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  • Why i am getting NullPointerException for this btree method??

    - by user306540
    hi, i am writing code for btree algorithms. i am getting NullPointerException . why???? please somebody help me...! public void insertNonFull(BPlusNode root,BPlusNode parent,String key) { int i=0; BPlusNode child=new BPlusNode(); BPlusNode node=parent; while(true) { i=node.numKeys-1; if(node.leaf) { while(i>=0 && key.compareTo(node.keys[i])<0) { node.keys[i+1]=node.keys[i]; i--; } node.keys[i+1]=key; node.numKeys=node.numKeys+1; } else { while(i>=0 && key.compareTo(node.keys[i])<0) { i--; } } i++; child=node.pointers[i]; if(child!=null && child.numKeys==7) { splitChild(root,node,i,child); if(key.compareTo(node.keys[i])>0) { i++; } } node=node.pointers[i]; } }

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  • Is there any appreciable difference between if and if-else?

    - by Drew
    Given the following code snippets, is there any appreciable difference? public boolean foo(int input) { if(input > 10) { doStuff(); return true; } if(input == 0) { doOtherStuff(); return true; } return false; } vs. public boolean foo(int input) { if(input > 10) { doStuff(); return true; } else if(input == 0) { doOtherStuff(); return true; } else { return false; } } Or would the single exit principle be better here with this piece of code... public boolean foo(int input) { boolean toBeReturned = false; if(input > 10) { doStuff(); toBeReturned = true; } else if(input == 0) { doOtherStuff(); toBeReturned = true; } return toBeReturned; } Is there any perceptible performance difference? Do you feel one is more or less maintainable/readable than the others?

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  • Can I get a table name from a join select resultset metadata

    - by Matt
    Below is my code trying to retrieve table name form Resultset ResultSet rs = stmt.executeQuery("select * from product"); ResultSetMetaData meta = rs.getMetaData(); int count = meta.getColumnCount(); for (int i=0; i<count; i++) { System.out.println(meta.getTableName(i)); } But it returns empty, no mention it is a join select resultset. Is there any other approaches to retrieve table name from reusltset metadata?

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  • Why is JavaMail Transport.send() a static method?

    - by skiphoppy
    I'm revising code I did not write that uses JavaMail, and having a little trouble understanding why the JavaMail API is designed the way it is. I have the feeling that if I understood, I could be doing a better job. We call: transport = session.getTransport("smtp"); transport.connect(hostName, port, user, password); So why is Eclipse warning me that this: transport.send(message, message.getAllRecipients()); is a call to a static method? Why am I getting a Transport object and providing settings that are specific to it if I can't use that object to send the message? How does the Transport class even know what server and other settings to use to send the message? It's working fine, which is hard to believe. What if I had instantiated Transport objects for two different servers; how would it know which one to use? In the course of writing this question, I've discovered that I should really be calling: transport.sendMessage(message, message.getAllRecipients()); So what is the purpose of the static Transport.send() method? Is this just poor design, or is there a reason it is this way?

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  • how to return a list using SwingWorker

    - by Ender
    I have an assignment where i have to create an Image Gallery which uses a SwingWorker to load the images froma a file, once the image is load you can flip threw the image and have a slideshow play. I am having trouble getting the list of loaded images using SwingWorker. This is what happens in the background it just publishes the results to a TextArea // In a thread @Override public List<Image> doInBackground() { List<Image> images = new ArrayList<Image>(); for (File filename : filenames) { try { //File file = new File(filename); System.out.println("Attempting to add: " + filename.getAbsolutePath()); images.add(ImageIO.read(filename)); publish("Loaded " + filename); System.out.println("Added file" + filename.getAbsolutePath()); } catch (IOException ioe) { publish("Error loading " + filename); } } return images; } } when it is done I just insert the images in a List<Image> and that is all it does. // In the EDT @Override protected void done() { try { for (Image image : get()) { list.add(image); } } catch (Exception e) { } } Also I created an method that returns the list called getImages() what I need to get is the list from getImages() but doesn't seam to work when I call execute() for example MySwingWorkerClass swingworker = new MySwingWorkerClass(log,list,filenames); swingworker.execute(); imageList = swingworker.getImage() Once it reaches the imageList it doesn't return anything the only way I was able to get the list was when i used the run() instead of the execute() is there another way to get the list or is the run() method the only way?. or perhaps i am not understanding the Swing Worker Class.

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  • Deploy a jar in Jetty

    - by Dimitri
    Hi guys, I was wondering if is it possible to deploy a jar file in Jetty? If not, are there applications servers who can do so? I am beginner. I am asking this question because all the docs that i have found, it seems that we can only deploy war archive in application servers. Is that true?

