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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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  • '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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  • How to create initializeDB() method for java database

    - by Holly
    I am working on a Java project for class and have not worked much with incorporating databases into Java. I can't find much on the initializeDB() method, but if I could get some help I would really appreciate it. Below is the code being used for the intializeDB() method: private void initializeDB() { try { // Load the JDBC driver System.out.println("Driver loaded"); // Establish a connection System.out.println("Database connected"); // Create a statement // Create a SQL Query string // Execute the query to create a recordset } catch (Exception ex) { ex.printStackTrace(); } }

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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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  • Java Array Index Out of Bounds Exception

    - by user1302023
    I need help debugging the following program: I'm getting a run time error that reads: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at SearchEngine.main(SearchEngine.java:126) import java.util.*; import java.io.*; public class SearchEngine { public static int getNumberOfWords (File f) throws FileNotFoundException { int numWords = 0; Scanner scan = new Scanner(f); while (scan.hasNext()) { numWords++; scan.next(); } scan.close(); return numWords; } public static void readInWords (File input, String [] x) throws FileNotFoundException { Scanner scan = new Scanner(input); int i = 0; while (scan.hasNext() && i<x.length) { x[i] = scan.next(); i++; } scan.close(); } public static int getNumOfDistinctWords (File input, String [] x) throws FileNotFoundException { Scanner scan = new Scanner(input); int count = 0; int i = 1; while (scan.hasNext() && i<x.length) { if (!x[i].equals(x[i-1])) { count++; } i++; } scan.close(); return count; } public static void readInDistinctWords (String [] x, String [] y) { int i = 1; int k = 0; while (i<x.length) { if (!x[i].equals(x[i-1])) { y[k] = x[i]; k++; } i++; } } public static int getNumberOfLines (File input) throws FileNotFoundException { int numLines = 0; Scanner scan = new Scanner(input); while (scan.hasNextLine()) { numLines++; scan.nextLine(); } scan.close(); return numLines; } public static void readInLines (File input, String [] x) throws FileNotFoundException { Scanner scan = new Scanner(input); int i = 0; while (scan.hasNextLine() && i<x.length) { x[i] = scan.nextLine(); i++; } scan.close(); } public static void main(String [] args) { try { //gets file name System.out.println("Enter the name of the text file you wish to search"); Scanner kb = new Scanner(System.in); String fileName = kb.nextLine(); String TXT = ".txt"; if (!fileName.endsWith(TXT)) { fileName = fileName.concat(TXT); } File input = new File(fileName); //First part of creating index System.out.println("Creating vocabArray"); int NUM_WORDS = getNumberOfWords(input); //System.out.println(NUM_WORDS); String [] wordArray = new String[NUM_WORDS]; readInWords(input, wordArray); Arrays.sort(wordArray); int NUM_DISTINCT_WORDS = getNumOfDistinctWords(input, wordArray); String [] vocabArray = new String[NUM_DISTINCT_WORDS]; readInDistinctWords(wordArray, vocabArray); System.out.println("Finished creating vocabArray"); System.out.println("Creating concordanceArray"); int NUM_LINES = getNumberOfLines(input); String [] concordanceArray = new String[NUM_LINES]; readInLines(input, concordanceArray); System.out.println("Finished creating concordanceArray"); System.out.println("Creating invertedIndex"); int [][] invertedIndex = new int[NUM_DISTINCT_WORDS][10]; int [] wordCountArray = new int[NUM_DISTINCT_WORDS]; int lineNum = 0; while (lineNum<concordanceArray.length) { Scanner scan = new Scanner(concordanceArray[lineNum]); while (scan.hasNext()) { int wordPos = Arrays.binarySearch(vocabArray, scan.next()); wordCountArray[wordPos]+=1; for(int i = 0; i < invertedIndex.length; i++) { for(int j = 0; j < invertedIndex[i].length; j++) { if (invertedIndex[i][j] == 0) { invertedIndex[i][j] = lineNum; break; } } } } lineNum++; } System.out.println("Finished creating invertedIndex"); } catch (FileNotFoundException exception) { System.out.println("File Not Found"); } } //main } //class

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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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  • Using charAt in java

    - by ThuL?nå F?rñ?nDö
    This is my assignment: Write a program where the user enters a string, and the program echoes it to the monitor with one character per line: C:\>java LinePerChar Enter a string: Octopus O c t o p u s I have tried, but I'm getting some compilation errors. Here's my code: import java.util.*; class CharactorEcho{ public static void main(String args []){ Scanner sc = new Scanner(System.in); System.out.println("Enter a string :"); try { String inputString = sc.nextLine(); for(int i=0; i < sc.length(); i++) { char c = inputString.charAt(i); System.out.println("" + c); } } catch(IOException e) { } } }

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  • limit of connections with database and number of java threads in an application

    - by Jyoti
    Hi, I am working to develop a JMS application(stand alone multithreaded java application) which can receive 100 messages at a time , they need to be processed and database procedures need to be called for inserting/updating data. Procedures are very heavy as validations are also performed in them. Each procedure is taking about 30 to 50 seconds of time to execute and they are capable to run concurrently. My concern is to execute 100 procedures for all 100 messages and also send reply within time limit of 90 seconds by jms application. No application server to be used(requirement) and database is Teradata (RDBMS) I am using connection pool and thread pool in java code and testing code with 90 connections. Question is : (1) What should be the limit on number of connections with database at a time? (2) How many threads at a time are recommended? Thanks, Jyoti

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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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  • 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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  • 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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  • Writing Java code in Matlab?

