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  • Java BufferedReader behavior in CSV vs TXT file

    - by Gabriel
    If i try to read a CSV file called csv_file.csv. The problem is that when i read lines with BufferedReader.readLine() it skips the first line with months. But when i rename the file to csv_file.txt it reads it allright and it's not skipping the first line. Is there an undocumented "feature" of BufferedReader that i'm not aware? Example of file: Months, SEP2010, OCT2010, NOV2010 col1, col2, col3, col4, col5 aaa,,sdf,"12,456",bla bla bla, xsaffadfafda and so on, and so on, "10,00", xxx, xxx The code: FileInputStream stream = new FileInputStream(UploadSupport.TEMPORARY_FILES_PATH+fileName); BufferedReader br = new BufferedReader(new InputStreamReader(stream, "UTF-8")); String line = br.readLine(); String months[] = line.split(","); while ((line=br.readLine())!=null) { /*parse other lines*/ }

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  • When can Java produce a NaN (with specific code question)

    - by Brent
    I'm a bit perplexed by some code I'm currently writing. I am trying to preform a specific gradient descent (main loop included below) and depending on the initial conditions I will alternatively get good looking results (perhaps 20% of the time) or everything becomes NaN (the other 80% of the time). However it seems to me that none of the operations in my code could produce NaN's when given honest numbers! My main loop is: // calculate errors delta = m1 + m2 - M; eta = f1 + f2 - F; for (int i = 0; i < numChildren; i++) { epsilon[i] = p[i]*m1+(1-p[i])*m2+q[i]*f1+(1-q[i])*f2-C[i]; } // use errors in gradient descent // set aside differences for the p's and q's float mDiff = m1 - m2; float fDiff = f1 - f2; // first update m's and f's m1 -= rate*delta; m2 -= rate*delta; f1 -= rate*eta; f2 -= rate*eta; for (int i = 0; i < numChildren; i++) { m1 -= rate*epsilon[i]*p[i]; m2 -= rate*epsilon[i]*(1-p[i]); f1 -= rate*epsilon[i]*q[i]; f2 -= rate*epsilon[i]*(1-q[i]); } // now update the p's and q's for (int i = 0; i < numChildren; i++) { p[i] -= rate*epsilon[i]*mDiff; q[i] -= rate*epsilon[i]*fDiff; } This behavior can be seen when we have rate = 0.01; M = 30; F = 30; C = {15, 25, 35, 45}; with the p[i] and q[i] chosen randomly uniformly between 0 and 1, m1 and m2 chosen randomly uniformly to add to M, and f1 and f2 chosen randomly uniformly to add up to F. Does anyone see anything that could create these NaN's?

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  • Parse XML with XPath & namespaces in Java

    - by ripper234
    Can you help me adjust this code so it manages to parse the XML? If I drop the XML namespace it works: String webXmlContent = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" + "<foo xmlns=\"http://foo.bar/boo\"><bar>baz</bar></foo>"; DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance(); domFactory.setNamespaceAware(true); DocumentBuilder builder = domFactory.newDocumentBuilder(); org.w3c.dom.Document doc = builder.parse(new StringInputStream(webXmlContent)); NamespaceContextImpl namespaceContext = new NamespaceContextImpl(); namespaceContext.startPrefixMapping("foo", "http://www.w3.org/2001/XMLSchema-instance"); XPath xpath = XPathFactory.newInstance().newXPath(); xpath.setNamespaceContext(namespaceContext); XPathExpression expr = xpath.compile("/foo/bar"); Object result = expr.evaluate(doc, XPathConstants.NODESET); NodeList nodes = (NodeList) result; System.out.println("Got " + nodes.getLength() + " nodes");

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  • java Swing Listeners: components listening at each others.

    - by Pierre
    Hi all, I want to code two JList (categories and items). When I click one category it should select all the items for that category and when I click on one item it should select its categories. So both JList will have a ListSelectionListener listening at each other and changing the selection. Should I fear about some a of "loop" ? Is there a way to tell that an Event has been consumed ? how do people manage that kind of situation ? Thanks

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  • [Java] Safe way of exposing keySet().

    - by Jake
    This must be a fairly common occurrence where I have a map and wish to thread-safely expose its key set: public MyClass { Map<String,String> map = // ... public final Set<String> keys() { // returns key set } } Now, if my "map" is not thread-safe, this is not safe: public final Set<String> keys() { return map.keySet(); } And neither is: public final Set<String> keys() { return Collections.unmodifiableSet(map.keySet()); } So I need to create a copy, such as: public final Set<String> keys() { return new HashSet(map.keySet()); } However, this doesn't seem safe either because that constructor traverses the elements of the parameter and add()s them. So while this copying is going on, a ConcurrentModificationException can happen. So then: public final Set<String> keys() { synchronized(map) { return new HashSet(map.keySet()); } } seems like the solution. Does this look right?

