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  • Avoiding RTTI In Java

    - by destructo_gold
    Hi, If I have a superclass, say Animal, and two subclasses: Zebra and Giraffe, If I decide to define a Vector of Animals: Vector <Animal> animals = new Vector(); and I want to say: You can add Giraffes, but you must own at least one Zebra first. What is the best way to do this without using RTTI? (instanceof)

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  • Implement a RSA algorithm in Java

    - by Robin Monjo
    Hello everyone. I want to implement a RSA algorithm to encrypt an image (byte[]). To generate my two keys I used this piece of code : KeyPairGenerator keygen = KeyPairGenerator.getInstance("RSA"); keygen.initialize(512); keyPair = keygen.generateKeyPair(); Once public and private key are generated, I would like to show them to the user so he can distribute the public key and use the private key to decode. How can I get back those key? Using keygen.getPrivateKey() and keygen.getPublicKey() give me all the information of the RSA algorithm, not only the keys I need. Thanks

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  • java casting a list

    - by dcp
    Let's say I had: protected void performLogic(List<Object> docs) { ... } In the code where I'm going to be calling this method, I have a List<String> list. I want to call performLogic, passing this list. But it won't work because the lists are 2 different types: public void execute() { List<String> docs = new ArrayList<String>(); performLogin(docs); // won't work } I tried casting to List<Object> also, but that won't work either. So is the only way to do this is to make a new ArrayList of Object and just add the values and then pass it? Just seems cumbersome. I wondered if there was a better way to do it. Thanks.

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  • Refactor java code

    - by Alfred
    I would like to refactor code which looks something like this: String input; // input from client socket. if (input.equals(x) { doX(); } else if (input.equals(y) { doY(); } else { unknown_command(); } It is code which checks input from socket to perform some action, but I don't like the if else construction because every time a new command is added to the server (code) a new if else has to be added which is ugly. Also when deleting a command the if else has to be modified.

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  • Any simple shape recognition libraries for Java?

    - by Phil
    I am working on a on-screen keyboard for Android, and I need to recognize starting points, turning points and end points of lines drawn by the user on the keyboard. A simple straightening function would be nice, as it is difficult to draw a perfectly straight line even with a stylus, not to mention finger-only touchscreens today. What I am trying to write is something like Swype. Any good libraries that I can use or make reference to?

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  • Permutation algorithm without recursion? Java

    - by Andreas Hornig
    Hi, I would like to get all combination of a number without any repetation. Like 0.1.2, 0.2.1, 1.2.0, 1.0.2, 2.0.1, 2.1.0. I tried to find an easy scheme but couldn't find so I drawed a graph/tree for it and this screams to use recursion. But I would like to do it without, if this is possible. So could anyone please help me how to do that? Thank you in advance, Andreas

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  • Binary Search Tree in Java

    - by John R
    I want to make a generic BST, that can be made up of any data type, but i'm not sure how I could add things to the tree, if my BST is generic. All of my needed code is below. I want my BST made up of Locations, and sorted by the x variable. Any help is appreciated. Major thanks for looking. public void add(E element) { if (root == null) root = element; if (element < root) add(element, root.leftChild); if (element > root) add(element, root.rightChild); else System.out.println("Element Already Exists"); } private void add(E element, E currLoc) { if (currLoc == null) currLoc = element; if (element < root) add(element, currLoc.leftChild); if (element > root) add(element, currLoc.rightChild); else System.out.println("Element Already Exists); } Other Code public class BinaryNode<E> { E BinaryNode; BinaryNode nextBinaryNode; BinaryNode prevBinaryNode; public BinaryNode() { BinaryNode = null; nextBinaryNode = null; prevBinaryNode = null; } } public class Location<AnyType> extends BinaryNode { String name; int x,y; public Location() { name = null; x = 0; y = 0; } public Location(String newName, int xCord, int yCord) { name = newName; x = xCord; y = yCord; } public int equals(Location otherScene) { return name.compareToIgnoreCase(otherScene.name); } }

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  • Java getMethod with superclass parameters in method

    - by Jonathon
    Given: class A { public void m(List l) { ... } } Let's say I want to invoke method m with reflection, passing an ArrayList as the parameter to m: List myList = new ArrayList(); A a = new A(); Method method = A.class.getMethod("m", new Class[] { myList.getClass() }); method.invoke(a, Object[] { myList }); The getMethod on line 3 will throw NoSuchMethodException because the runtime type of myList is ArrayList, not List. Is there a good generic way around this that doesn't require knowledge of class A's parameter types?

