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  • Call a function by its name, given from string java

    - by Joao
    Hello, I would like to be able to call a function based on its name provided by a string. Something like public void callByName(String funcName){ this.(funcName)(); } I have searched a bit into lambda funcions but they are not supported. I was thinking about going for Reflection, but I am a bit new to programming, so I am not so familiar with the subject. This whole question was brought up on my java OOP class, when I started GUI (Swing, swt) programming, and events. I found that using object.addActionCommand() is very ugly, because I would later need to make a Switch and catch the exact command I wanted. I would rather do something like object.attachFunction(btn1_click), so that it would call the btn1_click function when the event click was raised. Thank you Joao

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  • java xml pretty printing - preserve empty elements and white pace

    - by javamonkey79
    Basically, I am looking for a java library that will take this: <foo><bar> </bar><baz>yadda</baz></foo> And pretty print it to this: <?xml version="1.0" encoding="UTF-8"?> <foo> <bar> </bar> <baz>yadda</baz> </foo> e.g. preserving whitespace AND blank elements The closest I have got was with dom4j like so: OutputFormat format = OutputFormat.createPrettyPrint(); format.setTrimText( false ); However, this does not honor the whitespace unless the element contains other character data. I'm not opposed to writing something on my own, but I would think this has already been done, why reinvent the wheel?

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  • Run java thread at specific times

    - by rmarimon
    I have a web application that synchronizes with a central database four times per hour. The process usually takes 2 minutes. I would like to run this process as a thread at X:55, X:10, X:25, and X:40 so that the users knows that at X:00, X:15, X:30, and X:45 they have a clean copy of the database. It is just about managing expectations. I have gone through the executor in java.util.concurrent but the scheduling is done with the scheduleAtFixedRate which I believe provides no guarantee about when this is actually run in terms of the hours. I could use a first delay to launch the Runnable so that the first one is close to the launch time and schedule for every 15 minutes but it seems that this would probably diverge in time. Is there an easier way to schedule the thread to run 5 minutes before every quarter hour?

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  • Interaction between Java and Android

    - by Grasper
    I am currently trying to research how to use Android with an existing java based system. Basically, I need to communicate to/from an Android application. The system currently passes object data from computer to computer using ActiveMQ as the JMS provider. On one of the computers is a display which shows object data to the user. What we want to do now is use a phone (running Android) as another option to show this object data to a user with wifi/network access. Ideally we would like to have a native application on the Android that would listen to the ActiveMQ topic and publish to another Topic and read/write/display the object data, but from some research I have done, I am not sure if this is possible. What are some other ways to approach this problem? The android Phone needs to be able to send/receive data. I have been using the AndroidEmulator for testing.

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  • How should objects be in a Java game.

    - by Gabriel A. Zorrilla
    EDIT: i just deleted the entire post and reformulated the question to be more generic. I want to do a simple strategy game: map, units. Map: one class. Units: another class, self drawn. Simple questions: How does an unit should redraw itself on the map. A unit should be a JPanel or similar Swing component (just to be able to manage them as an entity with its own mousehandlers) or can be another thing, without neglecting the fact that it should be an autonomous object with its own action handlers and fields. Is this map-units model correct of a simple game that would help me to learn in a fun way Java and OOP fundamentals. Thats it!

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  • Greek/latin scientific JLabel in Java Swing application

    - by MartinStettner
    For a scientific application I want to design an input form which lets the user enter certain parameters. Some of them are designated using greek letters, some of them have latin letters. The parameter names should be displayed using ordinary JLabel controls. On Windows, the Tahoma font (which is used for Labels by default) contains both latin and greek letters, so I simply set the Text property of the label to a greek (unicode) string and everything works fine. I'm wondering if this works also without modifications on Linux and OSX systems resp. for which Java/OS versions this would work. Also I'm curious if there's an easy way to show subscripts in labels ("\eta_0" in TeX), but this is not that important for my application ...

