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  • Java LinkedList iterator being exhausted prematurely

    - by Sujeet
    I am using LinkedList and retrieving an Iterator object by using list.iterator(). After that, I am checking it.hasNext(), real issue is while checking it.hasNext(), sometimes it returns false. I need help why this is happening, though I have elements in the list. Some code: public synchronized void check(Object obj) throws Exception { Iterator itr = list.iterator(); while(itr.hasNext()) { //This Line I get false.. though i have list size is 1 Item p = (Item)itr.next(); if(p.getId() == null) {continue;} if(p.getId().getElemntId() == obj.getId() || obj.getId() == 0 ) { p.setResponse(obj); notifyAll(); return; } } Log.Error("validate failed obj.getId="+obj.getId()+" **list.size="+list.size()*This shows 1*); throw new Exception("InvalidData"); }

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  • How can I make three partials into just one in rails where the :collection is the same?

    - by Angela
    I have three partials that I'd like to consolidate into one. They share the same collection, but each gets passed its own :local variable. Those variables are used for specific Models, so as a result, I have three different calls to the partial and three different partials. Here's the repetitive code: <% for email in campaign.emails %> <h4><%= link_to email.title, email %> <%= email.days %> days</h4> <% @contacts= campaign.contacts.find(:all, :order => "date_entered ASC" )%> <!--contacts collection--> <!-- render the information for each contact --> <%= render :partial => "contact_email", :collection => @contacts, :locals => {:email => email} %> <% end %> Calls in this Campaign: <% for call in campaign.calls %> <h4><%= link_to call.title, call %> <%= call.days %> days</h4> <% @contacts= campaign.contacts.find(:all, :order => "date_entered ASC" )%> <!--contacts collection--> <!-- render the information for each contact --> <%= render :partial => "contact_call", :collection => @contacts, :locals => {:call => call} %> <% end %> Letters in this Campaign: <% for letter in campaign.letters %> <h4><%= link_to letter.title, letter %> <%= letter.days %> days</h4> <% @contacts= campaign.contacts.find(:all, :order => "date_entered ASC" )%> <!--contacts collection--> <!-- render the information for each contact --> <%= render :partial => "contact_letter", :collection => @contacts, :locals => {:letter => letter} %> <% end %> An example of one of the partials is as follows: < div id="contact_email_partial"> <% if from_today(contact_email, email.days) < 0 %> <% if show_status(contact_email, email) == 'no status'%> <p> <%= full_name(contact_email) %> <% unless contact_email.statuses.empty?%> (<%= contact_email.statuses.find(:last).status%>) <% end %> is <%= from_today(contact_email,email.days).abs%> days overdue: <%= do_event(contact_email, email) %> <%= link_to_remote "Skip Email Remote", :url => skip_contact_email_url(contact_email,email), :update => "update-area-#{contact_email.id}-#{email.id}" %> <span id='update-area-<%="#{contact_email.id}-#{email.id}"%>'> </span> <% end %> <% end %> </div>

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  • Difference between a Deprecated and an Legacy API?

    - by Vaibhav Bajpai
    I was studying the legacy API's in the Java's Collection Framework and I learnt that classes such as Vector and HashTable have been superseded by ArrayList and HashMap. However still they are NOT deprecated, and deemed as legacy when essentially, deprecation is applied to software features that are superseded and should be avoided, so, I am not sure when is a API deemed legacy and when it is deprecated.

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  • best scala idiom for find & return

    - by IttayD
    This is something I encounter frequently, but I don't know the elegant way of doing. I have a collection of Foo objects. Foo has a method bar() that may return null or a Bar object. I want to scan the collection, calling each object's bar() method and stop on the first one returning an actual reference and return that reference from the scan. Obviously: foos.find(_.bar != null).bar does the trick, but calls #bar twice.

