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  • Explicit constructor still has default values even though a default constructor is not invoked.

    - by Phoenix
    According to my understanding a default constructor initializes the state of the object to default values, so if i provide an explicit no-arg public constructor like this then how are the values of d and e still getting initialized to zero because in this case the default constructor is not invoked. public class B extends A{ private int d; private int e; public B() { System.out.println(d); System.out.println(e); } } EDIT:: The only thing default constructor does is call to super() then how come if i have a explicitly mentioned a constructor here and A has a protected variable say c which is initialized to 17 in its constructor. Should I not be explicitly calling super() to be able to see that change since I'm using my own constructor ? Why is B still getting the value of 17 through inheritance ?

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  • Compute hex color code for an arbitrary string

    - by user222164
    Heading Is there a way to map an arbitrary string to a HEX COLOR code. I tried to compute the HEX number for string using string hashcode. Now I need to convert this hex number to six digits which are in HEX color code range. Any suggestions ? String [] programs = {"XYZ", "TEST1", "TEST2", "TEST3", "SDFSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS"}; for(int i = 0; i < programs.length; i++) { System.out.println( programs[i] + " -- " + Integer.toHexString(programs[i].hashCode())); }

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  • Practicing inserting data into an array by using binary search, few problems

    - by HelpNeeder
    I'm trying to create a method which inserts and then sort elements in form of binary form. The problem I am experiencing that my code doesn't insert data correctly which means that output does not appear to be in order at all. The list is not organized, and data is added in order that is being inserted. Now, 2 questions, what am I doing wrong here? And how to fix this? public void insertBinarySearch(long value) // put element into array { int j = 0; int lower = 0; int upper = elems-1; int cur = 0; while (cur < elems) { curIn = (lower + upper ) / 2; if(a[cur] < value) { j = cur + 1; break; } else if(a[cur] > value) { j = cur; break; } else { if(a[cur] < value) lower = cur + 1; else upper = cur - 1; } } for(int k = elems; k > j; k--) a[k] = a[k-1]; a[j] = value; elems++; }

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  • Is catching NumberFormatException a bad practice?

    - by integeruser
    I have to parse a String that can assume hex values or other non-hex values 0xff, 0x31 or A, PC, label, and so on. I use this code to divide the two cases: String input = readInput(); try { int hex = Integer.decode(input); // use hex ... } catch (NumberFormatException e) { // input is not a hex, continue parsing } Can this code be considered "ugly" or difficult to read? Are there other (maybe more elegant) solutions? EDIT : I want to clarify that (in my case) a wrong input doesn't exist: i just need to distinguish if it is a hex number, or not. And just for completeness, i'm making a simple assebler for DCPU-16.

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  • Printing a list using reflection

    - by TFool
    public class Service{ String serviceName; //setter and getter } public class Version{ String VersionID; //setter and getter } public void test(Object list){ //it shd print the obtained list } List< Service list1; //Service is a Bean List< Version list2; //Version is a Bean test(list1); test(list2); Now the test method shd print the obtained list - (i.e) If the list is of type Service ,then serviceName should be printed using its getter. If the list type is Version versionID should be printed. Is it possible to achieve this without using Interface or abstract class?

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  • what is serialization and how it works

    - by Rozer
    I know the serialization process but have't implemented it. In my application i have seen there are various classes that has been implemented serilizable interface. consider following class public class DBAccessRequest implements Serializable { private ActiveRequest request = null; private Connection connection = null; private static Log log = LogFactory.getLog(DBAccessRequest.class); public DBAccessRequest(ActiveRequest request,Connection connection) { this.request = request; this.connection = connection; } /** * @return Returns the DB Connection object. */ public Connection getConnection() { return connection; } /** * @return Returns the active request object for the db connection. */ public ActiveRequest getRequest() { return request; } } just setting request and connection in constructor and having getter setter for them. so what is the use of serilizable implementation over here...

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  • "Overriding" instance variables in subtype: Possible risks?

    - by sebastiangeiger
    Say I had a class SuperClass and two subclasses SubClassA and SubClassB that inherit from SuperClass. abstract class SuperClass{ ... List someList; ... } class SubClassA extends SuperClass{ ... List<String> someList; ... } class SubClassB extends SuperClass{ ... List<Integer> someList; ... } That way it is convenient because I can get someList.size() in Superclass and have Typesafety in the Subclasses. The problem is that it does not "feel" right, can you think of potential hazards this apporach has that I am not aware of?

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  • Initial state of autoCreateRowSorter in Swing JTable

    - by Nazgulled
    I have this JTable on my Swing app with the autoCreateRowSorter enabled. My table only has 3 columns, two strings and one int, it works well for all of them when I click the column headers. However, I'm looking for way to do it programatically. I wanted to set the "initial state" for this table. With the Windows look and feel, the column header (when sorted) has a little arrow showing the sort order. But at startup that doesn't show, I have to do one initial click. How can I do that by code?

