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  • Removing PDF attachments via itext

    - by r00fus
    I'm trying to remove attachments from a number of my pdf files (I can extract via pdftk, so preserving them is not an issue). I coded the following based on an example found from a google search: import java.io.FileOutputStream; import java.io.IOException; import com.lowagie.text.*; import com.lowagie.text.pdf.*; class pdfremoveattachment { public static void main(String[] args) throws IOException, DocumentException { if (args.length < 2) { System.out.println("Usage: java PDFremoveAttachments source.pdf target.pdf"); System.exit(1); } PdfReader sourcePDF = new PdfReader(args[0]); removeAttachments(sourcePDF); FileOutputStream targetFOS = new FileOutputStream(args[1]); PdfStamper targetPDF = new PdfStamper(sourcePDF,targetFOS); targetPDF.close(); } public static void removeAttachments(PdfReader reader) { PdfDictionary catalog = reader.getCatalog(); // System.out.println(catalog.getAsDict(PdfName.NAME)); // this would print "null" PdfDictionary names = (PdfDictionary)PdfReader.getPdfObject(catalog.get(PdfName.NAMES)); // System.out.println(names.toString()); //this returns NPE if( names != null) { PdfDictionary files = (PdfDictionary) PdfReader.getPdfObject(names.get(PdfName.FILEATTACHMENT)); if( files!= null ){ for( Object key : files.getKeys() ){ files.remove((PdfName)key); } files = (PdfDictionary) PdfReader.getPdfObject(names.get(PdfName.EMBEDDEDFILES)); } if( files!= null ){ for( Object key : files.getKeys() ){ files.remove((PdfName)key); } reader.removeUnusedObjects(); } } } } If anyone knows how I might be able to remove attachments, I'd greatly appreciate a reply.

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  • jmap -histo is missing a lot of memory

    - by ripper234
    I have a JVM with 12 gigs of total RAM, out of which 7 GB is allocated to the old generation. There seems to be some memory leak, because almost the entire old gen is full, and will not release when I schedule a GC (the process is not doing anything else at that time). A jmap -histo dump only reveals less than 1 gigabyte worth of objects. Where are the missing 6 gigs? What better tool do you propose for diagnosing this? Here is the top of the jmap output: num #instances #bytes class name ---------------------------------------------- 1: 429853 68725736 <constMethodKlass> 2: 429853 51594040 <methodKlass> 3: 37503 49611368 <constantPoolKlass> 4: 37503 31109576 <instanceKlassKlass> 5: 191716 28019968 [C 6: 32573 26933152 <constantPoolCacheKlass> 7: 86158 13789560 [I 8: 53532 11244232 [B 9: 284 10507216 [J 10: 137608 7210664 <symbolKlass> 11: 203072 6498304 java.lang.String 12: 10132 5219512 <methodDataKlass> 13: 39694 4128176 java.lang.Class 14: 55713 3792816 [S 15: 61816 3141936 [[I 16: 90109 2883488 java.util.HashMap$Entry

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  • Packaging reference documentation with jar file

    - by soren.enemaerke
    We are porting our .NET library to a java equivalent and is now looking at how to distribute this port. Packaging the classes into a jar-file seems like best practice and we would then ship this jar file in a zip along with some license terms. But what about the documentation? In .NET land it seems like best practice to distribute the xml file that can be consumed by tooling (Visual Studio) but we can't seem to find such best practices for java. We have javadoc comments on our public classes and interfaces, so we are just looking for a way to generate and distribute these comments in a way that is developer friendly (we're thinking easily consumed from various IDEs). What are developers expecting and how do you best deliver this? We would really prefer to bundle the documentation along with the jar file and not have to host the documentation on our website EDIT: We would like for our documentation to appear inside the java IDEs so we want to provide the documentation in a way that integrates into the IDEs as gracefully as possible. In .NET land this is as an xml file placed next to the .dll file, but is there a similar concept for jar files that enables the integration into tooling? PS: We are developing in Eclipse and have an ant task doing the building and jar-file packaing in our automated build.

