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  • [Java] Implement a RSA algorithm

    - by Robin Monjo
    Hello everyone. I want to implement a RSA algorithm to encrypt an image (byte[]). To generate my two keys I used this piece of code : KeyPairGenerator keygen = KeyPairGenerator.getInstance("RSA"); keygen.initialize(512); keyPair = keygen.generateKeyPair(); Once public and private key are generated, I would like to show them to the user so he can distribute the public key and use the private key to decode. How can I get back those key ? Using keygen.getPrivateKey() and keygen.getPublicKey() give me all the information of the RSA algorithm, not only the keys I need. Thanks

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  • Java program has errors, 80 lines of code

    - by user2961687
    I have a problem with a program. It contains a lot of errors in Eclipse. Sorry for my english and thank you in advance. Here is the task: I. Declare a class that contains private fields Jam: String taste, double weight Create constructors containing variables as parameters: (String taste, double weight), (double weight), (String taste). Parameters constructors should initialize class fields. In case the constructor does not provide the necessary parameter, it must be assumed that the field taste must have the value "No Name" and weight - 100.0. Introduce the use of all constructors creating objects that represent three kinds of jams. Note: it must be assumed that the only constructor with two parameters can be assigned to fields of the class. Declare a class Jar that contains the field Jam jam, a dedicated constructor initiating all declared fields and methods: open close isItOpen Next, create an object of class Jar and fill it with the selected type of jam, operations repeat for all the kinds of jams. This is my code this far: public class App { public static void main(String[] args) { Jam strawberry = new Jam("strawberry", 20.45); Jam raspberry = new Jam(40.50); Jam peach = new Jam("peach"); Jar jar_1 = new Jar(); Jar jar_2 = new Jar(); Jar jar_3 = new Jar(); jar_1.open(); jar_1.fillIn(strawberry); jar_2.fillIn(peach); jar_3.fillIn(raspberry); } } class Jam { String taste; double weight; public Jam(String taste, double weight) { this.taste = taste; this.weight = weight; } public Jam(double weight) { this.taste = "No name"; this.weight = weight; } public Jam(String taste) { this.taste = taste; this.weight = 100.0; } } class Jar { public Jam Jam = new Jam(); private String state_jar; public Jar() { Jam.weight = 0; Jam.taste = ""; state_jar = "closed"; } public static String open() { state_jar = open; return state_jar; } public static String close() { state_jar = "closed"; return state_jar; } public static boolean isItOpen() { return state_jar; } public void fillIn(Jam jam) { if (isItOpen == false) open(); this.Jam.weight = jam.weight; this.Jam.taste = jam.taste; this.Jam.close(); } }

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  • Implement dictionary using java

    - by ahmad
    Task Dictionary ADT The dictionary ADT models a searchable collection of key-element entries Multiple items with the same key are allowed Applications: word-definition pairs Dictionary ADT methods: find(k): if the dictionary has an entry with key k, returns it, else, returns null findAll(k): returns an iterator of all entries with key k insert(k, o): inserts and returns the entry (k, o) remove(e): remove the entry e from the dictionary size(), isEmpty() Operation Output Dictionary insert(5,A) (5,A) (5,A) insert(7,B) (7,B) (5,A),(7,B) insert(2,C) (2,C) (5,A),(7,B),(2,C) insert(8,D) (8,D) (5,A),(7,B),(2,C),(8,D) insert(2,E) (2,E) (5,A),(7,B),(2,C),(8,D),(2,E) find(7) (7,B) (5,A),(7,B),(2,C),(8,D),(2,E) find(4) null (5,A),(7,B),(2,C),(8,D),(2,E) find(2) (2,C) (5,A),(7,B),(2,C),(8,D),(2,E) findAll(2) (2,C),(2,E) (5,A),(7,B),(2,C),(8,D),(2,E) size() 5 (5,A),(7,B),(2,C),(8,D),(2,E) remove(find(5)) (5,A) (7,B),(2,C),(8,D),(2,E) find(5) null (7,B),(2,C),(8,D),(2,E) Detailed explanation: NO Specific requirements: please Get it done i need HELP !!!

