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• Schema to support dynamic properties

  - by Johan Fredrik Varen

  Hi people. I'm working on an editor that enables its users to create "object" definitions in real-time. A definition can contain zero or more properties. A property has a name a type. Once a definition is created, a user can create an object of that definition and set the property values of that object. So by the click of a mouse-button, the user should ie. be able to create a new definition called "Bicycle", and add the property "Size" of type "Numeric". Then another property called "Name" of type "Text", and then another property called "Price" of type "Numeric". Once that is done, the user should be able to create a couple of "Bicycle" objects and fill in the "Name" and "Price" property values of each bike. Now, I've seen this feature in several software products, so it must be a well-known concept. My problem started when I sat down and tried to come up with a DB schema to support this data structure, because I want the property values to be stored using the appropriate column types. Ie. a numeric property value is stored as, say, an INT in the database, and a textual property value is stored as VARCHAR. First, I need a table that will hold all my object definitions: Table obj_defs id | name | ---------------- 1 | "Bicycle" | 2 | "Book" | Then I need a table for holding what sort of properties each object definition should have: Table prop_defs id | obj_def_id | name | type | ------------------------------------ 1 | 1 | "Size" | ? | 2 | 1 | "Name" | ? | 3 | 1 | "Price" | ? | 4 | 2 | "Title" | ? | 5 | 2 | "Author" | ? | 6 | 2 | "ISBN" | ? | I would also need a table that holds each object: Table objects id | created | updated | ------------------------------ 1 | 2011-05-14 | 2011-06-15 | 2 | 2011-05-14 | 2011-06-15 | 3 | 2011-05-14 | 2011-06-15 | Finally, I need a table that will hold the actual property values of each object, and one solution is for this table to have one column for each possible value type, such as this: Table prop_vals id | prop_def_id | object_id | numeric | textual | boolean | ------------------------------------------------------------ 1 | 1 | 1 | 27 | | | 2 | 2 | 1 | | "Trek" | | 3 | 3 | 1 | 1249 | | | 4 | 1 | 2 | 26 | | | 5 | 2 | 2 | | "GT" | | 6 | 3 | 2 | 159 | | | 7 | 4 | 3 | | "It" | | 8 | 5 | 3 | | "King" | | 9 | 6 | 4 | 9 | | | If I implemented this schema, what would the "type" column of the prop_defs table hold? Integers that each map to a column name, varchars that simply hold the column name? Any other possibilities? Would a stored procedure help me out here in some way? And what would the SQL for fetching the "name" property of object 2 look like?

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• Multi-threaded Pooled Allocators

  - by Darren Engwirda

  I'm having some issues using pooled memory allocators for std::list objects in a multi-threaded application. The part of the code I'm concerned with runs each thread function in isolation (i.e. there is no communication or synchronization between threads) and therefore I'd like to setup separate memory pools for each thread, where each pool is not thread-safe (and hence fast). I've tried using a shared thread-safe singleton memory pool and found the performance to be poor, as expected. This is a heavily simplified version of the type of thing I'm trying to do. A lot has been included in a pseudo-code kind of way, sorry if it's confusing. /* The thread functor - one instance of MAKE_QUADTREE created for each thread */ class make_quadtree { private: /* A non-thread-safe memory pool for int linked list items, let's say that it's * something along the lines of BOOST::OBJECT_POOL */ pooled_allocator<int> item_pool; /* The problem! - a local class that would be constructed within each std::list as the * allocator but really just delegates to ITEM_POOL */ class local_alloc { public : //!! I understand that I can't access ITEM_POOL from within a nested class like //!! this, that's really my question - can I get something along these lines to //!! work?? pointer allocate (size_t n) { return ( item_pool.allocate(n) ); } }; public : make_quadtree (): item_pool() // only construct 1 instance of ITEM_POOL per // MAKE_QUADTREE object { /* The kind of data structures - vectors of linked lists * The idea is that all of the linked lists should share a local pooled allocator */ std::vector<std::list<int, local_alloc>> lists; /* The actual operations - too complicated to show, but in general: * * - The vector LISTS is grown as a quadtree is built, it's size is the number of * quadtree "boxes" * * - Each element of LISTS (each linked list) represents the ID's of items * contained within each quadtree box (say they're xy points), as the quadtree * is grown a lot of ID pop/push-ing between lists occurs, hence the memory pool * is important for performance */ } }; So really my problem is that I'd like to have one memory pool instance per thread functor instance, but within each thread functor share the pool between multiple std::list objects.

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• Mock Object and Interface

  - by tunl

  I'm a newbie in Unit Test with Mock Object. I use EasyMock. I try to understand this example: import java.io.IOException; public interface ExchangeRate { double getRate(String inputCurrency, String outputCurrency) throws IOException; } import java.io.IOException; public class Currency { private String units; private long amount; private int cents; public Currency(double amount, String code) { this.units = code; setAmount(amount); } private void setAmount(double amount) { this.amount = new Double(amount).longValue(); this.cents = (int) ((amount * 100.0) % 100); } public Currency toEuros(ExchangeRate converter) { if ("EUR".equals(units)) return this; else { double input = amount + cents/100.0; double rate; try { rate = converter.getRate(units, "EUR"); double output = input * rate; return new Currency(output, "EUR"); } catch (IOException ex) { return null; } } } public boolean equals(Object o) { if (o instanceof Currency) { Currency other = (Currency) o; return this.units.equals(other.units) && this.amount == other.amount && this.cents == other.cents; } return false; } public String toString() { return amount + "." + Math.abs(cents) + " " + units; } } import junit.framework.TestCase; import org.easymock.EasyMock; import java.io.IOException; public class CurrencyTest extends TestCase { public void testToEuros() throws IOException { Currency testObject = new Currency(2.50, "USD"); Currency expected = new Currency(3.75, "EUR"); ExchangeRate mock = EasyMock.createMock(ExchangeRate.class); EasyMock.expect(mock.getRate("USD", "EUR")).andReturn(1.5); EasyMock.replay(mock); Currency actual = testObject.toEuros(mock); assertEquals(expected, actual); } } So, i wonder how to Currency use ExchangeRate in toEuros(..) method. rate = converter.getRate(units, "EUR"); The behavior of getRate(..) method is not specified because ExchangeRate is an interface.

