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• Why doesn't java.util.Set have get(int index)?

  - by Marty Pitt

  I'm sure there's a good reason, but could someone please explain why the java.util.Set interface lacks get(int Index), or any similar get() method? It seems that sets are great for putting things into, but I can't find an elegant way of retrieving a single item from it. If I know I want the first item, I can use set.iterator().next(), but otherwise it seems I have to cast to an Array to retrieve an item at a specific index? What are the appropriate ways of retrieving data from a set? (other than using an iterator) I'm sure the fact that it's excluded from the API means there's a good reason for not doing this -- could someone please enlighten me? EDIT: Some extremely great answers here, and a few saying "more context". The specific scneario was a dbUnit test, where I could reasonalby assert that the returned set from a query had only 1 item, and I was trying to access that item. However, the question is more valid without the scenario, as it remains more focussed : What's the difference between set & list. Thanks to all for the fantastic answers below.

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• Scala type inference failure on "? extends" in Java code

  - by oxbow_lakes

  I have the following simple Java code: package testj; import java.util.*; public class Query<T> { private static List<Object> l = Arrays.<Object>asList(1, "Hello", 3.0); private final Class<? extends T> clazz; public static Query<Object> newQuery() { return new Query<Object>(Object.class); } public Query(Class<? extends T> clazz) { this.clazz = clazz; } public <S extends T> Query<S> refine(Class<? extends S> clazz) { return new Query<S>(clazz); } public List<T> run() { List<T> r = new LinkedList<T>(); for (Object o : l) { if (clazz.isInstance(o)) r.add(clazz.cast(o)); } return r; } } I can call this from Java as follows: Query<String> sq = Query.newQuery().refine(String.class); //NOTE NO <String> But if I try and do the same from Scala: val sq = Query.newQuery().refine(classOf[String]) I get the following error: error: type mismatch found :lang.this.class[scala.this.Predef.String] required: lang.this.class[?0] forSome{ type ?0 <: ? } val sq = Query.newQuery().refine(classOf[String]) This is only fixed by the insertion of the correct type parameter! val sq = Query.newQuery().refine[String](classOf[String]) Why can't scala infer this from my argument? Note I am using Scala 2.7

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• Casting to specify unknown object type?

  - by fuzzygoat

  In the following code I have a view object that is an instance of UIScrollView, if I run the code below I get warnings saying that "UIView might not respond to -setContentSize etc." UIImage *image = [UIImage imageNamed:@"Snowy_UK.jpg"]; imageView = [[UIImageView alloc] initWithImage:image]; [[self view] addSubview:imageView]; [[self view] setContentSize:[image size]]; [[self view] setMaximumZoomScale:2.0]; [[self view] setMinimumZoomScale: [[self view] bounds].size.width / [image size].width]; I have checked the type of the object and [self view] is indeed a UIScrollView. I am guessing that this is just the compiler making a bad guess as to the type and the solution is simply to cast the object to the correct type manually, am I getting this right? UIScrollView *scrollView = (UIScrollView *)[self view]; UIImage *image = [UIImage imageNamed:@"Snowy_UK.jpg"]; imageView = [[UIImageView alloc] initWithImage:image]; [[self view] addSubview:imageView]; [scrollView setContentSize:[image size]]; [scrollView setMaximumZoomScale:2.0]; [scrollView setMinimumZoomScale: [scrollView bounds].size.width / [image size].width]; cheers Gary.

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• Converting ntext to nvcharmax(max) - Getting around size limitation

  - by Overflew

  Hi all, I'm trying to change an existing SQL NText column to nvcharmax(max), and encountering an error on the size limit. There's a large amount of existing data, some of which is more than the 8k limit, I believe. We're looking to convert this, so that the field is searchable in LINQ. The 2x SQL statements I've tried are: update Table set dataNVarChar = convert(nvarchar(max), dataNtext) where dataNtext is not null update Table set dataNVarChar = cast(dataNtext as nvarchar(max)) where dataNtext is not null And the error I get is: Cannot create a row of size 8086 which is greater than the allowable maximum row size of 8060. This is using SQL Server 2008. Any help appreciated, Thanks. Update / Solution: The marked answer below is correct, and SQL 2008 can change the column to the correct data type in my situation, and there are no dramas with the LINQ-utilising application we use on top of it: alter table [TBL] alter column [COL] nvarchar(max) I've also been advised to follow it up with: update [TBL] set [COL] = [COL] Which completes the conversion by moving the data from the lob structure to the table (if the length in less than 8k), which improves performance / keeps things proper.