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  • NFS Server in Java

    - by dmeister
    I search an implementation of a network (or distributed) file system like NFS in Java. The goal is to extend it and do some research stuff with it. On the web I found some implementation e.g. DJ NFS, but the open question is how mature and fast they are. Can anyone purpose a good starting point, has anyone experience with such things? P.S. I know Hadoop DFS and I used it for some projects, but Hadoop is not a good fit for the things I want to do here. --EDIT-- Hadoop is really focused on highly scalable, high throughput computing without the possibilities to overwrite parts of a file and so an. The goal is you could use the filesystem e.g. for user home directories. --EDIT-- More Details: The idea is to modify such a implementation so that the files are not stored directly on a local filesystem, but to apply data de-duplication.

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  • Transfer files using java

    - by markovuksanovic
    I need to transfer lots of small files to a remote computer within my java program. I was wondering if somebody could suggest the best way to do so... I need to transfer lots of small files and it has to be really fast. Should I use some existing protocol implementation? maybe ftp? One important thing is that most files would be the same all the time, or the difference would be minor so I was thinking of using git for that purpose. Does anyone have experience with sth like this?

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  • Problems with retrieving the correct cookie in Java

    - by Spines
    When I retrieve the cookies in my java servlet, all of the values from getPath() are null. So if a cookie with the same name is set in directory /foo, and at the root directory, I retrieve two cookies with the same exact name, but I can't differentiate them because getPath() returns null for both. I looked in firebug and saw that firefox was not sending anythign for the path. My application uses a "rememberme" cookie with the path set to "/". Everything works fine as long as there is only one cookie with name rememberme. But if somehow another cookie gets set with the same name on a different path like /foo, then my application won't know which one is the one I set for the root. How can I differentiate the cookies? Do I need to worry about a cookie existing with the same name in a subdir, or can I just assume there will be only the one I set?

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  • Listeners when using hylafax from Java

    - by DaDaDom
    I am trying to send a fax to a hylafax server via Java: Client faxClient = new HylaFAXClient(); faxClient.open(...); faxClient.user(...); faxClient.pass(...); Job j = faxClient.createJob(); job.setStuff(...); job.setNotifyType(Job.NOTIFY_ALL); faxClient.addTransferListener(new FaxTransferListener()); faxClient.addConnectionListiener(new FaxConnectionListener()); faxClient.submit(job); The problem is that I don't get any notifications on any of the listener methods. When I watch the queues on the hylafax server, e.g. via JHylaFax, the job failed, but how can I react to that event programatically on client side without having to poll the job queues regularly?

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  • Best Design for a Facebook clone on GAE Java

    - by charming30
    My current App is written in Python on GAE which can do Contacts management, Genealogy, Social Networking, Photo sharing, Telecom Integration (SMS, iVRS, URL Billing), CRON and performs business logic operations for our Mobile Apps. Current Architecture indlues python, django, jquery, memcache and few telecom APIs. Now, It feels that an SOA Architecture on GAE using Java would be really ideal and scalable for this kind of App where we want to build new features like widgets that users can turn on or off and third party developers can also develop and deploy features. Please correct me or improve the following design decision: UI (Current plan is GWT) Sessions, Security and ACL (Spring MVC 2.x) Reusable Business Logic components (?) Implementation of Web Services (?) Your advice would really help.

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  • How to do google webpage translate in a Java class

    - by Robert
    Hi,this is a follow-up question of mine. Suppose now I have a URL : http://www.baidu.com/s?bs=%B0%C2%B0%CD%C2%ED&f=8&wd=%B0%C2%B0%CD%C2%ED and it work perfectly by inputting it in the text field of google translate and select from "Chinese" to English. My question is ,suppose now I want to achieve this in Java, I would like to adopt "Process q=Runtime.getRuntime().exec( "cmd /c start +URL" approach to do this. Could I achieve that by simply concatenating the Google translate URL and the webpage URL? If yes,could you please elaborte,thanks.

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  • time required in java

    - by Amol
    i would like to know how much time is required to execute the conditional loops individually. Like if i had an option to use "if else", "while","for", or "foreach" loop then which loop would get executed faster.I know the difference would be very small and most would say that it would not matter but if i were to have a program which would access thousands of data then this point would come into picture. I would like to know if i declare a variable in the beginning in java and if i were to declare it just before i use it will it make any difference. will the total time required be reduced? if yes then which is practically used (the one in which variables are declared in the beginning or where they are just declared b4 they are used)?

