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  • How to get the type of the class for comparison

    - by Halo
    I have this object which is an instance of a superclass. I want to know which subclass that object really is, so that I can decide what to do with it. There is this getClass() method but it's apparently not used for comparison issues. How can I get the sub-type of my object?

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  • Implementing deadlock condition

    - by Bhaskar
    I am trying to implementing deadlock condition but somehow I am not able to get it working. Both the threads Thread1 and Thread2 are entering in the run function but only one of them enters in Sub/Sum depending on who entered run first. Example : if Thread2 entered run first the it will call sub() and Thread1 never calls sum(). I have also added sleep time so that Thread2 sleeps before calling sum() and Thread1 gets enough time to enter Sum() but Thread1 never enters. public class ExploringThreads { public static void main(String[] args) { // TODO Auto-generated method stub threadexample a1 = new threadexample(); Thread t1 = new Thread(a1, "Thread1"); Thread t2 = new Thread(a1,"Thread2"); t1.start(); t2.start(); } } class threadexample implements Runnable{ public int a = 10; public void run(){ if(Thread.currentThread().getName().equals("Thread1")) sum(); else if(Thread.currentThread().getName().equals("Thread2")) sub(); } public synchronized void sum() { try { Thread.sleep(2000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println(Thread.currentThread().getName()+"In Sum"); sub(); } public synchronized void sub() { try { Thread.sleep(2000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println(Thread.currentThread().getName()+"In Sub"); sum(); } }

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  • How to properly mix generics and inheritance to get the desired result?

    - by yamsha
    My question is not easy to explain using words, fortunately it's not too difficult to demonstrate. So, bear with me: public interface Command<R> { public R execute();//parameter R is the type of object that will be returned as the result of the execution of this command } public abstract class BasicCommand<R> { } public interface CommandProcessor<C extends Command<?>> { public <R> R process(C<R> command);//this is my question... it's illegal to do, but you understand the idea behind it, right? } //constrain BasicCommandProcessor to commands that subclass BasicCommand public class BasicCommandProcessor implements CommandProcessor<C extends BasicCommand<?>> { //here, only subclasses of BasicCommand should be allowed as arguments but these //BasicCommand object should be parameterized by R, like so: BasicCommand<R> //so the method signature should really be // public <R> R process(BasicCommand<R> command) //which would break the inheritance if the interface's method signature was instead: // public <R> R process(Command<R> command); //I really hope this fully illustrates my conundrum public <R> R process(C<R> command) { return command.execute(); } } public class CommandContext { public static void main(String... args) { BasicCommandProcessor bcp = new BasicCommandProcessor(); String textResult = bcp.execute(new BasicCommand<String>() { public String execute() { return "result"; } }); Long numericResult = bcp.execute(new BasicCommand<Long>() { public Long execute() { return 123L; } }); } } Basically, I want the generic "process" method to dictate the type of generic parameter of the Command object. The goal is to be able to restrict different implementations of CommandProcessor to certain classes that implement Command interface and at the same time to able to call the process method of any class that implements the CommandProcessor interface and have it return the object of type specified by the parametarized Command object. I'm not sure if my explanation is clear enough, so please let me know if further explanation is needed. I guess, the question is "Would this be possible to do, at all?" If the answer is "No" what would be the best work-around (I thought of a couple on my own, but I'd like some fresh ideas)

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  • HTML/CSS Rendering to Image

    - by Steve
    Is there a library or tool that can take an html page and some css, and then render an image? I would like to define some templates server side using html code snippets, and some CSS to define the layout. Then using the template and CSS, I would like to essentially render an image of how this would display in a browser, and pass the image back to the client. Thanks.

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  • About NullPointer Exception in Arraylist

    - by user2234456
    List<PrcSubList> listSl = new ArrayList<PrcSubList>(); if (listSl == null || listSl.size() == 0) { PrcSubList subListAdd=coreService.addSubListByAddAlert(childSub); System.out.println("sublist after insert db :" + subListAdd.getName()); listSl.add(subListAdd); System.out.println(listSl.size() +" sublist after insert list:" + listSl.get(0).getName()); } Ouput with first System.out.println("sublist after insert db :" + subListAdd.getName()); sublist after insert db :SYSTEM_ALERT_12312313 Problem But i have NullPointerException with 2nd System.out.println(listSl.size() +" sublist after insert list:" + listSl.get(0).getName()); Can you help me!

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  • Connecting Android app to MySQL database

    - by opuhliyvladyslav
    Can somebody help me with question related with MySQL database using? Yesterday i was making app for getting some text data and sending them to database located on remote server! I was making POST request to database and sent few text fields to one table in database. So MY QUESTION IS: "Can I use MySQL directly (not though POST method )? and how to use it ?" (will be so glad to see url to solutions or examples) P.S. when i was sending data to server i have some errors in database fields when sending russian characters (what type of encoding sending from my app to server????)