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  • Java Regex Matcher Question

    - by Yang
    How do I match an URL string like this: img src = "http://stackoverflow.com/a/b/c/d/someimage.jpg" where only the domain name and the file extension (jpg) is fixed while others are variables? The following code does not seem working: Pattern p = Pattern.compile("<img src=\"http://stachoverflow.com/.*jpg"); // Create a matcher with an input string Matcher m = p.matcher(url); while (m.find()) { String s = m.toString(); }

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  • Java servlet and UTF-8 problem

    - by Gabriele
    I have some problem with UTF-8. My client (realized in GWT) make a request to my servlet, with some parametres in the URL, as follow: http://localhost:8080/servlet?param=value When in the servlet I retrieve the URL, I have some problem with UTF-8 characters. I use this code: protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("UTF-8"); String reqUrl = request.getRequestURL().toString(); String queryString = request.getQueryString(); System.out.println("Request: "+reqUrl + "?" + queryString); ... So, if I call this url: http://localhost:8080/servlet?param=così the result is like this: Request: http://localhost:8080/servlet?param=cos%C3%AC What can I do to set up properly the character encoding?

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  • Is the Cloud ready for an Enterprise Java web application? Seeking a JEE hosting advice.

    - by Jakub Holý
    Greetings to all the smart people around here! I'd like to ask whether it is feasible or a good idea at all to deploy a Java enterprise web application to a Cloud such as Amazon EC2. More exactly, I'm looking for infrastructure options for an application that shall handle few hundred users with long but neither CPU nor memory intensive sessions. I'm considering dedicated servers, virtual private servers (VPSs) and EC2. I've noticed that there is a project called JBoss Cloud so people are working on enabling such a deployment, on the other hand it doesn't seem to be mature yet and I'm not sure that the cloud is ready for this kind of applications, which differs from the typical cloud-based applications like Twitter. Would you recommend to deploy it to the cloud? What are the pros and cons? The application is a Java EE 5 web application whose main function is to enable users to compose their own customized Product by combining the available Parts. It uses stateless and stateful session beans and JPA for persistence of entities to a RDBMS and fetches information about Parts from the company's inventory system via a web service. Aside of external users it's used also by few internal ones, who are authenticated against the company's LDAP. The application should handle around 300-400 concurrent users building their product and should be reasonably scalable and available though these qualities are only of a medium importance at this stage. I've proposed an architecture consisting of a firewall (FW) and load balancer supporting sticky sessions and https (in the Cloud this would be replaced with EC2's Elastic Load Balancing service and FW on the app. servers, in a physical architecture the load-balancer would be a HW), then two physical clustered application servers combined with web servers (so that if one fails, a user doesn't loose his/her long built product) and finally a database server. The DB server would need a slave backup instance that can replace the master instance if it fails. This should provide reasonable availability and fault tolerance and provide good scalability as long as a single RDBMS can keep with the load, which should be OK for quite a while because most of the operations are done in the memory using a stateful bean and only occasionally stored or retrieved from the DB and the amount of data is low too. A problematic part could be the dependency on the remote inventory system webservice but with good caching of its outputs in the application it should be OK too. Unfortunately I've only vague idea of the system resources (memory size, number and speed of CPUs/cores) that such an "average Java EE application" for few hundred users needs. My rough and mostly unfounded estimate based on actual Amazon offerings is that 1.7GB and a single, 2-core "modern CPU" with speed around 2.5GHz (the High-CPU Medium Instance) should be sufficient for any of the two application servers (since we can handle higher load by provisioning more of them). Alternatively I would consider using the Large instance (64b, 7.5GB RAM, 2 cores at 1GHz) So my question is whether such a deployment to the cloud is technically and financially feasible or whether dedicated/VPS servers would be a better option and whether there are some real-world experiences with something similar. Thank you very much! /Jakub Holy PS: I've found the JBoss EAP in a Cloud Case Study that shows that it is possible to deploy a real-world Java EE application to the EC2 cloud but unfortunately there're no details regarding topology, instance types, or anything :-(

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  • [java] Keystore change passwords

    - by user313724
    Hi, I currently have a keystore, with a particular password that only I should know. I now need to give access to that keystore to someone else, so I would like to either: 1) Change the password, so I can share it with others and let them sign 2) Create a different password and allow them to sign with it. Is this possible? and - if yes - how?

