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  • What's "@Override" there for in java?

    - by symfony
    public class Animal { public void eat() { System.out.println("I eat like a generic Animal."); } } public class Wolf extends Animal { @Override public void eat() { System.out.println("I eat like a wolf!"); } } Does @Override actually have some functionality or it's just kinda comment?

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  • Publish failed using Ant publisher (Eclipse/datanucleus).

    - by aronp
    Dear All, I am being driven mad the following (apparently hard) error from eclipse. Publish failed using Ant publisher Resource is out of sync with the file system: '/MyServlet/build/classes/com/inver/hotzones/database/BaseNetworkData.class'. I have seen comments on similar errors where refreshing eclipses view of the project helps but it is not helping me. Have tried cleaning the project, removing it from the webserver, deleting war files but cant seem to clear it. I have reset my TMPDIR variable so that it uses a directory on the same filesystem as that appeared to be another possible cause. The error occurs on classes which have been enhanced by datanuculeus. I have auto-enhance on the project. The other references to this problem indicate that it is due to Eclipses view of the project being out of step with the filesystem, and I am guessing that this has something to do with thedata nucleus enhancement. Any ideas? Thanks. I am using Eclipse 3.5.2 with latest datanucleus pluggins. Stack trace org.eclipse.core.runtime.CoreException: Resource is out of sync with the file system: '/MyServlet/build/classes/com/inver/hotzones/database/BaseNetworkData.class'. at org.eclipse.jst.server.generic.core.internal.publishers.AbstractModuleAssembler.copyModule(AbstractModuleAssembler.java:172) at org.eclipse.jst.server.generic.core.internal.publishers.WarModuleAssembler.assemble(WarModuleAssembler.java:31) at org.eclipse.jst.server.generic.core.internal.publishers.AntPublisher.assembleModule(AntPublisher.java:167) at org.eclipse.jst.server.generic.core.internal.publishers.AntPublisher.publish(AntPublisher.java:128) at org.eclipse.jst.server.generic.core.internal.GenericServerBehaviour.publishModule(GenericServerBehaviour.java:82) at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.publishModule(ServerBehaviourDelegate.java:949) at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.publishModules(ServerBehaviourDelegate.java:1039) at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.publish(ServerBehaviourDelegate.java:872) at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.publish(ServerBehaviourDelegate.java:708) at org.eclipse.wst.server.core.internal.Server.publishImpl(Server.java:2731) at org.eclipse.wst.server.core.internal.Server$PublishJob.run(Server.java:278) at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

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  • Java-Instance Method Call

    - by Gogi
    When I call as instance method of a class as follows : object_name.function_name(); how the compiler knows that the "function_name" has to be called for that "object_name" behind the scenes ?

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  • Reading XML in Java Applet

    - by Midday
    I know: I have to sign the applet so it can read files How to parse XML files My Questions would be: Should I keep the XML file in the .jar or separate? Are there some best practices tutorials? if so please link me

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  • How to simulate an unhandled exception in Java

    - by Martin Wiboe
    Hi, I am creating some multi-threaded code, and I have created a JobDispatcher class that creates threads. I want this object to handle any unhandled exceptions in the worker threads, and so I am using Thread.setUncaughtExceptionHandler(this); Now, I would like to test this functionality - how can I generate an unhandled exception in the run() method of my worker object? Thanks, Martin

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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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  • Java: Get Mainform object from JInternalFrame

    - by rodion
    Can I do this without reference to the object in the constructor? In other words, any class inherited from FrmTaoChild when creating must to add the button on the toolbar of the main window public class FrmTaoMain extends JFrame { JToolBar tbTask = new JToolBar(); public FrmTaoMain(String Caption) { super(Caption); ... FrmTaoChild FrmChild = new FrmTaoChild(tbTask,"test"); } } public class FrmTaoChild extends JInternalFrame { public FrmTaoChild(JToolBar tbTask, String Caption) { super (Caption); JButton btnTask = new JButton(Caption); tbTask.add(btnTask); } }

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  • Algorithm to detect how many words typed, also multi sentence support (Java)

