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  • Getting a cryptic error on my simple Java program, comparing char[i] to a string.

    - by Sergio Tapia
    public static void ejemplosString(String palabra){ char[] letras = palabra.toCharArray(); int contadorVocales = 0; for (int i = 0; i < letras.length; i++) { if (char[i] == 'a') { contadorVocales++; } if (char[i] == "e") { contadorVocales++; } if (char[i] == "i") { contadorVocales++; } if (char[i] == "o") { contadorVocales++; } if (char[i] == "u") { contadorVocales++; } } } Getting the error on every If statement. Any guidance?

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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 Swing: how to listen to JComboBox's width changes?

    - by agnieszka
    I tried PropertyChangeListener with property set to "width", "Width", "size" and "Size". PropertyChangeListener widthChangeListener = new PropertyChangeListener() { @Override public void propertyChange(PropertyChangeEvent evt) { //code } }; streamsComboBox.addPropertyChangeListener("width", widthChangeListener); projectsComboBox.addPropertyChangeListener("width", widthChangeListener); vobsComboBox.addPropertyChangeListener("width", widthChangeListener); Nothing works - the handler method is never fired. What should I do to handle JComboBox's size change? Where does the property name come from anyway?

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  • OOP App Architecture: Which layer does a lazy loader sit in?

    - by JW
    I am planning the implemention an Inheritance Mapper pattern for an application component http://martinfowler.com/eaaCatalog/inheritanceMappers.html One feature it needs to have is for a domain object to reference a large list of aggreageted items (10,000 other domain objects) So I need some kind of lazy loading collection to be passed out of the aggregate root domain object to other domain objects. To keep my (php) model scripts organised i am storing them in two folders: MyComponent\ controllers\ models\ domain\ <- domain objects, DDD repository, DDD factory daccess\ <- PoEAA data mappers, SQL queries etc views\ But now I am racking my brains wondering where my lazy loading collection sits. Any suggestions / justifications for putting it in one place over another another? DDD = Domain Driven Design Patterns, Eric Evans - book PoEAA = Patterns of Application Architecture Patterns, Martin Fowler - book

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  • Creating lib file from java jar using mingw/gcj

    - by Xinus
    I am trying to convert jar file to native lib file using mingw-gcj under windows platform it is thrown me the error as C:\testDir\libs>gcj -o glassfish-embedded-all-3.1-SNAPSHOT.lib glassfish-embedde d-all-3.1-SNAPSHOT.jar com/sun/codemodel/JAnonymousClass.java: In class 'com.sun.codemodel.JAnonymousCl ass': com/sun/codemodel/JAnonymousClass.java: In constructor '(com.sun.codemodel.JClas s,com.sun.codemodel.JCodeModel)': In file included from com/sun/codemodel/CodeWriter.java:15, from <built-in>:3: com/sun/codemodel/JAnonymousClass.java:21: error: verification failed at PC=3: c onstant pool index out of range com/sun/codemodel/JAnonymousClass.java:21: confused by earlier errors, bailing o ut Is it related to some java 1.6 issue or bug in gcj /

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  • How to (simply) create new service objects in java jax-ws webservices?

    - by cibercitizen1
    Is it possible in jax-ws to have a webmethod that creates a new object (of a service class) and returns a reference to it to the client caller (for the client, it's a remote reference) so that the client and this new service object maintain a session? (Therefore each client is served by a different instance). Schematically: client server o:Session -------- -------- ---------- s = server.access() ------------------> o = new Session() return o <--- o.doSomething() ----------------------------------------------> make it <--- o.doMore() --------------------------------------------------> make it <---

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  • Is this class + constructor definition pattern overly redundant?

    - by Protector one
    I often come across a pattern similar to this: class Person { public string firstName, lastName; public Person(string firstName, string lastName) { this.firstName = firstName; this.lastName = lastName; } } This feels overly redundant (I imagine typing "firstName" once, instead of thrice could be enough…), but I can't think of a proper alternative. Any ideas? Maybe I just don't know about a certain design pattern I should be using here? Edit - I think I need to elaborate a little. I'm not asking how to make the example code "better", but rather, "shorter". In its current state, all member names appear 3 times (declaration, initialization, constructor arguments), and it feels rather redundant. So I'm wondering if there is a pattern (or semantic sugar) to get (roughly) the same behavior, but with less bloat. I apologize for being unclear initially.

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  • Java: how do I get a class literal from a generic type?

    - by Tom
    Typically, I've seen people use the class literal like this: Class<Foo> cls = Foo.class; But what if the type is generic, e.g. List? This works fine, but has a warning since List should be parameterized: Class<List> cls = List.class So why not add a <?>? Well, this causes a type mismatch error: Class<List<?>> cls = List.class I figured something like this would work, but this is just a plain ol' a syntax error: Class<List<Foo>> cls = List<Foo>.class How can I get a Class<List<Foo>> statically, e.g. using the class literal? I could use @SuppressWarnings("unchecked") to get rid of the warnings caused by the non-parameterized use of List in the first example, Class<List> cls = List.class, but I'd rather not. Any suggestions? Thanks!

