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  • Getting Active Session counts with JMX (Java Management Extensions) API

    - by bLee
    I'm trying to use JMX API to get active session counts for a web application. Is it possible to use JMX API to get this kind of information? If yes, how reliable would it be? Any example code on how to get this done? I've been reading JMX tutorial and documentation, but they are giving me the overview of what the technology is. I just can't pinpoint to what I need, yet.

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  • making a java panel fullscreen

    - by clamp
    hello, how would you make a JComponent (panel, frame, window, etc.) fullscreen so that it also overlaps everything on the screen including the windows startbar? i dont want to change the resolution or anything with the graphics device like bitdepth etc, i just want to overlap everything else. thanks!

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  • Encrypted AES key too large to Decrypt with RSA (Java)

    - by Petey B
    Hello, I am trying to make a program that Encrypts data using AES, then encrypts the AES key with RSA, and then decrypt. However, once i encrypt the AES key it comes out to 128 bytes. RSA will only allow me to decrypt 117 bytes or less, so when i go to decrypt the AES key it throws an error. Relavent code: KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA"); kpg.initialize(1024); KeyPair kpa = kpg.genKeyPair(); pubKey = kpa.getPublic(); privKey = kpa.getPrivate(); updateText("Private Key: " +privKey +"\n\nPublic Key: " +pubKey); updateText("Encrypting " +infile); //Genereate aes key KeyGenerator kgen = KeyGenerator.getInstance("AES"); kgen.init(128); // 192/256 SecretKey aeskey = kgen.generateKey(); byte[] raw = aeskey.getEncoded(); SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); updateText("Encrypting data with AES"); //encrypt data with AES key Cipher aesCipher = Cipher.getInstance("AES"); aesCipher.init(Cipher.ENCRYPT_MODE, skeySpec); SealedObject aesEncryptedData = new SealedObject(infile, aesCipher); updateText("Encrypting AES key with RSA"); //encrypt AES key with RSA Cipher cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.ENCRYPT_MODE, pubKey); byte[] encryptedAesKey = cipher.doFinal(raw); updateText("Decrypting AES key with RSA. Encrypted AES key length: " +encryptedAesKey.length); //decrypt AES key with RSA Cipher decipher = Cipher.getInstance("RSA"); decipher.init(Cipher.DECRYPT_MODE, privKey); byte[] decryptedRaw = cipher.doFinal(encryptedAesKey); //error thrown here because encryptedAesKey is 128 bytes SecretKeySpec decryptedSecKey = new SecretKeySpec(decryptedRaw, "AES"); updateText("Decrypting data with AES"); //decrypt data with AES key Cipher decipherAES = Cipher.getInstance("AES"); decipherAES.init(Cipher.DECRYPT_MODE, decryptedSecKey); String decryptedText = (String) aesEncryptedData.getObject(decipherAES); updateText("Decrypted Text: " +decryptedText); Any idea on how to get around this?

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  • Using selection sort in java to sort floats

    - by user334046
    Hey, I need to sort an array list of class house by a float field in a certain range. This is my code for the selection sort: public ArrayList<House> sortPrice(ArrayList<House> x,float y, float z){ ArrayList<House> xcopy = new ArrayList<House>(); for(int i = 0; i<x.size(); i++){ if(x.get(i).myPriceIsLessThanOrEqualTo(z) && x.get(i).myPriceIsGreaterThanOrEqualTo(y)){ xcopy.add(x.get(i)); } } ArrayList<House> price= new ArrayList<House>(); while(xcopy.size()>0){ House min = xcopy.get(0); for(int i = 1; i < xcopy.size();i++){ House current = xcopy.get(i); if (current.myPriceIsGreaterThanOrEqualTo(min.getPrice())){ min = current; } } price.add(min); xcopy.remove(min); } return price; } Here is what the house class looks like: public class House { private int numBedRs; private int sqft; private float numBathRs; private float price; private static int idNumOfMostRecentHouse = 0; private int id; public House(int bed,int ft, float bath, float price){ sqft = ft; numBathRs = bath; numBedRs = bed; this.price = price; idNumOfMostRecentHouse++; id = idNumOfMostRecentHouse; } public boolean myPriceIsLessThanOrEqualTo(float y){ if(Math.abs(price - y)<0.000001){ return true; } return false; } public boolean myPriceIsGreaterThanOrEqualTo(float b){ if(Math.abs(b-price)>0.0000001){ return true; } return false; } When i call looking for houses in range 260000.50 to 300000 I only get houses that are at the top of the range even though I have a lower value at 270000. Can someone help?

