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  • returning a Void object

    - by Robert
    What is the correct way to return a Void type, when it isn't a primitive? Eg. I currently use null as below. interface B<E>{ E method(); } class A implements B<Void>{ public Void method(){ // do something return null; } }

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  • J2ME development and native API

    - by Attilah
    Is it possible to write a mobile application with J2ME and whenever we want to implement a functionality not offered by J2ME call native mobile API ? (kind of like what is done with .NET, whenever you need something not provided, you just call the Win32 API from the .NET platform).

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  • How do I remove an old JPanel and add a new one?

    - by Roman
    I would like to remove an old JPanel from the Window (JFrame) and add a new one. How should I do it? I tried the following: public static void showGUI() { JFrame frame = new JFrame("Colored Trails"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.add(partnerSelectionPanel); frame.setSize(600,400); frame.setVisible(true); } private static void updateGUI(final int i, final JLabel label, final JPanel partnerSelectionPanel) { SwingUtilities.invokeLater( new Runnable() { public void run() { label.setText(i + " seconds left."); } partnerSelectionPanel.setVisible(false); \\ <------------ } ); } So, my code update the "old" JPanel and them it makes the whole JPanel invisible. It was the idea. But it does not work. The compiler complains about the line indicated with "<------------". It writes: <identifier> expected, illegal start of type.

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  • How to use CellRenderer for GregorianCalendar?

    - by HansDampf
    So I have been trying to use the example from Tutorial and change it so it fits my program. The getColumnValue method returns the object that holds the information that is supposed to be displayed. Is this the way to go or should it rather return the actual String to be displayed. I guess not because that way I would mix the presentation with the data, which I was trying to avoid. public class IssueTableFormat implements TableFormat<Appointment> { public int getColumnCount() { return 6; } public String getColumnName(int column) { if(column == 0) return "Datum"; else if(column == 1) return "Uhrzeit"; else if(column == 2) return "Nummer"; else if(column == 3) return "Name"; else if(column == 4) return "letzte Aktion"; else if(column == 5) return "Kommentar"; throw new IllegalStateException(); } public Object getColumnValue(Appointment issue, int column) { if(column == 0) return issue.getDate(); else if(column == 1) return issue.getDate(); else if(column == 2) return issue.getSample(); else if(column == 3) return issue.getSample(); else if(column == 4) return issue.getHistory(); else if(column == 5) return issue.getComment(); throw new IllegalStateException(); } } The column 0 and 1 contain a GregorianCalendar object, but I want column 0 to show the date and 1 to show the time. So I know using cellRenderers can help here. This is what I tried. public class DateRenderer extends DefaultTableCellRenderer { public DateRenderer() { super(); } public void setValue(Object value) { GregorianCalendar g =(GregorianCalendar) value; value=g.get(GregorianCalendar.HOUR); } } But the cell doesnt show anything, what is wrong here?

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  • Hibernate violation error

    - by sarah
    Hi All, I am having a designation table with d_name as primary key which i am using in user table as foreign key reference .I am using hbm for mapping in designation hbm i have id defined as d_name mapped to database column .I am getting a error saying "integrity constraint violation(user_designation_fk) parent key not found. " Where am i going wrong /this error is coming while i am tring to add a user selecting a designation reading from designation table.

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  • Wait for inline thread to complete before moving to next method...

    - by Tyler
    Hello, I have an android app where I am doing the following: private void onCreate() { final ProgressDialog dialog = ProgressDialog.show(this, "Please wait..", "Doing stuff..", true); new Thread() { public void run() { //do some serious stuff... dialog.dismiss(); } }.start(); stepTwo(); } And I would like to ensure that my thread is complete before stepTwo(); is called. How can I do this? Thanks!

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  • Best way of invoking getter by reflection

    - by Javi
    Hello, I need to get the value of a field with a specific annotation, So with reflection I am able to get this Field Object. The problem is that this field will be always private though I know in advance it will always have a getter method. I know that I can use setAccesible(true) and get its value (when there is no PermissionManager), though I prefer to invoke its getter method. I know that I could look for the method by looking for "get+fieldName" (though I know for example for boolean fields are sometimes named as "is+fieldName"). I wonder if there is a better way to invoke this getter (many frameworks use getters/setters to access the attributes so maybe they do in another way). Thanks

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  • How much memory does a hashtable use?

    - by Michael
    Would a hashtable/hashmap use a lot of memory if it only consists of object references and int's? As for a school project we had to map a database to objects (that's what being done by orm/hibernate nowadays) but eager to find a good way not to store id's in objects in order to save them again we thought of putting all objects we created in a hashmap/hashtable, so we could easily retrieve it's ID. My question is if it would cost me performance using this, in my opinion more elegant way to solve this problem.

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  • What is corresponding Cron expression to fire in every X seconds, where X > 60?

    - by giolekva
    I want my jobs to execute in every X seconds, there's one to one matching between job and X. Also during runtime there can be registered new jobs with their own intervals. I've tried to write cron expression for such scenarios, but in documentation there's written that value of seconds can't be more than 69. So cron expression like this: "0/63 * * * * ?" isn't valid. At first sight solution of that problem seemed to be expression like this: "0/3 0/1 * * * ?", but it means completely different thing: trigger job in every three second of every minute. Can you suggest what is the right solution (cron expression) for that? I know I could use just simple timers, but I've to use cron jobs using Quartz.

