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  • Roguelike FOV problem

    - by Manderin87
    I am working on a college compsci project and I would like some help with a field of view algorithm. I works mostly, but in some situations the algorithm sees through walls and hilights walls the player should not be able to see. void cMap::los(int x0, int y0, int radius) { //Does line of sight from any particular tile for(int x = 0; x < m_Height; x++) { for(int y = 0; y < m_Width; y++) { getTile(x,y)->setVisible(false); } } double xdif = 0; double ydif = 0; bool visible = false; float dist = 0; for (int x = MAX(x0 - radius,0); x < MIN(x0 + radius, m_Height); x++) { //Loops through x values within view radius for (int y = MAX(y0 - radius,0); y < MIN(y0 + radius, m_Width); y++) { //Loops through y values within view radius xdif = pow( (double) x - x0, 2); ydif = pow( (double) y - y0, 2); dist = (float) sqrt(xdif + ydif); //Gets the distance between the two points if (dist <= radius) { //If the tile is within view distance, visible = line(x0, y0, x, y); //check if it can be seen. if (visible) { //If it can be seen, getTile(x,y)->setVisible(true); //Mark that tile as viewable } } } } } bool cMap::line(int x0,int y0,int x1,int y1) { bool steep = abs(y1-y0) > abs(x1-x0); if (steep) { swap(x0, y0); swap(x1, y1); } if (x0 > x1) { swap(x0,x1); swap(y0,y1); } int deltax = x1-x0; int deltay = abs(y1-y0); int error = deltax/2; int ystep; int y = y0; if (y0 < y1) ystep = 1; else ystep = -1; for (int x = x0; x < x1; x++) { if ( steep && getTile(y,x)->isBlocked()) { getTile(y,x)->setVisible(true); getTile(y,x)->setDiscovered(true); return false; } else if (!steep && getTile(x,y)->isBlocked()) { getTile(x,y)->setVisible(true); getTile(x,y)->setDiscovered(true); return false; } error -= deltay; if (error < 0) { y = y + ystep; error = error + deltax; } } return true; } If anyone could help me make the first blocked tiles visible but stops the rest, I would appreciate it. thanks, Manderin87

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  • How do I force excel (and other office products) to stop opening files in the same application?

    - by KronoS
    Whenever I "double click" on an Excel file and another Excel file is open, the newly opened file automatically opens in the same application window as the previously opened Excel file. This isn't limited to just Excel, as I've seen Word do this as well. This poses a problem when wanting to compare documents side by side. The current solution I have for this is to actually open another Excel or Word instance, and then open the file from within that application window itself. Is there a way to force Office to open a new instance of the application when double clicking on the file icons? I'm currently using Office 2007 and Windows XP but I've seen this on Office 2010 and Windows Vista and 7. I'm looking for an overall solution if possible.

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  • Explicit method tables in C# instead of OO - good? bad?

    - by FunctorSalad
    Hi! I hope the title doesn't sound too subjective; I absolutely do not mean to start a debate on OO in general. I'd merely like to discuss the basic pros and cons for different ways of solving the following sort of problem. Let's take this minimal example: you want to express an abstract datatype T with functions that may take T as input, output, or both: f1 : Takes a T, returns an int f2 : Takes a string, returns a T f3 : Takes a T and a double, returns another T I'd like to avoid downcasting and any other dynamic typing. I'd also like to avoid mutation whenever possible. 1: Abstract-class-based attempt abstract class T { abstract int f1(); // We can't have abstract constructors, so the best we can do, as I see it, is: abstract void f2(string s); // The convention would be that you'd replace calls to the original f2 by invocation of the nullary constructor of the implementing type, followed by invocation of f2. f2 would need to have side-effects to be of any use. // f3 is a problem too: abstract T f3(double d); // This doesn't express that the return value is of the *same* type as the object whose method is invoked; it just expresses that the return value is *some* T. } 2: Parametric polymorphism and an auxilliary class (all implementing classes of TImpl will be singleton classes): abstract class TImpl<T> { abstract int f1(T t); abstract T f2(string s); abstract T f3(T t, double d); } We no longer express that some concrete type actually implements our original spec -- an implementation is simply a type Foo for which we happen to have an instance of TImpl. This doesn't seem to be a problem: If you want a function that works on arbitrary implementations, you just do something like: // Say we want to return a Bar given an arbitrary implementation of our abstract type Bar bar<T>(TImpl<T> ti, T t); At this point, one might as well skip inheritance and singletons altogether and use a 3 First-class function table class /* or struct, even */ TDictT<T> { readonly Func<T,int> f1; readonly Func<string,T> f2; readonly Func<T,double,T> f3; TDict( ... ) { this.f1 = f1; this.f2 = f2; this.f3 = f3; } } Bar bar<T>(TDict<T> td; T t); Though I don't see much practical difference between #2 and #3. Example Implementation class MyT { /* raw data structure goes here; this class needn't have any methods */ } // It doesn't matter where we put the following; could be a static method of MyT, or some static class collecting dictionaries static readonly TDict<MyT> MyTDict = new TDict<MyT>( (t) => /* body of f1 goes here */ , // f2 (s) => /* body of f2 goes here */, // f3 (t,d) => /* body of f3 goes here */ ); Thoughts? #3 is unidiomatic, but it seems rather safe and clean. One question is whether there are any performance concerns with it. I don't usually need dynamic dispatch, and I'd prefer if these function bodies get statically inlined in places where the concrete implementing type is known statically. Is #2 better in that regard?

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  • Why does my performance slow to a crawl I move methods into a base class?

    - by Juliet
    I'm writing different implementations of immutable binary trees in C#, and I wanted my trees to inherit some common methods from a base class. However, I find. I have lots of binary tree data structures to implement, and I wanted move some common methods into in a base binary tree class. Unfortunately, classes which derive from the base class are abysmally slow. Non-derived classes perform adequately. Here are two nearly identical implementations of an AVL tree to demonstrate: AvlTree: http://pastebin.com/V4WWUAyT DerivedAvlTree: http://pastebin.com/PussQDmN The two trees have the exact same code, but I've moved the DerivedAvlTree.Insert method in base class. Here's a test app: using System; using System.Collections.Generic; using System.Diagnostics; using System.Linq; using Juliet.Collections.Immutable; namespace ConsoleApplication1 { class Program { const int VALUE_COUNT = 5000; static void Main(string[] args) { var avlTreeTimes = TimeIt(TestAvlTree); var derivedAvlTreeTimes = TimeIt(TestDerivedAvlTree); Console.WriteLine("avlTreeTimes: {0}, derivedAvlTreeTimes: {1}", avlTreeTimes, derivedAvlTreeTimes); } static double TimeIt(Func<int, int> f) { var seeds = new int[] { 314159265, 271828183, 231406926, 141421356, 161803399, 266514414, 15485867, 122949829, 198491329, 42 }; var times = new List<double>(); foreach (int seed in seeds) { var sw = Stopwatch.StartNew(); f(seed); sw.Stop(); times.Add(sw.Elapsed.TotalMilliseconds); } // throwing away top and bottom results times.Sort(); times.RemoveAt(0); times.RemoveAt(times.Count - 1); return times.Average(); } static int TestAvlTree(int seed) { var rnd = new System.Random(seed); var avlTree = AvlTree<double>.Create((x, y) => x.CompareTo(y)); for (int i = 0; i < VALUE_COUNT; i++) { avlTree = avlTree.Insert(rnd.NextDouble()); } return avlTree.Count; } static int TestDerivedAvlTree(int seed) { var rnd = new System.Random(seed); var avlTree2 = DerivedAvlTree<double>.Create((x, y) => x.CompareTo(y)); for (int i = 0; i < VALUE_COUNT; i++) { avlTree2 = avlTree2.Insert(rnd.NextDouble()); } return avlTree2.Count; } } } AvlTree: inserts 5000 items in 121 ms DerivedAvlTree: inserts 5000 items in 2182 ms My profiler indicates that the program spends an inordinate amount of time in BaseBinaryTree.Insert. Anyone whose interested can see the EQATEC log file I've created with the code above (you'll need EQATEC profiler to make sense of file). I really want to use a common base class for all of my binary trees, but I can't do that if performance will suffer. What causes my DerivedAvlTree to perform so badly, and what can I do to fix it?

