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  • non blocking client server chat application in java using nio

    - by Amith
    I built a simple chat application using nio channels. I am very much new to networking as well as threads. This application is for communicating with server (Server / Client chat application). My problem is that multiple clients are not supported by the server. How do I solve this problem? What's the bug in my code? public class Clientcore extends Thread { SelectionKey selkey=null; Selector sckt_manager=null; public void coreClient() { System.out.println("please enter the text"); BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in)); SocketChannel sc = null; try { sc = SocketChannel.open(); sc.configureBlocking(false); sc.connect(new InetSocketAddress(8888)); int i=0; while (!sc.finishConnect()) { } for(int ii=0;ii>-22;ii++) { System.out.println("Enter the text"); String HELLO_REQUEST =stdin.readLine().toString(); if(HELLO_REQUEST.equalsIgnoreCase("end")) { break; } System.out.println("Sending a request to HelloServer"); ByteBuffer buffer = ByteBuffer.wrap(HELLO_REQUEST.getBytes()); sc.write(buffer); } } catch (IOException e) { e.printStackTrace(); } finally { if (sc != null) { try { sc.close(); } catch (Exception e) { e.printStackTrace(); } } } } public void run() { try { coreClient(); } catch(Exception ej) { ej.printStackTrace(); }}} public class ServerCore extends Thread { SelectionKey selkey=null; Selector sckt_manager=null; public void run() { try { coreServer(); } catch(Exception ej) { ej.printStackTrace(); } } private void coreServer() { try { ServerSocketChannel ssc = ServerSocketChannel.open(); try { ssc.socket().bind(new InetSocketAddress(8888)); while (true) { sckt_manager=SelectorProvider.provider().openSelector(); ssc.configureBlocking(false); SocketChannel sc = ssc.accept(); register_server(ssc,SelectionKey.OP_ACCEPT); if (sc == null) { } else { System.out.println("Received an incoming connection from " + sc.socket().getRemoteSocketAddress()); printRequest(sc); System.err.println("testing 1"); String HELLO_REPLY = "Sample Display"; ByteBuffer buffer = ByteBuffer.wrap(HELLO_REPLY.getBytes()); System.err.println("testing 2"); sc.write(buffer); System.err.println("testing 3"); sc.close(); }}} catch (IOException e) { e.printStackTrace(); } finally { if (ssc != null) { try { ssc.close(); } catch (IOException e) { e.printStackTrace(); } } } } catch(Exception E) { System.out.println("Ex in servCORE "+E); } } private static void printRequest(SocketChannel sc) throws IOException { ReadableByteChannel rbc = Channels.newChannel(sc.socket().getInputStream()); WritableByteChannel wbc = Channels.newChannel(System.out); ByteBuffer b = ByteBuffer.allocate(1024); // read 1024 bytes while (rbc.read(b) != -1) { b.flip(); while (b.hasRemaining()) { wbc.write(b); System.out.println(); } b.clear(); } } public void register_server(ServerSocketChannel ssc,int selectionkey_ops)throws Exception { ssc.register(sckt_manager,selectionkey_ops); }} public class HelloClient { public void coreClientChat() { Clientcore t=new Clientcore(); new Thread(t).start(); } public static void main(String[] args)throws Exception { HelloClient cl= new HelloClient(); cl.coreClientChat(); }} public class HelloServer { public void coreServerChat() { ServerCore t=new ServerCore(); new Thread(t).start(); } public static void main(String[] args) { HelloServer st= new HelloServer(); st.coreServerChat(); }}

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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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  • Reformatting a Java String

    - by Travis
    I have a string that looks like this: CALDARI_STARSHIP_ENGINEERING and I need to edit it to look like Caldari Starship Engineering Unfortunately it's three in the morning and I cannot for the life of me figure this out. I've always had trouble with replacing stuff in strings so any help would be awesome and would help me understand how to do this in the future.

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  • Import text file crunching library for Java/Groovy ?

