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  • Close resources before exiting JFrame and TCP communication in Java

    - by Oz Molaim
    1. I'm writing a chat based application on TCP communication. I'm using NetBeans and I want to add functionality to the default EXIT_ON_CLOSE when exiting JFrame. The reason of course is because I want to clean resources and end threads safely. How can I call a method that clear resources and only then close the JFrame safely and end the process. 2. I need to implement the server side. The server has List/HashMap/Queue of 'Socket' with their chat nick-names. Is there any simple design pattern to do it correctly because I don't want to re-invent the wheel. thanks.

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  • Arrays- Square root of an Array and printing the result JAVA

    - by roger34
    Hello, The title says it all, really. I'm trying to get an array of (9) numbers squared then printed but I keep coming back with only one result - the number of numbers in the array squared- obviously not what I want. Thanks for any help. Ok, here is my terrible code so far. Trying to pass it to a method as well. public static void main ( String args[] ) { double[] nums = {126, 12.939, 795, 320.16, 110, 34.7676, 7773, 67, 567, 323}; System.out.println ("Square root is " +square); square(nums); } public static double square (double [] array) { double result; for( double i = 0; i < array.length ; i++ ) result = Math.sqrt(array[i]); return result; } }

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  • Java HTTP Request Occasionally Hangs

    - by behrk2
    Hello Everyone, For the majority of the time, my HTTP Requests work with no problem. However, occasionally they will hang. The code that I am using is set up so that if the request succeeds (with a response code of 200 or 201), then call screen.requestSucceeded(). If the request fails, then call screen.requestFailed(). When the request hangs, however, it does so before one of the above methods are called. Is there something wrong with my code? Should I be using some sort of best practice to prevent any hanging? The following is my code. I would appreciate any help. Thanks! HttpConnection connection = (HttpConnection) Connector.open(url + connectionParameters); connection.setRequestMethod(method); connection.setRequestProperty("WWW-Authenticate", "OAuth realm=api.netflix.com"); if (method.equals("POST")) { connection.setRequestProperty("Content-type", "application/x-www-form-urlencoded"); } int responseCode = connection.getResponseCode(); System.out.println("RESPONSE CODE: " + responseCode); if (connection instanceof HttpsConnection) { HttpsConnection secureConnection = (HttpsConnection) connection; String issuer = secureConnection.getSecurityInfo() .getServerCertificate().getIssuer(); UiApplication.getUiApplication().invokeLater( new DialogRunner( "Secure Connection! Certificate issued by: " + issuer)); } if (responseCode != 200 && responseCode != 201) { screen.requestFailed("Unexpected response code: " + responseCode); connection.close(); return; } String contentType = connection.getHeaderField("Content-type"); ByteArrayOutputStream baos = new ByteArrayOutputStream(); InputStream responseData = connection.openInputStream(); byte[] buffer = new byte[20000]; int bytesRead = 0; while ((bytesRead = responseData.read(buffer)) > 0) { baos.write(buffer, 0, bytesRead); } baos.close(); connection.close(); screen.requestSucceeded(baos.toByteArray(), contentType); } catch (IOException ex) { screen.requestFailed(ex.toString()); }

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  • Java regex basic usage problem

    - by Ernelli
    The following code works: String str= "test with foo hoo"; Pattern pattern = Pattern.compile("foo"); Matcher matcher = pattern.matcher(str); if(matcher.find()) { ... } But this example does not: if(Pattern.matches("foo", str)) { ... } And neither this version: if(str.matches("foo")) { ... } In the real code, str is a chunk of text with multiple lines if that is treated differently by the matcher, also in the real code, replace will be used to replace a string of text. Anyway, it is strange that it works in the first version but not the other two versions.