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• User Defined Exceptions with JMX

  - by Daniel

  I have exposed methods for remote management in my application server using JMX by creating an MXBean interface, and a class to implement it. Included in this interface are operations for setting attributes on my server, and for getting the current value of attributes. For example, take the following methods: public interface WordManagerMXBean { public void addWord(String word); public WordsObject getWords(); public void removeWord(String word); } The WordsObject is a custom, serializable class used to retrieve data about the state of the server. Then I also have a WordManager class that implements the above interface. I then create a JMX agent to manage my resource: MBeanServer mbs = ManagementFactory.getPlatformMBeanServer(); ObjectName wordManagerName = new ObjectName("com.example:type=WordManager"); mbs.registerMBean(wordManager, wordManagerName); I have created a client that invokes these methods, and this works as expected. However, I would like to extend this current configuration by adding user defined exceptions that can be sent back to my client. So I would like to change my interface to something like this: public interface WordManagerMXBean { public void addWord(String word) throws WordAlreadyExistsException; public WordsObject getWords(); public void removeWord(String word); } My WordAlreadyExistsException looks like this: public class WordAlreadyExistsException extends Exception implements Serializable { private static final long serialVersionUID = -9095552123119275304L; public WordAlreadyExistsException() { super(); } } When I call the addWord() method in my client, I would like to get back a WordAlreadyExistsException if the word already exists. However, when I do this, I get an error like this: java.rmi.UnmarshalException: Error unmarshaling return; nested exception is: java.lang.ClassNotFoundException: com.example.WordAlreadyExistsException The WordAlreadyExistsException, the WordsObject and the WordManagerMXBean interface are all in a single jar file that is available to both the client and the server. If I call the getWords() method, the client has no difficulty handling the WordsObject. However, if a user defined exception, like the one above, is thrown, then the client gives the error shown above. Is it possible to configure JMX to handle this exception correctly in the client? Following some searching, I noticed that there is an MBeanException class that is used to wrap exceptions. I'm not sure if this wrapping is performed by the agent automatically, or if I'm supposed to do the wrapping myself. I tried both, but in either case I get the same error on the client. I have also tried this with both checked and unchecked exceptions, again the same error occurs. One solution to this is to simply pass back the error string inside a generic error, as all of the standard java exceptions work. But I'd prefer to get back the actual exception for processing by the client. Is it possible to handle user defined exceptions in JMX? If so, any ideas how?

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• Question about InputMismatchException while using Scanner

  - by aser

  The question : Input file: customer’s account number, account balance at beginning of month, transaction type (withdrawal, deposit, interest), transaction amount Output: account number, beginning balance, ending balance, total interest paid, total amount deposited, number of deposits, total amount withdrawn, number of withdrawals package sentinel; import java.io.*; import java.util.*; public class Ex7 { /** * @param args the command line arguments */ public static void main(String[] args) throws FileNotFoundException { int AccountNum; double BeginningBalance; double TransactionAmount; int TransactionType; double AmountDeposited=0; int NumberOfDeposits=0; double InterestPaid=0.0; double AmountWithdrawn=0.0; int NumberOfWithdrawals=0; boolean found= false; Scanner inFile = new Scanner(new FileReader("Account.in")); PrintWriter outFile = new PrintWriter("Account.out"); AccountNum = inFile.nextInt(); BeginningBalance= inFile.nextDouble(); while (inFile.hasNext()) { TransactionAmount=inFile.nextDouble(); TransactionType=inFile.nextInt(); outFile.printf("Account Number: %d%n", AccountNum); outFile.printf("Beginning Balance: $%.2f %n",BeginningBalance); outFile.printf("Ending Balance: $%.2f %n",BeginningBalance); outFile.println(); switch (TransactionType) { case '1': // case 1 if we have a Deposite BeginningBalance = BeginningBalance + TransactionAmount; AmountDeposited = AmountDeposited + TransactionAmount; NumberOfDeposits++; outFile.printf("Amount Deposited: $%.2f %n",AmountDeposited); outFile.printf("Number of Deposits: %d%n",NumberOfDeposits); outFile.println(); break; case '2':// case 2 if we have an Interest BeginningBalance = BeginningBalance + TransactionAmount; InterestPaid = InterestPaid + TransactionAmount; outFile.printf("Interest Paid: $%.2f %n",InterestPaid); outFile.println(); break; case '3':// case 3 if we have a Withdraw BeginningBalance = BeginningBalance - TransactionAmount; AmountWithdrawn = AmountWithdrawn + TransactionAmount; NumberOfWithdrawals++; outFile.printf("Amount Withdrawn: $%.2f %n",AmountWithdrawn); outFile.printf("Number of Withdrawals: %d%n",NumberOfWithdrawals); outFile.println(); break; default: System.out.println("Invalid transaction Tybe: " + TransactionType + TransactionAmount); } } inFile.close(); outFile.close(); } } But is gives me this : Exception in thread "main" java.util.InputMismatchException at java.util.Scanner.throwFor(Scanner.java:840) at java.util.Scanner.next(Scanner.java:1461) at java.util.Scanner.nextInt(Scanner.java:2091) at java.util.Scanner.nextInt(Scanner.java:2050) at sentinel.Ex7.main(Ex7.java:36) Java Result: 1

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• Issue accessing class variable from thread.

  - by James

  Hello, The code below is meant to take an arraylist of product objects as an input, spun thread for each product(and add the product to the arraylist 'products'), check product image(product.imageURL) availability, remove the products without images(remove the product from the arraylist 'products'), and return an arraylist of products with image available. package com.catgen.thread; import java.util.ArrayList; import java.util.Iterator; import java.util.List; import com.catgen.Product; import com.catgen.Utils; public class ProductFilterThread extends Thread{ private Product product; private List<Product> products = new ArrayList<Product>(); public ProductFilterThread(){ } public ProductFilterThread(Product product){ this.product = product; } public synchronized void addProduct(Product product){ System.out.println("Before add: "+getProducts().size()); getProducts().add(product); System.out.println("After add: "+getProducts().size()); } public synchronized void removeProduct(Product product){ System.out.println("Before rem: "+getProducts().size()); getProducts().remove(product); System.out.println("After rem: "+getProducts().size()); } public synchronized List<Product> getProducts(){ return this.products; } public synchronized void setProducts(List<Product> products){ this.products = products; } public void run(){ boolean imageExists = Utils.fileExists(this.product.ImageURL); if(!imageExists){ System.out.println(this.product.ImageURL); removeProduct(this.product); } } public List<Product> getProductsWithImageOnly(List<Product> products){ ProductFilterThread pft = null; try{ List<ProductFilterThread> threads = new ArrayList<ProductFilterThread>(); for(Product product: products){ pft = new ProductFilterThread(product); addProduct(product); pft.start(); threads.add(pft); } Iterator<ProductFilterThread> threadsIter = threads.iterator(); while(threadsIter.hasNext()){ ProductFilterThread thread = threadsIter.next(); thread.join(); } }catch(Exception e){ e.printStackTrace(); } System.out.println("Total returned products = "+getProducts().size()); return getProducts(); } } Calling statement: displayProducts = new ProductFilterThread().getProductsWithImageOnly(displayProducts); Here, when addProduct(product) is called from within getProductsWithImageOnly(), getProducts() returns the list of products, but that's not the case(no products are returned) when the method removeProduct() is called by a thread, because of which the products without images are never removed. As a result, all the products are returned by the module whether or not the contained products have images. What can be the problem here? Thanks in advance. James.

