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  • Returning the element number of the longest string in an array

    - by JohnRoberts
    I'm trying to get the longestS method to take the user-inputted array of strings, then return the element number of the longest string in that array. I got it to the point where I was able to return the number of chars in the longest string, but I don't believe that will work for what I need. My problem is that I keep getting incompatible type errors when trying to figure this out. I don't understand the whole data type thing with strings yet. It's confusing me how I go about return a number of the array yet the array is of strings. The main method is fine, I got stuck on the ???? part. { public static void main(String [] args) { Scanner inp = new Scanner( System.in ); String [] responseArr= new String[4]; for (int i=0; i<4; i++) { System.out.println("Enter string "+(i+1)); responseArr[i] = inp.nextLine(); } int highest=longestS(responseArr); } public static int longestS(String[] values) { int largest=0 for( int i = 1; i < values.length; i++ ) { if ( ????? ) } return largest; } }

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  • How can I make a family of singletons?

    - by Jay
    I want to create a set of classes that share a lot of common behavior. Of course in OOP when you think that you automatically think "abstract class with subclasses". But among the things I want these classes to do is to each have a static list of instances of the class. The list should function as sort of a singleton within the class. I mean each of the sub-classes has a singleton, not that they share one. "Singleton" to that subclass, not a true singleton. But if it's a static, how can I inherit it? Of course code like this won't work: public abstract A { static List<A> myList; public static List getList() { if (myList==null) myList=new ArrayList<A>(10); return myList; } public static A getSomethingFromList() { List listInstance=getList(); ... do stuff with list ... } public int getSomethingFromA() { ... regular code acting against current instance ... } } public class A1 extends A { ... } public class A2 extends A { ... } A1 somethingfromA1List=(A1) A1.getSomethingFromList(); A2 somethingfromA2List=(A2) A2.getSomethingFromList(); The contents of the list for each subclass would be different, but all the code to work on the lists would be the same. The problem with the above code is that I'd only have one list for all the subclasses, and I want one for each. Yes, I could replicate the code to declare the static list in each of the subclasses, but then I'd also have to replicate all the code that adds to the lists and searches the list, etc, which rather defeats the purpose of subclassing. Any ideas on how to do this without replicating code?

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  • What to do when ServerSocket throws IOException and keeping server running

    - by s5804
    Basically I want to create a rock solid server. while (keepRunning.get()) { try { Socket clientSocket = serverSocket.accept(); ... spawn a new thread to handle the client ... } catch (IOException e) { e.printStackTrace(); // NOW WHAT? } } In the IOException block, what to do? Is the Server socket at fault so it need to be recreated? For example wait a few seconds and then serverSocket = ServerSocketFactory.getDefault().createServerSocket(MY_PORT); However if the server socket is still OK, then it is a pity to close it and kill all previously accepted connections that are still communicating. EDIT: After some answers, here my attempt to deal with the IOException. Would the implementation be guaranteeing keeping the server up and only re-create server socket when only necessary? while (keepRunning.get()) { try { Socket clientSocket = serverSocket.accept(); ... spawn a new thread to handle the client ... bindExceptionCounter = 0; } catch (IOException e) { e.printStackTrace(); recreateServerSocket(); } } private void recreateServerSocket() { while (keepRunning) { try { logger.info("Try to re-create Server Socket"); ServerSocket socket = ServerSocketFactory.getDefault().createServerSocket(RateTableServer.RATE_EVENT_SERVER_PORT); // No exception thrown, then use the new socket. serverSocket = socket; break; } catch (BindException e) { logger.info("BindException indicates that the server socket is still good.", e); bindExceptionCounter++; if (bindExceptionCounter < 5) { break; } } catch (IOException e) { logger.warn("Problem to re-create Server Socket", e); e.printStackTrace(); try { Thread.sleep(30000); } catch (InterruptedException ie) { logger.warn(ie); } } } }

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  • JTextPane insert component, faulty vertical alignment

    - by John O
    I have a JTextPane, into which I need to insert a JComponent. I'm using JTextPane.insertComponent(Component). The item is indeed inserted, but the vertical positioning is too high. Instead of having the bottom of the component aligned with the baseline of the current line of text, the component is way above that position, blocking out/over-painting lines of text appearing above. I have tried calling setAlignmentY(float) with various values, on both the inserted component and the JTextPane, but it doesn't affect the behavior at all. My guess: there seems to be some state inside my JTextPane or its Document that I need to be changing. But I don't know what it is. John