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  • Hazelcast Distributed Executor Service KeyOwner

    - by János Veres
    I have problem understanding the concept of Hazelcast Distributed Execution. It is said to be able to perform the execution on the owner instance of a specific key. From Documentation: <T> Future<T> submitToKeyOwner(Callable<T> task, Object key) Submits task to owner of the specified key and returns a Future representing that task. Parameters: task - task key - key Returns: a Future representing pending completion of the task I believe that I'm not alone to have a cluster built with multiple maps which might actually use the same key for different purposes, holding different objects (e.g. something along the following setup): IMap<String, ObjectTypeA> firstMap = HazelcastInstance.getMap("firstMap"); IMap<String, ObjectTypeA_AppendixClass> secondMap = HazelcastInstance.getMap("secondMap"); To me it seems quite confusing what documentation says about the owner of a key. My real frustration is that I don't know WHICH - in which map - key does it refer to? The documentation also gives a "demo" of this approach: import com.hazelcast.core.Member; import com.hazelcast.core.Hazelcast; import com.hazelcast.core.IExecutorService; import java.util.concurrent.Callable; import java.util.concurrent.Future; import java.util.Set; import com.hazelcast.config.Config; public void echoOnTheMemberOwningTheKey(String input, Object key) throws Exception { Callable<String> task = new Echo(input); HazelcastInstance hz = Hazelcast.newHazelcastInstance(); IExecutorService executorService = hz.getExecutorService("default"); Future<String> future = executorService.submitToKeyOwner(task, key); String echoResult = future.get(); } Here's a link to the documentation site: Hazelcast MultiHTML Documentation 3.0 - Distributed Execution Did any of you guys figure out in the past what key does it want?

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  • Total Order between !different! volatile variables?

    - by andreas
    Hi all, Consider the following Java code: volatile boolean v1 = false; volatile boolean v2 = false; //Thread A v1 = true; if (v2) System.out.println("v2 was true"); //Thread B v2 = true; if (v1) System.out.println("v1 was true"); If there was a globally visible total order for volatile accesses then at least one println would always be reached. Is that actually guaranteed by the Java Standard? Or is an execution like this possible: A: v1 = true; B: v2 = true; A: read v2 = false; B: read v1 = false; A: v2 = true becomes visible (after the if) B: v1 = true becomes visible (after the if) I could only find statements about accesses to the same volatile variable in the Standard (but I might be missing something). "A write to a volatile variable (§8.3.1.4) v synchronizes-with all subsequent reads of v by any thread (where subsequent is defined according to the synchronization order)." http://java.sun.com/docs/books/jls/third_edition/html/memory.html#17.4.4 Thanks!

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  • Set fields with instrospection - Problem with String.valueOf(String)

    - by fabb
    Hey there! I'm setting public fields of the Object 'this' via reflection. Both the field name and the value are given as String. I use several various field types: Boolean, Integer, Float, Double, an own enum, and a String. It works with all of them except with a String. The exception that gets thrown is that no method with the Signature String.valueOf(String) exists... Now I use a dirty instanceof workaround to detect if each field is a String and in that case just copy the value to the field. private void setField(String field, String value) throws Exception { Field wField = this.getClass().getField(field); if(wField.get(this) instanceof String){ //TODO dirrrrty hack //stupid workaround as java.lang.String.valueOf(java.lang.String) fails... wField.set(this, value); }else{ Method parseMethod = wField.getType().getMethod("valueOf", new Class[]{String.class}); wField.set(this, parseMethod.invoke(wField, value)); } } Any ideas how to avoid that workaround? Do you think java.lang.String should support the method valueOf(String)? thanks, fabb

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  • Ruby and duck typing: design by contract impossible?

    - by davetron5000
    Method signature in Java: public List<String> getFilesIn(List<File> directories) similar one in ruby def get_files_in(directories) In the case of Java, the type system gives me information about what the method expects and delivers. In Ruby's case, I have no clue what I'm supposed to pass in, or what I'll expect to receive. In Java, the object must formally implement the interface. In Ruby, the object being passed in must respond to whatever methods are called in the method defined here. This seems highly problematic: Even with 100% accurate, up-to-date documentation, the Ruby code has to essentially expose its implementation, breaking encapsulation. "OO purity" aside, this would seem to be a maintenance nightmare. The Ruby code gives me no clue what's being returned; I would have to essentially experiment, or read the code to find out what methods the returned object would respond to. Not looking to debate static typing vs duck typing, but looking to understand how you maintain a production system where you have almost no ability to design by contract. Update No one has really addressed the exposure of a method's internal implementation via documentation that this approach requires. Since there are no interfaces, if I'm not expecting a particular type, don't I have to itemize every method I might call so that the caller knows what can be passed in? Or is this just an edge case that doesn't really come up?