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• DRYing out implementation of ICloneable in several classes

  - by Sarah Vessels

  I have several different classes that I want to be cloneable: GenericRow, GenericRows, ParticularRow, and ParticularRows. There is the following class hierarchy: GenericRow is the parent of ParticularRow, and GenericRows is the parent of ParticularRows. Each class implements ICloneable because I want to be able to create deep copies of instances of each. I find myself writing the exact same code for Clone() in each class: object ICloneable.Clone() { object clone; using (var stream = new MemoryStream()) { var formatter = new BinaryFormatter(); // Serialize this object formatter.Serialize(stream, this); stream.Position = 0; // Deserialize to another object clone = formatter.Deserialize(stream); } return clone; } I then provide a convenience wrapper method, for example in GenericRows: public GenericRows Clone() { return (GenericRows)((ICloneable)this).Clone(); } I am fine with the convenience wrapper methods looking about the same in each class because it's very little code and it does differ from class to class by return type, cast, etc. However, ICloneable.Clone() is identical in all four classes. Can I abstract this somehow so it is only defined in one place? My concern was that if I made some utility class/object extension method, it would not correctly make a deep copy of the particular instance I want copied. Is this a good idea anyway?

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• How to get a JTextField event that started a pop up menu in Java ?

  - by Frank

  I have a JTextField that represents a day, such as "Sunday", when I left mouse click on it, it changes background color, when I right mouse click on it, a pop up menu comes up, after I click on a menu item, such as "1st of month", it gets the value, closes the menu and then change the bgcolor, my code looks like this : JTextField dayHeading=new JTextField("Su"); ...... final JPopupMenu Pmenu; JMenuItem menuItem; Pmenu=new JPopupMenu(); menuItem=new JMenuItem("1st of month"); Pmenu.add(menuItem); menuItem=new JMenuItem("2nd of month"); Pmenu.add(menuItem); ...... menuItem.addMouseListener(new MouseAdapter() { public void mouseReleased(final MouseEvent e) { System.out.println(((JMenuItem)e.getComponent()).getText()); onHeadingClicked(e); // Error : java.lang.ClassCastException: javax.swing.JMenuItem cannot be cast to javax.swing.JTextField // How to get the orininal JTextField event that started this pop up menu, so I can pass it onto onHeadingClicked() ? } }); ...... dayHeading.setEditable(false); dayHeading.setFocusable(false); dayHeading.addMouseListener(new MouseAdapter() { public void mouseReleased(final MouseEvent evt) { if (SwingUtilities.isLeftMouseButton(evt)) onHeadingClicked(evt); else if (SwingUtilities.isRightMouseButton(evt)) Pmenu.show(evt.getComponent(),evt.getX(),evt.getY()); } }); ...... void onHeadingClicked(final java.awt.event.MouseEvent evt) { final javax.swing.JTextField fld=(javax.swing.JTextField) evt.getSource(); ... } My question is : in the menuItem.addMouseListener section, how to get the orininal JTextField event that started this pop up menu, so I can pass it onto onHeadingClicked() ?

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• ClassCastException in iterating list returned by Query using Hibernate Query Language

  - by Tushar Paliwal

  I'm beginner in hibernate.I'm trying a simplest example using HQL but it generates exception at line 25 ClassCastException when i try to iterate list.When i try to cast the object returned by next() methode of iterator it generates the same problem.I could not identify the problem.Kindly give me solution of the problem. Employee.java package one; import javax.persistence.Entity; import javax.persistence.Id; @Entity public class Employee { @Id private Long id; private String name; public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Employee(Long id, String name) { super(); this.id = id; this.name = name; } public Employee() { } } Main2.java package one; import java.util.Iterator; import java.util.List; import org.hibernate.Query; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.Transaction; import org.hibernate.cfg.Configuration; public class Main2 { public static void main(String[] args) { SessionFactory sf=new Configuration().configure().buildSessionFactory(); Session s1=sf.openSession(); Query q=s1.createQuery("from Employee "); Transaction tx=s1.beginTransaction(); List l=q.list(); Iterator itr=l.iterator(); while(itr.hasNext()) { Object obj[]=(Object[])itr.next();//Line 25 for(Object temp:obj) { System.out.println(temp); } } tx.commit(); s1.close(); sf.close(); } }

