collections

问题 I need to inherit a collection of items of the current type, like this class A { // some properties... public ICollection<A> Children; } class B: A { // other properties } This mostly works as expected. The problem is I can do something like this class C: A { } B b = new B(); b.Children = new List<C>(); Is there any way to force b.Children to be a collection of B ? 回答1: No, there is no way to do such thing yet. The C# language has no artifact to declare such thing: class A { public

问题 I need to inherit a collection of items of the current type, like this class A { // some properties... public ICollection<A> Children; } class B: A { // other properties } This mostly works as expected. The problem is I can do something like this class C: A { } B b = new B(); b.Children = new List<C>(); Is there any way to force b.Children to be a collection of B ? 回答1: No, there is no way to do such thing yet. The C# language has no artifact to declare such thing: class A { public

问题 I need to inherit a collection of items of the current type, like this class A { // some properties... public ICollection<A> Children; } class B: A { // other properties } This mostly works as expected. The problem is I can do something like this class C: A { } B b = new B(); b.Children = new List<C>(); Is there any way to force b.Children to be a collection of B ? 回答1: No, there is no way to do such thing yet. The C# language has no artifact to declare such thing: class A { public

问题 I wanted to have your opinion on what is the best way to manage time series in c# according to you. I need to have a 2 dimensions matrix-like with Datetime object as an index of rows (ordered and without duplicate) and each columns would represent the stock value for the relevant Datetime. I would like to know if any of those objects would be able to handle missing data for a date: adding a column or a time serie would add the missing date in the row index and would add "null" or "N/a" for

问题 When I am trying to convert, I am getting below exception java.lang.ArrayStoreException: java.util.HashSet at java.util.AbstractCollection.toArray(Unknown Source) This is my code Map<String, Set<String>> map = new HashMap<>(); String[] keySet = map.keySet().toArray(new String[map.size()]); Collection<Set<String>> collections = map.values(); String[] values = collection.toArray(new String[collection.size()]);// In this line getting Exception 回答1: You can simply use Stream.flatMap as you stream

问题 When I am trying to convert, I am getting below exception java.lang.ArrayStoreException: java.util.HashSet at java.util.AbstractCollection.toArray(Unknown Source) This is my code Map<String, Set<String>> map = new HashMap<>(); String[] keySet = map.keySet().toArray(new String[map.size()]); Collection<Set<String>> collections = map.values(); String[] values = collection.toArray(new String[collection.size()]);// In this line getting Exception 回答1: You can simply use Stream.flatMap as you stream

问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 4 years ago . Improve this question /* I have a list of employees */ List<Employee> empList=new ArrayList<Employee>(); empList.add(employee1); empList.add(employee2); empList.add(employee3); empList.add(employee4); /* I have taken an iterator */ Iterator<Employee> empIterator=empList.iterator()

问题 I have Java code containing a TreeSet . I want to convert the code to C#. Which equivalent collection can I use? If there is none please suggest alternatives. 回答1: I think there is no treeset in C#. There was similar question asked in msdn, check that may be useful. http://social.msdn.microsoft.com/forums/en-US/netfxbcl/thread/823c46ca-4a60-4429-a606-e76c3195d4cc/ 回答2: That would be System.Collections.Generic.SortedSet<T>. It does have the methods and complexity guarantees that one would

问题 I made a program with python and mongodb to do some diaries. Like this Sometimes I want to delete the last sentence, just by typing "delete!" But I dont know how to delete in a samrt way. I dont want to use "skip". Is there a good way to do it? 回答1: Be it first or last item, MongoDB maintains unique _id key for each record and thus you can just pass that id field in your delete query either using deleteOne() or deleteMany() . Since only one record to delete you need to use deleteOne() like db

问题 This question already has answers here : Java 8 Streams peek api (4 answers) Closed 2 years ago . In java 8, I am using Streams to print the output, but size is coming as 0. Why? public class IntermediateryAndFinal { public static void main(String[] args) { Stream<String> stream = Stream.of("one", "two", "three", "four", "five"); Predicate<String> p1 = Predicate.isEqual("two"); Predicate<String> p2 = Predicate.isEqual("three"); List<String> list = new ArrayList<>(); stream.peek(System.out: