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  • slowAES encryption and java descryption

    - by amnon
    Hi , I've tried to implement the same steps as discussed in AES .NET but with no success , i can't seem to get java and slowAes to play toghter ... attached is my code i'm sorry i can't add more this is my first time trying to deal with encryption would appreciate any help private static final String ALGORITHM = "AES"; private static final byte[] keyValue = getKeyBytes("12345678901234567890123456789012"); private static final byte[] INIT_VECTOR = new byte[16]; private static IvParameterSpec ivSpec = new IvParameterSpec(INIT_VECTOR); public static void main(String[] args) throws Exception { String encoded = encrypt("watson?"); System.out.println(encoded); } private static Key generateKey() throws Exception { Key key = new SecretKeySpec(keyValue, ALGORITHM); // SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM); // key = keyFactory.generateSecret(new DESKeySpec(keyValue)); return key; } private static byte[] getKeyBytes(String key) { byte[] hash = DigestUtils.sha(key); byte[] saltedHash = new byte[16]; System.arraycopy(hash, 0, saltedHash, 0, 16); return saltedHash; } public static String encrypt(String valueToEnc) throws Exception { Key key = generateKey(); Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding"); c.init(Cipher.ENCRYPT_MODE, key,ivSpec); byte[] encValue = c.doFinal(valueToEnc.getBytes()); String encryptedValue = new BASE64Encoder().encode(encValue); return encryptedValue; } public static String decrypt(String encryptedValue) throws Exception { Key key = generateKey(); Cipher c = Cipher.getInstance(ALGORITHM); c.init(Cipher.DECRYPT_MODE, key); byte[] decordedValue = new BASE64Decoder().decodeBuffer(encryptedValue); byte[] decValue = c.doFinal(decordedValue); String decryptedValue = new String(decValue); return decryptedValue; } the bytes returned are different thanks in advance .

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  • Sync version of the project with Java

    - by Alexadar
    I have a problem, I need to sync version of the project. Changes are performed on main project that resides on central Coldfusion server. There are about 30 remote Coldfusion servers, that has to sync with latest version on central server. New synch application will to be done in Java! I have a direct link to each remote location. Mostly Windows OS and Windows tools are used. My idea: The synchronization is performed at the level of synchronization of folders. I would like to avoid the use of SVN and similar tools. My idea is to carry out comparison of folders on the local server (comparison is performed between the old and new versions),with NO communication with remote servers, make the difference between the versions and the same is sent to the remote machines. We will install Tomcat on every remote server. "Sync application" deployed on Tomcat will take care about differences. Remote server will return me an answer, about the success of the sync. Any kind of suggestion or completely new approach on this topic is more than welcome. Thanks Best regards

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  • implementing a Intelligent File Transfer Software in java over TCP/IP

    - by whyjava
    Hello I am working on a proposal where we have to implement a software which can move files between one source to destination.The overall goal of this project is to create intelligent file transfer.This software will have three components :- 1) Broker : Broker is the module that communicates with other brokers, monitors files, moves files, retrieves configurations from the Configuration Manager, supplies process information for the monitor, archives files, writes all process data to log files and escalates issues if necessary 2) Configuration Manager :Configuration Manager is a web-based application used to configure and deploy the configuration to all brokers. 3) Monitor : Monitor is a web-based application used to monitor each Broker in the environment. This project has to be built up in java and protocol for file transfer in tcp/ip. Client does not want to use FTP. File Transfer seems very easy, until there are several processes who are waiting to pick the file up automatically. Several problems arise: How can we guarantee the file is received at the destination? If a file isn’t received the first time, we should try it again (even after a restart or power breakdown) ? How does the receiver knows the file that is received is complete? How can we transfer multiple files synchronously? How can we protect the bandwidth, so file transfer isn’t blocking other processes? How does one interoperate between multiple OS platforms? What about authentication? How can we monitor het workflow? Auditing / logging Archiving Can you please provide answer to some of these? Thanks

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  • Fastest way to pad a number in Java to a certain number of digits

