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  • casting a generic array in java

    - by liloboy
    The implementation is for a linked list in java : public AnyType[] toArr() { AnyType[] arr = (AnyType[]) new Object[size]; int i = 0; Node<AnyType> current = head.next; while (cur != head){ arr[i] = current.data;// fill the array i++; current = current.next; } return arr; } public static void main(String[] args) { System.out.println(ll.toArr().toString()); } The error that I get: Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.Integer; Thanks.

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  • Measuring time spent in application / thread

    - by Adamski
    I am writing a simulation in Java whereby objects act under Newtonian physics. An object may have a force applied to it and the resulting velocity causes it to move across the screen. The nature of the simulation means that objects move in discrete steps depending on the time ellapsed between the current and previous iteration of the animation loop; e.g public void animationLoop() { long prev = System.currentTimeMillis(); long now; while(true) { long now = System.currentTimeMillis(); long deltaMillis = now - prev; prev = now; if (deltaMillis > 0) { // Some time has passed for (Mass m : masses) { m.updatePosition(deltaMillis); } // Do all repaints. } } } A problem arises if the animation thread is delayed in some way causing a large amount of time to ellapse (the classic case being under Windows whereby clicking and holding on minimise / maximise prevents a repaint), which causes objects to move at an alarming rate. My question: Is there a way to determine the time spent in the animation thread rather than the wallclock time, or can anyone suggest a workaround to avoid this problem? My only thought so far is to contstrain deltaMillis by some upper bound.

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  • Signal amplitude against time (java)

    - by wsr74ws84
    Hi everyone , I'm racking my brain in order to solve a knotty problem (at least for me) While playing an audio file (using java) I want the signal amplitude to be displayed against time. I mean I'd like to implement a small panel showing a sort of oscilloscope .(SPECTRUM ANALYZER) The audio signal should be viewed in the time domain (vertical axis is amplitude and the horizontal axis is time) Does anyone know how to do it? Is there a good tutorial I can rely on? Since I know vwry little about java , I wish someone could help me . Thanks in advance.

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  • Good design of mapping Java Domain objects to Tables (using Hibernate)

    - by M. McKenzie
    Hey guys, I have a question that is more in the realm of design, than implementation. I'm also happy for anyone to point out resources for the answer and I'll gladly, research for myself. Highly simplified Java and SQL: Say I have a business domain POJO called 'Picture' with three attributes. class Picture int idPicture String fileName long size Say I have another business domain POJO called "Item" with 3 attributes Class Item int idItem String itemName ArrayList itemPictures These would be a normal simple relationship. You could say that 'Picture' object, will never exist outside an 'Item' object. Assume a picture belongs only to a specific item, but that an item can have multiple pictures Now - using good database design (3rd Normal Form), we know that we should put items and pictures in their own tables. Here is what I assume would be correct. table Item int idItem (primary key) String itemName table Picture int idPicture (primary key) varchar(45) fileName long size int idItem (foreign key) Here is my question: If you are making Hibernate mapping files for these objects. In the data design, your Picture table needs a column to refer to the Item, so that a foreign key relation can be maintained. However,in your business domain objects - your Picture does not hold a reference/attribute to the idItem - and does not need to know it. A java Picture instance is always instantiated inside an Item instance. If you want to know the Item that the Picture belongs to you are already in the correct scope. Call myItem.getIdItem() and myItem.getItemPictures(),and you have the two pieces of information you need. I know that Hibernate tools have a generator that can auto make your POJO's from looking at your database. My problem stems from the fact that I planned out the data design for this experiment/project first. Then when I went to make the domain java objects, I realized that good design dictated that the objects hold other objects in a nested way. This is obviously different from the way that a database schema is - where all objects(tables) are flat and hold no other complex types within them. What is a good way to reconcile this? Would you: (A) Make the hibernate mapping files so that Picture.hbm.xml has a mapping to the POJO parent's idItem Field (if it's even possible) (B) Add an int attribute in the Picture class to refer to the idItem and set it at instantiation, thus simplifying the hbm.xml mapping file by having all table fields as local attributes in the class (C) Fix the database design because it is wrong, dork. I'd truly appreciate any feedback

