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  • ConcurentModificationException in Java HashMap

    - by Bear
    Suppose I have two methods in my classes, writeToMap() and processKey() and both methods are called by multiple threads. writeToMap is a method to write something in hashmap and processKey() is used to do sth based on the keySet of HashMap. Inside processKey, I first copy the originalMap before getting the key set. new HashMap<String, Map<String,String>(originalMap).get("xx").keySet(); But I am still getting ConcurrentModificationException even though I always copy the hashmap. Whats the problem?

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  • can the keyword 'this' be used in an abstract class in java

    - by Reddy
    I tried with below example, it is working fine. I expected it to pick sub-class's value since object won't be created for super class (as it is abstract). But it is picking up super class's field value only. Please help me understand what is the concepts behind this? abstract class SuperAbstract { private int a=2; public void funA() { System.out.println("In SuperAbstract: this.a "+a); } } class SubClass extends SuperAbstract { private int a=34; } I am calling new SubClass.funA(); I am expecting it to print 34, but it is printing 2.

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  • Question About Eclipse Java Debugger Conditional Breakpoints Inefficiency

    - by Personman
    I just set a conditional breakpoint in Eclipse's debugger with a mildly inefficient condition by breakpoint standards - checking whether a HashMap's value list (8 elements) contains Double.NaN. This resulted in an extremely noticeable slowdown in performance - after about five minutes, I gave up. Then I copy pasted the condition into an if statement at the exact same line, put a noop in the if, and set a normal breakpoint there. That breakpoint was reached in the expected 20-30 seconds. Is there something special that conditional breakpoints do that is different from this, or is Eclipse's implementation just kinda stupid? It seems like they could fairly easily just do exactly the same thing behind the scenes.

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  • Get n Number of words using regex in Java

    - by Aymon Fournier
    I have a section of a book, complete with punctuation, line breaks etc. and I want to be able to extract the first n words from the text, and divide that into 5 parts. Regex mystifies me. This is what I am trying. I creates an array of index size 0, with all the input text: public static String getNumberWords2(String s, int nWords){ String[] m = s.split("([a-zA-Z_0-9]+\b.*?)", (nWords / 5)); return "Part One: \n" + m[1] + "\n\n" + "Part Two: \n" + m[2] + "\n\n" + "Part Three: \n" + m[3] + "\n\n" + "Part Four: \n" + m[4] + "\n\n" + "Part Five: \n" + m[5]; } Thanks!

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  • Java action perfmored when text is enterd into a textarea

    - by adam08
    I'm wondering if someone can help me out. I'm entered a chacter into a text area from a button, and want to use the string entered into the textarea to retrieve words from a list. Bear in mind, there could be numerous characters entered. Is it possible for a text area to detect when text has been entered and to action it?

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  • Set the amount of rows JList show (Java)

    - by Alex Cheng
    Hi all. Problem: I have a method that creates a list from the parsed ArrayList. I manage to show the list in the GUI, without scrollbar. However, I am having problem setting it to show only the size of ArrayList. Meaning, say if the size is 6, there should only be 6 rows in the shown List. Below is the code that I am using. I tried setting the visibleRowCount as below but it does not work. I tried printing out the result and it shows that the change is made. private void createSuggestionList(ArrayList<String> str) { int visibleRowCount = str.size(); System.out.println("visibleRowCount " + visibleRowCount); listForSuggestion = new JList(str.toArray()); listForSuggestion.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); listForSuggestion.setSelectedIndex(0); listForSuggestion.setVisibleRowCount(visibleRowCount); System.out.println(listForSuggestion.getVisibleRowCount()); listScrollPane = new JScrollPane(listForSuggestion); MouseListener mouseListener = new MouseAdapter() { @Override public void mouseClicked(MouseEvent mouseEvent) { JList theList = (JList) mouseEvent.getSource(); if (mouseEvent.getClickCount() == 2) { int index = theList.locationToIndex(mouseEvent.getPoint()); if (index >= 0) { Object o = theList.getModel().getElementAt(index); System.out.println("Double-clicked on: " + o.toString()); } } } }; listForSuggestion.addMouseListener(mouseListener); textPane.add(listScrollPane); repaint(); } To summarize: I want the JList to show as many rows as the size of the parsed ArrayList, without a scrollbar. Any ideas? Please help. Thanks. Please let me know if a picture of the problem is needed in case I did not phrase my question correctly.