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  • java: how to convert a file to utf8

    - by Enrique San Martín
    Hi, i have a file that have some non-utf8 caracters (like "ISO-8859-1"), and so i want to convert that file (or read) to UTF8 encoding, how i can do it? The code it's like this: File file = new File("some_file_with_non_utf8_characters.txt"); /* some code to convert the file to an utf8 file */ ... edit: Put an encoding example

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  • Deleting from arraylist and exporting back to .buab file(Java)

    - by Dave
    Ive made an address book. I can currently write to the arraylist and save it back to the .buab file, but I cant delete from the arraylist and export it back to the .buab file? Im pretty much stuck on this. Im able to retrive contacts from the .buab and scroll through them using the JTextFields and buttons ive created. Any help will be dearly appreciated. Ive set up seprate classes for all operations (newcontacts, nextcontact etc). If you need the code posted let me know.. Cheers Dave

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  • Mix of Arabic and English causes problems in JTextArea (Java)

    - by Dan
    I have a JTextArea which displays HTML of an Arabic web page. So it's essentially a mix of English and Arabic. In the JTextArea, with columns set to 30, certain text just disappears instead of wrapping properly. The weird thing is that if I copy the invisible text and paste it into Notepad, then I can see it in Notepad. If I change the number of columns to 40, everything displays fine. Any ideas?

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  • DWR and other possible tools for build java application level Ajax framework

    - by Fazal
    I would assume that this question would have been asked in different ways already, but I could not find one so posting it. Sorry if its a repetition The basic idea which I am trying to explore is to design a common Ajax framework/API for our application. The main requirement is to have a common framework in the product which every module in the application can call whenever it needs to provide Ajax behavior. We basically have a page based application and not everything would be Ajax for sure. Mostly it will be smaller pieces of work which Ajax will handle. We have used GWT and it works great. But we have some constraints because of which certain areas in the application need to build standard jsp and html pages only I know little bit about dwr and it looks very promising (as even answered by some people). I wanted to know what are the other possible frameworks like dwr which I can evaluate too, before making the decision

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  • how to generate a random String? in java

    - by chandra wibowo
    hi everyone, i have an object called Student, and it has studentName, studentId, studentAddress, etc. for the studentId, i have to generate random string consist of seven numeric charaters, eg. studentId = getRandomId(); studentId = "1234567" <-- from the random generator. and i have to make sure that there is no duplicate id. thanks in advance

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  • Java generics: Illegal forward reference

    - by Arian
    Given a generic interface interface Foo<A, B> { } I want to write an implementation that requires A to be a subclass of B. So I want to do class Bar<A, B super A> implements Foo<A, B> { } // --> Syntax error or class Bar<A extends B, B> implements Foo<A, B> { } // --> illegal forward reference But the only solution that seems to work is this: class Bar<B, A extends B> implements Foo<A, B> { } which is kind of ugly, because it reverses the order of the generic parameters. Are there any solutions or workarounds to this problem?

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  • Extracting Mail from Microsoft Exchange server 2007 through IMAPS in java

    - by abhishekgem84
    props.put("mail.debug", "true"); props.setProperty("mail.store.protocol","imaps"); props.setProperty("mail.imaps.auth.plain.disable","false"); props.setProperty("mail.imaps.host","Mail3.connect.com"); props.setProperty("mail.imaps.port","135"); props.setProperty("mail.imaps.user","test"); props.setProperty("mail.imaps.pwd","123"); props.setProperty("mail.imaps.ssl.protocols","SSL"); props.setProperty("mail.imaps.socketFactory.class", "javax.net.ssl.SSLSocketFactory"); props.setProperty("mail.imaps.socketFactory.fallback", "false"); props.setProperty("mail.imaps.socketFactory.port", "135"); i have done all this but it still says javax.mail.AuthenticationFailedException: failed to connect, no password specified? kindly help me out thanks

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  • Java - FontMetrics without Graphics

    - by subSeven
    Hello! How to get FontMetrics without use Graphics ? I want to get FontMetrics in constructor, now I do this way: BufferedImage bi = new BufferedImage(5, 5, BufferedImage.TYPE_INT_RGB); FontMetrics fm = bi.getGraphics().getFontMetrics(font); int width = fm.stringWidth(pattern); int height = fm.getHeight();

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  • How to combine array list string in java ?

    - by tiendv
    I have some arraylist string with keyword inside like that ! A windows is arraylist string with keyword is bold Struct of window : 9 words before + keyword + 9 words after You can see some window overlaping How to i combine that arraylist to receive like that : Thanks

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  • Building a control-flow graph from an AST with a visitor pattern using Java