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  • Is it possible to prevent out-of-order execution by using single volatile

    - by Yan Cheng CHEOK
    By referring article, it is using a pair of volatile to prevent out-of-order execution. I was wondering, is it possible to prevent it using single volatile? void fun_by_thread_1() { this.isNuclearFactory = true; this.factory = new NuclearFactory(); } void fun_by_thread_2() { Factory _factory = this.factory; if (this.isNuclearFactory) { // Do not operate nuclear factory!!! return; } // If out-of-order execution happens, _factory might // be NuclearFactory instance. _factory.operate(); } Factory factory = new FoodFactory(); volatile boolean isNuclearFactory = false; The reason I ask, is because I have a single guard flag (similar to isNuclearFactory flag), to guard against multiple variables (similar to many Factory). I do not wish to mark all the Factory as volatile. Or, shall I fall into the following solution? void fun_by_thread_1() { try { writer.lock(); this.isNuclearFactory = true; this.factory = new NuclearFactory(); } finally { writer.unlock(); } } void fun_by_thread_2() { try { reader.lock(); Factory _factory = this.factory; if (this.isNuclearFactory) { // Do not operate nuclear factory!!! return; } } finally { reader.unlock(); } _factory.operate(); } Factory factory = new FoodFactory(); boolean isNuclearFactory = false; P/S: I know instanceof. Factory is just an example to demonstrate of out-of-order problem.

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  • Workaround for richfaces combobox hotkey bug

    - by John
    Hi, Does anyone know a workaround for the bug https://jira.jboss.org/jira/browse/RF-8076 ? Just to clarify things, we have a form with multiple inputs, one of them being a combobox with auto complete features. We've setup a hotkey via <rich:hotKey key="return" ... /> It works great everywhere except in the combobox, and I would really like to get it working on the combobox as well. The behaviour I want when the ENTER key is pressed inside the combobox is: If the combobox context was modified by auto complete then do nothing Else action the event on ENTER key pressed We're running on seam/richfaces. I'm open to any workaround, but simplicity is much sought for. Thanks!

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  • Netbeans Clamshell emulator out of memory

    - by Kyle
    Hello, I have been working with the clamshell mobile phone emulator for netbeans. I recently have tested a simple bluetooth application and got an Out of Memory erorr. Is it possible to up the amount of memory the emulator can use? thanks!

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  • Resized image degrades in quality.

    - by Venkats
    I resized an image using Java2D Graphics class. But it doesn't look right. BufferedImage resizedImage = new BufferedImage(IMG_WIDTH, IMG_HEIGHT, type); Graphics2D g = resizedImage.createGraphics(); g.drawImage(originalImage, 0, 0, IMG_WIDTH, IMG_HEIGHT, null); g.dispose(); Is it possible to scale an image without introducing artifacts?

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  • String operations

    - by NEO
    I am trying to find the most repeated word in a string. My code is as follows: public class Word { private String toWord; private int Count; public Word(int count, String word){ toWord = word; Count = count; } public static void main(String args[]){ String str="my name is neo and my other name is also neo because I am neo"; String []str1=str.split(" "); Word w1=new Word(0,str1[0]); LinkedList<Word> list = new LinkedList<Word>(); list.add(w1); ListIterator itr = list.listIterator(); for(int i=1;i<str1.length;i++){ while(itr.hasNext()){ if(str1[i].equalsTO(????)); else list.add(new Word(0,str1[i])); } How do I compare the string from string array str1 to the string stored in the linked list and then how do i increase the respective count. I will then print the string with the highest count, I dont know how to do that either.

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  • Log4j - Logging to multiple log files based on the project modules

    - by Veera
    Consider this scenario: I have a project with two modules and one common module as below (the package structure): com.mysite.moduleone com.mysite.moduletwo com.mysite.commonmodule In the above, the commonmodule classes can be used by other two modules. The question: I need to configureLog4J such a way that the log messages from moduleone and moduletwo goes to different log file. I can always do this using using category. But the real problem is when I want to log the messages from the commonmodule also. So, when the commonmodule classes are called from moduleone the commonmodule log messages should go to the moduleone log file. If the commonmodule is accesse from moduletwo the commonmodule log messages should go to moduletwo log file. Is it possible to configure Log4J in this fashion? Any comments? PS: I think I made my question clear. If any confusion, leave a comment, wil try to clear it. :)

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  • Getting the instance when Constructor#newInstance throws?

