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  • Setting attributes of a class during construction from **kwargs

    - by Carson Myers
    Python noob here, Currently I'm working with SQLAlchemy, and I have this: from __init__ import Base from sqlalchemy.schema import Column, ForeignKey from sqlalchemy.types import Integer, String from sqlalchemy.orm import relationship class User(Base): __tablename__ = "users" id = Column(Integer, primary_key=True) username = Column(String, unique=True) email = Column(String) password = Column(String) salt = Column(String) openids = relationship("OpenID", backref="users") User.__table__.create(checkfirst=True) #snip definition of OpenID class def create(**kwargs): user = User() if "username" in kwargs.keys(): user.username = kwargs['username'] if "email" in kwargs.keys(): user.username = kwargs['email'] if "password" in kwargs.keys(): user.password = kwargs['password'] return user This is in /db/users.py, so it would be used like: from db import users new_user = users.create(username="Carson", password="1234") new_user.email = "[email protected]" users.add(new_user) #this function obviously not defined yet but the code in create() is a little stupid, and I'm wondering if there's a better way to do it that doesn't require an if ladder, and that will fail if any keys are added that aren't in the User object already. Like: for attribute in kwargs.keys(): if attribute in User: user.__attribute__[attribute] = kwargs[attribute] else: raise Exception("blah") that way I could put this in its own function (unless one hopefully already exists?) So I wouldn't have to do the if ladder again and again, and so I could change the table structure without modifying this code. Any suggestions?

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  • java.lang.NoClassDefFoundError: Could not initialize class org.apache.poi.POIXMLDocument on Jboss 5.0 EAP

    - by nidhin
    Getting following exception in Jboss 5.0 EAP but it work fine in JBoss 5.1 GA. we are using POI 3.7 and jars included are poi-3.7.jar poi-ooxml-schemas.jar poi-ooxml.jar The stack trace is ERROR [org.apache.catalina.core.ContainerBase.[jboss.ueb].[localhost].[fesbcon-Fig].[Faces Servlet]] 3;13;44.4g3pM (http-0.0.0.0-8280-1) Servlet.service() -For servlet Faces Servlet threu exception java.lang.NoClassDe-FFoundError: Could not initialize class org.apache.poi.POIXMLDocument at org.apache.poi.ss.usermodel.HorkbookFactory.create(HorkbookFactory.java:62) at com.-Ferguson.esb.con-Fig.controller.AssociationsExcelUploadController.submit(Unknoun Source) at sun.re-Flect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.re-Flect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.re-Flect.DelegatingMethodAccessorImpl.invoke(Delegating?ethodAccessorImpl.java:25) at java.lang.re-Flect.Method.invoke(Method.java:597) at org.apache.my-Faces.el.MethodBindingImpl.invoke(MethodBindingImpl.java:132) at org.apache.my-Faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:61) Please Advise how to solve this issue in JBoss 5.0 EAP

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  • Eclipselink problem in a javase project

    - by arinte
    I am getting this error when I am running my eclipselink project. [EL Warning]: 2008.12.05 11:47:08.056--java.lang.NoClassDefFoundError: org/jboss/resource/adapter/jdbc/ValidConnectionChecker was thrown on attempt of PersistenceLoadProcessor to load class com.mysql.jdbc.integration.jboss.MysqlValidConnectionChecker. The class is ignored. Exception in thread "main" java.lang.NoClassDefFoundError: org/jboss/resource/adapter/jdbc/ValidConnectionChecker at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(Unknown Source) at java.security.SecureClassLoader.defineClass(Unknown Source) at java.net.URLClassLoader.defineClass(Unknown Source) at java.net.URLClassLoader.access$000(Unknown Source) at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at org.eclipse.persistence.internal.jpa.deployment.PersistenceUnitProcessor.loadClass(PersistenceUnitProcessor.java:261) at org.eclipse.persistence.internal.jpa.metadata.MetadataProcessor.initPersistenceUnitClasses(MetadataProcessor.java:247) at org.eclipse.persistence.internal.jpa.metadata.MetadataProcessor.processEntityMappings(MetadataProcessor.java:422) at org.eclipse.persistence.internal.jpa.deployment.PersistenceUnitProcessor.processORMetadata(PersistenceUnitProcessor.java:299) at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.predeploy(EntityManagerSetupImpl.java:830) at org.eclipse.persistence.internal.jpa.deployment.JPAInitializer.callPredeploy(JPAInitializer.java:101) at org.eclipse.persistence.internal.jpa.deployment.JPAInitializer.initPersistenceUnits(JPAInitializer.java:149) at org.eclipse.persistence.internal.jpa.deployment.JPAInitializer.initialize(JPAInitializer.java:135) at org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactory(PersistenceProvider.java:104) at org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactory(PersistenceProvider.java:64) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:83) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:60) at Main.main(Main.java:32) Caused by: java.lang.ClassNotFoundException: org.jboss.resource.adapter.jdbc.ValidConnectionChecker at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClassInternal(Unknown Source) ... 24 more Any ideas? Why would eclipselink need something from jboss? What jboss jar do I need. I would use open jpa, but for some reason after quit a few persists from my app it starts giving a bunch of stackoverflow errors.

