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  • Is nested synchronized block necessary?

    - by Dan
    I am writing a multithreaded program and I have a method that has a nested synchronized blocks and I was wondering if I need the inner sync or if just the outer sync is good enough. public class Tester { private BlockingQueue<Ticket> q = new LinkedBlockingQueue<>(); private ArrayList<Long> list = new ArrayList<>(); public void acceptTicket(Ticket p) { try { synchronized (q) { q.put(p); synchronized (list) { if (list.size() < 5) { list.add(p.getSize()); } else { list.remove(0); list.add(p.getSize()); } } } } catch (InterruptedException ex) { Logger.getLogger(Consumer.class.getName()).log(Level.SEVERE, null, ex); } } } EDIT: This isn't a complete class as I am still working on it. But essentially I am trying to emulate a ticket machine. The ticket machine maintains a list of tickets in the BlockingQueue q. Whenever a client adds a ticket to the machine, the machine also keeps track of the price of the last 5 tickets (ArrayList list)

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  • JPanel: both implementing my own paintComponent() and rendering children doesn't work

    - by Paul Marshall
    I'm extending a JPanel to display a game board, and adding a JEditorPane at the bottom to hold some status text. Unfortunately, the game board renders just fine, but the JEditorPane is just a blank gray area until I highlight the text in it, when it will render whatever text is highlighted (but not the rest). If I'm understanding Swing right, it should work, because super.paintComponent(g) should render the other children (i.e., the JEditorPane). Tell me, o great stackoverflow, what bonehead mistake am I making? public GameMap extends JPanel { public GameMap() { JEditorPane statusLines = new JEditorPane("text/plain","Stuff"); this.setLayout(new BoxLayout(this,BoxLayout.PAGE_AXIS)); this.add(new Box.Filler(/*enough room to draw my game board*/)); this.add(statusLines); } public void paintComponent(Graphics g){ super.paintComponent(g); for ( all rows ){ for (all columns){ //paint one tile } } } }

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  • Implementing tagging in JDO

    - by Julie Paltrow
    I am implementing a tagging system for a website that uses JDO . I would like to use this method. However I am new to relationships in JDO. To keep it simple, what I have looks like this: @PersistentCapable class Post { @Persistent String title; @Persistent String body; } @PersistentCapable class Tag { @Persistent String name; } What kind of JDO relationships do I need and how to implement them? I want to be able to list all Tags that belong to a Post, and also be able to list all Posts that have a given Tag. So in the end I would like to have something like this: Table: Post Columns: PostID, Title, Body Table: Tag Columns: TagID, name Table: PostTag Columns: PostID, TagID

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  • How do I authenticate regarding EJB3 Container ?

    - by FMR
    I have my business classes protected by EJB3 security annotations, now I would like to call these methods from a Spring controller, how do I do it? edit I will add some information about my setup, I'm using Tomcat for the webcontainer and OpenEJB for embedding EJB into tomcat. I did not settle on any version of spring so it's more or less open to suggestions. edit current setup works this way : I have a login form + controller that puts a User pojo inside SessionContext. Each time someone access a secured part of the site, the application checks for the User pojo, if it's there check roles and then show the page, if it's not show a appropriate message or redirect to login page. Now the bussiness calls are made thanks to a call method inside User which bypass a probable security context which is a remix of this code found in openejb security examples : Caller managerBean = (Caller) context.lookup("ManagerBeanLocal"); managerBean.call(new Callable() { public Object call() throws Exception { Movies movies = (Movies) context.lookup("MoviesLocal"); movies.addMovie(new Movie("Quentin Tarantino", "Reservoir Dogs", 1992)); movies.addMovie(new Movie("Joel Coen", "Fargo", 1996)); movies.addMovie(new Movie("Joel Coen", "The Big Lebowski", 1998)); List<Movie> list = movies.getMovies(); assertEquals("List.size()", 3, list.size()); for (Movie movie : list) { movies.deleteMovie(movie); } assertEquals("Movies.getMovies()", 0, movies.getMovies().size()); return null; } });

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  • Running server-program from a .jar file

    - by skiwi
    I have created and am working on a server-application that monitors for specific folders and takes appropriate actions whenever files are being added. Now I come to the point where I want to be able to shutdown the program, for example for applying a patch. The server runs simply in a command prompt, how can I signal that I want to perform maintenance on it? I do not think reading System.In is feasible as I am also outputting text in the prompt. Regards.