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  • different for lusses java

    - by Ayrton
    Hi I'm having some difficulties with the following problem: I'm making a little game where you're at a specific spot and each spot has each some possible directions. The available directions are N(ord),E(ast),S,W . I use the function getPosDirections to get the possible directions of that spot. The function returns the directions into an ArrayList e.g. for spot J3: [E,W] Now the game goes like this: 2 dices will be rolled so you get a number between 2 and 12, this number represents the number of steps you can make. What I want is an ArrayList of all the possible routes e.g.: I throw 3 and I'm currently at spot J3: [[E,N,E],[E,N,S],[E,S,E],[E,S,S],[W,N,E],[W,N,S],[W,S,E],[W,S,S]] How would obtain the last mentioned Array(list) Thanks in advance

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  • Singleton & Multithreading in Java

    - by vivek jagtap
    What is the preferred way to work with Singleton class in multithreaded environment? Suppose if I have 3 thread, and all they try to access getInstance() method of singleton class at the same time - What would happen if no synchronization is maintained? Is it good practice to use synchronized getInstance() method or use synchronized block inside getInstance(). Please advise if there is any other way out.

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  • Web service security not working. Java

    - by Nitesh Panchal
    Hello, I have a ejb module which contains my ejbs as well as web services. I am using Netbeans 6.8 and Glassfish V3 I right clicked on my web service and clicked "edit web service attributes" and then checked "secure service" and then selected keystore of my server. This is my sun-ejb-jar.xml file :- <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE sun-ejb-jar PUBLIC "-//Sun Microsystems, Inc.//DTD Application Server 9.0 Servlet 2.5//EN" "http://www.sun.com/software/appserver/dtds/sun-web-app_2_5-0.dtd"> <sun-ejb-jar> <security-role-mapping> <role-name>Admin</role-name> <group-name>Admin</group-name> </security-role-mapping> <security-role-mapping> <role-name>General</role-name> <group-name>General</group-name> </security-role-mapping> <security-role-mapping> <role-name>Member</role-name> <group-name>Member</group-name> </security-role-mapping> <enterprise-beans> <ejb> <ejb-name>MemberBean</ejb-name> <webservice-endpoint> <port-component-name>wsMember</port-component-name> <login-config> <auth-method>BASIC</auth-method> <realm>file</realm> </login-config> </webservice-endpoint> </ejb> </enterprise-beans> </sun-ejb-jar> Here MemberBean is my ejb and wsMember is my webservice. Then i made another project and added web service client and again right clicked on "edit web service attributes" and gave password as test and test. This username and password (test) is in Glassfish server in file realm. But when i try to invoke my webservice i always get SEC5046: Audit: Authentication refused for [test]. SEC1201: Login failed for user: test What am i doing wrong? Am i missing something?

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  • converting a UTC time to a local time zone in Java

    - by aloo
    I know this subject has been beaten to death but after searching for a few hours to this problem I had to ask. My Problem: do calculations on dates on a server based on the current time zone of a client app (iphone). The client app tells the server, in seconds, how far away its time zone is away from GMT. I would like to then use this information to do computation on dates in the server. The dates on the server are all stored as UTC time. So I would like to get the HOUR of a UTC Date object after it has been converted to this local time zone. My current attempt: int hours = (int) Math.floor(secondsFromGMT / (60.0 * 60.0)); int mins = (int) Math.floor((secondsFromGMT - (hours * 60.0 * 60.0)) / 60.0); String sign = hours > 0 ? "+" : "-"; Calendar now = Calendar.getInstance(); TimeZone t = TimeZone.getTimeZone("GMT" + sign + hours + ":" + mins); now.setTimeZone(t); now.setTime(someDateTimeObject); int hourOfDay = now.get(Calendar.HOUR_OF_DAY); The variables hour and mins represent the hour and mins the local time zone is away from GMT. After debugging this code - the variables hour, mins and sign are correct. The problem is hourOfDay does not return the correct hour - it is returning the hour as of UTC time and not local time. Ideas?

