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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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  • 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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  • 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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  • Can I call make runtime decided method calls in Java?

    - by Catalin Marin
    I know there is an invoke function that does the stuff, I am overall interested in the "correctness" of using such a behavior. My issue is this: I have a Service Object witch contains methods which I consider services. What I want to do is alter the behavior of those services without later intrusion. For example: class MyService { public ServiceResponse ServeMeDonuts() { do stuff... return new ServiceResponse(); } after 2 months I find out that I need to offer the same service to a new client app and I also need to do certain extra stuff like setting a flag, or make or updating certain data, or encode the response differently. What I can do is pop it up and throw down some IFs. In my opinion this is not good as it means interaction with tested code and may result in un wanted behaviour for the previous service clients. So I come and add something to my registry telling the system that the "NewClient" has a different behavior. So I'll do something like this: public interface Behavior { public void preExecute(); public void postExecute(); } public class BehaviorOfMyService implements Behavior{ String method; String clientType; public void BehaviorOfMyService(String method,String clientType) { this.method = method; this.clientType = clientType; } public void preExecute() { Method preCall = this.getClass().getMethod("pre" + this.method + this.clientType); if(preCall != null) { return preCall.invoke(); } return false; } ...same for postExecute(); public void preServeMeDonutsNewClient() { do the stuff... } } when the system will do something like this if(registrySaysThereIs different behavior set for this ServiceObject) { Class toBeCalled = Class.forName("BehaviorOf" + usedServiceObjectName); Object instance = toBeCalled.getConstructor().newInstance(method,client); instance.preExecute(); ....call the service... instance.postExecute(); .... } I am not particularly interested in correctness of code as in correctness of thinking and approach. Actually I have to do this in PHP, witch I see as a kind of Pop music of programming which I have to "sing" for commercial reasons, even though I play POP I really want to sing by the book, so putting aside my more or less inspired analogy I really want to know your opinion on this matter for it's practical necessity and technical approach. Thanks

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  • using compareTo in Binary Search Tree program

    - by Scott Rogener
    I've been working on this program for a few days now and I've implemented a few of the primary methods in my BinarySearchTree class such as insert and delete. Insert seemed to be working fine, but once I try to delete I kept getting errors. So after playing around with the code I wanted to test my compareTo methods. I created two new nodes and tried to compare them and I get this error: Exception in thread "main" java.lang.ClassCastException: TreeNode cannot be cast to java.lang.Integer at java.lang.Integer.compareTo(Unknown Source) at TreeNode.compareTo(TreeNode.java:16) at BinarySearchTree.myComparision(BinarySearchTree.java:177) at main.main(main.java:14) Here is my class for creating the nodes: public class TreeNode<T> implements Comparable { protected TreeNode<T> left, right; protected Object element; public TreeNode(Object obj) { element=obj; left=null; right=null; } public int compareTo(Object node) { return ((Comparable) this.element).compareTo(node); } } Am I doing the compareTo method all wrong? I would like to create trees that can handle integers and strings (seperatly of course)

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  • In the java DBCP connection pool - what is an idle connection?

    - by Ravenor
    A colleague at work insists that a DBCP idle connection is a connection that has lain unused for 30 minutes. I believe a dbcp idle connection is a connection that is in the pool available to be borrowed, and an active connection is one that is borrowed. Looking through the code I found no reference to 30 minutes or other magic values and a cursory glance through the code for assuring minidle does not show any such logic. If he is correct can you please back that up with a code or documentation reference. For the complete answer I would like it answered for both DBCP 1.1 and 1.6.

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  • Open-source and client-side IRC-Client

    - by user125197
    I'm administrating a homepage with an IRC-Webclient. At the moment, it uses a Java-client, modified to be SSL-compatible and compatible with whatever design I want to use. The usual PJIRC thing, with users wishes and concerns implemented (I'll give you SSL-PJIRC if you want - no problem. The login-script will be improved for IE6-support this weekend, means write the object tag if an old IE is found, that's it. Rest runs perfectly well). But still, the better user experience would be a client that only requires the user to enable JavaScript. So, before I go into rewriting and customizing a complete Java-IRC-solution, I'd like to ask some other people - after researching for half a year of time. The requirements are: a) Free hosting, no cgi-bin is acceptable. A lot of hosters also have CGI supported, but it doesn't allow IRC-access. So, seems you are limited to x10-hosting for CGI:IRC. b) Solution must be open source (not free as in free beer, but free as in free speech - I want to be able to read every line of the code). c) Hosting cannot be limited to Windows-hosting. Free operation systems (anything with Linux, BSD, whatever - I think you get what I mean) must be possible. d) No server-side technology. I'm limited to everything that runs client-side only. (Well, a Java-Applet does...). d) Solution must support SSL. e) The side must be able to move. Means, you register to a new free hoster, load your things up via FileZilla and the thing simply runs. No server-concerning implementations needed. f) Old browsers must be supported. From all my research, there are two ways a) Java-Applet b) Use HTML5-Websockets (it is impossible to use the JavaScript-library I found, as it depends on ActiveX - means, Windows hosting). b) means "you are going to enter very unstable content". I worked with HTML5 for month, and, well ... Though, HTML5 also is not suitable for older browsers (old browser support is an absolutely necessary requirement). PHP by the way is a server side solution ... so no line of PHP. My idea now was a Java Applet, and a fallback which again is embedded and proprietary, but only requieres JavaScript (wsirc or Mibbit are great here, whilst I prefer wsirc ... and zooming fonts that are plainly to small, but worse, cannot read the code). So my question is - with free hosting, not installation on server, plain upload - do you see and open source, complelety client-side, ssl-compatible way to use or write a client? This wouldn't be my first programming project, I'm not afraid of the code. If there was a way and I had to write it, even from scratch, I'd do. From all I know, there sadly is none. But maybe some experienced admin has an idea? Best Wishes, yetanotheruser Sry my English isn't perfect. It's enough for programming at least.

