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  • How to force my method to accept objects from external software?

    - by Roman
    I have a method which needs to take a callback object as an argument and then (at the moment when it's needed) my method will call a specific method of the callback object. I wrote a class called Manager which has a method called addListener. As the argument for this method I need to use a callback object which is defined by the external software. So, I define the addListener in the following way: public void addListener(Listener listener). Of course Eclipse complains because it does not know what Listener is (because the Listener is defined by the external software). The only think that I know (should know) about the Listener is that it has a method called doSomething. So, to pleasure Eclipse I add an interface before my Manager class: interface Listener { void doSomething(); } public class CTManager { ... The problem seems to be solved but then I try to test my software. So, I create a class called test. In this class I create an instance of the Manager class and try to use addListener method of this instance. I also create a class Listener, instantiate it and give the instance to the addListener. And it's the place where the problem appears. Eclipse writes that addListener is not applicable to the given argument. I think it's because it expect something from my Listenr interface but gets something from the Listener class. How can I solve this problem?

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  • Limiting JMS Destination Instances

    - by jumponadoughnut
    Is it possible to limit the number of JMS receiver instances to a single instance? I.e. only process a single message from a queue at any one time? The reason I ask is because I have a fairly intensive render type process to run for each message (potentially many thousands). I'd like to limit the execution of this code to a single instance at a time. My application server is JBoss AS 6.0 Any help much appreciated

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  • Read a file with 2048 bytes

    - by Suresh S
    Guys i have a file which has only one line. The file has no encoding it is a simple text file with single line. For every 2048 byte in a line , there is new record of 151 byte (totally 13*151 byte = 1945 records + 85 byte empty space). similarly for the next 2048 bytes. What is the best file i/o to use? i am thinking of reading 2048 bytes from file and storing it in an array . while (offset < fileLength &&(numRead=in.read(recordChunks, offset,alength)) >= 0) { } how can i get from the read statement only 2048 bytes at a time . i am getting IndexOutofBoundException.

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  • How to copy an object by value, not by reference

    - by Blankman
    I want to make a copy of an object, then after some logic, re-assign the original object the value of the copy. example: User userCopy = //make a copy foreach(...) { user.Age = 1; user.ID = -1; UserDao.Update(user) user = userCopy; } I don't want a copy by reference, it has to be a copy by value. The above is just a sample, not how I really want to use it but I need to learn how to copy by value.

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  • Is there a design pattern to cut down on code duplication when subclassing Activities in Android?

    - by Daniel Lew
    I've got a common task that I do with some Activities - downloading data then displaying it. I've got the downloading part down pat; it is, of course, a little tricky due to the possibility of the user changing the orientation or cancelling the Activity before the download is complete, but the code is there. There is enough code handling these cases such that I don't want to have to copy/paste it to each Activity I have, so I thought to create an abstract subclass Activity itself such that it handles a single background download which then launches a method which fills the page with data. This all works. The issue is that, due to single inheritance, I am forced to recreate the exact same class for any other type of Activity - for example, I use Activity, ListActivity and MapActivity. To use the same technique for all three requires three duplicate classes, except each extends a different Activity. Is there a design pattern that can cut down on the code duplication? As it stands, I have saved much duplication already, but it pains me to see the exact same code in three classes just so that they each subclass a different type of Activity.

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  • ant conditions problem

    - by senzacionale
    I have problem with ant. I woul dlike to use conditions in ant. But i get error of: BUILD FAILED C:\Projekti\Projekt ANT\build.xml:412: Problem: failed to create task or type Cause: The name is undefined. Action: Check the spelling. Action: Check that any custom tasks/types have been declared. Action: Check that any / declarations have taken place. and this is code: <target name="test"> <input message="Write some text: " addproperty="foo" /> <if> <equals arg1="${foo}" arg2="bar" /> <then> <echo message="The value of property foo is 'bar'" /> </then> <elseif> <equals arg1="${foo}" arg2="foo" /> <then> <echo message="The value of property foo is 'foo'" /> </then> </elseif> <else> <echo message="The value of property foo is not 'foo' or 'bar'" /> </else> </if> </target>

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  • Which faces technology for use with GlassFish 2.1 and NetBeans 6.7?

