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  • Java's Swing Threading

    - by nevets1219
    My understanding is that if I start up another thread to perform some actions, I would need to SwingUtilities.invokeAndWait or SwingUtilities.invokeLater to update the GUI while I'm in said thread. Please correct me if I'm wrong. What I'm trying to accomplish is relatively straightforward: when the user clicks submit, I want to (before performing any actions) disable the submit button, perform the action, and at the end of the action re-enable the button. My method to perform the action updates the GUI directly (displays results) when it gets the results back. This action basically queries a server and gets some results back. What I have so far is: boolean isRunning = false; synchronized handleButtonClick() { if ( isRunning == false ) { button.setEnabled( false ); isRunning = true; doAction(); } } doAction() { new Thread() { try { doAction(); // Concern A } catch ( ... ) { displayStackTrace( ... ); // Concern B } finally { SwingUtilities.invokeLater ( /* simple Runnable to enable button */ ); isRunning = false; } } } For both of my concerns above, do I would have to use SwingUtilities.invokeAndWait since they both will update the GUI? All GUI updates revolve around updating JTextPane. Do I need to in my thread check if I'm on EDT and if so I can call my code (regardless of whether it updates the GUI or not) and NOT use SwingUtilities.invokeAndWait?

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  • permute data for a HashMap in Java

    - by tuxou
    hi i have a linkedhashmap and i need to permute (change the key of the values) between 2 random values example : key 1 value 123 key 2 value 456 key 3 value 789 after random permutation of 2 values key 1 value 123 key 2 value 789 key 3 value 456 so here I permuted values between key 2 and key 3 thank you; sample of the code of my map : Map map = new LinkedHashMap(); map =myMap.getLinkedHashMap(); Set key = map.keySet(); for(Iterator it = cles.iterator(); it.hasNext();) { Integer cle = it.next(); ArrayList values = (ArrayList)map.get(cle);//an arrayList of integers int i = 0; while(i < values.size()) { //i donno what to do here i++; } }

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  • Java: refactoring static constants

    - by akf
    We are in the process of refactoring some code. There is a feature that we have developed in one project that we would like to now use in other projects. We are extracting the foundation of this feature and making it a full-fledged project which can then be imported by its current project and others. This effort has been relatively straight-forward but we have one headache. When the framework in question was originally developed, we chose to keep a variety of constant values defined as static fields in a single class. Over time this list of static members grew. The class is used in very many places in our code. In our current refactoring, we will be elevating some of the members of this class to our new framework, but leaving others in place. Our headache is in extracting the foundation members of this class to be used in our new project, and more specifically, how we should address those extracted members in our existing code. We know that we can have our existing Constants class subclass this new project's Constants class and it would inherit all of the parent's static members. This would allow us to effect the change without touching the code that uses these members to change the class name on the static reference. However, the tight coupling inherent in this choice doesn't feel right. before: public class ConstantsA { public static final String CONSTANT1 = "constant.1"; public static final String CONSTANT2 = "constant.2"; public static final String CONSTANT3 = "constant.3"; } after: public class ConstantsA extends ConstantsB { public static final String CONSTANT1 = "constant.1"; } public class ConstantsB { public static final String CONSTANT2 = "constant.2"; public static final String CONSTANT3 = "constant.3"; } In our existing code branch, all of the above would be accessible in this manner: ConstantsA.CONSTANT2 I would like to solicit arguments about whether this is 'acceptable' and/or what the best practices are.