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  • JAVA: 500 Worker Threads, what kind of thread pool?

    - by Submerged
    I am wondering if this is the best way to do this. I have about 500 threads that run indefinitely, but Thread.sleep for a minute when done one cycle of processing. ExecutorService es = Executors.newFixedThreadPool(list.size()+1); for (int i = 0; i < list.size(); i++) { es.execute(coreAppVector.elementAt(i)); //coreAppVector is a vector of extends thread objects } I do need a separate threads for each running task, so changing the architecture isn't an option. I tried making my threadPool size equal to Runtime.getRuntime().availableProcessors() which attempted to run all 500 threads, but only let 8 (4xhyperthreading) of them execute. The other threads wouldn't surrender and let other threads have their turn. I tried putting in a wait() and notify(), but still no luck. If anyone has a simple example or some tips, I would be grateful!

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  • How do you draw a string centered vertically in Java?

    - by Paul Alexander
    I know it's a simple concept but I'm struggling with the font metrics. Centering horizontally isn't too hard but vertically seems a bit difficult. I've tried using the FontMetrics getAscent, getLeading, getXXXX methods in various combinations but no matter what I've tried the text is always off by a few pixels. Is there a way to measure the exact height of the text so that it is exactly centered.

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  • How can I rotate an image using Java/Swing and then set its origin to 0,0?

    - by JT
    I'm able to rotate an image that has been added to a JLabel. The only problem is that if the height and width are not equal, the rotated image will no longer appear at the JLabel's origin (0,0). Here's what I'm doing. I've also tried using AffineTransform and rotating the image itself, but with the same results. Graphics2D g2d = (Graphics2D)g; g2d.rotate(Math.toRadians(90), image.getWidth()/2, image.getHeight()/2); super.paintComponent(g2d); If I have an image whose width is greater than its height, rotating that image using this method and then painting it will result in the image being painted vertically above the point 0,0, and horizontally to the right of the point 0,0.

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  • Is it bad to explicitly compare against boolean constants e.g. if (b == false) in Java?

    - by polygenelubricants
    Is it bad to write: if (b == false) //... while (b != true) //... Is it always better to instead write: if (!b) //... while (!b) //... Presumably there is no difference in performance (or is there?), but how do you weigh the explicitness, the conciseness, the clarity, the readability, etc between the two? Note: the variable name b is just used as an example, ala foo and bar.

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  • How to fill two-dimensional array using java enhanced loop?

    - by Shark
    Basically, I am trying this, but this only leaves array filled with zeros. I know how to fill it with normal for loop (such as for (int i = 0; i < array.length; i++) and so on), but why is my variant is not working? Any help would be appreciated. char[][] array = new char[x][y]; for (char[] row : array) for (char element : row) element = '~';

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  • How do we simplify this kind of code in Java? Something like macros in C?

    - by Terry Li
    public static boolean diagonals(char[][] b, int row, int col, int l) { int counter = 1; // because we start from the current position char charAtPosition = b[row][col]; int numRows = b.length; int numCols = b[0].length; int topleft = 0; int topright = 0; int bottomleft = 0; int bottomright = 0; for (int i=row-1,j=col-1;i>=0 && j>=0;i--,j--) { if (b[i][j]==charAtPosition) { topleft++; } else { break; } } for (int i=row-1,j=col+1;i>=0 && j<=numCols;i--,j++) { if (b[i][j]==charAtPosition) { topright++; } else { break; } } for (int i=row+1,j=col-1;i<=numRows && j>=0;i++,j--) { if (b[i][j]==charAtPosition) { bottomleft++; } else { break; } } for (int i=row+1,j=col+1;i<=numRows && j<=numCols;i++,j++) { if (b[i][j]==charAtPosition) { bottomright++; } else { break; } } return topleft + bottomright + 1 >= l || topright + bottomleft + 1 >= l; //in this case l is 5 } After I was done posting the code above here, I couldn't help but wanted to simplify the code by merging the four pretty much the same loops into one method. Here's the kind of method I want to have: public int countSteps(char horizontal, char vertical) { } Two parameters horizontal and vertical can be either + or - to indicate the four directions to walk in. What I want to see if possible at all is i++; is generalized to i horizontal horizontal; when horizontal taking the value of +. What I don't want to see is if or switch statements, for example: public int countSteps(char horizontal, char vertical) { if (horizontal == '+' && vertical == '-') { for (int i=row-1,j=col+1;i>=0 && j<=numCols;i--,j++) { if (b[i][j]==charAtPosition) { topright++; } else { break; } } } else if (horizontal == '+' && vertical == '+') { for (int i=row+1,j=col+1;i>=0 && j<=numCols;i++,j++) { if (b[i][j]==charAtPosition) { topright++; } else { break; } } } else if () { } else { } } Since it is as tedious as the original one. Note also that the comparing signs for the loop condition i>=0 && j<=numCols; for example, >= && <= have correspondence with the value combination of horizontal and vertical. Sorry for my bad wording, please let me know if anything is not clear.

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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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  • 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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