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  • Netbeans Error: "Could not add one or more tag libraries"

    - by JJ4UC
    I am using Netbeans 6.1 and Tomcat 6.0.1.6. I made some very minor changes to a project that had been working and now I am getting the following error: com.sun.rave.web.ui.appbase.ApplicationException: org.apache.jasper.JasperException: Could not add one or more tag libraries. The only change I made was to a backing bean method, no new UI components, jsp, etc. Any direction would be greatly appreciated. Thanks!

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  • JavaApplicationStub with SWT causing problems

    - by mystro
    I created an application in Eclipse that uses SWT for the GUI. I've attempted to deploy the application using the Eclipse deploy, but it seems that when I do that, LSUIElement is not respected, and I can't force the application to disappear from the dock. Nonwhistanding that issue, the application actually deploys ok and is runnable. I attempted to deploy the application using Jar Bundler, but when I try to run the application, I get the following errors: 2010-06-09 21:44:02.564 JavaApplicationStub[89045:2003] * __NSAutoreleaseNoPool(): Object 0x10021f260 of class NSCFString autoreleased with no pool in place - just leaking 2010-06-09 21:44:02.568 JavaApplicationStub[89045:2003] * __NSAutoreleaseNoPool(): Object 0x10010a0a0 of class NSCFNumber autoreleased with no pool in place - just leaking 2010-06-09 21:44:02.569 JavaApplicationStub[89045:2003] * __NSAutoreleaseNoPool(): Object 0x1001127a0 of class NSCFString autoreleased with no pool in place - just leaking 2010-06-09 21:44:02.582 JavaApplicationStub[89045:2003] * __NSAutoreleaseNoPool(): Object 0x7fff70b7af70 of class NSCFString autoreleased with no pool in place - just leaking 2010-06-09 21:44:02.583 JavaApplicationStub[89045:2003] * __NSAutoreleaseNoPool(): Object 0x100123ea0 of class NSCFData autoreleased with no pool in place - just leaking 2010-06-09 21:44:02.587 JavaApplicationStub[89045:2003] * __NSAutoreleaseNoPool(): Object 0x100225b90 of class NSCFDictionary autoreleased with no pool in place - just leaking 2010-06-09 21:44:02.588 JavaApplicationStub[89045:2003] * __NSAutoreleaseNoPool(): Object 0x100225ee0 of class __NSFastEnumerationEnumerator autoreleased with no pool in place - just leaking in a very, very, very, long list. The application launches and appears to hang with the icon constantly bouncing in the dock, and the first GUI menu only partially loaded (it looks like one of the text boxes is semi visible, and the overall rectangle is the right size, but the GUI is not showing properly. It is essentially hung.) I'm hoping someone has had experience with this problem, and may be able to help! Thanks!

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  • Why do InterruptedExceptions clear a thread's interrupted status?

    - by Hanno Fietz
    If a thread is interrupted while inside Object.wait() or Thread.join(), it throws an InterruptedException, which resets the thread's interrupted status. I. e., if I have a loop like this inside a Runnable.run(): while (!this._workerThread.isInterrupted()) { // do something try { synchronized (this) { this.wait(this._waitPeriod); } } catch (InterruptedException e) { if (!this._isStopping()) { this._handleFault(e); } } } the thread will continue to run after calling interrupt(). This means I have to explicitly break out of the loop by checking for my own stop flag in the loop condition, rethrow the exception, or add a break. Now, this is not exactly a problem, since this behaviour is well documented and doesn't prevent me from doing anything the way I want. However, I don't seem to understand the concept behind it: Why is a thread not considered interrupted anymore once the exception has been thrown? A similar behaviour also occurs if you get the interrupted status with interrupted() instead of isInterrupted(), then, too, the thread will only appear interrupted once. Am I doing something unusual here? For example, is it more common to catch the InterruptedException outside the loop? (Even though I'm not exactly a beginner, I tagged this "beginner", because it seems like a very basic question to me, looking at it.)

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  • Extract Generic types from extended Generic

    - by Brigham
    I'm trying to refactor a class and set of subclasses where the M type does extend anything, even though we know it has to be a subclass of a certain type. That type is parametrized and I would like its parametrized types to be available to subclasses that already have values for M. Is there any way to define this class without having to include the redundant K and V generic types in the parameter list. I'd like to be able to have the compiler infer them from whatever M is mapped to by subclasses. public abstract class NewParametrized<K, V, M extends SomeParametrized<K, V>> { public void someMethodThatTakesKAndV(K k1, V v1) { } } In other words, I'd like the class declaration to look something like: public class NewParametrized<M extends SomeParametrized<K, V>> { And K and V's types would be inferred from the definition of M.

