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  • c++ "interface"-like classes similar to Java?

    - by William the Coderer
    In Java, you can define an interface as a class with no actual code implementation, but only to define the methods that a class must implement. Those types can be passed as parameters to methods and returned from methods. In C++, a pure virtual class can't be used as a parameter or return type, from what I can tell. Any way to mimic Java's interface classes? I have a string class in C++, and several subclasses for different encodings (like UTFxxx, ISOxxx, etc) that derive from the base string class. However, since there are so many different encodings, the base class has no meaningful implementation. But it would serve well as an interface if I could handle it as its own object and calls to that object would call on the correct subclass it was inherited to.

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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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  • 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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  • '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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  • OSX - Update "Java for OS X 2012-002" is not mentioned on support.apple.com, is this ok?

    - by snies
    Straight after installing "Java for OS X 2012-001" Software Update asks me to install "Java for OS X 2012-002", which has the exact same size (66.6 MB) and description (including the same two links: HT5055 and HT1222) as the former, which strikes me as odd. The "Java for OS X 2012-001" is described on the apple support pages, but the "Java for OS X 2012-002" is not mentioned anywhere. Also searching on google does not yield any usable results. What is your opinon? Am i paranoid? Did you also see this update?

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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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  • 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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  • 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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  • Java NoSuchElementException using scanner.nextInt()

    - by othnin
    I am trying to read in a pgm file (512x512 array) and when I read in a larger file I get the error: java.util.NoSuchElementException on reading element (3,97). I have created a much smaller file to read (23x23) and it reads fine. Is there a size limit? I have checked the file and confirmed that there is an int for the value: This appears to be the line it crashes at: fileArray[row][col] = scan.nextInt(); Here is the file: import java.util.Scanner; import java.io.*; public class FileReader { public static void main(String[] args) throws IOException { String fileName = "lena.pgma"; int width, height, maxValue; FileInputStream fileInputStream = null; fileInputStream = new FileInputStream(fileName); Scanner scan = new Scanner(fileInputStream); // Discard the magic number scan.nextLine(); // Discard the comment line scan.nextLine(); // Read pic width, height and max value width = scan.nextInt(); System.out.println("Width: " + width); height = scan.nextInt(); System.out.println("Heigth: " + height); maxValue = scan.nextInt(); fileInputStream.close(); // Now parse the file as binary data FileInputStream fin = new FileInputStream(fileName); DataInputStream dis = new DataInputStream(fin); // look for 4 lines (i.e.: the header) and discard them int numnewlines = 4; while (numnewlines > 0) { char c; do { c = (char)(dis.readUnsignedByte()); } while (c != '\n'); numnewlines--; } // read the image data int[][] fileArray = new int[height][width]; for (int row = 0; row < height; row++) { for (int col = 0; col < width; col++) { fileArray[row][col] = scan.nextInt(); System.out.print("(" + row + " ," + col +"): " + fileArray[row][col]+ " "); } System.out.println(); } dis.close(); } } any advise would be appreciated.

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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