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  • Invoke a subclass method of an anonymous class

    - by arjacsoh
    I am trying right now to dig into anonymous classes and one question was just arised I 'd prefer not to refer to much details and to pose my question straightforward: How can I invoke the method sizzle() in the following anonymous class: public class Popcorn { public void pop() { System.out.println("popcorn"); } } class Food { Popcorn p = new Popcorn() { public void sizzle() { System.out.println("anonymous sizzling popcorn"); } public void pop() { System.out.println("anonymous popcorn"); } }; public void popIt() { p.pop(); // OK, Popcorn has a pop() method p.sizzle(); // Not Legal! Popcorn does not have sizzle() } } It is known and definite in polymorphism rules that a refernce of a superclass cannot invoke methods of subclass without downcasting (even if it refers to an object of the given subclass). However in the above case what is the "key" to invoke the sizzle() method?

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  • Interrupt an Http Request blocked in read() on Android

    - by twk
    Using the Apache Http stack on Android, I'm trying to force a thread out of a call to read. This is what the stack looks like: OSNetworkSystem.receiveStreamImpl(FileDescriptor, byte[], int, int, int) line: not available [native method] OSNetworkSystem.receiveStream(FileDescriptor, byte[], int, int, int) line: 478 PlainSocketImpl.read(byte[], int, int) line: 565 SocketInputStream.read(byte[], int, int) line: 87 SocketInputBuffer(AbstractSessionInputBuffer).fillBuffer() line: 103 SocketInputBuffer(AbstractSessionInputBuffer).read(byte[], int, int) line: 134 IdentityInputStream.read(byte[], int, int) line: 86 EofSensorInputStream.read(byte[], int, int) line: 159 Fetcher.readStream() line: 89 I've tried InputStream.close(), Thread.Interrupt(), and HttpUriRequest.abort(), without any success. Any ideas? I'm also open to some kind of non-blocking IO, but I don't see any way to do that with the HttpUriRequest object. Thanks!

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  • Why a "private static" is not seen in a method?

    - by Roman
    I have a class with the following declaration of the fields: public class Game { private static String outputFileName; .... } I set the value of the outputFileName in the main method of the class. I also have a write method in the class which use the outputFileName. I always call write after main sets value for outputFileName. But write still does not see the value of the outputFileName. It say that it's equal to null. Could anybody, pleas, tell me what I am doing wrong? ADDED As it is requested I post more code: In the main: String outputFileName = userName + "_" + year + "_" + month + "_" + day + "_" + hour + "_" + minute + "_" + second + "_" + millis + ".txt"; f=new File(outputFileName); if(!f.exists()){ try { f.createNewFile(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } System.out.println("IN THE MAIN!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"); System.out.println("------>" + outputFileName + "<------"); This line outputs me the name of the file. Than in the write I have: public static void write(String output) { // Open a file for appending. System.out.println("==========>" + outputFileName + "<============"); ...... } And it outputs null.

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  • The fastest way to do a collection subtraction

    - by Tony
    I have two Sets. Set<B> b is the subset of Set<A> a. they're both very huge Sets. I want to subtract b from a , what's the best practice to do this common operation ? I've written to many codes like this , and I don't think it's efficient. what's your idea ? for(int i = 0 ; i < a.size(); i++) { for (int j=0 ; j < b.size() ;j++) { // do comparison , if found equals ,remove from a break; } } And I want to find an algorithm , not only applies to Sets, also works for Array.

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  • Passing empty list as parameter to JPA query throws error

    - by Tuukka Mustonen
    If I pass an empty list into a JPA query, I get an error. For example: List<Municipality> municipalities = myDao.findAll(); // returns empty list em.createQuery("SELECT p FROM Profile p JOIN p.municipality m WHERE m IN (:municipalities)") .setParameter("municipalities", municipalities) .getResultList(); Because the list is empty, Hibernate generates this in SQL as "IN ()", which gives me error with Hypersonic database. There is a ticket for this in Hibernate issue tracking but there are not many comments/activity there. I don't know about support in other ORM products or in JPA spec either. I don't like the idea of having to manually check for null objects and empty lists every time. Is there some commonly known approach/extension to this? How do you handle these situations?

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  • How does this code break the Law of Demeter?