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  • How to solve "java.io.IOException: error=12, Cannot allocate memory" calling Runtime#exec()?

    - by Andrea Francia
    On my system I can't run a simple Java application that start a process. I don't know how to solve. Could you give me some hints how to solve? The program is: [root@newton sisma-acquirer]# cat prova.java import java.io.IOException; public class prova { public static void main(String[] args) throws IOException { Runtime.getRuntime().exec("ls"); } } The result is: [root@newton sisma-acquirer]# javac prova.java && java -cp . prova Exception in thread "main" java.io.IOException: Cannot run program "ls": java.io.IOException: error=12, Cannot allocate memory at java.lang.ProcessBuilder.start(ProcessBuilder.java:474) at java.lang.Runtime.exec(Runtime.java:610) at java.lang.Runtime.exec(Runtime.java:448) at java.lang.Runtime.exec(Runtime.java:345) at prova.main(prova.java:6) Caused by: java.io.IOException: java.io.IOException: error=12, Cannot allocate memory at java.lang.UNIXProcess.<init>(UNIXProcess.java:164) at java.lang.ProcessImpl.start(ProcessImpl.java:81) at java.lang.ProcessBuilder.start(ProcessBuilder.java:467) ... 4 more Configuration of the system: [root@newton sisma-acquirer]# java -version java version "1.6.0_0" OpenJDK Runtime Environment (IcedTea6 1.5) (fedora-18.b16.fc10-i386) OpenJDK Client VM (build 14.0-b15, mixed mode) [root@newton sisma-acquirer]# cat /etc/fedora-release Fedora release 10 (Cambridge) EDIT: Solution This solves my problem, I don't know exactly why: echo 0 /proc/sys/vm/overcommit_memory Up-votes for who is able to explain :) Additional informations, top output: top - 13:35:38 up 40 min, 2 users, load average: 0.43, 0.19, 0.12 Tasks: 129 total, 1 running, 128 sleeping, 0 stopped, 0 zombie Cpu(s): 1.5%us, 0.5%sy, 0.0%ni, 94.8%id, 3.2%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 1033456k total, 587672k used, 445784k free, 51672k buffers Swap: 2031608k total, 0k used, 2031608k free, 188108k cached Additional informations, free output: [root@newton sisma-acquirer]# free total used free shared buffers cached Mem: 1033456 588548 444908 0 51704 188292 -/+ buffers/cache: 348552 684904 Swap: 2031608 0 2031608

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  • BufferedReader.readLine() gives error java.net.SocketException: Software caused connection abort: re

    - by javatcp
    I am trying to code my program such that until the buffered reader gets something in readLine() from my tcp client it should keep running in the while loop checking but I get this error as soon as the program executes Mar 31, 2010 11:03:36 PM deswash.DESWashView$5 run SEVERE: null java.net.SocketException: Software caused connection abort: recv failed at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.read(SocketInputStream.java:129) at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:264) at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:306) at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:158) at java.io.InputStreamReader.read(InputStreamReader.java:167) at java.io.BufferedReader.fill(BufferedReader.java:136) at java.io.BufferedReader.readLine(BufferedReader.java:299) at java.io.BufferedReader.readLine(BufferedReader.java:362) at deswash.DESWashView$5.run(DESWashView.java:448) the second line in the following code throws the error while(running){ String temp = in.readLine(); if(!(temp.equals(null))){ int inid = Integer.parseInt(temp); stationList.add(inid); } }

