestions plz do! File inputFile = new File("C:/test.txt"); InputStream is = new FileInputStream(inputFile); InputStream bis = new BufferedInputStream(is); //bis.skip(inputFile.length()); Scanner src = new Scanner(bis); src.useDelimiter("\n2010-05-01 "); while (true) { while(src.hasNext()){ System.out.println("[ " + src.next() + " ]"); } Thread.sleep(50); if(bis.available() > 0){ src = new Scanner(bis); src.useDelimiter("\n2010-05-01 "); } }

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  • Java XMLRPC request-String

    - by Philip
    Hi, I'm using Apache XML-RPC 3.1.2 to talk to an online-service. They have something special, they need a hash over the whole XML with a secret key for some kind of security, like this: String hash = md5(xmlRequest + secretKey); String requestURL = "http://foo.bar/?authHash=" + hash; So I need the XML-request like this: <?xml version="1.0"?> <methodCall> <methodName>foo.bar</methodName> <params> <param> <value><struct> <member><name>bla</name> <value><int>1</int></value> </member> <member><name>blubb</name> <value><int>2</int></value> </member> </struct></value> </param> </params> </methodCall> But how do I get this String-representation of the XMLRPC-Request with the lib Apache XML-RPC?

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  • How to pause a thread in java?

    - by mithun1538
    Consider the following code: while(true) { someFunction(); Thread.sleep(1000); } What I want is that, someFunction() be called once every 10 seconds. But this is not the case. It is being called every second. I tried Thread.wait(1000), but even that doesnt help. I removed of the while part, just kept the body, and at the end wrote : Thread.start(); But it throwed an exception. Is there any other solution to this?

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  • java source code doubt

    - by abson
    this compiles class ex1 { public int show() { try { int a=10/10; return 10;} catch(ArithmeticException e) { System.out.println(e); } finally { System.out.println("Finally");} System.out.println("hello"); return 20; } } on the other hand this doesn't class ex15 { public int show() { try { int a=10/0; return 10;} catch(ArithmeticException e) { System.out.println(e); } finally { System.out.println("Finally"); return 40;} System.out.println("hello"); return 20; } } why is it so?

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  • Java How to call method of grand parents?

    - by Arkaha
    Let's assume I have 3 classes A, B and C, each one extending the previous one. How do I call the code in A.myMethod() from C.myMethod() if B also implements myMethod? class A { public void myMethod() { // some stuff for A } } class B extends A { public void myMethod() { // some stuff for B //and than calling A stuff super.myMethod(); } } class C extends B { public void myMethod() { // some stuff for C // i don't need stuff from b, but i need call stuff from A // something like: super.super.myMethod(); ?? how to call A.myMethod(); ?? } }

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  • Java Swing TanleModel fireTableRowsInserted on EDT

    - by Ayman
    I have a TableModel that is populated from a background running thread. I am calling fireTableRowsInserted when data is inserted, which is NOT on the EDT. My question is, do I need to use invokeLater for the fireTableRowsInserted? In other words, is the below correct: public void putData(TableRow row) { // we are not on the EDT here... rows.add(row); fireTableRowsInserted(rows.size()-1, rows.size()-1); }

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  • Java: why can't iterate over an iterator?

    - by noamtm
    I read http://stackoverflow.com/questions/839178/why-is-javas-iterator-not-an-iterable and http://stackoverflow.com/questions/27240/why-arent-enumerations-iterable, but I still don't understand why this: void foo(Iterator<X> it) { for (X x : it) { bar(x); baz(x); } } was not made possible. In other words, unless I'm missing something, the above could have been nice and valid syntactic sugar for: void foo(Iterator<X> it) { for (X x; it.hasNext();) { x = it.next(); bar(x); baz(x); } }

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  • Java method keyword "final" and its use

    - by Lukas Eder
    When I create complex type hierarchies (several levels, several types per level), I like to use the final keyword on methods implementing some interface declaration. An example: interface Garble { int zork(); } interface Gnarf extends Garble { /** * This is the same as calling {@link #zblah(0)} */ int zblah(); int zblah(int defaultZblah); } And then abstract class AbstractGarble implements Garble { @Override public final int zork() { ... } } abstract class AbstractGnarf extends AbstractGarble implements Gnarf { // Here I absolutely want to fix the default behaviour of zblah // No Gnarf shouldn't be allowed to set 1 as the default, for instance @Override public final int zblah() { return zblah(0); } // This method is not implemented here, but in a subclass @Override public abstract int zblah(int defaultZblah); } I do this for several reasons: It helps me develop the type hierarchy. When I add a class to the hierarchy, it is very clear, what methods I have to implement, and what methods I may not override (in case I forgot the details about the hierarchy) I think overriding concrete stuff is bad according to design principles and patterns, such as the template method pattern. I don't want other developers or my users do it. So the final keyword works perfectly for me. My question is: Why is it used so rarely in the wild? Can you show me some examples / reasons where final (in a similar case to mine) would be very bad?

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