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  • reading html from an inputstream java

    - by randeel wimalagunarathne
    hello everyone, I am reading a html file using an inputstream from a java servlet. But the contents of the original and the read one are in a different format although when displayed in a web browser they are the same. These are the two links for the html files after reading output http://www.fileflyer.com/view/gQREGAe orginal output http://www.fileflyer.com/view/mWXHVAE Is there a way to get the original html when reading? why is this happening? my java code is as follows; InputStreamReader isr = new InputStreamReader(inputStream); BufferedReader br = new BufferedReader(isr); String line = null; while ( (line = br.readLine()) != null) { System.out.println(line); } Any help would be greatly appreciated!! Thank you, rana.

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  • How do I configure ubuntu server's iptables to allow java without opening the floodgates?

    - by rofls
    I'm new to servers, so please bear with me. I have my amateur site running. Problem is, I followed Rackspace's instructions on setting up iptables and am pretty sure that's why the java server I'm trying to use on port 8080 isn't working (it runs the script but my android test app doesn't connect to it). When I try running the same java server script on port 80 it doesn't even start. I also ran nmap on my domain and saw that indeed only port 80 and 22 (for ssh) are responding. Is it possible to run Java and apache happily on the same server? If so, how can I configure my iptables correctly. (I'm aware that I should probably do some sort of filtering in the java server itself, but will figure that out later).

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  • Java and Different Types of Stacks

    - by Rarge
    Currently the only stack I know anything about is Vector, I normally use this in place of an array but I understand that there is other types of stacks and they all suit different jobs. The project I am currently working on requires me to be inserting objects in a certain position inside a stack, not always the front of the stack and I am under the impression that a Vector may not be the best class for this job. Could somebody please give me a brief description of the other types of stacks available to me with the Java language and their advantages and disadvantages? Are these names homogeneous? E.g. Are they only used in the Java language or are they used as general terms in Computer Science? Thank you

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  • 'void' type not allowed here error (java) help?

    - by David
    When i try to compile this: import java.awt.* ; class obj { public static void printPoint (Point p) { System.out.println ("(" + p.x + ", " + p.y + ")"); } public static void main (String[]arg) { Point blank = new Point (3,4) ; System.out.println (printPoint (blank)) ; } } i get this error: obj.java:12: 'void' type not allowed here System.out.println (printPoint (blank)) ; ^ 1 error I don't really know how to start asking about this other than to ask: What went wrong here? What does this error message mean?

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  • Deploy java (command line) app using Netbeans / ant

    - by Haes
    I've finally managed to create a Netbeans project out of an old standalone (not Web-) Java application which consisted only out of single .java sources. Now I have basically two questions regarding Netbeans Subversion interaction and application deployment: Do you check in all the Netbeans project files into the repository, normally? If I build the project using Netbeans (or ant) I get a .jar file and some additional jar libraries. In order for the app to run properly on the server, some additional config files and directories (log/ for example) are needed. The application itself is a J2SE application (no frameworks) which runs from the command line on a Linux platform. How would you deploy and install such an application? It would also be nice if I could see what version of app is currently installed (maybe by appending the version number to the installed app path). Thanks for any tips.

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  • Java/C++ communication via pipe on Windows

    - by Warlax
    Hi, I have two separate programs, one in Java and one in C++, both running on Windows. We need to do bidirectional interprocess communication between the two. Up until now, we were using this awkward solution of writing to text files and reading them on the other side, where the producer would generate a .lock file when it's done writing and the consumer would remove that when it's done reading... like I said, awkward. If we were on *nix, we would use a pipe using popen() on the C++ and RadomAccessFile on the Java side. It seems to work well. What can we do on Windows? Can we use named pipes? Thank you.