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  • Best Practice With JFrame Constructors?

    - by David Barry
    In both my Java classes, and the books we used in them laying out a GUI with code heavily involved the constructor of the JFrame. The standard technique in the books seems to be to initialize all components and add them to the JFrame in the constructor, and add anonymous event handlers to handle events where needed, and this is what has been advocated in my class. This seems to be pretty easy to understand, and easy to work with when creating a very simple GUI, but seems to quickly get ugly and cumbersome when making anything other than a very simple gui. Here is a small code sample of what I'm describing: public class FooFrame extends JFrame { JLabel inputLabel; JTextField inputField; JButton fooBtn; JPanel fooPanel; public FooFrame() { super("Foo"); fooPanel = new JPanel(); fooPanel.setLayout(new FlowLayout()); inputLabel = new JLabel("Input stuff"); fooPanel.add(inputLabel); inputField = new JTextField(20); fooPanel.add(inputField); fooBtn = new JButton("Do Foo"); fooBtn.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { //handle event } }); fooPanel.add(fooBtn); add(fooPanel, BorderLayout.CENTER); } } Is this type of use of the constructor the best way to code a Swing application in java? If so, what techniques can I use to make sure this type of constructor is organized and maintainable? If not, what is the recommended way to approach putting together a JFrame in java?

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  • Improving field get and set performance with ASM or Javassist

    - by ng
    I would like to avoid reflection in an open source project I am developing. Here I have classes like the following. public class PurchaseOrder { @Property private Customer customer; @Property private String name; } I scan for the @Property annotation to determine what I can set and get from the PurchaseOrder reflectively. There are many such classes all using java.lang.reflect.Field.get() and java.lang.reflect.Field.set(). Ideally I would like to generate for each property an invoker like the following. public interface PropertyAccessor<S, V> { public void set(S source, V value); public V get(S source); } Now when I scan the class I can create a static inner class of PurchaseOrder like so. static class customer_Field implements PropertyAccessor<PurchaseOrder, Customer> { public void set(PurchaseOrder order, Customer customer) { order.customer = customer; } public Customer get(PurchaseOrder order) { return order.customer; } } With these I totally avoid the cost of reflection. I can now set and get from my instances with native performance. Can anyone tell me how I would do this. A code example would be great. I have searched the net for a good example but can find nothing like this. The ASM and Javasist examples are pretty poor also. The key here is that I have an interface that I can pass around. So I can have various implementations, perhaps one with Java Reflection as a default, one with ASM, and one with Javassist? Any help would be greatly appreciated.

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  • How to parse a custom XML-style error code response from a website

    - by user1870127
    I'm developing a program that queries and prints out open data from the local transit authority, which is returned in the form of an XML response. Normally, when there are buses scheduled to run in the next few hours (and in other typical situations), the XML response generated by the page is handled correctly by the java.net.URLConnection.getInputStream() function, and I am able to print the individual results afterwards. The problem is when the buses are NOT running, or when some other problem with my queries develops after it is sent to the transit authority's web server. When the authority developed their service, they came up with their own unique error response codes, which are also sent as XMLs. For example, one of these error messages might look like this: <Error xmlns:i="http://www.w3.org/2001/XMLSchema-instance"> <Code>3005</Code> <Message>Sorry, no stop estimates found for given values.</Message> </Error> (This code and similar is all that I receive from the transit authority in such situations.) However, it appears that URLConnection.getInputStream() and some of its siblings are unable to interpret this custom code as a "valid" response that I can handle and print out as an error message. Instead, they give me a more generic HTTP/1.1 404 Not Found error. This problem cascades into my program which then prints out a java.io.FileNotFoundException error pointing to the offending input stream. My question is therefore two-fold: 1. Is there a way to retrieve, parse, and print a custom XML-formatted error code sent by a web service using the plugins that are available in Java? 2. If the above is not possible, what other tools should I use or develop to handle such custom codes as described?