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  • getting node value exception

    - by Aswan
    Hi Folks <amount currency="USD">1000500</amount> while parsing above string i am getting only attribute value .when i try to get node value null pointer exception for getting node value using NodeList amountList= estimateElement.getElementsByTagName("amount"); Element amtElement= (Element)amountList.item(0); String amount=amtElement.getFirstChild().getnodevalue() Thanks in advance Aswan

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  • How to know any request type with comet in tomcat 6

    - by Alvin
    Hi, I want to create a chat application in Tomcat 6.0, but before allowing any user for chatting I want to authenticate a user or registering its account to the database by passing request to the servlets at the comet Event type Begin. But I don't know how to know about the request type. How can I know a user has already been logged in, or he is making a request for registering his account. How can I know this by implementing CometProcessor interface? Is there any better way to do that task?

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  • Limiting Row Selection in JTable

    - by Pat
    Is there an easy way to limit the total selection of rows in a JTable? I mean I'd like to allow the user to use shift and ctrl to select a maximum of X rows. If he clicks again on a row it would cancel out all the selections. Sort of how it currently behaves, but while limiting the total amount of selected rows. Here's my current implementation, I'm kind of clueless on how to limit the selection graphically. public class RoomsListView extends AbstractViewPanel { public RoomsListView(DefaultController controller) { this.controller = controller; initUI(); } private void initUI() { tableT = new JTable(RoomsModel.getInstance()); sorter = new TableRowSorter<RoomsModel>(RoomsModel.getInstance()); tableT.setRowSorter(sorter); tableT.setPreferredScrollableViewportSize(new Dimension(CUSTOM_TABLE_WIDTH, CUSTOM_TABLE_HEIGHT)); tableT.addMouseListener(new MouseAdapter() { public void mouseClicked(MouseEvent e) { rowClickedPerformed(e); } }); } private void rowClickedPerformed(MouseEvent e) { } public void modelPropertyChange(PropertyChangeEvent evt) { } public JTable getTable() { return tableT; } private final int CUSTOM_TABLE_WIDTH = -1; private final int CUSTOM_TABLE_HEIGHT = 150; private JTable tableT; private DefaultController controller; private TableRowSorter<RoomsModel> sorter; }

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  • Vertical line on HxW canvas of pixels

    - by bobby williams
    I searched and found nothing. I'm trying to draw lines (simple y=mx+b ones) on a canvas of black pixels. It works fine, but no line occurs when it is vertical. I'm not sure why. My first if statement checks if the denominator is zero, therefore m is undefined and no need for a line equation. My second and third if statement check how steep it is and based on that, calculate the points in between. I don't think there is a need for other classes, since I think there is a bug in my code or I'm just not translating the mathematics into code properly. If more is needed, I'll be happy to post more. /** * Returns an collection of points that connects p1 and p2 */ public ArrayList getPoints() { ArrayList points = new ArrayList(); // checks to see if denominator in m is zero. if zero, undefined. if ((p2.getX() - p1.getX()) == 0) { for (int y = p1.getY(); y<p2.getY(); y++) { points.add(new Point(p1.getX(), y, getColor())); } } double m = (double)(p2.getY()-p1.getY())/(double)(p2.getX()-p1.getX()); int b = (int)(p1.getY() - (m * p1.getX())); // checks to see if slope is steep. if (m > -1 || m < 1) { for (int x = p1.getX(); x<p2.getX(); x++) { int y = (int) ((m*x)+b); points.add(new Point(x, y, getColor())); } } // checks to see if slope is not steep. if (m <= -1 || m >= 1) { for (int y = p1.getY(); y<p2.getY(); y++) { int x = (int) ((y-b)/m); points.add(new Point(x, y, getColor())); } } return points; }

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  • adding org.springframework.test package to spring-2.5.6-SEC01.jar in netbeans

    - by John
    This is probably very simple, however I can't get this to work. I want to use AbstractDependencyInjectionSpringContextTest class which is in org.springframework.test package. This package is not included in Netbeans' spring library, so I want to add it. So what I have tried so far is: copy and paste "test" directory (downloaded from spring) into the Netbeans' spring-2.5.6-SEC01.jar file (copy it to org.springframework directory in that jar so I can use org.springframework.test to import it). If I go to project/libraries in Netbeans it is there, but when I try to import org.springframework.test.*; the autocomplition doesn't give me the option to choose test directory from org.soringframework package. create a new library which points to "test" directory and add it to the project- as there is no any jar file in "test" I'm not sure what path should I use to import it. I'm pretty sure this is something very simple but I'm still a novice and can't figure this out.

