abstract-class

问题 Here is the code: interface hi { public void meth1(); } abstract class Hullo { public abstract void meth1(); } public class Hello extends Hullo implements hi { public void meth1(){} } Question:The code compiles and everything. I wanted to know the meth1() in class Hello is overriding which meth1()? The ont in the interface or the one in the abstract class and why? 回答1: The answer is short: Both..... In fact, to be correct: You are overriding none of them, you are implementing them both, with

问题 I have half a dozen classes which all extend the same abstract class. The abstract class has a static variable pointing to some JNI code that I only want to load once per instantiation of the classes. From what I understand this results in exactly one instance of this static variable being instantiated, but what I want is for each of the extending classes to have their own static instance of the variable that is unique for the given child class. I want to write some code in my abstract class

问题 This question already has answers here : Closed 10 years ago . Duplicate: When to use an interface instead of an abstract class and vice versa? Probably one of the most famous software developer job interview questions. What would be your answer? EDIT: I'm trying to find out how you would answer this in a real-life situation. Please try to formulate your answer as you would on a real job interview (be complete, but don't be too long, post no links of course). 回答1: An interface only describes

问题 I'm trying to extend this plugin for my own use... https://github.com/jamesmontemagno/Xamarin.Plugins/blob/master/Connectivity/Connectivity/Connectivity.Plugin.Abstractions/BaseConnectivity.cs But when I copy the code over to Visual Studio, I'm am getting some error. Do I need to import some special framework in order to use the '=>' operator and 'Invoke' Method? This is an abstract base class. I am using VS2013 回答1: ?. is a feature from C# 6, and as well as the => operator (when used for

问题 Is there any way to define abstract class properties in PHP? abstract class Foo_Abstract { abstract public $tablename; } class Foo extends Foo_Abstract { //Foo must 'implement' $property public $tablename = 'users'; } 回答1: There is no such thing as defining a property. You can only declare properties because they are containers of data reserved in memory on initialization. A function on the other hand can be declared (types, name, parameters) without being defined (function body missing) and

问题 I have a base class class ShapeF { public: ShapeF(); virtual ~ShapeF(); inline void SetPosition(const Vector2& inPosition) { mPosition.Set(inPosition); } protected: Vector2 mPosition; } Obviously with some ommitied code, but you get the point. I use this as a template, and with some fun (ommited) enums, a way to determine what kind of shape i'm using class RotatedRectangleF : public ShapeF { public: RotatedRectangleF(); virtual ~RotatedRectangleF(); protected: float mWidth; float mHeight;

问题 When we create a Subclass object which extends an abstract class, the abstract class constructor also runs . But we know we cannot create objects of an abstract class. Hence does it mean that even if a constructor completes running without any exception, there is no guarantee whether an object is created? 回答1: Hence does it mean that even if a constructor completes running without any exception, there is no guarantee whether an object is created? Simply speaking, a constructor does not create

问题 When we create a Subclass object which extends an abstract class, the abstract class constructor also runs . But we know we cannot create objects of an abstract class. Hence does it mean that even if a constructor completes running without any exception, there is no guarantee whether an object is created? 回答1: Hence does it mean that even if a constructor completes running without any exception, there is no guarantee whether an object is created? Simply speaking, a constructor does not create

问题 So I've been working on a homework on abstraction for my programming class and fell into a problem. The goal for me right now is to be able to use abstraction, then later be able to draw with rectangles and ovals a simple city, like a rectangular building or a oval light on a light post. The error I am receiving when I compile is: MyTestApp.Rectangle is not abstract and does not override abstract method drawEllipse(java.awt.Graphics) in MyTestApp.Shape. This Error shows up on the line "class

问题 I am making an abstract-base-class and was thinking I might want a pure virtual signal. But when I compiled I get a warning for the pure virtual signals I have defined: ../FILE1.h:27: Warning: Signals cannot be declared virtual ../FILE1.h:28: Warning: Signals cannot be declared virtual Is it valid to define a pure virtual signal in C++/Qt? Is it valid to define a virtual signal? Qt's signal and slot documentation page says you can define virtual slots but doesn't talk about signals. I can't