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  • Java Swing: how to add an image to a JPanel ?

    - by Leonel
    I have a JPanel to which I'd like to add JPEG and PNG images that I generate on the fly. All the examples I've seen so far in the Swing Tutorials, specially in the Swing examples use ImageIcons. I'm generating these images as byte arrays, and they are usually larger than the common icon they use in the examples, at 640x480. Is there any (performance or other) problem in using the ImageIcon class to display an image that size in a JPanel ? What's the usual way of doing it ? How to add an image to a JPanel without using the ImageIcon class ? Edit: A more careful examination of the tutorials and the API shows that you cannot add an ImageIcon directly to a JPanel. Instead, they achieve the same effect by setting the image as an icon of a JLabel. This just doesn't fill right...

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  • Adding an Object to Vector loses Reference using Java?

    - by thechiman
    I have a Vector that holds a number of objects. My code uses a loop to add objects to the Vector depending on certain conditions. My question is, when I add the object to the Vector, is the original object reference added to the vector or does the Vector make a new instance of the object and adds that? For example, in the following code: private Vector numbersToCalculate; StringBuffer temp = new StringBuffer(); while(currentBuffer.length() > i) { //Some other code numbersToCalculate.add(temp); temp.setLength(0); //resets the temp StringBuffer } What I'm doing is adding the "temp" StringBuffer to the numbersToCalculate Vector. Should I be creating a new StringBuffer within the loop and adding that or will this code work? Thanks for the help! Eric

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  • Database Replication OOD Pattern

    - by MrOnigiri
    Greetings fellow overflowers, After reading on MSDN about correct strategies on how to perform database replication, and understanding their suggestion on Master-Subordinate Incremental Replication. It left me wondering, what OOD design pattern should I use on this... The main elements of this strategy are the Acquirer, the Manipulator and the Writer. The first fetches data from the database and passes on to the second which might perform simple transformations to the data, before handling it to the final element, the writer, that writes the desired data on the destination Database. I thought about using the Chain of Responsibility pattern, but the Acquirer, Manipulator and Writer don't share a common role among theme, so It makes no sense. Should these elements be written as separate classes, or methods inside my service? Of course I'll be creating a DB Helper class as well, but that doesn't constitutes a problem. Wondering what your opinions on this are! Thanks for your replies

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  • Saving data to server with user accounts.

    - by AKRamkumar
    Ok, so for an app I am making, I want the user to be able to save data online. On my website, I will provide a web server with tables of UserName/Password/SaveData. How can I do this without crashing the server load? How can I guarantee security ? Is there a Design Pattern for this?Is there a better way of doing this? This is going to be a free application, available to the public and I would like for their settings to be available, no matter the computer they are using. Is there a better way of doing this? I am using MEF for plugins so is there a way I can save plugin data as well?

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  • Help using Horner's rule and Hash Functions in JAVA?

    - by Matt
    I am trying to use Horner's rule to convert words to integers. I understand how it works and how if the word is long, it may cause an overflow. My ultimate goal is to use the converted integer in a hash function h(x)=x mod tableSize. My book suggests, because of the overflow, you could "apply the mod operator after computing each parenthesized expression in Horner's rule." I don't exactly understand what they mean by this. Say the expression looks like this: ((14*32+15)*32+20)*32+5 Do I take the mod tableSize after each parenthesized expression and add them together? What would it look like with this hash function and this example of Horner's rule?

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  • Dealing with ArrayLists in java...all members of the arraylist updating themselves?

    - by Charlie
    I have a function that shrinks the size of a "Food bank" (represented by a rectangle in my GUI) once some of the food has been taken. I have the following function check for this: public boolean tryToPickUpFood(Ant a) { int xCoord = a.getLocation().x; int yCoord = a.getLocation().y; for (int i = 0; i < foodPiles.size(); i++) { if (foodPiles.get(i).containsPoint(xCoord, yCoord)) { foodPiles.get(i).decreaseFood(); return true; } } return false; } Where decreaseFood shrinks the rectangle.. public void decreaseFood() { foodAmount -= 1; shrinkPile(); } private void shrinkPile() { WIDTH -=1; HEIGHT = WIDTH; } However, whenever one rectangle shrinks, ALL of the rectangles shrink. Why would this be?

