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  • Can you tell on runtime if you're running java from within a jar?

    - by Dikla
    Hi, I have an application that some of my users run from Eclipse, and others run it by using a jar file. I want some actions to be done when running from within the jar, but I don't want them to be done when running from Eclipse. Is there a way to know on runtime whether the current application is running from within a jar? Thanks! Dikla

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  • What features do you expect from a Java (Rich) Client Framework?

    - by Peter Walser
    I'm intending to design (and provide a reference implementation for) a new Swing Rich Client Framework. My job and personal experience covers many project-specific Swing client frameworks as well as the Eclipse RCP, and every one of them had some original and clever concepts, but also drawbacks and rigid realizations. My plan is to incorporate the best of those concepts and features into a new framework whose core is very open and extendable. For my must-have-features list, I'm counting on your input and hope you can share some concept pearls & diamonds you've encountered in other frameworks, or features you always wanted to have or have in a better way. The framework is intended for very simple to very complex and sophisticated projects for clients that need full i18n for richt clients that execute some or all of the non-presentation logic on the server to be very lightweight to be easy to learn and use Thanks in advance for sharing your insights :)

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  • Is this use of PreparedStatements in a Thread in JAVA correct?

    - by Gormcito
    I'm still an undergrad just working part time and so I'm always trying to be aware of better ways to do things. Recently I had to write a program for work where the main thread of the program would spawn "task" threads (for each db "task" record) which would perform some operations and then update the record to say that it has finished. Therefore I needed a database connection object and PreparedStatement objects in or available to the ThreadedTask objects. This is roughly what I ended up writing, is creating a PreparedStatement object per thread a waste? I thought static PreparedStatments could create race conditions... Thread A stmt.setInt(); Thread B stmt.setInt(); Thread A stmt.execute(); Thread B stmt.execute(); A´s version never gets execed.. Is this thread safe? Is creating and destroying PreparedStatement objects that are always the same not a huge waste? public class ThreadedTask implements runnable { private final PreparedStatement taskCompleteStmt; public ThreadedTask() { //... taskCompleteStmt = Main.db.prepareStatement(...); } public run() { //... taskCompleteStmt.executeUpdate(); } } public class Main { public static final db = DriverManager.getConnection(...); }

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  • Java Persistence: Cast to something the result of Query.getResultList() ?

    - by GuiSim
    Hey everyone, I'm new to persistence / hibernate and I need your help. Here's the situation. I have a table that contains some stuff. Let's call them Persons. I'd like to get all the entries from the database that are in that table. I have a Person class that is a simple POJO with a property for each column in the table (name, age,..) Here's what I have : Query lQuery = myEntityManager.createQuery("from Person") List<Person> personList = lQuery.getResultList(); However, I get a warning saying that this is an unchecked conversion from List to List<Person> I thought that simply changing the code to Query lQuery = myEntityManager.createQuery("from Person") List<Person> personList = (List<Person>)lQuery.getResultList(); would work.. but it doesn't. Is there a way to do this ? Does persistence allow me to set the return type of the query ? (Through generics maybe ? )

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  • How to set session timeout dinamically in java web applications?

    - by Jonathas Carrijo
    Hi, I need to give my user a web interface to change the session timeout interval. So, each installation of the application might have different timeouts for their sessions, but they web.xml cannot be different. Is there a way to set the session timeout programatically, so that I could use, say, ServletContextListener.contextInitialized() to read the configured interval and set it upon application startup? Thanks a lot.

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  • How come JFrame window size in Java does not produce the size of window specified?

    - by typoknig
    Hi all, I am just messing around trying to make a game right now, but I have had this problem before too. When I specify a specific window size (1024 x 768 for instance) the window produced is just a little larger than what I specified. Very annoying. Is there a reason for this? How do I correct it so the window created is actually the size I want instead of being just a little bit bigger? Up till now I have always just gone back and manually adjusted the size a few pixels at a time until I got the result I wanted, but that is getting old. If there was even a formula I could use that would tell me how many pixels I needed to add/subtract from my my variable that would be excellent! P.S. I don't know if my OS could be a factor in this, but I am using W7X64. private int windowWidth = 1024; private int windowHeight = 768; public SomeWindow() { this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); this.setSize(windowWidth, windowHeight); this.setResizable(false); this.setLocation(0,0); this.setVisible(true); }

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  • Is there a way to launch an aggressive and complete garbage collection in Java?

    - by Gnoupi
    For memory optimization reasons, I'm launching myself the garbage collector during profiling, to check if objects are correctly cleaned after disposing of them. The call to garbage collector is not enough, though, and it seems that there is no guarantee of what it will clean. Is there a way to call it, to be sure it will recover as much as it can, in profiling conditions (this would have no point in production, of course)? Or is "calling it several times" the only way to be "almost sure"? Or did I simply misunderstand something about the Garbage Collector?

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  • Java. Writing a matrix in a file using column information. ( matrix transposition )

    - by Dmitry
    Hello, everybody! I have a file in which a matrix is stored. This file has a RandomAccessFile type. This matrix is stored by columns. I mean that in an i-th row of this matrix an i-th column (of a real matrix) is stored. There is an example: i-th row: 1 2 3 4 (in the file). That means that the real matrix has an i-th column: (1 2 3 4)(is transposed). I need to save this matrix in a natural way (by rows) in a new file, which I will then open with FileReader and display with TextArea. Do you know, how to do that? If so, please help =)

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  • How can two programs talk to each other in Java?