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  • Jsystem AutoITAgent does not work - java.lang.NoClassDefFoundError: org/apache/xmlrpc/WebServer

    - by lasombra
    Even so the jar files exists and are in the correct folder, I get the NoClassDefFoundError. Why? What I am doing wrong? The Classpath definition is .\thirdparty\lib\;C:\jsystem\runner\lib\ant-jsystem.jar;C:jsystem\runner\lib\cli.jar;C:\jsystem\runner\lib\commons-logging-1.1.jar;C:\jsystem\runner\lib\embeddedCatalina.jar;C:\jsystem\runner\lib\fileParser.jar;C:\jsystem\runner\lib\filetransfer.jar;C:\jsystem\runner\lib\j2autoit.jar;C:\jsystem\runner\lib\jsystem-launcher.jar;C:\jsystem\runner\lib\jsystemAgent.jar;C:\jsystem\runner\lib\jsystemApp.jar;C:\jsystem\runner\lib\jsystemCommon.jar;C:\jsystem\runner\lib\jsystemCore.jar;C:\jsystem\runner\lib\snmp.jar;C:\jsystem\runner\lib\stations.jar;C:\jsystem\runner\lib\swing.jar;C:\jsystem\runner\lib\tcl.jar;C:\jsystem\runner\lib\vbshell.jar;C:\jsystem\runner\lib\web.jar;C:\jsystem\runner\lib\wget.jar; C:\jsystem\runner\lib\xmlrpc-client-3.1.3.jar; C:\jsystem\runner\lib\xmlrpc-common-3.1.3.jar; C:\jsystem\runner\lib\xmlrpc-server-3.1.3.jar; C:\jsystem\runner\lib\j2autoit\j2autoit.jar C:\jsystem\runner Setting J2AutoIt Agent to use the port: 8888 Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/xmlrpc/WebServer at com.jsystem.j2autoit.AutoItAgent.startAutoItWebServer(AutoItAgent.java:665) at com.jsystem.j2autoit.AutoItAgent.main(AutoItAgent.java:348) Caused by: java.lang.ClassNotFoundException: org.apache.xmlrpc.WebServer at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClassInternal(Unknown Source) ... 2 more

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  • Java Applet in Firefox

    - by prakash
    Hi All, I am facing a weird problem in Testing server while using applet (using embed tag) in my ASP.NET MVC application Applet works fine locally in both browsers IE and Firefox but when deployed to Testing server its throwing below exception for Firefox only (IE works fine). Please help me out in this basic: exception: javax.xml.parsers.FactoryConfigurationError: Provider <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> not found. java.lang.RuntimeException: javax.xml.parsers.FactoryConfigurationError: Provider <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> not found at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source) at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source) at java.lang.Thread.run(Unknown Source) Caused by: javax.xml.parsers.FactoryConfigurationError: Provider <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> not found at javax.xml.parsers.DocumentBuilderFactory.newInstance(Unknown Source) at org.apache.log4j.xml.DOMConfigurator.doConfigure(DOMConfigurator.java:772) at org.apache.log4j.xml.DOMConfigurator.doConfigure(DOMConfigurator.java:696) at org.apache.log4j.helpers.OptionConverter.selectAndConfigure(OptionConverter.java:471) at org.apache.log4j.LogManager.<clinit>(LogManager.java:125) at org.apache.log4j.Logger.getLogger(Logger.java:105) at com.goldleaf.scanner.Logger.<init>(Unknown Source) at com.goldleaf.scanner.Logger.<init>(Unknown Source) at com.goldleaf.scanner.Logger$LoggerHolder.<clinit>(Unknown Source) at com.goldleaf.scanner.Logger.getInstance(Unknown Source) at com.goldleaf.scanner.ScannerApplet.<init>(Unknown Source) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) at java.lang.reflect.Constructor.newInstance(Unknown Source) at java.lang.Class.newInstance0(Unknown Source) at java.lang.Class.newInstance(Unknown Source) at sun.plugin2.applet.Plugin2Manager$12.run(Unknown Source) at java.awt.event.InvocationEvent.dispatch(Unknown Source) at java.awt.EventQueue.dispatchEvent(Unknown Source) at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.run(Unknown Source) Exception: java.lang.RuntimeException: javax.xml.parsers.FactoryConfigurationError: Provider <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> not found Ignored exception: java.lang.RuntimeException: javax.xml.parsers.FactoryConfigurationError: Provider <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> not found basic: Starting applet teardown basic: Finished applet teardown

