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  • C# StackOverflowException

    - by KSwift87
    Problem: I am trying to update a List. If a certain item's ID already exists in the List, I want to add onto that item's quantity. If not, then I want to add another item to the list. cart = (List<OrderItem>)Session["cart"]; for(int counter = cart.Count-1; counter >= 0; counter--) { if (cart[counter].productId == item.productId) { cart[counter].productQuantity += item.productQuantity; } else if (counter == 0) { cart.Add(item); } } "cart[counter]" and "item" represent an instance(s) of a custom object of mine. Currently when I finally find a matching ID, everything APPEARS as though it should work, but I get a StackOverflowException thrown in my custom object class. public int productQuantity { get { return _productQuantity; } set { productQuantity = value; } } It gets thrown right at the open-bracket of the "set". Could somebody please tell me what the heck is wrong because I've been going at this for the past 2+ hours to no avail. Thank you in advance.

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  • What causes this retainAll exception?

    - by Joren
    java.lang.UnsupportedOperationException: This operation is not supported on Query Results at org.datanucleus.store.query.AbstractQueryResult.contains(AbstractQueryResult.java:250) at java.util.AbstractCollection.retainAll(AbstractCollection.java:369) at namespace.MyServlet.doGet(MyServlet.java:101) I'm attempting to take one list I retrieved from a datastore query, and keep only the results which are also in a list I retrieved from a list of keys. Both my lists are populated as expected, but I can't seem to user retainAll on either one of them. // List<Data> listOne = new ArrayList(query.execute(theQuery)); // DatastoreService ds = DatastoreServiceFactory.getDatastoreService(); // List<Data> listTwo = new ArrayList(ds.get(keys).values()); // listOne.retainAll(listTwo);

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  • Saving jQuery UI Sortable's order to Backbone.js Collection

    - by VirtuosiMedia
    I have a Backbone.js collection that I would like to be able to sort using jQuery UI's Sortable. Nothing fancy, I just have a list that I would like to be able to sort. The problem is that I'm not sure how to get the current order of items after being sorted and communicate that to the collection. Sortable can serialize itself, but that won't give me the model data I need to give to the collection. Ideally, I'd like to be able to just get an array of the current order of the models in the collection and use the reset method for the collection, but I'm not sure how to get the current order. Please share any ideas or examples for getting an array with the current model order.

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  • Convert SelectedObjectCollection to Collection of Specific Type

    - by Jonathan Wood
    I have a WinForms multiselect listbox, and each item in the listbox is of type MyClass. I am also writing a method that needs to take a parameter that is a collection of MyClass. It could be of type MyClass[], List<MyClass>, IList<MyClass>, IEnumerable<MyClass>, etc. Any of those would work fine. Somehow, I need to pass the selected items in the listbox to my method. But how would I convert SelectedObjectCollection to any of the MyClass collection types described above?

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  • Using Google Common Collection in GWT

    - by Jeeyoung Kim
    This is a simple problem, but I'm having problems with it... I'm trying to use Google common collection's Objects.equal() method in a GWT client code, but I'm keep getting the error "20:12:10.001 [ERROR] [gwt_regex] Line 39: No source code is available for type com.google.common.base.Objects; did you forget to inherit a required module?" Tried to Google for the answer, but couldn't find any answer regarding this - everyone just said "Google collection should work off the box with GWT".

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  • Passing a comparator syntax help in Java