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• Tapestry + JaxB conflict

  - by alex

  Hi all ! I need your help to resolve a conflict between Tapestry and JaxB. The error is : com.sun.xml.stream.ZephyrParserFactory cannot be cast to org.codehaus.stax2.XMLInputFactory2 I find a way to resolve it, but it is for jetty : http://tynamo.org/tapestry-resteasy+guide The solution seems to be to add a system properties to declare : javax.xml.stream.XMLInputFactory = com.ctc.wstx.stax.WstxInputFactory But i don't know how to do this for Tomcat. I try to do it int he web.xml like : <env-entry> <env-entry-name> javax.xml.stream.XMLInputFactory </env-entry-name> <env-entry-value> com.ctc.wstx.stax.WstxInputFactory </env-entry-value> <env-entry-type> com.ctc.wstx.stax.WstxInputFactory </env-entry-type> </env-entry> without success... I am also aware for another solution :) thx for helping me.

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• Wildcards vs. generic methods

  - by FredOverflow

  Is there any practical difference between the following approaches to print all elements in a range? public static void printA(Iterable<?> range) { for (Object o : range) { System.out.println(o); } } public static <T> void printB(Iterable<T> range) { for (T x : range) { System.out.println(x); } } Apparently, printB involves an additional checked cast to Object (see line 16), which seems rather stupid to me -- isn't everything an Object anyway? public static void printA(java.lang.Iterable); Code: 0: aload_0 1: invokeinterface #18, 1; //InterfaceMethod java/lang/Iterable.iterator:()Ljava/util/Iterator; 6: astore_2 7: goto 24 10: aload_2 11: invokeinterface #24, 1; //InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object; 16: astore_1 17: getstatic #30; //Field java/lang/System.out:Ljava/io/PrintStream; 20: aload_1 21: invokevirtual #36; //Method java/io/PrintStream.println:(Ljava/lang/Object;)V 24: aload_2 25: invokeinterface #42, 1; //InterfaceMethod java/util/Iterator.hasNext:()Z 30: ifne 10 33: return public static void printB(java.lang.Iterable); Code: 0: aload_0 1: invokeinterface #18, 1; //InterfaceMethod java/lang/Iterable.iterator:()Ljava/util/Iterator; 6: astore_2 7: goto 27 10: aload_2 11: invokeinterface #24, 1; //InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object; 16: checkcast #3; //class java/lang/Object 19: astore_1 20: getstatic #30; //Field java/lang/System.out:Ljava/io/PrintStream; 23: aload_1 24: invokevirtual #36; //Method java/io/PrintStream.println:(Ljava/lang/Object;)V 27: aload_2 28: invokeinterface #42, 1; //InterfaceMethod java/util/Iterator.hasNext:()Z 33: ifne 10 36: return

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• Native Endians and Auto Conversion

  - by KnickerKicker

  so the following converts big endians to little ones uint32_t ntoh32(uint32_t v) { return (v << 24) | ((v & 0x0000ff00) << 8) | ((v & 0x00ff0000) >> 8) | (v >> 24); } works. like a charm. I read 4 bytes from a big endian file into char v[4] and pass it into the above function as ntoh32 (* reinterpret_cast<uint32_t *> (v)) that doesn't work - because my compiler (VS 2005) automatically converts the big endian char[4] into a little endian uint32_t when I do the cast. AFAIK, this automatic conversion will not be portable, so I use uint32_t ntoh_4b(char v[]) { uint32_t a = 0; a |= (unsigned char)v[0]; a <<= 8; a |= (unsigned char)v[1]; a <<= 8; a |= (unsigned char)v[2]; a <<= 8; a |= (unsigned char)v[3]; return a; } yes the (unsigned char) is necessary. yes it is dog slow. there must be a better way. anyone ?

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• boost::python string-convertible properties

  - by Checkers

  I have a C++ class, which has the following methods: class Bar { ... const Foo& getFoo() const; void setFoo(const Foo&); }; where class Foo is convertible to std::string (it has an implicit constructor from std::string and an std::string cast operator). I define a Boost.Python wrapper class, which, among other things, defines a property based on previous two functions: class_<Bar>("Bar") ... .add_property( "foo", make_function( &Bar::getFoo, return_value_policy<return_by_value>()), &Bar::setFoo) ... I also mark the class as convertible to/from std::string. implicitly_convertible<std::string, Foo>(); implicitly_convertible<Foo, std::string>(); But at runtime I still get a conversion error trying to access this property: TypeError: No to_python (by-value) converter found for C++ type: Foo How to achieve the conversion without too much boilerplate of wrapper functions? (I already have all the conversion functions in class Foo, so duplication is undesirable.