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  • Trying to import SQL file in a xampp server returns error

    - by Victor_J_Martin
    I have done a ER diagram in Mysql Workbench, and I am trying load in my server with phpMyAdmin, but it returns me the next error: Error SQL Query: -- ----------------------------------------------------- -- Table `BDA`.`UG` -- ----------------------------------------------------- CREATE TABLE IF NOT EXISTS `BDA`.`UG` ( `numero_ug` INT NOT NULL, `nombre` VARCHAR(45) NOT NULL, `segunda_firma_autorizada` VARCHAR(45) NOT NULL, `fecha_creacion` DATE NOT NULL, `nombre_depto` VARCHAR(140) NOT NULL, `dni` INT NOT NULL, `anho_contable` INT NOT NULL, PRIMARY KEY (`numero_ug`), INDEX `nombre_depto_idx` (`nombre_depto` ASC), INDEX `dni_idx` (`dni` ASC), INDEX `anho_contable_idx` (`anho_contable` ASC), CONSTRAINT `nombre_depto` FOREIGN KEY (`nombre_depto`) REFERENCES `BDA`.`Departamento` (`nombre_depto`) ON DELETE NO ACTION ON UPDATE NO ACTION, CONSTRAINT `dni` FOREIGN KEY (`dni`) REFERENCES `BDA`.`Trabajador` (`dni`) ON DELETE NO ACTION ON UPDATE NO ACTION, CONSTRAINT `anho_contable` FOREIGN KEY (`anho_contable`) REFERENCES `BDA`.`Capitulo_Contable` (`anho_contable`) [...] MySQL said: Documentation #1022 - Can't write; duplicate key in table 'ug' I export the result of the diagram from Mysql Workbench to a SQL file, and this file is what I'm trying to upload. This is the file. I can not find the duplicate key. SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0; SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0; SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='TRADITIONAL,ALLOW_INVALID_DATES'; CREATE SCHEMA IF NOT EXISTS `BDA` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci ; USE `BDA` ; -- ----------------------------------------------------- -- Table `BDA`.`Departamento` -- ----------------------------------------------------- CREATE TABLE IF NOT EXISTS `BDA`.`Departamento` ( `nombre_depto` VARCHAR(140) NOT NULL, `area_depto` VARCHAR(140) NOT NULL, PRIMARY KEY (`nombre_depto`)) ENGINE = InnoDB; -- ----------------------------------------------------- -- Table `BDA`.`Trabajador` -- ----------------------------------------------------- CREATE TABLE IF NOT EXISTS `BDA`.`Trabajador` ( `dni` INT NOT NULL, `direccion` VARCHAR(140) NOT NULL, `nombre` VARCHAR(45) NOT NULL, `apellidos` VARCHAR(140) NOT NULL, `fecha_nacimiento` DATE NOT NULL, `fecha_contrato` DATE NOT NULL, `titulacion` VARCHAR(140) NULL, `nombre_depto` VARCHAR(45) NOT NULL, PRIMARY KEY (`dni`), INDEX `nombre_depto_idx` (`nombre_depto` ASC), CONSTRAINT `nombre_depto` FOREIGN KEY (`nombre_depto`) REFERENCES `BDA`.`Departamento` (`nombre_depto`) ON DELETE NO ACTION ON UPDATE NO ACTION) ENGINE = InnoDB; -- ----------------------------------------------------- -- Table `BDA`.`Capitulo_Contable` -- ----------------------------------------------------- CREATE TABLE IF NOT EXISTS `BDA`.`Capitulo_Contable` ( `anho_contable` INT NOT NULL, `numero_ug` INT NOT NULL, `debe` DOUBLE NOT NULL, `haber` DOUBLE NOT NULL, PRIMARY KEY (`anho_contable`), INDEX `numero_ug_idx` (`numero_ug` ASC), CONSTRAINT `numero_ug` FOREIGN KEY (`numero_ug`) REFERENCES `BDA`.`UG` (`numero_ug`) ON DELETE NO ACTION ON UPDATE NO ACTION) ENGINE = InnoDB; -- ----------------------------------------------------- -- Table `BDA`.`UG` -- ----------------------------------------------------- CREATE TABLE IF NOT EXISTS `BDA`.`UG` ( `numero_ug` INT NOT NULL, `nombre` VARCHAR(45) NOT NULL, `segunda_firma_autorizada` VARCHAR(45) NOT NULL, `fecha_creacion` DATE NOT NULL, `nombre_depto` VARCHAR(140) NOT NULL, `dni` INT NOT NULL, `anho_contable` INT NOT NULL, PRIMARY KEY (`numero_ug`), INDEX `nombre_depto_idx` (`nombre_depto` ASC), INDEX `dni_idx` (`dni` ASC), INDEX `anho_contable_idx` (`anho_contable` ASC), CONSTRAINT `nombre_depto` FOREIGN KEY (`nombre_depto`) REFERENCES `BDA`.`Departamento` (`nombre_depto`) ON DELETE NO ACTION ON UPDATE NO ACTION, CONSTRAINT `dni` FOREIGN KEY (`dni`) REFERENCES `BDA`.`Trabajador` (`dni`) ON DELETE NO ACTION ON UPDATE NO ACTION, CONSTRAINT `anho_contable` FOREIGN KEY (`anho_contable`) REFERENCES `BDA`.`Capitulo_Contable` (`anho_contable`) ON DELETE NO ACTION ON UPDATE NO ACTION) ENGINE = InnoDB; -- ----------------------------------------------------- -- Table `BDA`.`Cliente` -- ----------------------------------------------------- CREATE TABLE IF NOT EXISTS `BDA`.`Cliente` ( `cif_cliente` INT NOT NULL, `nombre_cliente` VARCHAR(140) NOT NULL, PRIMARY KEY (`cif_cliente`)) ENGINE = InnoDB; -- ----------------------------------------------------- -- Table `BDA`.`Ingreso` -- ----------------------------------------------------- CREATE TABLE IF NOT EXISTS `BDA`.`Ingreso` ( `id` INT NOT NULL, `concepto` VARCHAR(45) NOT NULL, `importe` DOUBLE NOT NULL, `fecha` DATE NOT NULL, `cif_cliente` INT NOT NULL, `numero_ug` INT NOT NULL, PRIMARY KEY (`id`), INDEX `cif_cliente_idx` (`cif_cliente` ASC), INDEX `numero_ug_idx` (`numero_ug` ASC), CONSTRAINT `cif_cliente` FOREIGN KEY (`cif_cliente`) REFERENCES `BDA`.`Cliente` (`cif_cliente`) ON DELETE NO ACTION ON UPDATE NO ACTION, CONSTRAINT `numero_ug` FOREIGN KEY (`numero_ug`) REFERENCES `BDA`.`UG` (`numero_ug`) ON DELETE NO ACTION ON UPDATE NO ACTION) ENGINE = InnoDB; -- ----------------------------------------------------- -- Table `BDA`.`Proveedor` -- ----------------------------------------------------- CREATE TABLE IF NOT EXISTS `BDA`.`Proveedor` ( `cif_proveedor` INT NOT NULL, `nombre_proveedor` VARCHAR(140) NOT NULL, PRIMARY KEY (`cif_proveedor`)) ENGINE = InnoDB; -- ----------------------------------------------------- -- Table `BDA`.`Gasto` -- ----------------------------------------------------- CREATE TABLE IF NOT EXISTS `BDA`.`Gasto` ( `id` INT NOT NULL, `concepto` VARCHAR(45) NOT NULL, `importe` DOUBLE NOT NULL, `fecha` DATE NOT NULL, `factura` INT NOT NULL, `cif_proveedor` INT NOT NULL, `numero_ug` INT NOT NULL, PRIMARY KEY (`id`), INDEX `cif_proveedor_idx` (`cif_proveedor` ASC), INDEX `numero_ug_idx` (`numero_ug` ASC), CONSTRAINT `cif_proveedor` FOREIGN KEY (`cif_proveedor`) REFERENCES `BDA`.`Proveedor` (`cif_proveedor`) ON DELETE NO ACTION ON UPDATE NO ACTION, CONSTRAINT `numero_ug` FOREIGN KEY (`numero_ug`) REFERENCES `BDA`.`UG` (`numero_ug`) ON DELETE NO ACTION ON UPDATE NO ACTION) ENGINE = InnoDB; SET SQL_MODE=@OLD_SQL_MODE; SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS; SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS; Thanks for your advices.

