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  • Java inheritance question

    - by Milos
    I have an abstract class Airplane, and two classes PassengerAirplane and CargoAirplane, which extend class Airplane. I also have an interface Measurable, and two classes that implement it - People and Containers. So, Airplane can do many things on its own, and there is a method which allows measurable things to be added to the airplane (called addAMeasurableThing). The only difference between PassengerAirplane/CargoAirplane and just an Airplane is that addAMeasurableThing should only accept People / Containers, and not any kind Measurable things. How do I implement this? I tried doing: Airplane class: public abstract Airplane addAMeasurableThing (Measurable m, int position); PassengerAirplane class: public Airplane addAMeasurableThing (Measurable m, int position) { if (m instanceof People)... CargoAirplane class: public Airplane addAMeasurableThing (Measurable m, int position) { if (m instanceof Containers)... But when I was debugging it, I've noticed that addAMeasurableThing in the CargoAirplane class never gets called, because both methods have the same signature. So how can the appropriate PassengerAirplane/CargoAirplane's addAMeasurableThing be called, depending on the type of Measurable thing that is being passed on? Thanks!

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  • A question in java.lang.Integer internal code

    - by Daziplqa
    Hi folks, While looking in the code of the method: Integer.toHexString I found the following code : public static String toHexString(int i) { return toUnsignedString(i, 4); } private static String toUnsignedString(int i, int shift) { char[] buf = new char[32]; int charPos = 32; int radix = 1 << shift; int mask = radix - 1; do { buf[--charPos] = digits[i & mask]; i >>>= shift; } while (i != 0); return new String(buf, charPos, (32 - charPos)); } The question is, in toUnsignedString, why we create a char arr of 32 chars?

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  • Best practices for Java logging from multiple threads?

    - by Jason S
    I want to have a diagnostic log that is produced by several tasks managing data. These tasks may be in multiple threads. Each task needs to write an element (possibly with subelements) to the log; get in and get out quickly. If this were a single-task situation I'd use XMLStreamWriter as it seems like the best match for simplicity/functionality without having to hold a ballooning XML document in memory. But it's not a single-task situation, and I'm not sure how to best make sure this is "threadsafe", where "threadsafe" in this application means that each log element should be written to the log correctly and serially (one after the other and not interleaved in any way). Any suggestions? I have a vague intuition that the way to go is to use a queue of log elements (with each one able to be produced quickly: my application is busy doing real work that's performance-sensitive), and have a separate thread which handles the log elements and sends them to a file so the logging doesn't interrupt the producers. The logging doesn't necessarily have to be XML, but I do want it to be structured and machine-readable. edit: I put "threadsafe" in quotes. Log4j seems to be the obvious choice (new to me but old to the community), why reinvent the wheel...

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  • How does one convert from a Java resultset to ColdFusion query in Railo?

    - by Shawn Grigson
    The following works fine in CFMX 7 and CF8, and I'd assume CF9 as well: <!--- 'conn' is a JDBC connection ---> <cfset stat = conn.createStatement() /> <cfset rs = stat.executeQuery(trim(arguments.sql)) /> <!--- convert this Java resultset to a CF query recordset ---> <cfset queryTable = CreateObject("java", "coldfusion.sql.QueryTable")> <cfset queryTable.init(rs) > <cfset query = queryTable.FirstTable() /> This creates a statement using a JDBC driver, executes a query against it, putting it into a java resultset, and then coldfusion.sql.QueryTable is instantiated, passed the Java resulset object, and then queryTable.FirstTable() is called, which returns an actual coldfusion resultset (for cfloop and the like). The problem comes with a difference in Railo's implementation. Running this code in Railo returns the following error: No matching Constructor for coldfusion.sql.QueryTable(org.sqlite.RS) found. I've dumped the Railo java object, and don't see init() among the methods. Am I missing something simple? I'd love to get this working in Railo as well. Please note: I am doing a DSN-less connection to a SQLite db. I understand how to set up a CF datasource. My only hiccup at this point is doing the translation from a Java result set to a Railo query.