    - by Dave Jarvis
    The following code breaks the Law of Demeter: public class Student extends Person { private Grades grades; public Student() { } /** Must never return null; throw an appropriately named exception, instead. */ private synchronized Grades getGrades() throws GradesException { if( this.grades == null ) { this.grades = createGrades(); } return this.grades; } /** Create a new instance of grades for this student. */ protected Grades createGrades() throws GradesException { // Reads the grades from the database, if needed. // return new Grades(); } /** Answers if this student was graded by a teacher with the given name. */ public boolean isTeacher( int year, String name ) throws GradesException, TeacherException { // The method only knows about Teacher instances. // return getTeacher( year ).nameEquals( name ); } private Grades getGradesForYear( int year ) throws GradesException { // The method only knows about Grades instances. // return getGrades().getForYear( year ); } private Teacher getTeacher( int year ) throws GradesException, TeacherException { // This method knows about Grades and Teacher instances. A mistake? // return getGradesForYear( year ).getTeacher(); } } public class Teacher extends Person { public Teacher() { } /** * This method will take into consideration first name, * last name, middle initial, case sensitivity, and * eventually it could answer true to wild cards and * regular expressions. */ public boolean nameEquals( String name ) { return getName().equalsIgnoreCase( name ); } /** Never returns null. */ private synchronized String getName() { if( this.name == null ) { this.name == ""; } return this.name; } } Questions How is the LoD broken? Where is the code breaking the LoD? How should the code be written to uphold the LoD?

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  • log4j properties file: how to configure ?

    - by EugeneP
    Is it right that the procedure of using log4j looks like this: 1) put a .properties file somewhere in a project folder 2) in an initialization method, that runs only once, invoke PropertyConfigurator.configure("path_to_file"); 3) in every method we need to use logger we define a static logger variable and simply invoke getLogger(class) I'm asking you this: what if the initialization module is not defined? Where to put "log4j.properties" file so that we wouldn't need to invoke propertyconfigurator.configure at all, or if it's not possible, is it ok to invoke PropertyConfigurator.configure("path_to_file") in every method that uses a logger?

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  • Servlet requests are executed sequentially for no apparent reason in Glassfish v3

    - by Fabien Benoit
    Hi, I'm using Glassfish 3 Web profile and can't get http workers to execute concurrently requests on a servlet. This is how i observed the problem. I've made a very simple servlet, that writes the current thread name to the standard output and sleep for 10 seconds : protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println(Thread.currentThread().getName()); try { Thread.sleep(10000); // 10 sec } catch (InterruptedException ex) {} } } And when i'm running several simultaneous requests, I clearly see in the logs that the requests are sequentially executed (one trace every 10 seconds). INFO: http-thread-pool-8080-(2) (10 seconds later...) INFO: http-thread-pool-8080-(1) (10 seconds later...) INFO: http-thread-pool-8080-(2) etc. All my GF settings are untouched - it's the out-of-the-box config (the default thread pool is 2 threads min, 5 max if I recall properly). ...I really don't understand why the sleep() block all the others worker threads. Any insight would be greatly appreciated ! Thanks, Fabien

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  • JPA @ManyToMany on only one side?

    - by Ethan Leroy
    I am trying to refresh the @ManyToMany relation but it gets cleared instead... My Project class looks like this: @Entity public class Project { ... @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER) @JoinTable(name = "PROJECT_USER", joinColumns = @JoinColumn(name = "PROJECT_ID", referencedColumnName = "ID"), inverseJoinColumns = @JoinColumn(name = "USER_ID", referencedColumnName = "ID")) private Collection<User> users; ... } But I don't have - and I don't want - the collection of Projects in the User entity. When I look at the generated database tables, they look good. They contain all columns and constraints (primary/foreign keys). But when I persist a Project that has a list of Users (and the users are still in the database), the mapping table doesn't get updated gets updated but when I refresh the project afterwards, the list of Users is cleared. For better understanding: Project project = ...; // new project with users that are available in the db System.out.println(project getUsers().size()); // prints 5 em.persist(project); System.out.println(project getUsers().size()); // prints 5 em.refresh(project); System.out.println(project getUsers().size()); // prints 0 So, how can I refresh the relation between User and Project?

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  • How do I get the size of a response from a Spring 2.5 HTTP remoting call?