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  • IOException during blocking network NIO in JDK 1.7

    - by Bass
    I'm just learning NIO, and here's the short example I've written to test how a blocking NIO can be interrupted: class TestBlockingNio { private static final boolean INTERRUPT_VIA_THREAD_INTERRUPT = true; /** * Prevent the socket from being GC'ed */ static Socket socket; private static SocketChannel connect(final int port) { while (true) { try { final SocketChannel channel = SocketChannel.open(new InetSocketAddress(port)); channel.configureBlocking(true); return channel; } catch (final IOException ioe) { try { Thread.sleep(1000); } catch (final InterruptedException ie) { } continue; } } } private static byte[] newBuffer(final int length) { final byte buffer[] = new byte[length]; for (int i = 0; i < length; i++) { buffer[i] = (byte) 'A'; } return buffer; } public static void main(final String args[]) throws IOException, InterruptedException { final int portNumber = 10000; new Thread("Reader") { public void run() { try { final ServerSocket serverSocket = new ServerSocket(portNumber); socket = serverSocket.accept(); /* * Fully ignore any input from the socket */ } catch (final IOException ioe) { ioe.printStackTrace(); } } }.start(); final SocketChannel channel = connect(portNumber); final Thread main = Thread.currentThread(); final Thread interruptor = new Thread("Inerruptor") { public void run() { System.out.println("Press Enter to interrupt I/O "); while (true) { try { System.in.read(); } catch (final IOException ioe) { ioe.printStackTrace(); } System.out.println("Interrupting..."); if (INTERRUPT_VIA_THREAD_INTERRUPT) { main.interrupt(); } else { try { channel.close(); } catch (final IOException ioe) { System.out.println(ioe.getMessage()); } } } } }; interruptor.setDaemon(true); interruptor.start(); final ByteBuffer buffer = ByteBuffer.allocate(32768); int i = 0; try { while (true) { buffer.clear(); buffer.put(newBuffer(buffer.capacity())); buffer.flip(); channel.write(buffer); System.out.print('X'); if (++i % 80 == 0) { System.out.println(); Thread.sleep(100); } } } catch (final ClosedByInterruptException cbie) { System.out.println("Closed via Thread.interrupt()"); } catch (final AsynchronousCloseException ace) { System.out.println("Closed via Channel.close()"); } } } In the above example, I'm writing to a SocketChannel, but noone is reading from the other side, so eventually the write operation hangs. This example works great when run by JDK-1.6, with the following output: Press Enter to interrupt I/O XXXX Interrupting... Closed via Thread.interrupt() — meaning that only 128k of data was written to the TCP socket's buffer. When run by JDK-1.7 (1.7.0_25-b15 and 1.7.0-u40-b37), however, the very same code bails out with an IOException: Press Enter to interrupt I/O XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXX Exception in thread "main" java.io.IOException: Broken pipe at sun.nio.ch.FileDispatcherImpl.write0(Native Method) at sun.nio.ch.SocketDispatcher.write(SocketDispatcher.java:47) at sun.nio.ch.IOUtil.writeFromNativeBuffer(IOUtil.java:93) at sun.nio.ch.IOUtil.write(IOUtil.java:65) at sun.nio.ch.SocketChannelImpl.write(SocketChannelImpl.java:487) at com.example.TestBlockingNio.main(TestBlockingNio.java:109) Can anyone explain this different behaviour?

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  • error LNK2019 and fatal error LNK1120 i get these errors in c++.

