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  • Read from one large file and write to many (tens, hundreds, or thousands) files in Java?

    - by Rudiger
    I have a large-ish file (4-5 GB compressed) of small messages that I wish to parse into approximately 6,000 files by message type. Messages are small; anywhere from 5 to 50 bytes depending on the type. Each message starts with a fixed-size type field (a 6-byte key). If I read a message of type '000001', I want to write append its payload to 000001.dat, etc. The input file contains a mixture of messages; I want N homogeneous output files, where each output file contains only the messages of a given type. What's an efficient a fast way of writing these messages to so many individual files? I'd like to use as much memory and processing power to get it done as fast as possible. I can write compressed or uncompressed files to the disk. I'm thinking of using a hashmap with a message type key and an outputstream value, but I'm sure there's a better way to do it. Thanks!

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  • Java IO (javase 6)- Help me understand the effects of my sample use of Streams and Writers...

    - by Daddy Warbox
    BufferedWriter out = new BufferedWriter( new OutputStreamWriter( new BufferedOutputStream( new FileOutputStream("out.txt") ) ) ); So let me see if I understand this: A byte output stream is opened for file "out.txt". It is then fed to a buffered output stream to make file operations faster. The buffered stream is fed to an output stream writer to bridge from bytes to characters. Finally, this writer is fed to a buffered writer... which adds another layer of buffering? Hmm...

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  • Reports in Java. What tool to use?

    - by Tom
    Hi, I need to create some reports, in different formats (xls, pdf, rtf). I am currently using JasperReports, in conjunction with IReport. I have no major complaints about it (except for the cases when IReport messes up my xml files), but i've been having some problems with it, when exporting to xls files and with some "special" characters, such as '&'. Is there a widely use alternative? Is JasperReports the right choice?

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  • How do i generate a random integer between min and max in java?

    - by David
    What method returns a random int between a min and max? Or does no such method exist? what i'm looking for is something like this: NAMEOFMETHOD (min, max) (where min and max are ints) that returns soemthing like this: 8 (randomly) if such a method does exist could you please link to the relevant documentation with your answer. thanks.

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  • why PaintComponent event in Java happen everytime I use its Graphics Event?

    - by Pooya
    Consider this code: public class StateChartPanel extends JPanel { private LightContext LC; public StateChartPanel(LightContext lc){ LC=lc; } public void paintComponent( Graphics G ){ super.paintComponent( G ); LC.DrawStateChart((Graphics2D)G); } } StateChartPanel is a panel to draw something (a state chart). It sends its Graphics object to LC which use it to draw shapes but whenever it draws something the PaintComponent event of StateChartPanel happens again and it causes my application to hang.

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  • Are there any good videos out there on Java Design Patterns?

    - by Becky Reamy
    My team would like to spend some time at lunch learning design patterns. Previously, we watched some videos on Javascript which we found very useful as a way to start discussions. We would like to do the same thing with design patterns so that we don't have to spend a lot of time (outside of work) researching individual patterns in order to give a presentation. I did a little searching and came up fairly empty handed. Any help would be appreciated. It doesn't even have to be a video, even something that we can listen to (maybe a book on tape even).

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  • How can I print the argument value that caused Exception in Java?

    - by Sanoj
    I am writing a parser for csv-files, and sometimes I get NumberFormatException. Is there an easy way to print the argument value that caused the exception? For the moment do I have many try-catch blocks that look like this: String ean; String price; try { builder.ean(Long.parseLong(ean)); } catch (NumberFormatException e) { System.out.println("EAN: " + ean); e.printStackTrace(); } try { builder.price(new BigDecimal(price)); } catch (NumberFormatException e) { System.out.println("Price: " + price); e.printStackTrace(); } I would like to be able to write something like: try { builder.ean(Long.parseLong(ean)); } catch (NumberFormatException e) { e.printMethod(); // Long.parseLong() e.printArgument(); // should print the string ean "99013241.23" e.printStackTrace(); } Is there any way that I at least can improve my code? And do this kind of printing/logging more programmatically?

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  • How to mark messages that are received by an java application using javax Mail Api?

    - by telebog
    I want to create an application that gets all e-mails from an e-mail account using imap. When I first run the application I get all mails, than if I run it again I want to mark the messages that was read before so I can receive only new messages. I found that Message Object contains Flags(System Flags and User defined flags), but I can't manage to set one user defined flag. It is possible to mark the messages received by my application on the e-mail account, or I have to retain all message ids and every time when I get messages from imap I have to compare their id with retained ids and get only the messages that has different ids?

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  • What is the base open source java package to filter/match URLs?

    - by Boaz
    Hi, I have an high performance application which deals with URLs. For every URL it needs to retrieve the appropriate settings from a predefined pool. Every settings object is associated with a URL pattern which indicates which URLs should use these settings. The matching rules are as follows: "google.com" match pattern should match all URLs pointing to the google domain (thus, maps.google.com and www.google.com/match are matched). "*.google.com" should match all URLs pointing to a subdomain of google.com (thus, maps.google.com matches, but google.com and www.google.com don't). "maps.google.com" should match all URLs pointing to this specific subdomain. Apart from the above rules, every match rule can contain a path, which means that the path part of the URL should start with the match rule path. So: "*.google.com/maps" matches "maps.google.com/maps" but not "maps.google.com/advanced". As you can see the rules above are overlapping. In the case two rules exist which match the same URL the most specific should apply. The list above is ranked from least specific to most specific. This seems to be such a standard problem that I was hoping to use a ready made library rather than program my self. Google reveals a couple of options but without a clear way to choose between them. What would you recommend as a good library for this task? Thanks, Boaz

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  • Simple way to reorder methods of a Java class in IntelliJ?