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• Hibernate MappingException Unknown entity: $Proxy2

  - by slynn1324

  I'm using Hibernate annotations and have a VERY basic data object: import java.io.Serializable; import javax.persistence.Entity; import javax.persistence.Id; @Entity public class State implements Serializable { /** * */ private static final long serialVersionUID = 1L; @Id private String stateCode; private String stateFullName; public String getStateCode() { return stateCode; } public void setStateCode(String stateCode) { this.stateCode = stateCode; } public String getStateFullName() { return stateFullName; } public void setStateFullName(String stateFullName) { this.stateFullName = stateFullName; } } and am trying to run the following test case: public void testCreateState(){ Session s = HibernateUtil.getSessionFactory().getCurrentSession(); Transaction t = s.beginTransaction(); State state = new State(); state.setStateCode("NE"); state.setStateFullName("Nebraska"); s.save(s); t.commit(); } and get an org.hibernate.MappingException: Unknown entity: $Proxy2 at org.hibernate.impl.SessionFactoryImpl.getEntityPersister(SessionFactoryImpl.java:628) at org.hibernate.impl.SessionImpl.getEntityPersister(SessionImpl.java:1366) at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:121) .... I haven't been able to find anything referencing the $Proxy part of the error - and am at a loss.. Any pointers to what I'm missing would be greatly appreciated. hibernate.cfg.xml <property name="hibernate.connection.driver_class">org.hsqldb.jdbcDriver</property> <property name="connection.url">jdbc:hsqldb:hsql://localhost/xdb</property> <property name="connection.username">sa</property> <property name="connection.password"></property> <property name="current_session_context_class">thread</property> <property name="dialect">org.hibernate.dialect.HSQLDialect</property> <property name="show_sql">true</property> <property name="hbm2ddl.auto">update</property> <property name="hibernate.transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property> <mapping class="com.test.domain.State"/> in HibernateUtil.java public static SessionFactory getSessionFactory(boolean testing ) { if ( sessionFactory == null ){ try { String configPath = HIBERNATE_CFG; AnnotationConfiguration config = new AnnotationConfiguration(); config.configure(configPath); sessionFactory = config.buildSessionFactory(); } catch (Exception e){ e.printStackTrace(); throw new ExceptionInInitializerError(e); } } return sessionFactory; }

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• How do you return a pointer to a base class with a virtual function?

  - by Nick Sweet

  I have a base class called Element, a derived class called Vector, and I'm trying to redefine two virtual functions from Element in Vector. //element.h template <class T> class Element { public: Element(); virtual Element& plus(const Element&); virtual Element& minus(const Element&); }; and in another file //Vector.h #include "Element.h" template <class T> class Vector: public Element<T> { T x, y, z; public: //constructors Vector(); Vector(const T& x, const T& y = 0, const T& z =0); Vector(const Vector& u); ... //operations Element<T>& plus(const Element<T>& v) const; Element<T>& minus(const Element<T>& v) const; ... }; //sum template <class T> Element<T>& Vector<T>::plus(const Element<T>& v) const { Element<T>* ret = new Vector((x + v.x), (y + v.y), (z + v.z)); return *ret; } //difference template <class T> Element<T>& Vector<T>::minus(const Element<T>& v) const { Vector<T>* ret = new Vector((x - v.x), (y - v.y), (z - v.z)); return *ret; } but I always get error: 'const class Element' has no member named 'getx' So, can I define my virtual functions to take Vector& as an argument instead, or is there a way for me to access the data members of Vector through a pointer to Element? I'm still fairly new to inheritance polymorphism, fyi.

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• Deserialization error in a new environment

  - by cerhart

  I have a web application that calls a third-party web service. When I run it locally, I have no problems, but when I move it to my production environment, I get the following error: There is an error in XML document (2, 428). Stack: at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle, XmlDeserializationEvents events) at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle) at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall) at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters) at RMXClasses.RMXContactService.ContactService.getActiveSessions(String user, String pass) in C:\Users\hp\Documents\Visual Studio 2008\Projects\ReklamStore\RMXClasses\Web References\RMXContactService\Reference.cs:line 257 at I have used the same web config file from the production environment but it still works locally. My local machine is a running vista home edition and the production environment is windows server 2003. The application is written in asp.net 3.5, wierdly under the asp.net config tab in iis, 3.5 doesn't show up in the drop down list, although that version of the framework is installed. The error is not being thrown in my code, it happens during serialization. I called the method on the proxy, I have checked the arguments and they are OK. I have also logged the SOAP request and response, and they both look OK as well. I am really at a loss here. Any ideas? SOAP log: This is the soap response that the program seems to have trouble parsing only on server 2003. On my machine the soap is identical, and yet it parses with no problems. SoapResponse BeforeDeserialize; <?xml version="1.0" encoding="UTF-8"?> <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="urn:ContactService" xmlns:ns2="http://api.yieldmanager.com/types" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"><SOAP-ENV:Body><ns1:getActiveSessionsResponse> <sessions SOAP-ENC:arrayType="ns2:session[1]" xsi:type="ns2:array_of_session"> <item xsi:type="ns2:session"> <token xsi:type="xsd:string">xxxxxxxxxxxxxxxxxxxx1ae12517584b</token> <creation_time xsi:type="xsd:dateTime">2009-09-25T05:51:19Z</creation_time> <modification_time xsi:type="xsd:dateTime">2009-09-25T05:51:19Z</modification_time> <ip_address xsi:type="xsd:string">xxxxxxxxxx</ip_address> <contact_id xsi:type="xsd:long">xxxxxx</contact_id></item></sessions> </ns1:getActiveSessionsResponse></SOAP-ENV:Body></SOAP-ENV:Envelope>