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• Using reflection to find all linq2sql tables and ensure they match the database

  - by Jake Stevenson

  I'm trying to use reflection to automatically test that all my linq2sql entities match the test database. I thought I'd do this by getting all the classes that inherit from DataContext from my assembly: var contexttypes = Assembly.GetAssembly(typeof (BaseRepository<,>)).GetTypes().Where( t => t.IsSubclassOf(typeof(DataContext))); foreach (var contexttype in contexttypes) { var context = Activator.CreateInstance(contexttype); var tableProperties = type.GetProperties().Where(t=> t.PropertyType.Name == typeof(ITable<>).Name); foreach (var propertyInfo in tableProperties) { var table = (propertyInfo.GetValue(context, null)); } } So far so good, this loops through each ITable< in each datacontext in the project. If I debug the code, "table" is properly instantiated, and if I expand the results view in the debugger I can see actual data. BUT, I can't figure out how to get my code to actually query that table. I'd really like to just be able to do table.FirstOrDefault() to get the top row out of each table and make sure the SQL fetch doesn't fail. But I cant cast that table to be anything I can query. Any suggestions on how I can make this queryable? Just the ability to call .Count() would be enough for me to ensure the entities don't have anything that doesn't match the table columns.

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• MUD (game) design concept question about timed events.

  - by mudder

  I'm trying my hand at building a MUD (multiplayer interactive-fiction game) I'm in the design/conceptualizing phase and I've run into a problem that I can't come up with a solution for. I'm hoping some more experienced programmers will have some advice. Here's the problem as best I can explain it. When the player decides to perform an action he sends a command to the server. the server then processes the command, determines whether or not the action can be performed, and either does it or responds with a reason as to why it could not be done. One reason that an action might fail is that the player is busy doing something else. For instance, if a player is mid-fight and has just swung a massive broadsword, it might take 3 seconds before he can repeat this action. If the player attempts to swing again to soon, the game will respond indicating that he must wait x seconds before doing that. Now, this I can probably design without much trouble. The problem I'm having is how I can replicate this behavior from AI creatures. All of the events that are being performed by the server ON ITS OWN, aka not as an immediate reaction to something a player has done, will have to be time sensitive. Some evil monster has cast a spell on you but must wait 30 seconds before doing it again... I think I'll probably be adding all these events to some kind of event queue, but how can I make that event queue time sensitive?

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• Are these two functions the same?

  - by Ranhiru

  There is a function in the AES algorithm, to multiply a byte by 2 in Galois Field. This is the function given in a website private static byte gfmultby02(byte b) { if (b < 0x80) return (byte)(int)(b <<1); else return (byte)( (int)(b << 1) ^ (int)(0x1b) ); } This is the function i wrote. private static byte MulGF2(byte x) { if (x < 0x80) return (byte)(x << 1); else { return (byte)((x << 1) ^ 0x1b); } } What i need to know is, given any byte whether this will perform in the same manner. Actually I am worried about the extra conversion of to int and then again to byte. So far I have tested and it looks fine. Does the extra cast to int and then to byte make a difference?

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• Trying to write priority queue in Java but getting "Exception in thread "main" java.lang.ClassCastEx

  - by Dan

  For my data structure class, I am trying to write a program that simulates a car wash and I want to give fancy cars a higher priority than regular ones using a priority queue. The problem I am having has something to do with Java not being able to type cast "Object" as an "ArrayQueue" (a simple FIFO implementation). What am I doing wrong and how can I fix it? public class PriorityQueue<E> { private ArrayQueue<E>[] queues; private int highest=0; private int manyItems=0; public PriorityQueue(int h) { highest=h; queues = (ArrayQueue[]) new Object[highest+1]; <----problem is here } public void add(E item, int priority) { queues[priority].add(item); manyItems++; } public boolean isEmpty( ) { return (manyItems == 0); } public E remove() { E answer=null; int counter=0; do { if(!queues[highest-counter].isEmpty()) { answer = queues[highest-counter].remove(); counter=highest+1; } else counter++; }while(highest-counter>=0); return answer; } }