    - by user320950
    #include <iostream> #include <fstream> using namespace std; int read_file_in_array(int exam[100][3]); double calculate_total(int exam1[], int exam2[], int exam3[]); // function that calcualates grades to see how many 90,80,70,60 //void display_totals(); double exam[100][3]; int read_file_in_array(double exam[100][3]) { ifstream infile; int exam1[100]; int exam2[100]; int exam3[100]; infile.open("grades.txt");// file containing numbers in 3 columns if(infile.fail()) // checks to see if file opended { cout << "error" << endl; } int num, i=0,j=0; while(!infile.eof()) // reads file to end of line { for(i=0;i<100;i++) // array numbers less than 100 { for(j=0;j<3;j++) // while reading get 1st array or element infile >> exam[i][j]; infile >> exam[i][j]; infile >> exam[i][j]; cout << exam[i][j] << endl; { if (! (infile >> exam[i][j]) ) cout << exam[i][j] << endl; } exam[i][j]=exam1[i]; exam[i][j]=exam2[i]; exam[i][j]=exam3[i]; } infile.close(); } return 0; } i have no idea how to get these errors out. i wrote the whole code over and tried to see if it was a problem with brackets but that doesnt help either. i dont know what line it is but i believe it is in this function. error LNK2019: unresolved external symbol "int __cdecl read_file_in_array(int (* const)[3])" (?read_file_in_array@@YAHQAY02H@Z) referenced in function _main fatal error LNK1120: 1 unresolved externals // i believe this one has to do with brackets double calculate_total(int exam1[],int exam2[],int exam3[]) { int calc_tot,above90=0, above80=0, above70=0, above60=0,i,j, fail=0; int exam[100][3]; calc_tot=read_file_in_array(exam); for(i=0;i<100;i++) { exam1[i]=exam[100][0]; exam2[i]=exam[100][1]; exam3[i]=exam[100][2]; if(exam[i][j] <=90 && exam[i][j] >=100) { above90++; { if(exam[i][j] <=80 && exam[i][j] >=89) { above80++; { if(exam[i][j] <=70 && exam[i][j] >=79) { above70++; { if(exam[i][j] <=60 && exam[i][j] >=69) { above60++; { if(exam[i][j] >=59) { fail++; } } } } } } } } } } return 0; } int main() { int go,go2,go3; int exam[100][3]; int exam1[100]; int exam2[100]; int exam3[100]; go=read_file_in_array(exam); go2=calculate_total(exam1,exam2,exam3); //go3=display_totals(); cout << go,go2,go3; return 0; }

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  • C++ Greatest Number Verification

    - by Daniel
    Hey guys, I was assigned to create a program that creates n arrays composed by 10 random integers. The the program should sum all the integers and display the result. After, it has to verify which of the sums is the greatest and it has to display that array and the result. Im having troubles getting it done and would like to get some help! Thanks once again. Here is my code so far: #include <iostream> #include <iomanip> #include <cmath> using namespace std; double random(unsigned int &seed); unsigned int seed = 5; void generateData(int set[10]); int sumData(int set[10]); void checkData(int sumResult, int arrayNumber); int main (int argc, char * const argv[]) { int arrayNumber, sumResult; int set[10]; do { cout << "Number of Arrays to Compare: " << endl; cin >> arrayNumber; } while (arrayNumber < 0); for (int i = 0; i < arrayNumber; ++i) { generateData(set); sumResult = sumData(set); cout << "Sum --> " << sumResult << endl; checkData(sumResult, arrayNumber); } return 0; } double random(unsigned int &seed) { const int MODULUS = 15749; const int MULTIPLIER = 69069; const int INCREMENT = 1; seed = ((MULTIPLIER * seed) + INCREMENT) % MODULUS; return double(seed) / double(MODULUS); } void generateData(int set[10]) { for (int i = 0; i < 10; ++i) { set[i] = int (5 + 6 * random(seed)); cout << set[i] << " || "; } } int sumData(int set[10]) { int sumTotal = 0; for (int i = 0; i < 10; ++i) sumTotal = sumTotal + set[i]; return sumTotal; } void checkData(int sumResult, int arrayNumber) { int largerNumber; int tempSet[2]; for (int i = 0; i < arrayNumber; ++i) { if (sumResult > largerNumber) { tempSet[i] = sumResult; } } }

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  • My windows keyboard is being "clever" with the quote keys - how can I stop it?

    - by Marcin
    I'm using windows 7 on a laptop. On the laptop keyboard, for some reason, the quote key (which has both double and single quote on it) is doing some "clever" annoying things: When I press single-quote (or double-quote), windows doesn't send any characters until I press it twice (resulting in '' or "") When I press it before a vowel, I get some kind of accented character. As I usually only write English, this is annoying. The backtick/tilde key is subject to similar behaviour. I have not attempted to set up my computer to process anything other than English. My keyboard appears to be (in so far as these things are standard on laptops) a standard US qwerty keyboard. How can I stop this happening?

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  • Resumable upload from Java client to Grails web application?

    - by dersteps
    After almost 2 workdays of Googling and trying several different possibilities I found throughout the web, I'm asking this question here, hoping that I might finally get an answer. First of all, here's what I want to do: I'm developing a client and a server application with the purpose of exchanging a lot of large files between multiple clients on a single server. The client is developed in pure Java (JDK 1.6), while the web application is done in Grails (2.0.0). As the purpose of the client is to allow users to exchange a lot of large files (usually about 2GB each), I have to implement it in a way, so that the uploads are resumable, i.e. the users are able to stop and resume uploads at any time. Here's what I did so far: I actually managed to do what I wanted to do and stream large files to the server while still being able to pause and resume uploads using raw sockets. I would send a regular request to the server (using Apache's HttpClient library) to get the server to send me a port that was free for me to use, then open a ServerSocket on the server and connect to that particular socket from the client. Here's the problem with that: Actually, there are at least two problems with that: I open those ports myself, so I have to manage open and used ports myself. This is quite error-prone. I actually circumvent Grails' ability to manage a huge amount of (concurrent) connections. Finally, here's what I'm supposed to do now and the problem: As the problems I mentioned above are unacceptable, I am now supposed to use Java's URLConnection/HttpURLConnection classes, while still sticking to Grails. Connecting to the server and sending simple requests is no problem at all, everything worked fine. The problems started when I tried to use the streams (the connection's OutputStream in the client and the request's InputStream in the server). Opening the client's OutputStream and writing data to it is as easy as it gets. But reading from the request's InputStream seems impossible to me, as that stream is always empty, as it seems. Example Code Here's an example of the server side (Groovy controller): def test() { InputStream inStream = request.inputStream if(inStream != null) { int read = 0; byte[] buffer = new byte[4096]; long total = 0; println "Start reading" while((read = inStream.read(buffer)) != -1) { println "Read " + read + " bytes from input stream buffer" //<-- this is NEVER called } println "Reading finished" println "Read a total of " + total + " bytes" // <-- 'total' will always be 0 (zero) } else { println "Input Stream is null" // <-- This is NEVER called } } This is what I did on the client side (Java class): public void connect() { final URL url = new URL("myserveraddress"); final byte[] message = "someMessage".getBytes(); // Any byte[] - will be a file one day HttpURLConnection connection = url.openConnection(); connection.setRequestMethod("GET"); // other methods - same result // Write message DataOutputStream out = new DataOutputStream(connection.getOutputStream()); out.writeBytes(message); out.flush(); out.close(); // Actually connect connection.connect(); // is this placed correctly? // Get response BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream())); String line = null; while((line = in.readLine()) != null) { System.out.println(line); // Prints the whole server response as expected } in.close(); } As I mentioned, the problem is that request.inputStream always yields an empty InputStream, so I am never able to read anything from it (of course). But as that is exactly what I'm trying to do (so I can stream the file to be uploaded to the server, read from the InputStream and save it to a file), this is rather disappointing. I tried different HTTP methods, different data payloads, and also rearranged the code over and over again, but did not seem to be able to solve the problem. What I hope to find I hope to find a solution to my problem, of course. Anything is highly appreciated: hints, code snippets, library suggestions and so on. Maybe I'm even having it all wrong and need to go in a totally different direction. So, how can I implement resumable file uploads for rather large (binary) files from a Java client to a Grails web application without manually opening ports on the server side?