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  • A very strange problem -> CSS file not detected .Java web application

    - by Nitesh Panchal
    Hello, If i browse my site using http://localhost:8080/abc/Login/index.jsf, everything works fine. But if browse it using simply http://localhost:8080/abc, the page is shown but all its images and css files are missing. What can be the problem? I have this in my web.xml :- <form-login-config> <form-login-page>/Login/index.jsf</form-login-page> <form-error-page>/Login/index.jsf</form-error-page> </form-login-config> Probably, images are not getting referenced correctly. Can anybody help me? I have referenced css file as follows :- <link href="./Css/MainStyleSheet.css" rel="stylesheet" type="text/css" /> where Css is folder in Login

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  • Java 7 API design best practice - return Array or return Collection

    - by Shengjie
    I know this question has be asked before generic comes out. Array does win out a bit given Array enforces the return type, it's more type-safe. But now, with latest JDK 7, every time when I design this type of APIs: public String[] getElements(String type) vs public List<String> getElements(String type) I am always struggling to think of some good reasons to return A Collection over An Array or another way around. What's the best practice when it comes to the case of choosing String[] or List as the API's return type? Or it's courses for horses. I don't have a special case in my mind, I am more looking for a generic pros/cons comparison.

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  • Java Applet - ArrayIndexOutOfBoundsException

    - by Dan
    OK so I am getting an ArrayIndexOutofBoundsException. I don't know why. Here's my code: http://www.so.pastebin.com/y5MjD1k3 The thing is when I go to the red brick at board[2][2]... I go there. Then I go up... then I TRY go to back down but that error pops up. Also when I go to the right 8 squares... I ALSO get that error. ALSO, pretend my 2d map is split into FOUR squares... well square one is the top left... if I go ANYWHERE else ... I get that error. What am I doing wrong? Thanks.

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  • Java URL Connection Time Out

    - by webren
    Hello, I am attempting to connect to a website where I'd like to extract its HTML contents. My application will never connect to the site - only time out. Here is my code: URL url = new URL("www.website.com"); URLConnection connection = url.openConnection(); connection.setConnectTimeout(2000); connection.setReadTimeOut(2000); BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()); String line; while ((line = reader.readLine()) != null) { // do stuff with line } reader.close(); Any ideas would be greatly appreciated. Thanks!

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  • Avoiding duplicate objects in Java deserialization

    - by YGL
    I have two lists (list1 and list2) containing references to some objects, where some of the list entries may point to the same object. Then, for various reasons, I am serializing these lists to two separate files. Finally, when I deserialize the lists, I would like to ensure that I am not re-creating more objects than needed. In other words, it should still be possible for some entry of List1 to point to the same object as some entry in List2. MyObject obj = new MyObject(); List<MyObject> list1 = new ArrayList<MyObject>(); List<MyObject> list2 = new ArrayList<MyObject>(); list1.add(obj); list2.add(obj); // serialize to file1.ser ObjectOutputStream oos = new ObjectOutputStream(...); oos.writeObject(list1); oos.close(); // serialize to file2.ser oos = new ObjectOutputStream(...); oos.writeObject(list2); oos.close(); I think that sections 3.4 and A.2 of the spec say that deserialization strictly results in the creation of new objects, but I'm not sure. If so, some possible solutions might involve: Implementing equals() and hashCode() and checking references manually. Creating a "container class" to hold everything and then serializing the container class. Is there an easy way to ensure that objects are not duplicated upon deserialization? Thanks.

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  • java statistics collection for performance evaluation

    - by user384706
    What is the most efficient way to collect and report performance statistic analysis from an application? If I have an application that uses a series of network apis, and I want to report statistics at runtime, e.g. Method doA() was called 3 times and consumed on avg 500ms Method doB() was called 5 times and consumed on avg 1200ms etc Then, I thought of using a well defined data structure (of collection) that each thread updates per remote call, and this can be used for the report. But I think that it will make the performance worse, for the time spend for statistics collection. Am I correct? How would I procceed if I used a background thread for this, and the other threads that did the remote calls were unaware of this collection gathering? Thanks

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  • Java String.split

    - by user903772
    I have the following text: ARIYALUR:ARIYALUR|CHENNAI:CHENNAI|COIMBATORE:COIMBATORE|CUDDALORE:CUDDALORE|DINDIGUL:DINDIGUL|ERODE:ERODE|KANCHEEPURAM:KANCHEEPURAM|KANYAKUMARI:KANYAKUMARI|KRISHNAGIRI:KRISHNAGIRI|MADURAI:MADURAI|NAMAKKAL:NAMAKKAL|NILGIRIS:NILGIRIS|PERAMBALUR:PERAMBALUR|PONDICHERRY:PONDICHERRY|SALEM:SALEM|THANJAVUR:THANJAVUR|THENI:THENI|THIRUVALLUR:THIRUVALLUR|THOOTHUKUDI:THOOTHUKUDI|TIRUNELVELI:TIRUNELVELI|VELLORE:VELLORE|VILLUPURAM:VILLUPURAM|VIRUDHUNAGAR:VIRUDHUNAGAR| I tried to do a split("|") but my array is made up of alphabets and not each district. Please help.

