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  • Jave JIT compiler compiles at compile time or runtime ?

    - by Tony
    From wiki: In computing, just-in-time compilation (JIT), also known as dynamic translation, is a technique for improving the runtime performance of a computer program. So I guess JVM has another compiler, not javac, that only compiles bytecode to machine code at runtime, while javac compiles sources to bytecode,is that right?

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  • Is System.nanoTime() consistent across threads?

    - by obvio171
    I want to count the time elapsed between two events in nanoseconds. To do that, I can use System.nanoTime() as mentioned here. The problem is that the two events are happening in different threads. Since nanoTime() doesn't return an absolute timestamp but instead can only be used to calculate time differences, I'd like to know if the values I get on the two different threads are consistent with the physical time elapsed between the two events.

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  • Why are static imports of static methods with same names legal?

    - by user1055638
    Lets say we have these packages and classes: package p1; public class A1 { public static void a() {} } package p2; public class A1 { public static void a() {} } package p3; import static p1.A1.a; import static p2.A1.a; public class A1 { public static void test() { } } I am wondering, why the static import of methods is legal (won't result in compile time error) in package p3? We won't be able to use them further in the test() method as such usage will result in the compile time error. Why it is not the same as with a normal import of classes. Lets say we would like to import classes A1 from packages p1 and p2 into p3: package p3; import p1.A1; import p2.A1; such import is illegal and will result in the compile time error.

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  • OSGI, Servlets and JPA hello world / tutorial / example

    - by Kamil
    I want to build a web application which basically is a restful web-service serving json messages. I would like it to be as simple as possible. I was thinking about using servlets (with annotations). JPA as a database layer is a must - Toplink or Hibernate. Preferably working on Tomcat. I want to have app divided into modules serving different functionality (auth service, customer service, etc..). And I would like to be able to update those modules without reinstalling whole application on the server - like eclipse plugins, user is notified (when he enters webapp's home url) that update is available, clicks it, and app is downloading and installing updated module. I think this functionality can be made with OSGI, but I can't find any example code, or tutorial with simple hello world updatable servlet providing some data from database through jpa. I'm looking for an advice: - Is OSGI the right tool for this or it can be done with something simpler? - Where can I find some examples covering topic (or topics) which I need for this project. - Which OSGI implementation would be best-simplest for this task. *My knowledge of OSGI is basic. I know how bundles are described, I understand concept of OSGI container and what it does. I have never created any OSGI app yet.

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  • Algorithm for redirecting the traffic

    - by TechGeeky
    I was going through the interview questions and found out the below question which I am not able to answer it. Can anyone provide some sort of algorithm for this problem how can I solve it? There are a cluster of stateless servers all serving the same pages. The servers are hosting 5 web pages- p1.html, p2.html, p3.html, p4.html and p5.html p1.html just redirects users to the other 4 pages Requests to p1.html should result in 10% of users being redirected to p2.html, 5% of users redirected to p3.html, 20% of users redirected to p4.html, and 65% of users redirected to p5.html. Users do not need to stick to the page they are first redirected to. They could end up on a different page with every request to p1.html Write a function/pseudocode that would be invoked with every request to p1.html and redirect the correct percentage of users to the correct page. Any suggestions will be of great help.

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  • How does the event dispatch thread work?

    - by Roman
    With the help of people on stackoverflow I was able to get the following working code of the simples GUI countdown (it just displays a window counting down seconds). My main problem with this code is the invokeLater stuff. As far as I understand the invokeLater send a task to the event dispatching thread (EDT) and then the EDT execute this task whenever it "can" (whatever it means). Is it right? To my understanding the code works like that: In the main method we use invokeLater to show the window (showGUI method). In other words, the code displaying the window will be executed in the EDT. In the main method we also start the counter and the counter (by construction) is executed in another thread (so it is not in the event dispatching thread). Right? The counter is executed in a separate thread and periodically it calls updateGUI. The updateGUI is supposed to update GUI. And GUI is working in the EDT. So, updateGUI should also be executed in the EDT. It is why the code for the updateGUI is inclosed in the invokeLater. Is it right? What is not clear to me is why we call the counter from the EDT. Anyway it is not executed in the EDT. It starts immediately a new thread and the counter is executed there. So, why we cannot call the counter in the main method after the invokeLater block? import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.SwingUtilities; public class CountdownNew { static JLabel label; // Method which defines the appearance of the window. public static void showGUI() { JFrame frame = new JFrame("Simple Countdown"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); label = new JLabel("Some Text"); frame.add(label); frame.pack(); frame.setVisible(true); } // Define a new thread in which the countdown is counting down. public static Thread counter = new Thread() { public void run() { for (int i=10; i>0; i=i-1) { updateGUI(i,label); try {Thread.sleep(1000);} catch(InterruptedException e) {}; } } }; // A method which updates GUI (sets a new value of JLabel). private static void updateGUI(final int i, final JLabel label) { SwingUtilities.invokeLater( new Runnable() { public void run() { label.setText("You have " + i + " seconds."); } } ); } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { showGUI(); counter.start(); } }); } }