    - by Shtééf
    I'm working on a simple plugin system, where third party plugins implement a Plugin interface. A directory of JARs is scanned, and the implementing classes are instantiated with Constructor#newInstance. The thing is, these plugins call back into register* methods of the plugin host. These registrations use the Plugin instance as a handle. My problem is how to clean up these registrations if the constructor decides to fail and throw halfway through. InvocationTargetException doesn't seem to have anything on it to get the instance. Is there a way to get at the instance of an exception throwing constructor? P.S.: It's typically strongly advised to users that the constructor not do anything, but in practice people are doing it any ways.

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  • Are there any examples/tutorials of using Spring 3.0 with Cassandra as a backend?

    - by zeroDivisible
    Hello, As I had written in title, I am trying to learn Spring 3.0 (I already know Django, Pylons and few simpler MVC frameworks) and try to use Cassandra as a backend for my web application. Are there any real world examples of doing this? Or maybe some tutorials? I know about the existence of documentation of both technologies, yet I am looking for something "faster" to read and get me rolling.

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  • Design Pattern for Server Emulator

    - by adisembiring
    I wanna build server socket emulator, but I want implement some design pattern there. I will described my case study that I have simplified like these: My Server Socket will always listen client socket. While some request message come from the client socket, the server emulator will response the client through the socket. the response is response code. '00' will describe request message processed successfully, and another response code expect '00' will describe there are some error while processing the message request. IN the server there are some UI, this UI contain check response parameter such as. response code timeout interval While the server want to response the client message, the response code taken from input parameter response form UI check the timeout interval, it will create sleep thread and the interval taken from timeout interval input from UI. I have implement the function, but I create it in one class. I feel it so sucks. Can you suggest me what class / interface that I must create to refactor my code.

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  • how to handle result set data

    - by ashwani66476
    Hello All I am getting lacks of records in my Result Set. My concerns are : How Result Set handle these records internally? and How a programmer can handle those records in batches So that memory problem would not occur.? waiting for your answers .. Many Thanks

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  • Running server-program from a .jar file

    - by skiwi
    I have created and am working on a server-application that monitors for specific folders and takes appropriate actions whenever files are being added. Now I come to the point where I want to be able to shutdown the program, for example for applying a patch. The server runs simply in a command prompt, how can I signal that I want to perform maintenance on it? I do not think reading System.In is feasible as I am also outputting text in the prompt. Regards.

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  • sorting a doubly linked list with merge sort.

    - by user329820
    Hi I have found this code in the internet and it was for arrays ,I want to change it for doubly linked list(instead of index we should use pointer) would you please help me that how can i change merge method(I have changed sort method by myself) also this is not my home work ,I love working with linked list!! public class MergeSort { private DoublyLinkedList LocalDoublyLinkedList; public MergeSort(DoublyLinkedList list) { LocalDoublyLinkedList = list; } public void sort() { if (LocalDoublyLinkedList.size() <= 1) { return; } DoublyLinkedList listOne = new DoublyLinkedList(); DoublyLinkedList listTwo = new DoublyLinkedList(); for (int x = 0; x < (LocalDoublyLinkedList.size() / 2); x++) { listOne.add(x, LocalDoublyLinkedList.getValue(x)); } for (int x = (LocalDoublyLinkedList.size() / 2) + 1; x < LocalDoublyLinkedList.size`(); x++) {` listTwo.add(x, LocalDoublyLinkedList.getValue(x)); } //Split the DoublyLinkedList again MergeSort sort1 = new MergeSort(listOne); MergeSort sort2 = new MergeSort(listTwo); sort1.sort(); sort2.sort(); merge(listOne, listTwo); } private void merge(DoublyLinkedList a, DoublyLinkedList b) { int x = 0; int y = 0; int z = 0; while (x < first.length && y < second.length) { if (first[x] < second[y]) { a[z] = first[x]; x++; } else { a[z] = second[y]; y++; } z++; } //copy remaining elements to the tail of a[]; for (int i = x; i < first.length; i++) { a[z] = first[i]; z++; } for (int i = y; i < second.length; i++) { a[z] = second[i]; z++; } } }