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  • How to add two label in one gridbox?

    - by Jessy
    Hello everyone, How can I add two label in the same grid box? e.g. in row 1, col 1 the will be 2 labels? The code below will add the label in two different grid. JPanel chckBox = new JPanel(new GridLayout(1,8,3,3)); JLabel label1 = new JLabel("A"); JLabel label2 = new JLabel("B"); ... chckBox.add(label1); chckBox.add(label2); ...

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  • Grails , how do I get an object NOT to save

    - by user350325
    Hello I am new to grails and trying to create a form which allows a user to change the email address associated with his/her account for a site I am creating. It asks for the user for their current password and also for the new email address they want to use. If the user enters the wrong password or an invalid email address then it should reject them with an appropriate error message. Now the email validation can be done through constraints in grails, but the password change has to match their current password. I have implemented this check as a method on a service class. See code below: def saveEmail = { def client = ClientUser.get(session.clientUserID) client.email = params.email if(clientUserService.checkPassword(session.clientUserID , params.password) ==false) { flash.message = "Incorrect Password" client.discard() redirect(action:'changeEmail') } else if(!client.validate()) { flash.message = "Invalid Email Address" redirect(action:'changeEmail') } else { client.save(); session.clientUserID = null; flash.message = "Your email address has been changed, please login again" redirect(controller: 'clientLogin' , action:'index') } } Now what I noticed that was odd was that if I entered an invalid email then it would not save the changes (as expected) BUT if I entered the wrong password and a valid email then it would save the changes and even write them back into the database even though it would give the correct "invalid password" error message. I was puzzled so set break points in all the if/else if/else blocks and found that it was hitting the first if statement as expected and not hitting the others , so it would never come accross a call to the save() method, yet it was saved anyway. After a little research I came accross documentation for the discard() method which you can see used in the code above. So I added this but still no avail. I even tried using discard then reloading the client object from the DB again but still no dice. This is very frustrating and I would be grateful for any help, since I think that this should surely not be a complicated requirement!

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  • JTextPane insert component, faulty vertical alignment

    - by John O
    I have a JTextPane, into which I need to insert a JComponent. I'm using JTextPane.insertComponent(Component). The item is indeed inserted, but the vertical positioning is too high. Instead of having the bottom of the component aligned with the baseline of the current line of text, the component is way above that position, blocking out/over-painting lines of text appearing above. I have tried calling setAlignmentY(float) with various values, on both the inserted component and the JTextPane, but it doesn't affect the behavior at all. My guess: there seems to be some state inside my JTextPane or its Document that I need to be changing. But I don't know what it is. John

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  • Move 3 rectangles up in their X but keep order of rectangles

    - by Nicolas Martel
    I have 3 rectangles being rendered here. Let's say i wanted to move them all above the line yet keep their order, how would i go about that? I tried subtracting the Y and height rather than adding the Y it but as expected, the lower rectangle goes at the top, middle stays in the middle and top goes to the bottom before: after: So is there any simple solution to render them just above rather than having to change all values ?

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  • Testing REST webservices

    - by anjanb
    HI There, My organization is working on building RESTful webservices on JBoss appserver. The QA team is used to testing SOAP webservices so far using SoapUI. SoapUI has a new version that has REST capabilities. We're considering using that. 1) Are there any publicly available RESTful services available on the net for free that someone could test ? 2) What tools are available(and used) for testing RESTful web services ? Thank you in Advance, BR, ~A

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  • Why doesn't this loop terminate?