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  • Java (Tomcat): how to configure a cookieless subdomain to serve static content

    - by Webinator
    One of the tip given by both Google and Yahoo! to speed up webpages loading is to configure a cookieless subdomain to server static content. How do you configure a "cookieless subdomain" using Tomcat in standalone mode (this question is not about how to use Apache to serve static content in a cookieless-way, but about how to do it in Tomcat-standalone mode)? Note that I don't care about filters supporting If-Modified-Since nor care about filters supporting gzipping: the static content I'm serving is forever cacheable (or its name will change) and it is already compressed data (so gzip would only slow down the transfer). Do I need two different Tomcat webapps? (one "cookiefull" and one "cookieless") Do I need two different servlets? (as of now I've got only one dispatcher/controller servlet). Why would a "regular" link to, say, a static image be called in a cookiefull way when it would be on the same domain as the main webapp and then be called in a "cookie-less" way when it is on a subdomain? I don't understand exactly what is going on: is it the browser that decides to append or not cookies to the query? If so, why would it not append the cookies to a static query on a "cookieless" subdomain. Any example as to what is going on behind the scene is most welcome :)

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  • Measure heap used by each object in Java

    - by Fazal
    Can some suggest a good a free memory profiling tool which will show memory being used by each object in the heap separately. We are trying to profile our application and I used jconsole but its gives me total memory usage only. I am using Eclipse and OC4J

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  • Exception hierarchy in java

    - by Abhishek Jain
    As Error and Exception are subclass of throwable class, we can throw any error, runtime ex and other ex. Also we can catch any of these type. Why do we usually catch only checked Exception? Can somebody provide me good links for exception with examples?

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  • Java - When to use Iterators?

    - by Walter White
    Hi all, I am trying to better understand when I should and should not use Iterators. To me, whenever I have a potentially large amount of data to iterate through, I write an Iterator for it. If it also lends itself to the Iterator interface, then it seems like a win. I was reading a little bit that there is a lot of overhead with using an Iterator. A good example of where I used an Iterator was to iterate through a bunch of SQL scripts to execute one query at a time, reading it in, then executing it. Is there another performance trade off I should be aware of? Before I used iterators, I would read the entire String of SQL commands to execute into an ArrayList, and the iterate through that. If the import is rather large (like for geolocation data, then the server tends to get bogged down). Walter

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  • Java-Swing: Change getSource() in ActionListener

    - by Brandon
    I have a class that contains a JButton. This can't be changed. The problem is this: The actionListener calls getSource() and gets the JButton, not the container class. Can I change what getSource retrieves, before the actionListener is added? OR can JButtons have a variable reference to its container? I can't make a class extend a JButton. It caused bugs for drawing purposes... story of my week.

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  • running multi threads in Java