    - by Martin
    Am trying to create a well-optimised bit of code to create number of X-digits in length (where X is read from a runtime properties file), based on a DB-generated sequence number (Y), which is then used a folder-name when saving a file. I've come up with three ideas so far, the fastest of which is the last one, but I'd appreciate any advice people may have on this... 1) Instantiate a StringBuilder with initial capacity X. Append Y. While length < X, insert a zero at pos zero. 2) Instantiate a StringBuilder with initial capacity X. While length < X, append a zero. Create a DecimalFormat based on StringBuilder value, and then format the number when it's needed. 3) Create a new int of Math.pow( 10, X ) and add Y. Use String.valueOf() on the new number and then substring(1) it. The second one can obviously be split into outside-loop and inside-loop sections. So, any tips? Using a for-loop of 10,000 iterations, I'm getting similar timings from the first two, and the third method is approximately ten-times faster. Does this seem correct? Full test-method code below... // Setup test variables int numDigits = 9; int testNumber = 724; int numIterations = 10000; String folderHolder = null; DecimalFormat outputFormat = new DecimalFormat( "#,##0" ); // StringBuilder test long before = System.nanoTime(); for ( int i = 0; i < numIterations; i++ ) { StringBuilder sb = new StringBuilder( numDigits ); sb.append( testNumber ); while ( sb.length() < numDigits ) { sb.insert( 0, 0 ); } folderHolder = sb.toString(); } long after = System.nanoTime(); System.out.println( "01: " + outputFormat.format( after - before ) + " nanoseconds" ); System.out.println( "Sanity check: Folder = \"" + folderHolder + "\"" ); // DecimalFormat test before = System.nanoTime(); StringBuilder sb = new StringBuilder( numDigits ); while ( sb.length() < numDigits ) { sb.append( 0 ); } DecimalFormat formatter = new DecimalFormat( sb.toString() ); for ( int i = 0; i < numIterations; i++ ) { folderHolder = formatter.format( testNumber ); } after = System.nanoTime(); System.out.println( "02: " + outputFormat.format( after - before ) + " nanoseconds" ); System.out.println( "Sanity check: Folder = \"" + folderHolder + "\"" ); // Substring test before = System.nanoTime(); int baseNum = (int)Math.pow( 10, numDigits ); for ( int i = 0; i < numIterations; i++ ) { int newNum = baseNum + testNumber; folderHolder = String.valueOf( newNum ).substring( 1 ); } after = System.nanoTime(); System.out.println( "03: " + outputFormat.format( after - before ) + " nanoseconds" ); System.out.println( "Sanity check: Folder = \"" + folderHolder + "\"" );

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  • Transferring HashMap between client and server using Sockets (JAVA)

    - by sar
    I am working on a JAVA project in which there are multiple terminals. These terminals act as client and servers. For example if there are 3 terminals A,B and C.Then at any given point in time one of them say A, will be a client making broadcast request. The other two terminals, B and C, will reply. I am using sockets to make them communicate. Once the reply is received from all the other terminals A will check the pool of channels to see if any one of the channel is free. It takes up the free channel and making it availabilty false. The channelpool is implemented using HashMAp: HashMap channelpool = new HashMap(); channelpool = 1=true, 2=true, 3=false, 4=true, 5=true, 6=true, 7=true, 8=true, 9=true, 10=true So initially all the channels are true, any terminal can take any channel. But once the channel is taken it is set to false for the period of use and then reset to true. Now this Hashmap has to be shared among the distributed terminals. Also it should be kept up to date. I can not used a shared resource among the terminals to store the HashMap.Can someone tell me an easy way to transfer the HashMap between the terminals. I will appreciate if someone could point me to a website which discusses this.