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  • Discover NullPointerException bugs using FindBug

    - by alex2k8
    When I run FindBug on this code, it reports NO issues. boolean _closed = false; public void m1(@Nullable String text) { if(_closed) return; System.out.println(text.toLowerCase()); } While here it finds issue as expected: public void m1(@Nullable String text) { System.out.println(text.toLowerCase()); // FireBug: text must be nonnull but is marked as nullable } Why does it fail in first case?

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  • Problem with extending JPanel

    - by Halo
    I have an abstract entity: public abstract class Entity extends JPanel implements FocusListener And I have a TextEntity: public class TextEntity extends Entity Inside TextEntity's constructor I want to put a JTextArea that will cover the panel: textArea = new JTextArea(); textArea.setSize(getWidth(),getHeight()); add(textArea); But getWidth() and getHeight() returns 0. Is it a problem with the inheritance or the constructor?

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  • How to copy generically superclass instances to subclass instances?

    - by gerry
    Hi @all, I have a class hierarchy / inheritance like this: public class A { private String name; // with getters & setters public void doAWithName(){ ... } } public class B extends A { public void doBWithName(){ // a differnt implementation to what I do in class A } } public class C extends B { public void doCWithName(){ // a differnt implementation to what I do in class A and B } } So at one time there is a instance of class A with the initialized field "name". Later I want this instance of A get wrapped into instance of B or C. So the superclasses should be get wrapped with a subclass! How can I make this most efficent with respect to DRY? I've thought about a constructor that does some copying with the getters/setters. But in this case I have to repeat myself - and this doesn't respect anymore to my initial requirement of DRY! So, how can I warp A to B by just initializing B's new fields (with default values) and delegating the rest to a method in A (which knows more than B about which fields of A should be accessed...). In the same way: If A should be wrapped into C only a method in c should init C's 'new' fields, delegate to B's wrap method (which therefore inits B's 'new' fields in C) and at last B delegates to A which copies it's fields to the fields of C). So in the end I have a new instance of C which has the values of A wrapped (and some default init values to the fields which the inheritance hierarchy has added).

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  • vlcj not displaying the video

    - by Cássio Eudardo
    I'm using vlcj to play video, but the video doesn't display on some computers(i tested in 4 and worked on 2, all windows), on 1 it displays the button but not the video and on the other it just display a gray background without the button. I tested .wmv and .avi files. I'm using the following code: public class Video extends JFrame implements WindowListener{ private JPanel contentPane; private JButton btnClose; private Dimension size; private float aspectRatio; private EmbeddedMediaPlayer mediaPlayer; public Video() { try { size = Toolkit.getDefaultToolkit().getScreenSize(); aspectRatio = (float)size.width/size.height; String file = "..."; btnClose = new JButton("X"); btnClose.addActionListener(new ActionListener() {...}); btnClose.setBounds(640 - 50, 10, 40, 40); setBounds(size.width/2 - 320, (int)(size.height - 40*aspectRatio) - 250, 640, 200); contentPane = new JPanel(); contentPane.setLayout(null); setContentPane(contentPane); WindowsCanvas surface = new WindowsCanvas(); contentPane.setBounds(0, 0, 640, 200); surface.setBounds(0, 0, 640, 200); MediaPlayerFactory factory = new MediaPlayerFactory(new String("--no-video-title-show")); mediaPlayer = factory.newEmbeddedMediaPlayer(); surface.addMouseListener(new MouseListener() {...}); contentPane.add(btnClose); contentPane.add(surface); setVisible(true); mediaPlayer.setVideoSurface(factory.newVideoSurface(surface)); mediaPlayer.setRepeat(true); mediaPlayer.playMedia(file); } catch(Exception e) { } }}

