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  • Simple way to repeat a String in java

    - by e5
    I'm looking for a simple commons method or operator that allows me to repeat some String n times. I know I could write this using a for loop, but I wish to avoid for loops whenever necessary and a simple direct method should exist somewhere. String str = "abc"; String repeated = str.repeat(3); repeated.equals("abcabcabc"); Related to: repeat string javascript Create NSString by repeating another string a given number of times Edited I try to avoid for loops when they are not completely necessary because: They add to the number of lines of code even if they are tucked away in another function. Someone reading my code has to figure out what I am doing in that for loop. Even if it is commented and has meaningful variables names, they still have to make sure it is not doing anything "clever". Programmers love to put clever things in for loops, even if I write it to "only do what it is intended to do", that does not preclude someone coming along and adding some additional clever "fix". They are very often easy to get wrong. For loops that involving indexes tend to generate off by one bugs. For loops often reuse the same variables, increasing the chance of really hard to find scoping bugs. For loops increase the number of places a bug hunter has to look.

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  • is this possible in java or any other programming language

    - by drake
    public abstract class Master { public void printForAllMethodsInSubClass() { System.out.println ("Printing before subclass method executes"); } } public class Owner extends Master { public void printSomething () { System.out.println ("This printed from Owner"); } public int returnSomeCals () { return 5+5; } } Without messing with methods of subclass...is it possible to execute printForAllMethodsInSubClass() before the method of a subclass gets executed?

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  • Detecting incorrect key using AES/GCM in JAVA

    - by 4r1y4n
    I'm using AES to encrypt/decrypt some files in GCM mode using BouncyCastle. While I'm proving wrong key for decryption there is no exception. How should I check that the key is incorrect? my code is this: SecretKeySpec incorrectKey = new SecretKeySpec(keyBytes, "AES"); IvParameterSpec ivSpec = new IvParameterSpec(ivBytes); Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding", "BC"); byte[] block = new byte[1048576]; int i; cipher.init(Cipher.DECRYPT_MODE, incorrectKey, ivSpec); BufferedInputStream fis=new BufferedInputStream(new ProgressMonitorInputStream(null,"Decrypting ...",new FileInputStream("file.enc"))); BufferedOutputStream ro=new BufferedOutputStream(new FileOutputStream("file_org")); CipherOutputStream dcOut = new CipherOutputStream(ro, cipher); while ((i = fis.read(block)) != -1) { dcOut.write(block, 0, i); } dcOut.close(); fis.close(); thanks

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  • Converting non-generic List type to Generic List type in Java 1.5

    - by Shaun F
    I have a List that is guaranteed to contain just one type object. This is created by some underlying code in a library that I cannot update. I want to create a List<ObjectType> based on the incoming List object so that my calling code is talking to List<ObjectType>. What's the best way to convert the List (or any other object collection) to a List<ObjectType>.

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  • Add elements to Arraylist and it replaces all previous elements in Java

