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  • interfacing: simplified

    - by code wombat
    i've been doing some research on interfaces and a simple layman's explanation for what it truly is. For some reason people love using overly complex explanations and jargon to explain truly simple concepts (guess it makes them feel big) and i have a gut feeling it's the same in this case. so from what i could grasp, it seems like interfaces are nothing more than a way to reserve method names, their return type if any, and the type and amount of arguments they accept. so when a class implements an interface (or interfaces) it is forced to define the body of each method from the interface(s). Am i on the nose with this one or do i need to keep digging? p.s. i know javascript doesn't have support for interfaces, but i still need to understand the concept because there are quite a few places where it's shown how to emulate to an extent.

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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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  • How can you tell if an activities state is stored?

    - by Joren
    I have an activity which pulls some JSON from my server, and then uses it to draw a list. That list launches further activities. My problem is that I can't figure out a way to tell if the activity is still alive when you go back to it, so I end up re-querying my JSON from the server and redrawing the list every time the user goes back to the activity. How can I tell if my activity is still alive so I can skip the redraw?

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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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  • Request attributes in jsf / icefaces behaves strange (survive request end)

    - by hubertg
    I have the following code in a listener method: FacesContext.getCurrentInstance().getExternalContext().getRequestMap().put("time", new Date()); When a button is clicked the following code is executed System.out.println(FacesContext.getCurrentInstance().getExternalContext().getRequestMap().get("time")); One could except that "time" is null when the listener was not executed while processing the current request, but: it seems like the "time" object survives the request processing. So when "time" has been set sometimes in the past it stays there... can anybody explain this? Thanks.

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  • Restful Path Parameters in Spring MVC 3

    - by MDK
    Is it possible to: set a URI template in the mvc:view-controller element of the *-servlet.xml file or in a controller method and then use/get that path parameter in a jsp? I understand that using @PathVariable in a controller method will give me access to the path parameter in that controller method. But how can I gain access to the path parameter in the jsp? For example, is it possible to do something like: *-servlet.xml file: <beans...> <mvc:view-controller path="/home" view-name="home"/> <mvc:view-controller path="/home/{error}" view-name="home"/> </beans> jsp file: <c:if test="${not empty param['error']}"> <span class="error">You have an error...</span> </c:if>

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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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  • 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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  • Weird output of Throwable getMessage()

    - by Ravi Gupta
    Hi I have below pseudo code with throws an exception like this throw new MyException("Bad thing happened","com.stuff.errorCode"); where MyException extends Exception class. So the problem is when I try to get the message from MyException class by calling myEx.getMessage() it returns ???en_US.Bad thing happened??? instead of my original message i.e. Bad thing happened I have checked that MyException class doesn't overrides Throwable class's getMessage() behavior. Below is the how the call passes from MyException.getMessage() to Throwable.getMessage() public MyException(String msg, String sErrorCode){ super(msg); this.sErrorCode = sErrorCode; this.iSeverity = 0; } which then calls public Exception(String message) { super(message); } and finally public Throwable(String message) { fillInStackTrace(); detailMessage = message; } when I do a getMessage on myexception it calls Throwable's getMessage as below public String getMessage() { return detailMessage; } So ideally it should return the original message as I set when throwing the exception. What's the ???en_US thing ?

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  • Sad logic on types

    - by user2972231
    Code base is littered with code like this: BaseRecord record = // some BaseRecord switch(record.source()) { case FOO: return process((FooRecord)record); case BAR: return process((BarRecord)record); case QUUX: return process((QuuxRecord)record); . . // ~25 more cases . } and then private SomeClass process(BarRecord record) { } private SomeClass process(FooRecord record) { } private SomeClass process(QuuxRecord record) { } It makes me terribly sad. Then, every time a new class is derived from BaseRecord, we have to chase all over our code base updating these case statements and adding new process methods. This kind of logic is repeated everywhere, I think too many to add a method for each and override in the classes. How can I improve this?