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  • Remove Empty Attributes from XML

    - by er4z0r
    Hi, I have a buggy xml that contains empty attributes and I have a parser that coughs on empty attributes. I have no control over the generation of the xml nor over the parser that coughs on empty attrs. So what I want to do is a pre-processing step that simply removes all empty attributes. I have managed to find the empty attribus, but now I don't know how to remove them: XPathFactory xpf = XPathFactory.newInstance(); XPath xpath = xpf.newXPath(); XPathExpression expr = xpath.compile("//@*"); Object result = expr.evaluate(d, XPathConstants.NODESET); if (result != null) { NodeList nodes = (NodeList) result; for(int node=0;node<nodes.getLength();node++) { Node n = nodes.item(node); if(isEmpty(n.getTextContent())) { this.log.warn("Found empty attribute declaration "+n.toString()); NamedNodeMap parentAttrs = n.getParentNode().getAttributes(); parentAttrs.removeNamedItem(n.getNodeName()); } } } This code gives me a NPE when accessing n.getParentNode().getAttributes(). But how can I remove the empty attribute from an element, when I cannot access the element?

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  • Occasional weird Glassfish errors, resolved by a restart?

    - by Pooria
    I'm developing a web app using netbeans with GlassFishv3. Every once in a while when I add a new feature in my app, glassfish starts nagging with stupid errors, after a lot of time wasting and panicking, i restart glassfish and run my application again, then suddenly the errors all go away and my site starts acting correctly. (or in case I have made a real mistake, i receive a reasonable & descriptive error from GF.) [Edit: the rest of the question was revealed to have been my own mistake.] But the problems don't end there. Recently, i added the ability to write comments in a (JSF) page, after the user submits their comment, i add it to the database and redirect to the same page, so that hopefully the page refreshes with the new comment, but it wont! The underlying Mysql database shows that the new comment has been added, but the page just wont show the new comment! I've tried everything (e.g. deleting browser cache, using different browsers) but only after restarting GF is when the page shows the new comment! Do you have any idea what the problem could be? Could this be a Glassfish bug? What i am using: JSF2, EJB3.1, JPA, MySql

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  • JavaME - LWUIT images eat up all the memory

    - by Marko
    Hi, I'm writing a MIDlet using LWUIT and images seem to eat up incredible amounts of memory. All the images I use are PNGs and are packed inside the JAR file. I load them using the standard Image.createImage(URL) method. The application has a number of forms and each has a couple of labels an buttons, however I am fairly certain that only the active form is kept in memory (I know it isn't very trustworthy, but Runtime.freeMemory() seems to confirm this). The application has worked well in 240x320 resolution, but moving it to 480x640 and using appropriately larger images for UI started causing out of memory errors to show up. What the application does, among other things, is download remote images. The application seems to work fine until it gets to this point. After downloading a couple of PNGs and returning to the main menu, the out of memory error is encountered. Naturally, I looked into the amount of memory the main menu uses and it was pretty shocking. It's just two labels with images and four buttons. Each button has three images used for style.setIcon, setPressedIcon and setRolloverIcon. Images range in size from 15 to 25KB but removing two of the three images used for every button (so 8 images in total), Runtime.freeMemory() showed a stunning 1MB decrease in memory usage. The way I see it, I either have a whole lot of memory leaks (which I don't think I do, but memory leaks aren't exactly known to be easily tracked down), I am doing something terribly wrong with image handling or there's really no problem involved and I just need to scale down. If anyone has any insight to offer, I would greatly appreciate it.

