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  • Shortcut for adding to List in a HashMap

    - by Damo
    I often have a need to take a list of objects and group them into a Map based on a value contained in the object. Eg. take a list of Users and group by Country. My code for this usually looks like: Map<String, List<User>> usersByCountry = new HashMap<String, List<User>>(); for(User user : listOfUsers) { if(usersByCountry.containsKey(user.getCountry())) { //Add to existing list usersByCountry.get(user.getCountry()).add(user); } else { //Create new list List<User> users = new ArrayList<User>(1); users.add(user); usersByCountry.put(user.getCountry(), users); } } However I can't help thinking that this is awkward and some guru has a better approach. The closest I can see so far is the MultiMap from Google Collections. Are there any standard approaches? Thanks!

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  • JDO in Google App Engine: order of keys in unowned one-to-many relationship

    - by Kel
    I'm implementing web application with JDO in Google App Engine. According to documentation, in owned one-to-many relationships, order of elements in "owner" object collection is determined either by automatically created index field, or by information given in explicit ordering clause. For example: @PersistenceCapable public class Person { // ... @Order(extensions = @Extension(vendorName="datanucleus", key="list-ordering", value="country asc, city asc")) private List<ContactInfo> contacts = new List<ContactInfo>(); In unowned relationships, "owner" object contains collection of keys of "nested" objects, for example: @PersistenceCapable public class Author { // ... @Persistent private List<Key> books; Is order of keys preserved, if I use List<Key> collection in "owner" object for storing keys of "nested" elements? I could not find answer neither in JDO relationships article, nor in Data Classes article :(

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  • Relation many-to-many with attributes : how ?

    - by mada
    Hi, Excuse me for my poor english in advance as it is not my mother tongue. Like in this example: http://www.xylax.net/hibernate/manytomany.html But i have in the table foo-bar 2 attributes which are not part of the primary or foreign keys.: one boolean(A) & one string(B). I know how to map it without attributes but not in this case. I have not found an answer in the documentation. I need to know please how to map it & what kind of collection i have to declare in my class Foo. Thanks in advance for your answer. I really appreciate the time given by you.

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  • Anyone know exactly which JMS messages will be redelivered in CLIENT_ACKNOWLEDGE mode if the client

    - by user360612
    The spec says "Acknowledging a consumed message automatically acknowledges the receipt of all messages that have been delivered by its session" - but what I need to know is what it means by 'delivered'. For example, if I call consumer.receive() 6 times, and then call .acknowledge on the 3rd message - is it (a) just the first 3 messages that are ack'd, or (b) all 6? I'm really hoping it's option a, i.e. messages after the one you called acknowledge on WILL be redelivered, otherwise it's hard to see how you could prevent message lost in the event of my receiver process crashing before I've had a chance to persist and acknowledge the messages. But the spec is worded such that it's not clear. I get the impression the authors of the JMS spec considered broker failure, but didn't spend too long thinking about how to protect against client failure :o( Anyway, I've been able to test with SonicMQ and found that it implements (a), i.e. messages 'received' later than the message you call .ack on DO get redelivered in the event of a crash, but I'd love to know how other people read the standard, and if anyone knows how any other providers have implemented CLIENT_ACKNOWLEDGE? (i.e. what the 'de facto' standard is) Thanks Ben

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  • How to deserialize implementation classes in OSGi

    - by Daniel Schneller
    In an eRCP OSGi based application the user can push a button and go to a lock screen similar to that of Windows or Mac OS X. When this happens, the current state of the application is serialized to a file and control is handed over to the lock screen. In this mobile application memory is very tight, so we need to get rid of the original view/controller when the lock screen comes up. This works fine and we end up with a binary serialized file. Once the user logs back in, the file is read in again and the original state of the application restored. This works fine as well, except when the controller that was serialized contained a reference to an object which comes from a different bundle. In my concrete case the original controller (from bundle A) can call a web service and gets a result back. Nothing fancy, just some Strings and Numbers in a simple value holder class. However the controller only sees this as a Result interface; the actual runtime object (ResultImpl) is defined and created in a different bundle (bundle B, the webservice client implementation) and returned via a service call. When the deserialization now tries to thaw the controller from the file, it throws a ClassNotFound exception, complaining about not being able to deserialize the result object, because deserialization is called from bundle A, which cannot see the ResultImpl class from bundle B. Any ideas on how to work around that? The only thing I could come up with is to clone all the individual values into another object, defined in the controller's bundle, but this seems like quite a hassle.

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  • Entities equals(), hashCode() and toString(). How to correctly implement them?