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  • @Stateless, @Remote and @Local

    - by Jeff Foster
    In my deployment on JBoss 5.1.0GA with JavaEE-5 I have beans of the general form public interface Foo { void baz (); } @Stateless public class FooBean implements Foo { void baz() { // ... } } I have assumed that this is the same as if I have explicitly annotated the Foo interface with @Local. From seeing a stack trace in the code I think that it is actually using a remote interface, whereas I want all of my beans to be local. Do I need to explicitly annotate interfaces as Local or is there some default? Finding documentation on this is proving challenging so any links to relevant documentation would be greatly appreciated.

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  • Can I include both Apache Axis 1 and 2 libraries in the same project?

    - by ian_scho_es
    If it sounds like a ridiculous idea then it is. The client only wants to have to install one project on their server. Our web service will be bridging between mobile phones and various SOAP services made in .NET, Apache Axis 1 and 2, which rely on standards to transfer files such as MTOM and DIME. I am looking for an 'architecture' trick, such as develop the Axis 1 calls in a separate project and compile as a jar, to then pass it into the Axis 2 project.... Hmmm. Anything rather than having to download the source code for Axis 1 & 2 and compile them using the same xml libraries, etc. "It can't be done" is an acceptable answer. Thanks!

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  • How to deal with the test data in Junit?

    - by user351637
    In TDD(Test Driven Development) development process, how to deal with the test data? Assumption that a scenario, parse a log file to get the needed column. For a strong test, How do I prepare the test data? And is it properly for me locate such files to the test class files?

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  • Figuring out QuadCurveTo's parameters

    - by Fev
    Could you guys help me figuring out QuadCurveTo's 4 parameters , I tried to find information on http://docs.oracle.com/javafx/2/api/javafx/scene/shape/QuadCurveTo.html, but it's hard for me to understand without picture , I search on google about 'Quadratic Bezier' but it shows me more than 2 coordinates, I'm confused and blind now. I know those 4 parameters draw 2 lines to control the path , but how we know/count exactly which coordinates the object will throught by only knowing those 2 path-controller. Are there some formulas? import javafx.animation.PathTransition; import javafx.animation.PathTransition.OrientationType; import javafx.application.Application; import static javafx.application.Application.launch; import javafx.scene.Group; import javafx.scene.Scene; import javafx.scene.paint.Color; import javafx.scene.shape.MoveTo; import javafx.scene.shape.Path; import javafx.scene.shape.QuadCurveTo; import javafx.scene.shape.Rectangle; import javafx.stage.Stage; import javafx.util.Duration; public class _6 extends Application { public Rectangle r; @Override public void start(final Stage stage) { r = new Rectangle(50, 80, 80, 90); r.setFill(javafx.scene.paint.Color.ORANGE); r.setStrokeWidth(5); r.setStroke(Color.ANTIQUEWHITE); Path path = new Path(); path.getElements().add(new MoveTo(100.0f, 400.0f)); path.getElements().add(new QuadCurveTo(150.0f, 60.0f, 100.0f, 20.0f)); PathTransition pt = new PathTransition(Duration.millis(1000), path); pt.setDuration(Duration.millis(10000)); pt.setNode(r); pt.setPath(path); pt.setOrientation(OrientationType.ORTHOGONAL_TO_TANGENT); pt.setCycleCount(4000); pt.setAutoReverse(true); pt.play(); stage.setScene(new Scene(new Group(r), 500, 700)); stage.show(); } public static void main(String[] args) { launch(args); } } You can find those coordinates on this new QuadCurveTo(150.0f, 60.0f, 100.0f, 20.0f) line, and below is the picture of Quadratic Bezier

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  • Creating user generated reports

    - by Marquinio
    Hello Everyone, I need users to create custom reports. These users do not know any technical skills like SQL. We currently have a custom database report design. So basically whatever the user does on the GUI the application will have to generate the appropriate SQL to generate the report structure. Has anyone done this before? I know there are reporting solutions out there but we already have our own database tables for reporting. We already have a section where users can view reports displayed in HTML. Like for example if user selects a "UserID" and "Accounts" fields from GUI, how would I know that my SQL has to join the USER and ACCOUNTS table? I guess I'm just looking for some ideas to help me solve this problem. Thanks.

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  • Building a custom iterator.

    - by Isai
    I am making this class which is a custom Map based off a hash map. I have an add method where if you add an object the object will be the key, and its value will be 1 if the object is not currently in the list. However if you add object that is currently in the list its value will be bumped up by 1. So if I added 10 strings which were all the same, the key would be that string and the value will be 10. I understand in practice when I iterate through the map, there is actually only one object to iterate, however, I am trying to create a inner class that will define an iterator that will iterate the same object however many times its value is. I can do this by simply using for loops to construct an appropriate ArrayList and just create an iterator for that, but that is too inefficient. Is there an easy or more efficient way of doing this?

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  • How to trigger the specific controller action using a button?