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  • Java Download Concurrent Data

    - by xger86x
    Hi, i'm developing an app which download map tiles around different places in a city. To do this, i have one thread for each place in which i select the tiles and create a thread to download each. Well, the question is how to avoid creating a thread for a tile that already exists in the thread pool. Should not just check if the file exists, since it is possible that the thread for that tile already exists (other place already need that tile) but the file has not been created- Any idea? Thanks

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  • java: converting part of a ByteBuffer to a string

    - by Jason S
    I have a ByteBuffer containing bytes that were derived by String.getBytes(charsetName), where "containing" means that the string comprises the entire sequence of bytes between the ByteBuffer's position() and limit(). What's the best way for me to get the string back? (assuming I know the encoding charset) Is there anything better than the following (which seems a little clunky) byte[] ba = new byte[bbuf.remaining()]; bbuf.get(ba); try { String s = new String(ba, charsetName); } catch (UnsupportedEncodingException e) { /* take appropriate action */ }

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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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  • Simple Question:Output of below Java program

    - by Abhishek Jain
    public class abc1 { private String s; public abc1(String s){this.s=s;} public static void main(String args[]) { HashSet<Object> hs=new HashSet<Object>(); abc1 a1= new abc1("abc"); abc1 a2= new abc1("abc"); String s1= new String("abc"); String s2= new String("abc"); hs.add(a1); hs.add(a2); hs.add(s1); hs.add(s2); System.out.println(hs.size()); } } Why above program output is 3?

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  • Sorting an array of strings in reverse alphabetical order in Java

    - by Quacky
    I've been tasked with turning this code into a reverse sort, but for the life of me cannot figure out how to do it. These are my sort, findlargest and swap methods. I have a feeling I am missing something glaringly obvious here, any help would be really appreciated. public static void sort(String[] arr) { for (int pass = 1; pass < arr.length; pass++) { int largestPos = findLargest(arr, arr.length - pass); if (largestPos != arr.length - pass) { swap(arr, largestPos, arr.length - pass); } } } public static int findLargest(String[] arr, int num) { int largestPos = 0; for (int i = 1; i <= num; i++) { if (arr[i].compareToIgnoreCase(arr[largestPos]) > 0) { largestPos = i; } } return largestPos; } public static void swap(String[] arr, int first, int second) { String temp = arr[first]; arr[first] = arr[second]; arr[second] = temp; } }

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  • Need to split a string into two parts in java

    - by Reddy
    I have a string which contains a contiguous chunk of digits and then a contiguous chunk of characters. I need to split them into two parts (one integer part, and one string). I tried using String.split("\D", 1), but it is eating up first character. I checked all the String API and didn't find a suitable method. Is there any method for doing this thing?

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  • Download Large Files using java

    - by angelina
    Dear All, I M building a application in which i want to download large files on handset (mobile),but if size of file is large i m getting exception socket exception-broken pipe . inputStream = new FileInputStream(path); byte[] buffer = new byte[1024]; int bytesRead = 0; do { bytesRead = inputStream.read(buffer, offset, buffer.length); resp.getOutputStream().write(buffer, 0, bytesRead); } while (bytesRead == buffer.length); resp.getOutputStream().flush(); }

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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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  • Deferred printing in Java

    - by Bober02
    I have a specific issue with general console printing and I was wondering whether anyone has a solution for it. I am trying to print a dataTable which would look like sth like this: Table ---------------------- Name |Surname | ---------------------- Mike |Mikhailowish| Rafaello|Mirena | and so on. In order to print the border of the bar I need to know what the maximum length of each column value is. I don't want to go through the whole database to find that out and then again to print it. I would rather like to do sth like: System.out.printLater(s); //herejust leave a pointer to a StringBuilder you will build ... s.append("--------"); ... System.out.printAllDeferred(); I understand the above is probably in 99.99999% chances impossible, but perhaps you guys have a clever way of achieving the above?