    - by pie154
    I am adding elements to a ArrayList and it adds the first one correctly but then when I add any subsequent elements it wipes replaces the other elements with the value form the most recently added and adds a new element to the ArrayList. I ran test using arraylist and ints and even another created class and it worked perfectly but soemthing about the custon class i am using here causes problems. The code for the array list is public static void main(String args[]){ List<BasicEvent> list = new ArrayList<BasicEvent>(); list.add(new BasicEvent("Basic", "Door", 9, 4444, new Date(12,04,2010), new Time(12,04,21), 1, 0.98, 0)); list.add(new BasicEvent("Composite", "Door", 125, 4444, new Date(12,04,2010), new Time(12,04,20), 1, 0.98, 1)); list.add(new BasicEvent("Basic", "Door", 105, 88, new Date(12,04,2010), new Time(12,05,23), 1, 0.98, 0)); list.add(new BasicEvent("Basic", "Door", 125, 12, new Date(12,04,2010), new Time(12,05,28), 1, 0.98, 1)); list.add(new BasicEvent("Basic", "Door", 129, 25, new Date(12,04,2010), new Time(12,05,30), 1, 0.98, 0)); list.add(new BasicEvent("Basic", "Door", 125, 63, new Date(12,04,2010), new Time(12,04,20), 1, 0.98, 1)); list.add(new BasicEvent("Basic", "Detect", 127, 9, new Date(12,04,2010), new Time(12,05,29), 1, 0.98, -1)); for(int i=0;i<list.size();i++) {System.out.println("list a poition " + i + " is " + BasicEvent.basicToString(list.get(i)));} And the code for the custom class basicEvent is public class BasicEvent { public static String Level; public static String EType; public static double xPos; public static double yPos; public static Date date; public static Time time; public static double Rlb; public static double Sig; public static int Reserved; public BasicEvent(String L, String E, double X, double Y, Date D, Time T, double R, double S, int Res){ Level = L; EType = E; xPos = X; yPos = Y; date = D; time = T; Rlb = R; Sig = S; Reserved = Res; }; public static String basicToString(BasicEvent bse){ String out = bse.getLevel() + ";" + bse.getEtype() + ";" + bse.getxPos() + ";" + bse.getyPos() + ";" + bse.getDate().dateAsString() + ";" + bse.getTime().timeAsString() + ";" + bse.getRlb() + ";" + bse.getSig() + ";" + bse.getReserved(); return out; }

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  • printStackTrace in java?

    - by Venkats
    I am go through a socket program. In that printStackTrace is caught by the catch block. Actully what it is? catch(IOException ioe) { ioe.printStackTrace(); } I am unaware of it. For what they are used?

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  • Mouse event in Java

    - by Harish
    I am trying to move a JComponent say a label over a table.I am tracking this event using MouseMotionListener's mouseDragged method.This method perfectly helps me in tracking the item.Is there a way to track the mouse release after dragging is complete(.ie the dropping event). tktLabel1.addMouseMotionListener(new MouseMotionListener() { public void mouseDragged(MouseEvent arg0) { tktLabel1.setBounds(tktLabel1.getX() + arg0.getX(), tktLabel1.getY() + arg0.getY(), width, height); } public void mouseMoved(MouseEvent arg0) { } });

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  • Java multiple connections downloading file

    - by weulerjunior
    Hello friends, I was wanting to add multiple connections in the code below to be able to download files faster. Could someone help me? Thanks in advance. public void run() { RandomAccessFile file = null; InputStream stream = null; try { // Open connection to URL. HttpURLConnection connection = (HttpURLConnection) url.openConnection(); // Specify what portion of file to download. connection.setRequestProperty("Range", "bytes=" + downloaded + "-"); // Connect to server. connection.connect(); // Make sure response code is in the 200 range. if (connection.getResponseCode() / 100 != 2) { error(); } // Check for valid content length. int contentLength = connection.getContentLength(); if (contentLength < 1) { error(); } /* Set the size for this download if it hasn't been already set. */ if (size == -1) { size = contentLength; stateChanged(); } // Open file and seek to the end of it. file = new RandomAccessFile("C:\\"+getFileName(url), "rw"); file.seek(downloaded); stream = connection.getInputStream(); while (status == DOWNLOADING) { /* Size buffer according to how much of the file is left to download. */ byte buffer[]; if (size - downloaded > MAX_BUFFER_SIZE) { buffer = new byte[MAX_BUFFER_SIZE]; } else { buffer = new byte[size - downloaded]; } // Read from server into buffer. int read = stream.read(buffer); if (read == -1) { break; } // Write buffer to file. file.write(buffer, 0, read); downloaded += read; stateChanged(); } /* Change status to complete if this point was reached because downloading has finished. */ if (status == DOWNLOADING) { status = COMPLETE; stateChanged(); } } catch (Exception e) { error(); } finally { // Close file. if (file != null) { try { file.close(); } catch (Exception e) { } } // Close connection to server. if (stream != null) { try { stream.close(); } catch (Exception e) { } } } }

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  • Java Layout Insets

    - by ikurtz
    board image the above is a board layout done by using gridbaglayout. i would like insets of 5 pixels around the whole board but not between each label. i scaned the api and havent come up with something that lets me do this. does this mean i have to nest my board gui inside another gridbaglayout with the insets desired? thank you.