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  • Use of Java constructors in persistent entities

    - by Mr Morgan
    Hello I'm new to JPA and using persistence in Java anyway and I have two questions I can't quite work out: I have generated tags as: @JoinColumn(name = "UserName", referencedColumnName = "UserName") @ManyToOne(optional = false) private User userName; @JoinColumn(name = "DatasetNo", referencedColumnName = "DatasetNo") @ManyToOne(optional = false) private Dataset datasetNo; But in one of the constructors for the class, no reference is made to columns UserName or DatasetNo whereas all other columns in the class are referenced in the constructor. Can anyone tell me why this is? Both columns UserName and DatasetNo are 'foreign keys' on the entity Visualisation which corresponds to a database table of the same name. I can't quite work out the ORM. And when using entity classes, or POJO, is it better to have class variables like: private User userName; Where an instance of a class is specified or simply the key of that class instance like: private String userName; Thanks Mr Morgan.

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  • Exception in thread "main" java.lang.StackOverflowError

    - by Ray.R.Chua
    I have a piece of code and I could not figure out why it is giving me Exception in thread "main" java.lang.StackOverflowError. This is the question: Given a positive integer n, prints out the sum of the lengths of the Syracuse sequence starting in the range of 1 to n inclusive. So, for example, the call: lengths(3) will return the the combined length of the sequences: 1 2 1 3 10 5 16 8 4 2 1 which is the value: 11. lengths must throw an IllegalArgumentException if its input value is less than one. My Code: import java.util.HashMap; public class Test { HashMap<Integer,Integer> syraSumHashTable = new HashMap<Integer,Integer>(); public Test(){ } public int lengths(int n)throws IllegalArgumentException{ int sum =0; if(n < 1){ throw new IllegalArgumentException("Error!! Invalid Input!"); } else{ for(int i =1; i<=n;i++){ if(syraSumHashTable.get(i)==null) { syraSumHashTable.put(i, printSyra(i,1)); sum += (Integer)syraSumHashTable.get(i); } else{ sum += (Integer)syraSumHashTable.get(i); } } return sum; } } private int printSyra(int num, int count){ int n = num; if(n == 1){ return count; } else{ if(n%2==0){ return printSyra(n/2, ++count); } else{ return printSyra((n*3)+1, ++count) ; } } } } Driver code: public static void main(String[] args) { // TODO Auto-generated method stub Test s1 = new Test(); System.out.println(s1.lengths(90090249)); //System.out.println(s1.lengths(5)); } . I know the problem lies with the recursion. The error does not occur if the input is a small value, example: 5. But when the number is huge, like 90090249, I got the Exception in thread "main" java.lang.StackOverflowError. Thanks all for your help. :) I almost forgot the error msg: Exception in thread "main" java.lang.StackOverflowError at Test.printSyra(Test.java:60) at Test.printSyra(Test.java:65) at Test.printSyra(Test.java:60) at Test.printSyra(Test.java:65) at Test.printSyra(Test.java:60) at Test.printSyra(Test.java:60) at Test.printSyra(Test.java:60) at Test.printSyra(Test.java:60)

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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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  • Help naming a class that has a single public method called Execute()

    - by devoured elysium
    I have designed the following class that should work kind of like a method (usually the user will just run Execute()): public abstract class ??? { protected bool hasFailed = false; protected bool hasRun = false; public bool HasFailed { get { return hasFailed; } } public bool HasRun { get { return hasRun; } } private void Restart() { hasFailed = false; hasRun = false; } public bool Execute() { ExecuteImplementation(); bool returnValue = hasFailed; Restart(); return returnValue; } protected abstract void ExecuteImplementation(); } My question is: how should I name this class? Runnable? Method(sounds awkward)?