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  • junit assert in thread throws exception

    - by antony.trupe
    What am I doing wrong that an exception is thrown instead of showing a failure, or should I not have assertions inside threads? @Test public void testComplex() throws InterruptedException { int loops = 10; for (int i = 0; i < loops; i++) { final int j = i; new Thread() { @Override public void run() { ApiProxy.setEnvironmentForCurrentThread(env);//ignore this new CounterFactory().getCounter("test").increment();//ignore this too int count2 = new CounterFactory().getCounter("test").getCount();//ignore assertEquals(j, count2);//here be exceptions thrown. this is line 75 } }.start(); } Thread.sleep(5 * 1000); assertEquals(loops, new CounterFactory().getCounter("test").getCount()); } StackTrace Exception in thread "Thread-26" junit.framework.AssertionFailedError: expected:<5> but was:<6> at junit.framework.Assert.fail(Assert.java:47) at junit.framework.Assert.failNotEquals(Assert.java:277) at junit.framework.Assert.assertEquals(Assert.java:64) at junit.framework.Assert.assertEquals(Assert.java:195) at junit.framework.Assert.assertEquals(Assert.java:201) at com.bitdual.server.dao.ShardedCounterTest$3.run(ShardedCounterTest.java:77)

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  • In Java What is the guaranteed way to get a FileLock from FileChannel while accessing a RandomAcces

    - by narasimha.bhat
    I am trying to use FileLock lock(long position, long size,boolean shared) in FileChannel object As per the javadoc it can throw OverlappingFileLockException. When I create a test program with 2 threads lock method seems to be waiting to acquire the lock (both exclusive and non exclusive) But when the number threads increases in the acutal scenario over lapping file lock exception is thrown and processing slows down due the block at File lock table. What is the best way to acquire lock avoiding the OverlappingFileLockException ?

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  • Equivalent to Android's Toast or Mac OSX Growl in Java Swing?

    - by I82Much
    Hi all, Looking for a means of displaying transient, non-modal dialogs in a Swing application. In other words, I'd like to pop up a semi-transparent box with some text in it that can be immediately dismissed, or will fade away in a set amount of time. Is there a library to do this? I don't want to reinvent the wheel if it already exists. Growl screenshot: Android Toast screenshot:

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  • Where to put a textfile I want to use in eclipse?

    - by Jayomat
    hi there, I need to read a text file when I start my program. I'm using eclipse and started a new java project. In my project folder I got the "src" folder and the standard "JRE System Library"... I just don't know where to put the text file. I cannot use a "hard coded" path because the text file needs to be included with my app... I also tried to create a new folder like "Files" and use the pathe "Files/staedteliste.txt".. doesn't work too... I use the following code to read the file, but I get this error: Error:java.io.FileNotFoundException:staedteliste.txt(No such file or directory) import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.util.ArrayList; public class Test { ArrayList<String[]> values; public static void main(String[] args) { // TODO Auto-generated method stub loadList(); } public static void loadList() { BufferedReader reader; String zeile = null; try { reader = new BufferedReader(new FileReader("staedteliste.txt")); zeile = reader.readLine(); ArrayList<String[]> values = new ArrayList<String[]>(); while (zeile != null) { values.add(zeile.split(";")); zeile = reader.readLine(); } System.out.println(values.size()); System.out.println(zeile); } catch (IOException e) { System.err.println("Error :"+e); } } } thx for help!

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  • What's a good Java API for creating Word documents?

    - by Bill James
    I have a new app I'll be working on where I have to generate a Word document that contains tables, graphs, a table of contents and text. What's a good API to use for this? How sure are you that it supports graphs, ToCs, and tables? What are some hidden gotcha's in using them? Some clarifications: I can't output a PDF, they want a Word doc. They're using MS Word 2003 (or 2007), not OpenOffice Application is running on *nix app-server It'd be nice if I could start with a template doc and just fill in some spaces with tables, graphs, etc. Thanks for the help. Edit: Several good answers below, each with their own faults as far as my current situation. Hard to pick a "final answer" from them. Think I'll leave it open, and hope for better solutions to be created. Edit: The OpenOffice UNO project does seem to be closest to what I asked for. While POI is certainly more mainstream, it's too immature for what I want.