    - by devdude
    In a lot of real life implementations of applications we face the requirement to import some kind of (text) files. Usually we would implement some (hardcoded?) logic to validate the file (eg. proper header, proper number of delimiters, proper date/time value,etc.). Eventually also need to check for the existence of related data in a table (eg. value of field 1 in text file must have an entry in some basic data table). While XML solves this (to some extend) with XSD and DTD, we end up hacking this again and again for proprietary text file formats. Is there any library or framework that allows the creation of templates similar to the xsd approach ? This would make it way more flexible to react on file format changes or implement new formats. Thanks for any hints Sven

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  • Java HTTP Request Occasionally Hangs

    - by behrk2
    Hello Everyone, For the majority of the time, my HTTP Requests work with no problem. However, occasionally they will hang. The code that I am using is set up so that if the request succeeds (with a response code of 200 or 201), then call screen.requestSucceeded(). If the request fails, then call screen.requestFailed(). When the request hangs, however, it does so before one of the above methods are called. Is there something wrong with my code? Should I be using some sort of best practice to prevent any hanging? The following is my code. I would appreciate any help. Thanks! HttpConnection connection = (HttpConnection) Connector.open(url + connectionParameters); connection.setRequestMethod(method); connection.setRequestProperty("WWW-Authenticate", "OAuth realm=api.netflix.com"); if (method.equals("POST")) { connection.setRequestProperty("Content-type", "application/x-www-form-urlencoded"); } int responseCode = connection.getResponseCode(); System.out.println("RESPONSE CODE: " + responseCode); if (connection instanceof HttpsConnection) { HttpsConnection secureConnection = (HttpsConnection) connection; String issuer = secureConnection.getSecurityInfo() .getServerCertificate().getIssuer(); UiApplication.getUiApplication().invokeLater( new DialogRunner( "Secure Connection! Certificate issued by: " + issuer)); } if (responseCode != 200 && responseCode != 201) { screen.requestFailed("Unexpected response code: " + responseCode); connection.close(); return; } String contentType = connection.getHeaderField("Content-type"); ByteArrayOutputStream baos = new ByteArrayOutputStream(); InputStream responseData = connection.openInputStream(); byte[] buffer = new byte[20000]; int bytesRead = 0; while ((bytesRead = responseData.read(buffer)) > 0) { baos.write(buffer, 0, bytesRead); } baos.close(); connection.close(); screen.requestSucceeded(baos.toByteArray(), contentType); } catch (IOException ex) { screen.requestFailed(ex.toString()); }

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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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  • goto statements in java

    - by user238284
    I executed the below code in Eclipse, but the GOTO statements in it is not effective. How to use it? case 2: **outsideloops:** System.out.println("Enter the marks (in 100):"); System.out.println("Subject 1:"); float sub1=Float.parseFloat(br.readLine()); **if(sub1<=101) goto outsideloops;** System.out.println("Subject 2:"); float sub2=Float.parseFloat(br.readLine()); System.out.println("Subject 3:"); float sub3=Float.parseFloat(br.readLine()); System.out.println("The Student is "+stu.average(sub1,sub2,sub3)+ "in the examinations"); break;

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  • Java: Combine 2 List <String[]>

    - by battousai622
    I have two List of array string. I want to be able to create a New List (newList) by combining the 2 lists. But it must meet these 3 conditions: 1) Copy the contents of store_inventory into newList. 2) Then if the item names in store_inventory & new_acquisitions match, just add the two quantities together and change it in newList. 3) If new_acquisitions has a new item that does not exist in store_inventory, then add it to the newList. The titles for the CSV list are: Item Name, Quantity, Cost, Price. The List contains an string[] of item name, quantity, cost and price for each row. CSVReader from = new CSVReader(new FileReader("/test/new_acquisitions.csv")); List <String[]> acquisitions = from.readAll(); CSVReader to = new CSVReader(new FileReader("/test/store_inventory.csv")); List <String[]> inventory = to.readAll(); List <String[]> newList; Any code to get me started would be great! =] this is what i have so far... for (int i = 0; i < acquisitions.size(); i++) { temp1 = acquisitions.get(i); for (int j = 1; j < inventory.size(); j++) { temp2 = inventory.get(j); if (temp1[0].equals(temp2[0])) { //if match found... do something? //break out of loop } } //if new item found... do something? }

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  • Java multi Generic collection parameters complie error

    - by Geln Yang
    Hi, So strange!Please have a look the code first: public class A { } public class B extends A { } public class C extends A { } public class TestMain { public <T extends A> void test(T a, T b) { } public <T extends A> void test(List<T> a, List<T> b) { } public static void main(String[] args) { new TestMain().test(new B(), new C()); new TestMain().test(new ArrayList<B>(), new ArrayList<C>()); } } The statement "new TestMain().test(new ArrayList(), new ArrayList())" get a "Bound mismatch" compile error, while "new TestMain().test(new B(), new C())" is compiled ok. Bound mismatch: The generic method test(T, T) of type TestMain is not applicable for the arguments (ArrayList, ArrayList). The inferred type ArrayList is not a valid substitute for the bounded parameter It seems the type of the second generic List parameter is limited by the Type of the first.Is it a feature or a bug of the compile program? ps, jdk:1.6,IDE:Eclipse 3.5.1