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  • Webcrawler, feedback?

    - by Jan Kuboschek
    Hey folks, every once in a while I have the need to automate data collection tasks from websites. Sometimes I need a bunch of URLs from a directory, sometimes I need an XML sitemap (yes, I know there is lots of software for that and online services). Anyways, as follow up to my previous question I've written a little webcrawler that can visit websites. Basic crawler class to easily and quickly interact with one website. Override "doAction(String URL, String content)" to process the content further (e.g. store it, parse it). Concept allows for multi-threading of crawlers. All class instances share processed and queued lists of links. Instead of keeping track of processed links and queued links within the object, a JDBC connection could be established to store links in a database. Currently limited to one website at a time, however, could be expanded upon by adding an externalLinks stack and adding to it as appropriate. JCrawler is intended to be used to quickly generate XML sitemaps or parse websites for your desired information. It's lightweight. Is this a good/decent way to write the crawler, provided the limitations above? http://pastebin.com/VtgC4qVE - Main.java http://pastebin.com/gF4sLHEW - JCrawler.java http://pastebin.com/VJ1grArt - HTMLUtils.java Thanks for your feedback in advance! :)

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  • JPA native query join returns object but dereference throws class cast exception

    - by masato-san
    I'm using JPQL Native query to join table and query result is stored in List<Object[]>. public String getJoinJpqlNativeQuery() { String final SQL_JOIN = "SELECT v1.bitbit, v1.numnum, v1.someTime, t1.username, t1.anotherNum FROM MasatosanTest t1 JOIN MasatoView v1 ON v1.username = t1.username;" System.out.println("get join jpql native query is being called ============================"); EntityManager em = null; List<Object[]> out = null; try { em = EmProvider.getDefaultManager(); Query query = em.createNativeQuery(SQL_JOIN); out = query.getResultList(); System.out.println("return object ==========>" + out); System.out.println(out.get(0)); String one = out.get(0).toString(); //LINE 77 where ClassCastException System.out.println(one); } catch(Exception e) { } finally { if(em != null) { em.close; } } } The problem is System.out.println("return object ==========>" + out); outputs: return object ==========> [[true, 0, 2010-12-21 15:32:53.0, masatosan, 0.020], [false, 0, 2010-12-21 15:32:53.0, koga, 0.213]] System.out.println(out.get(0)) outputs: [true, 0, 2010-12-21 15:32:53.0, masatosan, 0.020] So I assumed that I can assign return value of out.get(0) which should be String: String one = out.get(0).toString(); But I get weird ClassCastException. java.lang.ClassCastException: java.util.Vector cannot be cast to [Ljava.lang.Object; at local.test.jaxrs.MasatosanTestResource.getJoinJpqlNativeQuery (MasatosanTestResource.java:77) So what's really going on? Even Object[] foo = out.get(0); would throw an ClassCastException :(

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  • return an ArrayList method

    - by Bopeng Liu
    This is a drive method for two other classes. which i posted here http://codereview.stackexchange.com/questions/33148/book-program-with-arraylist I need some help for the private static ArrayList getAuthors(String authors) method. I am kind a beginner. so please help me finish this drive method. or give me some directions. Instruction some of the elements of the allAuthors array contain asterisks “*” between two authors names. The getAuthors method uses this asterisk as a delimiter between names to store them separately in the returned ArrayList of Strings. import java.util.ArrayList; public class LibraryDrive { public static void main(String[] args) { String[] titles = { "The Hobbit", "Acer Dumpling", "A Christmas Carol", "Marley and Me", "Building Java Programs", "Java, How to Program" }; String[] allAuthors = { "Tolkien, J.R.", "Doofus, Robert", "Dickens, Charles", "Remember, SomeoneIdont", "Reges, Stuart*Stepp, Marty", "Deitel, Paul*Deitel, Harvery" }; ArrayList<String> authors = new ArrayList<String>(); ArrayList<Book> books = new ArrayList<Book>(); for (int i = 0; i < titles.length; i++) { authors = getAuthors(allAuthors[i]); Book b = new Book(titles[i], authors); books.add(b); authors.remove(0); } Library lib = new Library(books); System.out.println(lib); lib.sort(); System.out.println(lib); } private static ArrayList<String> getAuthors(String authors) { ArrayList books = new ArrayList<String>(); // need help here. return books; } }