    - by David
    Here's the sample code: public static void col (int n) { if (n % 2 == 0) n = n/2 ; if (n % 2 != 0) n = ((n*3)+1) ; System.out.println (n) ; if (n != 1) col (n) ; } this works just fine until it gets down to 2. then it outputs 2 4 2 4 2 4 2 4 2 4 infinitely. it seems to me that if 2 is entered as n then (n % 2 == 0) is true 2 will be divided by 2 to yeild 1. then 1 will be printed and since (n != 1) is false the loop will terminate. Why doesn't this happen?

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  • Swing's KeyListener and multiple keys pressed at the same time.

    - by Negai
    Hi everyone, is there any conventional way in swing of tracking down the events, when two keyboard keys are pressed at the same time? I have a couple of ideas e.g. remembering the key and event generation time so that we could in a consecutive event handler invocation check the time difference between these two events and decide, whether it's a two-button event or not. Phew. But it looks like a kludge. Thanks in advance.

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  • How to refresh an activity? Map View refresh fails

    - by poeschlorn
    Hi Guys, after implementing some Android Apps, including several Map activities, I try to refresh the activity when the GPS listener's onLocationChanged() mehtod is called. I have no idea how to tell the map activity to refresh on its own and display the new coords... the coords to store will have to be in global values, so that the location listener will have access to it. In my sample GPS-class (see code below) I just changed the text of a text view....but how to do that in map view? private class MyLocationListener implements LocationListener { @Override public void onLocationChanged(Location loc) { final TextView tv = (TextView) findViewById(R.id.myTextView); if (loc != null) { tv.setText("Location changed : Lat: " + loc.getLatitude() + " Lng: " + loc.getLongitude()); } } I think the solution of this Problem won't be very difficult, but I just need the beginning ;-) This whole app shall work like a really simple navigation system. It would be great if someone could help me a little bit further :) nice greetings, Poeschlorn

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  • Android: roatating images in a loop.

    - by user573736
    Hello, I am trying with no success to modify the code example from: http://www.inter-fuser.com/2009/08/android-animations-3d-flip.html so it will rotate the images in a loop, when clicking on the image once. (second click should pause). I tried using Handler and threading but cannot update the view since only the main thread can update UI. Exception I get from the code below: android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views. [in 'image1.startAnimation(rotation);' ('applyRotation(0, 90);' from the main thread)] package com.example.flip3d; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.view.animation.AccelerateInterpolator; import android.widget.ImageView; public class Flip3d extends Activity { private ImageView image1; private ImageView image2; private boolean isFirstImage = true; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); image1 = (ImageView) findViewById(R.id.image01); image2 = (ImageView) findViewById(R.id.image02); image2.setVisibility(View.GONE); image1.setOnClickListener(new View.OnClickListener() { public void onClick(View view) { if (isFirstImage) { applyRotation(0, 90); isFirstImage = !isFirstImage; } else { applyRotation(0, -90); isFirstImage = !isFirstImage; } } }); } private void applyRotation(float start, float end) { // Find the center of image final float centerX = image1.getWidth() / 2.0f; final float centerY = image1.getHeight() / 2.0f; // Create a new 3D rotation with the supplied parameter // The animation listener is used to trigger the next animation final Flip3dAnimation rotation = new Flip3dAnimation(start, end, centerX, centerY); rotation.setDuration(500); rotation.setFillAfter(true); rotation.setInterpolator(new AccelerateInterpolator()); rotation.setAnimationListener(new DisplayNextView(isFirstImage, image1, image2)); if (isFirstImage) { image1.startAnimation(rotation); } else { image2.startAnimation(rotation); } } } How can I manage to update the UI and control the rotation within onClick listener? Thank you, Oakist

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  • How to redirect to the same view using ModelAndview in Spring MVC framework

    - by ria
    I have a page with a link. On clicking the link a page opens up in a separate window. This new page has a form. On submitting this form, some operation takes place at the server. The result of which needs to be redirected to the same page. However after the operation on using the following: return new ModelAndView("newUser"); //This view "newUser" actually maps to the popped up window. A similar new window again pops up and the message gets displayed on this new page. Any ideas as to why this behavior or how to go about this?