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  • Java + Eclipse + Pulpcore

    - by cable729
    I've never programmed in java or eclipse before, although I have used c# and visual studio. I'm trying to get started with java development, and develop 2d games, but I can't get the project to run. I've followed the tutorial here: http://cloningtheclassics.com/getting-started-with-pulpcore/ I've retried the tutorial at least 5 times, and I still can't get it to work. The error it displays is: Buildfile: C:\workspace\javapulp\project\build.xml [taskdef] Could not load definitions from resource tasks.properties. It could not be found. [taskdef] Could not load definitions from resource tasks.properties. It could not be found. -init: BUILD FAILED C:\workspace\javapulp\project\build.xml:127: Required file not found: ../../build/pulpcore-applet-debug-0.11.jar Total time: 1 second Thanks in advance!

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  • get entire line with java.util.scanner.hasNext(regex)

    - by Hussain
    I'm doing something in Java that requires input to be matched against the pattern ^[1-5]$. I should have a while loop looping through each line of input, checking it against the pattern, and outputting an error message if it does not. Sudo code: while (regex_match(/^[^1-5]$/,inputLine)) { print ("Please enter a number between 1 and 5! "); getNextInputLine(); } I can use java.util.Scanner.hasMatch("^[^1-5]$"), but that will only match a single token, not the entire line. Any idea on how to make hasMatch match against the entire line? (Setting the delimiter to "\n" or "\0" doesn't work.)

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  • Java respawn process

    - by Bart van Heukelom
    I'm making an editor-like program. If the user chooses File-Open in the main window I want to start a new copy of the editor process with the chosen filename as an argument. However, for that I need to know what command was used to start the first process: java -jar myapp.jar blabalsomearguments // --- need this information Open File (fileUrl) exec("java -jar myapp.jar blabalsomearguments fileUrl"); I'm not looking for an in-process solution, I've already implemented that. I'd like to have the benefits that seperate processes bring.

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  • what the java command's -jar option really does

    - by JBoy
    Does the -jar option of the java command also compile the sources before running the main method? I believe so but i would like to have a better understanding of the internal process, from the man page you can clearly see a small workflow sequence: -jar Execute a program encapsulated in a JAR file. The first argument is the name of a JAR file instead of a startup class name. In order for this option to work, the manifest of the JAR file must contain a line of the form Main-Class: classname. Here, classname identifies the class having the public static void main(String[] args) method that serves as your application's starting point. See the Jar tool reference page and the Jar trail of the Java Tutorial @ But it does not mention that it compiles the sources.

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  • The best alternative for String flyweight implementation in Java

    - by Dan
    My application is multithreaded with intensive String processing. We are experiencing excessive memory consumption and profiling has demonstrated that this is due to String data. I think that memory consumption would benefit greatly from using some kind of flyweight pattern implementation or even cache (I know for sure that Strings are often duplicated, although I don't have any hard data in that regard). I have looked at Java Constant Pool and String.intern, but it seems that it can provoke some PermGen problems. What would be the best alternative for implementing application-wide, multithreaded pool of Strings in java?

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  • A better way to do XML in Java

    - by jboyd
    There are a lot of questions that ask the best XML parser, I am more interested in what is the XML parser that is the most like Groovy for Java? I want: SomeApiDefinedObject o = parseXml( xml ); for( SomeApiDefinedObject it : o.getChildren() ) { System.out.println( it.getAttributes() ); } The most important things are that I don't want to create an object for every type of filed, I'd rather just deal with them all as strings, and that building the XML doesn't require any converters or anything, just a simple object that is already defined If you have used the Groovy XML parser, you will know what I'm talking about Alternatively, would it be better for me to just use Groovy from Java?

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  • how to show image from ms access to jpanel in java netbeans

    - by Shiv
    I have used this code : private void okActionPerformed(java.awt.event.ActionEvent evt) { try { String Update = name.getText(); Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); Connection connection = DriverManager.getConnection("jdbc:odbc:NewPData"); PreparedStatement psmnt = connection.prepareStatement("SELECT Image FROM Table1 where Name='" + Update + "'"); ResultSet rs = psmnt.executeQuery(); Blob blob = rs.getBlob("Image"); int b; InputStream bis = rs.getBinaryStream("Image"); FileOutputStream f = new FileOutputStream("Image.jpg"); while ((b = bis.read()) >= 0) { f.write(b); } f.close(); bis.close(); icon = new ImageIcon(blob.getBytes(1L, (int) blob.length())); lblImage.setIcon(icon); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } } Exception it show is java.lang.UnsupportedOperationException i have stored image first in ms access and now i want to show it on a label plz help

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  • How does java LoginContext.login() work?