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  • Dynamically added JTable not displaying

    - by Graza
    Java Newbie here. I have a JFrame that I added to my netbeans project, and I've added the following method to it, which creates a JTable. Problem is, for some reason when I call this method, the JTable isn't displayed. Any suggestions? public void showFromVectors(Vector colNames, Vector data) { jt = new javax.swing.JTable(data, colNames); sp = new javax.swing.JScrollPane(jt); //NB: "this" refers to my class DBGridForm, which extends JFrame this.add(sp,java.awt.BorderLayout.CENTER); this.setSize(640,480); } The method is called in the following context: DBGridForm gf = new DBGridForm(); //DBGridForm extends JFrame DBReader.outMatchesTable(gf); gf.setVisible(true); ... where DBReader.outMatchesTable() is defined as static public void outMatchesTable(DBGridForm gf) { DBReader ddb = new DBReader(); ddb.readMatchesTable(null); gf.showFromVectors(ddb.lastRsltColNames, ddb.lastRsltData); } My guess is I'm overlooking something, either about the swing classes I'm using, or about Java. Any ideas?

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  • JSP: How can I still get the code on my error page to run, even if I can't display it?

    - by Josh Hinman
    I've defined an error-page in my web.xml: <error-page> <exception-type>java.lang.Exception</exception-type> <location>/error.jsp</location> </error-page> In that error page, I have a custom tag that I created. The tag handler for this tag e-mails me the stacktrace of whatever error occurred. For the most part this works great. Where it doesn't work great is if the output has already begun being sent to the client at the time the error occurs. In that case, we get this: SEVERE: Exception Processing ErrorPage[exceptionType=java.lang.Exception, location=/error.jsp] java.lang.IllegalStateException I believe this error happens because we can't redirect a request to the error page after output has already started. The work-around I've used is to increase the buffer size on particularly large JSP pages. But I'm trying to write a generic error handler that I can apply to existing applications, and I'm not sure it's feasible to go through hundreds of JSP pages making sure their buffers are big enough. Is there a way to still allow my stack trace e-mail code to execute in this case, even if I can't actually display the error page to the client?

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  • problem with running Servlet on Tomcat: InvocationTargetException

    - by Fahim
    Hi, I am new to Tomcat, and trying to run a simple HelloWorld servlet. I have installed Tomcat 6, and Jdk1.6 on Mandriva Linux, set CLASSPATH and JAVA_HOME. I have the following files and directories: $CATALINA_HOME/webapps/MyApp/WEB_INF/classes/TestServlet.class $CATALINA_HOME/webapps/MyApp/WEB_INF/web.xml My web.xml file contains the following: http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5" <description>ZibJana Localization</description> <display-name>ZibJana Localization</display-name> <!-- Define the servlets for this application--> <servlet> <servlet-name>ZibJana</servlet-name> <servlet-class>TestServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ZibJana</servlet-name> <url-pattern>*</url-pattern> </servlet-mapping> But when I try to invoke my servlet with url http://localhost:8080/MyApp, tomcat fails to launch launch the servlet. I checked in the $CATALINA_HOME/logs/catalina.out log-file and found the following error, which occurs every time I start tomcat service. INFO: Deploying web application directory MyApp 16-Mar-2010 12:05:38 AM org.apache.tomcat.util.digester.Digester endElement SEVERE: End event threw exception java.lang.reflect.InvocationTargetException at sun.reflect.GeneratedMethodAccessor18.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) Please let me know where my mistake is. Thanks in advance.