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• How to return a property name when comparing two properties at class-level

  - by CodeMonkey

  Hi I have implemented an 'EqualTo' Validation Attribute, that compares two Properties of an object, during ModelBinding in ASP.NET MVC 2. The problem I have is not with it not working, because it does work. The problem is, when I do my request - which is an ajax request - I get back errors to my front-end, where it sets a class on the input fields to indicate invalid input. What it does is iterate through a list of Errors (in a JsonResult), and set a class. This is all dandy. But the ValidationAtrribute I am having trouble with is set at a Class-level, i.e., it's not like other ValidationAttributes where you set something like "[Required]" or something like that. [AttributeUsage(AttributeTargets.Class, AllowMultiple=true, Inherited=false)] public class EqualToAttribute : ValidationAttribute { public String SourceProperty { get; set; } public String MatchProperty { get; set; } public EqualToAttribute(string source, string match) { SourceProperty = source; MatchProperty = match; } public override Boolean IsValid(Object value) { Type objectType = value.GetType(); PropertyInfo[] properties = objectType.GetProperties(); object sourceValue = new object(); object matchValue = new object(); Type sourceType = null; Type matchType = null; int counter = 0; foreach (PropertyInfo propertyInfo in properties) { if (propertyInfo.Name == SourceProperty || propertyInfo.Name == MatchProperty) { if (counter == 0) { sourceValue = propertyInfo.GetValue(value, null); sourceType = propertyInfo.GetValue(value, null).GetType(); } if (counter == 1) { matchValue = propertyInfo.GetValue(value, null); matchType = propertyInfo.GetValue(value, null).GetType(); } counter++; if (counter == 2) { break; } } } if (sourceType != null && matchType != null) { return sourceValue.ToString().Equals(matchValue.ToString()); //return Convert.ChangeType(sourceValue, sourceType) == Convert.ChangeType(matchValue, matchType); } return false; } private object _typeId = new object(); public override object TypeId { get { return this._typeId; } } } Now this code works, except for the fact that the validation process does not return which Property failed. And I simply can't figure out how to make it return one of the two. In reality I don't care which one it returns.. because both are failing.. Do you have an idea how to make it return the/or both Property/Properties that is/are failing.

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• How do I do distributed UML development (à la FOSS)?

  - by James A. Rosen

  I have a UML project (built in IBM's Rational System Architect/Modeler, so stored in their XML format) that has grown quite large. Additionally, it now contains several pieces that other groups would like to re-use. I come from a software development (especially FOSS) background, and am trying to understand how to use that as an analogy here. The problem I am grappling with is similar to the Fragile Base Class problem. Let me start with how it works in an object-oriented (say, Java or Ruby) FOSS ecosystem: Group 1 publishes some "core" package, say "net/smtp version 1.0" Group 2 includes Group 1's net/smtp 1.0 package in the vendor library of their software project At some point, Group 1 creates a new 2.0 branch of net/smtp that breaks backwards compatibility (say, it removes an old class or method, or moves a class from one package to another). They tell users of the 1.0 version that it will be deprecated in one year. Group 2, when they have the time, updates to net/smtp 2.0. When they drop in the new package, their compiler (or test suite, for Ruby) tells them about the incompatibility. They do have to make some manual changes, but all of the changes are in the code, in plain text, a medium with which they are quite familiar. Plus, they can often use their IDE's (or text editor's) "global-search-and-replace" function once they figure out what the fixes are. When we try to apply this model to UML in RSA, we run into some problems. RSA supports some fairly powerful refactorings, but they seem to only work if you have write access to all of the pieces. If I rename a class in one package, RSA can rename the references, but only at the same time. It's very difficult to look at the underlying source (the XML) and figure out what's broken. To fix such a problem in the RSA editor itself means tons of clicking on things -- there is no good equivalent of "global-search-and-replace," at least not after an incomplete refactor. They real sticking point seems to be that RSA assumes that you want to do all your editing using their GUI, but that makes certain operations prohibitively difficult. Does anyone have examples of open-source UML projects that have overcome this problem? What strategies do they use for communicating changes?

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• Macports 1.8.2 fails to build db46 on os x 1.6.3

  - by themoch

  i'm trying to put a dev environment on my mac, and to do so i need to install several packages which require db46 when running sudo port install db46 i get the following error: ---> Computing dependencies for db46 ---> Fetching db46 ---> Attempting to fetch patch.4.6.21.1 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch patch.4.6.21.2 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch patch.4.6.21.3 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch patch.4.6.21.4 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch db-4.6.21.tar.gz from http://distfiles.macports.org/db4/4.6.21_6 ---> Verifying checksum(s) for db46 ---> Extracting db46 ---> Applying patches to db46 ---> Configuring db46 ---> Building db46 Error: Target org.macports.build returned: shell command " cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_ports_databases_db46/work/db-4.6.21/build_unix" && /usr/bin/make -j2 all " returned error 2 Command output: ../dist/../libdb_java/db_java_wrap.c:9464: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9487: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9509: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9532: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9563: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jint' ../dist/../libdb_java/db_java_wrap.c:9588: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9613: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jint' ../dist/../libdb_java/db_java_wrap.c:9638: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9666: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9691: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9716: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9739: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9771: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9796: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9819: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9842: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9867: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jobject' ../dist/../libdb_java/db_java_wrap.c:9899: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9920: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9943: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9966: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jstring' ../dist/../libdb_java/db_java_wrap.c:9991: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jint' ../dist/../libdb_java/db_java_wrap.c:10010: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:10046: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:10071: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' make: *** [db_java_wrap.lo] Error 1 make: *** Waiting for unfinished jobs.... Note: Some input files use unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. cd ./classes && jar cf ../db.jar ./com/sleepycat Error: Status 1 encountered during processing. i have removed my /usr/local folder completely and it does not seem to help

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• Problem with OOP Class Definitions