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  • Java Play Mustache NPE Error

    - by zanedev
    We are getting a mustache play error in production (amazon linux EC2 AMI) but not in development (MACs) and we have tried upgrading the jvm, using the jdk instead, and changing from a tomcat deploy model to match our development environments as much as possible but nothing is working. Please any help would be greatly appreciated. We have lots of shared code in java and javascript using mustache and it would be a big deal to rewrite everything if we had to ditch mustache on the java side. 20:48:52,403 ERROR ~ @6al2dd0po Internal Server Error (500) for request GET /mystuff/people Execution exception (In {module:mustache-0.2}/app/play/modules/mustache/MustacheTags.java around line 32) NullPointerException occured : null play.exceptions.JavaExecutionException at play.templates.BaseTemplate.throwException(BaseTemplate.java:90) at play.templates.GroovyTemplate.internalRender(GroovyTemplate.java:257) at play.templates.Template.render(Template.java:26) at play.templates.GroovyTemplate.render(GroovyTemplate.java:187) at play.mvc.results.RenderTemplate.<init>(RenderTemplate.java:24) at play.mvc.Controller.renderTemplate(Controller.java:660) at play.mvc.Controller.renderTemplate(Controller.java:640) at play.mvc.Controller.render(Controller.java:695) at controllers.MyStuff.people(MyStuff.java:183) at play.mvc.ActionInvoker.invokeWithContinuation(ActionInvoker.java:548) at play.mvc.ActionInvoker.invoke(ActionInvoker.java:502) at play.mvc.ActionInvoker.invokeControllerMethod(ActionInvoker.java:478) at play.mvc.ActionInvoker.invokeControllerMethod(ActionInvoker.java:473) at play.mvc.ActionInvoker.invoke(ActionInvoker.java:161) at Invocation.HTTP Request(Play!) Caused by: java.lang.NullPointerException at play.modules.mustache.MustacheTags._template(MustacheTags.java:32) at play.modules.mustache.MustacheTags$_template.call(Unknown Source) at /app/views/User/people.html.(line:22) at play.templates.GroovyTemplate.internalRender(GroovyTemplate.java:232) ... 13 more

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  • generating class from hibernate mapping file

    - by Mrityunjay
    hi, i have one mapping file viz. student.hbm.xml.. i need to generate Student.java from the same. the file is below :- <?xml version="1.0" encoding="UTF-8"?> <hibernate-mapping> <class name="org.hibernate.entity.ClassRoom" table="class_room"> <id name="roomId" column="room_id" type="int"/> <property name="roomClass" column="room_class" type="string"/> <property name="floor" column="floor" type="int"/> <property name="roomMaster" column="room_mast" type="string"/> </class> </hibernate-mapping> is there any way i can create the class file from the above file.please help...

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  • C++: Create abstract class with abstract method and override the method in a subclass

    - by Martijn Courteaux
    Hi, How to create in C++ an abstract class with some abstract methods that I want to override in a subclass? How should the .h file look? Is there a .cpp, if so how should it look? In Java it would look like this: abstract class GameObject { public abstract void update(); public abstract void paint(Graphics g); } class Player extends GameObject { @Override public void update() { // ... } @Override public void paint(Graphics g) { // ... } } // In my game loop: for (int i = 0; i < objects.size(); i++) { objects.get(i).update(); } for (int i = 0; i < objects.size(); i++) { objects.get(i).paint(g); } Translating this code to C++ is enough for me.

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  • java.lang.ClassNotFoundException: com.mysql.jdbc.Driver When run jar file

    - by user1024858
    Hi all, Connection conn = null; String url = "jdbc:mysql://localhost:3306/"; String dbName = "test"; String driver = "com.mysql.jdbc.Driver"; String userName = "root"; String password = "admin"; try { Class.forName(driver).newInstance(); conn = DriverManager.getConnection(url+dbName,userName,password); System.out.println("Connected to the database"); conn.close(); System.out.println("Disconnected from database"); } catch (Exception e) { e.printStackTrace();} I run in eclipse it's ok, but i built to jar file and run on command line java -jar Test.jar i get this error: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver at java.net.URLClassLoader$1.run(Unknown Source) at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Unknown Source) Please help me how to fix it. Thanks!!!