    - by aarestad
    I've been poking around the org.springframework.remoting.httpinvoker package in Spring 2.5 trying to find a way to get visibility into the size of the response, but I keep going around in circles. Via another question I saw here, I think what I want to do is get a handle on the InputStream that represents the response from the server, and then wrap it with an Apache commons-io CountingInputStream. What's the best way to go about doing this? For the moment, I'd be happy with just printing the size of the response to stdout, but eventually I want to store it in a well-known location in my app for optional display.

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  • Sorting a text file by date - Date looks like DD/MM/YYYY

    - by John N
    I am trying to sort the dates from the earliest to the latest. I was thinking about using the bufferedreader and do a try searching the first 2 characters of the string and then the 4th and 5th characters and finally the 7th and 8th characters, ignoring the slashes. The following is an example of the text file I have: 04/24/2010 - 2000.0 (Deposit) 09/05/2010 - 20.0 (Fees) 02/30/2007 - 600.0 (Deposit) 06/15/2009 - 200.0 (Fees) 08/23/2010 - 300.0 (Deposit) 06/05/2006 - 500.0 (Fees)

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  • Spring and hibernate.cfg.xml

    - by Steve Kuo
    How do I get Spring to load Hibernate's properties from hibernate.cfg.xml? We're using Spring and JPA (with Hibernate as the implementation). Spring's applicationContext.xml specifies the JPA dialect and Hibernate properties: <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalEntityManagerFactoryBean"> <property name="jpaDialect"> <bean class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" /> </property> <property name="jpaProperties"> <props> <prop key="hibernate.dialect">org.hibernate.dialect.MySQLInnoDBDialect</prop> </props> </property> </bean> In this configuration, Spring is reading all the Hibernate properties via applicationContext.xml . When I create a hibernate.cfg.xml (located at the root of my classpath, the same level as META-INF), Hibernate doesn't read it at all (it's completely ignored). What I'm trying to do is configure Hibernate second level cache by inserting the cache properties in hibernate.cfg.xml: <cache usage="transactional|read-write|nonstrict-read-write|read-only" region="RegionName" include="all|non-lazy" />

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  • Where to put default-servlet-handler in Spring MVC configuration

    - by gigadot
    In my web.xml, the default servlet mapping, i.e. /, is mapped to Spring dispatcher. In my Spring dispatcher configuration, I have DefaultAnnotationHandlerMapping, ControllerClassNameHandlerMapping and AnnotationMethodHandlerAdapter which allows me to map url to controllers either by its class name or its @Requestmapping annotation. However, there are some static resources under the web root which I also want spring dispatcher to serve using default servlet. According to Spring documentation, this can be done using <mvc:default-servlet-handler/> tag. In the configuration below, there are 4 candidate locations that I marked which are possible to insert this tag. Inserting the tag in different location causes the dispatcher to behave differently as following : Case 1 : If I insert it at location 1, the dispatcher will no longer be able to handle mapping by the @RequestMapping and controller class name but it will be serving the static content normally. Cas 2, 3 : It will be able to handle mapping by the @RequestMapping and controller class name as well as serving the static content if other mapping cannot be done successfully. Case 4 : It will not be able to serve the static contents. Therefore, Case 2 and 3 are desirable .According to Spring documentation, this tag configures a handler which precedence order is given to lowest so why the position matters? and Which is the best position to put this tag? <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd"> <context:annotation-config/> <context:component-scan base-package="webapp.controller"/> <!-- Location 1 --> <!-- Enable annotation-based controllers using @Controller annotations --> <bean id="annotationUrlMapping" class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping"/> <!-- Location 2 --> <bean id="controllerClassNameHandlerMapping" class="org.springframework.web.servlet.mvc.support.ControllerClassNameHandlerMapping"/> <!-- Location 3 --> <bean id="annotationMethodHandlerAdapter" class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/> <!-- Location 4 --> <mvc:default-servlet-handler/> <!-- All views are JSPs loaded from /WEB-INF/jsp --> <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/> <property name="prefix" value="/WEB-INF/jsp/"/> <property name="suffix" value=".jsp"/> </bean> </beans>

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  • Test problem using JUnitPerf

    - by allenzzzxd
    Hi, guys, I'm writing a JUnit test using JUnitPerf. Here, I want to generate some entries and use them to update a database. To test the capacity of the database, I want several test to run simultaneously or randomly, so I use, for example: Test loadTest = new LoadTest(testCase, n); But, still, I have to insure that in each test, a different update source will be used so that a different entry in the database will be updated. So my question is how can I realize this? Thanks a lot Allen