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  • Foreign/accented characters in sql query

    - by FromCanada
    I'm using Java and Spring's JdbcTemplate class to build an SQL query in Java that queries a Postgres database. However, I'm having trouble executing queries that contain foreign/accented characters. For example the (trimmed) code: JdbcTemplate select = new JdbcTemplate( postgresDatabase ); String query = "SELECT id FROM province WHERE name = 'Ontario';"; Integer id = select.queryForObject( query, Integer.class ); will retrieve the province id, but if instead I did name = 'Québec' then the query fails to return any results (this value is in the database so the problem isn't that it's missing). I believe the source of the problem is that the database I am required to use has the default client encoding set to SQL_ASCII, which according to this prevents automatic character set conversions. (The Java environments encoding is set to 'UTF-8' while I'm told the database uses 'LATIN1' / 'ISO-8859-1') I was able to manually indicate the encoding when the resultSets contained values with foreign characters as a solution to a previous problem with a similar nature. Ex: String provinceName = new String ( resultSet.getBytes( "name" ), "ISO-8859-1" ); But now that the foreign characters are part of the query itself this approach hasn't been successful. (I suppose since the query has to be saved in a String before being executed anyway, breaking it down into bytes and then changing the encoding only muddles the characters further.) Is there a way around this without having to change the properties of the database or reconstruct it? PostScript: I found this function on StackOverflow when making up a title, it didn't seem to work (I might not have used it correctly, but even if it did work it doesn't seem like it could be the best solution.):

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  • finding ALL cycles in a huge sparse matrix

    - by Andy
    Hi there, First of all I'm quite a Java beginner, so I'm not sure if this is even possible! Basically I have a huge (3+million) data source of relational data (i.e. A is friends with B+C+D, B is friends with D+G+Z (but not A - i.e. unmutual) etc.) and I want to find every cycle within this (not necessarily connected) directed graph. I've found this thread (http://stackoverflow.com/questions/546655/finding-all-cycles-in-graph/549402#549402) which has pointed me to Donald Johnson's (elementary) cycle-finding algorithm which, superficially at least, looks like it'll do what I'm after (I'm going to try when I'm back at work on Tuesday - thought it wouldn't hurt to ask in the meanwhile!). I had a quick scan through the code of the Java implementation of Johnson's algorithm (in that thread) and it looks like a matrix of relations is the first step, so I guess my questions are: a) Is Java capable of handling a 3+million*3+million matrix? (was planning on representing A-friends-with-B by a binary sparse matrix) b) Do I need to find every connected subgraph as my first problem, or will cycle-finding algorithms handle disjoint data? c) Is this actually an appropriate solution for the problem? My understanding of "elementary" cycles is that in the graph below, rather than picking out A-B-C-D-E-F it'll pick out A-B-F, B-C-D etc. but that's not the end of the world given the task. E / \ D---F / \ / \ C---B---A d) If necessary, I can simplify the problem by enforcing mutuality in relations - i.e. A-friends-with-B <== B-friends-with-A, and if really necessary I can maybe cut down the data size, but realistically it is always going to be around the 1mil mark. z) Is this a P or NP task?! Am I biting off more than I can chew? Thanks all, any help appreciated! Andy

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  • Question about WeakHashMap

    - by michael
    Hi, In the Javadoc of "http://java.sun.com/j2se/1.4.2/docs/api/java/util/WeakHashMap.html", it said "Each key object in a WeakHashMap is stored indirectly as the referent of a weak reference. Therefore a key will automatically be removed only after the weak references to it, both inside and outside of the map, have been cleared by the garbage collector." And then Note that a value object may refer indirectly to its key via the WeakHashMap itself; that is, a value object may strongly refer to some other key object whose associated value object, in turn, strongly refers to the key of the first value object. But should not both Key and Value should be used weak reference in WeakHashMap? i.e. if there is low on memory, GC will free the memory held by the value object (since the value object most likely take up more memory than key object in most cases)? And if GC free the Value object, the Key Object can be free as well? Basically, I am looking for a HashMap which will reduce memory usage when there is low memory (GC collects the value and key objects if necessary). Is it possible in Java? Thank you.

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  • how to restart a Thread?