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  • How to round a number to n decimal places in Java

    - by Alex Spurling
    What I'd like is a method to convert a double to a string which rounds using the half-up method. I.e. if the decimal to be rounded is a 5, it always rounds up the previous number. This is the standard method of rounding most people expect in most situations. I also would like only significant digits to be displayed. That is there should not be any trailing zeroes. I know one method of doing this is to use the String.format method: String.format("%.5g%n", 0.912385); returns: 0.91239 which is great, however it always displays numbers with 5 decimal places even if they are not significant: String.format("%.5g%n", 0.912300); returns: 0.91230 Another method is to use the DecimalFormatter: DecimalFormat df = new DecimalFormat("#.#####"); df.format(0.912385); returns: 0.91238 However as you can see this uses half-even rounding. That is it will round down if the previous digit is even. What I'd like is this: 0.912385 -> 0.91239 0.912300 -> 0.9123 What is the best way to achieve this in Java?

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  • Java NullPointerException In the constructor's class

    - by AndreaF
    I have made a Java class where I have defined a constructor and some methods but I get a NullPointer Exception, and I don't know how I could fix It. public class Job { String idJob; int time; int timeRun; Job j1; List<Job> startBeforeStart; List<Job> restricted; Job(String idJob, int time){ this.idJob=idJob; this.time=time; } public boolean isRestricted() { return restricted.size() != 0; } public void startsBeforeStartOf(Job job){ startBeforeStart.add(job); job.restricted.add(this); } public void startsAfterStartOf(Job job){ job.startsBeforeStartOf(this); } public void checkRestrictions(){ if (!isRestricted()){ System.out.println("+\n"); } else{ Iterator<Job> itR = restricted.iterator(); while(itR.hasNext()){ Job j1 = itR.next(); if(time>timeRun){ System.out.println("-\n"); time--; } else { restricted.remove(j1); } } } } @Override public boolean equals(Object obj) { return obj instanceof Job && ((Job) obj).idJob.equals(idJob); } public void run() { timeRun++; } } PS Looking in a forum a user says that to fix the error I should make an ArrayList inside the constructor (without modify the received parameters that should remain String id and int time), but I haven't understand what He mean.

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  • Can not issue data manipulation statements with executeQuery in java

    - by user225269
    I'm trying to insert records in mysql database using java, What do I place in this code so that I could insert records: String id; String name; String school; String gender; String lang; Scanner inputs = new Scanner(System.in); System.out.println("Input id:"); id=inputs.next(); System.out.println("Input name:"); name=inputs.next(); System.out.println("Input school:"); school= inputs.next(); System.out.println("Input gender:"); gender= inputs.next(); System.out.println("Input lang:"); lang=inputs.next(); Class.forName("com.mysql.jdbc.Driver"); Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/employee_record", "root", "MyPassword"); PreparedStatement statement = con.prepareStatement("insert into employee values('id', 'name', 'school', 'gender', 'lang');"); statement.executeUpdate();

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  • Sorting arrays in java

    - by user360706
    Write a static method in Java : public static void sortByFour (int[] arr) That receives as a paramater an array full of non-negative numbers (zero or positive) and sorts the array in the following way : In the beginning of the array all the numbers that devide by four without a remainder will appear. After them all the numbers in the array that devide by 4 with a remainder of 1 will appear. After them all the numbers in the array that devide by 4 with a remainder of 2 will appear. In the end of the array all the rest numbers (those who divide by 4 with the remainder 3) will appear. (The order of the numbers in each group doesn't matter) The method must be the most efficient it can. This is what I wrote but unfortunately it doesn't work well... :( public static void swap( int[] arr, int left, int right ) { int temp = arr[left]; arr[left] = arr[right]; arr[right] = temp; } public static void sortByFour( int[] arr ) { int left = 0; int right = ( arr.length - 1 ); int mid = ( arr.length / 2 ); while ( left < right ) { if ( ( arr[left] % 4 ) > ( arr[right] % 4 ) ) { swap( arr, left, right ); right--; } if ( ( arr[left] % 4 ) == ( arr[right] % 4 ) ) left++; else left++; } } Can someone please help me by fixing my code so that it will work well or rewriting it?