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  • UTF-8 bit representation

    - by Yanick Rochon
    I'm learning about UTF-8 standards and this is what I'm learning : Definition and bytes used UTF-8 binary representation Meaning 0xxxxxxx 1 byte for 1 à 7 bits chars 110xxxxx 10xxxxxx 2 bytes for 8 à 11 bits chars 1110xxxx 10xxxxxx 10xxxxxx 3 bytes for 12 à 16 bits chars 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx 4 bytes for 17 à 21 bits chars And I'm wondering, why 2 bytes UTF-8 code is not 10xxxxxx instead, thus gaining 1 bit all the way up to 22 bits with a 4 bytes UTF-8 code? The way it is right now, 64 possible values are lost (from 1000000 to 10111111). I'm not trying to argue the standards, but I'm wondering why this is so? ** EDIT ** Even, why isn't it UTF-8 binary representation Meaning 0xxxxxxx 1 byte for 1 à 7 bits chars 110xxxxx xxxxxxxx 2 bytes for 8 à 13 bits chars 1110xxxx xxxxxxxx xxxxxxxx 3 bytes for 14 à 20 bits chars 11110xxx xxxxxxxx xxxxxxxx xxxxxxxx 4 bytes for 21 à 27 bits chars ...? Thanks!

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  • OpenGL texture misaligned on quad

    - by user308226
    I've been having trouble with this for a while now, and I haven't gotten any solutions that work yet. Here is the problem, and the specifics: I am loading a 256x256 uncompressed TGA into a simple OpenGL program that draws a quad on the screen, but when it shows up, it is shifted about two pixels to the left, with the cropped part appearing on the right side. It has been baffling me for the longest time, people have suggested clamping and such, but somehow I think my problem is probably something really simple, but I just can't figure out what it is! Here is a screenshot comparing the TGA (left) and how it appears running in the program (right) for clarity. Also take note that there's a tiny black pixel on the upper right corner, I'm hoping that's related to the same problem. Here's the code for the loader, I'm convinced that my problem lies in the way that I'm loading the texture. Thanks in advance to anyone who can fix my problem. bool TGA::LoadUncompressedTGA(char *filename,ifstream &texturestream) { cout << "G position status:" << texturestream.tellg() << endl; texturestream.read((char*)header, sizeof(header)); //read 6 bytes into the file to get the tga header width = (GLuint)header[1] * 256 + (GLuint)header[0]; //read and calculate width and save height = (GLuint)header[3] * 256 + (GLuint)header[2]; //read and calculate height and save bpp = (GLuint)header[4]; //read bpp and save cout << bpp << endl; if((width <= 0) || (height <= 0) || ((bpp != 24) && (bpp !=32))) //check to make sure the height, width, and bpp are valid { return false; } if(bpp == 24) { type = GL_RGB; } else { type = GL_RGBA; } imagesize = ((bpp/8) * width * height); //determine size in bytes of the image cout << imagesize << endl; imagedata = new GLubyte[imagesize]; //allocate memory for our imagedata variable texturestream.read((char*)imagedata,imagesize); //read according the the size of the image and save into imagedata for(GLuint cswap = 0; cswap < (GLuint)imagesize; cswap += (bpp/8)) //loop through and reverse the tga's BGR format to RGB { imagedata[cswap] ^= imagedata[cswap+2] ^= //1st Byte XOR 3rd Byte XOR 1st Byte XOR 3rd Byte imagedata[cswap] ^= imagedata[cswap+2]; } texturestream.close(); //close ifstream because we're done with it cout << "image loaded" << endl; glGenTextures(1, &texID); // Generate OpenGL texture IDs glBindTexture(GL_TEXTURE_2D, texID); glPixelStorei(GL_UNPACK_ALIGNMENT, 1); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); glTexImage2D(GL_TEXTURE_2D, 0, type, width, height, 0, type, GL_UNSIGNED_BYTE, imagedata); delete imagedata; return true; } //Public loading function for TGA images. Opens TGA file and determines //its type, if any, then loads it and calls the appropriate function. //Returns: TRUE on success, FALSE on failure bool TGA::loadTGA(char *filename) { cout << width << endl; ifstream texturestream; texturestream.open(filename,ios::binary); texturestream.read((char*)header,sizeof(header)); //read 6 bytes into the file, its the header. //if it matches the uncompressed header's first 6 bytes, load it as uncompressed LoadUncompressedTGA(filename,texturestream); return true; }

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  • Can't get Jacobi algorithm to work in Objective-C

    - by Chris Long
    Hi, For some reason, I can't get this program to work. I've had other CS majors look at it and they can't figure it out either. This program performs the Jacobi algorithm (you can see step-by-step instructions and a MATLAB implementation here). BTW, it's different from the Wikipedia article of the same name. Since NSArray is one-dimensional, I added a method that makes it act like a two-dimensional C array. After running the Jacobi algorithm many times, the diagonal entries in the NSArray (i[0][0], i[1][1], etc.) are supposed to get bigger and the others approach 0. For some reason though, they all increase exponentially. For instance, i[2][4] should equal 0.0000009, not 9999999, while i[2][2] should be big. Thanks in advance, Chris NSArray+Matrix.m @implementation NSArray (Matrix) @dynamic offValue, transposed; - (double)offValue { double sum = 0.0; for ( MatrixItem *item in self ) if ( item.nonDiagonal ) sum += pow( item.value, 2.0 ); return sum; } - (NSMutableArray *)transposed { NSMutableArray *transpose = [[[NSMutableArray alloc] init] autorelease]; int i, j; for ( i = 0; i < 5; i++ ) { for ( j = 0; j < 5; j++ ) { [transpose addObject:[self objectAtRow:j andColumn:i]]; } } return transpose; } - (id)objectAtRow:(NSUInteger)row andColumn:(NSUInteger)column { NSUInteger index = 5 * row + column; return [self objectAtIndex:index]; } - (NSMutableArray *)multiplyWithMatrix:(NSArray *)array { NSMutableArray *result = [[NSMutableArray alloc] init]; int i = 0, j = 0, k = 0; double value; for ( i = 0; i < 5; i++ ) { value = 0.0; for ( j = 0; j < 5; j++ ) { for ( k = 0; k < 5; k++ ) { MatrixItem *firstItem = [self objectAtRow:i andColumn:k]; MatrixItem *secondItem = [array objectAtRow:k andColumn:j]; value += firstItem.value * secondItem.value; } MatrixItem *item = [[MatrixItem alloc] initWithValue:value]; item.row = i; item.column = j; [result addObject:item]; } } return result; } @end Jacobi_AlgorithmAppDelegate.m // ... - (void)jacobiAlgorithmWithEntry:(MatrixItem *)entry { MatrixItem *b11 = [matrix objectAtRow:entry.row andColumn:entry.row]; MatrixItem *b22 = [matrix objectAtRow:entry.column andColumn:entry.column]; double muPlus = ( b22.value + b11.value ) / 2.0; muPlus += sqrt( pow((b22.value - b11.value), 2.0) + 4.0 * pow(entry.value, 2.0) ); Vector *u1 = [[[Vector alloc] initWithX:(-1.0 * entry.value) andY:(b11.value - muPlus)] autorelease]; [u1 normalize]; Vector *u2 = [[[Vector alloc] initWithX:-u1.y andY:u1.x] autorelease]; NSMutableArray *g = [[[NSMutableArray alloc] init] autorelease]; for ( int i = 0; i <= 24; i++ ) { MatrixItem *item = [[[MatrixItem alloc] init] autorelease]; if ( i == 6*entry.row ) item.value = u1.x; else if ( i == 6*entry.column ) item.value = u2.y; else if ( i == ( 5*entry.row + entry.column ) || i == ( 5*entry.column + entry.row ) ) item.value = u1.y; else if ( i % 6 == 0 ) item.value = 1.0; else item.value = 0.0; [g addObject:item]; } NSMutableArray *firstResult = [[g.transposed multiplyWithMatrix:matrix] autorelease]; matrix = [firstResult multiplyWithMatrix:g]; } // ...