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  • Anyone know exactly which JMS messages will be redelivered in CLIENT_ACKNOWLEDGE mode if the client

    - by user360612
    The spec says "Acknowledging a consumed message automatically acknowledges the receipt of all messages that have been delivered by its session" - but what I need to know is what it means by 'delivered'. For example, if I call consumer.receive() 6 times, and then call .acknowledge on the 3rd message - is it (a) just the first 3 messages that are ack'd, or (b) all 6? I'm really hoping it's option a, i.e. messages after the one you called acknowledge on WILL be redelivered, otherwise it's hard to see how you could prevent message lost in the event of my receiver process crashing before I've had a chance to persist and acknowledge the messages. But the spec is worded such that it's not clear. I get the impression the authors of the JMS spec considered broker failure, but didn't spend too long thinking about how to protect against client failure :o( Anyway, I've been able to test with SonicMQ and found that it implements (a), i.e. messages 'received' later than the message you call .ack on DO get redelivered in the event of a crash, but I'd love to know how other people read the standard, and if anyone knows how any other providers have implemented CLIENT_ACKNOWLEDGE? (i.e. what the 'de facto' standard is) Thanks Ben

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  • HTTP status 405 - HTTP method POST is not supported by this URL

    - by Wont Say
    I am getting this "HTTP method POST is not supported by this URL" error when I run my project. The funny thing is, it was running perfectly fine two days ago. After I made a few changes to my code but then restored my original code and its giving me this error. Could you please help me? Here is my index.html: <form method="post" action="login.do"> <div> <table> <tr><td>Username: </td><td><input type="text" name="e_name"/> </td> </tr> <tr><td> Password: </td><td><input type="password" name="e_pass"/> </td> </tr> <tr><td></td><td><input type="submit" name ="e_submit" value="Submit"/> Here is my Login servlet: public class Login extends HttpServlet { /** * Processes requests for both HTTP * <code>GET</code> and * <code>POST</code> methods. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException, SQLException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); try { /* * TODO output your page here. You may use following sample code. */ int status; String submit = request.getParameter("e_submit"); String submit2 = request.getParameter("a_submit"); out.println("Here1"); String e_name = request.getParameter("e_name"); String e_password = request.getParameter("e_pass"); String a_name = request.getParameter("a_name"); String a_password = request.getParameter("a_pass"); out.println(e_name+e_password+a_name+a_password); Author author = new Author(a_name,a_password); Editor editor = new Editor(e_name,e_password); // If it is an AUTHOR login: if(submit==null){ status = author.login(author); out.println("Author Login"); //Incorrect login details if(status==0) { out.println("Incorrect"); RequestDispatcher view = request.getRequestDispatcher("index_F.html"); view.forward(request, response); } //Correct login details --- AUTHOR else { out.println("Correct login details"); HttpSession session = request.getSession(); session.setAttribute(a_name, "a_name"); RequestDispatcher view = request.getRequestDispatcher("index_S.jsp"); view.forward(request, response); } } //If it is an EDITOR login else if (submit2==null){ status = editor.login(editor); //Incorrect login details if(status==0) { RequestDispatcher view = request.getRequestDispatcher("index_F.html"); view.forward(request, response); } //Correct login details --- EDITOR else { out.println("correct"); HttpSession session = request.getSession(); session.setAttribute(e_name, "e_name"); session.setAttribute(e_password, "e_pass"); RequestDispatcher view = request.getRequestDispatcher("index_S_1.html"); view.forward(request, response); } } out.println("</body>"); out.println("</html>"); } finally { out.close(); } } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { super.doPost(req, resp); } @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { super.doGet(req, resp); }} And my web.xml looks like this: <?xml version="1.0" encoding="UTF-8"?> <servlet> <servlet-name>action</servlet-name> <servlet-class>org.apache.struts.action.ActionServlet</servlet-class> <init-param> <param-name>config</param-name> <param-value>/WEB-INF/struts-config.xml</param-value> </init-param> <init-param> <param-name>debug</param-name> <param-value>2</param-value> </init-param> <init-param> <param-name>detail</param-name> <param-value>2</param-value> </init-param> <load-on-startup>2</load-on-startup> </servlet> <servlet> <servlet-name>Login</servlet-name> <servlet-class>controller.Login</servlet-class> </servlet> <servlet-mapping> <servlet-name>action</servlet-name> <url-pattern>*.do</url-pattern> </servlet-mapping> <servlet-mapping> <servlet-name>Login</servlet-name> <url-pattern>/login.do</url-pattern> </servlet-mapping> <session-config> <session-timeout> 30 </session-timeout> </session-config> <welcome-file-list> <welcome-file>index.html</welcome-file> </welcome-file-list> I use Glassfish v3 server - let me know anything else you need to know

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