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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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  • 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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  • Java Days & Bookings

    - by sys_debug
    Ok this is an extension of a question I asked about earlier yet this is the next step that is unclear to me. Everything else will be ready and this part is driving me mad! some members provided great help and I already made progress with that info, but this is just another obstacle. I am creating a booking object (as was suggested) that will have a start date and end date. each booking will also have a number of seats associated with it (that I require to reserve). The total available number of seats any given day 46 (as the total capacity of the hall is 46 seats). so in assumption that I have a booking to be made in the system, and start date is 1st jan and end date is 10th jan. The question is how can I check the remaining seats in all those days between the range to see if requested number could be hosted or not? and then when the second booking is made, it will have to see that the days in this range already have less than 46 and decrement further if possible to host the reservation. one of the members, and I appreciate his effort, gladly contributed a method to compare if this booking is after or before the existing bookings. The code provided is here: public boolean overlapsWithExisting(Booking booking) { final Date early = booking.getStart(); final Date late = booking.getEnd(); for(Booking existing : existingBookings) { if(!(early.isAfter(existing.getEnd() || late.isBefore(existing.getStart())) return true; } return false; } I just want to know how to associate 46 with each day and keep record of days that are decremented by bookings. Thanks and reallllllly appreciated :D

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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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  • Java RSA Encrypt using .NET XML Key File - need help

    - by badMonkey
    In .net I have generated the following public key file: <RSAKeyValue> <Modulus>xTSiS4+I/x9awUXcF66Ffw7tracsQfGCn6g6k/hGkLquHYMFTCYk4mOB5NwLwqczwvl8HkQfDShGcvrm47XHKUzA8iadWdA5n4toBECzRxiCWCHm1KEg59LUD3fxTG5ogGiNxDj9wSguCIzFdUxBYq5ot2J4iLgGu0qShml5vwk=</Modulus> <Exponent>AQAB</Exponent> .NET is happy to encrypt using it's normal methods. I am trying to use this key to encode a string in Java and am running into an Arithmetic problem (exception) when I attempt to encrypt the string. The following is the code I am using to encrypt: byte[] modulusBytes = Base64.decode(this.getString(R.string.public_key_modulus)); byte[] exponentBytes = Base64.decode(this.getString(R.string.public_key_exponent)); BigInteger modulus = new BigInteger( modulusBytes ); BigInteger exponent = new BigInteger( exponentBytes); RSAPublicKeySpec rsaPubKey = new RSAPublicKeySpec(modulus, exponent); KeyFactory fact = KeyFactory.getInstance("RSA"); PublicKey pubKey = fact.generatePublic(rsaPubKey); Cipher cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.ENCRYPT_MODE, pubKey); byte[] cipherData = cipher.doFinal( new String("big kitty dancing").getBytes() ); It is the final line in the code block that fails. I have looked at numerous examples and this is the best I could come up with. If it is not obvious, the R.string.public_key_modulus is a copy/paste of the text in the Modulus element, same applies for exponent.

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  • Highlighting Changes in Java

    - by Buzz Lightyear
    Basically, i have done my program so that it will display differences in strings and display the whole line. I want to highlight (in a colour) the differences in the line. Example: Original at line 5 <rect x="60.01" width="855.38" id="rect_1" y="-244.35" height="641.13" style="stroke-width: 1; stroke: rgb(0, 0, 0); fill: none; "/> Edited at line 5 <rect x="298.43" width="340.00" y="131.12" height="380.00" id="rect_1" style="stroke-width: 1; stroke: rgb(0, 0, 0); fill: rgb(255, 102, 0); "/> In this example, the width is different from the 'original' from the 'edited' version. I would like to be able to highlight that difference and any other difference. My code so far: Patch patch = DiffUtils.diff(centralFile, remoteFile); StringBuffer resultsBuff = new StringBuffer(remoteFileData.length); for (Delta delta : patch.getDeltas()) { resultsBuff.append("Original at line " + delta.getOriginal().getPosition() + "\n"); for (Object line : delta.getOriginal().getLines()) { resultsBuff.append(" " + line + "\n"); } resultsBuff.append("Edited at line " + delta.getRevised().getPosition() + "\n"); for (Object line : delta.getRevised().getLines()) { resultsBuff.append(" " + line + "\n"); } resultsBuff.append("\n"); } return resultsBuff.toString(); } That will display two whole lines like the example before (the original and the edited version) I want to be able to highlight the changes that have actually been made, is there any way to do this in Java?