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  • Html.Editor() helper in ASP.NET MVC 3 does not work as expected with array in model

    - by SlimShaggy
    In my ASP.NET MVC 3 application I have classes like the following: public class Localization<T> { public int VersionID { get; set; } public T Value { get; set; } ... } public class Localizable<T> { public Localization<T>[] Name { get; set; } ... } Then, I have the following view: @model dynamic ... @for (int i = 0; i < VersionCount; i++) { ... @Html.Editor(string.Format("Name[{0}.Value", i)) ... } Now, when I display this view, passing a subclass of Localizable<string> as the model, the textboxes for the strings are rendered, but they are empty. If I replace @Html.Editor(string.Format("Name[{0}.Value", i)) with @InputExtensions.TextBox(Html, string.Format("Name[{0}].Value", i), Model.Name[i].Value), the textboxes are correctly filled with values from the model. However, using TextBox instead of Editor is not an option for me, because I want to use different editor templates for different types of T. So, what am I doing wrong, or is it a bug in MVC, and is there any workaround?

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  • is this possible: c# collection of Type with constrains, or collection of generic type?

    - by Jon
    I'm trying to store types in a collection, so that i can later instantiate objects of the types in the collection. But I'm not sure how to do this the best way. What i have so far: List<Type> list = new List<Type>(); list.Add(typeof(MyClass)); var obj = (MyClass)Activator.CreateInstance(list[0]); I would like to have some constrains on the Type, or better yet, just a generic type in the collection instead of an instantiated Type object. Is this possible?

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  • Getting a java collection of objects in Alphabetical order

    - by MichaelMcCabe
    I have a question that I dont really know where to start. So I thought i'd ask it here. Basically, I have a drop down with names in it. I want these names to be in alphabetical order. Populating the drop down happens as follows; I query a database and pull down an Id and Name, make a object called "UserList", and set the name and id variables with what I get back. I then add this object to an ArrayList. I do this over and over. I then convert this collection to an array, and pass it to my JSP page using session.setAttribute("userList", UserList); I then populate the drop down as below. <c:forEach items="${usersCompanysList}" var="c" > There probably is a simple answer but how to I sort these names?

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  • How to initialize list with parent child relation

    - by user2917702
    Let's say I have the following classes. public class Parent { public string name; IList<Children> children; } public class Child { public string parentName; public int age; } As it is understandable, each parent can have multiple children, and we can have multiple parents. What is the best way to initialize these classes? Is it better to get all of the parents, and all of the children from database then use LINQ? IList<Parent> parents = GetParents()//assume this gets parents from db IList<Child> children = GetChildren() //assume this gets children from db foreach(Parent parent in parents) { parent.children = children.Where(x=>x.parentName==parent.name).ToList(); } or get all of the parents and iterate through each parent to query database by parentName to get children information? Due to requirement that I have, I cannot use datatable or dataset; I can only use datareader. IList<Parent> parents = GetParents()//assume this gets parents from db foreach(Parent parent in parents) { parent.children = GetChildrenByParentName();//assume this gets parents from db by parentName } Thank you

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  • List.ForEach method and collection interfaces

    - by tyndall
    In .NET 3.5 List< gains a ForEach method. I notice this does not exist on IList< or IEnumerable< what was the thinking here? Is there another way to do this? Nice and simple short way to do this? I ask because I was at a talk where the speaker said always use the more general interfaces. But why would I use IList< as a return type if I want to be able to turn around and use ForEach? Then I would just end up casting it back to a List<.

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  • Bind to a collection's view and just call ToString()

    - by womp
    I'm binding a GridView to a collection of objects that look like this: public class Transaction { public string PersonName { get; set; } public DateTime TransactionDate { get; set; } public MoneyCollection TransactedMoney { get; set;} } MoneyCollection simply inherits from ObservableCollection<T>, and is a collection of MyMoney type object. In my GridView, I just want to bind a column to the MoneyCollection's ToString() method. However, binding it directly to the TransactedMoney property makes every entry display the text "(Collection)", and the ToString() method is never called. I understand that it is binding to the collection's default view. So my question is - how can I make it bind to the collection in such a way that it calls the ToString() method on it? This is my first WPF project, so I know this might be a bit noobish, but pointers would be very welcome.