    - by wizztjh
    It is a RMI Server object , so many sethumanActivity() might be run , how do i make sure the previous changeToFalse thread will be stop or halt before the new changeToFalse run? t. interrupt ? Basically when sethumanActivity() is invoke , the humanActivity will be set to true , but a thread will be run to set it back to false. But I am thinking for how to disable or kill the thread when another sethumanActivity() invoked? public class VitaminDEngine implements VitaminD { public boolean humanActivity = false; changeToFalse cf = new changeToFalse(); Thread t = new Thread(cf); private class changeToFalse implements Runnable{ @Override public void run() { try { Thread.sleep(4000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } humanActivity = false; } } @Override public void sethumanActivity() throws RemoteException { // TODO Auto-generated method stub humanActivity = true; t.start(); } public boolean gethumanActivity() throws RemoteException { // TODO Auto-generated method stub return humanActivity; } } Edited after the help of SOer package smartOfficeJava; import java.rmi.RemoteException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class VitaminDEngine implements VitaminD { public volatile boolean humanActivity = false; changeToFalse cf = new changeToFalse(); ExecutorService service = Executors.newSingleThreadExecutor(); private class changeToFalse implements Runnable{ @Override public void run() { try { Thread.sleep(4000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } humanActivity = false; } } @Override public synchronized void sethumanActivity() throws RemoteException { humanActivity = true; service.submit(cf); } public synchronized boolean gethumanActivity() throws RemoteException { return humanActivity; } }

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  • Is there a limit for the number of files in a directory on an SD card?

    - by jamesh
    I have a project written for Android devices. It generates a large number of files, each day. These are all text files and images. The app uses a database to reference these files. The app is supposed to clear up these files after a little use (perhaps after a few days), but this process may or may not be working. This is not the subject of this question. Due to a historic accident, the organization of the files are somewhat naive: everything is in the same directory; a .hidden directory which contains a zero byte .nomedia file to prevent the MediaScanner indexing it. Today, I am seeing an error reported: java.io.IOException: Cannot create: /sdcard/.hidden/file-4200.html at java.io.File.createNewFile(File.java:1263) Regarding the sdcard, I see it has plenty of storage left, but counting $ cd /Volumes/NO_NAME/.hidden $ ls | wc -w 9058 Deleting a number of files seems to have allowed the file creation for today to proceed. Regrettably, I did not try touching a new file to try and reproduce the error on a commandline; I also deleted several hundred files rather than a handful. However, my question is: are there hard limits on filesize or number of files in a directory? am I even on the right track here? Nota Bene: The SD card is as-is - i.e. I haven't formatted it, so I would guess it would be a FAT-* format. The FAT-32 format has hard limits of filesize of 2GB (well above the filesizes I am dealing with) and a limit of number of files in the root directory. I am definitely not writing files in the root directory.

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  • Improving field get and set performance with ASM

    - by ng
    I would like to avoid reflection in an open source project I am developing. Here I have classes like the following. public class PurchaseOrder { @Property private Customer customer; @Property private String name; } I scan for the @Property annotation to determine what I can set and get from the PurchaseOrder reflectively. There are many such classes all using java.lang.reflect.Field.get() and java.lang.reflect.Field.set(). Ideally I would like to generate for each property an invoker like the following. public interface PropertyAccessor<S, V> { public void set(S source, V value); public V get(S source); } Now when I scan the class I can create a static inner class of PurchaseOrder like so. static class customer_Field implements PropertyAccessor<PurchaseOrder, Customer> { public void set(PurchaseOrder order, Customer customer) { order.customer = customer; } public Customer get(PurchaseOrder order) { return order.customer; } } With these I totally avoid the cost of reflection. I can now set and get from my instances with native performance. Can anyone tell me how I would do this. A code example would be great. I have searched the net for a good example but can find nothing like this. The ASM examples are pretty poor also. The key here is that I have an interface that I can pass around. So I can have various implementations, perhaps one with Java Reflection as a default, one with ASM, and maybe one with Javassist? Any help would be greatly appreciated.

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  • substitution cypher with different alphabet length

    - by seanizer
    I would like to implement a simple substitution cypher to mask private ids in URLs I know how my IDs will look like (combination of upperchase ascii, digits and underscore), and they will be rather long, as they are composed keys. I would like to use a longer alphabet to shorten the resulting codes (I'd like to use upper and lower case ascii letters, digits and nothing else). So my incoming alphabet would be [A-Z0-9_] (37 chars) and my outgoing alphabet would be [A-Za-z0-9] (62 chars) so a compression of almost 50% would be available. let's say my URLs look like this: /my/page/GFZHFFFZFZTFZTF_24_F34 and I want them to look like this instead: /my/page/Ft32zfegZFV5 Obviously both arrays would be shuffled to bring some random order in. This does not have to be secure. if someone figures it out: fine, but I don't want the scheme to be obvious. My desired solution would be to convert the string to an integer representation of radix 37, convert the radix to 62 and use the second alphabet to write out that number. is there any sample code available that does something similar? Integer.parseInt ( http://java.sun.com/javase/6/docs/api/java/lang/Integer.html#parseInt%28java.lang.String,%20int%29 ) has some similar logic, but it is hard-coded to use standard digit behavior Any hints? I am using java to implement this but code or pseudo-code in any other language is of course also helpful