    - by spike07
    I'm implementing equals(), hashCode() and toString() of my entities using all the available fields in the bean. I'm getting some Lazy init Exception on the frontend when I try to compare the equality or when I print the obj state. That's because some list in the entity can be lazy initialized. I'm wondering what's the correct way to for implementing equals() and toString() on an entity object.

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  • writing large excel spreadsheets

    - by pstanton
    has anybody found a library that works well with large spreadsheets? I've tried apache's POI but it fails miserably working with large files - both reading and writing. It uses massive amounts of memory leaving you needing a supercomputer to parse or create a 20+mb spreadsheet. Surely there is a more memory efficient way and someone has written it?!

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  • Detecting struckout text in a cell using JExcelApi

    - by Geo
    I need to detect whether the text within a cell is struck out or not. I'm using this: Cell cc = sheet.getCell("B1"); CellFormat format = cc.getCellFormat(); System.out.println(format.getFont().isStruckout()); but I remember I read somewhere that CellFormat is deprecated and CellFeatures should be used instead. How could one find out whether a text is struck out using CellFeatures?

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  • How can I change GWT's widget CSS values?

    - by Xorty
    Basically, I like default theme widgets. However, I need to change font size on DecoratedStackPanel widget. I think it should be possible with something like this: decoratedStackPanel.getElement().getStyle().setProperty("fontSize", "12pt"); However, "fontSize" is not valid name for property and I didn't find way how to get all element's properties. Therefore, I don't know correct property name. Any ideas? Please, don't post about inheriting widget or writing custom CSS. I like default one but the font size. This should be possible afaik.

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  • Add 'expand' button to JTree node that has no children?

    - by thedude19
    I'd like to add the 'expand' button to my JTree's nodes to indicate that they are expandable. The catch is that they have no children until the user clicks on them (due to processing that happens in the background). Is there any way I can set a node as a parent or having children without it actually having children? Thanks

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  • non-servlet JSP

    - by h2g2java
    I realise there are EL and near EL frameworks like StringTemplate, JUEL, Velocity, etc. However, I am not asking for list of alternatives to JSTL/EL. I came across a package more than a year ago, someone who wrote a util that emulates the functionality of JSP for non-servlet env, i.e., JSP composition which does not need a "servlet container" to function. I ignored it and now I think it would be helpful to me and I need help to recall what it is. My actual motivation is similar to what StringTemplate, JUEL, Velocity would offer to help me compose SQL blocks, HTML blocks but I am thinking that JSPs are precompiled into bytecode and JSPs are more run-time efficient since run-time parsing is done no more than once. So actually, recommendation for alternatives would be acceptable as long as the templates are precompiled into bytecode. But I still prefer the JSP emulator.

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  • Draw a Image on FullScreen mode Android

    - by Marcos Vasconcelos
    Hi, I already know how to get my Activity as fullscreen on Android, now I need to draw a Image in this screen. This is my XML layout. <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <ImageView android:id="@+id/image01" android:layout_width="fill_parent" android:layout_height="fill_parent" /> </LinearLayout> This image is dynamic generated and drawed in the ImageView. This is my code on my Activity. public void onCreate(Bundle savedInstance) { super.onCreate(savedInstance); requestWindowFeature(Window.FEATURE_NO_TITLE); getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN); setContentView(R.layout.main); } But when running, the Activity is FullScreen, but the ImageView is adjusted in the center. What's wrong?

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  • Maven profile properties are not "overriding"

    - by Nazar
    I have Maven multi-module project with such structure: parent-pom-project -- module1 -- module2 At the parent-pom-project I have such pom.xml <modules> <module>module1</module> </modules> ... <profiles> <profile> <id>local</id> <properties> <prop>local_prop</prop> </properties> </profile> <profile> <id>test</id> <modules> <module>module2</module> </modules> <properties> <prop>test_prop</prop> </properties> </profile> </profiles> At all pom.xml files I have such tag: <build> <resources> <resource> <directory>src/main/resources</directory> <filtering>true</filtering> </resource> <resource> <directory>src/test/resources</directory> <filtering>true</filtering> </resource> </resources> </build> At module1 and module2 in resource directory I have properties files with such text: prop=${prop} The problem is that after mvn clean install or mvn clean install -Ptest or even mvn clean install -P test I get prop=local_prop If I user test profile for build module2 is also builded, but properties are used from local profile. I use Maven 3.0.3. Anybody have any ideas?

