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  • When does the call() method get called in a Java Executor using Callable objects?

    - by MalcomTucker
    This is some sample code from an example. What I need to know is when call() gets called on the callable? What triggers it? public class CallableExample { public static class WordLengthCallable implements Callable { private String word; public WordLengthCallable(String word) { this.word = word; } public Integer call() { return Integer.valueOf(word.length()); } } public static void main(String args[]) throws Exception { ExecutorService pool = Executors.newFixedThreadPool(3); Set<Future<Integer>> set = new HashSet<Future<Integer>>(); for (String word: args) { Callable<Integer> callable = new WordLengthCallable(word); Future<Integer> future = pool.submit(callable); //**DOES THIS CALL call()?** set.add(future); } int sum = 0; for (Future<Integer> future : set) { sum += future.get();//**OR DOES THIS CALL call()?** } System.out.printf("The sum of lengths is %s%n", sum); System.exit(sum); } }

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  • Java - Adding a Node in a doubly-linked list.

    - by jacobnlsn
    Hi, I am working on some code were I need to add a Node into a doubly linked-list, this is the code I have so far: Node tempNext = cursor.getNext(); temp = new Node(item, null, cursor, tempNext); tempNext.setPrev(temp); cursor is the Node that is right before the new added Node should go.

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  • how to read data from file into array? java

    - by lox
    I need some help reading data from a txt file into my ArrayList. I know the code is pretty messy, but just try to take a look at it. The first part with the creating and putting the ArrayList into the txt file works perfectly. I just need some help at the end in the "marked" area. Sorry if I still have some words in my native language, but I didn't really had the time to translate everything. public class ContAngajat { String username; String password; } public class CreazaCont { // creating the arraylist and putting it into a file public static void ang(String args[]) { ArrayList<ContAngajat> angajati=new ArrayList<ContAngajat>(50); Scanner diskScanner = new Scanner(in); Scanner forn = new Scanner(in); int n; out.print("Introduceti numarul de conturi noi care doriti sa le introduceti: "); n=forn.nextInt(); out.println(); try{ FileWriter fw = new FileWriter("ConturiAngajati.txt", true); for(int i=0; i<n; i++){ ContAngajat cont = new ContAngajat(); out.print("Username: "); cont.username=diskScanner.nextLine(); out.print("Password: "); cont.password=diskScanner.nextLine(); angajati.add(cont); fw.write(cont.username + " "); fw.write(cont.password +"|"); } fw.close(); } catch(IOException ex){ System.out.println("Could not write to file"); System.exit(0); } for (int i=0; i<n; i++) { out.println("username: " + angajati.get(i).username + " password: " +angajati.get(i).password ); } } // HERE I'M TRING TO GET THE ARRAYLIST OUT OF THE FILE public static void RdAng(String args[]) { ArrayList<ContAngajat> angajati=new ArrayList<ContAngajat>(50); ContAngajat cont = new ContAngajat(); int count,i2,i; try{ FileReader fr = new FileReader("ConturiAngajati.txt"); BufferedReader br = new BufferedReader(fr); String line = ""; while((line=br.readLine())!=null) { String[] theline=line.split("|"); count=theline.length; for(i=0;i<theline.length;i++) { String[] theword = theline[i].split(" "); } } for(i2=0;i2<count;i2++) { ContAngajat contrd = new ContAngajat(); // "ERROR" OVER HERE for (int ird=0; ird <theword.length; ird++) { cont.username=theword[0]; cont.password=theword[1]; // they keep telling me "theword cannot be resolved" whenever i try to run this } angajati.add(contrd); } } catch(IOException ex){ System.out.println("Could not read to file"); System.exit(0); } } }

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  • Can anyone help with java? Finding common nodes from two linked lists using recursion

    - by Dan
    I have to write a method that returns a linked list with all the nodes that are common to two linked lists using recursion, without loops. For example, first list is 2 - 5 - 7 - 10 second list is 2 - 4 - 8 - 10 the list that would be returned is 2 - 10 I am getting nowhere with this.. What I have been think of was to check each value of the first list with each value of the second list recursively but the second list would then be cut by one node everytime and I cannot compare the next value in the first list with the the second list. I hope this makes sense... Can anyone help?

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  • Java: Selected rows's index does not changes when I sort them!

    - by adrian7
    Hello, I have a Jtable on which I called the method table1.setAutoCreateRowSorter(true);. So this works on well. But I also have a methos in my JFrame class which is fired when i push a button. It gets the selected rows indexes using this code int selectedRows[] = this.table1.getSelectedRows();. And displays an edit window for the first row corresponding in the selected interval. The problem is that if I don't click on column's headers (I mean i don't sorte them at all) my method works perfect. But when I sort the row, the indexes of the rows doesn't seems to change at all - thus resulting an edit window for the old row whicn was initially in that position before making any sort. I am using JDK 6 could anyonw give ma a tip?

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  • Java IDE - find all INDIRECT usages/references of a function or class?

    - by GreenieMeanie
    In Netbeans or in Eclipse, you can use "Find Usages" or "References" from the right click context menu. If a() calls b(), using the functionality from b() will show you a(). However, what I want is to be able to see some kind of tree or have an option to see all usages of a given/class or method, such that if z() calls a() that using the functionality will show both z() and a(). Any IDE plugins or external tools that can do this?

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  • Is there anything inherently wrong with long variable/method names in Java?