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  • Java: Print and access List <String[]>

    - by battousai622
    Im reading in a file and storing it in t1. How do i access the elements in t1? When i try to print it i get addresses instead of values. Also whats the dif between string and string[]? CSVReader reader = new CSVReader(new FileReader("src/new_acquisitions.csv")); List <String[]> t1 = reader.readAll(); int i = 0 while(i < t1.size()) { System.out.println(t1.get(i)); i++; } output: [Ljava.lang.String;@9304b1 [Ljava.lang.String;@190d11 [Ljava.lang.String;@a90653 [Ljava.lang.String;@de6ced

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  • Java - Highest, Lowest and Average

    - by Emily
    Hello, I've just started studying and I need help on one of my exercises. I need the end user to input a rain fall number for each month. I then need to out put the average rainfall, highest month and lowest month and the months which rainfall was above average. I keep getting the same number in the highest and lowest and I have no idea why. I am seriously pulling my hair out. Any help would be greatly appreciated. This is what I have so far: public class rainfall { /** * @param args */ public static void main(String[] args) { int[] numgroup; numgroup = new int [13]; ConsoleReader console = new ConsoleReader(); int highest; int lowest; int index; int tempVal; int minMonth; int minIndex; int maxMonth; int maxIndex; System.out.println("Welcome to Rainfall"); for(index = 1; index < 13; index = index + 1) { System.out.println("Please enter the rainfall for month " + index); tempVal = console.readInt(); while (tempVal>100 || tempVal<0) { System.out.println("The rating must be within 0...100. Try again"); tempVal = console.readInt(); } numgroup[index] = tempVal; } lowest = numgroup[0]; for(minIndex = 0; minIndex < numgroup.length; minIndex = minIndex + 1); { if (numgroup[0] < lowest) { lowest = numgroup[0]; minMonth = minIndex; } } highest = numgroup[1]; for(maxIndex = 0; maxIndex < numgroup.length; maxIndex = maxIndex + 1); { if (numgroup[1] > highest) { highest = numgroup[1]; maxMonth = maxIndex; } } System.out.println("The average monthly rainfall was "); System.out.println("The lowest monthly rainfall was month " + minIndex); System.out.println("The highest monthly rainfall was month " + maxIndex); System.out.println("Thank you for using Rainfall"); } private static ConsoleReader ConsoleReader() { return null; } } Thanks, Emily

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  • Java Localization & ResourceManager

    - by Gopalakrishnan Subramani
    I want to add resources to my netbeans project but I don't know where to add or how to get the added resource via ResourceManager so that I can localize the text. I could not find any dummy guide to add the resource files and read the localized strings using resource manager. What is the format of the resource file? It is .properties or a xml file? Can you help me?

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  • Writing XML in different character encodings with Java

    - by Roman Myers
    I am attempting to write an XML library file that can be read again into my program. The file writer code is as follows: XMLBuilder builder = new XMLBuilder(); Document doc = builder.build(bookList); DOMImplementation impl = doc.getImplementation(); DOMImplementationLS implLS = (DOMImplementationLS) impl.getFeature("LS", "3.0"); LSSerializer ser = implLS.createLSSerializer(); String out = ser.writeToString(doc); //System.out.println(out); try{ FileWriter fstream = new FileWriter(location); BufferedWriter outwrite = new BufferedWriter(fstream); outwrite.write(out); outwrite.close(); }catch (Exception e){ } The above code does write an xml document. However, in the XML header, it is an attribute that the file is encoded in UTF-16. when i read in the file, i get the error: "content not allowed in prolog" this error does not occur when the encoding attribute is manually changed to UTF-8. I am trying to get the above code to write an XML document encoded in UTF-8, or successfully parse a UTF-16 file. the code for parsing in is DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder loader = factory.newDocumentBuilder(); Document document = loader.parse(filename); the last line returns the error.

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  • Java-Instance Method Call

    - by Gogi
    When I call as instance method of a class as follows : object_name.function_name(); how the compiler knows that the "function_name" has to be called for that "object_name" behind the scenes ?

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  • I have a problem wit the following code of java

    - by Sanjeev
    public class b { public static void main(String[] args) { byte b = 1; long l = 127; // b = b + l; // 1 if I try this then its not compile b += l; // 2 if I try this its compile System.out.println(b); } } I don't understand why b=b+1; is not compile and if I write b+=l; then it compile an run.

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  • JAVA and how to execute user-code

    - by Parhs
    Hello. I am building a tool which should do a diagnosis based on some values... It should be user extensible so hardcoding the conditions isnt a solution... Suppose that we have a blood test... example ... WBC , ALDO ... And i want the user to be able to write somehow scripts if (WBC.between(4,10) && ALDO.greater(5) || SOMETHINGELESE.isTrue()) ..... diagnosis="MPLAMPLA"... The problem is 1)Write my parser 2)Or try to find something that executes user conditionals at runtime and customize it.. 3)another way Please help,ideas needed!