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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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  • 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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  • Database insertion not happening

    - by Pramod Setlur
    int i=0; ContentValues values = null; for ( SortedMap.Entry<Integer, String> entry : mapDefect.entrySet() ) { if( i++ < count ) continue; if( i < arrlst.size() ) { values = new ContentValues(); Log.d("MAP", "Id :"+entry.getKey()+"Des :"+entry.getValue()+"Co :"+ arrlst.get(i)); values.put( MARKER_COORD, arrlst.get( i ) ); values.put( MARKER_ID, entry.getKey() ); values.put( DEFECT_DESCRIPTION, entry.getValue() ); values.put( IMAGE_ID_F, imageID + 1 ); Log.d( "Err", "in insertNewDefectsDescription" ); long rowId = db.insert( TABLE_DEFECTS, null, values ); long rowId1 = rowId; i++; } } So, I want to access the arraylist only after the count variable, which is why the:- if(i++<count) continue; But, when I insert a break point at the 'insert' line, it is not working. The line is not executing at all, and hence the data is not being inserted into the database. What has gone wrong?? The 'values' are null.

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  • Explanation of output

    - by Anon
    My program class Building { Building() { System.out.print("b "); } Building(String name) { this(); System.out.print("bn " + name); } }; public class House extends Building { House() { System.out.print("h "); // this is line# 1 } House(String name) { this(); // This is line#2 System.out.print("hn " + name); } public static void main(String[] args) { new House("x "); } } We know that compiler will write a call to super() as the first line in the child class's constructor. Therefore should not the output be: b (call from compiler written call to super(), before line#2 b (again from compiler written call to super(),before line#1 ) h hn x But the output is b h hn x Why is that?

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  • paintComponent on JPanel, image flashes and then disappears

    - by mark
    I have a JApplet (MainClass extends JApplet), a JPanel (ChartWindow extends JPanel) and a Grafico class. The problem is that the Grafico class instance has 2 JPanel that should show 2 images (1 for each panel) but the images are shown and after a little while they disappears: instead of them i get a gray background (like an empty JPanel). This happens for every repaint() call (that are made in the ChartWindow class) the MainClass init() contains chartwindow=new ChartWindow(); add(chartwindow) chartwindow has a Grafico instance. it's the ChartWindow's paintComponent (override) paintComponent(Graphics g) { super.paintComponent(g); Image immagineGrafico=createImage(grafico.pannelloGrafico.getWidth() ,grafico.pannelloGrafico.getHeight()); Image immagineVolumi=createImage(grafico.pannelloVolumi.getWidth() ,grafico.pannelloVolumi.getHeight()); Graphics2D imgGrafico=(Graphics2D)immagineGrafico.getGraphics(); Graphics2D imgVolumi=(Graphics2D)immagineVolumi.getGraphics(); grafico.draw(imgGrafico,imgVolumi,mouseX,mouseY); ((Graphics2D)grafico.pannelloGrafico.getGraphics()).drawImage(immagineGrafico,0,0,this); ((Graphics2D)grafico.pannelloVolumi.getGraphics()).drawImage(immagineVolumi,0,0,this); } grafico's JPanels are added this way in the ChartWindow's constructor grafico=new Grafico() ................ add(grafico.pannelloGrafico); add(grafico.pannelloVolumi); Tell me if you need more information, thank you very much :-)

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  • Hibernate: how to maintain insertion order

    - by jwaddell
    I have a list of entities where creation order is important, but they do not contain a timestamp to use for sorting. Entities are added to the end of the list as they are created so they will be ordered correctly in the list itself. After persisting the list using Hibernate the entities appear in the database table in the order that they were created. However when retrieving the list using a new Hibernate session the list is now in reverse order of insertion/creation. Is this expected behaviour? Is there any way to retrieve the list in the same order as it appears in the table? The primary key is a UUID, and the list of entities should always have been created on the same IP address and JVM. This mean sorting by UUID is a possibility but I'd rather not make assumptions. Another possibility is if the list is guaranteed to always come out in reverse order I could always just work through it backwards.

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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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  • recommendations for firestorm dao replacement

    - by Casey
    I have taken over some code that has been using the Firestorm DAO code generator from CodeFutures. I believe that the license for this is going to be up soon, and was wondering if anyone could recommend any alternatives, open source or not, so that I can get an idea of what's out there to better make a decision.

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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 to check whether the tab is active or not in JTabbedPane?

    - by Supereme
    Hi, How to check whether a tab in JTabbedPane instance is active or not, in the class of the tab(nested class) itself and not in the enclosing class? I know that there is a method 'booloean isEnabledAt(int index)'; but this method can only be called in the enclosing class whereas I want to check whether the tab is currently selected or not in the tab class (nested class) itself. Can anybody please suggest me something? Thank you!

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