  - by oben

  Hi, this is Oben from Turkey. I work for my homework in C++ and i have some problems with multiply definitions. My graph class ; class Graph{ private: string name; //Graph name fstream* graphFile; //Graph's file protected: string opBuf; //Operations buffer int containsNode(string); //Query if a node is present Node* nodes; //Nodes in the graph int nofNodes; //Number of nodes in the graph public: static int nOfGraphs; //Number of graphs produced Graph(); //Constructors and destructor Graph(int); Graph(string); Graph(const Graph &); ~Graph(); string getGraphName(); //Get graph name bool addNode(string); //add a node to the graph bool deleteNode(string); //delete a node from the graph bool addEdge(string,string); //add an edge to the graph bool deleteEdge(string,string); //delete an edge from the graph void intersect(const Graph&); //intersect the graph with the <par> void unite(const Graph&); //intersect the graph with the <par> string toString(); //get string representation of the graph void acceptTraverse(BreadthFirst*); void acceptTraverse(DepthFirst *); }; and my traversal class; class Traversal { public: string *visitedNodes; virtual string traverse (const Graph & ); }; class BreadthFirst : public Traversal { public : BreadthFirst(); string traverse(); }; class DepthFirst : public Traversal { public : DepthFirst(); string traverse(); }; My problem is in traversal class , i need to declare Graph class at the same time , in graph class i need traversal class to declare. I have big problems with declerations :) Could you please help me ?

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• Trouble passing a string as a SQLite ExecSQL command

  - by Hackbrew

  I keep getting the ERROR: near "PassWord": syntax error when trying to execute the ExecSQL() statement. The command looks good in the output of the text file. In fact, I copied & pasted the command directly into SQLite Database Browser and the commend executed properly. Here's the code that's producing the error: procedure TForm1.Button1Click(Sender: TObject); var i, iFieldSize: integer; sFieldName, sFieldType, sFieldList, sExecSQL: String; names: TStringList; f1: Textfile; begin //Open Source table - Table1 has 8 fields but has only two different field types ftString and Boolean Table1.TableName:= 'PWFile'; Table1.Open; //FDConnection1.ExecSQL('drop table PWFile'); sFieldList := ''; names := TStringList.Create; for i := 0 to Table1.FieldCount - 1 do begin sFieldName := Table1.FieldDefList.FieldDefs[i].Name; sFieldType := GetEnumName(TypeInfo(TFieldType),ord(Table1.FieldDefList.FieldDefs[i].DataType)); iFieldSize := Table1.FieldDefList.FieldDefs[i].Size; if sFieldType = 'ftString' then sFieldType := 'NVARCHAR' + '(' + IntToStr(iFieldSize) + ')'; if sFieldType = 'ftBoolean' then sFieldType := 'INTEGER'; names.Add(sFieldName + ' ' + sFieldType); if sFieldList = '' then sFieldList := sFieldName + ' ' + sFieldType else sFieldList := sFieldList + ', ' + sFieldName + ' ' + sFieldType; end; ListBox1.Items.Add(sFieldList); sExecSQL := 'create table IF NOT EXISTS PWFile (' + sFieldList + ')'; // 08/18/2014 - Entered this to log the SQLite FDConnection1.ExecSQL Command to a file AssignFile(f1, 'C:\Users\Test User\Documents\SQLite_Command.txt'); Rewrite(f1); Writeln(f1, sExecSQL); { insert code here that would require a Flush before closing the file } Flush(f1); { ensures that the text was actually written to file } CloseFile(f1); FDConnection1.ExecSQL(sFieldList); Table1.Close; end; Here's the actual command that gets executed: create table IF NOT EXISTS PWFile (PassWord NVARCHAR(10), PassName NVARCHAR(10), Dept NVARCHAR(10), Active NVARCHAR(1), Admin INTEGER, Shred INTEGER, Reports INTEGER, Maintain INTEGER)

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• How to reduce redundant code when adding new c++0x rvalue reference operator overloads

  - by Inverse

  I am adding new operator overloads to take advantage of c++0x rvalue references, and I feel like I'm producing a lot of redundant code. I have a class, tree, that holds a tree of algebraic operations on double values. Here is an example use case: tree x = 1.23; tree y = 8.19; tree z = (x + y)/67.31 - 3.15*y; ... std::cout << z; // prints "(1.23 + 8.19)/67.31 - 3.15*8.19" For each binary operation (like plus), each side can be either an lvalue tree, rvalue tree, or double. This results in 8 overloads for each binary operation: // core rvalue overloads for plus: tree operator +(const tree& a, const tree& b); tree operator +(const tree& a, tree&& b); tree operator +(tree&& a, const tree& b); tree operator +(tree&& a, tree&& b); // cast and forward cases: tree operator +(const tree& a, double b) { return a + tree(b); } tree operator +(double a, const tree& b) { return tree(a) + b; } tree operator +(tree&& a, double b) { return std::move(a) + tree(b); } tree operator +(double a, tree&& b) { return tree(a) + std::move(b); } // 8 more overloads for minus // 8 more overloads for multiply // 8 more overloads for divide // etc which also has to be repeated in a way for each binary operation (minus, multiply, divide, etc). As you can see, there are really only 4 functions I actually need to write; the other 4 can cast and forward to the core cases. Do you have any suggestions for reducing the size of this code? PS: The class is actually more complex than just a tree of doubles. Reducing copies does dramatically improve performance of my project. So, the rvalue overloads are worthwhile for me, even with the extra code. I have a suspicion that there might be a way to template away the "cast and forward" cases above, but I can't seem to think of anything.