    - by Eugene
    I'm creating a simple training project. I've implemented a controller method, which deletes an item from the list. The method is looking like this: @Controller @RequestMapping(value = "/topic") public class TopicController { @Autowired private TopicService service; ... @RequestMapping(value = "/deleteComment/{commentId}", method = RequestMethod.POST) public String deleteComment(@PathVariable int commentId, BindingResult result, Model model){ Comment deletedComment = commentService.findCommentByID(commentId); if (deletedComment != null) { commentService.deleteComment(deletedComment); } return "refresh:"; } } This method is called from the button-tag, which is looking in the following way: _form> _button formaction = "../deleteComment/1" formmethod = "post">delete_/button> _/form> Sorry, but in the form tag I've changed all the '<' characters with the '_', because the tag was invisible. In my project the form-tag is looking like a cliuckable button. But there is a serious problem: controller's method is never triggered. How can I trigger it, using a button-tag? P.S. the call is performed from the page with URI http://localhost:8080/simpleblog/topic/details/2 and controller's URI is the http://localhost:8080/simpleblog/topic/deleteComment/2

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  • Android/ORMLite Insert Row with ID

    - by Joe M
    I'm currently using ORMLite to work with a SQLite database on Android. As part of this I am downloading a bunch of data from a backend server and I'd like to have this data added to the SQLite database in the exact same format it is on the backend server (ie the IDs are the same, etc). So, my question to you is if I populate my database entry object (we'll call it Equipment), including Equipment's generatedId/primary key field via setId(), and I then run a DAO.create() with that Equipment entry will that ID be saved correctly? I tried it this way and it seems to me that this was not the case. If that is the case I will try again and look for other problems, but with the first few passes over the code I was not able to find one. So essentially, if I call DAO.create() on a database object with an ID set will that ID be sent to the database and if it is not, how can I insert a row with a primary key value already filled out? Thanks!

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  • How to introduce multi-column constraint with JPA annotations?

    - by plouh
    I am trying to introduce a multi-key constraint on a JPA-mapped entity: public class InventoryItem { @Id private Long id; @Version private Long version; @ManyToOne @JoinColumn("productId") private Product product; @Column(nullable=false); private long serial; } Basically (product, serial) pair should be unique, but I only found a way to say that serial should be unique. This obviously isn't a good idea since different products might have same serial numbers. Is there a way to generate this constraint via JPA or am I forced to manually create it to DB?

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  • Can I replicate some of the optimisations done by the JVM by hand?

    - by Subb
    I'm working on a Sudoku solver at school and we're having a little performance contest. Right now, my algorithm is pretty fast on the first run (about 2.5ms), but even faster when I solve the same puzzle 10 000 times (about 0.5ms for each run). Those timing are, of course, depend of the puzzle being solved. I know the JVM do some optimization when a method is called multiple time, and this is what I suspect is happening. I don't think I can further optimize the algorithm itself (though I'll keep looking), so I was wondering if I could replicate some of the optimizations done by the JVM. Note : compiling to native code is not an option Thanks!

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  • What is the easiest straightforward way of telling which version performs better?

    - by Peter Perhác
    I have an application, which I have re-factored so that I believe it is now faster. One can't possibly feel the difference, but in theory, the application should run faster. Normally I would not care, but as this is part of my project for my master's degree, I would like to support my claim that the re-factoring did not only lead to improved design and 'higher quality', but also an increase in performance of the application (a small toy-thing - a train set simulation). I have toyed with the latest VisualVM thing today for about four hours but I couldn't get anything helpful out of it. There isn't (or I haven't found it) a way to simply compare the profiling results taken from the two versions (pre- and post- refactoring). What would be the easiest, the most straightforward way of simply telling the slower from the faster version of the application. The difference of the two must have had an impact on the performance. Thank you.

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  • connection.setRequestProperty and excplicitly writing to the urloutputstream are they same ?

    - by Bunny Rabbit
    URL url = new URL("http://www.example.com/comment"); HttpURLConnection connection = (HttpURLConnection) url.openConnection(); connection.setDoOutput(true); connection.setRequestMethod("POST"); Is connection.setRequestProperty(key, value); same as OutputStreamWriter writer = new OutputStreamWriter(connection.getOutputStream()); writer.write("key=" + value); writer.close(); if not please correct me .

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  • Twitter friends timeline not returning full history

    - by twofivesevenzero
    I am using twitter4J to get a user's friends timeline, but it is not returning the full available history. I know there are pagination limits (200 per request and 3200 total as per http://bit.ly/ck8ysq) and I am well within those. I make a request like so: private static final int MAX_COUNT = 200; private List<Status> getAllStatuses(long sinceID) throws TwitterException { Twitter twitter = new Twitter(username, password); List<Status> friendsTimelineList = new ArrayList<Status>(); List<Status> tempList; int page = 0; do { page++; tempList = twitter.getFriendsTimeline( new Paging(page, MAX_COUNT, sinceID)); if(tempList == null ) break; friendsTimelineList.addAll(tempList); } while(true); return friendsTimelineList; } This results in only 423 statuses being returned across 3 pages. Any idea why this might be happening?

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