    - by Alex Cheng
    Hello all. Problem: I have to design an algorithm, which does the following for me: Say that I have a line (e.g.) alert tcp 192.168.1.1 (caret is currently here) The algorithm should process this line, and return a value of 4. I coded something for it, I know it's sloppy, but it works, partly. private int counter = 0; public void determineRuleActionRegion(String str, int index) { if (str.length() == 0 || str.indexOf(" ") == -1) { triggerSuggestionList(1); return; } //remove duplicate space, spaces in front and back before searching int num = str.trim().replaceAll(" +", " ").indexOf(" ", index); //Check for occurances of spaces, recursively if (num == -1) { //if there is no space //no need to check if it's 0 times it will assign to 1 triggerSuggestionList(counter + 1); counter = 0; return; //set to rule action } else { //there is a space counter++; determineRuleActionRegion(str, num + 1); } } //end of determineactionRegion() So basically I find for the space and determine the region (number of words typed). However, I want it to change upon the user pressing space bar <space character>. How may I go around with the current code? Or better yet, how would one suggest me to do it the correct way? I'm figuring out on BreakIterator for this case... To add to that, I believe my algorithm won't work for multi sentences. How should I address this problem as well. -- The source of String str is acquired from textPane.getText(0, pos + 1);, the JTextPane. Thanks in advance. Do let me know if my question is still not specific enough.

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  • Java assert nasty side-effect - compiler bug?

    - by Alex
    This public class test { public static void main(String[] args) { Object o = null; assert o != null; if(o != null) System.out.println("o != null"); } } prints out "o != null"; both 1.5_22 and 1.6_18. Compiler bug? Commenting out the assert fixes it. The byte code appears to jump directly to the print statement when assertions are disabled: public static main(String[]) : void L0 LINENUMBER 5 L0 ACONST_NULL ASTORE 1 L1 LINENUMBER 6 L1 GETSTATIC test.$assertionsDisabled : boolean IFNE L2 ALOAD 1: o IFNONNULL L2 NEW AssertionError DUP INVOKESPECIAL AssertionError.<init>() : void ATHROW L2 LINENUMBER 8 L2 GETSTATIC System.out : PrintStream LDC "o != null" INVOKEVIRTUAL PrintStream.println(String) : void L3 LINENUMBER 9 L3 RETURN L4

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  • Regular Expression in java

    - by Sunil
    I have a HTML page and I want to fetch the result between two tags <b> and <BR> <b>Defendants Name:</b>Donahue, Leah A <BR> What is the regular expression to fetch the words between these two tags

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  • java regular expression

    - by changed
    Hi I have to create a regular expression for some path conversion. Example for path are //name:value /name:value // name:value /name:value /name:value /name:value//name:value thing is how to check for // or / at the start or middle of the string and how can i specify that name can contain any of this a-zA-Z and _ Path also contains white spaces. thanks-

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  • Java: versioned data structures?

    - by Jason S
    I have a data structure that is pretty simple (basically a structure containing some arrays and single values), but I need to record the history of the data structure so that I can efficiently get the contents of the data structure at any point in time. Is there a relatively straightforward way to do this? The best way I can think of would be to encapsulate the whole data structure with something that handles all the mutating operations by storing data in functional data structures, and then for each mutation operation caching a copy of the data structure in a Map indexed by time-ordering (e.g. a TreeMap with real time as keys, or a HashMap with a counter of mutation operations combined with one or more indexes stored in TreeMaps mapping real time / tick count / etc. to mutation operations) any suggestions?

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  • Mixed alignment with Java Swing's GroupLayout

    - by zigdon
    I'm trying to build a GUI window in my application. What I'm trying to do is have a window, with a few buttons at the top, and a large text area. Something like this: +--------------------------------------------------+ | [button1] [button2] [button3] | | +----------------------------------------------+ | | | text area | | | | | | | | | | | | | | | +----------------------------------------------+ | +--------------------------------------------------+ I'm almost there, using GroupLayout: layout.setHorizontalGroup( layout.createParallelGroup() .addGroup(layout.createSequentialGroup() .addComponent(button1) .addComponent(button2)) .addComponent(closeWindow)) .addComponent(textarea1) ); layout.setVerticalGroup( layout.createSequentialGroup() .addGroup(layout.createParallelGroup() .addComponent(button1) .addComponent(button2) .addComponent(button3)) .addComponent(textarea) ); The problem is that this ends up with button3 aligned to the left, with the other two. I can't seem to figure out how I can specify the alignment on just that one button. I can do GroupLayout.Alignment.TRAILING on the entire button bar, but that hits all 3 buttons, which is also not quite right. So what's the correct approach? Since the alignment only applies for Parallel Groups, I don't think having a HorizontalGroup with two Sequential Groups in it will help? What am I missing?

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  • Java + Eclipse: Synchronize stdout and stderr

    - by Martijn Courteaux
    Hi, I use Eclipse. When I have an application like this: write 20 times 'Hello World\n' to stdout write 'ERROR\n' to stderr write 5 times 'Hello World\n' to stdout The output looks many times like this: Hello World Hello World Hello World Hello World Hello World Hello World ... Hello World Hello World Hello World ERROR Is there a way to synchronize these two output streams? Of course without waiting a few milliseconds after the block of 20 times Hello World and waiting a few milliseconds after printing ERROR.