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  • Trouble adding Image to a JPanel

    - by user1276078
    I'm making a video game, and I need to add an image to a JPanel and then add that JPanel to a JFrame. All of the tutorials I've seen say to add it to a JLabel, but the image needs to be able to move around. Unless you can move a JLabel around, I can't do that. How would I be able to add an Image directly to a JPanel. This is what I have so far, but it is just like it was on a JApplet class Penguin extends JPanel { public Image image; public void paintComponent( Graphics g ) { image = getImage( getDocumentBase(), "Penguins.jpg" ); g.drawImage( image, 0, 0, this ); } }

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  • Get email address from OpenId using Jboss/Seam

    - by Andy
    I'm using the org.jboss.seam.security.openid.OpenId class to login user's to my seam webapp. Currently I'm saving the validatedId (openid.getValidatedId()) into the database, and asking the user to provide their own email address and first and last name after logging in. I'm using Google, Yahoo, AOL, and MyOpenID for the openId Providers. Is there any way to retrieve the email address and or first/last name of the user without having them enter this in manually?

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  • Hibernate: Walk millions of rows and don't leak memory

    - by Autocracy
    The below code functions, but Hibernate never lets go of its grip of any object. Calling session.clear() causes exceptions regarding fetching a joined class, and calling session.evict(currentObject) before retrieving the next object also fails to free the memory. Eventually I exhaust my heap space. Checking my heap dumps, StatefulPersistenceContext is the garbage collector's root for all references pointing to my objects. public class CriteriaReportSource implements JRDataSource { private ScrollableResults sr; private Object currentObject; private Criteria c; private static final int scrollSize = 10; private int offset = 1; public CriteriaReportSource(Criteria c) { this.c = c; advanceScroll(); } private void advanceScroll() { // ((Session) Main.em.getDelegate()).clear(); this.sr = c.setFirstResult(offset) .setMaxResults(scrollSize) .scroll(ScrollMode.FORWARD_ONLY); offset += scrollSize; } public boolean next() { if (sr.next()) { currentObject = sr.get(0); if (sr.isLast()) { advanceScroll(); } return true; } return false; } public Object getFieldValue(JRField jrf) throws JRException { Object retVal = null; if(currentObject == null) { return null; } try { retVal = PropertyUtils.getProperty(currentObject, jrf.getName()); } catch (Exception ex) { Logger.getLogger(CriteriaReportSource.class.getName()).log(Level.SEVERE, null, ex); } return retVal; } }

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  • Inheriting the main method

    - by Eric
    I want to define a base class that defines a main method that instantiates the class, and runs a method. There are a couple of problems though. Here is the base class: public abstract class Strategy { abstract void execute(SoccerRobot robot); public static void main(String args) { Strategy s = new /*Not sure what to put here*/(); s.execute(new SoccerRobot()) } } And here is an example derived class: public class UselessStrategy { void execute(SoccerRobot robot) { System.out.println("I'm useless") } } It defines a simple execute method, which should be called in a main method upon usage as a the main application. However, in order to do so, I need to instantiate the derived class from within the base class's main method. Which doesn't seem to be possible. I'd rather not have to repeat the main method for every derived class, as it feels somewhat unnessary. Is there a right way of doing this?

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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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  • Twitter Client using JavaScript and Oauth

    - by MP
    Is there any good tutorial or example to build a Twitter client using popup and oauth for login (Ex: http://twitgoo.com/) Also once the user logs in, the new tweets showed without any page refresh and also the ability to post a tweet without page refresh. If there is no good example, please suggest the API or libraries i need or any general suggestion.

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  • Why my object sees variables which were not given to it in the constructor?

    - by Roman
    I have the following code. Which is "correct" and which I do not understand: private static void updateGUI(final int i, final JLabel label) { SwingUtilities.invokeLater( new Runnable() { public void run() { label.setText("You have " + i + " seconds."); } } ); } I create a new instance of the Runnable class and then in the run method of this instance I use variables label and i. It works, but I do not understand why it work. Why the considered object sees values of these variables. According to my understanding the code should look like that (and its wrong): private static void updateGUI(final int i, final JLabel label) { SwingUtilities.invokeLater(new Runnable(i,label) { public Runnable(int i, JLabel label) { this.i = i; this.label = label; } public void run() { label.setText("You have " + i + " seconds."); } }); } So, I would give the i and label variables to the constructor so the object can access them... By the way, in the updateGUI I use final before the i and label. I think I used final because compiler wanted that. But I do not understand why.