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  • Java SOAP - Need help on Body and ChildElement manipulation

    - by techventure
    Hi guys I'm trying to write some code in java to learn more about coding with WSDL and SOAP. I've been able to build up a BodyElement for a given namespace. But when i come to adding the childElements I'm runnig intp problems. For example given :'<'to:checkAccount xmlns:to="http://foo" '<'to:id test' <'/to:id '<'to:password test '<'/to:password '<'to:checkAccount " I'm able to set the bodyElement(to:checkAccount), but when i try to add the childElements (to:id, to:password) , the childElement needs to have the "to" prefix otherwise it won't work. ie. sf = SOAPFactory.newInstance(); Name childName = sf.createName("id"); SOAPElement symbol = bodyElement.addChildElement(childName); this doesn't work since it doesn't have the "to" prefix to id and password. I cannot do Name childName = sf.createName("id","to",null); as it gives me an error saying wrong namespace... can someone tell me how i can add to:id and to:password to to:checkAccount ?

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  • Efficient mapping of game entity positions in Java

    - by byte
    In Java (Swing), say I've got a 2D game where I have various types of entities on the screen, such as a player, bad guys, powerups, etc. When the player moves across the screen, in order to do efficient checking of what is in the immediate vicinity of the player, I would think I'd want indexed access to the things that are near the character based on their position. For example, if player 'P' steps onto element 'E' in the following example... | | | | | | | | | |P| | | | |E| | | | | | | | | ... would be to do something like: if(player.getPosition().x == entity.getPosition().x && entity.getPosition.y == thing.getPosition().y) { //do something } And thats fine, but that implies that the entities hold their positions, and therefor if I had MANY entities on the screen I would have to loop through all possible entities available and check each ones position against the player position. This seems really inefficient especially if you start getting tons of entities. So, I would suspect I'd want some sort of map like Map<Point, Entity> map = new HashMap<Point, Entity>(); And store my point information there, so that I could access these entities in constant time. The only problem with that approach is that, if I want to move an entity to a different point on the screen, I'd have to search through the values of the HashMap for the entity I want to move (inefficient since I dont know its Point position ahead of time), and then once I've found it remove it from the HashMap, and re-insert it with the new position information. Any suggestions or advice on what sort of data structure / storage format I ought to be using here in order to have efficient access to Entities based on their position, as well as Position's based on the Entity?

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  • Send string from java (or other platform) to application

    - by MrSnowflake
    I want to send a barcode, read with my cellphone, to my computer. My computer has a simple server running, which listens to barcodes. When a barcode arrives, the server app should be able to input the value of the received barcode into the active application (I don't really care which application is going to get the input, the user should be able to select gedit, a terminal window or the browser if they choose to). My language at the moment is Java on GNU/Linux (Ubuntu), so I know about the Robot class. But the Robot class emulates a keyboard, which means: when you send VK_1 on a US keyboard layout, the output is '1' indeed, but when you send VK_1 on another layout (like belgian, which I use), which requires shift for the '1' key, the output is '&' (this is the character on the '1' key, when you don't hold shift). I also found xsendkeys, but this application too requires you to specify whether you need to hold shift. So it will be able to send an 'a' but for an 'A' (thus capital) you need to specify you want to hold shift with your 'a'. Isn't there an easy way to do this, for GNU/Linux and Windows, just using strings. I want to be able to send "12a68dd" to the active application. And I also would like to be able to send UTF-8 characters to the active application. I have been looking for a solution, but most require the breakdown in multiple keystrokes, which are often dependent on the keyboard layout.