    - by Crystal
    I've tried this a couple ways, the first is have a class that implements comparator at the bottom of the following code. When I try to pass the comparat in sortListByLastName, I get a constructor not found error and I am not sure why import java.util.*; public class OrganizeThis implements WhoDoneIt { /** Add a person to the organizer @param p A person object */ public void add(Person p) { staff.put(p.getEmail(), p); //System.out.println("Person " + p + "added"); } /** * Remove a Person from the organizer. * * @param email The email of the person to be removed. */ public void remove(String email) { staff.remove(email); } /** * Remove all contacts from the organizer. * */ public void empty() { staff.clear(); } /** * Find the person stored in the organizer with the email address. * Note, each person will have a unique email address. * * @param email The person email address you are looking for. * */ public Person findByEmail(String email) { Person aPerson = staff.get(email); return aPerson; } /** * Find all persons stored in the organizer with the same last name. * Note, there can be multiple persons with the same last name. * * @param lastName The last name of the persons your are looking for. * */ public Person[] find(String lastName) { ArrayList<Person> names = new ArrayList<Person>(); for (Person s : staff.values()) { if (s.getLastName() == lastName) { names.add(s); } } // Convert ArrayList back to Array Person nameArray[] = new Person[names.size()]; names.toArray(nameArray); return nameArray; } /** * Return all the contact from the orgnizer in * an array sorted by last name. * * @return An array of Person objects. * */ public Person[] getSortedListByLastName() { PersonLastNameComparator comp = new PersonLastNameComparator(); Map<String, Person> sorted = new TreeMap<String, Person>(comp); ArrayList<Person> sortedArrayList = new ArrayList<Person>(); for (Person s: sorted.values()) { sortedArrayList.add(s); } Person sortedArray[] = new Person[sortedArrayList.size()]; sortedArrayList.toArray(sortedArray); return sortedArray; } private Map<String, Person> staff = new HashMap<String, Person>(); public static void main(String[] args) { OrganizeThis testObj = new OrganizeThis(); Person person1 = new Person("J", "W", "111-222-3333", "[email protected]"); Person person2 = new Person("K", "W", "345-678-9999", "[email protected]"); Person person3 = new Person("Phoebe", "Wang", "322-111-3333", "[email protected]"); Person person4 = new Person("Nermal", "Johnson", "322-342-5555", "[email protected]"); Person person5 = new Person("Apple", "Banana", "123-456-1111", "[email protected]"); testObj.add(person1); testObj.add(person2); testObj.add(person3); testObj.add(person4); testObj.add(person5); System.out.println(testObj.findByEmail("[email protected]")); System.out.println("------------" + '\n'); Person a[] = testObj.find("W"); for (Person p : a) System.out.println(p); System.out.println("------------" + '\n'); a = testObj.find("W"); for (Person p : a) System.out.println(p); System.out.println("SORTED" + '\n'); a = testObj.getSortedListByLastName(); for (Person b : a) { System.out.println(b); } System.out.println(testObj.getAuthor()); } } class PersonLastNameComparator implements Comparator<Person> { public int compare(Person a, Person b) { return a.getLastName().compareTo(b.getLastName()); } } And then when I tried doing it by creating an anonymous inner class, I also get a constructor TreeMap cannot find symbol error. Any thoughts? inner class method: public Person[] getSortedListByLastName() { //PersonLastNameComparator comp = new PersonLastNameComparator(); Map<String, Person> sorted = new TreeMap<String, Person>(new Comparator<Person>() { public int compare(Person a, Person b) { return a.getLastName().compareTo(b.getLastName()); } }); ArrayList<Person> sortedArrayList = new ArrayList<Person>(); for (Person s: sorted.values()) { sortedArrayList.add(s); } Person sortedArray[] = new Person[sortedArrayList.size()]; sortedArrayList.toArray(sortedArray); return sortedArray; }

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  • joining / merging two arrays

    - by Shishant
    I have two arrays like this, actually this is mysql data retrieved from two different servers: $array1 = array ( 0 => array ( 'id' => 1, 'name' => 'somename') , 1 => array ( 'id' => 2, 'name' => 'somename2') ); $array2 = array ( 0 => array ( 'thdl_id' => 1, 'otherdate' => 'spmethings') , 1 => array ( 'thdl_id' => 2, 'otherdate' => 'spmethings22') ); how can i join / merge array so it looks like this $new_array = array ( 0 => array ( 'id' => 1, 'name' => 'somename', 'otherdate' => 'spmethings') , 1 => array ( 'id' => 2, 'name' => 'somename2', 'otherdate' => 'spmethings22') );

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  • What is a practical, real world example of the Linked List?

    - by JStims
    I understand the definition of a Linked List, but how can it be represented and related to a common concept or item? For example, inheritance in OOP can be related to automobiles. All (most) automobiles in real life are the essentially same thing; an automobile has an Engine, you can start() it, you can make the car go(), stop() and so on. An automobile would typically have a maximum passenger capacity but it would differ between a Bus and a SportsCar, which are both automobiles. Is there some real life, intuitive example of the plain ole' singly Linked List like we have with inheritance? The typical textbook Linked List example shows a node with an integer and a pointer to the next, and it just doesn't seem very useful. Your input is appreciated.

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  • VB.net: Is my Thread Safe List Solution actually safe?