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  • Objective-C(iPhone SDK) - Code for Chemical Equation Balancer help

    - by Evan
    -(IBAction) balancer: (id) sender{ double M[4][4]; M[0][0] = 6.0; M[0][1] = 0.0; M[0][2] = -1.0; M[0][3] = 0.0; M[1][0] = 12.0; M[1][1] = 0.0; M[1][2] = 0.0; M[1][3] = 2.0; M[2][0] = 6.0; M[2][1] = 2.0; M[2][2] = -2.0; M[2][3] = 1.0; M[3][0] = 0.0; M[3][1] = 0.0; M[3][2] = 0.0; M[3][3] = 0.0; int rowCount = 4; int columnCount = 4; int lead = 0; for (int r = 0; r < rowCount; r++) { if (lead = columnCount) break; int i = r; while (M[i][lead] == 0) { i++; if (i == rowCount) { i = r; lead++; if (lead == columnCount){ break; } } } double temp[4] ; temp[0] = M[r][0]; temp[1] = M[r][1]; temp[2] = M[r][2]; temp[3] = M[r][3]; M[r][0] = M[i][0]; M[r][1] = M[i][1]; M[r][2] = M[i][2]; M[r][3] = M[i][3]; M[i][0] = temp[0]; M[i][1] = temp[1]; M[i][2] = temp[2]; M[i][3] = temp[3]; double lv = M[r][lead]; for (int j = 0; j < columnCount; j++) M[r][j] = M[r][j] / lv; for (int f = 0; f < rowCount; f++) { if (f != r) { double l = M[f][lead]; for (int j = 0; j < columnCount; j++) M[f][j] = M[f][j] - l * M[r][j]; } } lead++; } NSString* myNewString = [NSString stringWithFormat:@"%g",M[0][3]]; label1.text = myNewString; } This is returning NaN, while it should be returning .16666667 for M[0][3]. Any suggestions on how to fix this?

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  • Arduino Ethernet Shield Not Connecting to WebServer

    - by new user
    I have a problem making my Arduino Ethernet shield to communicate with the server, the result on the serial monitor is always: my arduino code is #include <Ethernet.h> //library for ethernet functions #include <SPI.h> #include <Dns.h> #include <Client.h> //library for client functions #include <DallasTemperature.h> //library for temperature sensors // Ethernet settings byte mac[] = {0x09,0xA2,0xDA,0x00,0x01,0x26}; //Replace with your Ethernet shield MAC byte ip[] = { 192,168,0,54}; //The Arduino device IP address byte subnet[] = { 255,255,255,0}; byte gateway[] = { 192,168,0,1}; IPAddress server(192,168,0,53); // IP-adress of server arduino sends data to EthernetClient client; bool connected = false; void setup(void) { Serial.begin(9600); Serial.println("Initializing Ethernet."); delay(1000); Ethernet.begin(mac, ip , gateway , subnet); } void loop(void) { if(!connected) { Serial.println("Not connected"); if (client.connect(server, 80)) { connected = true; int temp =analogRead(A1); Serial.print("Temp is "); Serial.println(temp); Serial.println(); Serial.println("Sending to Server: "); client.print("GET /formSubmit.php?t0="); Serial.print("GET /formSubmit.php?t0="); client.print(temp); Serial.print(temp); client.println(" HTTP/1.1"); Serial.println(" HTTP/1.1"); client.println("Host: http://localhost/PhpProject1/"); Serial.println("Host: http://localhost/PhpProject1/"); client.println("User-Agent: Arduino"); Serial.println("User-Agent: Arduino"); client.println("Accept: text/html"); Serial.println("Accept: text/html"); //client.println("Connection: close"); //Serial.println("Connection: close"); client.println(); Serial.println(); delay(10000); } else{ Serial.println("Cannot connect to Server"); } } else { delay(1000); while (client.connected() && client.available()) { char c = client.read(); Serial.print(c); } Serial.println(); client.stop(); connected = false; } } the server is an Apache server running on a pc, the server ip address in the code is the pc ip address. For testing purposes I work at my homes network, there's no proxy or firewall, and I also turned of the antivirus and firewall on my pc. the result in the serial monitor is always: Not connected Cannot connect to Server Any thoughts??

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  • Can someone explain this color wheel code to me?