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• Using Core Data Concurrently and Reliably

  - by John Topley

  I'm building my first iOS app, which in theory should be pretty straightforward but I'm having difficulty making it sufficiently bulletproof for me to feel confident submitting it to the App Store. Briefly, the main screen has a table view, upon selecting a row it segues to another table view that displays information relevant for the selected row in a master-detail fashion. The underlying data is retrieved as JSON data from a web service once a day and then cached in a Core Data store. The data previous to that day is deleted to stop the SQLite database file from growing indefinitely. All data persistence operations are performed using Core Data, with an NSFetchedResultsController underpinning the detail table view. The problem I am seeing is that if you switch quickly between the master and detail screens several times whilst fresh data is being retrieved, parsed and saved, the app freezes or crashes completely. There seems to be some sort of race condition, maybe due to Core Data importing data in the background whilst the main thread is trying to perform a fetch, but I'm speculating. I've had trouble capturing any meaningful crash information, usually it's a SIGSEGV deep in the Core Data stack. The table below shows the actual order of events that happen when the detail table view controller is loaded: Main Thread Background Thread viewDidLoad Get JSON data (using AFNetworking) Create child NSManagedObjectContext (MOC) Parse JSON data Insert managed objects in child MOC Save child MOC Post import completion notification Receive import completion notification Save parent MOC Perform fetch and reload table view Delete old managed objects in child MOC Save child MOC Post deletion completion notification Receive deletion completion notification Save parent MOC Once the AFNetworking completion block is triggered when the JSON data has arrived, a nested NSManagedObjectContext is created and passed to an "importer" object that parses the JSON data and saves the objects to the Core Data store. The importer executes using the new performBlock method introduced in iOS 5: NSManagedObjectContext *child = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType]; [child setParentContext:self.managedObjectContext]; [child performBlock:^{ // Create importer instance, passing it the child MOC... }]; The importer object observes its own MOC's NSManagedObjectContextDidSaveNotification and then posts its own notification which is observed by the detail table view controller. When this notification is posted the table view controller performs a save on its own (parent) MOC. I use the same basic pattern with a "deleter" object for deleting the old data after the new data for the day has been imported. This occurs asynchronously after the new data has been fetched by the fetched results controller and the detail table view has been reloaded. One thing I am not doing is observing any merge notifications or locking any of the managed object contexts or the persistent store coordinator. Is this something I should be doing? I'm a bit unsure how to architect this all correctly so would appreciate any advice.

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• howto parse struct to C++ dll from C#

  - by Nerds Rule

  I am trying to call a function in a unmanaged C++ dll. It has this prototype: [DllImport("C:\\Program Files\\MySDK\\VSeries.dll", EntryPoint = "BII_Send_Index_Template_MT" )] internal unsafe static extern Int32 BII_Send_Index_Template_MT(IntPtr pUnitHandle, ref BII_Template template, Int32 option, Boolean async); BII_Template template = new BII_Template(); error_code = BII_Send_Index_Template_MT(pUnitHandle, ref template, option, false); I is how I define the BII_Template struct in C#: public unsafe struct BII_Template { public ulong id; public ulong employee_id; public ulong password; public byte sensor_version; public byte template_version; public fixed char name[16]; public byte finger; public byte admin_level; public byte schedule; public byte security_thresh; public fixed byte noise_level[18]; public byte corramb; public byte reference_x; public byte reference_y; public fixed byte ihcore[3]; public fixed byte ivcore[3]; public byte temp_xoffset; public byte temp_yoffset; public byte index; public fixed byte inphase[5500]; }; It build and when I run it the dll return error_code = "The record checksum is invalid." I assume that I am using the ref keyword in a wrong way or the size of some of the elements in the struct is wrong. ----- EDIT ------------ Here is the struct in C++: typedef struct { unsigned long id; unsigned long employee_id; unsigned long password; unsigned char sensor_version; unsigned char template_version; char name[16]; unsigned char finger; unsigned char admin_level; unsigned char schedule; unsigned char security_thresh; unsigned char noise_level[18]; unsigned char corramb ; unsigned char reference_x ; unsigned char reference_y ; unsigned char ihcore[NUM_CORE]; unsigned char ivcore[NUM_CORE]; unsigned char temp_xoffset; unsigned char temp_yoffset; unsigned char index; unsigned char inphase[PACKED_ARRAY_SIZE]; } BII_Template;

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• Sessions not persisting between requests

  - by klonq

  My session objects are only stored within the request scope on google app engine and I can't figure out how to persist objects between requests. The docs are next to useless on this matter and I can't find anyone who's experienced a similar problem. Please help. When I store session objects in the servlet and forward the request to a JSP using: getServletContext().getRequestDispatcher("/example.jsp").forward(request,response); Everything works like it should. But when I store objects to the session and redirect the request using: response.sendRedirect("/example/url"); The session objects are lost to the ether. In fact when I dump session key/value pairs on new requests there is absolutely nothing, session objects only appear within the request scope of servlets which create session objects. It appears to me that the objects are not being written to Memcache or Datastore. In terms of configuring sessions for my application I have set <sessions-enabled>true</sessions-enabled> In appengine-web.xml. Is there anything else I am missing? The single paragraph of documentation on sessions also notes that only objects which implement Serializable can be stored in the session between requests. I have included an example of the code which is not working below. The obvious solution is to not use redirects, and this might be ok for the example given below but some application data does need to be stored in the session between requests so I need to find a solution to this problem. EXAMPLE: The class FlashMessage gives feedback to the user from server-side operations. if (email.send()) { FlashMessage flash = new FlashMessage(FlashMessage.SUCCESS, "Your message has been sent."); session.setAttribute(FlashMessage.SESSION_KEY, flash); // The flash message will not be available in the session object in the next request response.sendRedirect(URL.HOME); } else { FlashMessage flash = new FlashMessage(FlashMessage.ERROR, FlashMessage.INVALID_FORM_DATA); session.setAttribute(FlashMessage.SESSION_KEY, flash); // The flash message is displayed without problem getServletContext().getRequestDispatcher(Templates.CONTACT_FORM).forward(request,response); } FlashMessage.java import java.io.Serializable; public class FlashMessage implements Serializable { private static final long serialVersionUID = 8109520737272565760L; // I have tried using different, default and no serialVersionUID public static final String SESSION_KEY = "flashMessage"; public static final String ERROR = "error"; public static final String SUCCESS = "success"; public static final String INVALID_FORM_DATA = "Your request failed to validate."; private String message; private String type; public FlashMessage (String type, String message) { this.type = type; this.message = message; } public String display(){ return "<div id='flash' class='" + type + "'>" + message + "</div>"; } }

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• Java DriverManager Always Assigns My Driver