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  • JAVA Casting error

    - by user1612725
    Im creating a program that uses Dijksrtras algorithm, im using nodes that represent cities on an imported map, and you can create edges between two cities on the map. My problem is every edge has a "weight" where it will represent distance in minutes and i have a function where i want to see the distance between the two edges. But i keep getting the error "Cannot cast from Stad to Edge" at the line Edge<Stad> selectedEdge = (Edge) fvf.visaFörbLista.getSelectedValue(); where "Stad" represents the city and "Edge" an edge. FormVisaförbindelse fvf = new FormVisaförbindelse(); for(;;){ try{ int svar = showConfirmDialog(null, fvf, "Ändra Förbindelser", JOptionPane.OK_CANCEL_OPTION); if (svar != YES_OPTION) return; if (fvf.visaFörbLista.isSelectionEmpty() == true){ showMessageDialog(mainMethod.this, "En Förbindelse måste valjas.","Fel!", ERROR_MESSAGE); return; } Edge<Stad> selectedEdge = (Edge) fvf.visaFörbLista.getSelectedValue(); FormÄndraförbindelse faf = new FormÄndraförbindelse(); faf.setförbNamn(selectedEdge.getNamn()); for(;;){ try{ int svar2 = showConfirmDialog(mainMethod.this, faf, "Ändra Förbindelse", OK_CANCEL_OPTION); if (svar2 != YES_OPTION) return; selectedEdge.setVikt(faf.getförbTid()); List<Edge<Stad>> edges = lg.getEdgesBetween(sB, sA); for (Edge<Stad> edge : edges){ if (edge.getNamn()==selectedEdge.getNamn()){ edge.setVikt(faf.getförbTid()); } } return; } catch(NumberFormatException e){ showMessageDialog(mainMethod.this, "Ogiltig inmatning.","Fel!", ERROR_MESSAGE); }

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  • Java the little console game won't repeat?

    - by Jony Kale
    Okay, what I have so far is: You enter the game, and write "spin" to the console. Program will enter the while loop. In the while loop, if entered int is -1, return to the back (Set console input back to "", and let the user select what game he would like to play). Problem: Instead of going back, and selecting "spin" again, the program exits? Why is it happening? How can I fix this? private static Scanner console = new Scanner(System.in); private static Spin spin = new Spin(); private static String inputS = ""; private static int inputI = 0; private static String[] gamesArray = new String[] {"spin", "tof"}; private static boolean spinWheel = false; private static boolean tof = false; public static void main (String[] args) { if (inputS.equals("")) { System.out.println("Welcome to the system!"); System.out.print("Please select a game: "); inputS = console.nextLine(); } while (inputS.equals("spin")) { System.out.println("Welcome to the spin game! Please write 1 to spin. and -1 to exit back"); inputI = console.nextInt(); switch (inputI) { case 1: break; case -1: inputI = 0; inputS = ""; break; } } }

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  • Java BufferedReader readline blocking?

    - by tgguy
    I want to make an HTTP request and then get the response as sketched here: URLConnection c = new URL("http://foo.com").openConnection(); c.setDoOutput(true); /* write an http request here using a new OutputStreamWriter(c.getOutputStream) */ BufferedReader reader = new BufferedReader(new InputStreamReader(c.getInputStream)); reader.readLine(); But my question is, if the request I send takes a long time before a response is received, what happens in the call reader.readLine() above? Will this process stay running/runnable on the CPU or will it get taken off the CPU and be notified to wake up and run again when there is IO to be read? If it stays on the CPU, what can be done to make it get off and be notified later?