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  • Working with Java using methods and arrays [closed]

    - by jordan
    Hi i'm a newb at java and for one of my labs I have to create a instant messenger client with these requirements: add buddyList instance variable add IMClient constructor to create ArrayList addBuddy method removeBuddy method findBuddy method printBuddyList method what's the best way to go about this? so far I have this: public class IMClient { private String userId; // User id private String password; // Password private int status; // Status code for user: 1 - Online, 2 - Off-line, 3 - Away public IMClient(String userId, String password, int status) { super(); this.userId = userId; this.password = password; this.status = status; } // Returns true if password as a parameter matches password instance variable. public boolean checkPassword(String password) { return this.password.equals(password); } public String toString() { StringBuffer buf = new StringBuffer(100); buf.append(" User id: "); buf.append(userId); buf.append(" Password: "); buf.append(password); buf.append(" Status: "); buf.append(status); return buf.toString(); } public String getUserId() { return userId; } public void setUserId(String userId) { this.userId = userId; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public int getStatus() { return status; } public void setStatus(int status) { this.status = status; } public static void main(String[] args) { } }

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  • Help me find article on Multi-threading and Event Handling in Java

    - by JDR
    I once read an article on how to properly write event handlers for multi-threading in Java, but I can't for the life of me find it anymore. It described the pitfalls and potentials for deadlocks that can occur when firing events (not Swing events mind you, but general events like model update notifications). To clarify, the situation would be as such: // let's say this is code from an MVC model somewhere public void setSomeProperty(String myProperty){ if(!this.myProperty.equals(myProperty)){ this.myProperty = myProperty; fireMyPropertyChangedEvent(...); } } The article described how passing control to arbitrary external listener code was a potential cause for deadlock. I now find myself in a situation where I need to fire such events in a multithreaded environment and I would very much like to read the article again to see what it has to say before I continue. Does anyone know the article I'm referring to? I believe it came as a (fairly short) PDF. It started off with an initial naive implementation and incrementally pointed out flaws and improved upon it. It ended with a sort of final proper-way-to-fire-multithreaded-events. I've searched endlessly in my browse history and on google, but all I could find were endless amounts topics on Swing event dispatch threads. Thank you.

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  • java hashmap array to double array

    - by Tweety
    Hi, I declared LinkedHashMap<String, float[]> and now I want to convert float[] values into double[][]. I am using following code. LinkedHashMap<String, float[]> fData; double data[][] = null; Iterator<String> iter = fData.keySet().iterator(); int i = 0; while (iter.hasNext()) { faName = iter.next(); tValue = fData.get(faName); //data = new double[fData.size()][tValue.length]; for (int j = 0; j < tValue.length; j++) { data[i][j] = tValue[j]; } i++; } When I try to print data System.out.println(Arrays.deepToString(data)); it doesn't show the data :( I tried to debug my code and i figured out that I have to initialize data outside the while loop but then I don't know the array dimensions :( How to solve it? Thanks

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  • how to add data in Table of Jasper Report using Java

    - by Areeb Gillani
    i am here to ask you just a simple question that i am trying to pass data to a jasper report using java but i dont know how to to, because the table data is very dynamic thats y cannot pass sql query. any idea for this. i have a 2D array of object type, where i have all the data... so how can i pass that... Thanx in advance...!:) ConnectionManager con = new ConnectionManager(); con.establishConnection(); String fileName = "Pmc_Bill.jrxml"; String outFileName = "OutputReport.pdf"; HashMap params = new HashMap(); params.put("PName", pname); params.put("PSerial", psrl); params.put("PGender",pgen); params.put("PPhone",pph); params.put("PAge",page); params.put("PRefer",pref); params.put("PDateR",dateNow); try { JasperReport jasperReport = JasperCompileManager.compileReport(fileName); if(jasperReport != null ) System.out.println("so far so good "); // Fill the report using an empty data source JasperPrint jasperPrint = JasperFillManager.fillReport(jasperReport, params, new JRTableModelDataSource(tbl.getModel()));//con.connection); try{ JasperExportManager.exportReportToPdfFile(jasperPrint, outFileName); System.out.printf("File exported sucessfully"); }catch(Exception e){ e.printStackTrace(); } JasperViewer.viewReport(jasperPrint); } catch (JRException e) { JOptionPane.showMessageDialog(null, e); e.printStackTrace(); System.exit(1); }