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  • Is java HashMap.clear() and remove() memory effective?

    - by Shaman
    Consider the follwing HashMap.clear() code: /** * Removes all of the mappings from this map. * The map will be empty after this call returns. */ public void clear() { modCount++; Entry[] tab = table; for (int i = 0; i < tab.length; i++) tab[i] = null; size = 0; } It seems, that the internal array (table) of Entrys is never shrinked. So, when I add 10000 elements to a map, and after that call map.clear(), it will keep 10000 nulls in it's internal array. So, my question is, how does JVM handle this array of nothing, and thus, is HashMap memory effective?

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  • StackOverflowError occured as using java.util.regex.Matcher

    - by Captain Kidd
    Hi guys I try to catch text by Regular Expression. I list codes as follows. Pattern p=Pattern.compile("<@a>(?:.|\\s)+?</@a>"); Matcher m = p.matcher(fileContents.toString()); while(m.find()) { //Error will be thrown at this point System.out.println(m.group()); } If the length of text I want to catch is too long, system will throw me a StackOverflowError. Otherwise, the codes work well. Please help me how to solve this problem.

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  • A linked list with multiple heads in Java

    - by Emile
    Hi, I have a list in which I'd like to keep several head pointers. I've tried to create multiple ListIterators on the same list but this forbid me to add new elements in my list... (see Concurrent Modification exception). I could create my own class but I'd rather use a built-in implementation ;) To be more specific, here is an inefficient implementation of two basic operations and the one wich doesn't work : class MyList <E { private int[] _heads; private List<E _l; public MyList ( int nbHeads ) { _heads = new int[nbHeads]; _l = new LinkedList<E(); } public void add ( E e ) { _l.add(e); } public E next ( int head ) { return _l.get(_heads[head++]); // ugly } } class MyList <E { private Vector<ListIterator<E _iters; private List<E _l; public MyList ( int nbHeads ) { _iters = new Vector<ListIterator<E(nbHeads); _l = new LinkedList<E(); for( ListIterator<E iter : _iters ) iter = _l.listIterator(); } public void add ( E e ) { _l.add(e); } public E next ( int head ) { // ConcurrentModificationException because of the add() return _iters.get(head).next(); } } Emile

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  • Java: repetition, overuse -- ?

    - by HH
    I try to be as minimalist as possible. Repetition is a problem. I hate it. When is it really a problem? what is static-overuse? what is field-method overuse? what is class-overuse? are there more types of overuse? Problem A: when it is too much to use of static? private static class Data { private static String fileContent; private static SizeSequence lineMap; private static File fileThing; private static char type; private static boolean binary; private static String name; private static String path; } private static class Print { //<1st LINE, LEFT_SIDE, 2nd LINE, RIGHT_SIDE> private Integer[] printPositions=new Integer[4]; private static String fingerPrint; private static String formatPrint; } Problem B: when it is too much to get field data with private methods? public Stack<Integer> getPositions(){return positions;} public Integer[] getPrintPositions(){return printPositions;} private Stack<String> getPrintViews(){return printViews;} private Stack<String> getPrintViewsPerFile(){return printViewsPerFile;} public String getPrintView(){return printView;} public String getFingerPrint(){return fingerPrint;} public String getFormatPrint(){return formatPrint;} public String getFileContent(){return fileContent;} public SizeSequence getLineMap(){return lineMap;} public File getFile(){return fileThing;} public boolean getBinary(){return binary;} public char getType(){return type;} public String getPath(){return path;} public FileObject getData(){return fObj;} public String getSearchTerm(){return searchTerm;} Related interface overuse

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  • static block instance block java Order

    - by Rollerball
    Having read this question In what order are the different parts of a class initialized when a class is loaded in the JVM? and the related JLS. I would like to know in more detail why for example having class Animal (superclass) and class Dog (subclass) as following: class Animal { static{ System.out.println("This is Animal's static block speaking"): } { System.out.println("This is Animal's instance block speaking"); } class Dog{ static{ System.out.println("This is Dog's static block speaking"); } { System.out.println("This is Dog's instance block speaking"); } public static void main (String [] args) { Dog dog = new Dog(); } } Ok before instantiating a class its direct superclass needs to be initialized (therefore all the statics variables and block need to be executed). So basically the question is: Why after initializing the static variables and static blocks of the super class, control goes down to the subclass for static variables initialization rather then finishing off the initialization of also the instance member? The control goes like: superclass (Animal): static variables and static blocks subclass (Dog): static variables and static blocks superclass (Animal): instance variables and instance blocks sublcass (Dog):instance variables and instance blocks What is the reason why it is in this way rather than : superclass -> static members superclass -> instance members subclass -> static members sublcass-> instance members

