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  • Conceptual inheritance implementation

    - by TheSENDER
    Hi there, I'm writing a spatial data structure and I have a doubt about what's the best NODE implementation. According to my design I have an abstract node entity and three classes which inherit from it: EMPTYNODE, FULLNODE, INTERNALNODE. The first one has no particular data. The second one has 1 reference to a generic element. The third one has 2 references to other nodes. I have found several ways to implement this situation (that I have already coded) but I can't decide what's the best. The first solution that I have found is to use a single class Node that potentially performs all the operation in this way: private static class Node { private Elem elem = null; private Node left = null, right = null; public Elem getElem() { assert isFull(); return elem; } public boolean isEmpty() { return elem == null && left == null; } public boolean isFull() { return elem != null; } public boolean isInternal() { return elem == null && left != null; } } The second solution is to write an explicit division by classes where every class offers only its methods. Obviously in this way we are obliged to perform several casts to the node objects. private static abstract class Node { public abstract boolean isEmpty(); public abstract boolean isFull(); public abstract boolean isInternal(); } private static class FullNode extends Node{ private ITriangle elem; @Override public boolean isEmpty() { return false; } @Override public final boolean isFull() { return true; } @Override public final boolean isInternal() { return false; } public Elem getElem() { return elem; } } The third one solution is to use the inheritance allowing every classes to offer all the methods, but the object type should by check by "isEmpty()" and similar methods. In case of wrong call we'll throw an exception. private static abstract class Node { public abstract boolean isEmpty(); public abstract boolean isFull(); public abstract boolean isInternal(); public abstract Elem getElem(); } private static class Empty extends Node{ @Override public boolean isEmpty() { return true; } @Override public final boolean isFull() { return false; } @Override public final boolean isInternal() { return false; } @Override public Elem getElem() { throw new AssertionError(); } } What do you think about these three solutions? Which one would you use? Any other ideas? Thanks for your help. Every idea will be appreciated.

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  • when get pagecontent from URL the connect alway return nopermistion ?

    - by tiendv
    I have a methor to return pagecontent of link but when it run, alway return "Do not perrmisson ", plesea check it here is code to return string pagecontent public static String getPageContent(String targetURL) throws Exception { Hashtable contentHash = new Hashtable(); URL url; URLConnection conn; // The data streams used to read from and write to the URL connection. DataOutputStream out; DataInputStream in; // String returned as the result . String returnString = ""; // Create the URL object and make a connection to it. url = new URL(targetURL); conn = url.openConnection(); // check out permission of acess URL if (conn.getPermission() != null) { returnString = "Do not Permission access URL "; } else { // Set connection parameters. We need to perform input and output, // so set both as true. conn.setDoInput(true); conn.setDoOutput(true); // Disable use of caches. conn.setUseCaches(false); // Set the content type we are POSTing. We impersonate it as // encoded form data conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); // get the output stream . out = new DataOutputStream(conn.getOutputStream()); String content = ""; // Create a single String value pairs for all the keys // in the Hashtable passed to us. Enumeration e = contentHash.keys(); boolean first = true; while (e.hasMoreElements()) { // For each key and value pair in the hashtable Object key = e.nextElement(); Object value = contentHash.get(key); // If this is not the first key-value pair in the hashtable, // concantenate an "&" sign to the constructed String if (!first) content += "&"; // append to a single string. Encode the value portion content += (String) key + "=" + URLEncoder.encode((String) value); first = false; } // Write out the bytes of the content string to the stream. out.writeBytes(content); out.flush(); out.close(); // check if can't read from URL // Read input from the input stream. in = new DataInputStream(conn.getInputStream()); String str; while (null != ((str = in.readLine()))) { returnString += str + "\n"; } in.close(); } // return the string that was read. return returnString; }

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  • "Detecting" and loading of "plugins" in GAE

    - by Patrick Cornelissen
    Hi! I have a "plugin like" architecture and I want to create one instance of each class that implements a dedicated interface and put these in a cache. (To have a singleton-ish effect). The plugins will be provided as jars and put into the app engine war file before the app is uploaded. I have tried to use the ClassPathScanningCandidateComponentProvider as I'm using spring anyway, but this didn't work. The provider complained that it was not able to find the HttpServletResponse class file while scanning the classpath. I can't get around this, when I add the servlet jar, then I'll get of course problems, because the same jar is also provided by the GAE. If I don't, I'm getting the error above... So I tried to add a static initialization code, but of course this doesn't work, because the class is initialized when it's instantiated for the first time. (Well I knew that but it was worth a try) The last chance I currently see is that I create a properties file with all plugin classes when the package is created, but this requires writing of a maven plugin etc. and I'd like to avoid that. Is there something that I am missing?