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  • Java Backgroundworker: Scope of Widget to be updated unclear

    - by erlord
    Hi all, I am trying to understand the mechanism of org.jdesktop.swingx.BackgroundWorker. Their javadoc presents following example: final JLabel label; class MeaningOfLifeFinder implements BackgroundListener { public void doInBackground(BackgroundEvent evt) { String meaningOfLife = findTheMeaningOfLife(); evt.getWorker().publish(meaningOfLife); } public void process(BackgroundEvent evt) { label.setText("" + evt.getData()); } public void done(BackgroundEvent evt) {} public void started(BackgroundEvent evt) {} } (new MeaningOfLifeFinder()).execute(); Apart from the fact that I doubt the result will ever get published, I wonder how label is passed to the process method, where it is being updated. I thought it's scope is limited to the outside of the BackgroudListener implementation. Quite confused I am ... any answers for me? Thanks in advance

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  • Help with hash tables and quadratic probing in Java

    - by user313458
    I really need help with inserting into a hash table. I'm just not totally getting it right now. Could someone explain quadratic and linear probing in layman's terms? public void insert(String key) { int homeLocation = 0; int location = 0; int count = 0; if (find(key).getLocation() == -1) // make sure key is not already in the table { //****** ADD YOUR CODE HERE FOR QUADRATIC PROBING ******** } } This is the code I'm working on. I'm not asking anyone to do it, I just really need help with learning the whole concept Any help would be greatly appreciated.

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  • [Java] Form data transition into entity beans to persist them by the server side ORM

    - by cscsaba242
    Hello guys, Is there any good explanation or tutorial which describes the common way how can we create entity beans from the received data of the form ? The main reason of my question the treating the received ids (e.g id of country,city and so forth) which is the way from the id to entity ? Example: ................Client side form username:String countryid:Integer (could be a drop down) ................Server side entities public class UserBean { String username; CountryBean Country; } public class CountryBean { String cityname; Integer id; } ............................................ Maybe the question is dependent of the used technology, but I guess there is a very common way. I would like to comprehend the conventional approach of this problem. (For the sake of the completeness I would like to save the form data (received by Stripes) by JPA) Thanks advance. cscsaba242

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  • java.net.URISyntaxException

    - by aayushi soni
    Hi, I have get this exception. but this exception is not reproduced again. I want to get the cause of this Exception Caught while Checking tag in XMLjava.net.URISyntaxException: Illegal character in opaque part at index 2: C:\Documents and Settings\All Users\.SF\config\sd.xml stacktrace net.sf.saxon.trans.XPathException. Why this exception occured. How to deal with so it will not reproduce.

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  • Java Stop Server Thread

    - by ikurtz
    the following code is server code in my app: private int serverPort; private Thread serverThread = null; public void networkListen(int port){ serverPort = port; if (serverThread == null){ Runnable serverRunnable = new ServerRunnable(); serverThread = new Thread(serverRunnable); serverThread.start(); } else { } } public class ServerRunnable implements Runnable { public void run(){ try { //networkConnected = false; //netMessage = "Listening for Connection"; //networkMessage = new NetworkMessage(networkConnected, netMessage); //setChanged(); //notifyObservers(networkMessage); ServerSocket serverSocket = new ServerSocket(serverPort, backlog); commSocket = serverSocket.accept(); serverSocket.close(); serverSocket = null; //networkConnected = true; //netMessage = "Connected: " + commSocket.getInetAddress().getHostAddress() + ":" + //commSocket.getPort(); //networkMessage = new NetworkMessage(networkConnected, netMessage); //setChanged(); //notifyObservers(networkMessage); } catch (IOException e){ //networkConnected = false; //netMessage = "ServerRunnable Network Unavailable"; //System.out.println(e.getMessage()); //networkMessage = new NetworkMessage(networkConnected, netMessage); //setChanged(); //notifyObservers(networkMessage); } } } The code sort of works i.e. if im attempting a straight connection both ends communicate and update. The issue is while im listening for a connection if i want to quit listening then the server thread continues running and causes problems. i know i should not use .stop() on a thread so i was wondering what the solution would look like with this in mind? EDIT: commented out unneeded code.

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  • Problem with imbricate panels in java...

    - by stefan89
    i have a panel in another panel and i want to access an member of the child panel from the parent panel. The child panel reference that is in the parent panel doesn't see all the members that it has. Thanks! PS : the members i can't access are public

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  • Java Swing - Drawing markers on JSlider.