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  • General JDBC Setup

    - by AeroDroid
    So I have a MySQL database set up on a Debian server and it works fine from a phpMyAdmin client. I'm currently working on a project to write a Java server that would be able to use the MySQL database that is already on this server through a JDBC connection. I've looked at many tutorials and documentations but all of them seem to just explain how to do client-side code, but I have yet to figure out how to even successfully open a JDBC connection to the server. As far as I am concerned, I believe that program has the drivers properly set up because it's not crashing anymore (I simply direct the Java Build Path of my program to the Connector/J provided by MySQL). As far as my program goes, this is what it looks like... import java.sql.*; public class JDBCTest { public static void main(String[] args) { System.out.println("Started!"); try { DriverManager.registerDriver(new com.mysql.jdbc.Driver()); System.out.println("Driver registered. Connecting..."); Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/", "root", "password"); System.out.println("Connected!"); conn.close(); } catch (SQLException e) { System.out.println("Error!"); e.printStackTrace(); } } } This is what's printed... Started! Driver registered. Connecting... It's as if the DriverManager.getConnection(String) just freezes there. I'm sure this is a problem with the server because when I intentionally misspell localhost, or an IP address, the program crashes within 20 seconds. This just hangs there forever. Sorry about this wall of text, but my final question is if anyone has any information what I should do or install on the server to get this to work? Thank you so much!

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  • NullPointerException with static variables

    - by tomekK
    I just hit very strange (to me) behaviour of java. I have following classes: public abstract class Unit { public static final Unit KM = KMUnit.INSTANCE; public static final Unit METERS = MeterUnit.INSTANCE; protected Unit() { } public abstract double getValueInUnit(double value, Unit unit); protected abstract double getValueInMeters(double value); } And: public class KMUnit extends Unit { public static final Unit INSTANCE = new KMUnit(); private KMUnit() { } //here are abstract methods overriden } public class MeterUnit extends Unit { public static final Unit INSTANCE = new MeterUnit(); private MeterUnit() { } ///abstract methods overriden } And my test case: public class TestMetricUnits extends TestCase { @Test public void testConversion() { System.out.println("Unit.METERS: " + Unit.METERS); System.out.println("Unit.KM: " + Unit.KM); double meters = Unit.KM.getValueInUnit(102.11, Unit.METERS); assertEquals(0.10211, meters, 0.00001); } } 1) MKUnit and MeterUnit are both singletons initialized statically, so during class loading. Constructors are private, so they can't be initialized anywhere else. 2) Unit class contains static final references to MKUnit.INSTANCE and MeterUnit.INSTANCE I would expect that: KMUnit class is loaded and instance is created. MeterUnit class is loaded and instance is created. Unit class is loaded and both KM and METERS variable are initialized, they are final so they cant be changed. But when I run my test case in console with maven my result is: T E S T S Running de.audi.echargingstations.tests.TestMetricUnits Unit.METERS: m Unit.KM: null Tests run: 3, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.089 sec <<< FAILURE! - in de.audi.echargingstations.tests.TestMetricUnits testConversion(de.audi.echargingstations.tests.TestMetricUnits) Time elapsed: 0.011 sec <<< ERROR! java.lang.NullPointerException: null at de.audi.echargingstations.tests.TestMetricUnits.testConversion(TestMetricUnits.java:29) Results : Tests in error: TestMetricUnits.testConversion:29 NullPointer And the funny part is that, when I run this test from eclipse via JUnit runner everything is fine, I have no NullPointerException and in console I have: Unit.METERS: m Unit.KM: km So the question is: what can be the reason that KM variable in Unit is null (and in the same time METERS is not null)

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