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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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  • Cloning java ArrayList and preventing it from modifications

    - by user222164
    I have a data structure like a database Rowset, which has got Rows and Rows have Columns. I need to initialize a Columns with null values, current code is to loop thru each column for a row and initialize values to NULL. Which is very inefficient if you have 100s or rows and 10s of column. So instead I am keeping a initialized ArrayList of columns are RowSet level, and then doing a clone of this Arraylist for individual rows, as I believe clone() is faster than looping thru each element. row.columnsValues = rowsset.NullArrayList.clone() Problem with this is NullArrayList can be accidentally modified after being cloned, thus sacrificing the integrity of ArrayList at RowSet level, to prevent I am doing 3 things 1) Delcaring ArrayList as final 2) Any elements I insert are final or null 3) Methods thurough this arrayList are passed to other arrays are declared a final. Sounds like a plan, do you see any holes ?

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  • getting base64 content string of an image from a mimepart in Java

    - by Bas van den Broek
    Hello, I am trying to get the base64 content of a MimePart in a MimeMultiPart, but I'm struggling with the Javamail package. I simply want the base64 encoded String of a certain inline image, there doesn't seem to be an easy way to do this though. I wrote a method that will take the mime content (as a string) and an image name as a parameter, and searches for the part that contains the base64 content of that image name, and in the end returns this base64 string (as well as the content type but that is irrelevant for this question) Here is the relevant code: private static String[] getBase64Content(String imageName, String mimeString) throws MessagingException, IOException { System.out.println("image name: " + imageName + "\n\n"); System.out.println("mime string: " + mimeString); String[] base64Content = new String[2]; base64Content[0] = ""; base64Content[1] = "image/jpeg"; //some default value DataSource source = new ByteArrayDataSource(new ByteArrayInputStream(mimeString.getBytes()), "multipart/mixed"); MimeMultipart mp = new MimeMultipart(source); for (int i = 0; i < mp.getCount(); i++) { MimePart part = (MimePart) mp.getBodyPart(i); String disposition = part.getDisposition(); if (disposition != null && disposition.equals(Part.INLINE)) { if (part.getContentID() != null && part.getContentID().indexOf(imageName) > -1) //check if this is the right part { if (part.getContent() instanceof BASE64DecoderStream) { BASE64DecoderStream base64DecoderStream = (BASE64DecoderStream) part.getContent(); StringWriter writer = new StringWriter(); IOUtils.copy(base64DecoderStream, writer); String base64decodedString = writer.toString(); byte[] encodedMimeByteArray = Base64.encodeBase64(base64decodedString.getBytes()); String encodedMimeString = new String(encodedMimeByteArray); System.out.println("encoded mime string: " + encodedMimeString); base64Content[0] = encodedMimeString; base64Content[1] = getContentTypeString(part); } } } } return base64Content; } I cannot paste all of the output as the post would be too long, but this is some of it: image name: [email protected] This is a part of the mimeString input, it does find this (correct) part with the image name: --_004_225726A14AF9134CB538EE7BD44373A04D9E3F3940menexch2007ex_ Content-Type: image/gif; name="image001.gif" Content-Description: image001.gif Content-Disposition: inline; filename="image001.gif"; size=1070; creation-date="Fri, 02 Apr 2010 16:19:43 GMT"; modification-date="Fri, 02 Apr 2010 16:19:43 GMT" Content-ID: <[email protected]> Content-Transfer-Encoding: base64 R0lGODlhEAAQAPcAABxuHJzSlDymHGy2XHTKbITCdNTu1FyqTHTCXJTKhLTarCSKHEy2JHy6bJza lITKfFzCPEyWPHS+XHzCbJzSjFS+NLTirBx6HHzKdOz27GzCZJTOjCyWHKzWpHy2ZJTGhHS+VLzi (more base64 string here that I'm not going to paste) But when it finally prints the encoded mime string, this is a different string than I was expecting: encoded mime string: R0lGODlhEAAQAO+/vQAAHG4c77+90pQ877+9HGzvv71cdO+/vWzvv73vv71077+977+977+9XO+/vUx077+9XO+/vcqE77+92qwk77+9HEzvv70kfO+/vWzvv73alO+ Clearly different from the one that has its output in the part above. I'm not even sure what I'm looking at here, but when I try to load this as an image in a html page, it won't work. This is fairly frustrating for me, since all I want is a piece of the text that I'm already printing, but I'd rather not have to search through the mime string myself for the correct part, introducing all kinds of bugs.So I'd really prefer to use the Javamail library but could use some help on how to actually get that correct mime string.

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