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  • Using mail servers in java

    - by sword101
    greeting all i want to use a mail server where the users send emails to it and then i parse this emails then do some action please suggest me what mail server to be used and where to start some links,tutorials,guide is very appreciated .

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  • Question about layout in java.

    - by extro
    I have two panels main_panel and child_panel. I have set layout for main_panel by using "main_panel.setLayout(flowlayout)" and added child_panel in main_panel by using "main_panel.add(child_panel)". This child_panel gets added to main_panel but its position is at the cross-section of horizontal midpoint and top vertical section of screen. But I want child_panel to be at the top left corner, something I could have done by using "child_panel.setlocation(a,b)" method, if I have set the Layout of main_panel as NULL. I have used flowlayout here because I want components in the JPanel to keep adjusting with the size of JFrame. So question is, can I add child_panel to main_panel at the exact location I want, even if I set the Layout of main_panel as not NULL.

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  • Java ternary operator and boxing Integer/int?

    - by Markus
    I tripped across a really strange NullPointerException the other day caused by an unexpected type-cast in the ternary operator. Given this (useless exemplary) function: Integer getNumber() { return null; } I was expecting the following two code segments to be exactly identical after compilation: Integer number; if (condition) { number = getNumber(); } else { number = 0; } vs. Integer number = (condition) ? getNumber() : 0; . Turns out, if condition is true, the if-statement works fine, while the ternary opration in the second code segment throws a NullPointerException. It seems as though the ternary operation has decided to type-cast both choices to int before auto-boxing the result back into an Integer!?! In fact, if I explicitly cast the 0 to Integer, the exception goes away. In other words: Integer number = (condition) ? getNumber() : 0; is not the same as: Integer number = (condition) ? getNumber() : (Integer) 0; . So, it seems that there is a byte-code difference between the ternary operator and an equivalent if-else-statement (something I didn't expect). Which raises three questions: Why is there a difference? Is this a bug in the ternary implementation or is there a reason for the type cast? Given there is a difference, is the ternary operation more or less performant than an equivalent if-statement (I know, the difference can't be huge, but still)?

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  • Java Clock Assignment

    - by Mike S
    For my assignment we are suppose to make a clock. We need variables of hours, minutes, and seconds and methods like setHours/getHours, setMinutes/getMinutes, setSeconds/getSeconds. Now the parts of the assignment that I am having trouble on is that we need a addClock() method to make the sum of two clock objects and a tickDown() method which decrements the clock object and a tick() method that increments a Clock object by one second. Lastly, the part where I am really confused on is, I need to write a main() method in the Clock class to test the functionality of your objects with a separate Tester class with a main() method. Here is what I have so far... public class Clock { private int hr; //store hours private int min; //store minutes private int sec; //store seconds //Default constructor public Clock () { setClock (0, 0, 0); } public Clock (int hours, int minutes, int seconds) { setTimes (hours, minute, seconds); } public void setClock (int hours, int minutes, int seconds) { if(0 <= hours && hours < 24) { hr = hours; } else { hr = 0; } if(0 <= minutes && minutes < 60) { min = minutes; } else { min = 0; } if(0 <= seconds && seconds < 60) { sec = seconds; } else { sec = 0; } } public int getHours ( ) { return hr; } public int getMinutes ( ) { return min; } public int getSeconds ( ) { return sec; } //Method to increment the time by one second //Postcondition: The time is incremented by one second //If the before-increment time is 23:59:59, the time //is reset to 00:00:00 public void tickSeconds ( ) { sec++; if(sec > 59) { sec = 0; tickMinutes ( ); //increment minutes } } public void tickMinutes() { min++; If (min > 59) { min = 0; tickHours(); //increment hours } } public void tickHours() { hr++; If (hr > 23) hr = 0; } }

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  • Java: Set<E> collection, where items are identified by its class

    - by mschayna
    I need Set collection, where its items will be identified by items class. Something like ReferenceIdentityMap from Appache Collections, but on class scope i.e. two different instances of same class must be identified as same in this collection. You know, it is a violation of equals()/hashCode() identity principle but in occasional use it makes sense. I have done this in simple class backing with Map<Class<? extends E>, E>, but due to simplicity it doesn't implement Set<E>. There may be a more elegant solution, decorator of any Set<E> would be great. Is there any implementation of such collection there (Apache/Google/something/... Collections)?