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  • java ioexception error=24 too many files open

    - by MattS
    I'm writing a genetic algorithm that needs to read/write lots of files. The fitness test for the GA is invoking a program called gradif, which takes a file as input and produces a file as output. Everything is working except when I make the population size and/or the total number of generations of the genetic algorithm too large. Then, after so many generations, I start getting this: java.io.FileNotFoundException: testfiles/GradifOut29 (Too many open files). (I get it repeatedly for many different files, the index 29 was just the one that came up first last time I ran it). It's strange because I'm not getting the error after the first or second generation, but after a significant amount of generations, which would suggest that each generation opens up more files that it doesn't close. But as far as I can tell I'm closing all of the files. The way the code is set up is the main() function is in the Population class, and the Population class contains an array of Individuals. Here's my code: Initial creation of input files (they're random access so that I could reuse the same file across multiple generations) files = new RandomAccessFile[popSize]; for(int i=0; i<popSize; i++){ files[i] = new RandomAccessFile("testfiles/GradifIn"+i, "rw"); } At the end of the entire program: for(int i=0; i<individuals.length; i++){ files[i].close(); } Inside the Individual's fitness test: FileInputStream fin = new FileInputStream("testfiles/GradifIn"+index); FileOutputStream fout = new FileOutputStream("testfiles/GradifOut"+index); Process process = Runtime.getRuntime().exec ("./gradif"); OutputStream stdin = process.getOutputStream(); InputStream stdout = process.getInputStream(); Then, later.... try{ fin.close(); fout.close(); stdin.close(); stdout.close(); process.getErrorStream().close(); }catch (IOException ioe){ ioe.printStackTrace(); } Then, afterwards, I append an 'END' to the files to make parsing them easier. FileWriter writer = new FileWriter("testfiles/GradifOut"+index, true); writer.write("END"); try{ writer.close(); }catch(IOException ioe){ ioe.printStackTrace(); } My redirection of stdin and stdout for gradif are from this answer. I tried using the try{close()}catch{} syntax to see if there was a problem with closing any of the files (there wasn't), and I got that from this answer. It should also be noted that the Individuals' fitness tests run concurrently. UPDATE: I've actually been able to narrow it down to the exec() call. In my most recent run, I first ran in to trouble at generation 733 (with a population size of 100). Why are the earlier generations fine? I don't understand why, if there's no leaking, the algorithm should be able to pass earlier generations but fail on later generations. And if there is leaking, then where is it coming from? UPDATE2: In trying to figure out what's going on here, I would like to be able to see (preferably in real-time) how many files the JVM has open at any given point. Is there an easy way to do that?

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  • Combining Java hashcodes into a "master" hashcode

    - by Nick Wiggill
    I have a vector class with hashCode() implemented. It wasn't written by me, but uses 2 prime numbers by which to multiply the 2 vector components before XORing them. Here it is: /*class Vector2f*/ ... public int hashCode() { return 997 * ((int)x) ^ 991 * ((int)y); //large primes! } ...As this is from an established Java library, I know that it works just fine. Then I have a Boundary class, which holds 2 vectors, "start" and "end" (representing the endpoints of a line). The values of these 2 vectors are what characterize the boundary. /*class Boundary*/ ... public int hashCode() { return 1013 * (start.hashCode()) ^ 1009 * (end.hashCode()); } Here I have attempted to create a good hashCode() for the unique 2-tuple of vectors (start & end) constituting this boundary. My question: Is this hashCode() implementation going to work? (Note that I have used 2 different prime numbers in the latter hashCode() implementation; I don't know if this is necessary but better to be safe than sorry when trying to avoid common factors, I guess -- since I presume this is why primes are popular for hashing functions.)

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  • Java - problems iterating through an ArrayList

    - by cc0
    Ok so I have an ArrayList (arrBok), which is full of book objects (the code is in Norwegian, so pay no attention to that please). I want to make a public method which iterates through all the objects in the arraylist. When I execute the code, it just seems to run in an infinite loop, not producing any return values. Here is the relevant (I hope, because there are a couple of other classes involved) part of the code; public String listAll() { itr = arrBok.iterator(); while (itr.hasNext()) { i++; } return "lol"; } This code does nothing useful, but I just want to see if it can iterate through it successfully. What I have tried so far; Tested if the bokArr (arraylist) is empty, which it's not. It has 4 objects inside of it. Return the toString() method of the itr, with the following result; java.util.AbstractList$Itr@173a10f // <-- not sure if this would be relevant to anything return itr.next().toString(); <-- // which seems to return the first object in the array, does that make sense?