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  • graph and all pairs shortest path in java

    - by Sandra
    I am writing a java program using Flyod-Warshall algorithm “All pairs shortest path”. I have written the following : a0 is the adjacency matrix of my graph, but has infinity instead of 0. vList is the list of vertexes and the cost for each edge is 1. Path[i][j] = k+1 means for going from I to j you first go to k then j int[][] path = new int[size][size]; for(int i = 0; i<path.length;i++) { for(int j = 0; j<path.length; j++) { if(adjM[i][j]==1) path[i][j]=j+1; } } //*************** for (int k = 0; k < vList.size(); k++) for (int i = 0; i < vList.size(); i++) for (int j = 0; j < vList.size(); j++) { if (a0[i][j]>a0[i][k]+ a0[k][j]) path[i][j] = k + 1; a0[i][j] = Math.min(a0[i][j], a0[i][k] + a0[k][j]); } After running this code, in the result a0 is correct, but path is not correct and I don’t know why!. Would you please help me?

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  • Java redirected system output to jtext area, doesnt update until calculation is finished

    - by user1806716
    I have code that redirects system output to a jtext area, but that jtextarea doesnt update until the code is finished running. How do I modify the code to make the jtextarea update in real time during runtime? private void updateTextArea(final String text) { SwingUtilities.invokeLater(new Runnable() { public void run() { consoleTextAreaInner.append(text); } }); } private void redirectSystemStreams() { OutputStream out = new OutputStream() { @Override public void write(int b) throws IOException { updateTextArea(String.valueOf((char) b)); } @Override public void write(byte[] b, int off, int len) throws IOException { updateTextArea(new String(b, off, len)); } @Override public void write(byte[] b) throws IOException { write(b, 0, b.length); } }; System.setOut(new PrintStream(out, true)); System.setErr(new PrintStream(out, true)); } The rest of the code is mainly just an actionlistener for a button: private void updateButtonActionPerformed(java.awt.event.ActionEvent evt) { // TODO add your handling code here: String shopRoot = this.shopRootDirTxtField.getText(); String updZipPath = this.updateZipTextField.getText(); this.mainUpdater = new ShopUpdater(new File(shopRoot), updZipPath); this.mainUpdater.update(); } That update() method begins the process of copying+pasting files on the file system and during that process uses system.out.println to provide an up-to-date status on where the program is currently at in reference to how many more files it has to copy.

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  • Java/Python: Integration, problem with looping updating text

    - by Jivings
    Hello! Basically I have a script in Python that grabs the text from an open window using getWindowText() and outputs it to the screen. The python loops so as the text in the window changes, it outputs the changes, so the output of the python will always be up to date with the window text. I'm trying to access this text in my Java program by executing the python script as a process and reading the text it outputs using a buffered reader. For some reason this works fine for the first block of text, but will not read any more after this, it wont read any updates to the text as the python outputs it. Can someone shed some light on this? I'm about to try and use Jython, but I'd really like to know what the problem is here... try { Runtime r = Runtime.getRuntime(); Process p = r.exec("cmd /c getText.py"); BufferedReader br = new BufferedReader( new InputStreamReader(p.getInputStream())); int line; while (true) { line = br.read(); System.out.print((char) line); } } catch (Exception e) { e.printStackTrace(); }

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  • Error compiling basic java code

    - by Michael Younani
    New to java. Practicing coding by following a book. Heres my code: class Motorcycle { //Three instance variables - make and color are strings. while a boolean refers to TRUE OR FLASE(in this case off or on) String make; String color; boolean engineState; void startEngine() { if (engineState == true) System.out.print("The engine is already on."); else { engineState = true; System.out.print("The engine is now on."); } void showAtts() { System.out.print("This motorcycle is a " + color + " " + make); if (engineState ==true) System.out.print("The engine is on."); else System.out.print("The engine is off."); } } } When I compile I get 2 errors: 1) illegal start of expression 2) ; expected I can't pin point the problem. If anyone can direct me or hint me please do.