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  • FTPing a file to Mainframe using Java, Apache Common Net

    - by SKR
    I'm am trying to upload a file into mainframe server using FTP. My code is below FTPClient client = new FTPClient(); InputStream in = null; FileInputStream fis = null; try{ client.connect("10.10.23.23"); client.login("user1", "pass123"); client.setFileType(FTPClient.BINARY_FILE_TYPE); int reply ; reply = client.getReplyCode(); System.out.println("Reply Code:"+reply); if(FTPReply.isPositiveCompletion(reply)){ System.out.println("Positive reply"); String filename ="D:\\FILE.txt"; in = new FileInputStream(filename); client.storeFile("FILE.TXT", in); client.logout(); fis.close(); }else{ System.out.println("Negative reply"); } }catch(final Throwable t){ t.printStackTrace(); } The code gets struck in client.storeFile("FILE.TXT", in); I am unable to debug. Please suggest ways / solutions.

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  • JAVA - Download PDF file from Webserver

    - by Augusto Picciani
    I need to download a pdf file from a webserver to my pc and save it locally. I used Httpclient to connect to webserver and get the content body: HttpEntity entity=response.getEntity(); InputStream in=entity.getContent(); String stream = CharStreams.toString(new InputStreamReader(in)); int size=stream.length(); System.out.println("stringa html page LENGTH:"+stream.length()); System.out.println(stream); SaveToFile(stream); Then i save content in a file: //check CRLF (i don't know if i need to to this) String[] fix=stream.split("\r\n"); File file=new File("C:\\Users\\augusto\\Desktop\\progetti web\\test\\test2.pdf"); PrintWriter out = new PrintWriter(new FileWriter(file)); for (int i = 0; i < fix.length; i++) { out.print(fix[i]); out.print("\n"); } out.close(); I also tried to save a String content to file directly: OutputStream out=new FileOutputStream("pathPdfFile"); out.write(stream.getBytes()); out.close(); But the result is always the same: I can open pdf file but i can see white pages only. Does the mistake is around pdf stream and endstream charset encoding? Does pdf content between stream and endStream need to be manipulate in some others way?

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  • How to replace characters in a java String?

    - by ManBugra
    I like to replace a certain set of characters of a string with a corresponding replacement character in an efficent way. For example: String sourceCharacters = "šdccŠÐCCžŽ"; String targetCharacters = "sdccSDCCzZ"; String result = replaceChars("Gracišce", sourceCharacters , targetCharacters ); Assert.equals(result,"Gracisce") == true; Is there are more efficient way than to use the replaceAll method of the String class? My first idea was: final String s = "Gracišce"; String sourceCharacters = "šdccŠÐCCžŽ"; String targetCharacters = "sdccSDCCzZ"; // preparation final char[] sourceString = s.toCharArray(); final char result[] = new char[sourceString.length]; final char[] targetCharactersArray = targetCharacters.toCharArray(); // main work for(int i=0,l=sourceString.length;i<l;++i) { final int pos = sourceCharacters.indexOf(sourceString[i]); result[i] = pos!=-1 ? targetCharactersArray[pos] : sourceString[i]; } // result String resultString = new String(result); Any ideas? Btw, the UTF-8 characters are causing the trouble, with US_ASCII it works fine.

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  • Java enums in generic type

    - by Marcin Cylke
    Hi, I'd like to create a generic enum-based mapper for IBatis. I'm doing this with the below code. This does have compile time errors, which I don't know how to fix. Maybe my solution is just plain wrong (keep in mind the use of IBatis), in such case please suggest something better. Any help appreciated. What I want to achieve is to define subsequent mappers as: public class XEnumTypeHandler extends CommonEnumTypeHandler<X> { } The current code: public class CommonEnumTypeHandler<T extends Enum> implements TypeHandlerCallback { public void setParameter(ParameterSetter ps, Object o) throws SQLException { if (o.getClass().isAssignableFrom(**T**)) { ps.setString(((**T**) o).value().toUpperCase()); } else throw new SQLException("Excpected ParameterType object than: " + o); } public Object getResult(ResultGetter rs) throws SQLException { Object o = valueOf(rs.getString()); if (o == null) throw new SQLException("Unknown parameter type: " + rs.getString()); return o; } public Object valueOf(String s) { for (T pt : T.**values()**) { if (pt.**value()**.equalsIgnoreCase(s)) return pt; } return null; } } I've added error markings to the above code, the error messages are in order: T cannot be resolved The method value() is undefined for the type T The method values() is undefined for the type T The method values() is undefined for the type T