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  • jaxb entity print out as xml

    - by Cristian Boariu
    Hi, I have a class, let's say User adnotated with @XmlRootElement, with some properties (name, surname etc). I use this class for REST operations, as application/xml. The client will POST User class so i want to keep the values in the log. Is there any method in jax-ws to prints out this object as xml? For instance: log.info("Customers sent a USER"+user.whichMethod()); Customer sent a User <user> <name>cristi</name> <surname>kevin</surname> </user> Thanks.

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  • Debugging stack data not assigned to a named variable

    - by gibbss
    Is there a way to view stack elements like un-assigned return values or exceptions that not assigned to a local variable? (e.g. throw new ...) For example, suppose I have code along the lines of: public String foo(InputStream in) throws IOException { NastyObj obj = null; try { obj = new NastyObj(in); return (obj.read()); } finally { if (obj != null) obj.close(); } } Is there any way to view the return or exception value without stepping to a higher level frame where it is assigned? This is particularly relevant with exceptions because you often have to step back up through a number of frames to find an actual handler. I usually use the Eclipse debugging environment, but any answer is appreciated. Also, if this cannot be done, can you explain why? (JVM, JPDA limitation?)

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  • Help in J2ME for creating image and parse it

    - by HAMED
    Can anyone tell me how i can parse a png image into many png images in J2ME??? for examole:I just wnat to have a source image 150*150 pixel and parse it to 10 image with 15*15 pixel. I write an elemantary code that have exeption. This is my code: public class HelloMIDlet extends MIDlet implements CommandListener { private boolean midletPaused = false; private Command exitCommand; private Form form; private StringItem stringItem; Image im , im2; Form form1 = null; public HelloMIDlet() { try { // create source image im = Image.createImage("/image1.JPG"); int height = im.getHeight() ; int width = im.getWidth() ; int x = 0 ; int y = 0 ; while ( y < height ){ while ( x < width ){ // create 15*15 pixel of source image im2 = im.createImage(im, x, y, 15, 15, Sprite.TRANS_NONE) ; x += 15 ; } y += 15 ; x = 0 ; } } catch (IOException ex) { ex.printStackTrace(); } } please help me to make it right....It's emergency! Thanks a lot guys...

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  • Running junit tests in parallel ?

    - by krosenvold
    I'm using junit 4.4 and maven and I have a large number of long-running integration tests. When it comes to parallellizing test suites there are a few solutions that allow me to run each test method in a single test-class in parallel. But all of these require that I change the tests in one way or another. I really think it would be a much cleaner solution to run X different test classes in X threads in parallel. I have hundreds of tests so I don't really care about threading individual test-classes. Is there any way to do this ?

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  • How can I make a family of singletons?

    - by Jay
    I want to create a set of classes that share a lot of common behavior. Of course in OOP when you think that you automatically think "abstract class with subclasses". But among the things I want these classes to do is to each have a static list of instances of the class. The list should function as sort of a singleton within the class. I mean each of the sub-classes has a singleton, not that they share one. "Singleton" to that subclass, not a true singleton. But if it's a static, how can I inherit it? Of course code like this won't work: public abstract A { static List<A> myList; public static List getList() { if (myList==null) myList=new ArrayList<A>(10); return myList; } public static A getSomethingFromList() { List listInstance=getList(); ... do stuff with list ... } public int getSomethingFromA() { ... regular code acting against current instance ... } } public class A1 extends A { ... } public class A2 extends A { ... } A1 somethingfromA1List=(A1) A1.getSomethingFromList(); A2 somethingfromA2List=(A2) A2.getSomethingFromList(); The contents of the list for each subclass would be different, but all the code to work on the lists would be the same. The problem with the above code is that I'd only have one list for all the subclasses, and I want one for each. Yes, I could replicate the code to declare the static list in each of the subclasses, but then I'd also have to replicate all the code that adds to the lists and searches the list, etc, which rather defeats the purpose of subclassing. Any ideas on how to do this without replicating code?

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  • Accessing global variable in multithreaded Tomcat server

    - by jwegan
    I have a singleton object that I construct like thus: private static volatile KeyMapper mapper = null; public static KeyMapper getMapper() { if(mapper == null) { synchronized(Utils.class) { if(mapper == null) { mapper = new LocalMemoryMapper(); } } } return mapper; } The class KeyMapper is basically a synchronized wrapper to HashMap with only two functions, one to add a mapping and one to remove a mapping. When running in Tomcat 6.24 on my 32bit Windows machine everything works fine. However when running on a 64 bit Linux machine (CentOS 5.4 with OpenJDK 1.6.0-b09) I add one mapping and print out the size of the HashMap used by KeyMapper to verify the mapping got added (i.e. verify size = 1). Then I try to retrieve the mapping with another request and I keep getting null and when I checked the size of the HashMap it was 0. I'm confident the mapping isn't accidentally being removed since I've commented out all calls to remove (and I don't use clear or any other mutators, just get and put). The requests are going through Tomcat 6.24 (configured to use 200 threads with a minimum of 4 threads) and I passed -Xnoclassgc to the jvm to ensure the class isn't inadvertently getting garbage collected (jvm is also running in -server mode). I also added a finalize method to KeyMapper to print to stderr if it ever gets garbage collected to verify that it wasn't being garbage collected. I'm at my wits end and I can't figure out why one minute the entry in HashMap is there and the next it isn't :(