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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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  • Java multi-threading - what is the best way to monitor the activity of a number of threads?

    - by MalcomTucker
    I have a number of threads that are performing a long runing task. These threads themselves have child threads that do further subdivisions of work. What is the best way for me to track the following: How many total threads my process has created What the state of each thread currently is What part of my process each thread has currently got to I want to do it in as efficient a way as possible and once threads finish, I don't want any references to them hanging around becasuse I need to be freeing up memory as early as possible. Any advice?

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • I can't find the cause of an "unchecked or unsafe operations" warning in Java.

    - by Peter
    Hello, as per the title I am struggling to find the cause of an "unchecked or unsafe operations" warning in some code. If I have the following code, it compiles without any warnings: public void test() { Set<String> mySet = new HashSet<String>(); Set<String> myNewSet = mySet; //do stuff } Now, if I change where mySet comes from, specifically as the result of a method call, I get the "unchecked yadda yadda" warning: public void test() { Set<String> myNewSet = this.getSet(); //do stuff } public Set getSet() { Set<String> set = new HashSet<String>(); return set; } I have tried and tried to work out what the problem is and I am completely stumped. The issue is present whether I use Sets or Lists. Why would the Set returned by the getSet method be any different to the Set in the first example? Any help would be greatly appreciated as while the warning isn't the end of the world, it is bugging the hell out of me! :( Regards

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  • How can I overlay images over one another in Java?

    - by Sam
    So I have been posting all over and have yet to get a solid answer: I have created an image resizing class, with a crop method. The cropping works great. The issue that I am having is the background color that I specify in the drawImage function of Graphics is not working correctly. It defaults to black as the background regardless of what I supply (in this case Color.WHITE). Also, the overlaying image or top most image (comes from a file) is being inverted (I think it is) or otherwise discolored. Just so you can conceptualize this a little bit better, I am taking a jpeg and overlaying it on top of a new BufferedImage, the new buffered image's background is not being set. Here is the code below that I am working with: public void Crop(int Height, int Width, int SourceX, int SourceY) throws Exception { //output height and width int OutputWidth = this.OutputImage.getWidth(); int OutputHeight = this.OutputImage.getHeight(); //create output streams ByteArrayOutputStream MyByteArrayOutputStream = new ByteArrayOutputStream(); MemoryCacheImageOutputStream MyMemoryCacheImageOutputStream = new MemoryCacheImageOutputStream(MyByteArrayOutputStream); //Create a new BufferedImage BufferedImage NewImage = new BufferedImage(Width, Height, BufferedImage.TYPE_INT_RGB); Graphics MyGraphics = NewImage.createGraphics(); MyGraphics.drawImage(this.OutputImage, -SourceX, -SourceY, OutputWidth, OutputHeight, Color.WHITE, null); // Get Writer and set compression Iterator MyIterator = ImageIO.getImageWritersByFormatName("png"); if (MyIterator.hasNext()) { //get image writer ImageWriter MyImageWriter = (ImageWriter)MyIterator.next(); //get params ImageWriteParam MyImageWriteParam = MyImageWriter.getDefaultWriteParam(); //set outputstream MyImageWriter.setOutput(MyMemoryCacheImageOutputStream); //create new ioimage IIOImage MyIIOImage = new IIOImage(NewImage, null, null); //write new image MyImageWriter.write(null, MyIIOImage, MyImageWriteParam); } //convert output stream back to inputstream ByteArrayInputStream MyByteArrayInputStream = new ByteArrayInputStream(MyByteArrayOutputStream.toByteArray()); MemoryCacheImageInputStream MyMemoryCacheImageInputStream = new MemoryCacheImageInputStream(MyByteArrayInputStream); //resassign as a buffered image this.OutputImage = ImageIO.read(MyMemoryCacheImageInputStream); }

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