  - by JGB146

  I am writing a driver to act as a wrapper around two separate MySQL connections (to distributed databases). Basically, the goal is to enable interaction with my driver for all applications instead of requiring the application to sort out which database holds the desired data. Most of the code for this is in place, but I'm having a problem in that when I attempt to create connections via the MySQL Driver, the DriverManager is returning an instance of my driver instead of the MySQL Driver. I'd appreciate any tips on what could be causing this and what could be done to fix it! Below is a few relevant snippets of code. I can provide more, but there's a lot, so I'd need to know what else you want to see. First, from MyDriver.java: public MyDriver() throws SQLException { DriverManager.registerDriver(this); } public Connection connect(String url, Properties info) throws SQLException { try { return new MyConnection(info); } catch (Exception e) { return null; } } public boolean acceptsURL(String url) throws SQLException { if (url.contains("jdbc:jgb://")) { return true; } return false; } It is my understanding that this acceptsURL function will dictate whether or not the DriverManager deems my driver a suitable fit for a given URL. Hence it should only be passing connections from my driver if the URL contains "jdbc:jgb://" right? Here's code from MyConnection.java: Connection c1 = null; Connection c2 = null; /** *Constructors */ public DDBSConnection (Properties info) throws SQLException, Exception { info.list(System.out); //included for testing Class.forName("com.mysql.jdbc.Driver").newInstance(); String url1 = "jdbc:mysql://server1.com/jgb"; String url2 = "jdbc:mysql://server2.com/jgb"; this.c1 = DriverManager.getConnection( url1, info.getProperty("username"), info.getProperty("password")); this.c2 = DriverManager.getConnection( url2, info.getProperty("username"), info.getProperty("password")); } And this tells me two things. First, the info.list() call confirms that the correct user and password are being sent. Second, because we enter an infinite loop, we see that the DriverManager is providing new instances of my connection as matches for the mysql URLs instead of the desired mysql driver/connection. FWIW, I have separately tested implementations that go straight to the mysql driver using this exact syntax (al beit only one at a time), and was able to successfully interact with each database individually from a test application outside of my driver.

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• Extending AdapterView

  - by Ander Webbs

  Hi, i'm trying to make (for learning purposes) my own implementation of a simple AdapterView where items comes from an basic Adapter (ImageAdapter from sdk samples). Actual code is like this: public class MyAdapterView extends AdapterView<ImageAdapter> implements AdapterView.OnItemClickListener{ private ImageAdapter mAdapter; public MyAdapterView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); initThings(); } private void initThings(){ setOnItemClickListener(this); } @Override public ImageAdapter getAdapter() { // TODO Auto-generated method stub return mAdapter; } @Override public void setAdapter(ImageAdapter adapter) { // TODO Auto-generated method stub mAdapter=adapter; requestLayout(); } View obtainView(int position) { View child = mAdapter.getView(position, null, this); return child; } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { super.onLayout(changed, l, t, r, b); for(int i=0;i<mAdapter.getCount();i++){ View child = obtainView(i); child.layout(10, 70*i, 70, 70); addViewInLayout(child, i, null, true); } this.invalidate(); } @Override public void onItemClick(AdapterView<?> parent, View v, int position, long id) { Log.d("MYEXAMPLES","Clicked an item!"); } } This isn't a coding masterpiece, it just displays a pseudo-listview with pictures. I know i could've used ListView, GridView, Spinner, etc. but i'm relative new to android and i'm trying to figure out some things on it. Well, the question here is: Why is my onItemClick not firing? Using the same ImageAdapter with a GridView, everything works ok, but when i use with above class, i get nothing. Inside AdapterView.java there is code for those click, longclick, etc events... so why can't i just fire them? Maybe i'm misunderstanding basic things on how AdapterView works? Should I extend other base classes instead? And why? Hoping to find more experienced guidance on here, thanks in advance.

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• Import? Initialize? what do to?

  - by Jeremy B

  I'm working on homework and I'm close but I am having an issue. I just learned how to work with packages in eclipse so I have a class that is importing another class from a package (I think I said that right) The main prompts the user to enter an integer between -100 and 100 and I am having an issue with validating it. I know the issue is where I'm importing I'm just unsure the direction I need to go to fix it. This is a section of my main code. (my issue starts with the last couple lines if you want to skip ahead) import myUtils.util.Console; public class ConsoleTestApp { public static void main(String args[]) { // create the Console object Console c = new Console(); // display a welcome message c.println("Welcome to the Console Tester application"); c.println(); // int c.println("Int Test"); int i = c.getIntWithinRange("Enter an integer between -100 and 100: ", -101, 101); c.println(); I have a class called Console that is located in another package that I believe I have properly imported. here is the code I am stuck on in my console class. public int getIntWithinRange(String prompt, int min, int max) { int i = 0; boolean isValid = false; while (isValid == false) { System.out.println(prompt); if (sc.hasNextInt()) { //if user chooses menu option less than 1 the program will print an error message i = sc.nextInt(); if (i < min) { System.out.println("Error! Please enter an int greater than -100"); } else if (i > max) { System.out.println("Error! Please enter an int less than 100"); } else isValid = true; } else System.out.println("Error! Invalid number value"); sc.nextLine(); } // return the int return i; } when I run this I keep getting my last print which is an invalid number value. am I not importing the code from the main method in the other console properly?

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• Linked lists in Java - help with assignment

  - by user368241

  Representation of a string in linked lists In every intersection in the list there will be 3 fields : The letter itself. The number of times it appears consecutively. A pointer to the next intersection in the list. The following class CharNode represents a intersection in the list : public class CharNode { private char _data; private int _value; private charNode _next; public CharNode (char c, int val, charNode n) { _data = c; _value = val; _next = n; } public charNode getNext() { return _next; } public void setNext (charNode node) { _next = node; } public int getValue() { return _value; } public void setValue (int v) { value = v; } public char getData() { return _data; } public void setData (char c) { _data = c; } } The class StringList represents the whole list : public class StringList { private charNode _head; public StringList() { _head = null; } public StringList (CharNode node) { _head = node; } } Add methods to the class StringList according to the details : (I will add methods gradually according to my specific questions) (Pay attention, these are methods from the class String and we want to fulfill them by the representation of a string by a list as explained above) public int indexOf (int ch) - returns the index in the string it is operated on of the first appeareance of the char "ch". If the char "ch" doesn't appear in the string, returns -1. If the value of fromIndex isn't in the range, returns -1. Pay attention to all the possible error cases. Write what is the time complexity and space complexity of every method that you wrote. Make sure the methods you wrote are effective. It is NOT allowed to use ready classes of Java. It is NOT allowed to move to string and use string operations. Here is my try to write the method indexOf (int ch). Kindly assist me with fixing the bugs so I can move on. public int indexOf (int ch) { int count = 0; charNode pose = _head; if (pose == null ) { return -1; } for (pose = _head; pose!=null && pose.getNext()!='ch'; pose = pose.getNext()) { count++; } if (pose!=null) return count; else return -1; }