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  • Passing mix of T and T[] to a Java varargs method

    - by rfalke
    Suppose you have a Java method void foobar(int id, String ... args) and want to pass both String arrays and Strings into the method. Like this String arr1[]={"adas", "adasda"}; String arr2[]={"adas", "adasda"}; foobar(0, "adsa", "asdas"); foobar(1, arr1); foobar(2, arr1, arr2); foobar(3, arr1, "asdas", arr2); In Python there is "*" for this. Is there some way better than such rather ugly helper method: static String[] concat(Object... args) { List<String> result = new ArrayList<String>(); for (Object arg : args) { if (arg instanceof String) { String s = (String) arg; result.add(s); } else if (arg.getClass().isArray() && arg.getClass().getComponentType().equals(String.class)) { String arr[] = (String[]) arg; for (String s : arr) { result.add(s); } } else { throw new RuntimeException(); } } return result.toArray(new String[result.size()]); } which allows foobar(4, concat(arr1, "asdas", arr2));

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  • Does implementing a Java class under an open-source library's package name constitutes a modificatio

    - by Minyu
    Greetings, I understand that this is not the best forum for getting legal advices. But I am still wondering if anybody has some experience around this topic, or can point me to relevant resources that explain it. I have tried to search it online but could not find clear answers. Assuming I am using a Java open-source library from "somecompany", specifically its entities in the "org.somecompany.somepackage". During development, I found that I need to access some of the internals of that package that are not exposed through its public interface. So I thought maybe creating my own classes under the same "org.somecompany.somepackage" name would make that easier. My question is: does this constitutes a modification of the open-source library? The fully qualified name of my classes look like "org.somecompany.somepackage.myclass". It does seem an "extension" of the original library, even though I am not modifying the original library source or binary. I am also not adding my classes to the open-source jar files. Any advice or pointer to resources will be appreciated!

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  • Using same log4j logger in standalone java application

    - by ktaylorjohn
    I have some code which is a standalone java application comprising of 30+ classes. Most of these inherit from some other base classes. Each and every class has this method to get and use a log4j logger public static Logger getLogger() { if (logger != null) return logger; try { PropertyUtil propUtil = PropertyUtil.getInstance("app-log.properties"); if (propUtil != null && propUtil.getProperties() != null) PropertyConfigurator.configure(propUtil.getProperties ()); logger = Logger.getLogger(ExtractData.class); return logger; } catch (Exception exception) { exception.printStackTrace(); } } A) My question is whether this should be refactored to some common logger which is initialized once and used across by all classes? Is that a better practice? B) If yes, how can this be done ? How can I pass the logger around ? C) This is actually being used in the code not as Logger.debug() but getLogger().debug(). What is the impact of this in terms of performance?

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  • Java / Spring MVC 3 validation of an email address

