generics

问题 I am wondering what is wrong with this code: Map <? extends String, ? extends Integer> m = null; Set<Map.Entry<? extends String, ? extends Integer>> s = m.entrySet(); The compiler complains with the error message: Type mismatch: cannot convert from Set<Map.Entry<capture#1-of ? extends String,capture#2-of ? extends Integer>> to Set<Map.Entry<? extends String,? extends Integer>> What should the type of s be? Eclipse suggests Set<?> but I am trying to get more specific than that. 回答1: This issue

问题 I am trying to create a function that takes in a object property and returns back object property. How to get the property values into this specific Function, so that this function only takes takes in the object's specific property and not the entire object? class Program { public T MapFrom<T,V>(T SourceObject.property, V DestinationObject.Property) //Not able to achieve this// { // Code to Map Property } // Here I want to specifically pass only one property of Object , not the entire one

问题 I am trying to create a function that takes in a object property and returns back object property. How to get the property values into this specific Function, so that this function only takes takes in the object's specific property and not the entire object? class Program { public T MapFrom<T,V>(T SourceObject.property, V DestinationObject.Property) //Not able to achieve this// { // Code to Map Property } // Here I want to specifically pass only one property of Object , not the entire one

问题 I am trying to create a function that takes in a object property and returns back object property. How to get the property values into this specific Function, so that this function only takes takes in the object's specific property and not the entire object? class Program { public T MapFrom<T,V>(T SourceObject.property, V DestinationObject.Property) //Not able to achieve this// { // Code to Map Property } // Here I want to specifically pass only one property of Object , not the entire one

问题 Let's say I have a manufacturing scheduling system, which is made up of four parts: There are factories that can manufacture a certain type of product and know if they are busy: interface Factory<ProductType> { void buildProduct(ProductType product); boolean isBusy(); } There is a set of different products, which (among other things) know in which factory they are built: interface Product<ActualProductType extends Product<ActualProductType>> { Factory<ActualProductType> getFactory(); } Then

问题 Magical error appears when trying to create guava cache: import com.google.common.cache.CacheBuilder; import com.google.common.cache.CacheLoader; import java.util.concurrent.ConcurrentMap; public class Main { private static ConcurrentMap<Long, Object> cache = CacheBuilder .newBuilder() .build(new CacheLoader<Long, Object>() { @Override public Object load(Long key) throws Exception { return null; } }).asMap(); } java compile error: Error:(17, 21) java: C:\JavaWorkspace\untitled\src\...\Main

问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 4 years ago . I want to write a function that can input an iterator over a given generic type in a typesafe way. One possible use case would be writing a function like accumulate/map/fold: #include <iterator> #include <vector> #include <functional> template <typename V, typename K> K accumulate( std::function<K

问题 If I comment out my static class this compiles fine. However i'd like to have the static class working so I can use the first commented out line in main. My error is error CS0314: The type 'T' cannot be used as type parameter 'T' in the generic type or method 'DateTest.Range'. There is no boxing conversion or type parameter conversion from 'T' to 'System.IComparable'. My source is using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading

问题 I've had several problems with the plus operator so I decided to investigate and ended up with the following minimal example. When I compile func f<T>(t: T) -> [T] { return [t] + [t] } everything is fine. The compiler chooses this overload of the plus operator: public func +<RRC1 : RangeReplaceableCollection, RRC2 : RangeReplaceableCollection where RRC1.Iterator.Element == RRC2.Iterator.Element> (lhs: RRC1, rhs: RRC2) -> RRC1 However, when I add another + to the game, I get this: func f<T>(t:

问题 I cannot understand fully how reflect works, so I'm having some trouble trying to register a custom type adapter for my GsonBuilder . I need to register a type adapter for a List<Something> type. This is a working code: gsonBuilder.registerTypeAdapter( new TypeToken<List<MyClass>>() { }.getType(), new ListDeserializer(MyClass.class) ); The thing is that I have a lot of classes to register my type adapter, and I have a ListDeserializer and SingleDeserializer adapters. I'm trying to go generic