    - by owca
    My task is to simulate activity of couple of persons. Each of them has few activities to perform in some random time: fast (0-5s), medium(5-10s), slow(10-20s) and very slow(20-30s). Each person performs its task independently in the same time. At the beginning of new task I should print it's random time, start the task and then after time passes show next task's time and start it. I've written run() function that counts time, but now it looks like threads are done one after another and not in the same time or maybe they're just printed in this way. public class People{ public static void main(String[] args){ Task tasksA[]={new Task("washing","fast"), new Task("reading","slow"), new Task("shopping","medium")}; Task tasksM[]={new Task("sleeping zzzzzzzzzz","very slow"), new Task("learning","slow"), new Task(" :** ","slow"), new Task("passing an exam","slow") }; Task tasksJ[]={new Task("listening music","medium"), new Task("doing nothing","slow"), new Task("walking","medium") }; BusyPerson friends[]={ new BusyPerson("Alice",tasksA), new BusyPerson("Mark",tasksM), new BusyPerson("John",tasksJ)}; System.out.println("STARTING....................."); for(BusyPerson f: friends) (new Thread(f)).start(); System.out.println("DONE........................."); } } class Task { private String task; private int time; private Task[]tasks; public Task(String t, String s){ task = t; Speed speed = new Speed(); time = speed.getSpeed(s); } public Task(Task[]tab){ Task[]table=new Task[tab.length]; for(int i=0; i < tab.length; i++){ table[i] = tab[i]; } this.tasks = table; } } class Speed { private static String[]hows = {"fast","medium","slow","very slow"}; private static int[]maxs = {5000, 10000, 20000, 30000}; public Speed(){ } public static int getSpeed( String speedString){ String s = speedString; int up_limit=0; int down_limit=0; int time=0; //get limits of time for(int i=0; i<hows.length; i++){ if(s.equals(hows[i])){ up_limit = maxs[i]; if(i>0){ down_limit = maxs[i-1]; } else{ down_limit = 0; } } } //get random time within the limits Random rand = new Random(); time = rand.nextInt(up_limit) + down_limit; return time; } } class BusyPerson implements Runnable { private String name; private Task[] person_tasks; private BusyPerson[]persons; public BusyPerson(String s, Task[]t){ name = s; person_tasks = t; } public BusyPerson(BusyPerson[]tab){ BusyPerson[]table=new BusyPerson[tab.length]; for(int i=0; i < tab.length; i++){ table[i] = tab[i]; } this.persons = table; } public void run() { int time = 0; double t1=0; for(Task t: person_tasks){ t1 = (double)t.time/1000; System.out.println(name+" is... "+t.task+" "+t.speed+ " ("+t1+" sec)"); while (time == t.time) { try { Thread.sleep(10); } catch(InterruptedException exc) { System.out.println("End of thread."); return; } time = time + 100; } } } } And my output : STARTING..................... DONE......................... Mark is... sleeping zzzzzzzzzz very slow (36.715 sec) Mark is... learning slow (10.117 sec) Mark is... :** slow (29.543 sec) Mark is... passing an exam slow (23.429 sec) Alice is... washing fast (1.209 sec) Alice is... reading slow (23.21 sec) Alice is... shopping medium (11.237 sec) John is... listening music medium (8.263 sec) John is... doing nothing slow (13.576 sec) John is... walking medium (11.322 sec) Whilst it should be like this : STARTING..................... DONE......................... John is... listening music medium (7.05 sec) Alice is... washing fast (3.268 sec) Mark is... sleeping zzzzzzzzzz very slow (23.71 sec) Alice is... reading slow (15.516 sec) John is... doing nothing slow (13.692 sec) Alice is... shopping medium (8.371 sec) Mark is... learning slow (13.904 sec) John is... walking medium (5.172 sec) Mark is... :** slow (12.322 sec) Mark is... passing an exam very slow (27.1 sec)

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  • Java Prepared Statement arguments!

    - by Epitaph
    I am planning to replace repeatedly executed Statement objects with PreparedStatement objects to improve performance. I am using arguments like the MySQL function now(), and string variables. Most of the PreparedStatement queries I have seen contained constant values (like 10, and strings like "New York") as arguments used for the "?" in the queries. How would I go about using functions like now(), and variables as arguments? Is it necessary to use the "?"s in the queries instead of actual values? I am quite confounded.

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  • Using a priority queue in Java

    - by Bharat
    Forgive me if this is a tried question, but I'm having a little difficulty figuring it out. I currently have a class Node, and each 'node' is a square in a maze. I'm trying to implement the A* algorithm, so each of these nodes will have an f-cost (int) data member inside of it. I was wondering if there's a way that I can create a priority queue of these nodes, and set up the f-cost variable as the comparator? I've looked at examples online, but all I can find are String priority queues. Can I implement Comparator for the Node class? Would this allow me to access the data member stored inside it? Many Thanks!

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  • Bind a Java Collection to xQuery sequence from xQuery

    - by jtzero
    declare function Error:toString($this as javaObject) as xs:string external; the previous binds a return String() to xs:string. is it possible to return a collection and bind it to an xQuery Sequence, say the following declare function Error:toList($this as javaObject) as squenceType external; so that it can be run through a flwr?

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  • Java Generics Type Safety warning with recursive Hashmap

    - by GC
    Hi, I'm using a recursive tree of hashmaps, specifically Hashmap map where Object is a reference to another Hashmap and so on. This will be passed around a recursive algorithm: foo(String filename, Hashmap<String, Object> map) { //some stuff here for (Entry<String, Object> entry : map.entrySet()) { //type warning that must be suppressed foo(entry.getKey(), (HashMap<String, Object>)entry.getValue()); } } I know for sure Object is of type Hashmap<String, Object> but am irritated that I have to suppress the warning using @SuppressWarnings("unchecked"). I'll be satisfied with a solution that does either a assert(/*entry.getValue() is of type HashMap<String, Object>*/) or throws an exception when it isn't. I went down the Generics route for compile type safety and if I suppress the warning then it defeats the purpose. Thank you for your comments, ksb

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  • Java SQL database independence.