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  • Project Euler, Problem 10 java solution now working

    - by Dennis S
    Hi, I'm trying to find the sum of the prime numbers < 2'000'000. This is my solution in java but I can't seem get the correct answer. Please give some input on what could be wrong and general advice on the code is appreciated. Printing 'sum' gives: 1308111344, which is incorrect. /* The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17. Find the sum of all the primes below two million. */ class Helper{ public void run(){ Integer sum = 0; for(int i = 2; i < 2000000; i++){ if(isPrime(i)) sum += i; } System.out.println(sum); } private boolean isPrime(int nr){ if(nr == 2) return true; else if(nr == 1) return false; if(nr % 2 == 0) return false; for(int i = 3; i < Math.sqrt(nr); i += 2){ if(nr % i == 0) return false; } return true; } } class Problem{ public static void main(String[] args){ Helper p = new Helper(); p.run(); } }

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  • Concurrency problem with arrays (Java)

    - by Johannes
    For an algorithm I'm working on I tried to develop a blacklisting mechanism that can blacklist arrays in a specific way: If "1, 2, 3" is blacklisted "1, 2, 3, 4, 5" is also considered blacklisted. I'm quite happy with the solution I've come up with so far. But there seem to be some serious problems when I access a blacklist from multiple threads. The method "contains" (see code below) sometimes returns true, even if an array is not blacklisted. This problem does not occur if I only use one thread, so it most likely is a concurrency problem. I've tried adding some synchronization, but it didn't change anything. I also tried some slightly different implementations using java.util.concurrent classes. Any ideas on how to fix this? public class Blacklist { private static final int ARRAY_GROWTH = 10; private final Node root = new Node(); private static class Node{ private volatile Node[] childNodes = new Node[ARRAY_GROWTH]; private volatile boolean blacklisted = false; public void blacklist(){ this.blacklisted = true; this.childNodes = null; } } public void add(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return; else if(currentNode.childNodes.length <= edge) { currentNode.childNodes = Arrays.copyOf(currentNode.childNodes, edge + ARRAY_GROWTH); } if(currentNode.childNodes[edge] == null) { currentNode.childNodes[edge] = new Node(); } currentNode = currentNode.childNodes[edge]; } currentNode.blacklist(); } } public boolean contains(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return true; else if(currentNode.childNodes.length <= edge || currentNode.childNodes[edge] == null) return false; currentNode = currentNode.childNodes[edge]; } return currentNode.blacklisted; } } }

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  • Override java methods without affecting parent behaviour

    - by Timmmm
    suppose I have this classes (sorry it's kind of hard to think of a simple example here; I don't want any "why would you want to do that?" answers!): class Squarer { public void setValue(int v) { mV = v; } public int getValue() { return mV; } private int mV; public void square() { setValue(getValue() * getValue()); } } class OnlyOddInputsSquarer extends Squarer { @Override public void setValue(int v) { if (v % 2 == 0) { print("Sorry, this class only lets you square odd numbers!") return; } super.setValue(v); } } auto s = new OnlyOddInputsSquarer(); s.setValue(3); s.square(); This won't work. When Squarer.square() calls setValue(), it will go to OnlyOddInputsSquarer.setValue() which will reject all its values (since all squares are even). Is there any way I can override setValue() so that all the functions in Squarer still use the method defined there? PS: Sorry, java doesn't have an auto keyword you haven't heard about! Wishful thinking on my part.