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• How to use Comparator in Java to sort

  - by Dan

  I learned how to use the comparable but I'm having difficulty with the Comparator. I am having a error in my code: Exception in thread "main" java.lang.ClassCastException: New.People cannot be cast to java.lang.Comparable at java.util.Arrays.mergeSort(Unknown Source) at java.util.Arrays.sort(Unknown Source) at java.util.Collections.sort(Unknown Source) at New.TestPeople.main(TestPeople.java:18) Here is my code: import java.util.Comparator; public class People implements Comparator{ private int id; private String info; private double price; public People(int newid, String newinfo, double newprice){ setid(newid); setinfo(newinfo); setprice(newprice); } public int getid() { return id; } public void setid(int id) { this.id = id; } public String getinfo() { return info; } public void setinfo(String info) { this.info = info; } public double getprice() { return price; } public void setprice(double price) { this.price = price; } public int compare(Object obj1, Object obj2) { Integer p1 = ((People)obj1).getid(); Integer p2 = ((People)obj2).getid(); if (p1 p2 ){ return 1; } else if (p1 < p2){ return -1; } else return 0; } } import java.util.ArrayList; import java.util.Collections; public class TestPeople { public static void main(String[] args) { ArrayList peps = new ArrayList(); peps.add(new People(123, "M", 14.25)); peps.add(new People(234, "M", 6.21)); peps.add(new People(362, "F", 9.23)); peps.add(new People(111, "M", 65.99)); peps.add(new People(535, "F", 9.23)); Collections.sort(peps); for(int i=0;i I believe it has to do something with the casting in the compare method but I was playing around with it and still could not find the solution

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• C# Type conversion between two similar Datatable objects

  - by Ali

  I have .NET project with sync framework and two separate Datasets for MS SQL and Compact SQL. in my base class I have a generic DataTable object. in my derived classed I assign Typed DataTable to the generic object based on whether the application is operating online or offline: example: if (online) _dataTable = new MSSQLDataSet.Customer; else _dataTable = new CompactSQLDataSet.Customer; Now every where in my code i have to check and do a cast based on the current network mode like this: public void changeCustomerID(int ID) { if (online) (MSSQLDataSet.CustomerDataTable)_dataTable)[i].CustomerID = value; else (CompactMSSQLDataSet.CustomerDataTable)_dataTable)[i].CustomerID = value; } but I don't think this is very efficient and I believe it can be done in a smarter way to only use one line of code by dynamically getting the Type of _dataTable on the run time. my problem is at the design time, in order to acess datatable porperties such as "CustomerID" it has to be casted to either MSSQLDataSet.CustomerDataTable or CompactMSSQLDataSet.CustomerDataTable. Is there a way to have a function or a operator to convert the _datatable to its runtime type but still be able to use it's design time properties which are the same between the two types? something like: ((aType)_dataTable)[i].CustomerID = value; //or GetRuntimeType(_dataTable)[i].CustomerID = value;

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• Is there a general-purpose printf-ish routine defined in any C standard

  - by supercat

  In many C libraries, there is a printf-style routine which is something like the following: int __vgprintf(void *info, (void)(*print_function(void*, char)), const char *format, va_list params); which will format the supplied string and call print_function with the passed-in info value and each character in sequence. A function like fprintf will pass __vgprintf the passed-in file parameter and a pointer to a function which will cast its void* to a FILE* and output the passed-in character to that file. A function like snprintf will create a struct holding a char* and length, and pass the address of that struct to a function which will output each character in sequence, space permitting. Is there any standard for such a function, which could be used if e.g. one wanted a function to output an arbitrary format to a TCP port? A common approach is to allocate a buffer one hopes is big enough, use snprintf to put the data there, and then output the data from the buffer. It would seem cleaner, though, if there were a standard way to to specify that the print formatter should call a user-supplied routine with each character.