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  • How to get result size from an SQL query and check size

    - by Jimmy
    Hi I'm trying to write a piece of code for a simple verification method as part of a MVC. At present the SQL is not written as a prepared statement so obviously it is at risk to a SQL injection so any help in regards to writing the SQL as a prepared statement would be really helpful. The method which is in the User model. public boolean getLoginInfo() { try { DBAccess dbAccess = new DBAccess(); String sql = "SELECT username, password FROM owner WHERE username = '" + this.username + "'AND password = '" + this.password + "';"; dbAccess.close();dbAccess.executeQuery(sql); dbAccess.close(); return true; } catch (Exception e) { return false; } } I want to get the size of the result set which is generated by the SQL query and if the size of it is 1 return true else it's false. If you need more info on the rest of the MVC just post and I'll get it up here.

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  • GWT: What is the way to handle Click on GWT FlowPanel

    - by shaman.sir
    May be a dumb question, but GWT FlowPanel (raw div element) does not provides something to handle a mouseclick/mousemovement on it. Overriding onBrowserEvent do not works either. If setting onclick event using native JavaScript (need to specify positive height before, 'div' have a height of 0 if not specified), then catching these events is working properly. Is there a way to do it without using JSNI?

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  • Drag and drop + custom drawing in Android

    - by Rich
    I am working on something that needed custom drag-and-drop functionality, so I have been subclassing View, doing a bunch of math in response to touch events, and then rendering everything manually through code on the canvas in onDraw. Now, the more functionality I add, the more the code is growing out of control and I find myself writing a ton more code than I would expect to write in a high level environment like Android. Is this how it's done, or am I missing something? If I'm not doing anything fancy in the UI, the framework handles the majority of my interactions. Built-in controls handle the touches and drags, and my code is pretty much limited to business logic and data. Is there a way to leverage the power of some of the UI controls and things like animations while also doing some of it manually in the onDraw canvas? Is there an accepted standard of when to use one or the other (if indeed the two approaches can be mixed)?

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  • GWT: stange import collision error in visualisation api

    - by parag_
    hi, I'm attempting to add two charts to a gwt page using the visualization api, but for some strange and inexplicable reason, eclipse claims that the following two imports are colliding - which makes no sense to me. In the methods where i am calling them, I have even tried using the fully qualified names, but that doesnt seem to help either. Any idea what may be going on ? import com.google.gwt.visualization.client.visualizations.Table.Options; import com.google.gwt.visualization.client.visualizations.LineChart.Options;

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  • XML parse file from HTTP

    - by Travis
    I have an XML file located at a location such as http://example.com/test.xml I'm trying to parse the XML file to use it in my program with xPath like this but it is not working. Document doc = builder.parse(new File(url)); How can I get the XML file?

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  • How to change default font in netbeans platform?

    - by nathan
    I'd like to know how to change the default font used in netbeans platform. I'm not asking for changing the font in the Netbeans IDE but in the platform, then all my derived applications would use this default font. A netbeans application is a group of Jcomponent so i could easily set the font of each of those components but there is still things like notifications that i can't access directly to change the font, so i think the best would be to change the font by default. Programmaticaly or any other way... maybe editing one the jar?

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  • Hibernate configuration - session factory scanning?

    - by Marcus
    We have this hibernate.cfg.xml file. Is there a way to tell Hibernate to just scan a directory instead of having to add an entry here for each class? <hibernate-configuration> <session-factory> <mapping class="com.abc.domain.model.A" /> <mapping class="com.abc.domain.model.B" /> <mapping class="com.abc.domain.model.C" /> <mapping class="com.abc.domain.model.D" /> <mapping class="com.abc.domain.model.E" /> </session-factory> </hibernate-configuration>

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  • how to remove ConcurrentModificationException

    - by maverick
    what is this exception and how to remove this in my problem i am creating an arraylist of objects, and after checking some condition,i want to remove some objects. but the program is giving this exception ConcurrentModificationException. how to remove this thanks in advance

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  • How do I change content of ComboFieldEditor?

    - by fastcodejava
    I want to change the values on one ComboFieldEditor depending on another ComboFieldEditor in an eclipse plugin. E.g. if the user changes the package, different classes need to be populated in the second ComboFieldEditor. The ComboFieldEditor class does not seem to to have a way to change the items on the fly.

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