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  • Generate a collection of changed lines between two revisions of a file using Java

    - by mchr
    I am writing an eclipse plugin which needs to be able to determine which lines of a file have changed compared to a different version of the same file. Is there an existing class or library which I can use for this task? The closest I have found is org.eclipse.compare.internal.merge.DocumentMerger. This can be used to find the information I need but is in an internal package so is not suitable for me to use. I could copy/paste the source of this class and adapt it to my requirements. However, I am hoping there is an existing library to handle textual comparisons.

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  • Best Java library(ies) for forgiving command interpreter

    - by vkraemer
    I am looking for a library or set of libraries that will help me write a forgiving command interpreter. A forgiving command interpreter would be a command interpreter which can deal with simple and even not so simple spelling and word order mistakes in the input. My goal is to have an interpreter which would take the input (a command) from a user and then: execute the command, if it is correct. apply corrections to the command, until a correct command is generated and then present that command to the user to confirm whether it is 'what the user meant'.

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  • Fetching JSON object from Servlet Java

    - by ChrisA
    I want to create an application that will fetch a JSON object from a servlet to deserialize it, and then use its variables to do other things. My servlet has the following code in the doPost: protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ObjectOutputStream os; os = new ObjectOutputStream(response.getOutputStream()); String s = new String("A String"); Gson gson = new Gson(); String gsonObject= gson.toJson(s); os.writeObject(gsonObject); os.close(); } Now, while the servlet is running, I can access it via a browser, if I post same code in the doGet method, that would download a servlet file, which is not what I want. What should I use in my second application that would connect to the servlet, fetch the object, so that I can manipulate it later? Thanks in advance.

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  • What is the use of reflection in Java/C# etc

    - by zengr
    I was just curious, why should we use reflection in the first place? // Without reflection Foo foo = new Foo(); foo.hello(); // With reflection Class cls = Class.forName("Foo"); Object foo = cls.newInstance(); Method method = cls.getMethod("hello", null); method.invoke(foo, null); We can simply create an object and call the class's method, but why do the same using forName, newInstance and getMthod functions? To make everything dynamic?

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  • Java Object Creation Error

    - by ikurtz
    package Sartre.Connect4; import javax.swing.*; public class ChatGUI extends JDialog { public ChatGUI(){ setTitle("Chat"); } } when i do this in another class in the same package: ChatGUI chatGUI = new ChatGUI(); i end up with a situation: Cannot Find Symbol please help?

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  • Java, let CookieHandler work on only one instance.

    - by user435657
    Hi all, I don't know how CookieHandler works system wide, I did view the source of CookieHandler but found no more information except the get/set methods. Where do TCP/HTTP connections use instance of CookieHandler, which I set by CookieHandler.setDefault(...) Which source file I should refer to? URLConnection & HttpURLConnection don't seem have things to do with it. Help, thanks in advance.

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  • Regex to match pattern with subdomain in java gives issues

    - by Ramesh
    I am trying to match the sub domain of an url using http://([a-z0-9]*.)?example.com/.* which works perfectly for these cases. http://example.com/index.html http://test.example.com/index.html http://test1.example.com/index.html http://www.example.com/122/index.html But the problem is it matches for this URL too. http://www.test.com/?q=http://example.com/index.html if an URL with another domain has the URL in path it matches.Can any one tell me how to match for current domain only. getting the host will work but i need to match full URL.

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  • Java convert time format to integer or long

    - by behrk2
    Hello, I'm wondering what the best method is to convert a time string in the format of 00:00:00 to an integer or a long? My ultimate goal is to be able to convert a bunch of string times to integers/longs, add them to an array, and find the most recent time in the array... I'd appreciate any help, thanks! Ok, based on the answers, I have decided to go ahead and compare the strings directly. However, I am having some trouble. It is possible to have more than one "most recent" time, that is, if two times are equal. If that is the case, I want to add the index of both of those times to an ArrayList. Here is my current code: days[0] = "15:00:00"; days[1] = "17:00:00"; days[2] = "18:00:00"; days[3] = "19:00:00"; days[4] = "19:00:00"; days[5] = "15:00:00"; days[6] = "13:00:00"; ArrayList<Integer> indexes = new ArrayList<Integer>(); String curMax = days[0]; for (int x = 1; x < days.length1; x++) { if (days[x].compareTo(curMax) > 0) { curMax = days[x]; indexes.add(x); System.out.println("INDEX OF THE LARGEST VALUE: " + x); } } However, this is adding index 1, 2, and 3 to the ArrayList... Can anyone help me?

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  • Programming error in Java Socket

    - by Akhil K Nambiar
    Can you tell me what is the error in this code? Socket socket = new Socket(hostname, port); PrintWriter out = new PrintWriter(socket.getOutputStream(), true); //DataInputStream is = new DataInputStream(socket.getInputStream()); out.println("hi"); System.out.print(in.readLine()); The Server Socket program is written in .Net and it echoes back the data. The data is sent successfully but could not be retrieved properly. I tried the same by using the linux command nc 192.168.1.6 8425 (enter) Hi (Sent data) Hi (recieved data) When I checked the code the data is found to have sent as byteStream in .Net. Is that a problem. In that case what modification should I make.

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