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• creating new instance fails PHP

  - by as3isolib

  I am relatively new to PHP and having some decent success however I am running into this issue: If I try to create a new instance of the class GenericEntryVO, I get a 500 error with little to no helpful error information. However, if I use a generic object as the result, I get no errors. I'd like to be able to cast this object as a GenericEntryVO as I am using AMFPHP to communicate serialize data with a Flex client. I've read a few different ways to create constructors in PHP but the typical 'public function Foo()' for a class Foo was recommended for PHP 5.4.4 //in my EntryService.php class public function getEntryByID($id) { $link = mysqli_connect("localhost", "root", "root", "BabyTrackingAppDB"); if (mysqli_connect_errno()) { printf("Connect failed: %s\n", mysqli_connect_error()); exit(); } $query = "SELECT * FROM Entries WHERE id = '$id' LIMIT 1"; if ($result = mysqli_query($link, $query)) { // $entry = new GenericEntryVO(); this is where the problem lies! while ($row = mysqli_fetch_row($result)) { $entry->id = $row[0]; $entry->entryType = $row[1]; $entry->title = $row[2]; $entry->description = $row[3]; $entry->value = $row[4]; $entry->created = $row[5]; $entry->updated = $row[6]; } } mysqli_free_result($result); mysqli_close($link); return $entry; } //my GenericEntryVO.php class <?php class GenericEntryVO { public function __construct() { } public $id; public $title; public $entryType; public $description; public $value; public $created; public $updated; // public $properties; } ?>

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• Howto use predicates in LINQ to Entities for Entity Framework objects

  - by user274947

  I'm using LINQ to Entities for Entity Framework objects in my Data Access Layer. My goal is to filter as much as I can from the database, without applying filtering logic on in-memory results. For that purpose Business Logic Layer passes a predicate to Data Access Layer. I mean Func<MyEntity, bool> So, if I use this predicate directly, like public IQueryable<MyEntity> GetAllMatchedEntities(Func<MyEntity, Boolean> isMatched) { return qry = _Context.MyEntities.Where(x => isMatched(x)); } I'm getting the exception [System.NotSupportedException] --- {"The LINQ expression node type 'Invoke' is not supported in LINQ to Entities."} Solution in that question suggests to use AsExpandable() method from LINQKit library. But again, using public IQueryable<MyEntity> GetAllMatchedEntities(Func<MyEntity, Boolean> isMatched) { return qry = _Context.MyEntities.AsExpandable().Where(x => isMatched(x)); } I'm getting the exception Unable to cast object of type 'System.Linq.Expressions.FieldExpression' to type 'System.Linq.Expressions.LambdaExpression' Is there way to use predicate in LINQ to Entities query for Entity Framework objects, so that it is correctly transformed it into a SQL statement. Thank you.

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• Would making plain int 64-bit break a lot of reasonable code?

  - by R..

  Until recently, I'd considered the decision by most systems implementors/vendors to keep plain int 32-bit even on 64-bit machines a sort of expedient wart. With modern C99 fixed-size types (int32_t and uint32_t, etc.) the need for there to be a standard integer type of each size 8, 16, 32, and 64 mostly disappears, and it seems like int could just as well be made 64-bit. However, the biggest real consequence of the size of plain int in C comes from the fact that C essentially does not have arithmetic on smaller-than-int types. In particular, if int is larger than 32-bit, the result of any arithmetic on uint32_t values has type signed int, which is rather unsettling. Is this a good reason to keep int permanently fixed at 32-bit on real-world implementations? I'm leaning towards saying yes. It seems to me like there could be a huge class of uses of uint32_t which break when int is larger than 32 bits. Even applying the unary minus or bitwise complement operator becomes dangerous unless you cast back to uint32_t. Of course the same issues apply to uint16_t and uint8_t on current implementations, but everyone seems to be aware of and used to treating them as "smaller-than-int" types.

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• Setting Nullable Integer to String Containing Nothing yields 0

  - by Brian MacKay

  I've been pulling my hair out over some unexpected behavior from nullable integers. If I set an Integer to Nothing, it becomes Nothing as expected. If I set an Integer? to a String that is Nothing, it becomes 0! Of course I get this whether I explicitly cast the String to Integer? or not. I realize I could work around this pretty easily but I want to know what I'm missing. Dim NullString As String = Nothing Dim NullableInt As Integer? = CType(NullString, Integer?) 'Expected NullableInt to be Nothing, but it's 0! NullableInt = Nothing 'This works -- NullableInt now contains Nothing. How is this EDIT: Previously I had my code up here so without the explicit conversion to 'Integer?' and everyone seemed to be fixated on that. I want to be clear that this is not an issue that would have been caught by Option Strict On -- check out the accepted answer. This is a quirk of the string-to-integer conversion rules which predate nullable types, but still impact them.