    - by Tim
    I have a Java backend with Spring MVC and I am using validation in this way on my domain object for an email address: import javax.validation.constraints.NotNull; import javax.validation.constraints.Pattern; import javax.validation.constraints.Size; ... @NotNull @Size(min = 1, max = 100) @Pattern(regexp="^([a-zA-Z0-9\\-\\.\\_]+)'+'(\\@)([a-zA-Z0-9\\-\\.]+)'+'(\\.)([a-zA-Z]{2,4})$") private String email; But all I get with these lines of code Set<ConstraintViolation<Person>> failures = validator.validate(personObject); ... Map<String, String> failureMessages = new HashMap<String, String>(); for (ConstraintViolation<Person> failure : failures) { failureMessages.put(failure.getPropertyPath().toString(), failure.getMessage()); System.out.println(failure.getPropertyPath().toString()+" - "+failure.getMessage()) } I get this on the console: email - must match "^([a-zA-Z0-9\\-\\.\\_]+)'+'(\\@)([a-zA-Z0-9\\-\\.]+)'+'(\\.)([a-zA-Z]{2,4})$" but I have as email address [email protected], so the regexp does not match. So I have two prolems: What's wrong here? And how can I define a error message on my own, because display this to the user, that is not a good thing :-) Thank you in advance for your help and Best Regards.

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  • Relating text fields to check boxes in Java

    - by Finzz
    This program requires the user to login and request a database to access. The program then gets a connection object, searches through the database storing the column names into a vector for later use. The problem comes with implementing text fields to allow the user to search for specific values within the database. I can get the check boxes and text fields to appear using a gridlayout and add them to a panel. How do I relate the text fields to their appropriate check box? I've tried adding them to a vector, but then they can't also be added to the panel as well. I've searched for a way to name the text fields as the loop cycles through the column names, but it seems impossible to do without having them declared ahead of time. This can't be done either, as it's impossible to determine the attributes that the user will request. I just need to be able to know the names of the text fields so I can test to see if the user entered information and perform the necessary logic. Let me know if you have to see the rest of the code to give an answer, but hopefully you get the general idea of what I'm trying to accomplish. Picture of UI: try { ResultSet r2 = con.getMetaData().getColumns("", "", rb.getText(), ""); colNames1 = new Vector<String>(); columns1 = new Vector<JCheckBox>(); while (r2.next()) { colNames1.add(r2.getString(4)); JCheckBox cb = new JCheckBox(r2.getString(4)); JTextField tf = new JTextField(10); columns1.add(cb); p3.add(cb); p3.add(tf); } }

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  • post increment operator java

    - by srandpersonia
    I can't make heads or tails of the following code from "java puzzlers" by joshua bloch. public class Test22{ public static void main(String args[]){ int j=0; for(int i=0;i<100;i++){ j=j++; } System.out.println(j); //prints 0 int a=0,b=0; a=b++; System.out.println(a); System.out.println(b); //prints 1 } } I can't get the part where j prints 0. According to the author, j=j++ is similar to temp=j; j=j+1; j=temp; But a=b++ makes b 1. So it should've evaluated like this, a=b b=b+1 By following the same logic, shouldn't j=j++ be evaluated as, j=j j=j+1 Where does the temp come into picture here? Any explanations would be much appreciated. << I'm breaking my head over this. ;) Thanks in advance.

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  • Sorting a very large text file in Java

    - by Alice
    Hi, I have a large text file I need to sort in Java. The format is: word [tab] frequency [new line] The algorithm for sorting is: Read some of the file, filtering for purlely alphabetic words. Once you have X number of alphabetic words, call Collections.sort and write the result to a file. Repeat until you have finished reading the file. Start reading two sorted files, comparing line by line for the word with higher frequency, and writing at the same time to a new file as to not load much into your memory Repeat until all files are merged into one large file Right now I've divided the large file into smaller ones (sorted by descending frequency) with 10,000 lines each. I know I need to somehow merge these files back together, but I'm not sure how to go about this. I've created a LinkedList to keep track of all the files created. The algorithm says to compare each line in the two files, except I've tried a case where , say file1 = 8,6,5,3,1 and file2 = 9,8,8,8,8. Then if I compare them line by line I would get file3 = 9,8,8,6,8,5,8,3,8,1 which is incorrectly sorted (they should be in decreasing order). I think I'm misunderstanding some part of the algorithm. If someone could point out what I should do instead, I'd greatly appreciate it. Thanks. edit: Yes this is an assignment. We aren't allowed to increase memory unfortunately :(

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