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  • Upload files with java

    - by Marius
    I'd like to upload a few files to a http server. Basically what i need is some sort of a post request to the server with a few parameters and the files. I've seen examples of just uploading files, but didn't find how to also pass additional parameters. So the question would be what's the simplest and free solution of doing this? Does anyone have any file upload examples that i could study? I've been googling for a few hours, but (maybe it's just one of those days) couldn't find exactly what i needed. The best solution would be something that doesn't involve any third party classes or libraries. Thank you

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  • Java Time Zone When Parsing DateFormat

    - by shipmaster
    I had code that parses date as follows: String ALT_DATE_TIME_FORMAT = "yyyy-MM-dd'T'HH:mm:ss.SSSZ"; SimpleDateFormat sdf = new SimpleDateFormat( ALT_DATE_TIME_FORMAT); Date date = sdf.parse(requiredTimeStamp); And it was working fine, suddenly, this stopped working. It turns out an admin made some config changes on the server and the date is currently being returned as "2010-12-27T10:50:44.000-08:00" which is not parse-able by the above pattern. I have two questions: The first would be what pattern would parse the date being returned by the JVM in the format above (specifically, just '-08:00' as the time zone)? And second, where exactly would one change such settings on a linux RHEL 5 server so that we are aware of such changes in the future?

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  • java.util.concurrent.ThreadPoolExecutor strange logic

    - by rodrigoap
    Look ath this method of ThreadPoolExcecutor: public void execute(Runnable command) { ... if (runState == RUNNING && workQueue.offer(command)) { if (runState != RUNNING || poolSize == 0) ensureQueuedTaskHandled(command); } ... } It check that runState is RUNNING and then the oposite. As I'm trying to do some tuning on a SEDA like model I wanted to understand the internals of the thread pool. Do you think this code is correct?

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  • How to set more panels in Java

    - by baklap
    I need to get two JPanels into one JApplet. paneel = new RekenmachinePaneel(); nummer = new NummerPaneel(); setContentPane(paneel); Now I need to get the nummer panel to show up beneath the paneel. How should I do that?

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  • Using XPath on String in Android (JAVA)

    - by Rav
    I am looking for some examples of using xpath in Android? Or if anyone can share their experiences. I have been struggeling to make tail or head of this problem :-( I have a string that contains a standard xml file. I believe I need to convert that into an xml document. I have found this code which I think will do the trick: public static Document stringToDom(String xmlSource) throws SAXException, ParserConfigurationException, IOException { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); return builder.parse(new InputSource(new StringReader(xmlSource))); } Next steps Assuming the code above is OK, I need to apply xpath to get values from cat: "/animal/mammal/feline/cat" I look at the dev doc here: http://developer.android.com/reference/javax/xml/xpath/XPath.html and also look online, but I am not sure where to start! I have tried to use the following code: XPathFactory xPathFactory = XPathFactory.newInstance(); // To get an instance of the XPathFactory object itself. XPath xPath = xPathFactory.newXPath(); // Create an instance of XPath from the factory class. String expression = "SomeXPathExpression"; XPathExpression xPathExpression = xPath.compile(expression); // Compile the expression to get a XPathExpression object. Object result = xPathExpression.evaluate(xmlDocument); // Evaluate the expression against the XML Document to get the result. But I get "Cannot be resolved". Eclipse doesn't seem to be able to fix this import. I tried manually entering: javax.xml.xpath.XPath But this did not work. Does anyone know any good source code that I can utilise, for Android platform? 1.5

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  • Calling a groovy script or Java from Javascript

    - by RenegadeAndy
    Hey! I have a cool bit of dojo running where I click a button - and it brings a success message on the screen via javascript. Is it possible to issue a call to a server side Groovy script foo.groovy from within this Javascript - because not only do I want to show the cool success message - but I need to do some work in the background at that point also. Thanks Andy

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  • java filenames filter pattern

    - by Sergey
    Hello, I need to implement File[] files = getFiles( String folderName, String ptrn ); Where ptrn is a command prompt style pattern like "*2010*.txt" I'm familar with FilenameFilter class, but can't implement public boolean accept(File dir, String filename) because String.matches() doesn't accept such patterns. Thanks!

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  • get static initialization block to run in a java without loading the class

    - by TP
    I have a few classes as shown here public class TrueFalseQuestion implements Question{ static{ QuestionFactory.registerType("TrueFalse", "Question"); } public TrueFalseQuestion(){} } ... public class QuestionFactory { static final HashMap<String, String > map = new HashMap<String,String>(); public static void registerType(String questionName, String ques ) { map.put(questionName, ques); } } public class FactoryTester { public static void main(String[] args) { System.out.println(QuestionFactory.map.size()); // This prints 0. I want it to print 1 } } How can I change TrueFalseQuestion Type so that the static method is always run so that I get 1 instead of 0 when I run my main method? I do not want any change in the main method. I am actually trying to implement the factory patterns where the subclasses register with the factory but i have simplified the code for this question.