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  • Java Applet 411 Content Length

    - by user1903006
    I am new to Java. I wrote an applet with a gui that sends results (int w and int p) to a server, and I get the "411 Length Required" error. What am I doing wrong? How do you set a Content-Length? This is the method that communicates with the server: public void sendPoints1(int w, int p){ try { String url = "http://somename.com:309/api/Results"; String charset = "UTF-8"; String query = String.format("?key=%s&value=%s", URLEncoder.encode(String.valueOf(w), charset), URLEncoder.encode(String.valueOf(p), charset)); String length = String.valueOf((url + query).getBytes("UTF-8").length); HttpURLConnection connection = (HttpURLConnection) new URL(url + query).openConnection(); connection.setRequestMethod("POST"); connection.setRequestProperty("Content-Length", length); connection.connect(); System.out.println("Responce Code: " + connection.getResponseCode()); System.out.println("Responce Message: " + connection.getResponseMessage()); } catch (Exception e) { System.err.println(e.getMessage()); } }

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  • Getting a "for each" loop in Java to run in different order everytime

    - by R Stokes
    Hi, Basically my problem is that I'm trying to write a method that finds a random path in a graph of strings, which takes as it's parameters a start string, an integer length and a Vector of strings that will store the path. I'm attempting to do this by first adding the starting string to our blank vector, recursing through its neighbors until the vector's length (not including the start node) is the same as the integer length specified in the parameters. I've provided my code so far here: public Vector<String> findRandomPathFrom(String n, int len, Vector<String> randomPath){ randomPath.add(n); if (randomPath.size() == len + 1) return randomPath; for (String m : this.neighbours(n)){ if (!randomPath.contains(m) && findRandomPathFrom(m, len, randomPath) != null) return randomPath; } path.setSize(path.size() - 1); return null; } It seems to be working fine, returning a path with exactly the number of strings specified after the given start string. However, for any given starting string it generates the EXACT same path everytime, which kind of defeats the purpose of it being a random path generator. I'm guessing this problem is related to my "for each" loop, which loops through all the neighbouring strings of your current string. It seems to just be going with the first string in the neighbours vector every single time. Can anyone help me fix this problem so that it will choose a random neighbour instead of going in order? tl;dr - Any way of getting a "for each" loop in java to process a collection in a random order as oppoosed to start-to-finsih? Thanks in advance

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  • File mkdirs() method not working in android/java

    - by Leif Andersen
    I've been pulling out my hair on this for a while now. The following method is supposed to download a file, and save it to the location specified on the hard drive. private static void saveImage(Context context, boolean backgroundUpdate, URL url, File file) { if (!Tools.checkNetworkState(context, backgroundUpdate)) return; // Get the image try { // Make the file file.getParentFile().mkdirs(); // Set up the connection URLConnection uCon = url.openConnection(); InputStream is = uCon.getInputStream(); BufferedInputStream bis = new BufferedInputStream(is); // Download the data ByteArrayBuffer baf = new ByteArrayBuffer(50); int current = 0; while ((current = bis.read()) != -1) { baf.append((byte) current); } // Write the bits to the file OutputStream os = new FileOutputStream(file); os.write(baf.toByteArray()); os.close(); } catch (Exception e) { // Any exception is probably a newtork faiilure, bail return; } } Also, if the file doesn't exist, it is supposed to make the directory for the file. (And if there is another file already in that spot, it should just not do anything). However, for some reason, the mkdirs() method never makes the directory. I've tried everything from explicit parentheses, to explicitly making the parent file class, and nothing seems to work. I'm fairly certain that the drive is writable, as it's only called after that has already been determined, also that is true after running through it while debugging. So the method fails because the parent directories aren't made. Can anyone tell me if there is anything wrong with the way I'm calling it? Also, if it helps, here is the source for the file I'm calling it in: https://github.com/LeifAndersen/NetCatch/blob/master/src/net/leifandersen/mobile/android/netcatch/services/RSSService.java Thank you

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  • Java jList add item based on combobox selection