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  • Exception and Inheritance in JAVA

    - by user1759950
    Suppose we have this problem public class Father{ public void method1(){...} } public class Child1 extends Father{ public void method1() throws Exception{ super.method1(); ... } } Child1 extends Father and override method1 but given implementation Child1.method1 now throws a exception, this wont compile as override method can't throw new exceptions. What is the best solution? Propagate the required exception to the Father.. to me this is against encapsulation, inheritance and general OOP ( the father potentially throw and exception that will never happen ) Use a RuntimeException instead? This solution wont propagate the Exception to the father but I read In Oracle docs and others sources states class of exceptions should be used when "Client code cannot do anything" this is not that case, this exception will b useful to recover blablabla ( why is wrong to use RuntimeException instead? ) Other.. thanks, Federico

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  • Java: stopping long HTTP operations

    - by kilonet
    I'm using Apache Common library for HTTP operations: HttpClient client = getClient(); PutMethod put = new PutMethod(url); FileRequestEntity countingFileRequestEntity = new FileRequestEntity(file, "application/octet-stream"); put.setRequestEntity(countingFileRequestEntity); client.executeMethod(put); put.releaseConnection(); I wonder how can safely interrup long HTTP operation. Running it in new thread and stopping it seems to be wrong way. HttpMethodBase has abort() method, but I can't understand how to use it because client.executeMethod blocks execution until it complets

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  • Java OCR Help Needed

    - by maSnun
    Hello, How do I detect all the characters in an image? The image is in png and the font is constant. For simplicity, lets assume that the image has only numeric digits and there are only 4 digits on an image. I need to read all of them and output the text. Can you help? Thanks in advance.

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  • java /TableModel of Objects/Update Object"

    - by Tomás Ó Briain
    I've a collection of Stock objects that I'm updating about 10/15 variables for in real-time. I'm accessing each Stock by its ID in the collection. I'm also trying to display this in a JTable and have implemented an AbstractTablemodel. It's not working too well. I've a RowMap that I add each ID to as Stocks are added to the TableModel. To update the prices and variables of all the stocks in the TableModel, I want to send a Stock object to an updateModel(Stock s) method. I can find the relevant row by searching the map, but how do I handle this nicely, so I don't have to start iterating through table columns and comparing the values of the cells to the variables of the object to see whether there are any differences?? Basically, i want to send a Stock object to the TableModel and update cells if there are changes and do nothing if there aren't. Any ideas about how to implement a TableModel that might do this? Any pointeres at all would be appreciated. Thanks.

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  • Java- screen capture behind the application.

    - by Auxiliary
    Is there a way to capture the screen but without the app itself getting shown. I know how to minimize or make a frame invisible but this has to be done real fast cos it's going to happen alot in each second (at least once every second). I want it to look something like the magnifier in Windows Vista/7. (The app can see behind itself.) Thanks in advance.

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  • Java Sound Clip Looping Frame Position

    - by InsertNickHere
    Hi, I have a little problem with a loopting clip: If you have a soundfile e.g. 20000 samples long, the frame position will not reset after looping, so I get values that are "out of bounds" of the original soundfile. As I want to draw a position marker on my waveform, I'm a bit confused how to achive. At this time I just get myClip.getLongFramePosition() but this does not work as described above. Does anyone have an idea how to fix that? Is there a possibility to count how often a clip was looped before? Regards

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  • Connection and Collection Interfaces in Java

    - by Bhupi
    Which class implements all the Connection Interfaces which are in javax.microedition.io package and how? And in the same way which class implements the some of Collection interfaces like Iterator interface. I saw a code: - Iterator it; ArrayList list = new ArrayList(); it = list.iterator(); The iterator() return type is "Iterator" which is an interface. Please tell me what this code is doing is it returning an object of type Iterator? but as far as I know, interface can't be initialized.

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  • Creating a New Reverse Java Array

    - by mandir08
    Given an array of ints length 3, return a new array with the elements in reverse order, so {1, 2, 3} becomes {3, 2, 1}. public int[] reverse3(int[] nums) { int[] values = new int[3]; for(int i=0; i<=nums.length-1; i++) { for(int j=nums.length-1; j>=0; j--) { values[i]=nums[j]; } } return values; } I cant get this to work properly, usually the last int in the array, becomes every single int in the new array

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