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  • Java Convert ColorSpace of BufferedImage to CS_GRAY without using ConvertColorOp

    - by gmatt
    I know its possible to convert an image to CS_GRAY using public static BufferedImage getGrayBufferedImage(BufferedImage image) { BufferedImageOp op = new ColorConvertOp(ColorSpace .getInstance(ColorSpace.CS_GRAY), null); BufferedImage sourceImgGray = op.filter(image, null); return sourceImgGray; } however, this is a chokepoint of my entire program. I need to do this often, on 800x600 pixel images and takes about 200-300ms for this operation to complete, on average. I know I can do this alot faster by using one for loop to loop through the image data and set it right away. The code above on the other hand constructs a brand new 800x600 BufferedImage that is gray scale. I would rather just transform the image I pass in. Does any one know how to do this with a for loop and given that the image is RGB color space?

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  • Java Reflection Utility

    - by DD
    Is there a utility to get a property which isnt prefixed by get from an object using reflection similar to BeanUtils? e.g. if I specify "hashcode" and I want to get the object.hashcode() value. Thanks.

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  • Generate UML from java source

    - by Parhs
    Hello. Because i have a big project i must generate the UML for this...Writing UML for 300 classes is overkill... So is there any solution to generate the diagrams for me ? I am using Netbeans.... Thank you for reading

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  • Reformatting a Java String

    - by Travis
    I have a string that looks like this: CALDARI_STARSHIP_ENGINEERING and I need to edit it to look like Caldari Starship Engineering Unfortunately it's three in the morning and I cannot for the life of me figure this out. I've always had trouble with replacing stuff in strings so any help would be awesome and would help me understand how to do this in the future.

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  • Get the key and value of Map that is used Inside another Map (JAVA)

    - by Umair Iqbal
    I am using a map inside another map, The key of the outer map is Integer and the value is another Map. I get the values as expected but I don't know how to get the key and value of teh inner map. Here is the code Map<Integer, Map<Integer, Integer>> cellsMap = new HashMap<Integer, Map<Integer, Integer>>(); Map<Integer , Integer> bandForCell = cellsMap.get(band_number); if (bandForCell == null) bandForCell = new HashMap<Integer, Integer>(); bandForCell.put(erfcn, cell_found); cellsMap.put(band_number, bandForCell); csv.writeCells((Map<Integer, Map<Integer, Integer>>) cellsMap); public void writeCells (Map<Integer, Map<Integer, Integer>> cellsMap ) throws IOException { for (Map.Entry<Integer, Map<Integer, Integer>> entry : cellsMap.entrySet()) { System.out.println("Key: " + entry.getKey() + ". Value: " + entry.getValue() + "\n"); } } Out put of my Map Key: 20 Value: {6331=0, 6330=1, 6329=1, 6328=0, 6335=1, 6437=0, 6436=1} The value in the above output is another map. How can I get the key and value of the inner map from the value of the outer map? Like Keys of inner map = 6331, 6330, 6329 .... and values of inner map = 0 , 1 , 1 , 0 ... Thanks

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  • java and threads: very strange behaviour

    - by Derk
    private synchronized Map<Team, StandingRow> calculateStanding() { System.out.println("Calculate standing for group " + getName()); Map<Team, StandingRow> standing = new LinkedHashMap<Team, StandingRow>(); for (Team team : teams) { standing.put(team, new StandingRow(team)); } StandingRow homeTeamRow, awayTeamRow; for (Match match : matches.values()) { homeTeamRow = standing.get(match.getHomeTeam()); awayTeamRow = standing.get(match.getAwayTeam()); System.out.println("Contains key for " + match.getHomeTeam() + ": " + standing.containsKey(match.getHomeTeam())); System.out.println("Contains key for " + match.getAwayTeam() + ": " + standing.containsKey(match.getAwayTeam())); } } This is my code. matches contains 6 elements, but the problem is that after two matches no keys are anymore found in the standing map. The output is for example Contains key for Zuid-Afrika: true Contains key for Mexico: true Contains key for Uruguay: true Contains key for Frankrijk: true Contains key for Zuid-Afrika: false Contains key for Uruguay: false Contains key for Frankrijk: false Contains key for Mexico: false Contains key for Mexico: false Contains key for Uruguay: false Contains key for Frankrijk: false Contains key for Zuid-Afrika: false This is in a threaded environment, but the method is synchronized so I thought that this would not give a problem? I have also a simple unit test for this method and that works well.