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  • Google App Engine and SQL LIKE

    - by jb
    Is there any way to query GAE datastore with filter similar to SQL LIKE statement? For example, if a class has a string field, and I want to find all classes that have some specific keyword in that string, how can I do that? It looks like JDOQL's matches() don't work... Am I missing something? Any comments, links or code fragments are welcome

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  • How to embed XBase expressions in an Xtext DSL

    - by Marcus Mathioudakis
    I am writing a simple little DSL for specifying constraints on messages, and Have been trying without success for a while to embed XBase expressions into the language. The Grammar looks like this: grammar org.xtext.businessrules.BusinessRules with org.eclipse.xtext.xbase.Xbase //import "http://www.eclipse.org/xtext/xbase/Xbase" as xbase import "http://www.eclipse.org/xtext/common/JavaVMTypes" as jvmTypes generate businessRules "http://www.xtext.org/businessrules/BusinessRules" Start: rules+=Constraint*; Constraint: {Constraint} 'FOR' 'PAYLOAD' payload=PAYLOAD 'ELEMENT' element=ID 'CONSTRAINED BY' constraint=XExpression; PAYLOAD: "SimulationSessionEvents" |"stacons" |"any" ; Range: 'above' min=INT ('below' max=INT)? |'below' max=INT ('above' min=INT)? ; When trying to parse a file such as: FOR PAYLOAD SimulationSessionEvents ELEMENT matrix CONSTRAINED BY ... I can't get it to work for ... = any kind of Arithmetic expression, although it works for ...= loop or if expression, or even just a number. As soon as I do something like '-5' or '4-5' it says Couldn't resolve reference to JvmIdentifiableElement '-', even though the Xbase.xtext Grammar looks like it allows these expressions. I don't think I'm missing any Jars, as it doesn't complain when I run the mwe workflow, but only when trying to parse the input file. Any help would be much appreciated.

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  • Pageview implementation

    - by The Elite Gentleman
    Hi everyone I want to add a pageview feature on my current web application. This page view is based on the count of user viewing the page. It must be unique, i.e. I must not view a person's page 10000 times and record it as 10000 views, just record 1 view instead. My question is, should I base my pageview count on IP address? If not, what is/are the best approach in doing this? I know that if the person has logged in to my system, I can simply use the user id stored in the session and check on the record if the user has/hasn't viewed the page and update accordingly. But for "anonymous" viewers, what is the best approach? Thanks. PS How does Youtube does it?

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  • How to log all sql going through JBoss datasource with log4j

    - by Ichorus
    I've looked at log4jdbc (which does not support datasources), p6spy which seems to be what I am looking for but it has not been updated since 2003 which makes me nervous and lists only JBoss 3.x (we use JBoss 5), and JAMon which seems heavyweight for what I am trying to accomplish (a simple log of all SQL statements running through a JBoss application server). I was hoping that JBoss itself would have a switch to log all the sql (as Websphere does) but I cannot find any documentation for it so that functionality might not exist.

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  • How to get parent node in Stanford's JavaNLP?

    - by roddik
    Hello. Suppose I have such chunk of a sentence: (NP (NP (DT A) (JJ single) (NN page)) (PP (IN in) (NP (DT a) (NN wiki) (NN website)))) At a certain moment of time I have a reference to (JJ single) and I want to get the NP node binding A single page. If I get it right, that NP is the parent of the node, A and page are its siblings and it has no children (?). When I try to use the .parent() method of a tree, I always get null. The API says that's because the implementation doesn't know how to determine the parent node. Another method of interest is .ancestor(int height, Tree root), but I don't know how to get the root of the node. In both cases, since the parser knows how to indent and group trees, it must know the "parent" tree, right? How can I get it? Thanks

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  • How to differentiate between Programmer and JVM Exceptions

    - by Haxed
    As the title suggests, how can I tell a JVM thrown exception from a Programmatically(does this mean, thrown by a programmer or the program) thrown exception ? JVM Exceptions 1) ArrayIndexOutOfBoundsException 2) ClassCastException 3) NullPointerException Programmatically thrown 1) NumberFormatException 2) AssertionError Many Thanks

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