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  • Efficient implementation of exclusive execution

    - by n0weak
    I have an ObjectManager class that is used to process payments. It is wrapped over the Order entities, so new instance has to be created when processing is required. I need to prevent the situation when several ObjectManager instances are dealing with the same order simultaneously (it happend once because of some errors on the remote payment processing center, somehow they called our callback urls twice). I'd love to get an advice how to implement it more efficiently. For now, I am thinking about something like that: public class OrderManager{ private static final CopyOnWriteArrayList<Integer> LOCKER = new CopyOnWriteArrayList<Integer>(); private static synchronized boolean tryLock(Integer key) { return LOCKER.addIfAbsent(key); } private static void releaseLock(Integer key) { LOCKER.remove(key); } public void processPayment(Integer orderId) throws Exception{ if (!tryLock(orderId)) { return; } try { //operate } finally { releaseLock(orderId); } } //remainder omitted }

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  • JDBC delete statement with multiple columns

    - by user1643033
    It says I ended this statement wrong when if I input it into sql plus with just the addition of ; it works perfectly. What am I doing wrong? Statement statement = connection.createStatement(); statement.executeUpdate("delete from aplbuk MODEL = '"+ textField_4.getText() + "'AND year = '" + textField_1.getText() + "' AND Litres = '" + textField_2.getText() + "' AND ENGINE_TYPE = '" + textField_3.getText() + "'"); statement.close();

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  • programming help

    - by user208639
    class Person holds personal data Its constructor receives 3 parameters, two Strings representing first and last names and an int representing age public Person(String firstName, String lastName, int age) { its method getName has no parameters and returns a String with format "Lastname, Firstname" its method getAge takes no parameters and returns an int representing the current age its method birthday increases age value by 1 and returns the new age value Create the class Person and paste the whole class into the textbox below public class Person { public Person(String first, String last, int age) { getName = "Lastname, Firstname"; System.out.print(last + first); getAge = age + 1; return getAge; System.out.print(getAge); birthday = age + 1; newAge = birthday; return newAge; } } im getting errors such as "cannot find symbol - variable getName" but when i declare a variable it still not working, i also wanted to ask if i am heading in the right direction or is it all totally wrong? im using a program called BlueJ to work on.

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  • How do I compare a string in an array to a string?

    - by user1641312
    EDIT: IT'S FIXED, THANKS FOR THE HELP! So basically I have an array of strings, a question and an answer public static String[][] triviaData = { {"Question2", "Answer1"}, {"Question2", "Answer2"}, {"Question3", "Answer3"}, }; And I am trying to make a method that validates an entered input, lets call the entered input enteredAnswer. enteredAnswer is stored as a String. I am trying to validate that the enteredAnswer is the same as the second index of the array. if (enteredAnswer.equalsIgnoreCase(triviaData[Config.CurrentQuestion][1])) { This is the code I tried, but I get the error "Cannot invoke equalsIgnoreCase(String) on the array type String[]" I am a beginner programmer so if you could help me out it would be highly appreciated. Thanks. enteredAnswer is stored as public String[] enteredAnswer;

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  • jQuery & elastic Problem

    - by Fincha
    Hello eveyone, i using elastic in my script. I have also jQuery Tabs (every will be get over AJAX and content a textarea) and a timer for Saving content all 3 minutes. So some JS code... I have 2 parts on my site, left and right. On the right side i have 2 tabs (jQuery not AJAX) with each one textarea. And Left side between 5-10 Textareas each in Tab but they gonna be loaded only if Tab is activ (AJAX). my Problem is: If i paste a lot of text in a Textarea (1000 characters) the writing get slowed, not fluid, jerky. It ist 100% the elastic problem, without elastic there no Problem while writing. Have some one an idea for the solution of this Porblem? Is it Overload?

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  • Column moved [finished] event in JTable

    - by chown
    How should I detect that column moved action is finished in JTable? I've added columnModeListener to my column model but the problem is columnMoved method is called every time a column moves (by certain pixels). I don't want this behavior. I just want to detect when the column dragging is finished. columnModel.addColumnModelListener(new TableColumnModelListener() { public void columnAdded(TableColumnModelEvent e) { } public void columnRemoved(TableColumnModelEvent e) { } public void columnMoved(TableColumnModelEvent e) { //this is called so many times //I don't want this, but something like column moved finished event System.out.println("Moved "+e.getFromIndex()+", "+e.getToIndex()); } public void columnMarginChanged(ChangeEvent e) { } public void columnSelectionChanged(ListSelectionEvent e) { } }); I hope it is clear what I'm looking for. Thanks.

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  • Find out the Mac address!!