    - by user1869438
    I just started doing java and i need some help with understanding this code. I got it from a this website. This is supposed to be code for a color wheel but i don't really understand how it works, especially the final ints STEPS and SLICES. import java.awt.Color; import objectdraw.*; public class ColorWheel extends WindowController { private double brightness; private Text text; private FilledRect swatch; private Location center; private int size; private FilledRect brightnessOverlay; private static final int SLICES = 96; private static final int STEPS = 16; public void begin() { canvas.setBackground(Color.BLACK); brightness = 1.; size = Math.min(canvas.getWidth(), canvas.getHeight() - 20); center = new Location(canvas.getWidth() / 2, size / 2); for(int j = STEPS; j >= 1; j--) { int arcSize = size * j / STEPS; int x = center.getX() - arcSize / 2; int y = center.getY() - arcSize / 2; for(int i = 0; i < SLICES; i++) { Color c = Color.getHSBColor((float)i / SLICES, (float)j / STEPS, (float)brightness); new FilledArc(x, y, arcSize, arcSize, i * 360. / SLICES, 360. / SLICES + .5, c, canvas); } } swatch = new FilledRect(0, canvas.getHeight() - 20, canvas.getWidth(), 20, Color.BLACK, canvas); brightnessOverlay = new FilledRect(0, 0, canvas.getWidth(), canvas.getHeight() - 20, new Color(0, 0, 0, 0), canvas); text = new Text("", canvas.getWidth() / 2, canvas.getHeight() - 18, canvas); text.setAlignment(Text.CENTER, Text.TOP); text.setBold(true); } public void onMouseDrag(Location point) { brightness = (canvas.getHeight() - point.getY()) / (double)(canvas.getHeight()); if(brightness < 0) { brightness = 0; } else if(brightness > 1) { brightness = 1; } if(brightness < .5) { text.setColor(Color.WHITE); } else { text.setColor(Color.BLACK); } brightnessOverlay.setColor(new Color(0f, 0f, 0f, (float)(1 - brightness))); } public void onMouseMove(Location point) { double saturation = 2 * center.distanceTo(point) / size; if(saturation > 1) { text.setText(""); swatch.setColor(Color.BLACK); return; } double hue = -Math.atan2(point.getY() - center.getY(), point.getX() - center.getX()) / (2 * Math.PI); if(hue < 0) { hue += 1; } swatch.setColor(Color.getHSBColor((float)hue, (float)saturation, (float)brightness)); text.setText("Color.getHSBColor(" + Text.formatDecimal(hue, 2) + "f, " + Text.formatDecimal(saturation, 2) + "f, " + Text.formatDecimal(brightness, 2) + "f)"); } }

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  • Database implementation question?

    - by gundam
    consider a disk with a sector size of 512 bytes, 2000 tracks/surface, 50 sectors/track, 5 doubled sided platters, average seek time is 10 msec. Assume a block size of 1024-byte is selected. Assume a file that contains 100,000 records of 100-byte each is to be stored on the disk, and NONE of the reocd can be spanned 2 blocks. How many blocks are needed to store the entire file?? If the file is arranged sequentially on disk, how many surfaces are required?? Now, i have calculated that 10,000 blocks are needed to store 100,000 records. But i am not sure how to find out the answer of the surfaces required. I only calculated the capacity of track is 25KB and capacity of surface is 50,000 KB But I don't know how to calculate the number of surfaces... Could anyone help me how to get the answer? Thanks a lot!!

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  • location getting some times and sometimes not

    - by Chaitanya Sai
    // in this i'm getting location sometimes and sometimes location is not retrieving i had turned gps and gprs on and added permissions required . i'm bot getting what actually the problem is package com.example.addr; import java.util.List; import java.util.Locale; import android.location.Address; import android.location.Criteria; import android.location.Geocoder; import android.location.Location; import android.location.LocationListener; import android.location.LocationManager; import android.os.Bundle; import android.app.Activity; import android.content.Context; import android.view.Menu; import android.widget.TextView; public class MainActivity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); LocationManager locationManager; String context = Context.LOCATION_SERVICE; locationManager = (LocationManager)getSystemService(context); Criteria crta = new Criteria(); crta.setAccuracy(Criteria.ACCURACY_FINE); crta.setAltitudeRequired(false); crta.setBearingRequired(false); crta.setCostAllowed(true); crta.setPowerRequirement(Criteria.POWER_LOW); String provider = locationManager.getBestProvider(crta, true); // String provider = LocationManager.GPS_PROVIDER; Location location = locationManager.getLastKnownLocation(provider); updateWithNewLocation(location); locationManager.requestLocationUpdates(provider, 2000, 10, locationListener); } private final LocationListener locationListener = new LocationListener() { @Override public void onLocationChanged(Location location) { updateWithNewLocation(location); } @Override public void onProviderDisabled(String provider) { updateWithNewLocation(null); } @Override public void onProviderEnabled(String provider) { } @Override public void onStatusChanged(String provider, int status, Bundle extras) { } }; private void updateWithNewLocation(Location location) { String latLong; TextView myLocation; myLocation = (TextView) findViewById(R.id.myLocation); String addressString = "Sorry No Address Found"; if(location!=null) { double lat = location.getLatitude(); double lon = location.getLongitude(); latLong = "Lat:" + lat + "\nLong:" + lon; double lattitude = location.getLatitude(); double longitude = location.getLongitude(); Geocoder gc = new Geocoder(this,Locale.getDefault()); try { List<Address> addresses= gc.getFromLocation(lattitude, longitude, 1); StringBuilder sb = new StringBuilder(); if(addresses.size()>0) { Address address=addresses.get(0); for(int i=0;i<address.getMaxAddressLineIndex();i++) sb.append(address.getAddressLine(i)).append("\n"); sb.append(address.getLocality()).append("\n"); sb.append(address.getPostalCode()).append("\n"); sb.append(address.getCountryName()); } addressString = sb.toString(); } catch (Exception e) { } } else { latLong = " NO Location Found "; } myLocation.setText("Current Position is :\n"+ latLong + "\n"+ addressString ); } @Override public boolean onCreateOptionsMenu(Menu menu) { getMenuInflater().inflate(R.menu.activity_main, menu); return true; } }

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  • Start a VPN session using a Terminal script

    - by craibuc
    I use an OSX Terminal session to start a VPN connection. The command that I execute at the prompt is: /etc/netlock/cvc -c :: This works as expected. I would like to save this to a script file that I can simply double-click to start. I created a file, 'vpn.command', added the command (list above), save it, and given execute permission: chmod +x vpn.command When I double-click the file, Terminal opens a BASH shell, executes the command, then exits. Upon closer inspection, the command is now '/etc/netlock/cvc -c ::; exit;' Why is the extra '; exit;' appended to my command? BTW, is there a way to execute another command, /etc/netlock/cvc -d, when the Terminal session is being closed so I can close the VPN automatically?

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  • Default Program With Multiple Versions Installed

    - by Optimal Solutions
    I have multiple versions of Excel installed. Excel 2010, 2007 and 2003. I have them installed on one hard drive with Windows 7 Ultimate as the OS. When I double-click on an XLS file, Excel 2007 opens. I would like Excel 2010 to open. I read and followed the instructions to go to the Control Panel at "Control Panel\All Control Panel Items\Default Programs" and set the default programs. I changed the default to the physical EXE for Excel 2010 at the proper folder that it is installed. When I double-click on the XLS files, Excel 2007 still opens. So I tried to change it to Excel 2003 just to see if it changed to that and it still opens Excel 2007. What am I missing? I would really like the file extension to open Excel 2010, but can not seem to do that.