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  • Repeating fields in similar database tables

    - by user1738833
    I have been tasked with working on a database that I have never seen before and I'm looking at the DB structure. Some of the central and most heavily queried and joined tables look like virtual duplicates of each other. Here's a massively simplified representation of the situation, with business-sensitive information changed, listing hypothetical table names and fields: TopLevelGroup: PK_TLGroupId, DisplaysXOnBill, DisplaysYOnBill, IsInvoicedForJ, IsInvoicedForK SubGroup: PK_SubGroupId, FK_ParentTopLevelGroupId, DisplaysXOnBill, DisplaysYOnBill, IsInvoicedForJ, IsInvoicedForK SubSubGroup: PK_SubSUbGroupId, FK_ParentSubGroupId, DisplaysXOnBill, DisplaysYOnBill, IsInvoicedForJ, IsInvoicedForK I haven't listed the types of the fields as I don't think it's particularly important to the situation. In addition, it's worth saying that rather than four repeated fields as in the example above, I'm looking at 86 repeated fields. For the most part, those fields genuinely do represent "facts" about the primary table entity, so it's not automatically wrong for that reason. In addition, the "groups" represented here have a property inheritance relationship. If DisplaysXOnBill is NULL in the SubSubGroup, it takes the value of DisplaysXOnBillfrom it's parent, the SubGroup, and so-on up to the TopLevelGroup. Further, the requirements will never require that the model extends beyond three levels, so there is no need for flexibility in that area. Is there a design smell from several tables which describe very similar entities having almost identical fields? If so, what might be a better design of the example above? I'm using the phrase "design smell" to indicate a possible problem. Of course, in any given situation, a particular design might well be the best solution. I'm looking for a more general answer - wondering what might be wrong with this design and what might be the better design were that the case. Possibly related, but not primary questions: Is this database schema in a reasonably normal form (e.g. to 3NF), insofar as can be told from the information I've provided. I can't see a problem with the requirements of 2NF and 3NF, except in their inheriting the requirements of 1NF. Is 1NF satisfied though? Are repeating groups allowed in different tables? Is there a best-practice method for implementing the inheritance relationship in a database as I require? The method above feels clunky to me because any query on the SubSubGroup necessarily needs to join onto the SubGroup and the TopLevelGroup tables to collect inherited facts, which can make even trivial joins requiring facts from the SubSubGroup table rather long-winded. There are, of course, political considerations to making a relatively large change like this. For the purpose of this question, I'm happy to ignore that fact in the interests of keeping the answers ring-fenced to the technical problem.

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  • Splitting EJBs and interfaces into separate module -- deployment fails

    - by Hank
    I'm having trouble following this guide to "extract" my interfaces and entities from my EAR to use them from another Web Application: I use NetBeans 6.8 and Glassfish 3.0.1 "Java Class Library" project contains all the entities and interfaces "Java EE Application" project class library added to the project, is packaged into the EAR contains EJB implementations, MDBs, Test "Java Web Application" project class library added to the project, is packaged into the WAR contains REST interface When I build and deploy the Web Application, all goes well. When I build the JEE application, I can see the jar-file (interfaces, entities) being included. But when I try to deploy the EAR, Glassfish refuses it with a java.lang.NoClassDefFoundError error: [#|2010-03-28T18:25:59.875+0200|WARNING|glassfishv3.0|javax.enterprise.system.tools.deployment.org.glassfish.deployment.common|_ThreadID=28;_ThreadName=Thread-1;|Error in annotation processing: java.lang.NoClassDefFoundError: mvs/core/StoreServiceLocal|#] [#|2010-03-28T18:25:59.876+0200|SEVERE|glassfishv3.0|javax.enterprise.system.core.com.sun.enterprise.v3.server|_ThreadID=28;_ThreadName=Thread-1;|Exception while deploying the app java.lang.IllegalArgumentException: Invalid ejb jar [CoreServer]: it contains zero ejb. Note: 1. A valid ejb jar requires at least one session, entity (1.x/2.x style), or message-driven bean. 2. EJB3+ entity beans (@Entity) are POJOs and please package them as library jar. 3. If the jar file contains valid EJBs which are annotated with EJB component level annotations (@Stateless, @Stateful, @MessageDriven, @Singleton), please check server.log to see whether the annotations were processed properly. 'mvs/core/StoreServiceLocal' is an interface which is defined in the library jar file. What am I doing wrong?