    - by Doug Smith
    I know this is probably is a question of personal opinion, but I want to know what's standard practice and what would be frowned upon. One of my profs in university always seems to make his variable and method names as short as possible (getAmt() instead of getAmount) for instance. I have no objection to this, but personally, I prefer to have mine a little longer if it adds descriptiveness so the person reading it won't have to check or refer to documentation. For instance, we made a method that given a list of players, returns the player who scored the most goals. I made the method getPlayerWithMostGoals(), is this wrong? I toiled over choosing a way to make it shorter for awhile, but then I thought "why?". It gets the point across clearly and Eclipse makes it easy to autocomplete it when I type. I'm just wondering if the short variable names are a piece of the past due to needing everything to be as small as possible to be efficient. Is this still a requirement?

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  • How to properly clean up JDBC resources in Java?

    - by user523086
    What is considered best practices when cleaning up JDBC resources and why? I kept the example short, thus just the cleaning up of the ResultSet. finally { if(rs != null) try{ rs.close(); } catch(SQLException ignored) {} } versus finally { try{ rs.close(); } catch(Exception ignored) {} } Personally I favour the second option since it is a bit shorter. Any input on this is much appreciated.

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  • Where should i save my images that user uploads? java web application

    - by Nitesh Panchal
    Hello, I am saving the image at this location :- private static String photoGalleryPath = "/Common/PhotoGallery/"; In PhotoGallery. I create userid wise folders and save images. Everything works fine. But when i clean and build my project. The whole folder of PhotoGallery gets deleted. This looks very funny to me :). Why does it delete my whole folder everytime? And what more should i do to tell the extra smart Glassfish to not to delete my folders?

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  • Is there a a C-like way to get item number from enum in java ?

    - by Hernán Eche
    Perhap this is a simple basic question Having an enum public enum TK{ ID,GROUP,DATA,FAIL; } Can I get the order number for example ID=0, GROUP=2, DATA=3, FAIL=4 ? This is a way to to that, but a weird and long one! =S public enum TK{ ID(0),GROUP(1),DATA(2),FAIL(3); int num; TK(int n) { this.num=n; } public int get() { return num; } }; to get numbers so I write TK.ID.get(), TK.GROUP.get(), etc... I don't like that there is a better way? ( C enums, C macros..I miss you both ) thanks

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  • Array inside of Arrays; Java (Help with Lab Assignment)

    - by Adam
    We are working on a lab assignment for my CS&E class and I think I can ask this question without going into detail of the entire lab requirements, but is it possible for an array to be inside of an array? For example, would this work: int [] arrayOne = new int[3]; arrayOne[0] = Start of an array If this is possible how do you go about doing it?

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  • Lazy loading? Better avoiding it?

    - by Charlie Pigarelli
    I just read about this design pattern: Lazy Load. And, since in the application i'm working on i have all the classes in one folder, i was wondering if this pattern could just make me avoiding the include() function for every class. I mean: It's nice to know that if i forgot to include a class, PHP, before falling into an error, trough an __autoload() function try to get it. But is it fine enough to just don't care about including classes and let PHP do it by your own every time? Or we should write __autoload() just in case it is needed?

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  • Spring Jdbc Template + MySQL = TransientDataAccessResourceException : Invalid Argument Value : Java.

    - by Vanchinathan
    I was using spring jdbc template to insert some data into the database and I was getting this error. Here is my code : JdbcTemplate insert = new JdbcTemplate(dataSource); for(ResultType result : response.getResultSet().getResult()) { Object[] args = new Object[] {result.getAddress(), result.getCity(), result.getState(), result.getPhone(), result.getLatitude(), result.getLongitude(),result.getRating().getAverageRating(), result.getRating().getAverageRating(), result.getRating().getTotalRatings(), result.getRating().getTotalReviews(), result.getRating().getLastReviewDate(), result.getRating().getLastReviewIntro(), result.getDistance(), result.getUrl(), result.getClickUrl(), result.getBusinessUrl(), result.getBusinessClickUrl()}; insert.update("INSERT INTO data.carwashes ( address, city, state, phone, lat, lng, rating, average_rating, total_ratings, total reviews, last_review_date, last_review_intro, distance, url, click_url, business_url, business_click_url, category_id, zipcode_id) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?,96925724,78701)", args); } Quite lengthy code.. but, basically it gets the value from a object and sticks it to a array and passed that array to insert method of jdbc template. Any help will be appreciated.

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  • Avoid an "out of memory error" in Java(eclipse), when using large data structure?

    - by gnomed
    OK, so I am writing a program that unfortunately needs to use a huge data structure to complete its work, but it is failing with a "out of memory error" during its initialization. While I understand entirely what that means and why it is a problem, I am having trouble overcoming it, since my program needs to use this large structure and I don't know any other way to store it. The program first indexes a large corpus of text files that I provide. This works fine. Then it uses this index to initialize a large 2D array. This array will have nXn entries, where "n" is the number of unique words in the corpus of text. For the relatively small chunk I am testing it on(about 60 files) it needs to make approximately 30,000x30,000 entries. this will probably be bigger once I run it on my full intended corpus too. It consistently fails every time, after it indexes, while it is initializing the data structure(to be worked on later). Things I have done include: revamp my code to use a primitive "int[]" instead of a "TreeMap" eliminate redundant structures, etc... Also, I have run eclipse with "eclipse -vmargs -Xmx2g" to max out my allocated memory I am fairly confident this is not going to be a simple line of code solution, but is most likely going to require a very new approach. I am looking for what that approach is, any ideas? Thanks, B.

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