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  • getPackage() returning null when my JUnit test is run from Ant

    - by philharvey
    I'm having problems running a JUnit test. It runs fine in Eclipse, but now I'm trying to run it from the command-line using Ant. The problem is that the following code is returning null: getClass().getPackage(). I'm running my JUnit test like so: <junit fork="no" printsummary="yes" haltonfailure="no"> <classpath refid="junit.classpath" /> <batchtest fork="yes" todir="${reports.junit}"> <fileset dir="${junit.classdir}"> <include name="**/FileHttpServerTest.class" /> <exclude name="**/*$*" /> </fileset> </batchtest> <formatter type="xml" /> ... I Googled for this sort of error, and found a number of references to classloader misbehaviour. But I've found nothing gave me enough information to solve my problem. I really need getClass().getPackage() to not return null. Can anyone help me? Thanks, Phil

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  • Connection hangs after time of inactivity

    - by Sinuhe
    In my application, Spring manages connection pool for database access. Hibernate uses these connections for its queries. At first glance, I have no problems with the pool: it works correctly with concurrent clients and a pool with only one connection. I can execute a lot of queries, so I think that I (or Spring) don't leave open connections. My problem appears after some time of inactivity (sometimes 30 minutes, sometimes more than 2 hours). Then, when Hibernate does some search, it lasts too much. Setting log4j level to TRACE, I get this logs: ... 18:27:01 DEBUG nsactionSynchronizationManager - Retrieved value [org.springframework.orm.hibernate3.SessionHolder@99abd7] for key [org.hibernate.impl.SessionFactoryImpl@7d2897] bound to thread [http-8080-Processor24] 18:27:01 DEBUG HibernateTransactionManager - Found thread-bound Session [org.hibernate.impl.SessionImpl@8878cd] for Hibernate transaction 18:27:01 DEBUG HibernateTransactionManager - Using transaction object [org.springframework.orm.hibernate3.HibernateTransactionManager$HibernateTransactionObject@1b2ffee] 18:27:01 DEBUG HibernateTransactionManager - Creating new transaction with name [com.acjoventut.service.GenericManager.findByExample]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT 18:27:01 DEBUG HibernateTransactionManager - Preparing JDBC Connection of Hibernate Session [org.hibernate.impl.SessionImpl@8878cd] 18:27:01 TRACE SessionImpl - setting flush mode to: AUTO 18:27:01 DEBUG JDBCTransaction - begin 18:27:01 DEBUG ConnectionManager - opening JDBC connection Here it gets frozen for about 2 - 10 minutes. But then continues: 18:30:11 DEBUG JDBCTransaction - current autocommit status: true 18:30:11 DEBUG JDBCTransaction - disabling autocommit 18:30:11 TRACE JDBCContext - after transaction begin 18:30:11 DEBUG HibernateTransactionManager - Exposing Hibernate transaction as JDBC transaction [jdbc:oracle:thin:@212.31.39.50:30998:orcl, UserName=DEVELOP, Oracle JDBC driver] 18:30:11 DEBUG nsactionSynchronizationManager - Bound value [org.springframework.jdbc.datasource.ConnectionHolder@843a9d] for key [org.apache.commons.dbcp.BasicDataSource@7745fd] to thread [http-8080-Processor24] 18:30:11 DEBUG nsactionSynchronizationManager - Initializing transaction synchronization ... After that, it works with no problems, until another period of inactivity. IMHO, it seems like connection pool returns an invalid/closed connection, and when Hibernate realizes that, ask another connection to the pool. I don't know how can I solve this problem or things I can do for delimiting it. Any help achieving this will be appreciate. Thanks. EDIT: Well, it finally was due a firewall rule. Database detects the connection is lost, but pool (dbcp or c3p0) not. So, it tries to query the database with no success. What is still strange for me is that timeout period is very variable. Maybe the rule is specially strange or firewall doesn't work correctly. Anyway, I have no access to that machine and I can only wait for an explanation. :(

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