    - by Shiftbit
    I've added teh following Extensions to my Project in order to create a thread safe list: Extensions If I want to conduct a simple operation on my list <Extension()> _ Public Sub Action(Of T)(ByVal list As List(Of T), ByVal action As Action(Of List(Of T))) SyncLock (list) action(list) End SyncLock End Sub If I want to pass it more than one parameter I could simply extend it with more items... <Extension()> _ Public Sub Action(Of T)(ByVal list As List(Of T), ByVal action As Action(Of List(Of T), T), ByVal item As T) SyncLock (list) Action(list, item) End SyncLock End Sub Actions I have created the following Action Examples: Private Sub Read(Of T)(ByVal list As List(Of T)) Console.WriteLine("Read") For Each item As T In list Console.WriteLine(item.ToString) Thread.Sleep(10) Next End Sub and also one that takes a parameter: Private Sub Write(Of T)(ByVal list As List(Of T), ByVal item As T) Thread.Sleep(100) list.Add(item) Console.WriteLine("Write") End Sub Initiating Then in my various threads I will call my Actions with: list.Action(AddressOf Read) or list.Action(AddressOf Write2, 10) Are these Extenxion methods thread safe or do you have other recommendations?

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  • How to work threading with ConcurrentQueue<T>.

    - by dboarman
    I am trying to figure out what the best way of working with a queue will be. I have a process that returns a DataTable. Each DataTable, in turn, is merged with the previous DataTable. There is one problem, too many records to hold until the final BulkCopy (OutOfMemory). So, I have determined that I should process each incoming DataTable immediately. Thinking about the ConcurrentQueue<T>...but I don't see how the WriteQueuedData() method would know to dequeue a table and write it to the database. For instance: public class TableTransporter { private ConcurrentQueue<DataTable> tableQueue = new ConcurrentQueue<DataTable>(); public TableTransporter() { tableQueue.OnItemQueued += new EventHandler(WriteQueuedData); // no events available } public void ExtractData() { DataTable table; // perform data extraction tableQueue.Enqueue(table); } private void WriteQueuedData(object sender, EventArgs e) { BulkCopy(e.Table); } } My first question is, aside from the fact that I don't actually have any events to subscribe to, if I call ExtractData() asynchronously will this be all that I need? Second, is there something I'm missing about the way ConcurrentQueue<T> functions and needing some form of trigger to work asynchronously with the queued objects?

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  • Create and populate two-dimensional array in Scala

    - by ~asteinlein
    What's the recommended way of creating a pre-populated two-dimensional array in Scala? I've got the following code: val map = for { x <- (1 to size).toList } yield for { y <- (1 to size).toList } yield (x, y) How do I make an array instead of list? Replacing .toList with .toArray doesn't compile. And is there a more concise or readable way of doing this than the nested for expressions?

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  • Quickly retrieve the subset of properties used in a huge collection in C#

    - by ccornet
    I have a huge Collection (which I can cast as an enumerable using OfType<()) of objects. Each of these objects has a Category property, which is drawn from a list somewhere else in the application. This Collection can reach sizes of hundreds of items, but it is possible that only, say, 6/30 of the possible Categories are actually used. What is the fastest method to find these 6 Categories? The size of the huge Collection discourages me from just iterating across the entire thing and returning all unique values, so is there a faster method of accomplishing this? Ideally I'd collect the categories into a List.

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  • Clojure: seq (cons) vs. list (conj)

    - by dbyrne
    I know that cons returns a seq and conj returns a collection. I also know that conj "adds" the item to the optimal end of the collection, and cons always "adds" the item to the front. This example illustrates both of these points: user=> (conj [1 2 3] 4) //returns a collection [1 2 3 4] user=> (cons 4 [1 2 3]) //returns a seq (4 1 2 3) For vectors, maps, and sets these differences make sense to me. However, for lists they seem identical. user=> (conj '(3 2 1) 4) (4 3 2 1) user=> (cons 4 '(3 2 1)) (4 3 2 1) Are there any examples using lists where conj vs. cons exhibit different behaviors, or are they truly interchangeable? Phrased differently, is there an example where a list and a seq cannot be used equivalently?

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  • Best data-structure to use for two ended sorted list

    - by fmark
    I need a collection data-structure that can do the following: Be sorted Allow me to quickly pop values off the front and back of the list Remain sorted after I insert a new value Allow a user-specified comparison function, as I will be storing tuples and want to sort on a particular value Thread-safety is not required Optionally allow efficient haskey() lookups (I'm happy to maintain a separate hash-table for this though) My thoughts at this stage are that I need a priority queue and a hash table, although I don't know if I can quickly pop values off both ends of a priority queue. I'm interested in performance for a moderate number of items (I would estimate less than 200,000). Another possibility is simply maintaining an OrderedDictionary and doing an insertion sort it every-time I add more data to it. Furthermore, are there any particular implementations in Python. I would really like to avoid writing this code myself.