    - by Tony Day
    Hi, I have a progress bar which inherits from JSlider to provide highlighting functionality. Highlights can be added to the slider at a point (and a Color) and these are then painted onto the control. As follows: The problem is that I cannot get the highlights in the right place, they need to be in the same location as the markers. I also do not know how to retrieve the left and right margins to where the markers start and end. Is there anyway to get the coordinates of each marker? Or perhaps a better way of performing this task? Many Thanks!

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  • Passing pointer position to an object in Java.

    - by Gabriel A. Zorrilla
    I've got a JPanel class called Board with a static subclass, MouseHanlder, which tracks the mouse position along the appropriate listener in Board. My Board class has fields pointerX and pointerY. How do i pass the e.getX() and e.getY() from the MouseHandler subclass to its super class JPanel? I tried with getters, setters, super, and cant get the data transfer between subclass and parent class. I'm certain it's a concept issue, but im stuck. Thanks!

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  • java Properties - to expose or not to expose?

    - by ring bearer
    This might be an age old problem and I am sure everyone has their own ways. Suppose I have some properties defined such as secret.user.id=user secret.password=password website.url=http://stackoverflow.com Suppose I have 100 different classes and places where I need to use these properties. Which one is good (1) I create a Util class that will load all properties and serve them using a key constant Such as : Util is a singleton that loads all properties and keeps up on getInstance() call. Util myUtil = Util.getInstance(); String user = myUtil.getConfigByKey(Constants.SECRET_USER_ID); String password = myUtil.getConfigByKey(Constants.SECRET_PASSWORD); .. //getConfigByKey() - inturns invokes properties.get(..) doSomething(user, password) So wherever I need these properties, I can do steps above. (2) I create a meaningful Class to represent these properties; say, ApplicationConfig and provide getters to get specific properties. So above code may look like: ApplicationConfig config = ApplicationConfig.getInstance(); doSomething(config.getSecretUserId(), config.getPassword()); //ApplicationConfig would have instance variables that are initialized during // getInstance() after loading from properties file. Note: The properties file as such will have only minor changes in the future. My personal choice is (2) - let me hear some comments?

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  • Is java HashMap.clear() and remove() memory effective?

    - by Shaman
    Consider the follwing HashMap.clear() code: /** * Removes all of the mappings from this map. * The map will be empty after this call returns. */ public void clear() { modCount++; Entry[] tab = table; for (int i = 0; i < tab.length; i++) tab[i] = null; size = 0; } It seems, that the internal array (table) of Entrys is never shrinked. So, when I add 10000 elements to a map, and after that call map.clear(), it will keep 10000 nulls in it's internal array. So, my question is, how does JVM handle this array of nothing, and thus, is HashMap memory effective?

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  • Java - Problem in JTree

    - by Yatendra Goel
    There are 2 JTree: JTree1 and JTree2. Note that the nodes (country, city, colors, blue ...) all will be implemented as JCheckboxes so that user can select particular colors for each city or for the whole country by selecting their corresponding checkboxes. Problems: Q1. I want that each country or city can have its own colors selected. Means if a user wants city1.1 to have colors blue and violet and city2.1 to have colors red, then he first have to select the city1.1 checkbox and then select blue and violet, and after that when he selects city2.1, then the checkboxes blue and violet are deselected automatically so that user can select the colors for city2.1. But when the user selects the city1.1 again, then the JTree2should show the selected colors (bule and violet) for city1.1. So for this purpose, Is the JTree (with its nodes as checkboxes) correct option to implement or I should use some other JComponent? If JTree is a correct option, then how can I remember the colors of each city?

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  • Java: JAX-WS passing authentication info to a call to webservice

    - by agnieszka
    I am using JAX-WS. I am connecting to .NET webservice that requires authentication. I first call the Authentication.asmx so that I can be authenticated. The call returns me a LoginResult that contains a cookie name. Then I call another webservice and I need to somehow pass this cookie or a cookie name. and I don't know how. Here is the code: //first service that returns login information Authentication auth = new Authentication(new URL("the_url"), new QName("http://schemas.microsoft.com/sharepoint/soap/", "Authentication")); LoginResult result = auth.getAuthenticationSoap().login(HTTPuserName, HTTPpassword); //i need to pass cookie or cookie name or any other login information to call to this service Copy copyService = new Copy(new URL("service_url"), new QName("http://schemas.microsoft.com/sharepoint/soap/", "Copy")); BindingProvider p = (BindingProvider) copyService.getCopySoap();

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