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  • converting result set to list

    - by akshay
    how can i conver result set to list? i am using following code but its not working properly private List<User> convertToList(ResultSet rs) { List<User> userList = new ArrayList(); User user = new User(); try { while (rs.next()) { user.setId(rs.getInt("id")); user.setUsername(rs.getString("username")); user.setFname(rs.getString("fname")); user.setLname(rs.getString("lname")); user.setUsertype(rs.getInt("usertype")); user.setPasswd(rs.getString("passwd")); user.setEmail(rs.getString("email")); userList.add(user); } } catch (SQLException ex) { Logger.getLogger(UserDAO.class.getName()).log(Level.SEVERE, null, ex); } finally { closeConnection(); } return userList; }

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  • Google Maps Controls panel size is displayed wrong

    - by Andrea Giachetto
    I have a weird problem with Google Maps Control. I've tested in a blank page my custom maps with custom markers and everything seems to be ok, also with the control panel. When I tried to import all my code in the page I'm working with ( I use a full screen fluid grid system ) the control panel is displayed with strange size. I tried everything for disable/enable the ui of the Google Maps but the problem remain. The code of my maps are exactly the same, both in my blank page and in my site, but in the site the ui control panel is displayed very strange. Here's the code: <div id="map_canvas2" style="height: 580px; width: 100%;"></div> <script> var image = 'path/to/your/image.png'; var mapOptions = { zoom: 17, center: new google.maps.LatLng(45.499290, 12.621510), mapTypeId: google.maps.MapTypeId.ROADMAP, scrollwheel: false } var map = new google.maps.Map(document.getElementById('map_canvas2'), mapOptions); var myPos = new google.maps.LatLng(45.499290,12.621510); var myMarker = new google.maps.Marker({position: myPos, map: map, icon: 'http://www.factory42.it/jtaca/wordpress/wp-content/uploads/2014/06/pin-map.png' }); </script> </div> Here's an img: http://www.factory42.it/jtaca/wordpress/wp-content/uploads/2014/06/img-maps.png

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  • Can fields of the class and arguments of the method interfere?

    - by Roman
    I have a class with a fields called "a". In the class I have a method and in the list of arguments of this method I also have "a". So, which "a" I will see inside of the method? Will it be the field or it will be the argument of the method? public class myClass { private String a; // Method which sets the value of the field "a". public void setA(String a) { a = a; } } By the way, there is a similar situation. A method has some local (for method) variables whose names coincide with the names of the fields. What will the "see" the method if I refer to such a method-local variable inside the method (the field or the local variable)?

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  • Batch processing JDBC

    - by Wai Hein
    I am practicing JDBC batch processing and having errors: error 1: Unsupported feature error 2: Execute cannot be empty or null Property files include: itemsdao.updateBookName = Update Books set bookname = ? where books.id = ? itemsdao.updateAuthorName = Update books set authorname = ? where books.id = ? I know I can execute about DML statements in one update, but I am practicing batch processing in JDBC. Below is my method public void update(Item item) { String query = null; try { connection = DbConnector.getConnection(); property = SqlPropertiesLoader.getProperties("dml.properties"); connection.setAutoCommit(false); if ( property == null ) { Logging.log.debug("dml.properties does not exist. Check property loader or file name is spelled right"); return; } query = property.getProperty("itemsdao.updateBookName"); statement = connection.prepareStatement(query); statement.setString(1, item.getBookName()); statement.setInt(2, item.getId()); statement.addBatch(query); query = property.getProperty("itemsdao.updateAuthorName"); statement = connection.prepareStatement(query); statement.setString(1, item.getAuthorName()); statement.setInt(2, item.getId()); statement.addBatch(query); statement.executeBatch(); connection.commit(); }catch (ClassNotFoundException e) { Logging.log.error("Connection class does not exist", e); } catch (SQLException e) { Logging.log.error("Violating PK constraint",e); } //helper class th finally { DbUtil.close(connection); DbUtil.closePreparedStatement(statement); }

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  • How to represent a Many-To-Many relationship in XML or other simple file format?