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  • Java : Using parent class method to access child class variable

    - by Jayant
    I have the following scenario : public class A { private int x = 5; public void print() { System.out.println(x); } } public class B extends A { private int x = 10; /*public void print() { System.out.println(x); }*/ public static void main(String[] args) { B b = new B(); b.print(); } } On executing the code, the output is : 5. How to access the child class(B's) variable(x) via the parent class method? Could this be done without overriding the print() method (i.e. uncommenting it in B)? [This is important because on overriding we will have to rewrite the whole code for the print() method again]

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  • base class , inheritate class sizeof()

    - by user1279988
    why sizeof(X) is 4 and sizeof(Y) is 8? and another question, in class X, only the int(i) count as sizeof() 4? member function does take any memory space? Plz tell me, thanks! class X { int i; public: X() { i = 0; } void set(int ii) { i = ii; } int read() const { return i; } int permute() { return i = i * 47; } }; class Y : public X { int i; // Different from X's i public: Y() { i = 0; } int change() { i = permute(); // Different name call return i; } void set(int ii) { i = ii; X::set(ii); // Same-name function call } }; cout << "sizeof(X) = " << sizeof(X) << endl; cout << "sizeof(Y) = "

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  • Why is Java .Net so slow? [closed]

    - by 0101
    Ive just tried to use atmosphere.java.net (to see what it is) and I am not able to do it. Why is Java .NET so slow? Is it because they used Java in the server and are as incompetent as people whom write questions for SCJP? Does Sun have any competent employee and have you ever saw one ? (except the guy from Java Puzzles who made a career, because he made a lot of mistakes in Java API and now can teach us about it.) P.S. I would make it the "community wiki" if I could(to not get massive down-votes) but its not possible here, so hit me if you want to.

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  • Why is Python slower than Java but faster than PHP

    - by good_computer
    I have many times seen various benchmarks that show how a bunch of languages perform on a given task. Always these benchmarks reveal that Python is slower then Java and faster than PHP. And I wonder why is that the case. Java, Python, and PHP run inside a virtual machine All three languages convert their programs into their custom byte codes that run on top of OS -- so none is running natively Both Java and Python can be "complied" (.pyc for Python) but the __main__ module for Python is not compiled Python and PHP are dynamically typed and Java statically -- is this the reason Java is faster, and if so, please explain how that affects speed. And, even if the dynamic-vs-static argument is correct, this does not explain why PHP is slower than Python -- because both are dynamic languages. You can see some benchmarks here and here, and here

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  • Value of the HTML5 lang attribute

    - by user359650
    I'm working on a website which will offer localized content following the language+region approach as described on this W3.org page (e.g. fr-CA for Canadian French content, and fr-FR for "French French" content). As we consider content for each language+region to be unique, it is crucial to us that search engines properly identify and serve the content accordingly. By looking up on the Internet (e.g. this question), it appears that most people recommend the use of an ISO639 language code in the HTML lang attribute to describe the content language. Following this recommendation, we would en up using <html lang="fr"> which wouldn't enable the differentiation between the aforementioned language+region combinations. When reviewing the HTML4 specification, it seems that using language+region as a language code would be perfectly OK, as the en-US example is given as one possible value. However I couldn't find any confirmation of this in the HTML5 specification which doesn't seem to provide any example as to the possible allowed values. From there I tried to get a de facto answer by looking at what the web giants are doing. I looked at what Facebook are doing: they offer Candian French and French French versions of their websites with (slightly) different content, whilst the HTML lang value remains the same: fr-CA URL: http://fr-ca.facebook.com HTML lang attribute: <html lang="fr"> translation of the word 'email': courriel fr-FR URL: http://fr-fr.facebook.com/ HTML lang attribute: <html lang="fr"> translation of the word 'email': Adresse électronique Q: What is the recommended/standard way of describing content that was localized using the language+region approach in HTML5 ?