    - by Stephan Badert
    I have a csv file that is being loaded in my programme. It contains citys and areas and some other stuff (not important here). Once the csv is selected I load the data into several comboboxes. 1 Thing is not working, I have a combobox containing all the citys and now I need to list all the areas for that country based on selection from the combobox. Here is the event: private void cboProvinciesItemStateChanged(java.awt.event.ItemEvent evt) { //System.out.println(Arrays.asList(gemeentesPerProvincie(gemeentes))); invullenListProvincie(gemeentes); } Here is the method: private void invullenListProvincie(ArrayList<Gemeentes> gemeentes) { Gemeentes gf = (Gemeentes) cboProvincies.getSelectedItem(); DefaultListModel model = new DefaultListModel(); JList list = new JList(model); for (Gemeentes gemeente : gemeentesPerProvincie(gemeentes)) { model.addElement(gemeente); } lstGemeentes.setModel(model); } and this is the method to filter all the areas that equal the selection from the combobox: private ArrayList<Gemeentes> gemeentesPerProvincie(ArrayList<Gemeentes> gemeentes) { String GemPerProv = (String) cboProvincies.getSelectedItem(); ArrayList<Gemeentes> selectie = new ArrayList<Gemeentes>(); for (Gemeentes gemeente : gemeentes) { if (gemeente.getsProvincie().equals(GemPerProv)) { selectie.add(gemeente); } } return selectie; } I am convinced the error is the way I am trying to add items to the jList gemeentesPerProvincie(), I have tried so many things already. I really hope someone can see what i am clearly missing...

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  • A question on webpage representation in Java

    - by Gemma
    Hello there. I've followed a tutorial and came up with the following method to read the webpage content into a CharSequence public static CharSequence getURLContent(URL url) throws IOException { URLConnection conn = url.openConnection(); String encoding = conn.getContentEncoding(); if (encoding == null) { encoding = "ISO-8859-1"; } BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream(),encoding)); StringBuilder sb = new StringBuilder(16384); try { String line; while ((line = br.readLine()) != null) { sb.append(line); sb.append('\n'); } } finally { br.close(); } return sb; } It will return a representation of the webpage specified by the url. However,this representation is hugely different from what I use "view page source" in my Firefox,and since I need to scrape data from the original webpage(some data segement in the original "view page source" file),it will always fail to find required text on this Java representation. Did I go wrong somewhere?I need your advice guys,thanks a lot for helping!

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  • java array pass by reference does not work?

    - by stdnoit
    guys i thought almost all language including java pass array into function as reference (modifiable) but somehow it does not work here. and the testArray is still 1,2,3 with size of 3 strange enough, when if i change result[i] = 2 to a[1] =2; it work . it did pass by reference what is wrong with this code? at the end, i had a = result; (which update the a). did result get removed from stack. that is why a still get to the original a ? i am confused. thanks class Test { public static void main(String[] args) { int[] testArray = {1,2,3}; equalize(testArray, 6); System.out.println("test Array size :" + testArray.length); for(int i = 0; i < testArray.length; i++) System.out.println(testArray[i]); } public static void equalize(int[] a, int biggerSize) { if(a.length > biggerSize) throw new Error("Array size bigger than biggerSize"); int[] result = new int[biggerSize]; // System.arraycopy(a, 0, result, 0, a.length); // int array default value should be 0 for(int i = 0; i < biggerSize; i++) result[i] = 2; a = result; } }

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  • Java program will read from database, but not write to it

    - by ck1221
    I have a Java program that successfully connects to a mysql database that is hosted on godaddy's server. I can read from that db with out issue, however, when I try to write to it with INSERT or UPDATE for example, the query does not execute. I am using the 'admin' account that I set up through godaddy, I realize this is not the root account. I have checked and verified that the connection is not read only, and have logged out of phpmyadmin while the query ran. I'm not sure what else I can try or if anyone has experienced this issue. Maybe a setting to the connection I have failed to set? Or maybe its not possible since the db is hosted on godaddy's servers? Any help is great! Thanks. Here is some relevant code: Connection to db: Connection con; public DBconnection(String url, String user, String pass) { try { Class.forName("com.mysql.jdbc.Driver").newInstance(); con = DriverManager.getConnection (url,user,pass); if(!con.isClosed()) System.out.println("connecton open"); } catch (InstantiationException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();} } Send Query: public ResultSet executeQuery(String query) { ResultSet rs = null; try { Statement stmt = (Statement) con.createStatement(); rs = stmt.executeQuery(query); //while(rs.next()) //System.out.println(rs.getString("ticket_num")); } catch (SQLException e) {} return rs; } Insert Query (works in phpmyadmin): conn.executeQuery("INSERT INTO tickets VALUES(55555,'12/01/2012','me','reports','test','','','0','Nope')");