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  • using itext how to extracta string in java

    - by user2455183
    I am finding the string in between 123 and 321 and making it as bold. For that I used the Pattern to get the string before 123, text between 123 and 321 and text after 321. Could anyone please help me get all the strings between 123 and 321. Pattern p = Pattern.compile("^.*?(123)"); Matcher m = p.matcher(meredithEditorialSectionSegment); while (m.find()) { String desc = m.group(); String segDesc = (desc.substring(0, desc.length() - 3)); segmentDesc.add(new Chunk(segDesc, sectionDescriptionFont)); } descBold = meredithEditorialSectionSegment.substring(meredithEditorialSectionSegment.indexOf("123") + 3); descBold = descBold.substring(0, descBold.indexOf("321")); segmentDesc.add(new Chunk(descBold, sectionDescriptionBoldFont)); Matcher matcher = Pattern.compile("(?<=321).*").matcher(meredithEditorialSectionSegment); matcher.find(); segmentDesc.add(new Chunk(matcher.group(), sectionDescriptionFont));

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  • Java serialization problem

    - by stefan89
    I have two classes X and Y, like this: class X implements Serializable { int val1; Y val2; } class Y implements Serializable { int val; } I want to transmit an object of type X from a client to server but i can't because the class X has a field of type Y. I replaced the field of type Y with a field of type X in class X and it works.

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  • Java Detect Variable Change Using PropertyChangeSupport and PropertyChangeListener

    - by Sam
    I'm trying to print out debug statements when some third party code changes a variable. For example, consider the following: public final class MysteryClass { private int secretCounter; public synchronized int getCounter() { return secretCounter; } public synchronized void incrementCounter() { secretCounter++; } } public class MyClass { public static void main(String[] args) { MysteryClass mysteryClass = new MysteryClass(); // add code here to detect calls to incrementCounter and print a debug message } I don't have the ability to change the 3rd party MysteryClass, so I thought that I could use PropertyChangeSupport and PropertyChangeListener to detect changes to the secretCounter: public class MyClass implements PropertyChangeListener { private PropertyChangeSupport propertySupport = new PropertyChangeSupport(this); public MyClass() { propertySupport.addPropertyChangeListener(this); } public void propertyChange(PropertyChangeEvent evt) { System.out.println("property changing: " + evt.getPropertyName()); } public static void main(String[] args) { MysteryClass mysteryClass = new MysteryClass(); // do logic which involves increment and getting the value of MysteryClass } } Unfortunately, this did not work and I have no debug messages printed out. Does anyone see what is wrong with my implementation of the PropertyChangeSupport and Listener interfaces? I want to print a debug statement whenever incrementCounter is called or the value of secretCounter changes.

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  • Java for loop with multiple incrementers

    - by user2517280
    Im writing a program which combines the RGB pixel values for 3 images, e.g. red pixel of image 1, green pixel of image 2 and blue pixel of image 3 and I want to then create a final image of it. Im using the code below, but this seems to be incrementing x2 and x3 whilst x1 is the same, i.e. not giving the right pixel value for same co-ordinate for each image. for (int x = 0; x < image.getWidth(); x++) { for (int x2 = 0; x2 < image2.getWidth(); x2++) { for (int x3 = 0; x3 < image3.getWidth(); x3++) { for (int y = 0; y < image.getHeight(); y++) { for (int y2 = 0; y2 < image2.getHeight(); y2++) { for (int y3 = 0; y3 < image3.getHeight(); y3++) { So I was wondering if anyone can tell me how to iterate through each of the 3 images on the same co-ordinate, so for example read 1, 1 of each image and record the red, green and blue value accordingly. Apologies if it doesnt make complete sense, its a bit hard to explain. I can iterate the values for one image fine but when I add in another, things start to go a bit wrong as obviously its quite a bit more complicated! I was thinking it might be easier to create an array and replace the according values in that just not sure how to do that effectively either. Thanks

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  • What is Java Message Service (JMS) for?

    - by Daniel
    I am currently evaluating JMS and I don't get what I could use it for. Currently, I believe this would be a Usecase: I want to create a SalesInvoice PDF and print it when an SalesOrder leaves the Warehouse, so during the Delivery transaction I could send a transactional print request which just begins when the SalesOrder transaction completes successfully. Now I found out most JMS products are standalone server. Why would a need a Standalone Server for Message Processing, vs. e.g. some simple inproc processing with Quartz scheduler? How does it interact with my application? Isn't it much too slow? What are Usecases you already implemented successfully?

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