    - by Arnon
    I want to ?reduce? the CPU usage/ROM usage/RAM usage - generally?, all system resources that my app uses - who doesn't? :) For this reason I want to split the preferences window from the rest of the application, and let the preferences window to run as ?independent? program. The preferences program ?should? write to a Property file(not a problem at all) and to send a "update signal" to the main program - which means it should call the update method (that i wrote) that found in the Main class. How can I call the update method in the Main program from the preferences program? To put it another way, is a way to build preferences window that take system resources just when the window appears? Is this approach - of separating programs and let them talk to each other (somehow) - the right approach for speeding up my programs?

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  • Remove successive 0th entries in args[] for a Java command line interface?

    - by Bill IV
    I recall seeing, somewhere, an example that stepped through String args[] by deleting the lowest numbered value(s) public static void main( String args[]) { while (args.length > 0 ) { // do something and obliterate elements from args[] } } Obviously, a variable tracking current position in args and compared to args.length will do it; or an ArrayList made from args[]'s contents, with argsAL.size(). Am I mis-remembering an ArrayList example? I know this is a borderline question, the likely answer is, "No, there isn't and there shouldn't be either!". Maybe I'm over-focused... Bill

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  • Convert bit vector (array of booleans) to an integer, and integer to bit vector, in Java.

    - by dreeves
    What's the best way to unstub the following functions? // Convert a bit-vector to an integer. int bitvec2int(boolean[] b) { [CODE HERE] } // Convert an integer x to an n-element bit-vector. boolean[] int2bitvec(int x, int n) { [CODE HERE] } Or is there a better way to do that sort of thing than passing boolean arrays around? This comes up in an Android app where we need an array of 20 booleans to persist and the easiest way to do that is to write an integer or string to the key-value store. I'll post the way we (Bee and I) wrote the above as an answer. Thanks!

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  • java: how to make srollable panel with radio button and labels inside?

    - by Lucia
    Hi, I got a JScrollPane in which I want to place a list of radio buttons and labels. My problem is the panel doesn't scroll, I suppose it's because i didn't set a viewport, but how can I set it when I have to many components? My code looks something like this: JScrollPane panel = new JScrollPane(); JRadioButton myRadio; JLabel myLabel; for(int i = 0; i<100; i++){ myRadio = new JRadioButton(); myLabel = new JLabel("text"); panel.add(myRadio); panel.add(myLabel); } Thanks.

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  • Why am I getting a Java NoSuchPortException when the port exists?

    - by user258526
    Got the following production code below, I'm using it for a new driver. portName is COM4 and this port exists on the PC (and I can connect to it with hyperterminal), so why does Javacomm throw a NoSuchPortException? COM4 shows up fine in device mgr. too final String portName = getSerialPort(); try { final CommPortIdentifier id = CommPortIdentifier.getPortIdentifier(portName); port = (SerialPort) id.open(getName(), 1000); } catch (NoSuchPortException nspe) { report(SeverityCode.LEVEL2, getName(), "PIN Pad is not connected to " + portName + " port, or the port does not exist."); return; } catch (PortInUseException piue) { report(SeverityCode.LEVEL2, getName(), portName + " port is already in-use by some other device. Reason: " + piue.getMessage()); return; }

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  • String Index Out Of Bound Exception error

    - by Fd Fehfhd
    Im not really sure why a am getting this error. But here is my code it is meant to test palindromes disregarding punctuation. So here is my code import java.util.Scanner; public class PalindromeTester { public static void main(String [] args) { Scanner kb = new Scanner(System.in); String txt = ""; int left; int right; int cntr = 0; do { System.out.println("Enter a word, phrase, or sentence (blank line to stop):"); txt = kb.nextLine(); txt = txt.toLowerCase(); char yP; String noP = ""; for (int i = 0; i < txt.length(); i++) { yP = txt.charAt(i); if (Character.isLetterOrDigit(txt.charAt(yP))) { noP += yP; } } txt = noP; left = 0; right = txt.length() -1; while (txt.charAt(left) == txt.charAt(right) && right > left) { left++; right--; } if (left > right) { System.out.println("Palindrome"); cntr++; } else { System.out.println("Not a palindrome"); } } while (!txt.equals("")); System.out.println("You found " + cntr + " palindromes. Thank you for using palindromeTester."); } } And if i test it and then i put enter so it will tell me how many palindromes you found the error i am getting is javav.lang.StringIndexOutOfBoundException : String index out of range 0 at PalindromeTester.main(PalindromeTester.java:38) and line 28 is while (txt.charAt(left) == txt.charAt(right) && right > left) Thanks for the help in advance

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  • How to access a subset of XML data in Java when the XML data is too large to fit in memory?

    - by Michael Jones
    What I would really like is a streaming API that works sort of like StAX, and sort of like DOM/JDom. It would be streaming in the sense that it would be very lazy and not read things in until needed. It would also be streaming in the sense that it would read everything forwards (but not backwards). Here's what code that used such an API would look like. URL url = ... XMLStream xml = XXXFactory(url.inputStream()) ; // process each <book> element in this document. // the <book> element may have subnodes. // You get a DOM/JDOM like tree rooted at the next <book>. while (xml.hasContent()) { XMLElement book = xml.getNextElement("book"); processBook(book); } Does anything like this exist?

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  • How to implement event listener in background of the main program in java?

    - by Johny
    Hi im a beginner so sorry for my question if it sounds naive. I want to implement a thread that runs in the background and listens all the time. By listening i mean, say it keeps check on a value returned from main thread and if the vaue exceeds certain figure, it executes some method, or say exits the program. If you could give me some idea or at least refer me to something useful, that'll be great.

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  • Java 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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  • Multithreaded java cache for objects that are heavy to create ?

    - by krosenvold
    I need a cache some objects with fairly heavy creation times, and I need exactly-once creation semantics. It should be possible to create objects for different CacheKeys concurrently. I think I need something that (under the hood) does something like this: ConcurrentHashMap<CacheKey, Future<HeavyObject>> Are there any existing open-source implementations of this that I can re-use ?

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