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  • get particular string using regex java

    - by hussain
    i want to know how to get the string from group of string String j = "<a href=\"/watch?v=4Qx-lBqOqiQ&feature=popular\" onclick=\"\" onmousedown=\"yt.analytics.urchinTracker(\'/Events/Home/PersonalizedHome/POP/Logged_Out');\" ><span class=\"video-thumb video-thumb-220 \" id=\"video-thumb-4Qx-lBqOqiQ-8821469\"><img src=\"http://i1.ytimg.com/vi/4Qx-lBqOqiQ/hqdefault.jpg\" class=\"vimg220\" alt=\"Dog Squirrel Chasing A Squirrel\" title=\"Dog Squirrel Chasing A Squirrel\" onclick=\";yt.www.watch.watch5.IEshenanigans(event, this)\"><span class=\"video-time\"><span>1:08</span></span><span class=\"video-actions\"><button class=\"yt-uix-button-short yt-uix-button yt-uix-button-arrowbutton\" onclick=\"; return false;\" type=\"button\"> <img class=\"yt-uix-button-arrow\" src=\"http://s.ytimg.com/yt/img/pixel-vfl73.gif\" alt=\"\"> hai</a>"; i want to get the string href=\"/watch?v=4Qx-lBqOqiQ&feature=popular\" and src=\"http://i1.ytimg.com/vi/4Qx-lBqOqiQ/hqdefault.jpg\" thanks and advance

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  • debugging scaffolding contingent upon degbugging boolean (java)

    - by David
    Recently i've found myself writing a lot of methods with what i can only think to call debugging scaffolding. Here's an example: public static void printArray (String[] array, boolean bug) { for (int i = 0; i<array.lenght; i++) { if (bug) System.out.print (i) ; //this line is what i'm calling the debugging scaffolding i guess. System.out.println(array[i]) ; } } in this method if i set bug to true, wherever its being called from maybe by some kind of user imput, then i get the special debugging text to let me know what index the string being printed as at just in case i needed to know for the sake of my debugging (pretend a state of affairs exists where its helpful). All of my questions more or less boil down to the question: is this a good idea? but with a tad bit more objectivity: Is this an effective way to test my methods and debug them? i mean effective in terms of efficiency and not messing up my code. Is it acceptable to leave the if (bug) stuff ; code in place after i've got my method up and working? (if a definition of "acceptability" is needed to make this question objective then use "is not a matter of programing controversy such as ommiting brackets in an if(boolean) with only one line after it, though if you've got something better go ahead and use your definition i won't mind) Is there a more effective way to accomplish the gole of making debugging easier than what i'm doing? Anything you know i mean to ask but that i have forgotten too (as much information as makes sense is appreciated).

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  • Subqueries on Java GAE Datastore

    - by Dmitry
    I am trying to create a database of users with connection between users (friends list). There are 2 main tables: UserEntity (main field id) and FriendEntity with fields: - initiatorId - id of user who initiated the friendship - friendId - id of user who has been invited. Now I am trying to fetch all friends of one particular user and encountered some problems with using subqueries in JDO here. Logically the query should be something like this: SQL: SELECT * FROM UserEntity WHERE EXISTS (SELECT * FORM FriendEntity WHERE (initiatorId == UserEntity.id && friendId == userId) || (friendId == UserEntity.id && initiatorId == userId)) or SELECT * FROM UserEntity WHERE userId IN (SELECT * FROM FriendEntity WHERE initiatorId == UserEntity.id) OR userId IN (SELECT * FROM FriendEntity WHERE friendId == UserEntity.id) So to replicate the last query in JDOQL, I tried to do the following: Query friendQuery = pm.newQuery(FriendEntity.class); friendQuery.setFilter("initiatorId == uidParam"); friendQuery.setResult("friendId"); Query initiatorQuery = pm.newQuery(FriendEntity.class); initiatorQuery.setFilter("friendId == uidParam"); initiatorQuery.setResult("initiatorId"); Query query = pm.newQuery(UserEntity.class); query.setFilter("initiatorQuery.contains(id) || friendQuery.contains(id)"); query.addSubquery(initiatorQuery, "List initiatorQuery", null, "String uidParam"); query.addSubquery(friendQuery, "List friendQuery", null, "String uidParam"); query.declareParameters("String uidParam"); List<UserEntity> friends = (List<UserEntity>) query.execute(userId); In result I get the following error: Unsupported method while parsing expression. Could anyone help with this query please?