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  • JAVA: storing input into array

    - by Jann
    I need to write a program where the program would generate random letter and i would need to store this random character into an array char[] arrayRandom = new char[10]; for (int i = 0; i < 8; i++) { randomNumLet = (generator.nextInt(20) + 1); System.out.print(arrayRandomLetter[randomNumLet] + " "); arrayRandomLetter[randomNumLet] = arrayRandom[i]; } is there anything wrong with my code? because when i run this and printed the array i get boxes for all the values in the array and there are some letter that this line of code cannot print System.out.print(arrayRandomLetter[randomNumLet] + " "); Thanks

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  • Java synchronized method lock on object, or method?

    - by wuntee
    If I have 2 synchronized methods in the same class, but each accessing different variables, can 2 threads access those 2 methods at the same time? Does the lock occur on the object, or does it get as specific as the variables inside the synchronized method? Example: class x{ private int a; private int b; public synchronized void addA(){ a++; } public synchronized void addB(){ b++; } } Can 2 threads access the same instance of class x performing x.addA() and x.addB() at the same time?

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  • Java multi Generic collection parameters complie error

    - by Geln Yang
    Hi, So strange!Please have a look the code first: public class A { } public class B extends A { } public class C extends A { } public class TestMain { public <T extends A> void test(T a, T b) { } public <T extends A> void test(List<T> a, List<T> b) { } public static void main(String[] args) { new TestMain().test(new B(), new C()); new TestMain().test(new ArrayList<B>(), new ArrayList<C>()); } } The statement "new TestMain().test(new ArrayList(), new ArrayList())" get a "Bound mismatch" compile error, while "new TestMain().test(new B(), new C())" is compiled ok. Bound mismatch: The generic method test(T, T) of type TestMain is not applicable for the arguments (ArrayList, ArrayList). The inferred type ArrayList is not a valid substitute for the bounded parameter It seems the type of the second generic List parameter is limited by the Type of the first.Is it a feature or a bug of the compile program? ps, jdk:1.6,IDE:Eclipse 3.5.1

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  • system out output for double numbers in a java program

    - by Nikunj Chauhan
    I have a program where I am generating two double numbers by adding several input prices from a file based on a condition. String str; double one = 0.00; double two = 0.00; BufferedReader in = new BufferedReader(new FileReader(myFile)); while((str = in.readLine()) != null){ if(str.charAt(21) == '1'){ one += Double.parseDouble(str.substring(38, 49) + "." + str.substring(49, 51)); } else{ two += Double.parseDouble(str.substring(38, 49) + "." + str.substring(49, 51)); } } in.close(); System.out.println("One: " + one); System.out.println("Two: " + two); The output is like: One: 2773554.02 Two: 6.302505836000001E7 Question: None of the input have more then two decimals in them. The way one and two are getting calculated exactly same. Then why the output format is like this. What I am expecting is: One: 2773554.02 Two: 63025058.36 Why the printing is in two different formats ? I want to write the outputs again to a file and thus there must be only two digits after decimal.

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  • Calling Subclass Method in Java

    - by destructo_gold
    Given the following situation (UML below), If Y has the method: public void PrintWs(); and X has: ArrayList <P> myPs = new ArrayList(); Y y = new Y(); Z z = new Z(); myPs.add(y); myPs.add(z); How do I loop through each myPs object and call all Ys PrintWs (without using instanceof)? http://starbucks.mirror.waffleimages.com/files/68/68c26b815e913acd00307bf27bde534c0f1f8bfb.jpg

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