    - by tangens
    I have this code to create a configuration of a java client to connect to a JBoss application server: System.setProperty( "java.security.auth.login.config", "auth.conf" ); LoginContext auth = new LoginContext( "myAuth", new LoginCallbackHandler( username, password ) ); auth.login(); The file auth.conf contains the following lines: myAuth { org.jboss.security.ClientLoginModule required; }; Now, somewhere else in the code (the LoginContext auth isn't known there) I have an EJB that does a initialContext.lookup( jndiName ) and a narrow() to access a Bean on the JBoss application server. This narrow only succeeds if the login information of the first step was correct. Question How does the login information propagate from the LoginContext to the narrow()? I don't see any connection between these two places. And further, how could I do two or more different logins inside of one client?

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  • How to run AWS sample JAVA code on an EC2

    - by SeaPlusPlus
    I just started with Amazon web services, and I have an EC2 instance. I downloaded the JAVA SDK and the Eclipse toolbox. I am able to run a sample program locally on my PC and connect to the Amazon databases, etc. My question is, what do I need to do to get this working on my EC2 instance? This may not even be specific to AWS. On Eclipse, I can just "Run as Application" and run any code. On the server side, what do I need to do? Should I ftp over my .java files? Should I export it to a jar and upload that? Do I need to install anything special to actually run it? I'm just trying to run the basic DynamoDB example that connects to the database and adds a new table and row

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  • Benchmark of Java Try/Catch Block

    - by hectorg87
    I know that going into a catch block has some significance cost when executing a program, however, I was wondering if entering a try{} block also had any impact so I started looking for an answer in google with many opinions, but no benchmarking at all. Some answers I found were: Java try/catch performance, is it recommended to keep what is inside the try clause to a minimum? Try Catch Performance Java Java try catch blocks However they didn't answer my question with facts, so I decided to try it for myself. Here's what I did. I have a csv file with this format: host;ip;number;date;status;email;uid;name;lastname;promo_code; where everything after status is optional and will not even have the corresponding ; , so when parsing a validation has to be done to see if the value is there, here's where the try/catch issue came to my mind. The current code that in inherited in my company does this: StringTokenizer st=new StringTokenizer(line,";"); String host = st.nextToken(); String ip = st.nextToken(); String number = st.nextToken(); String date = st.nextToken(); String status = st.nextToken(); String email = ""; try{ email = st.nextToken(); }catch(NoSuchElementException e){ email = ""; } and it repeats what it's done for email with uid, name, lastname and promo_code. and I changed everything to: if(st.hasMoreTokens()){ email = st.nextToken(); } and in fact it performs faster. When parsing a file that doesn't have the optional columns. Here are the average times: --- Trying:122 milliseconds --- Checking:33 milliseconds however, here's what confused me and the reason I'm asking: When running the example with values for the optional columns in all 8000 lines of the CSV, the if() version still performs better than the try/catch version, so my question is Does really the try block does not have any performance impact on my code? The average times for this example are: --- Trying:105 milliseconds --- Checking:43 milliseconds Can somebody explain what's going on here? Thanks a lot

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  • Detect file system changes on Samba share with Java on Windows

    - by GHad
    Hi, for a recent project I need to detect file system changes on a mapped Samba share from java on windows: Creates, updates and removes. At the moment I am using a folder poll that maintains a list of files and their modified timestamp to look for events. But my problem is that this folder poll only peeks into the folder at certain times (every 10 seconds for example), so an updated file can be updated twice between two polls without recognizing. Is there any way to get events from windows inside Java whenever a file event occours on that mappep Samba share? Thanks!

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