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  • JavaOne 2012 - Java Deployment on Mac OS X

    - by Sharon Zakhour
    Also at the JavaOne 2012 conference, Scott Kovatch presented a session on Deploying Your Application with OpenJDK 7 on Mac OS X. The session had special emphasis on how to deploy Java applications to the Mac App Store and discussed topics relevant to using Oracle Java on the Mac. Interested developers may find the following documentation useful: Packaging a Java App for Distribution on a Mac. For more information on installing and using Oracle Java for the Mac, refer to the following documentation: Mac FAQ JDK 7 Installation for Mac OS X JRE 7 Installation for Mac OS X Mac OS X Platform Install FAQ Note for Users of Macs that Include Apple Java 6

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  • Goto for the Java Programming Language

    - by darcy
    Work on JDK 8 is well-underway, but we thought this late-breaking JEP for another language change for the platform couldn't wait another day before being published. Title: Goto for the Java Programming Language Author: Joseph D. Darcy Organization: Oracle. Created: 2012/04/01 Type: Feature State: Funded Exposure: Open Component: core/lang Scope: SE JSR: 901 MR Discussion: compiler dash dev at openjdk dot java dot net Start: 2012/Q2 Effort: XS Duration: S Template: 1.0 Reviewed-by: Duke Endorsed-by: Edsger Dijkstra Funded-by: Blue Sun Corporation Summary Provide the benefits of the time-testing goto control structure to Java programs. The Java language has a history of adding new control structures over time, the assert statement in 1.4, the enhanced for-loop in 1.5,and try-with-resources in 7. Having support for goto is long-overdue and simple to implement since the JVM already has goto instructions. Success Metrics The goto statement will allow inefficient and verbose recursive algorithms and explicit loops to be replaced with more compact code. The effort will be a success if at least twenty five percent of the JDK's explicit loops are replaced with goto's. Coordination with IDE vendors is expected to help facilitate this goal. Motivation The goto construct offers numerous benefits to the Java platform, from increased expressiveness, to more compact code, to providing new programming paradigms to appeal to a broader demographic. In JDK 8, there is a renewed focus on using the Java platform on embedded devices with more modest resources than desktop or server environments. In such contexts, static and dynamic memory footprint is a concern. One significant component of footprint is the code attribute of class files and certain classes of important algorithms can be expressed more compactly using goto than using other constructs, saving footprint. For example, to implement state machines recursively, some parties have asked for the JVM to support tail calls, that is, to perform a complex transformation with security implications to turn a method call into a goto. Such complicated machinery should not be assumed for an embedded context. A better solution is just to expose to the programmer the desired functionality, goto. The web has familiarized users with a model of traversing links among different HTML pages in a free-form fashion with some state being maintained on the side, such as login credentials, to effect behavior. This is exactly the programming model of goto and code. While in the past this has been derided as leading to "spaghetti code," spaghetti is a tasty and nutritious meal for programmers, unlike quiche. The invokedynamic instruction added by JSR 292 exposes the JVM's linkage operation to programmers. This is a low-level operation that can be leveraged by sophisticated programmers. Likewise, goto is a also a low-level operation that should not be hidden from programmers who can use more efficient idioms. Some may object that goto was consciously excluded from the original design of Java as one of the removed feature from C and C++. However, the designers of the Java programming languages have revisited these removals before. The enum construct was also left out only to be added in JDK 5 and multiple inheritance was left out, only to be added back by the virtual extension method methods of Project Lambda. As a living language, the needs of the growing Java community today should be used to judge what features are needed in the platform tomorrow; the language should not be forever bound by the decisions of the past. Description From its initial version, the JVM has had two instructions for unconditional transfer of control within a method, goto (0xa7) and goto_w (0xc8). The goto_w instruction is used for larger jumps. All versions of the Java language have supported labeled statements; however, only the break and continue statements were able to specify a particular label as a target with the onerous restriction that the label must be lexically enclosing. The grammar addition for the goto statement is: GotoStatement: goto Identifier ; The new goto statement similar to break except that the target label can be anywhere inside the method and the identifier is mandatory. The compiler simply translates the goto statement into one of the JVM goto instructions targeting the right offset in the method. Therefore, adding the goto statement to the platform is only a small effort since existing compiler and JVM functionality is reused. Other language changes to support goto include obvious updates to definite assignment analysis, reachability analysis, and exception analysis. Possible future extensions include a computed goto as found in gcc, which would replace the identifier in the goto statement with an expression having the type of a label. Testing Since goto will be implemented using largely existing facilities, only light levels of testing are needed. Impact Compatibility: Since goto is already a keyword, there are no source compatibility implications. Performance/scalability: Performance will improve with more compact code. JVMs already need to handle irreducible flow graphs since goto is a VM instruction.

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