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  • SocketTimeOutException while creating socket, java

    - by Sunil Kumar Sahoo
    Hi All, I have created a sample java socket application. I used Socket s = new Socket(ip, port) Now it works fine. but when my internet connection is very slow that time after a long interval (even if sometimes after 2 minutes) i used to get SocketTimeOutException in that line. means it gives that error while creating socket. I want the exception should be handled properly means if internet connection is very slow then if that error occurs it happens very late now . I want if this type of error occurs then it should be caught very fast means the error should not come at such a delay interval of time rather it should come immediately. How to achieve this. Thanks Sunil Kumar Sahoo

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  • concurrency in Java

    - by p1
    1]What is Non-blocking Concurrency and how is it different. 2] I have heard that this is available in Java. Are there any particular scenarios we should use this feature 3] Is there a difference/advantage of using one of these methods for a collection. What are the trade offs class List { private final ArrayList<String> list = new ArrayList<String>(); void add(String newValue) { synchronized (list) { list.add(newValue); } } } OR private final ArrayList<String> list = Collections.synchronizedMap(); The questions are more from a learning/understanding point of view. Thanks for attention.

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  • Java: Parse Australian Street Addresses

    - by bguiz
    Looking for a quick and dirty way to parse Australian street addresses into its parts: 3A/45 Jindabyne Rd, Oakleigh, VIC 3166 should split into: "3A", 45, "Jindabyne Rd" "Oakleigh", "VIC", 3166 Suburb names can have multiple words, as can street names. See: http://stackoverflow.com/questions/1739746/parse-a-steet-address-into-components Has to be in Java, cannot make http requests (e.g. to web APIs). EDIT: Assume that format specified is always followed. I have no issue with spitting incorrectly formatted strings back at the user with a message telling them to follow the format (which I've described above).

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  • Passing parametrized ArrayList to a function in java

    - by user150505
    I have the following fucntion. func(ArrayList <String> name) { ........ } The function fills the ArrayList. (I don't want to return the ArrayList) However, in the caller function the ArrayList obtained has all items of ArrayList as null. For eg. 1 name = new ArrayList[num]; 2 func(name); 3 System.out.println(name[0]); I get NullPointerException at line 3. Is this because of line 1, i.e. I am not parametrizing? If yes, is there another way this can be done? Because java does not allow creating a generic array of parametrized ArrayList.

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  • Java Memory Management

    - by Tara Singh
    I am designing a client-server chat application in Java. This is a secure application where the messages are exchanged using cryptographic algorithms. I have one server and it can support many clients. My problem is that when one client logs on the server it works fine, but when another user logs into the system, the server starts giving me bad padding exceptions for the encrypted text. I am not able to figure out the problem, according to my logic, when new connection request to server is made, the server creates a thread for listening to the client. Is it possible that once the instance of thread class is created, it does all the processing correctly for the first client, but not for the second client because the variables in server listener thread class already have some previous value, and thus the encrypted text is not decrypted properly? Please advise how I can make this process more robust so that the number of clients does not affect how well the server functions.

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  • Java: Local Enums

    - by bruno conde
    Today, I found myself coding something like this ... public class LocalEnums { public LocalEnums() { } public void foo() { enum LocalEnum { A,B,C }; // .... // class LocalClass { } } } and I was kind of surprised when the compiler reported an error on the local enum: The member enum LocalEnum cannot be local Why can't enums be declared local like classes? I found this very useful in certain situations. In the case I was working, the rest of the code didn't need to know anything about the enum. Is there any structural/design conflict that explains why this is not possible or could this be a future feature of Java?