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  • JTable horizontal scrollbar in Java

    - by Mr CooL
    Is there any way to enable horizontal scrollbar whenever necessary?? The situation was as such: I've a JTable on Netbeans, one of the cells, stored a long length of data. Hence, I need to have horizontal scrollbar. Anyone has idea on this? THanks in advance for any helps..

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  • Java HashSet using a specified method

    - by threenplusone
    I have a basic class 'HistoryItem' like so: public class HistoryItem private Date startDate; private Date endDate; private Info info; private String details; @Override public int hashCode() { int hash = (startDate == null ? 0 : startDate.hashCode()); hash = hash * 31 + (endDate == null ? 0 : endDate.hashCode()); return hash; } } I am currently using a HashSet to remove duplicates from an ArrayList on the startDate & endDate fields, which is working correctly. However I also need to remove duplicates on different fields (info & details). My question is this. Is there a way to specify a different method which HashSet will use in place of hashCode()? Something like this: public int hashCode_2() { int hash = (info == null ? 0 : info.hashCode()); hash = hash * 31 + (details == null ? 0 : details.hashCode()); return hash; } Set<HistoryItem> removeDups = new HashSet<HistoryItem>(); removeDups.setHashMethod(hashCode_2); Or is there another way that I should be doing this?

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  • Java threadpool functionality

    - by cpf
    Hi stackoverflow, I need to make a program with a limited amount of threads (currently using newFixedThreadPool) but I have the problem that all threads get created from start, filling up memory at alarming rate. I wish to prevent this. Threads should only be created shortly before they are executed. e.g.: I call the program and instruct it to use 2 threads in the pool. The program should create & launch the first 2 Threads immediately (obviously), create the next 2 to wait for the previous 2, and at that point wait until one or both of the first 2 ended executing. I thought about extending executor or FixedThreadPool or such. However I have no clue on how to start there and doubt it is the best solution. Easiest would have my main Thread sleeping on intervals, which is not really good either... Thanks in advance!

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  • Java - SwingWorker - problem in done() method

    - by Yatendra Goel
    I am using javax.swing.SwingWorker for the first time. I want to update a JLabel from the interim result published by the swing worker as follows: publish("Published String"); Now to update the JLabel, I have coded the following: process(List<String> chunks) { if (chunks.size() > 0) { String text = chunks.get(chunks.size() - 1); label.setText(text); } } The above code works but my problem(or to be more specific, my doubt) is as follows: The above swing worker task is an annonymous inner class so it can access label field. But what if I want to make the swing worker class a non-inner class. Should I need to pass label as an argument to the constructor of swing worker class so that the process() method can access. Or Is there any other way? What approach does other developer follow to update UI components from the swing worker class' result when the swing worker class is not an inner class?

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  • String replaceAll method (Java)

    - by Mr CooL
    I have following problem, Code: String a="Yeahh, I have no a idea what's happening now!"; System.out.println(a); a=a.replaceAll("a", ""); System.out.println(a); Before removing 'a', result: Yeahh, I have no a idea what's happening now! Actual Result: After removing 'a', result: Yehh, I hve no ide wht's hppening now! Desired Result: Yeahh, I have no idea what's happening now! Anyone can gimme some advices to achieve my desired result?

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  • How to combine array list string in java ?

    - by tiendv
    I have some arraylist string with keyword inside like that ! A windows is arraylist string with keyword is bold Struct of window : 9 words before + keyword + 9 words after You can see some window overlaping How to i combine that arraylist to receive like that : Thanks

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  • "Dynamic" java validation framework?

    - by pihentagy
    AFAIK JSR-303 is the standard bean validation system. I don't know whether it could do validations like this (I guess no): if an object has a deleted flag set, you cannot modify the object you cannot change the start date property, after the date is passed you cannot decrease some integer properties in the bean So how can I handle validations, which depend on the previous state of an object? I would like to solve problems like that in hibernate3.5 - spring3 - JPA2 environment. Thanks My solution was to mess with hibernate, reload the object to see the old state (after evicting the new object). This time I need some smarter solution...