    - by CSharperWithJava
    I have a list management appliaction that stores its data in a many-to-many relationship database. I.E. A note can be in any number of lists, and a list can have any number of notes. I also can export this data to and XML file and import it in another instance of my app for sharing lists between users. However, this is based on a legacy system where the list to note relationship was one-to-many (ideal for XML). Now a note that is in multiple lists is esentially split into two identical rows in the DB and all relation between them is lost. Question: How can I represent this many-to-many relationship in a simple, standard file format? (Preferably XML to maintain backwards compatibility)

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  • @ManyToMany Duplicate Entry Exception

    - by zp26
    I have mapped a bidirectional many-to-many exception between the entities Course and Trainee in the following manner: Course { ... private Collection<Trainee> students; ... @ManyToMany(targetEntity = lesson.domain.Trainee.class, cascade = {CascadeType.All}, fetch = {FetchType.EAGER}) @Jointable(name="COURSE_TRAINEE", joincolumns = @JoinColumn(name="COURSE_ID"), inverseJoinColumns = @JoinColumn(name = "TRAINEE_ID")) @CollectionOfElements public Collection<Trainee> getStudents() { return students; } ... } Trainee { ... private Collection<Course> authCourses; ... @ManyToMany(cascade = {CascadeType.All}, fetch = {FetchType.EAGER}, mappedBy = "students", targetEntity = lesson.domain.Course.class) @CollectionOfElements public Collection<Course> getAuthCourses() { return authCourses; } ... } Instead of creating a table where the Primary Key is made of the two foreign keys (imported from the table of the related two entities), the system generates the table "COURSE_TRAINEE" with the following schema: I am working on MySQL 5.1 and my App. Server is JBoss 5.1. Does anyone guess why?

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  • How can I get a project type on Netbeans Platform?

    - by Fabio
    Hi folks, Is there a way to know the type of a selected project? I would like to do some specific actions depending of the project type like a J2SE project. Below is the only way that I found to do that: public final class MyAction extends CookieAction { @Override public boolean isEnabled() { if(this.getActivatedNodes() == null || this.getActivatedNodes().length != 1) { return false; } Lookup lookup = this.getActivatedNodes()[0].getLookup(); // gets the selected project Project currentProject = lookup.lookup(Project.class); // checks if the selected project is a J2SE Project or a Maven Project if(currentProject != null && (currentProject.getClass().getSimpleName().equals("J2SEProject") || currentProject.getClass().getSimpleName().equals("NbMavenProjectImpl"))) { return true; } return false; }}

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  • Add Method to Built In Class

    - by Evorlor
    I am pretty sure this is not doable, but I will go ahead and cross my fingers and ask. I am trying to add a method to a built in class. I want this method to be callable by all of the built in class's subclasses. Specifically: I have a JButton, a JTextPane, and other JComponents. I want to be able to pass in a JDom Element instead of a Rectangle to setBounds(). My current solution is to extend each JComponent subclass with the desired methods, but that is a LOT of duplicate code. Is there a way I can write the following method just one time, and have it callable on all JComponent objects? Or is it required that I extend each subclass individually, and copy and paste the method below? public void setBounds(Element element) { this.setBounds(Integer.parseInt(element.getAttribute( "x").toString()), Integer.parseInt(element .getAttribute("y").toString()), Integer .parseInt(element.getAttribute("width").toString()), Integer.parseInt(element.getAttribute("height") .toString())); }

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  • JNI AttachCurrentThread NULLs the jenv

    - by Damg
    Hello all, I'm currently in the process of adding JNI functionality into a legacy delphi app. In a single-threaded environment everything works fine, but as soon as I move into multi-threaded environment, things start to become hairy. My problem is that calling JavaVM^.AttachCurrentThread( JavaVM, @JEnv, nil ); returns 0, but puts the JEnv pointer to nil. I have no idea why jvm.dll should return a NULL pointer. Is there anything I am missing? Thank you in advance -- damg PS: * Environment: WinXP + JDK 1.6 * Using JNI.pas from http://www.pacifier.com/~mmead/jni/delphi/