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  • How do you search through a map?

    - by Jack Null
    I have a map: Map<String, String> ht = new HashMap(); and I would like to know how to search through it and find anything matching a particular string. And if it is a match store it into an arraylist. The map contains strings like this: 1,2,3,4,5,5,5 and the matching string would be 5. So for I have this: String match = "5"; ArrayList<String> result = new ArrayList<String>(); Enumeration num= ht.keys(); while (num.hasMoreElements()) { String number = (String) num.nextElement(); if(number.equals(match)) { result.add(number); } }

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  • JDOQL Any way to avoid multiple .contains() calls in the query when searching for the presence of on

    - by Finbarr
    The question pretty much says it all. If I have a class Class A public class A { ... private List<String> keys; ... } And I want to select all A instances from the DataStore that have atleast one of a List of keys, is there a better way of doing it than this: query = pm.newQuery(A.class); query.setFilter("keys.contains(:key1) || keys.contains(:key2) || keys.contains(:key3)"); List<A> results = (List<A>)query.execute(key1, key2, key3); This has not yet been implemented, so I am open to radical suggestions.

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  • How to show alert in a jsp from a servlet and then redirect to another jsp?

    - by Xaul Omar Tobar
    I tried this but does not display the message only redirects login.jsp <form method="post" action="Login_Servlet" > <input name="idUsuario" type="text"/> <input name="password" type="password" /> <button type="submit">Entrar</button> </form> Login_Servlet response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); String userid= request.getParameter("idUser"); String password = request.getParameter("password"); Login_Service login_Service = new Login_Service(); boolean result = login_Servicio.aut(userid, password); Usuario user = login_Servicio.getUsuariosByUsuario(userid); if(result == true){ request.getSession().setAttribute("user", user); response.sendRedirect("vistas/Inicio.jsp"); } else{ out.println("<script type=\"text/javascript\">"); out.println("alert('User or password incorrect');"); out.println("</script>"); response.sendRedirect("index.jsp"); } Is it possible to display a message like this? if so I'm doing wrong?

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  • Strange "cache" effect between client and server

    - by mark
    I use a Socket-based connection between Client and server with ObjectOutputStream. The objects serialized and exchanged have this structure: public class RichiestaSalvataggioArticolo implements Serializable { private ArticoloDati articolo; public RichiestaSalvataggioArticolo(ArticoloDati articolo) { this.articolo = articolo; } @Override public void ricevi(GestoreRichieste gestore) throws Exception { gestore.interpreta(this); } public ArticoloDati getArticolo() { return articolo; } } the issue is that when I try to exchange messages between C/S with incapsulated content very similar (ArticoloDati whom differ only in 2 fields out of 10), the Client sends an ArticoloDati, but the Server receives the previous one. Does the ObjectOutputStream implement some kind of cache or memory between the calls, that fails to recognize that my 2 objects are different because they are very similar?

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  • WHY HAVE YOU ROMOVED MY POST? [closed]

    - by Eddy Freeman
    I posted a question about how to rotate a tile in BufferedImage. I did it in the morning and you removed it. Why have you removed it again? What is wrong with the posts? Tell me before i become angry. You have removed the post twice without informing/telling me the problem. with the posts What is wrong? Tell me. Reply to this post and tell me what is wrong.

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  • Speed/expensive of SQLite query vs. List.contains() for "in-set" icon on list rows

    - by kpdvx
    An application I'm developing requires that the app main a local list of things, let's say books, in a local "library." Users can access their local library of books and search for books using a remote web service. The app will be aware of other users of the app through this web service, and users can browse other users' lists of books in their library. Each book is identified by a unique bookId (represented as an int). When viewing books returned through a search result or when viewing another user's book library, the individual list row cells need to visually represent if the book is in the user's local library or not. A user can have at most 5,000 books in the library, stored in SQLite on the device (and synchronized with the remote web service). My question is, to determine if the book shown in the list row is in the user's library, would it be better to directly ask SQLite (via SELECT COUNT(*)...) or to maintain, in-memory, a List or int[] array of some sort containing the unique bookIds. So, on each row display do I query SQLite or check if the List or int[] array contains the unique bookId? Because the user can have at most 5,000 books, each bookId occupies 4 bytes so at most this would use ~ 20kB. In thinking about this, and in typing this out, it seems obvious to me that it would be far better for performance if I maintained a list or int[] array of in-library bookIds vs. querying SQLite (the only caveat to maintaining an int[] array is that if books are added or removed I'll need to grow or shrink the array by hand, so with this option I'll most likely use an ArrayList or Vector, though I'm not sure of the additional memory overhead of using Integer objects as opposed to primitives). Opinions, thoughts, suggestions?

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