    - by SteJav
    I'm running GlassFish 2.1 and using NetBeans 6.7. I'd like to create a web interface to my data using JSF 1.2. Trouble is, I'm not sure which 'faces' technology to learn (that includes some good documentation). JBoss/RichFaces seem pretty good on documentation, but I'm using GlassFish. Any thoughts? The choices appear overwhelming: Tomahawk Tobago Trinidad ICEfaces RCFaces Netadvantage WebGalileoFaces QuipuKit BluePrints Woodstock JBoss RichFaces Ajax4jsf ILOG Oracle ADF G4JSF Simplica Backbase jenia4faces VisualWebPack DynaFaces IBM Impl Dinamica Mojarra PrimeFaces jQuery OpenFaces ZK ExtJS Anybody had any experience with any of the above and found the documentation to be clear to a beginner? Being a JSF/Web beginner, I tried some ICEFaces, Mojarra tutorials and had a go at getting RichFaces working with NBeans and GlassFish, but no luck. Lots of XML complaints. I'm clearly missing some huge chunks of configuration, but I can't find any documentation to help me. Any suggestions would be much appreciated :-)

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  • JarEntry.getSize() is returning -1 when the jar files is opened as InputStream from URL

    - by Reshma Donthireddy
    I am trying to read file from the JarInputStream and the size of file is returning -1. I am accessing Jar file from the URL as a inputStream. URLConnection con = url.openConnection(); JarInputStream jis = new JarInputStream(con.getInputStream()); JarEntry je = null; while ((je = jis.getNextJarEntry()) != null) { htSizes.put(je.getName(), new Integer((int) je.getSize())); if (je.isDirectory()) { continue; } int size = (int) je.getSize(); // -1 means unknown size. if (size == -1) { size = ((Integer) htSizes.get(je.getName())).intValue(); } byte[] b = new byte[(int) size]; int rb = 0; int chunk = 0; while (((int) size - rb) > 0) { chunk = jis.read(b, rb, (int) size - rb); if (chunk == -1) { break; } rb += chunk; } // add to internal resource hashtable htJarContents.put(je.getName(), baos.toByteArray()); }

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  • Making an efficient algorithm

    - by James P.
    Here's my recent submission for the FB programming contest (qualifying round only requires to upload program output so source code doesn't matter). The objective is to find two squares that add up to a given value. I've left it as it is as an example. It does the job but is too slow for my liking. Here's the points that are obviously eating up time: List of squares is being recalculated for each call of getNumOfDoubleSquares(). This could be precalculated or extended when needed. Both squares are being checked for when it is only necessary to check for one (complements). There might be a more efficient way than a double-nested loop to find pairs. Other suggestions? Besides this particular problem, what do you look for when optimizing an algorithm? public static int getNumOfDoubleSquares( Integer target ){ int num = 0; ArrayList<Integer> squares = new ArrayList<Integer>(); ArrayList<Integer> found = new ArrayList<Integer>(); int squareValue = 0; for( int j=0; squareValue<=target; j++ ){ squares.add(j, squareValue); squareValue = (int)Math.pow(j+1,2); } int squareSum = 0; System.out.println( "Target=" + target ); for( int i = 0; i < squares.size(); i++ ){ int square1 = squares.get(i); for( int j = 0; j < squares.size(); j++ ){ int square2 = squares.get(j); squareSum = square1 + square2; if( squareSum == target && !found.contains( square1 ) && !found.contains( square2 ) ){ found.add(square1); found.add(square2); System.out.println( "Found !" + square1 +"+"+ square2 +"="+ squareSum); num++; } } } return num; }

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  • Buffering db inserts in multithreaded program

    - by Winter
    I have a system which breaks a large taks into small tasks using about 30 threads as a time. As each individual thread finishes it persists its calculated results to the database. What I want to achieve is to have each thread pass its results to a new persisance class that will perform a type of double buffering and data persistance while running in its own thread. For example, after 100 threads have moved their data to the buffer the persistance class then the persistance class swaps the buffers and persists all 100 entries to the database. This would allow utilization of prepared statements and thus cut way down on the I/O between the program and the database. Is there a pattern or good example of this type of multithreading double buffering?

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  • How to display image in Swing? in textarea?

    - by Nitesh Panchal
    Hello, I am creating a chat application using JApplet. I have a TextArea where all chat messages go. Everything in working fine and smooth just as you would expect a basic chat application to do. Now i want to add support for gestures. I wanted to know, how can we show an icon in textarea? it only takes string in append() method. Thanks in advance :)

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  • What is the correct approach to using GWT with persistent objects?

    - by dankilman
    Hi, I am currently working on a simple web application through Google App engine using GWT. It should be noted that this is my first attempt at such a task. I have run into to following problem/dilema: I have a simple Class (getters/setters and nothing more. For the sake of clarity I will refer to this Class as DataHolder) and I want to make it persistent. To do so I have used JDO which required me to add some annotations and more specifically add a Key field to be used as the primary key. The problem is that using the Key class requires me to import com.google.appengine.api.datastore.Key which is ok on the server side, but then I can't use DataHolder on the client side, because GWT doesn't allow it (as far as I know). So I have created a sister Class ClientDataHolder which is almost identical, though it doesn't have all the JDO annotations nor the Key field. Now this actually works but It feels like I'm doing something wrong. Using this approach would require maintaining to separate classes for each entity I wish to have. So my question is: Is there a better way of doing this? Thank you.