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  • Java KeyListener in separate class

    - by Chris
    So I have my main class here, where basically creates a new jframe and adds a world object to it. The world object is basically where all drawing and keylistening would take place... public class Blobs extends JFrame{ public Blobs() { super("Blobs :) - By Chris Tanaka"); setVisible(true); setResizable(false); setSize(1000, 1000); setIgnoreRepaint(true); setDefaultCloseOperation(EXIT_ON_CLOSE); add(new World()); } public static void main(String[] args) { new Blobs(); } } How exactly would you get key input from the world class? (So far I have my world class extending a jpanel and implementing a keylistener. In the constructor i addKeyListener(this). I also have these methods since they are auto implemented: public void keyPressed(KeyEvent e) { if (e.getKeyCode() == KeyEvent.VK_W) System.out.println("Hi"); } public void keyReleased(KeyEvent e) {} public void keyTyped(KeyEvent e) {} However this does not seem to work?

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  • Second level cache for java web app and its alternatives

    - by EugeneP
    Between the transitions of the web app I use a Session object to save my objects in. I've heard there's a program called memcached but there's no compiled version of it on the site, besides some people think there are real disadvantages of it. Now I wanna ask you. What are alternatives, pros and cons of different approaches? Is memcached painpul for sysadmins to install? Is it difficult to embed it to the existing infrastructure from the perspective of a sysadmin? What about using a database to hold temporary data between web app transitions? Is it a normal practice?

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  • Pass string between two threads in java

    - by geeta
    I have to search a string in a file and write the matched lines to another file. I have a thread to read a file and a thread to write a file. I want to send the stringBuffer from read thread to write thread. Please help me to pass this. I amm getting null value passed. write thread: class OutputThread extends Thread{ /****************** Writes the line with search string to the output file *************/ Thread runner1,runner; File Out_File; public OutputThread() { } public OutputThread(Thread runner,File Out_File) { runner1 = new Thread(this,"writeThread"); // (1) Create a new thread. this.Out_File=Out_File; this.runner=runner; runner1.start(); // (2) Start the thread. } public void run() { try{ BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter(Out_File,true)); System.out.println("inside write"); synchronized(runner){ System.out.println("inside wait"); runner.wait(); } System.out.println("outside wait"); // bufferedWriter.write(line.toString()); Buffer Buf = new Buffer(); bufferedWriter.write(Buf.buffers); System.out.println(Buf.buffers); bufferedWriter.flush(); } catch(Exception e){ System.out.println(e); e.printStackTrace(); } } } Read Thraed: class FileThread extends Thread{ Thread runner; File dir; String search_string,stats; File Out_File,final_output; StringBuffer sb = new StringBuffer(); public FileThread() { } public FileThread(CountDownLatch latch,String threadName,File dir,String search_string,File Out_File,File final_output,String stats) { runner = new Thread(this, threadName); // (1) Create a new thread. this.dir=dir; this.search_string=search_string; this.Out_File=Out_File; this.stats=stats; this.final_output=final_output; this.latch=latch; runner.start(); // (2) Start the thread. } public void run() { try{ Enumeration entries; ZipFile zipFile; String source_file_name = dir.toString(); File Source_file = dir; String extension; OutputThread out = new OutputThread(runner,Out_File); int dotPos = source_file_name.lastIndexOf("."); extension = source_file_name.substring(dotPos+1); if(extension.equals("zip")) { zipFile = new ZipFile(source_file_name); entries = zipFile.entries(); while(entries.hasMoreElements()) { ZipEntry entry = (ZipEntry)entries.nextElement(); if(entry.isDirectory()) { (new File(entry.getName())).mkdir(); continue; } searchString(runner,entry.getName(),new BufferedInputStream(zipFile.getInputStream(entry)),Out_File,final_output,search_string,stats); } zipFile.close(); } else { searchString(runner,Source_file.toString(),new BufferedInputStream(new FileInputStream(Source_file)),Out_File,final_output,search_string,stats); } } catch(Exception e){ System.out.println(e); e.printStackTrace(); } } /********* Reads the Input Files and Searches for the String ******************************/ public void searchString(Thread runner,String Source_File,BufferedInputStream in,File output_file,File final_output,String search,String stats) { int count = 0; int countw = 0; int countl=0; String s; String[] str; String newLine = System.getProperty("line.separator"); try { BufferedReader br2 = new BufferedReader(new InputStreamReader(in)); //OutputFile outfile = new OutputFile(); BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(output_file,true)); Buffer Buf = new Buffer(); //StringBuffer sb = new StringBuffer(); StringBuffer sb1 = new StringBuffer(); while((s = br2.readLine()) != null ) { str = s.split(search); count = str.length-1; countw += count; if(s.contains(search)){ countl++; sb.append(s); sb.append(newLine); } if(countl%100==0) { System.out.println("inside count"); Buf.setBuffers(sb.toString()); sb.delete(0,sb.length()); System.out.println("outside notify"); synchronized(runner) { runner.notify(); } //outfile.WriteFile(sb,bufferedWriter); //sb.delete(0,sb.length()); } } } synchronized(runner) { runner.notify(); } br2.close(); in.close(); if(countw == 0) { System.out.println("Input File : "+Source_File ); System.out.println("Word not found"); System.exit(0); } else { System.out.println("Input File : "+Source_File ); System.out.println("Matched word count : "+countw ); System.out.println("Lines with Search String : "+countl); System.out.println("Output File : "+output_file.toString()); System.out.println(); } } catch(Exception e){ System.out.println(e); e.printStackTrace(); } } }