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  • logic of button to be disabled or not in mvc

    - by rod
    Hi All, Here's an excerpt from a book I'm reading about application design with MVC: Ideally, the view is so simple and logic-free as to need virtually no testing. Users (and developers before users) can reasonably test the view by simply looking at the pixels on the screen. Anything else beyond pure graphical rendering should ideally be taken out of the view and placed in the controller and model. This includes, for example, the logic that determines whether a certain button should be enabled or grayed out at some point. what does the bold statement mean to you? what would this look like? thanks, rod.

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  • How can I control the width of JTextFields in Java Swing?

    - by Jonas
    I am trying to have several JTextFields on a single row, but I don't want them to have the same width. How can I control the width and make some of them wider than others? I want that they together take up 100% of the total width, so it would be good if I could use some kind of weigthing. I have tried with .setColumns() but it doesn't make sense. Here is my code: class Row extends JComponent { public Row() { this.setLayout(new BoxLayout(this, BoxLayout.X_AXIS)); JTextField fld1 = new JTextField("First field"); JTextField fld2 = new JTextField("Second field, should be longer"); JTextField fld3 = new JTextField("Short field"); JTextField fld4 = new JTextField("Another field"); fld1.setBorder(null); fld2.setBorder(null); fld3.setBorder(null); fld4.setBorder(null); fld1.setFocusable(false); fld2.setFocusable(false); fld3.setFocusable(false); fld4.setFocusable(false); fld1.setColumns(5); // makes no sense this.add(fld1); this.add(fld2); this.add(fld3); this.add(fld4); } } this.setLayout(new GridLayout(20,0)); this.add(new Row()); this.add(new Row()); this.add(new Row());

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  • Spring-MVC Problem using @Controller on controller implementing an interface

    - by layne
    I'm using spring 2.5 and annotations to configure my spring-mvc web context. Unfortunately, I am unable to get the following to work. I'm not sure if this is a bug (seems like it) or if there is a basic misunderstanding on how the annotations and interface implementation subclassing works. For example, @Controller @RequestMapping("url-mapping-here") public class Foo { @RequestMapping(method=RequestMethod.GET) public void showForm() { ... } @RequestMapping(method=RequestMethod.POST) public String processForm() { ... } } works fine. When the context starts up, the urls this handler deals with are discovered, and everything works great. This however does not: @Controller @RequestMapping("url-mapping-here") public class Foo implements Bar { @RequestMapping(method=RequestMethod.GET) public void showForm() { ... } @RequestMapping(method=RequestMethod.POST) public String processForm() { ... } } When I try to pull up the url, I get the following nasty stack trace: javax.servlet.ServletException: No adapter for handler [com.shaneleopard.web.controller.RegistrationController@e973e3]: Does your handler implement a supported interface like Controller? org.springframework.web.servlet.DispatcherServlet.getHandlerAdapter(DispatcherServlet.java:1091) org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:874) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:809) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:571) org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:501) javax.servlet.http.HttpServlet.service(HttpServlet.java:627) However, if I change Bar to be an abstract superclass and have Foo extend it, then it works again. @Controller @RequestMapping("url-mapping-here") public class Foo extends Bar { @RequestMapping(method=RequestMethod.GET) public void showForm() { ... } @RequestMapping(method=RequestMethod.POST) public String processForm() { ... } } This seems like a bug. The @Controller annotation should be sufficient to mark this as a controller, and I should be able to implement one or more interfaces in my controller without having to do anything else. Any ideas?

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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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