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  • Format String become 0001, 0010 etc

    - by trycatch4j
    Hi all.., I have number : 1, 2, 3, 4, 10 But I wanna print that number 0001 0002 0003 0004 0010 I have search in google, the keyword is number format. but I've got nothing, I just get, frmat decimal such ass 1,000,000.00. hope you can suggest me a reference or give me some problem solving. Thanks,

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  • specifying ThreadPoolExecutor problem

    - by Sarmun
    Is there any way to create Executor that will have always at least 5 threads, and maximum of 20 threads, and unbounded queue for tasks (meaning no task is rejected) I tried new ThreadPoolExecutor(5, 20, 60L, TimeUnit.SECONDS, queue) with all possibilities that I thought of for queue: new LinkedBlockingQueue() // never runs more than 5 threads new LinkedBlockingQueue(1000000) // runs more than 5 threads, only when there is more than 1000000 tasks waiting new ArrayBlockingQueue(1000000) // runs more than 5 threads, only when there is more than 1000000 tasks waiting new SynchronousQueue() // no tasks can wait, after 20, they are rejected and none worked as wanted.

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  • Is it possible to Hide Text through a Style?

    - by Sandro
    I currently have a JTextPane that will be displaying text coming in from different streams. The way that the user can tell which stream the text came from is that the text from each stream has a different Style to it. Is there a way to make a Style that will hide the text so that I can filter out different pieces of text? Thank you.

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  • Generic factory of generic containers

    - by Feuermurmel
    I have a generic abstract class Factory<T> with a method createBoxedInstance() which returns instances of T created by implementations of createInstance() wrapped in the generic container Box<T>. abstract class Factory<T> { abstract T createInstance(); public final Box<T> createBoxedInstance() { return new Box<T>(createInstance()); } public final class Box<T> { public final T content; public Box(T content) { this.content = content; } } } At some points I need a container of type Box<S> where S is an ancestor of T. Is it possible to make createBoxedInstance() itself generic so that it will return instances of Box<S> where S is chosen by the caller? Sadly, defining the function as follows does not work as a type parameter cannot be declared using the super keyword, only used. public final <S super T> Box<S> createBoxedInstance() { return new Box<S>(createInstance()); } The only alternative I see, is to make all places that need an instance of Box<S> accept Box<? extends S> which makes the container's content member assignable to S. Is there some way around this without re-boxing the instances of T into containers of type Box<S>? (I know I could just cast the Box<T> to a Box<S> but I would feel very, very guilty.)

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  • Hibernate OneToMany and ManyToOne confusion! Null List!

    - by squizz
    I have two tables... For example - Company and Employee (let's keep this real simple) Company( id, name ); Employee( id, company_id ); Employee.company_id is a foreign key. My entity model looks like this... Employee @ManyToOne(cascade = CascadeType.PERSIST) @JoinColumn(name = "company_id") Company company; Company @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER) @JoinColumn(name = "company_id") List<Employee> employeeList = new ArrayList<Employee>(); So, yeah I want a list of employees for a company. When I do the following... Employee e = new Employee(); e.setCompany(c); //c is an Company that is already in the database. DAO.insertEmployee(e); //this works fine! If I then get my Company object it's list is empty! Ive tried endless different ways from the Hibernate documentation! Obviously not tried the correct one yet! I just want the list to be populated for me or find out a sensible alternative. Help would be greatly appreciated, thanks!

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  • Connecting to an RMI server that sits behind a firewall?

    - by MalcomTucker
    I know my RMI app works correctly - it works fine when the server is on localhost and inside the LAN but when connecting to an external RMI server it fails when trying to make stub calls So the server is bound to localhost (an internal IP - 192.168.1.73) but the client is specifying an external IP (45.4.234.56) - which then gets forwarded to the internal server. How do you resolve this problem? thanks

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  • Request/Response objects

    - by Dan
    I'm planning on using CXF's rest implementation. I'm thinking of simply annotating my entity classes with jaxb annotations, such as @XmlRootElement, in order to create response objects. The benefit being avoidance of code duplication. As for the (client) request object, which will be used by a separate web app, I'm thinking of 'copying' the entity classes, removing the orm annotations, and adding jaxb annotations. Based on the above: Are there any dangers of creating request/response objects from entity classes? My entity classes contain relational properties, if I were to annotate them with @XmlRootElement, how can I stop the relational properties from being added (or considered apart of) to the response object? Is there a better/easier way to create request objects rather than copying the entity classes, removing/adding annotations?

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  • Allow Incorrect Package Name in Eclipse

    - by SamBeran
    I have some classes in my current project which have the wrong package declaration (they are in the wrong folder for their declared package.) Unfortunately, fixing the problem by moving the class is not an option. Is there a way I can get eclipse to ignore the error?

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  • How can we compute the LAST page with JPA?

    - by Kevin
    I would like to implement pagination in my Servlet/EJB/JPA-Hibernate project, but I can't figure out how only one page from the query and know the number of pages I must display I use setFirstResult(int first) ; setMaxResults(int max) ; and that's working alright, but how can I know how many pages I will have in total? (Hibernate is my JPA provider, but I would prefer using only JPA if possible) UPDATE: COUNT() seems to be the better/easiest solution; but what can be the cost of SELECT COUNT(*) FROM ... in comparison with executeQuery("SELECT * FROM ...).getListResult().size() ?

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  • What exactly is GRASP's Controller about?

    - by devoured elysium
    What is the idea behind Grasp's Controller pattern? My current interpretation is that sometimes you want to achieve something that needs to use a couple of classes but none of those classes could or has access to the information needed to do it, so you create a new class that does the job, having references to all the needed classes(this is, could be the information expert). Is this a correct view of what Grasp's Controller is about? Generally when googling or SO'ing controller, I just get results about MVC's (and whatnot) which are topics that I don't understand about, so I'd like answers that don't assume I know ASP.NET's MVC or something :( Thanks

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