    - by omegatai
    Hi guys, I'm trying to figure out how to implement my LEParserCfgVisitor class as to build a control-flow graph from an Abstract-Syntax-Tree already generated with JavaCC. I know there are tools that already exist, but I'm trying to do it in preparation for my Compilers final. I know I need to have a data structure that keeps the graph in memory, and I want to be able to keep attributes like IN, OUT, GEN, KILL in each node as to be able to do a control-flow analysis later on. My main problem is that I haven't figured out how to connect the different blocks together, as to have the right edge between each blocks depending on their nature: branch, loops, etc. In other words, I haven't found an explicit algorithm that could help me build my visitor. Here is my empty Visitor. You can see it works on basic langage expressions, like if, while and basic operations (+,-,x,^,...) public class LEParserCfgVisitor implements LEParserVisitor { public Object visit(SimpleNode node, Object data) { return data; } public Object visit(ASTProgram node, Object data) { data = node.childrenAccept(this, data); return data; } public Object visit(ASTBlock node, Object data) { } public Object visit(ASTStmt node, Object data) { } public Object visit(ASTAssignStmt node, Object data) { } public Object visit(ASTIOStmt node, Object data) { } public Object visit(ASTIfStmt node, Object data) { } public Object visit(ASTWhileStmt node, Object data) { } public Object visit(ASTExpr node, Object data) { } public Object visit(ASTAddExpr node, Object data) { } public Object visit(ASTFactExpr node, Object data) { } public Object visit(ASTMultExpr node, Object data) { } public Object visit(ASTPowerExpr node, Object data) { } public Object visit(ASTUnaryExpr node, Object data) { } public Object visit(ASTBasicExpr node, Object data) { } public Object visit(ASTFctExpr node, Object data) { } public Object visit(ASTRealValue node, Object data) { } public Object visit(ASTIntValue node, Object data) { } public Object visit(ASTIdentifier node, Object data) { } } Can anyone give me a hand? Thanks!

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  • Quickest way to write to file in java

    - by user1097772
    I'm writing an application which compares directory structure. First I wrote an application which writes gets info about files - one line about each file or directory. My soulution is: calling method toFile Static PrintWriter pw = new PrintWriter(new BufferedWriter( new FileWriter("DirStructure.dlis")), true); String line; // info about file or directory public void toFile(String line) { pw.println(line); } and of course pw.close(), at the end. My question is, can I do it quicker? What is the quickest way? Edit: quickest way = quickest writing in the file

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  • Implementing java FixedTreadPool status listener

    - by InsertNickHere
    Hi there, it's about an application which is supposed to process (VAD, Loudness, Clipping) a lot of soundfiles (e.g. 100k). At this time, I create as many worker threads (callables) as I can put into memory, and then run all with a threadPool.invokeAll(), write results to file system, unload processed files and continue at step 1. Due to the fact it's an app with a GUI, i don't want to user to feel like the app "is not responding" while processing all soundfiles. (which it does at this time cause invokeAll is blocking). Im not sure what is a "good" way to fix this. It shall not be possible for the user to do other things while processing, but I'd like to show a progress bar like "10 of 100000 soundfiles are done". So how do I get there? Do I have to create a "watcher thread", so that every worker hold a callback on it? I'm quite new to multi threading, and don't get the idea of such a mechanisem.. If you need to know: I'm using SWT/JFace. Regards, InsertNickHere

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  • java Database framework comparison

    - by user293655
    Hi, I want to create an application that synchronize a database to multiple databases(various type of databases). I'm looking for a framework that suitable to do this. I was looking for something just get the Object of the data (like a resultset) then copy that object to the destination database. Or comparing between 2 data. Any ideas? Thanks,

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  • "Dynamic" java validation framework?

    - by pihentagy
    AFAIK JSR-303 is the standard bean validation system. I don't know whether it could do validations like this (I guess no): if an object has a deleted flag set, you cannot modify the object you cannot change the start date property, after the date is passed you cannot decrease some integer properties in the bean So how can I handle validations, which depend on the previous state of an object? I would like to solve problems like that in hibernate3.5 - spring3 - JPA2 environment. Thanks My solution was to mess with hibernate, reload the object to see the old state (after evicting the new object). This time I need some smarter solution...

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  • Should I catch exceptions thrown when closing java.sql.Connection

    - by jb
    Connection.close() may throw SqlException, but I have always assumed that it is safe to ignore any such exceptions (and I have never seen code that does not ignore them). Normally I would write: try{ connection.close(); }catch(Exception e) {} Or try{ connection.close(); }catch(Exception e) { logger.log(e.getMessage(), e); } The question is: Is it bad practice (and has anyone had problems when ignoring such exeptions). When Connection.close() does throw any exception. If it is bad how should I handle the exception. Comment: I know that discarding exceptions is evil, but I'm reffering only to exceptions thrown when closing a connection (and as I've seen this is fairly common in this case). Does anyone know when Connection.close() may throw anything?