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  • How to generalize a method call in Java (to avoid code duplication)

    - by dln385
    I have a process that needs to call a method and return its value. However, there are several different methods that this process may need to call, depending on the situation. If I could pass the method and its arguments to the process (like in Python), then this would be no problem. However, I don't know of any way to do this in Java. Here's a concrete example. (This example uses Apache ZooKeeper, but you don't need to know anything about ZooKeeper to understand the example.) The ZooKeeper object has several methods that will fail if the network goes down. In this case, I always want to retry the method. To make this easy, I made a "BetterZooKeeper" class that inherits the ZooKeeper class, and all of its methods automatically retry on failure. This is what the code looked like: public class BetterZooKeeper extends ZooKeeper { private void waitForReconnect() { // logic } @Override public Stat exists(String path, Watcher watcher) { while (true) { try { return super.exists(path, watcher); } catch (KeeperException e) { // We will retry. } waitForReconnect(); } } @Override public byte[] getData(String path, boolean watch, Stat stat) { while (true) { try { return super.getData(path, watch, stat); } catch (KeeperException e) { // We will retry. } waitForReconnect(); } } @Override public void delete(String path, int version) { while (true) { try { super.delete(path, version); return; } catch (KeeperException e) { // We will retry. } waitForReconnect(); } } } (In the actual program there is much more logic and many more methods that I took out of the example for simplicity.) We can see that I'm using the same retry logic, but the arguments, method call, and return type are all different for each of the methods. Here's what I did to eliminate the duplication of code: public class BetterZooKeeper extends ZooKeeper { private void waitForReconnect() { // logic } @Override public Stat exists(final String path, final Watcher watcher) { return new RetryableZooKeeperAction<Stat>() { @Override public Stat action() { return BetterZooKeeper.super.exists(path, watcher); } }.run(); } @Override public byte[] getData(final String path, final boolean watch, final Stat stat) { return new RetryableZooKeeperAction<byte[]>() { @Override public byte[] action() { return BetterZooKeeper.super.getData(path, watch, stat); } }.run(); } @Override public void delete(final String path, final int version) { new RetryableZooKeeperAction<Object>() { @Override public Object action() { BetterZooKeeper.super.delete(path, version); return null; } }.run(); return; } private abstract class RetryableZooKeeperAction<T> { public abstract T action(); public final T run() { while (true) { try { return action(); } catch (KeeperException e) { // We will retry. } waitForReconnect(); } } } } The RetryableZooKeeperAction is parameterized with the return type of the function. The run() method holds the retry logic, and the action() method is a placeholder for whichever ZooKeeper method needs to be run. Each of the public methods of BetterZooKeeper instantiates an anonymous inner class that is a subclass of the RetryableZooKeeperAction inner class, and it overrides the action() method. The local variables are (strangely enough) implicitly passed to the action() method, which is possible because they are final. In the end, this approach does work and it does eliminate the duplication of the retry logic. However, it has two major drawbacks: (1) it creates a new object every time a method is called, and (2) it's ugly and hardly readable. Also I had to workaround the 'delete' method which has a void return value. So, here is my question: is there a better way to do this in Java? This can't be a totally uncommon task, and other languages (like Python) make it easier by allowing methods to be passed. I suspect there might be a way to do this through reflection, but I haven't been able to wrap my head around it.

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  • Find duplicate images?

    - by stefan.at.wpf
    I need a software (for Windows) that finds duplicate images by comparing the actual image content. I have duplicates of images, once with metadata, one without, so the image is the same, but the file is not, so comparing the files byte by byte is not enough. Another requirement is, that I can delete all / several duplicates at once - I don't want to click 100 times "delete"! That is, what I actually would have to do using XnView ): I also checked the other topics here and Google, but if a programscompares the images in a perfect way (like XnView) it doesn't allow the deletion of several duplicates at once

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  • Database implementation question? [closed]

    - by gundam
    consider a disk with a sector size of 512 bytes, 2000 tracks/surface, 50 sectors/track, 5 doubled sided platters, average seek time is 10 msec. Assume a block size of 1024-byte is selected. Assume a file that contains 100,000 records of 100-byte each is to be stored on the disk, and NONE of the reocd can be spanned 2 blocks. How many blocks are needed to store the entire file?? If the file is arranged sequentially on disk, how many surfaces are required?? Now, i have calculated that 10,000 blocks are needed to store 100,000 records. But i am not sure how to find out the answer of the surfaces required. I only calculated the capacity of track is 25KB and capacity of surface is 50,000 KB But I don't know how to calculate the number of surfaces... Could anyone help me how to get the answer? Thanks a lot!!

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  • Java.lang.NullPointerException when using retreived Image (Unless method is used statically!)

    - by Emdiesse
    Hi there, This has been doing my head in all day and I have finally decided to resort to asking for help! In my MIDLet I have an instance of the java class ImageFetcher called anImg. Also within my MIDLet I have a command that simply say's fetch, a CommandListener that when detects fetch was clicked runs the function below. This function should simply run public getImage() from the anImg instance of class ImageFetcher which returns an image and then appends/sets this Image onto the form on the display. (You may recognise the getImage() function from the Nokia JavaME Wiki!!!) Instead of any image being displayed this is written to the output terminal in netbeans: Msg: Java.lang.NullPointerException HOWEVER, If I change public getImage() to public static getImage() and replace anImg.getImage() with ImageFetcher.getImage() the image is successfully displayed!!! Thank you for your replies on this issue :) I look forward to going my hair back after this ordeal! FetchImageApp.java ... ... ... private doThis(){ try { Image im; if ((im = anImg.getImage()) != null) { ImageItem ii = new ImageItem(null, im, ImageItem.LAYOUT_DEFAULT, null); // If there is already an image, set (replace) it if (form.size() != 0) { form.set(0, ii); } else // Append the image to the empty form { form.append(ii); } } else { form.append("Unsuccessful download."); } // Display the form with the image display.setCurrent(form); } catch (Exception e) { System.err.println("Msg: " + e.toString()); } } ... ... ... ImageFetcher.java ... ... ... /*-------------------------------------------------- * Open connection and download png into a byte array. *-------------------------------------------------*/ public Image getImage() throws IOException { String url = "http://kenai.com/attachments/wiki_images/chessgame/java-duke-logo.png"; ContentConnection connection = (ContentConnection) Connector.open(url); // * There is a bug in MIDP 1.0.3 in which read() sometimes returns // an invalid length. To work around this, I have changed the // stream to DataInputStream and called readFully() instead of read() // InputStream iStrm = connection.openInputStream(); DataInputStream iStrm = connection.openDataInputStream(); ByteArrayOutputStream bStrm = null; Image im = null; try { // ContentConnection includes a length method byte imageData[]; int length = (int) connection.getLength(); if (length != -1) { imageData = new byte[length]; // Read the png into an array // iStrm.read(imageData); iStrm.readFully(imageData); } else // Length not available... { bStrm = new ByteArrayOutputStream(); int ch; while ((ch = iStrm.read()) != -1) { bStrm.write(ch); } imageData = bStrm.toByteArray(); bStrm.close(); } // Create the image from the byte array im = Image.createImage(imageData, 0, imageData.length); } finally { // Clean up if (iStrm != null) { iStrm.close(); } if (connection != null) { connection.close(); } if (bStrm != null) { bStrm.close(); } } return (im == null ? null : im); } ... ... ...

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