    - by pirates-iiita
    hello everyone, Can anyone please tell the way to find out the mac address of a system which is: 1. Shutdown 2. Power plugged in 3. Connected to Lan 4. Nic card ON. Kindly post the solution as i urgently need it in my project... thank you

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  • trying to switch beginning of an array with another

    - by user1874574
    I have a problem where i am trying to swap two arrays so that they switch beginnings. example: array 1 = (1,2,3,4,5,6,7,8) and array 2 = (11,12,13,14,15,16,17,18) i want to end up with the first array being (11,12,13,14,5,6,7,8) and i want the second array to be (1,2,3,4,15,16,17,18) but for some reason i end up with 1=(11,12,13,14,5,6,7,8) and 2=(11,12,13,14,15,16,17,18) my code is provided below, what am i doing wrong? public static void Mutate(Genetic lowest, Genetic secondLowest) { int halfway = (lowest.getPopulation().length)/2; int[] one = lowest.getPopulation(); int[] two = secondLowest.getPopulation(); int[] temp = secondLowest.getPopulation(); int[] temp2 = lowest.getPopulation(); for(int i = 0; i < halfway; i++){ temp[i] = one[i]; } lowest.setPopulation(temp); for(int i = 0; i < lowest.getPopulation().length; i++){ System.out.print(temp[i]); } System.out.println(); for(int i = 0; i < halfway; i++){ temp2[i] = two[i]; } for(int i = 0; i < lowest.getPopulation().length; i++){ System.out.print(temp2[i]); } }

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  • regarding object recycling

    - by ajaycv
    I have a question. What is wrong with regards to the below code: ArrayList tempList2 = new ArrayList(); tempList2 = getXYZ(tempList1, tempList2); //method getXYZ getXYZ(ArrayList tempList1, ArrayList tempList2) { //does some logic and adds objects into tempList2 return tempList2; } The code will get executed but it seems by passing tempList2 to the getXYZ method argument, it is doing object recycling. My question is, Is recycling the tempList2 arraylist object correct?

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  • Enumerate all k-partitions of 1d array with N elements?

    - by user301217
    This seems like a simple request, but google is not my friend because "partition" scores a bunch of hits in database and filesystem space. I need to enumerate all partitions of an array of N values (N is constant) into k sub-arrays. The sub-arrays are just that - a starting index and ending index. The overall order of the original array will be preserved. For example, with N=4 and k=2: [ | a b c d ] (0, 4) [ a | b c d ] (1, 3) [ a b | c d ] (2, 2) [ a b c | d ] (3, 1) [ a b c d | ] (4, 0) I'm pretty sure this isn't an original problem (and no, it's not homework), but I'd like to do it for every k <= N, and it'd be great if the later passes (as k grows) took advantage of earlier results. If you've got a link, please share.

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  • How do I create new variables based on the size of a List?

    - by GK
    I have a List with say size n, and i have to dynamically create n variables ie i want to dynamically create the variables depending upon the size of the list. How can i achieve this? Say i have List as List year with n elements in it; then i have to create the n Integer variables from the above list. thanks.

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  • Similar Sub-Classes

    - by praks5432
    Lets say I have a class A that is fairly simple like this - public class A{ private int randomField = 0; protected int key; protected double dmg; } Now I want to write a number of sub-classes that inherit the protected fields and only differ based on the initial values that are assigned to those fields - for example, if I wrote two subclasses B and C, the only difference between those two sub-classes would be that the values key and dmg would have different values. They would share a method, set, which would be exactly the same, in that it would affect the same variable. I find when I'm writing these sub-classes I'm repeating myself, as I just change the constructor to set different initial values to key and dmg, and simply copy and paste the set method. Is there a 'good' way to do this?

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  • getting panel color

    - by user161004
    I have a program where i have a button to change the background color to red and another button to set back the default panel color. How do i get back the default color for panel??

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  • Android ArrayList Calendar add and get is different

    - by Raku ShinShou
    I put increment date of the calendar and add into arraylist, but when i loop them out, the date is all same. Calendar a = Calendar.getInstance(); ArrayList<Calendar> b = new ArrayList<Calendar>(); for (int i=0; i<3; i++) { a.add(Calendar.DATE, i>0 ? 1 : 0); b.add(a); } for (int i=0; i<b.size(); i++){ Log.d("xxx", "test=" + b.get(i)); } suppose i wan 10/11/2012, 11/11/2012, 12/11/2012 but it come out like 12/11/2012, 12/11/2012, 12/11/2012 Anyone know how to solve this?

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  • bashscript for file search and replace!

    - by D3orn
    Hey I try to write a littel bash script. This should copy a dir and all files in it. Then it should search each file and dir in this copied dir for a String (e.g @ForTestingOnly) and then this save the line number. Then it should go on and count each { and } as soon as the number is equals it should save againg the line number. = it should delete all the lines between this 2 numbers. I'm trying to make a script which searchs for all this annotations and then delete the method which is directly after this ano. Thx for help...

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