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  • java simple JPanel management (see screenshot)

    - by Allen
    I have a JPanel that encapsulates two JPanels, one on top of the other. The first holds two JLabels which hold the playing cards. The second holds the player's text (name and score). However, when I remove the player's cards, the lower JPanel moves up to the top, which i would prefer that it not do. Is there a way to keep it in place regardless of whether the top JPanel is occupied or not? Thanks

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  • Permutatation algorithm without recursion? Java

    - by Andreas Hornig
    Hi, I would like to get all combination of a number without any repetation. Like 0.1.2, 0.2.1, 1.2.0, 1.0.2, 2.0.1, 2.1.0. I tried to find an easy scheme but couldn't find so I drawed a graph/tree for it and this screams to use recursion. But I would like to do it without, if this is possible. So could anyone please help mw how to do that? Thank you in advance, Andreas

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  • Java Regular Expressions

    - by david robers
    Hi All, Im struggling to understand the regex documentation. How would I find the strings that contain exactly one C in the following text: ABCCAMNL YOOBABCCA XNABCCA ZDXUABCCA TAQABCC ISABCCA REABCCA CABCAMONPT Edit: private void matchIt(String regex, ArrayList<String> d) { Pattern p = Pattern.compile("[\\w^C]"); Matcher m = p.matcher(regex); for (int i = 0; i < d.size(); i++) { p.matcher(d.get(i)); if(m.find()){ out.println(d.get(i)); } } } i have the above function and it only outputs: ABCCAMNL YOOBABCCA Why is that?

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  • Java simple encryption

    - by Ran
    Hello, I would like to encrypt a textual (configuration) file stored on disk. Trying to use DES encryption I've had fatal error on client machines, I later found out caused because the algorithm could not handle accented characters (!) I suspect that was because I was using old packages (sun.misc.BASE64Decoder) - but I'm not sure that is the reason. However, I'm looking for a simpler solution - I need a really simple encryption (I know some people would not agree on that) - not RSA of 128 bit keys or so, just obscuring the text from curious eyes. It is really weird that I could not find on the web a simple trivial solution. Any idea, anyone ? Thanks, Ran

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  • Question about Java File Reader.

    - by Cris Carter
    Hello. I'm having some problems with the FileReader class. How do I specify an offset in the lines it goes through, and how do I tell it when to stop? Let's say I want it to go through each line in a .txt file, but only lines 100-200 and then stop? How would I do this? Right now I'm using ReadLine() but I don't think there's a way to specify offset with that. Any fast help is VERY appreciated. Thanks.

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  • Java IndexOutOfBoundsException

    - by Meko
    Hi all ... I made an little shoot em up game..It works normal but I want also implement if fires intersects they will disappear. I have two list for Player bullets and for computer bullets ...But if I have more bullets from computer or reverse .Here my loop for (int i = 0; i < cb.size(); i++) { for (int j = 0; j < b.size(); j++) { if (b.get(j).rect.intersects(cb.get(i).rect)) { cb.remove(i); b.remove(j); continue; } if (cb.get(i).rect.intersects(b.get(j).rect)) { b.remove(j); cb.remove(i); continue; } } }

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  • http://java.sun.com/j2se/1.4.2/docs/api/org/w3c/dom/Document.html#getDoctype()

    - by Tom Brito
    The Document class have a getDoctype method but doesn't have a setDoctype. The documentation says: The DOM Level 2 does not support editing the Document Type Declaration. docType cannot be altered in any way, including through the use of methods inherited from the Node interface, such as insertNode or removeNode. and in my project I need to generate xml files with my specified doctypes. I've tryied to create my own DefaultNode, but it throws "DOMException: Method not supported" for the setters. Any idea?

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