    - by Paul
    Hello, I have been looking for an alternative to Hibernate for various reasons. I came across Liquibase and i like the idea so i am willing to try it. Liquibase will cater for database creation/modification in a SQL independent fashion. My main question is how does my code in my application execute SQL statements without being database dependent? Is there some other project that acts like Hibernates Dialect classes? Thanks, Paul

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  • Recursive String Function (Java)

    - by Jake Brooks
    Hi, I am trying to design a function that essentially does as follows: String s = "BLAH"; store the following to an array: blah lah bah blh bla bl ba bh ah al So basically what I did there was subtract each letter from it one at a time. Then subtract a combination of two letters at a time, until there's 2 characters remaining. Store each of these generations in an array. Hopefully this makes sense, Jake

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  • Message Driven Bean with Java Message Queue down

    - by Rafa de Castro
    I have the following problem deploying my application. It uses JMS and a remote openMQ for communication between servers. The problem is that the connection is not fully reliable so it can be up or down. For reconnecting I set the jms reconnect glassfish property so it reconnects if at some moment the connection gets lost. The problem arises when i try to deploy the application and there is no connection. It looks like it keeps retrying the connection but the application does not finish deployment until connection is available. Is it possible to configure it in any way that the deployment continues even if there is no connection and keeps retrying until there is connection available? Thanks a lot.

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  • Extracting URIs from RDF web page in Java using Jena Library

    - by Prannoy Mittal
    I have written following code for extratcting URIs from a web page with content type application/rdf-xml for Linked Data application. public static void test(String url) { try { Model read = ModelFactory.createDefaultModel().read(url); System.out.println("to go"); StmtIterator si; si = read.listStatements(); System.out.println("to go"); while(si.hasNext()) { Statement s=si.nextStatement(); Resource r=s.getSubject(); Property p=s.getPredicate(); RDFNode o=s.getObject(); System.out.println(r.getURI()); System.out.println(p.getURI()); System.out.println(o.asResource().getURI()); } } catch(JenaException | NoSuchElementException c) { } } But above code is not extracting all URIs. It provides only few of the URIs. Please guide me where i Went wrong?? hey Rafeel For Eq: for XML File : <?xml version="1.0"?> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:ex="http://example.org/stuff/1.0/"> <rdf:Description rdf:about="http://www.w3.org/TR/rdf-syntax-grammar" dc:title="RDF/XML Syntax Specification (Revised)"> <ex:editor> <rdf:Description ex:fullName="Dave Beckett"> <ex:homePage rdf:resource="http://purl.org/net/dajobe/" /> </rdf:Description> </ex:editor> </rdf:Description> </rdf:RDF> The output is : Subject URI is http://www.w3.org/TR/rdf-syntax-grammar Predicate URI is http://example.org/stuff/1.0/editor Object URI is null Subject URI is http://www.w3.org/TR/rdf-syntax-grammar Predicate URI is http://purl.org/dc/elements/1.1/title Website is read

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  • Task queue java

    - by user268515
    Hi i'm new to Task queue concepts when i referred the guide I got struck on this line queue.add( DatastoreServiceFactory.getDatastoreService().getCurrentTransaction(), TaskOptions().url("/path/to/my/worker")); what is TaskOptions() method. Is it default method are method created manually what will TaskOptions() method will return. I created a method called TaskOption() when i to return a string value its saying error as "The method url(String) is undefined for the type String" In url what i want to specify servlet are any other. My doubt may be stupid but plz clarify it. Thank you, sharun.

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  • java: <identifier> expected with ArrayList

    - by A-moc
    I have a class named Storage. Storage contains an arraylist of special objects called Products. Each product contains information such as name, price, etc. My code is as follows: class Storage{ Product sprite = new Product("sprite",1.25,30); Product pepsi = new Product("pepsi",1.85,45); Product orange = new Product("orange",2.25,36); Product hershey = new Product("hershey",1.50,33); Product brownie = new Product("brownie",2.30,41); Product apple = new Product("apple",2.00,15); Product crackers = new Product("peanut",3.90,68); Product trailmix = new Product("trailmix",1.90,45); Product icecream = new Product("icecream",1.65,28); Product doughnut = new Product("doughnut",2.75,18); Product banana = new Product("banana",1.25,32); Product coffee = new Product("coffee",1.30,40); Product chips = new Product("chips",1.70,35); ArrayList<Product> arl = new ArrayList<Product>(); //add initial elements to arraylist arl.add(sprite); arl.add(pepsi); arl.add(orange); arl.add(hershey); arl.add(brownie); arl.add(apple); arl.add(peanut); arl.add(trailmix); arl.add(icecream); arl.add(doughnut); arl.add(banana); arl.add(coffee); arl.add(chips); } Whenever I compile, I get an error message on lines 141-153 stating <identifier> expected. I know it's an elementary problem, but I can't seem to figure this out. Any help is much appreciated.

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