inheritance

问题 I found following code, What is use of inherited equals() and toString() method. @FunctionalInterface public interface FunInterface<T> { // An abstract method declared in the functional interface int test(T o1, T o2); // Re-declaration of the equals() method in the Object class boolean equals(Object obj); String toString(); } 回答1: The main reason to (re)declare such a method, is to extend and document the contract. In case of Comparator.equals(…), it’s not that obvious, as it doesn’t specify

问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 6 years ago . I'm a Java programmer, learning to program in Go. So far I really like the language. A LOT more than Java. But there's one thing I'm a bit confused about. Java has interfaces because classes can inherit only from one class. Since Go allows multiple inheritance, what's the

问题 We say that java follows a single inheritance model i.e. a Java class can extend only one class at max. and then say that every java class is inherited from Object class. Suppose there are two classes A and B. Both A and B extend from Object. Now suppose A extends B. Doesn't it imply that A has multiple inheritence (A is inheriting from both B and Class Object)? 回答1: Look at the difference between transitive inheritance (C inherits directly from B and transitively from A): and multiple

问题 Is there a collection in c# that supports the inheritance like concept that objects can have of appearing to include all the elements from another as well as themselves? For example: HashSet<animal> animals = new HashSet<animal>(); HashSet<dog> dogs = new HashSet<dog>(); animals.also_appears_to_include(dogs); So if I for example added 2 elements to dogs and 1 to animals, then looked at how many elements animals has I would see 3. Alternatively I could put references to the above mentioned 3

问题 I've been working with the prototype library for some time now and occasionally find myself wishing I had multiple access levels (public, private, and protected). The closest I've come so far is the following: SampleBase = Class.create({ /* virtual public constructor */ initialize: function(arg1, arg2) { // private variables var privateVar1, privateVar2; // private methods var privateMethod1 = function() { } function privateMethod2() { } // public (non virtual) methods this.publicNonVirtual1

问题 I've created a subclass of UIImage (UIImageExtra) as I want to include extra properties and methods. I have an array that contains instances of this custom class.However when I save the array, it appears the extra data in the UIImageExtra class is not saved. UIImageExtra conforms to NSCoding, but neither initWithCoder or encodeWithCoder are called, as NSLog statements I've added aren't printed. My method to save the array looks like this: - (void)saveIllustrations { if (_illustrations == nil)

问题 I know in Java , static method can not be overriden by the subclass. Two questions: 1. Why is that? Could anyone explain me the reason inside it? 2. Can subclass override final method in super class then? 回答1: Static methods aren't called on a particular instance - so they can't be called polymorphically. They are called on the type itself - nothing about the binding relies on any information which is only available at execution time. The point about polymorphic calls is that the method

问题 I have the following scenario. I have a base class from which a class derives. Everything appears good however, every time I hover my mouse cursor over an inherited member of the base class, the intellisense shows it fine, EG BaseClass::SomeMember. However, when I try to compile, the compiler shows various errors(they are about the variables and member functions that the intellisense was reporting well). The compiler says 'they're not valid identifiers', that they don't 'belong to a global

问题 I'm trying to practice Inheriting Constructors in C++. I have compiled and run following program in gcc and it's working fine. #include<iostream> using namespace std; class Base1 { public: Base1() { cout<<"Base1 Default Constructor\n"; } Base1(int i) { cout<<"Base1 parametrized Constructor\n"; } }; class Base2 { public: Base2() { cout<<"Base2 Default Constructor\n"; } Base2(const string& s) { cout<<"Base2 parametrized Constructor\n"; } }; class Derived :public Base1, public Base2 { public:

问题 I am using Rails 3.2.2 with mongoid 2.4.6. In order to keep my collections small I am storing child objects to a base class in sepparate collections using the "store_in" statement. My code looks like this: class BaseClass include Mongoid::Document end class ChildClass1 < BaseClass store_in :child_1 end class ChildClass2 < BaseClass store_in :child_2 end It appears that the objects get randomly stored in or or the other child collection. An object of type Child1 sometimes gets stored in