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  • Can I configure Eclipse / JBoss integration so it does not rely on deploying Jars to the "server/def

    - by kellyfj
    I am using MyEclipse 7.5 with JBoss 4.2.3 GA. When I define my local development JBoss server in MyEclipse it always wants to deploy jars, wars etc. to the "server/default/deploy" directory. Unfortunately our JBoss directory structure for production is "server/XYZ/deploy/abc" (driven by a third party). As a result our Dev JBoss instances are different from our QA/Staging/Production JBoss instances. Is there a way to configure Eclipse to use JBoss but deploy to that specific folder path "server/XYZ/deploy/abc" rather than the default one "server/default/deploy"?

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  • PreparedStatement and setTimestamp in oracle jdbc

    - by Roman
    Hi everyone, I am using PreparedStatement with Timestamp in where clause: PreparedStatement s=c.prepareStatement("select utctimestamp from t where utctimestamp>=? and utctimestamp<?"); s.setTimestamp(1, new Timestamp(1273017600000L)); //2010-05-05 00:00 GMT s.setTimestamp(2, new Timestamp(1273104000000L)); //2010-05-06 00:00 GMT The result I get is different, when I have different time zones on the client computer. Is this a bug in Oracle jdbc? or correct behavior? The parameter is Timestamp, and I expected that no time conversions will be done on the way. The database column type is DATE, but I also checked it with TIMESTAMP column type with the same results. Is there a way to achieve correct result? I cannot change default timezone in the the whole application to UTC. Thanks for your help

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  • Connection Pool Strategy: Good, Bad or Ugly?

    - by Drew
    I'm in charge of developing and maintaining a group of Web Applications that are centered around similar data. The architecture I decided on at the time was that each application would have their own database and web-root application. Each application maintains a connection pool to its own database and a central database for shared data (logins, etc.) A co-worker has been positing that this strategy will not scale because having so many different connection pools will not be scalable and that we should refactor the database so that all of the different applications use a single central database and that any modifications that may be unique to a system will need to be reflected from that one database and then use a single pool powered by Tomcat. He has posited that there is a lot of "meta data" that goes back and forth across the network to maintain a connection pool. My understanding is that with proper tuning to use only as many connections as necessary across the different pools (low volume apps getting less connections, high volume apps getting more, etc.) that the number of pools doesn't matter compared to the number of connections or more formally that the difference in overhead required to maintain 3 pools of 10 connections is negligible compared to 1 pool of 30 connections. The reasoning behind initially breaking the systems into a one-app-one-database design was that there are likely going to be differences between the apps and that each system could make modifications on the schema as needed. Similarly, it eliminated the possibility of system data bleeding through to other apps. Unfortunately there is not strong leadership in the company to make a hard decision. Although my co-worker is backing up his worries only with vagueness, I want to make sure I understand the ramifications of multiple small databases/connections versus one large database/connection pool.

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  • Why is my quick sort so slow?

    - by user513075
    Hello, I am practicing writing sorting algorithms as part of some interview preparation, and I am wondering if anybody can help me spot why this quick sort is not very fast? It appears to have the correct runtime complexity, but it is slower than my merge sort by a constant factor of about 2. I would also appreciate any comments that would improve my code that don't necessarily answer the question. Thanks a lot for your help! Please don't hesitate to let me know if I have made any etiquette mistakes. This is my first question here. private class QuickSort implements Sort { @Override public int[] sortItems(int[] ts) { List<Integer> toSort = new ArrayList<Integer>(); for (int i : ts) { toSort.add(i); } toSort = partition(toSort); int[] ret = new int[ts.length]; for (int i = 0; i < toSort.size(); i++) { ret[i] = toSort.get(i); } return ret; } private List<Integer> partition(List<Integer> toSort) { if (toSort.size() <= 1) return toSort; int pivotIndex = myRandom.nextInt(toSort.size()); Integer pivot = toSort.get(pivotIndex); toSort.remove(pivotIndex); List<Integer> left = new ArrayList<Integer>(); List<Integer> right = new ArrayList<Integer>(); for (int i : toSort) { if (i > pivot) right.add(i); else left.add(i); } left = partition(left); right = partition(right); left.add(pivot); left.addAll(right); return left; } }

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