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  • Disable Adding Item to Collection

    - by Wonko the Sane
    Hi All, I'm sure there's an "easy" answer to this, but for the moment it escapes me. In an MVVM application, I have a property that is a ObservableCollection, used for displaying some set of elements on the view. private readonly ObservableCollection<MyType> mMyCollection = new ObservableCollection<MyType>(); public ObservableCollection<MyType> MyCollection { get { return mMyCollection; } } I want to restrict consumers of this collection from simply using the property to add to the collection (i.e. I want to prevent this from the view): viewModel.MyCollection.Add(newThing); // want to prevent this! Instead, I want to force the use of a method to add items, because there may be another thread using that collection, and I don't want to modify the collection while that thread is processing it. public void AddToMyCollection(MyType newItem) { // Do some thread/task stuff here } Thanks, wTs

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  • Java: Efficient Equivalent to Removing while Iterating a Collection

    - by Claudiu
    Hello everyone. We all know you can't do this: for (Object i : l) if (condition(i)) l.remove(i); ConcurrentModificationException etc... this apparently works sometimes, but not always. Here's some specific code: public static void main(String[] args) { Collection<Integer> l = new ArrayList<Integer>(); for (int i=0; i < 10; ++i) { l.add(new Integer(4)); l.add(new Integer(5)); l.add(new Integer(6)); } for (Integer i : l) { if (i.intValue() == 5) l.remove(i); } System.out.println(l); } This, of course, results in: Exception in thread "main" java.util.ConcurrentModificationException ...even though multiple threads aren't doing it... Anyway. What's the best solution to this problem? "Best" here means most time and space efficient (I realize you can't always have both!) I'm also using an arbitrary Collection here, not necessarily an ArrayList, so you can't rely on get.

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  • object reference set in java

    - by landon9720
    I need to create a Set of objects. The concern is I do not want to base the hashing or the equality on the objects' hashCode and equals implementation. Instead, I want the hash code and equality to be based only on each object's reference identity (i.e.: the value of the reference pointer). I'm not sure how to do this in Java. The reasoning behind this is my objects do not reliably implement equals or hashCode, and in this case reference identity is good enough.

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  • for (Object object : list) [java] construction

    - by EugeneP
    My question, is, whether the sequence of elements picked from a list will always be the same, is this construction behaviour is deterministic for java "List"s - descendants of java.util.List 2) question, if I use for(Object o: list) construction and inside the loop's body increment a variable, will it be the index of list's elements? So, how it goes through list's elements, from 0 to size()-1 or chaotically? List.get(i) will always return this element? 3) question ( I suppose for the 2-nd question the answer will be negative, so:) for (int i=0; i < list.size(); i++) { } is the best way if I need to save the index of an element and later get it back from a list by its id?

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  • .NET Garbage Collection behavior (with DataTable)

    - by gmac
    I am wonder why after creating a very simple DataTable and then setting it to null why Garbage Collection does not clear out all the memory used by that DataTable. Here is an example. The variable Before should be equal to Removed but it is not. { long Before = 0, After = 0, Removed = 0, Collected = 0; Before = GC.GetTotalMemory(true); DataTable dt = GetSomeDataTableFromSql(); After = GC.GetTotalMemory(true); dt = null; Removed = GC.GetTotalMemory(true); GC.Collect(); Collected = GC.GetTotalMemory(true); } Gives the following results. Before = 388116 After = 731248 Removed = 530176 Collected = 530176

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  • What is the time complexity of LinkedList.getLast() in Java?

    - by i.
    I have a private LinkedList in a Java class & will frequently need to retrieve the last element in the list. The lists need to scale, so I'm trying to decide whether I need to keep a reference to the last element when I make changes (to achieve O(1)) or if the LinkedList class does that already with the getLast() call. What is the big-O cost of LinkedList.getLast() and is it documented? (i.e. can I rely on this answer or should I make no assumptions & cache it even if it's O(1)?)

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  • C# Generic Collection help

    - by dcmovva
    I have a requirement to implement some kind of dictionary object. Something like MyDict<K,V1, V2). For example if I have a Question as Key(k) then Correct answer is V1 . V2 is user selected answer. Is there a collection that would satisfy this requirement in C#. If I have to design my own type, what interfaces should I implement. ICollection and Ilist ?

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