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  • how to generate a random String? in java

    - by chandra wibowo
    hi everyone, i have an object called Student, and it has studentName, studentId, studentAddress, etc. for the studentId, i have to generate random string consist of seven numeric charaters, eg. studentId = getRandomId(); studentId = "1234567" <-- from the random generator. and i have to make sure that there is no duplicate id. thanks in advance

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  • java asynchronous task.

    - by Tony
    For some of HTTP requests from clients, there was very complex business logic in server side. Some of these business logics doesn't require to response to the client immediately, like sending a email to somebody. Can I put those tasks in an asynchronous method.

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  • Java - JPA - @Basic and @Embedded

    - by Yatendra Goel
    I am learning JPA from this tutorial. I have some confusions in understanding the following annotations: @Basic @Embedded Fields of an embeddable type default to persistent, as if annotated with @Embedded. If the fields of embeddable types defualt to persistent, then why would we need @Embedded

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  • Java/swing: console component?

    - by Jason S
    I am looking for a component I can use in Swing that acts as a GUI console which has a text area with scrollbars that can be set to a particular font has an InputStream and an OutputStream that a host application can obtain accepts keyboard input, prints it onto the end of the console text, and sends that input to the InputStream prints the OutputStream text to the end of the console has some kind of FIFO-ish property whereby the amount of text displayed in the console can be limited by automatically discarding the oldest text, when appropriate allows copy (but not cut or paste or any other editing) of the console text to the system clipboard This is kind of like the Console tab in Eclipse. Are there any good libraries that provide this?

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  • Not receiving all message via TCP in Java?

    - by javatcp
    I have a tcp socket sending three lines like this out2.println("message1\n"); out2.println("message2\n"); out2.println("message3\n"); and another tco socket receiving and displaying these messages like this System.out.println(in.readLine()); System.out.println(in.readLine()); System.out.println(in.readLine()); but only the first message is recieved and displayed, anything I send after that is not.

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  • Deleting from arraylist and exporting back to .buab file(Java)

    - by Dave
    Ive made an address book. I can currently write to the arraylist and save it back to the .buab file, but I cant delete from the arraylist and export it back to the .buab file? Im pretty much stuck on this. Im able to retrive contacts from the .buab and scroll through them using the JTextFields and buttons ive created. Any help will be dearly appreciated. Ive set up seprate classes for all operations (newcontacts, nextcontact etc). If you need the code posted let me know.. Cheers Dave

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  • Mimic an HTTPRequest and HTTPResponse object in Java

    - by Ankur
    How do I mimic an HTTPServletRequest and HTTPServletResponse object. The reason is I want to test the behaviour of some servlets. I know JUnit probably provides this functionality but I don't know how to use it (I will learn soon) and need to do this reasonably quickly. HTTPServletRequest and HTTPServletResponse are both interfaces so they can't be instantiated. There is a HttpServletRequestWrapper which implements HttpServletRequest but it doesn't seem to have any setParameter() type methods and HttpServletResponse doesn't seem to have any implementing classes at all. How can I test my code by passing a suitable HttpServletRequest object and then checking that the received HttpServletResponse object matches what I expect?

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  • Loading data in constructors and not in constructors [JAVA]

    - by Richeve S. Bebedor
    i just want to know the difference between loading the data inside the constructor and loading the data outside the constructor but not inside any methods example: Loading inside constructor public class Model{ Object testobject; public Model(){ testobject=new Object(); } } VS example: Loading outside constructor public class Model{ Object testobject=new Object(); public Model(){ } }

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  • communication between threads in java

    - by Noona
    How can I make a thread run only if the other thread is running too, meaning, if I return from run in one thread, then I want the other to stop running too, my code looks something like this: ClientMessageHandler clientMessagehandler = new ClientMessageHandler(); ServerMessageHandler serverMessagehandler = new ServerMessageHandler(); Thread thread1 = new Thread(serverMessagehandler); Thread thread2 = new Thread(clientMessagehandler); thread2.start(); thread1.start(); i want to cause thread1 to stop running when thread2 stops running. thanks

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