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  • Any tools or techniques for validating constraints programmatically between databases?

    - by Brandon
    If you had two databases, that had two tables between them that would normally implement a one to one (or many to many) constraint but cannot since they are separate databases, how would you validate this relationship in an application or test? Is there a simple way to do this? For example, a tool or technique that can, given a constraint type, tables and fields, does the validation. I imagine that this isn't the first time this come up so I'm hoping people can share their solution. Thanks.

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  • Is it possible to apply inheritance to a Singleton class?

    - by Bragaadeesh
    Hi, Today I faced one question in interview. Is it possible to apply inheritance concept on Singleton Classes. I said since the constructor is private, we cannot extend that Singleton class (can someone please validate this). Next thing he asked me is to apply inheritance on that Singleton class. So, I made the Singleton's constructor as protected thinking that child's constructor also has be protected. But I was wrong the child can have a modifier either equal to or higher than that. So, I asked him to give a real world example on such a case. He was not able to give me one and said that I cant ask questions and wanted me to tell whether this scenario is possible or not. I went kind of blank. My question here is, Is this possible? Even if its possible, what is the use of it? What real world scenario would demand such a use. Thanks

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  • Does close ever throw an IOException?

    - by TofuBeer
    After providing some answers here, and reading some comments, it would seem that, in practice IOException is never thrown on close for file I/O. Are there any cases in which calling close on a Stream/Reader/Writer actually throws an IOException? If an exception is actually thrown, how should it be dealt with?

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  • Javascript get li values and encode them

    - by bluedaniel
    At the moment I have two (maybe more) unordered lists which are sortable with jquery and ui. The things that work are that the lists are connected, items are draggable, items can be removed and a form that adds to the list. What I need however is a function that gets all the content for li items and json encode them ready to be sent off to some db function, or something. Im new to jquery however and cant find documentation for li items. Hope Ive explained this well. Daniel

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  • Possible loss of precision / [type] cannot be dereferenced

    - by Samuel
    I have been looking around a lot but i simply can't find a nice solution to this... Point mouse = MouseInfo.getPointerInfo().getLocation(); int dx = (BULLET_SPEED*Math.abs(x - mouse.getX()))/ (Math.abs(y - mouse.getY()) + Math.abs(x - mouse.getX()))* (x - mouse.getX())/Math.abs(x - mouse.getX()); In this constellation i get: Possible loss of precision, when i change e.g (x - mouse.getX()) to (x - mouse.getX()).doubleValue() it says double cannot be dereferenced, when i add intValue() somewhere it says int cannot be dereferenced. What's my mistake? [x, y are integers | BULLET_SPEED is a static final int] Thanks!

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  • Common Utility for Exception Searching

    - by Andrew
    I wrote this little helper method to search the exception chain for a particular exception (either equals or super class). However, this seems like a solution to a common problem, so was thinking it must already exist somewhere, possibly in a library I have already imported. So, any ideas on if/where this might exist? boolean exceptionSearch(Exception base, Class<?> search) { Throwable e = base; do { if (search.isAssignableFrom(e.getClass())) { return true; } } while ((e = e.getCause()) != null); return false; }

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  • How can I qualify an autowired property with a variable from a config file using annotations?

    - by jiggy
    My specific problem is that I have configured two beans that implement the same interface and I have a third bean that has a property of that interface's type. I inject the property using a config property. So, assuming RemoteDataSource and LocalDataSource implement IDataSource and dao1 has a property of type IDataSource, my XML config might look like this: <bean id="datasource1" class="com.foo.RemoteDataSource"> <property name="url">${url}</property> </bean> <bean id="datasource2" class="com.foo.LocalDataSource"> <property name="path">${filepath}</property> </bean> <bean id="dao1" class="com.foo.MyDAO"> <property name="dataSource">${datasource}</property> </bean> With url, filepath and datasource being defined in an included properties file. We are now making a push for annotation-driven configuration and I'm not sure how to annotate my dao to put the data source configured in the property file. I want to do something like this, but it is evidently not allowed: @Autowired @Qualifier("${datasource}") public void setDataSource(IDataSource datasource) {...}

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  • Architecture of a secure application that encrypts data in the database.

    - by Przemyslaw Rózycki
    I need to design an application that protects some data in a database against root attack. It means, that even if the aggressor takes control over the machine where data is stored or machine with the application server, he can't read some business critical data from the database. This is a customer's requirement. I'm going to encrypt data with some assymetric algorithm and I need some good ideas, where to store private keys, so that data is secure as well as the application usability was quite comfortable? We can assume, for simplicity, that only one key pair is used.

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