constructor

问题 This question already has answers here : Inheritance in Java - creating an object of the subclass invokes also the constructor of the superclass. Why exactly? (15 answers) Default constructors and inheritance in Java (11 answers) order of constructor calls in multilevel inheritance in java [duplicate] (4 answers) Closed 5 years ago . When I try the code on the bottom of this question, the output is: a a b a b c So this means that the constructor from B and C call the constructors from their

问题 I followed this tutorial to start to understand the move semantics and rvalue references in C++11. At some point, he implements these two classes with the std::move in the move constructors explaining that we pass the temporary to a move constructor, and it takes on new life in the new scope. In the context where the rvalue expression was evaluated, the temporary object really is over and done with. But in our constructor, the object has a name; it will be alive for the entire duration of our

问题 Well I understand the part that I will be getting some random value, but is the Foo() constructor in the snippet acting just like the default public constructor which the compiler supplies when we have no constructor defined? #include<iostream> using namespace std ; class Foo{ int i ; public: Foo(){ } void disp(){ cout<<"i = "<<i ; } }; int main(){ Foo bar1,bar2 ; bar1.disp(); cout<<"\n"; bar2.disp(); } I have seen some people writing an empty constructor like this, but I could't understand

问题 Calling the fruitName method inside Fruit constructor, is actually delegating the call to the child Apple class's method! public class CallingParentMethodInInheritanceHierarchy { abstract class Fruit { String fruitName; public Fruit(String fruitName) { this.fruitName = fruitName; /* * o/p - Inside constructor - Child: Fruit name is - Apple */ System.out.println("Inside constructor - " + fruitName()); // doubt? } public String fruitName() { return "Parent: Fruit name is - " + fruitName; }

问题 Calling the fruitName method inside Fruit constructor, is actually delegating the call to the child Apple class's method! public class CallingParentMethodInInheritanceHierarchy { abstract class Fruit { String fruitName; public Fruit(String fruitName) { this.fruitName = fruitName; /* * o/p - Inside constructor - Child: Fruit name is - Apple */ System.out.println("Inside constructor - " + fruitName()); // doubt? } public String fruitName() { return "Parent: Fruit name is - " + fruitName; }

问题 I think this is really a very lame question, but I guess on SO I will receive the answer faster than by googling it myself :) Let's say I have some class with a constructor: public class TestClass { private readonly IRepository repository; public TestClass(IRepository repository) { this.repository = repository; // Here is the non-obvious line - it invokes some // method, which changes the internal contents of // the repository object. repository.AddSomething(...); } } And now: IRepository

问题 first of all I apologize if my question is difficult to understand. I'm having a hard time trying to explain exactly what I need help with. I am new to Java and the concept of passing by reference etc. Basically, I need to know why the below code is incorrect. How do I tell Java to use a method for an object passed in as a parameter of the constructor? Apologies again, and thanks for reading! public ClassOne(ClassTwo twoObject){ } public boolean OneMethod(){ twoObject.MethodName(); //

问题 Context I've noticed that some functions can only be called with the new prefix. When called without it, the error Illegal Invocation is thrown. Below is two examples of how the console reacted when the Image was called in different ways. -> new Image(); <- <img> -> Image(); <- TypeError: DOM object constructor cannot be called as a function. Even more interesting, under closer observation, these types of functions seem like functions, yet they aren't. Take Image for example, the typeof

问题 I'm working through the book Head First C# (and it's going well so far), but I'm having a lot of trouble wrapping my head around the syntax involved with using the "this." keyword. Conceptually, I get that I'm supposed to use it to avoid having a parameter mask a field of the same name, but I'm having trouble actually tracking it through their examples (also, they don't seem to have a section dedicated to that particular keyword, they just explain it and start using it in their examples).

问题 This question combines unique_ptr as class member and move semantics fail to compile with clang and C++ std::vector in constructor. My goal is to construct a wrapper struct V_wrapper{ std::vector<std::unique_ptr<AClass> > vec; V_wrapper(std::vector<std::unique_ptr<AClass> > v) : vec{std::move(v)} {} }; Unfortunately this code does not compile, because the compiler (clang Apple LLVM version 4.2) attempts to copy construct the vector v which is not supported. On the other hand, if I design an