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  • Is there a SortedList<T> class in .net ? (not SortedList<Key,Value> which is actually a kind of Sort

    - by Brann
    I need to sort some objects according to their contents (in fact according to one of their properties, which is NOT the key and may be duplicated between different objects) .net provides two classes (SortedDictionnary and SortedList), and both are some kind of Dictionaries. The only difference (AFAIK) is that SortedDictionnary uses a binary tree to maintain its state whereas SortedList does not and is accessible via an index. I could achieve what I want using a List, and then using its Sort() method with a custom implementation of IComparer, but it wouldn't be time-efficient as I would sort the whole List each time I insert a new object, whereas a good SortedList would just insert the item at the right position. What I need is a SortedList class with a RefreshPosition(int index) to move only the changed (or inserted) object rather than resorting the whole list each time an object inside changes. Am I missing something obvious ?

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  • How to change order in ordered+persisted collection?

    - by Jaroslav Záruba
    I just need to change order of items in a (previously persisted) ordered collection... I tried simply passing the re-arranged collection to a setter: after committing a transaction the collection is gone. Then I tried to clear() the existing collection and addAll() afterwards: clear() makes persistent manager to mark all the elements as deleted. (But obviously I would like to be able to work with the collection items in the very transaction.) (The collection is not in a default fetch group, so I tried the above also with the named fetch group added into the fetch plan. No luck.) This must be the most stupid question, but I ran out of ideas and I'm stuck here two days already. I swear I googled. :(

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  • Java: How to workaround the lack of Equatable interface?

    - by java.is.for.desktop
    Hello, everyone! As far as I know, things such as SortedMap or SortedSet, use compareTo (rather than equals) on Comparable<?> types for checking equality (contains, containsKey). But what if certain types are equatable by concept, but not comparable? I have to declare a Comparator<?> and override the method int compareTo(T o1, To2). OK, I can return 0 for instances which are considered equal. But, for unqeual instances, what do I return when an order is not evident? Is the approach of using SortedMap or SortedSet on equatable but (by concept) not comparable types good anyway? Thank you! EDIT: I don't want to store things sorted, but would I use "usual" Map and Set, I couldn't "override" the equality-behavior. EDIT 2: Why I can't just override equals(...): I need to alter the equality-behavior of a foreign class. Can't edit it. EDIT 3: Just think of .NET: They have IEquatable interface which cat alter the equality-behavior without touching the comparable behavior.

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  • fail-fast iterator

    - by joy
    I get this definition : As name suggest fail-fast Iterators fail as soon as they realized that structure of Collection has been changed since iteration has begun. what it mean by since iteration has begun? is that mean after Iterator it=set.iterator() this line of code? public static void customize(BufferedReader br) throws IOException{ Set<String> set=new HashSet<String>(); // Actual type parameter added **Iterator it=set.iterator();**

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  • Creating a blocking Queue<T> in .NET?

    - by spoon16
    I have a scenario where I have multiple threads adding to a queue and multiple threads reading from the same queue. If the queue reaches a specific size all threads that are filling the queue will be blocked on add until an item is removed from the queue. The solution below is what I am using right now and my question is: How can this be improved? Is there an object that already enables this behavior in the BCL that I should be using? internal class BlockingCollection<T> : CollectionBase, IEnumerable { //todo: might be worth changing this into a proper QUEUE private AutoResetEvent _FullEvent = new AutoResetEvent(false); internal T this[int i] { get { return (T) List[i]; } } private int _MaxSize; internal int MaxSize { get { return _MaxSize; } set { _MaxSize = value; checkSize(); } } internal BlockingCollection(int maxSize) { MaxSize = maxSize; } internal void Add(T item) { Trace.WriteLine(string.Format("BlockingCollection add waiting: {0}", Thread.CurrentThread.ManagedThreadId)); _FullEvent.WaitOne(); List.Add(item); Trace.WriteLine(string.Format("BlockingCollection item added: {0}", Thread.CurrentThread.ManagedThreadId)); checkSize(); } internal void Remove(T item) { lock (List) { List.Remove(item); } Trace.WriteLine(string.Format("BlockingCollection item removed: {0}", Thread.CurrentThread.ManagedThreadId)); } protected override void OnRemoveComplete(int index, object value) { checkSize(); base.OnRemoveComplete(index, value); } internal new IEnumerator GetEnumerator() { return List.GetEnumerator(); } private void checkSize() { if (Count < MaxSize) { Trace.WriteLine(string.Format("BlockingCollection FullEvent set: {0}", Thread.CurrentThread.ManagedThreadId)); _FullEvent.Set(); } else { Trace.WriteLine(string.Format("BlockingCollection FullEvent reset: {0}", Thread.CurrentThread.ManagedThreadId)); _FullEvent.Reset(); } } }

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