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  • Java exception reading xml file

    - by xain
    Hi, I have the following xml file: <?xml version="1.0" encoding="UTF-8"?> <c1> <c2 id="0001" n="CM" urlget="/at/CsM" urle="/E/login.jsp"> </c2> <c2 id="0002" n="C2M" urlget="/a2t/CsM" urle="/E2/login.jsp"> </c2> </c1> I'm trying to load c2's attributes this way: Document d = DocumentBuilderFactory.newInstance() .newDocumentBuilder() .parse("epxy.xml"); Element c1 = d.getDocumentElement(); Element c2 = (Element)c1.getFirstChild(); while (c2 != null) { ... c2 = (Element)c2.getNextSibling(); } But I get the exception java.lang.ClassCastException: org.apache.xerces.dom.DeferredTextImpl incompatible with org.w3c.dom.Element in the line Element c2 = (Element)c1.getFirstChild(); before the loop. Any hints ? Thanks.

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  • Extending Throwable in Java

    - by polygenelubricants
    Java lets you create an entirely new subtype of Throwable, e.g: public class FlyingPig extends Throwable { ... } Now, very rarely, I may do something like this: throw new FlyingPig("Oink!"); and of course elsewhere: try { ... } catch (FlyingPig porky) { ... } My questions are: Is this a bad idea? And if so, why? What could've been done to prevent this subtyping if it is a bad idea? Since it's not preventable (as far as I know), what catastrophies could result? If this isn't such a bad idea, why not? How can you make something useful out of the fact that you can extends Throwable?

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  • Writing out BMP files with DataBuffer.TYPE_FLOAT or DataBuffer.TYPE_DOUBLE in java

    - by Basil Dsouza
    Hi Guys, I had a problem working with the image classes in java. I am creating a buffered image with DataBuffer.TYPE_DOUBLE. This all works fine in memory (I think). But the problem starts when I try to write it using ImageIO.write. Initially I was getting no exception at all and instead was only getting an empty output file for my troubles.. After a bit of poking around in the code, i found out that the bmp writer doesnt support writing type_double type of files. From: BMPImageWriterSpi.canEncodeImage: if (dataType < DataBuffer.TYPE_BYTE || dataType > DataBuffer.TYPE_INT) return false; So my question is, does anyone have a way of writing out those kind of images to disk? any documentation or tutorial, or link would be helpful. Thanks, Basil Dsouza

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  • Java portable media detection

    - by quosoo
    I would like to write a piece of java code that synchronizes files between local hard drive and a usb storage. I would like to have a different synchronization configuration depending on which usb storage is plugged in and I would like to have apropriate configuration to be selected automatically rather than chosen by the user. I've just read the JSR-80 and jUSB documentation as well as a bunch of articles and SO posts, but all of those are very old and it seems that since that time (around 2005) all the efforts have been abandoned especially for Windows platform, while the OS-independence is quite important to me (at least Windows and Linux need to be supported). Do I really need to use any of the USB APIs to recognize external drives that are connected to the system? I need something that is more unique than file path, drive letter or drive label... And if yes which one would you recommend (unless I missed something jUnit is actually the only for which Windows support exists).

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  • Books recommendation to learn about java networking

    - by elec
    In order to cover for my (glaring) lack of knowledge in the basics of networking, I'm looking for a book which would ideally cover: - 1 or 2 chapters on the transport layer: tcp, udp... - 1 or 2 chapters on the application layer: http, dns... - rest of the book would be devoted to pratical way of sending data across the wire using Java-related technologies. This would involve discussions about existing products (eg. hessian, protobuf, thrift, tibco...) , performances comparisons, case studies...etc.. Does such a book exist ?

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  • Java Polymorphism - Selecting correct method based on subtype

    - by Marty Pitt
    Hi Given the following Class and Service layer signatures: public class PersonActionRequest { PersonVO person // ... other fields } public class MyServiceLayerClass { public void requestAction(PersonActionRequest request) { PersonVO abstractPerson = request.getPerson(); // call appropriate executeAction method based on subclass of PersonVO } private void executeAction(PersonVO person) {} private void executeAction(EmployeeVO employee) {} private void executeAction(ManagerVO manager) {} private void executeAction(UnicornWranglerVO unicornWrangler) {} } As discussed here, java will select the best method based on type info at compile time. (Ie., it will always select executeAction(PersonVO person) ). What's the most appropriate way to select the correct method? The internet tells me that using instanceof gets me slapped. However, I don't see the appropraite way to select the method without explictly casting abstractPerson to one of the other concrete types. Thanks Marty

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