    - by Péter Török
    Is there a simpler way of reordering methods within a class source file in IntelliJ than cutting and pasting the code manually? Nowadays I often need this while refactoring legacy code, e.g. to move related methods close to each other in the source code. In Eclipse AFAIK there is a view similar to the Structure view of IntelliJ, where I can drag and drop methods around. However, this does not work in IntelliJ and I couldn't find any hints from its help either. I am using IntelliJ 9.0.2 to be specific.

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  • How to perform different operations within Observer's update() in Java?

    - by Nazgulled
    I just started playing with Observable, Observer and it's update() method and I can't understand what should I do when different actions call notifyObservers(). I mean, my Observable class has a few different methods that call setChanged() and notifyObservers() in the end. Depending on the called method, some part of the UI (Swing) needs to be updated. However, there is only one update() method implemented in the Observer class. I though of passing something to the notifyObservers() method and then I can check the argument on update() but it doesn't seem feel like a good way to do it. Even if it did, what should I pass? A string with a short description of the action/method? And int, like an action/method code? Something else? What's the best way to handle this situation?

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  • Ant fails without message at javac

    - by digitala
    I've written an Ant build.xml file which obtains a number of source files via WSDL and compiles them. These have been working on an old, now destroyed (and therefore unavailable for comparison), system but the build process isn't completing on this newer, faster system. The relevant section of the build file looks like this: <target name="compile" depends="init"> <java classname="org.apache.axis.wsdl.WSDL2Java"> <arg line="--all --server-side --skeletonDeploy --factory --wrapArrays --output src ${srcurl}" /> </java> <javac srcdir="${src}" destdir="${build}" verbose="yes" /> </target> The files are downloaded via the WSDL service successfully, however after that point Ant simply stops & returns to the commandline. Versions of the relevant apps: # java -version java version "1.6.0_14" Java(TM) SE Runtime Environment (build 1.6.0_14-b08) Java HotSpot(TM) 64-Bit Server VM (build 14.0-b16, mixed mode) # javac -version javac 1.6.0_14 # ant -version Apache Ant version 1.6.5 compiled on January 6 2007 I'm assuming that there's a problem with javac that Ant isn't passing back. Is there any way I can get some debugging information from javac? I've tried adding a <record /> tag to the target but that doesn't give any more information than running ant -v does. Any other suggestions would be great, also!

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  • Java Properties and References -- I'm not getting what I expect.

    - by Blumer
    I'm a little embarrassed to ask this as I ought to know better, but here's what I've got. I have an object "Pitcher" with an int property of "runsAllowed". I have an object Batter that has a property of "responsiblePitcher". I have an object Team that has a property "pitcher". When the batter reaches base: Batter.responsiblePitcher = Team.pitcher; All that's well and good. However, if we have a pitching change while the runner is on base, I set a new pitcher in Team.pitcher: Team.pitcher = new Pitcher(); ... and of course this changes the value of Batter.pitcher. How should I be doing things differently such that the Batter.responsiblePitcher property continues to point to the pitcher who let him on base instead of pointing at whever is in the Team.pitcher property? Again, I feel like I ought to know this already ... Thanks.

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  • How to make video in Java captured from webcam through lti-Civil CaptureDeviceStream ?

    - by i.Psi
    Can I do it only with the lti-Civil classes or I need FMJ or JMF ? do I use the actual Stream or set of captured Images from CaptureObserver? Thanks. captureStream = system.openCaptureDeviceStream(info.getDeviceID()); captureStream.setObserver(new CaptureObserver(){ public void onError(CaptureStream arg0, CaptureException arg1) { } public void onNewImage(CaptureStream streamSource, Image image) { try { imageFrame.setImage(AWTImageConverter.toBufferedImage(image)); bufferedImage = AWTImageConverter.toBufferedImage(image); } catch (Throwable t) { t.printStackTrace(); } } }); captureStream.start();

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  • Using Scanner in Java how can I hasNext(aString) where the string is not regex pattern?

    - by Parris
    Hi, I am trying to do as my question states, sooo I have the following code which would find the match. String test = scan.next(); if (test.equals("$let")) return 1; However, I would prefer to use hasNext as to not consume a token; however, when i do the following it fails. if (scan.hasNext("$let")) return 1; I realize the when giving has next a variable it expects a pattern, but I thought if i don't have any regex symbols it should work. I also thought $ was possibly some regex symbol so I tried /$ however, that did not work! Thanks for the help!

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  • [JAX-B] How can I ignore a superclass?

    - by MrSpandex
    I'm trying to write a web service for the java.util.logging api. So I wrote a class MyLogRecord that inherits from LogRecord. I annotated this class with JAX-B annotations, including @XmlAccessorType(XmlAccessType.NONE) so it would ignore non-annotated fields and properties. When I start up tomcat, I get errors that java.util.logging.Level and other java.util.logging classes do not have a default constructor, but none of my annotated methods make any reference to the Level class or any of the other java.util.logging classes. These are referenced by the parent class. My sub-class has everything it needs defined. How can I get JAX-B to ignore the parent class completely? Update: I found another post on this, which suggests modifying the parent class. This is obviously not possible because I am extending a java.util class. IS there any way to do this without modifying the superclass? Update2: I found a thread on java.net for a similar problem. That thread resulted in an enhancement request, which was marked as a duplicate of another issue, which resulted in the @XmlTransient annotation. The comments on these bug reports lead me to believe this is impossible in the current spec.

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