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  • W3C dom api in Java, get child elements by name

    - by Benju
    I just realized that the method Element.getElementsByTagName("someTagName") returns a nodelist of all elements in the document that have a given tagname. What if I just want to get all child elements by tag name? For example... <person> <name>Bob</name> <car> <name>Toyota Corolla</name> </car> </person>

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  • N-tier architecture and unit tests (using Java)

    - by Alexandre FILLATRE
    Hi there, I'd like to have your expert explanations about an architectural question. Imagine a Spring MVC webapp, with validation API (JSR 303). So for a request, I have a controller that handles the request, then passes it to the service layer, which passes to the DAO one. Here's my question. At which layer should the validation occur, and how ? My though is that the controller has to handle basic validation (are mandatory fields empty ? Is the field length ok ? etc.). Then the service layer can do some tricker stuff, that involve other objets. The DAO does no validation at all. BUT, if I want to implement some unit testing (i.e. test layers below service, not the controllers), I'll end up with unexpected behavior because some validations should have been done in the Controller layer. As we don't use it for unit testing, there is a problem. What is the best way to deal with this ? I know there is no universal answer, but your personal experience is very welcomed. Thanks a lot. Regards.

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  • Type conversion between PHP client and Java webservice

    - by a1ex07
    I have a web service implemented as EJB. One of it's methods returns Map<String,String>. On client side I use php : $client = new SoapClient($wsdl,array("cache_wsdl"=>WSDL_CACHE_NONE)); $result = $client->foo($params); Everything works fine, but I would like $result-return to be an associative array. Now it looks like array(10) { [0]=> object(stdClass)#46 (2) { ["key"]=> string(4) "key1" ["value"]=> string(4) "val1" } .... I want array(10) {"key1"=>"value1", "key2"=>"value2", .... } The obvious solution is to iterate through this array and create a new array $arr = array(); foreach ($result->return as $val) $arr[$val->key] = $val->value; But I wonder if there is a better way to get an assosicative array ? Thanks in advance.

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  • Java 1.5.0_16 corrupted colours when saving jpg image

    - by Coder
    Hi, i have a loaded image from disk (stored as a BufferedImage), which i display correctly on a JPanel but when i try to re-save this image using the command below, the image is saved in a reddish hue. ImageIO.write(image, "jpg", fileName); Note! image is a BufferedImage and fileName is a File object pointing to the filename that will be saved which end in ".jpg". I have read that there were problems with ImageIO methods in earlier JDKs but i'm not on one of those versions as far as i could find. What i am looking for is a way to fix this issue without updating the JDK, however having said that i would still like to know in what JDK this issue was fixed in (if it indeed is still a bug with the JDK i'm using). Thanks.

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  • Example of ==, equals and hashcode in java

    - by Abhishek Jain
    Given this: String s1= new String("abc"); String s2= new String("abc"); String s3 ="abc"; System.out.println(s1==s3); System.out.println(s1==s2); System.out.println(s1.equals(s2)); System.out.println(s1.equals(s3)); System.out.println(s1.hashCode()); System.out.println(s2.hashCode()); System.out.println(s3.hashCode()); Output is: false false true true 96354 96354 96354 Here == is giving false for each object but hashcode for each String object is same. Why is it so?

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