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  • Trouble swapping values as keys in generic java BST class

    - by user1729869
    I was given a generic binary search tree class with the following declaration: public class BST<K extends Comparable<K>, V> I was asked to write a method that reverses the BST such that the values become the keys and keys become values. When I call the following method (defined in the class given) reverseDict.put(originalDict.get(key), key); I get the following two error messages from Netbeans: Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - Erroneous sym type: BST.put And also: no suitable method found for put(V,K) method BST.put(BST<K,V>.Node,K,V) is not applicable (actual and formal argument lists differ in length) method BST.put(K,V) is not applicable (actual argument V cannot be converted to K by method invocation conversion) where V,K are type-variables: V extends Object declared in method <K,V>reverseBST(BST<K,V>) K extends Comparable<K> declared in method <K,V>reverseBST(BST<K,V>) From what the error messages are telling me, since my values do not extend Comparable I am unable to use them as keys. If I am right, how can I get around that without changing the class given (maybe a cast)?

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  • Trouble accessing fields of a serialized object in Java

    - by typoknig
    I have instantized a class that implements Serializable and I am trying to stream that object like this: try{ Socket socket = new Socket("localhost", 8000); ObjectOutputStream toServer = new ObjectOutputStream(socket.getOutputStream()); toServer.writeObject(myObject); } catch (IOException ex) { System.err.println(ex); } All good so far right? Then I am trying to read the fields of that object like this: //This is an inner class class HandleClient implements Runnable{ private ObjectInputStream fromClient; private Socket socket; // This socket was established earlier try { fromClient = new ObjectInputStream(socket.getInputStream()); GetField inputObjectFields = fromClient.readFields(); double myFristVariable = inputObjectFields.get("myFirstVariable", 0); int mySecondVariable = inputObjectFields.get("mySecondVariable", 0); //do stuff } catch (IOException ex) { System.err.println(ex); } catch (ClassNotFoundException ex) { System.err.println(ex); } finally { try { fromClient.close(); } catch (Exception ex) { ex.printStackTrace(); } } } But I always get the error: java.io.NotActiveException: not in call to readObject This is my first time streaming objects instead of primitive data types, what am I doing wrong? BONUS When I do get this working correctly, is the ENTIRE CLASS passed with the serialized object (i.e. will I have access to the methods of the object's class)? My reading suggests that the entire class is passed with the object, but I have been unable to use the objects methods thus far. How exactly do I call on the object's methods? In addition to my code above I also experimented with the readObject method, but I was probably using it wrong too because I couldn't get it to work. Please enlighten me.

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  • java setting resolution and print size for an Image

    - by Ingrid
    I wrote a program that generates a BufferedImage to be displayed on the screen and then printed. Part of the image includes grid lines that are 1 pixel wide. That is, the line is 1 pixel, with about 10 pixels between lines. Because of screen resolution, the image is displayed much bigger than that, with several pixels for each line. I'd like to draw it smaller, but when I scale the image (either by using Image.getScaledInstance or Graphics2D.scale), I lose significant amounts of detail. I'd like to print the image as well, and am dealing with the same problem. In that case, I am using this code to set the resolution: HashPrintRequestAttributeSet set = new HashPrintRequestAttributeSet(); PrinterResolution pr = new PrinterResolution(250, 250, ResolutionSyntax.DPI); set.add(pr); job.print(set); which works to make the image smaller without losing detail. But the problem is that the image is cut off at the same boundary as if I hadn't set the resolution. I'm also confused because I expected a larger number of DPI to make a smaller image, but it's working the other way. I'm using java 1.6 on Windows 7 with eclipse.

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