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• Java replacement for C macros

  - by thkala

  Recently I refactored the code of a 3rd party hash function from C++ to C. The process was relatively painless, with only a few changes of note. Now I want to write the same function in Java and I came upon a slight issue. In the C/C++ code there is a C preprocessor macro that takes a few integer variables names as arguments and performs a bunch of bitwise operations with their contents and a few constants. That macro is used in several different places, therefore its presence avoids a fair bit of code duplication. In Java, however, there is no equivalent for the C preprocessor. There is also no way to affect any basic type passed as an argument to a method - even autoboxing produces immutable objects. Coupled with the fact that Java methods return a single value, I can't seem to find a simple way to rewrite the macro. Avenues that I considered: Expand the macro by hand everywhere: It would work, but the code duplication could make things interesting in the long run. Write a method that returns an array: This would also work, but it would repeatedly result into code like this: long tmp[] = bitops(k, l, m, x, y, z); k = tmp[0]; l = tmp[1]; m = tmp[2]; x = tmp[3]; y = tmp[4]; z = tmp[5]; Write a method that takes an array as an argument: This would mean that all variable names would be reduced to array element references - it would be rather hard to keep track of which index corresponds to which variable. Create a separate class e.g. State with public fields of the appropriate type and use that as an argument to a method: This is my current solution. It allows the method to alter the variables, while still keeping their names. It has the disadvantage, however, that the State class will get more and more complex, as more macros and variables are added, in order to avoid copying values back and forth among different State objects. How would you rewrite such a C macro in Java? Is there a more appropriate way to deal with this, using the facilities provided by the standard Java 6 Development Kit (i.e. without 3rd party libraries or a separate preprocessor)?

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• Java java.util.ConcurrentModificationException error

  - by vijay

  Hi all, please can anybody help me solve this problem last so many days I could not able to solve this error. I tried using synchronized method and other ways but did not work so please help me Error java.util.ConcurrentModificationException at java.util.AbstractList$Itr.checkForComodification(Unknown Source) at java.util.AbstractList$Itr.remove(Unknown Source) at JCA.startAnalysis(JCA.java:103) at PrgMain2.doPost(PrgMain2.java:235) Code public synchronized void startAnalysis() { //set Starting centroid positions - Start of Step 1 setInitialCentroids(); Iterator<DataPoint> n = mDataPoints.iterator(); //assign DataPoint to clusters loop1: while (true) { for (Cluster c : clusters) { c.addDataPoint(n.next()); if (!n.hasNext()) break loop1; } } //calculate E for all the clusters calcSWCSS(); //recalculate Cluster centroids - Start of Step 2 for (Cluster c : clusters) { c.getCentroid().calcCentroid(); } //recalculate E for all the clusters calcSWCSS(); // List copy = new ArrayList(originalList); //synchronized (c) { for (int i = 0; i < miter; i++) { //enter the loop for cluster 1 for (Cluster c : clusters) { for (Iterator<DataPoint> k = c.getDataPoints().iterator(); k.hasNext(); ) { // synchronized (k) { DataPoint dp = k.next(); System.out.println("Value of DP" +dp); //pick the first element of the first cluster //get the current Euclidean distance double tempEuDt = dp.getCurrentEuDt(); Cluster tempCluster = null; boolean matchFoundFlag = false; //call testEuclidean distance for all clusters for (Cluster d : clusters) { //if testEuclidean < currentEuclidean then if (tempEuDt > dp.testEuclideanDistance(d.getCentroid())) { tempEuDt = dp.testEuclideanDistance(d.getCentroid()); tempCluster = d; matchFoundFlag = true; } //if statement - Check whether the Last EuDt is > Present EuDt } //for variable 'd' - Looping between different Clusters for matching a Data Point. //add DataPoint to the cluster and calcSWCSS if (matchFoundFlag) { tempCluster.addDataPoint(dp); //k.notify(); // if(k.hasNext()) k.remove(); for (Cluster d : clusters) { d.getCentroid().calcCentroid(); } //for variable 'd' - Recalculating centroids for all Clusters calcSWCSS(); } //if statement - A Data Point is eligible for transfer between Clusters. // }// syn } //for variable 'k' - Looping through all Data Points of the current Cluster. }//for variable 'c' - Looping through all the Clusters. }//for variable 'i' - Number of iterations. // syn }

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• Refactoring Singleton Overuse

  - by drharris

  Today I had an epiphany, and it was that I was doing everything wrong. Some history: I inherited a C# application, which was really just a collection of static methods, a completely procedural mess of C# code. I refactored this the best I knew at the time, bringing in lots of post-college OOP knowledge. To make a long story short, many of the entities in code have turned out to be Singletons. Today I realized I needed 3 new classes, which would each follow the same Singleton pattern to match the rest of the software. If I keep tumbling down this slippery slope, eventually every class in my application will be Singleton, which will really be no logically different from the original group of static methods. I need help on rethinking this. I know about Dependency Injection, and that would generally be the strategy to use in breaking the Singleton curse. However, I have a few specific questions related to this refactoring, and all about best practices for doing so. How acceptable is the use of static variables to encapsulate configuration information? I have a brain block on using static, and I think it is due to an early OO class in college where the professor said static was bad. But, should I have to reconfigure the class every time I access it? When accessing hardware, is it ok to leave a static pointer to the addresses and variables needed, or should I continually perform Open() and Close() operations? Right now I have a single method acting as the controller. Specifically, I continually poll several external instruments (via hardware drivers) for data. Should this type of controller be the way to go, or should I spawn separate threads for each instrument at the program's startup? If the latter, how do I make this object oriented? Should I create classes called InstrumentAListener and InstrumentBListener? Or is there some standard way to approach this? Is there a better way to do global configuration? Right now I simply have Configuration.Instance.Foo sprinkled liberally throughout the code. Almost every class uses it, so perhaps keeping it as a Singleton makes sense. Any thoughts? A lot of my classes are things like SerialPortWriter or DataFileWriter, which must sit around waiting for this data to stream in. Since they are active the entire time, how should I arrange these in order to listen for the events generated when data comes in? Any other resources, books, or comments about how to get away from Singletons and other pattern overuse would be helpful.

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