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  • Java Enum List from Class

    - by DD
    How do I go from a Class object to a list of enums generically? i.e. public static <T extends Enum> List<T> getList(Class<T> clazz) I cant find a way to get to the values() method

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  • Java Conversion of byte[] into a srting and then back to a byte[]

    - by Sid
    I am working on a proxy server. I am getting data in byte[] which i convert into a string to perform certain operations. Now when i convert this new string back into a byte [] it causes unkonw problems. So mainly its like i need to know how to correctly convert a byte[] into a string and then back into a byte[] again. I tried to just convert the byte[] to string and then back to byte[] again (to make sure thats its not my operations that are causing problems). So its like: // where reply is a byte[] String str= new String(reply,0, bytesRead); streamToClient.write(str.getBytes(), 0, bytesRead); is not equivalent to streamToClient.write(reply, 0, bytesRead); my proxy works fine when i just send the byte[] without any conversion but when i convert it from byte[] to a string and then back to a byte[] its causes problems. can some one please help? =]

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  • How to track value of a variable in Eclipse Java Debugger

    - by aveschini
    I would like to track the value of a boolean (not Boolean) variable in the Eclips debugger. I need to know when it does change and, for this, i need to track it's value through all the execution; not only when it is in scope. More particularly i have a class (let's call it myClass) with a boolean member variable called isAvailable. My program instantiate 4 or 5 myClass objects. I am expecting that at the end of the execution the isAvailable value of all of my objects is set to true. Contrarily to my excpectation one of myClass objects has isAvailable set to false. I need to know which (in a lot of) methods is setting isAvailable to false.

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  • Static files in (Java) App Engine not accessible.

    - by fiXedd
    The example documentation says that you simply need to place your files in war/ (or a subdirectory) and they should be accessible from the host (as long as they aren't JSPs or in WEB-INF). For example, if you place foo.css in war/ then you should be able to access it at http://localhost:8080/foo.css. However, this isn't working for me at all. NONE of my static files are accessible. The docs on appengine-web.xml say that you can also specifically denote certain types as static. I've tried this as well and it makes no difference. Am I missing something obvious? UPDATE: Turns out one of the mappings in my web.xml was a little too aggressive. The following was the culprit: <servlet> <servlet-name>Main</servlet-name> <servlet-class>MainServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>Main</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> It seems that it was grabbing everything that wasn't grabbed be one of the other rules, which I don't understand because there was no * on the end of the url-pattern. It also seems to be directly contradictory to the documentation that says: Note: Static files, files that are served verbatim to users such as images, CSS or JavaScript, are handled separately from paths mentioned in the deployment descriptor. A request for a URL path that matches a path to a file in the WAR that's considered a static file will serve the file, regardless of servlet and filter mappings in the deployment descriptor. You can exclude files from those treated as static files using the appengine-web.xml file. So, how can I have a rule that matches the base of my domain (eg. http://www.example.com/) and still allows the static files to filter through?

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  • Java How to get exact tile location in random tile engine

    - by SYNYST3R1
    I am using the slick2d library. I want to know how to get the exact tile location so when I click on a tile it only changes that tile and not every tile on the screen. My tile generation class public Image[] tiles = new Image[3]; public int width, height; public int[][] index; public Image grass, dirt, selection; boolean selected; int mouseX, mouseY; public void init() throws SlickException { grass = new Image("assets/tiles/grass.png"); dirt = new Image("assets/tiles/dirt.png"); selection = new Image("assets/tiles/selection.png"); tiles[0] = grass; tiles[1] = dirt; width = 50; height = 50; index = new int[width][height]; Random rand = new Random(); for (int x = 0; x < width; x++) { for (int y = 0; y < height; y++) { index[x][y] = rand.nextInt(2); } } } public void update(GameContainer gc) { Input input = gc.getInput(); mouseX = input.getMouseX(); mouseY = input.getMouseY(); if(input.isMouseButtonDown(Input.MOUSE_LEFT_BUTTON)) { selected = true; } else{ selected = false; } } public void render() { for (int x = 0; x < width; x++) { for (int y = 0; y < height; y++) { tiles[index[x][y]].draw(x * 64, y *64); if(IsMouseInsideTile(x, y)) selection.draw(x * 64, y * 64); } } } public boolean IsMouseInsideTile(int x, int y) { return (mouseX >= x * 64 && mouseX <= (x + 1) * 64 && mouseY >= y * 64 && mouseY <= (y + 1) * 64); } I have tried a couple different ways to change the tile I am clicking on, but I don't understand how to do it.

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