    - by scooziexp
    Hi, I'm trying to use the Java commands pw.println() and br.readLine() in Matlab because I have set up a socket (input_socket2) between Matlab and a command-line program I want to control using Java classes BufferedReader and PrintWriter. Before the following snippet of code, I implemented another socket that goes between 2 computers. This works great and I also know that the following snippet of code successfully opens up a communication line between Matlab and the other program. However, Matlab throws an error at pw.println('noop'). I think it has something to do with syntax, but I'm not sure how to write the command in Matlab syntax then: try input_socket2 = Socket(host2,port2); input_stream2 = input_socket2.getInputStream; d_input_stream2 = DataInputStream(input_stream2); br = BufferedReader(InputStreamReader(input_stream2)); pw = PrintWriter(input_socket2.getOutputStream,true); pw.println('noop') br.read end Any ideas?

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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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  • 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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  • Can I add elements to a Java GUI?

    - by Asj
    I want to know how I can make a java program where an unknown amount of objects can be added to a GUI depending on user input. I can program in objects one at a time within the program, but I haven't seen a more dynamic program. Can I do that with Java? If not, what can I do it with? For more information, here's a picture. http://i6.photobucket.com/albums/y223/Asj127/CapProjIdea.jpg There can be more than one question per question block, and each question can have it's own question block.

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  • how to upload a audio file using REST webservice in Google App Engine for Java

    - by sathya
    Am using google app engine with eclipse IDE and trying to upload a audio file. I used the File Upload in Google App Engine For Java and can able to upload the file successfully. Now am planning to use REST web service for it. I had analyzed in developers.google but i failed. Can anyone suggest me how to implement REST Web services in google app engine using Eclipse. The code google provided is shown below, // file Upload.java public class Upload extends HttpServlet { private BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService(); public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { Map<String, BlobKey> blobs = blobstoreService.getUploadedBlobs(req); BlobKey blobKey = blobs.get("myFile"); if (blobKey == null) { res.sendRedirect("/"); } else { res.sendRedirect("/serve?blob-key=" + blobKey.getKeyString()); }}} // file Serve.java public class Serve extends HttpServlet { private BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService(); public void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException { BlobKey blobKey = new BlobKey(req.getParameter("blob-key")); blobstoreService.serve(blobKey, res); }} // file index.jsp <%@ page import="com.google.appengine.api.blobstore.BlobstoreServiceFactory" %> <%@ page import="com.google.appengine.api.blobstore.BlobstoreService" %> <% BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService(); %> <form action="<%= blobstoreService.createUploadUrl("/upload") %>" method="post" enctype="multipart/form-data"> <input type="file" name="myFile"> <input type="submit" value="Submit"> </form> // web.xml <servlet> <servlet-name>Upload</servlet-name> <servlet-class>Upload</servlet-class> </servlet> <servlet> <servlet-name>Serve</servlet-name> <servlet-class>Serve</servlet-class> </servlet> <servlet-mapping> <servlet-name>Upload</servlet-name> <url-pattern>/upload</url-pattern> </servlet-mapping> <servlet-mapping> <servlet-name>Serve</servlet-name> <url-pattern>/serve</url-pattern> </servlet-mapping> Now how to provide a rest web service for the above code. Kindly suggest me an idea.

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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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  • How to write web services in java

    - by gurupriyan.e
    Though this might appear as a duplicate of Java Web Services , I would like to know Where to start and to continue.In the past, I have invested so much of time to find where to start but I wasn't able to. There are so many jargons and chaos (at least for me!) while reading the pages about web services. There are so many terms - like JAX-RPC, JAX-WS, Axis, Rest, Servlet as WebService, EJB's as Web Service and other terms that I don't know. Can this User group consolidate and give a highlevel overview of Java Web Services which is easy to understand and follow? I appreciate your kindness and thanks for your help.

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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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  • Need help regarding lwuit

    - by rajiv
    Hi, I have project, already developed using canvas and lib used is LCDUI. It's for nokia keyboard supported devices. Now I want to incorporate same application for touch devices. I have used touch methods like pointerpressed, etc. For normal functionality that worked pretty well. But it creates problem in commands. My application is in fullscreen mode. Commands I have created using user defined menu list. Probles is that I can not directly identify that which command has been clicked. Setting coordinates for every command is not thr feasible solution for me. I come across the new lib LWUIT, but i found out that it supports only forms(Can't we use on canvas?). and integrating LCDUI and LWUIT is also not possible(please give suggestion that can we use both in same application?). Is it possible to create form under canvas itself? Any other lib support available? thank you.

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