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  • How to prevent popups when loading a keystore

    - by Newtopian
    Hi as corollary to this question I wanted to ask if you know how to prevent the poping of dialogue either to ask for password or to ask to insert a certificate. We are currently building a system where we have to use the windows keystore to get certificates that are stored on USB token containing both reader and certificate. Unlike the original question we do not experience problems when loading the keystore but when we are accessing it. If there is only a single certificate in the keystore no problem, we get the appropriate password popup at the appropriate time and that's it. However if a second USB key gets inserted in the system and later removed the entry remains in the keystore and from then-on every time we try to access information in the keystore we get a popup to insert the key. This occurs for every certificates in the store for which the key is not currently connected to the computer. The system we are interfacing with that requires these certificates necessitates that we perform multiple cryptographic operations and to have these popups to come up every times is rather annoying to say the least.

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  • Drawing star shapes with variable parameters

    - by owca
    Hi. I have task to write program allowing users to draw stars, which can differ in size and amount of arms. When I was dealing with basic stars I was doing it with GeneralPath and tables of points : int xPoints[] = { 55, 67, 109, 73, 83, 55, 27, 37, 1, 43 }; int yPoints[] = { 0, 36, 36, 54, 96, 72, 96, 54, 36, 36 }; Graphics2D g2d = ( Graphics2D ) g; GeneralPath star = new GeneralPath(); star.moveTo( xPoints[ 0 ], yPoints[ 0 ] ); for ( int k = 1; k < xPoints.length; k++ ) star.lineTo( xPoints[ k ], yPoints[ k ] ); star.closePath(); g2d.fill( star ); What method should I choose for drawing stars with variable inner and outer radius, as well as different amount of arms ? This is what I should obtain :

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  • Tomcat - Redirect to Error Page when ServletContextListener fails

    - by Vic
    When Tomcat starts it calls my ServletContextListener to obtain a database connection, which I will later use in other servlets with getServletContext(). It is called in my web.xml as: listener listener-class org.ppdc.database.DBCPoolingListener /listener-class /listener (I removed the < because they wouldn't display properly in this message. If I cannot connect to the database when Tomcat starts up I get a 404 error, because Tomcat cannot start the application. How can I redirect the user to a custom error page at this point? I tried the following in my web.xml (I have the < brackets in the original): (error-page) (error-code404/error-code) (location/file_not_found.html/location) (/error-page) Any ideas on how to redirect a user to one of my error pages when Tomcat tries to start the application? Thanks Vic

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  • Creating JTable Row Header

    - by Chandu
    Hi all, I'm new to JTable.I'm working in Swings using JTable & Toplink(JPA). I have two buttons "add Row", "Del Row" and I have some records displayed from db. when ever "add row" is clicked a new record, row header should be added to JTable with an auto increment number displayed in sequential order to the JTable Row Header. During deletion using "Del row " button the record has to be deleted & not its corresponding header so that next rows got updated to the previous headers & the auto increment number remain unchanged and always be in sequence. please help me on this regard. Thanks in advance, Chandu

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  • How convince other developers not to ignore Exceptions?

    - by Mnementh
    Recently I encountered a bug in an application I took over from another developer. I debugged for the reason and over an hour later I realized, that the problem wasn't the code producing the exception, but some code executed before this returning wrong data. If I dived into this, I encountered the following: try { ... } catch (XYException e){} If the Exception would have been propagated (a change I did), I would have found the reason for the bugs in a few minutes, as the stacktrace had pointed me to the problem. So how can I convince other developers to never catch and ignore exceptions in this way?

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  • Counting the number of visitors for a web page - JavaScript and Struts

    - by Dj
    Hi i am Dhananjay, I need to keep track of the number of visitors to a web page. I have planned like this: on load of the home page, I will call a javascript callCounter(); From javascript, I need then to call an action and update a record in database. Please help me with this. How do i call the action? I should be in the same home jsp after updating database. Thanks in advance, Dhananjay

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  • Write Tomcat 5.5 output to one of Tomcat's log files

    - by Spiderman
    I'd like that all the output that is shown in Tomcat's console will be saved into a file including the output on startup and shutdown of Tomcat. How can I do this? I looked at apache documentation about logging, Do I need to change something in the logging.properties can I trust log4j to write message from the first message on startup to the last message on shutdown?

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