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  • Entity Aspect (in Spring)

    - by niklassaers
    Hi guys, I'm having a bit of a problem defining my aspects. I've got a bunch of entities that I'd like to profile the get-methods in, so I've written the following pointcut and method @Pointcut("execution(* tld.myproject.data.entities.*.get*()") public void getEntityProperty() {} @Around("getEntityProperty()") public Object profileGetEntityProperty(ProceedingJoinPoint pjp) throws Throwable { long start = System.currentTimeMillis(); String name = pjp.getSignature().getName(); Object output = pjp.proceed(); long elapsedTime = System.currentTimeMillis() - start; if(elapsedTime > 100) System.err.println("profileGetEntityProperty: Entity method " + name + " execution time: " + elapsedTime + " ms."); return output; } I've got weaving turned on in my configuration, and aspects weaving into the business layer work just fine. Is my pointcut correctly written? Or is there something about entities that make them non-weavable? (my entity is prefixed with @Entity before the class definition) Cheers Nik

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  • NullPointerException when thying to add an object to a PriorityQueue

    - by meagan
    i keep getting a null pointer exception when trying to add an object to a priority queue i initialize the queue: private PriorityQueue<NodeObject> nodes; and here i try to add to it: NodeObject childNode = new NodeObject(child, 1); nodes.add(childNode); why doesn't this work? i know my NodeObject is not null because i create it right before i add it.

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  • How do you determine an acceptable response time for App Engine DB requests?

    - by qiq
    According to this discussion of Google App Engine on Hacker News, A DB (read) request takes over 100ms on the datastore. That's insane and unusable for about 90% of applications. How do you determine what is an acceptable response time for a DB read request? I have been using App Engine without noticing any issues with DB responsiveness. But, on the other hand, I'm not sure I would even know what to look for in that regard :)

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  • Android ListActivity with Bitmaps and Garbage Collection issue

    - by chis54
    I have a ListActivity and in it I set my list items with a class that extends SimpleCursorAdapter. I'm overriding bindView to set my Views. I have some TextViews and ImageViews. This is how I set my list items in my cursor adapter: String variableName = "drawable/q" + num + "_200px"; int imageResource = context.getResources().getIdentifier(variableName, "drawable", context.getPackageName()); if (imageResource != 0 ) { // The drawable exists Bitmap b = BitmapFactory.decodeResource(context.getResources(), imageResource); width = b.getWidth(); height = b.getHeight(); imageView.getLayoutParams().width = (int) (width); imageView.getLayoutParams().height = (int) (height); imageView.setImageResource(imageResource); } else { imageView.setImageResource(R.drawable.25trans_200px); } The problem I'm having is whenever I update my list with setListAdapter I get a large amount of garbage collection: D/dalvikvm(18637): GC_EXTERNAL_ALLOC freed 125K, 51% free 2710K/5447K, external 2022K/2137K, paused 75ms D/dalvikvm(18637): GC_EXTERNAL_ALLOC freed 30K, 51% free 2701K/5447K, external 2669K/2972K, paused 64ms D/dalvikvm(18637): GC_EXTERNAL_ALLOC freed 23K, 51% free 2713K/5447K, external 3479K/3579K, paused 53ms D/dalvikvm(18637): GC_EXTERNAL_ALLOC freed 22K, 51% free 2706K/5447K, external 3303K/3352K, paused 64ms D/dalvikvm(18637): GC_EXTERNAL_ALLOC freed 21K, 51% free 2722K/5447K, external 3569K/3685K, paused 102ms D/dalvikvm(18637): GC_EXTERNAL_ALLOC freed 23K, 50% free 2755K/5447K, external 3499K/3605K, paused 65ms D/dalvikvm(18637): GC_EXTERNAL_ALLOC freed 23K, 50% free 2771K/5447K, external 4213K/4488K, paused 53ms D/dalvikvm(18637): GC_EXTERNAL_ALLOC freed 18K, 49% free 2796K/5447K, external 5057K/5343K, paused 75ms D/dalvikvm(18637): GC_EXTERNAL_ALLOC freed 28K, 49% free 2803K/5447K, external 5944K/5976K, paused 53ms D/dalvikvm( 435): GC_EXPLICIT freed 6K, 54% free 2544K/5511K, external 1625K/2137K, paused 50ms D/dalvikvm( 165): GC_EXPLICIT freed 85K, 52% free 2946K/6087K, external 4838K/5980K, paused 111ms D/dalvikvm( 448): GC_EXPLICIT freed 1K, 54% free 2540K/5511K, external 1625K/2137K, paused 50ms D/dalvikvm( 294): GC_EXPLICIT freed 8K, 55% free 2598K/5703K, external 1625K/2137K, paused 64ms What can I do to avoid this? It's causing my UI to be sluggish and when I scroll, too.

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