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  • Problem loading java properties

    - by markovuksanovic
    I am trying to load properties from a file (test.properties) The code I use is as follows: URL url = getClass().getResource("../resources/test.properties"); properties.load(url.openStream()); But when executing the second line I get a NPE. (null pointer exception) I'm not sure what's wrong here... I have checked that the file exists at the location where URL points to... Any help is appreciated....

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  • Java: Line appears when using AffineTransform to scale image

    - by Malakim
    Hi, I'm having a problem with image scaling. When I use the following code to scale an image it ends up with a line either at the bottom or on the right side of the image. double scale = 1; if (scaleHeight >= scaleWidth) { scale = scaleWidth; } else { scale = scaleHeight; } AffineTransform af = new AffineTransform(); af.scale(scale, scale); AffineTransformOp operation = new AffineTransformOp(af, AffineTransformOp.TYPE_NEAREST_NEIGHBOR); BufferedImage bufferedThumb = operation.filter(img, null); The original image is here: http://tinyurl.com/yzv6r7h The scaled image: http://tinyurl.com/yk6e8ga Does anyone know why the line appears? Thanks!

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  • Java Concurrency : Volatile vs final in "cascaded" variables?

    - by Tom
    Hello Experts, is final Map<Integer,Map<String,Integer>> status = new ConcurrentHashMap<Integer, Map<String,Integer>>(); Map<Integer,Map<String,Integer>> statusInner = new ConcurrentHashMap<Integer, Map<String,Integer>>(); status.put(key,statusInner); the same as volatile Map<Integer,Map<String,Integer>> status = new ConcurrentHashMap<Integer, Map<String,Integer>>(); Map<Integer,Map<String,Integer>> statusInner = new ConcurrentHashMap<Integer, Map<String,Integer>>(); status.put(key,statusInner); in case the inner Map is accessed by different Threads? or is even something like this required: volatile Map<Integer,Map<String,Integer>> status = new ConcurrentHashMap<Integer, Map<String,Integer>>(); volatile Map<Integer,Map<String,Integer>> statusInner = new ConcurrentHashMap<Integer, Map<String,Integer>>(); status.put(key,statusInner); In case the it is NOT a "cascaded" map, final and volatile have in the end the same effect of making shure that all threads see always the correct contents of the Map... But what happens if the Map iteself contains a map, as in the example... How do I make shure that the inner Map is correctly "Memory barriered"? Tanks! Tom

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  • java runtime tracing library to replace system.out.println

    - by Grzegorz Oledzki
    Have you heard of any library which would allow me to set up a tracing for specific methods at runtime? Instead of adding (and removing) lots of System.out.println in my code (and having to re-compile and re-deploy) I would like to have a magic thing which would print out a line for each call of selected method without any change in the code. This would work without re-compiling, so some kind of JVM agent (or some non-standard JVM would be needed?). Sounds like a job for aspect programming? A typical scenario would be to start an application, configure the traced methods dynamically (in a separate file or similar) and then everytime a selected method is called a line with its name (and arguments) is printed out to System.out (or some log file). Naturally one could think of tens of additional features, but this basic set would be a great tool. BTW, I use Eclipse interactive debugger too, not only the System.out tracing technique, but both have some advantages and sometimes Eclipse is not enough.

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  • Java Reflection Utility

    - by DD
    Is there a utility to get a property which isnt prefixed by get from an object using reflection similar to BeanUtils? e.g. if I specify "hashcode" and I want to get the object.hashcode() value. Thanks.

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