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• StructureMap Open Generic Types

  - by Shane Fulmer

  I have the following classes: public interface IRenderer<T> { string Render(T obj); } public class Generic<T> { } public class SampleGenericRenderer<T> : IRenderer<Generic<T>> { public string Render(Generic<T> obj) { throw new NotImplementedException(); } } I would like to be able to call StructureMap with ObjectFactory.GetInstance<IRenderer<Generic<string>>>(); and receive SampleGenericRenderer<string>. I'm currently using the following registration and receiving this error when I call GetInstance. "Unable to cast object of type 'ConsoleApplication1.SampleGenericRenderer'1[ConsoleApplication1.Generic'1[System.String]]' to type 'ConsoleApplication1.IRenderer'1[ConsoleApplication1.Generic'1[System.String]]'." public class CoreRegistry : Registry { public CoreRegistry() { Scan(assemblyScanner => { assemblyScanner.AssemblyContainingType(typeof(IRenderer<>)); assemblyScanner.AddAllTypesOf(typeof(IRenderer<>)); assemblyScanner.ConnectImplementationsToTypesClosing(typeof(IRenderer<>)); }); } } Is there any way to configure StructureMap so that it creates SampleGenericRenderer<string> instead of SampleGenericRenderer<Generic<string>>?

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• Help with Java Generics: Cannot use "Object" as argument for "? extends Object"

  - by AniDev

  Hello, I have the following code: import java.util.*; public class SellTransaction extends Transaction { private Map<String,? extends Object> origValueMap; public SellTransaction(Map<String,? extends Object> valueMap) { super(Transaction.Type.Sell); assignValues(valueMap); this.origValueMap=valueMap; } public SellTransaction[] splitTransaction(double splitAtQuantity) { Map<String,? extends Object> valueMapPart1=origValueMap; valueMapPart1.put(nameMappings[3],(Object)new Double(splitAtQuantity)); Map<String,? extends Object> valueMapPart2=origValueMap; valueMapPart2.put(nameMappings[3],((Double)origValueMap.get(nameMappings[3]))-splitAtQuantity); return new SellTransaction[] {new SellTransaction(valueMapPart1),new SellTransaction(valueMapPart2)}; } } The code fails to compile when I call valueMapPart1.put and valueMapPart2.put, with the error: The method put(String, capture#5-of ? extends Object) in the type Map is not applicable for the arguments (String, Object) I have read on the Internet about generics and wildcards and captures, but I still don't understand what is going wrong. My understanding is that the value of the Map's can be any class that extends Object, which I think might be redundant, because all classes extend Object. And I cannot change the generics to something like ? super Object, because the Map is supplied by some library. So why is this not compiling? Also, if I try to cast valueMap to Map<String,Object>, the compiler gives me that 'Unchecked conversion' warning. Thanks!

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• Slope requires a real as parameter 2?

  - by Dave Jarvis

  Question How do you pass the correct value to udf_slope's second parameter type? Attempts CAST(Y.YEAR AS FLOAT), but that failed (SQL error). Y.YEAR + 0.0, but that failed, too (see error message). slope(D.AMOUNT, 1.0), failed as well Error Message Using udf_slope fails due to: Can't initialize function 'slope'; slope() requires a real as parameter 2 Code SELECT D.AMOUNT, Y.YEAR, slope(D.AMOUNT, Y.YEAR + 0.0) as SLOPE, intercept(D.AMOUNT, Y.YEAR + 0.0) as INTERCEPT FROM YEAR_REF Y, DAILY D Here, D.AMOUNT is a FLOAT and Y.YEAR is an INTEGER. Create Function The slope function was created as follows: CREATE AGGREGATE FUNCTION slope RETURNS REAL SONAME 'udf_slope.so'; Function Signature From udf_slope.cc: double slope( UDF_INIT* initid, UDF_ARGS* args, char* is_null, char* is_error ) Example Usages Reading the fine manual reveals: UDF intercept() Calculates the intercept of the linear regression of two sets of variables. Function name intercept Input parameter(s) 2 (dependent variable: REAL, independent variable: REAL) Examples SELECT intercept(income,age) FROM customers UDF slope() Calculates the slope of the linear regression of two sets of variables. Function name slope Input parameter(s) 2 (dependent variable: REAL, independent variable: REAL) Examples SELECT slope(income,age) FROM customers Thoughts? Thank you!

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