overriding

问题 I was just trying some sample code for checking class variable overriding behavior in Java. Below is the code: class A{ int i=0; void sayHi(){ System.out.println("Hi From A"); } } class B extends A{ int i=2; void sayHi(){ System.out.println("Hi From B"); } } public class HelloWorld { public static void main(String[] args) { A a= new B(); System.out.println("i->"+a.i); // this prints 0, which is from A System.out.println("i->"+((B)a).i); // this prints 2, which is from B a.sayHi(); // method

问题 I need to do some additional stuff in a setter method. But I get an infinite loop when doing so: I've got a core data object @interface Transaction : NSManagedObject @property (nonatomic, retain) NSDate * date; @end @implementation Transaction @dynamic date; -(void)setDate:(NSDate *)date { self.date = date; //additional stuff omitted } So, in that case I get an infinite loop. Okay so I searched on the net and modified my code in the following way and for every version I get compiler errors

问题 I need to do some additional stuff in a setter method. But I get an infinite loop when doing so: I've got a core data object @interface Transaction : NSManagedObject @property (nonatomic, retain) NSDate * date; @end @implementation Transaction @dynamic date; -(void)setDate:(NSDate *)date { self.date = date; //additional stuff omitted } So, in that case I get an infinite loop. Okay so I searched on the net and modified my code in the following way and for every version I get compiler errors

问题 Consider the following (LinqPad) example. ToString in class X is marked virtual. Why is the output here not equal to "Hi, I'm Y, Hi, I'm X" but instead the typename is printed? Of course marking ToString virtual is wrong, because it is defined in Object as virtual, I am just trying to understand what is happening here. void Main() { Y y = new Y(); Console.WriteLine(y); } // Define other methods and classes here class X { public virtual String ToString() { return "Hi, I'm X"; } } class Y : X {

问题 I know (from the compiler's errors) that a constant property cannot be overridden by a constant, nor can it be overridden by the getter of a computed property. Obviously they can't be overridden by anything non-constant. There's no reason to add observers to them, either, since they'll never change. And yet final let seems to be a thing. Is it impossible to override a stored constant property? Is final let exactly equivalent to let ? 来源： https://stackoverflow.com/questions/35671819/is-it

问题 I need to modify the templates for the angular 2 material date-picker. Its templates are declared in several internal components that are defined in @angular/material/esm5/datepicker.es5.js. I could modify the template directly in the node package, but then it would get overwritten when updating. The only two ways I can see this being possible is if I modify the template dynamically (is this really possible?), or if I copy over the entire angular material node package locally and then modify

问题 I've already seen the similar question here, and I have already added the line import android.content.res.Configuration; . It hasn't helped though. I am writing a class that extends AdapterView<Adapter> , and Eclipse will not let me override onConfigurationChanged(Configuration) . As seen in the AdapterView page in the Android Docs, the method does indeed exist. So why can't I override it? Here is my implementation: import android.content.Context; import android.content.res.Configuration;

问题 What OO principle is broken by the following code ? Not Java OO principle but general OO principle. class GeneralArg{} class Arg extends GeneralArg{} class A{ public void test(Arg a){} } class B extends A{ @Override public void test(GeneralArg a){} } I think this should work! However there is a compile error saying that B.test() doesn't override A.test() 回答1: Statement 1: Every GeneralArg is not an Arg. Base definition of test says: test() takes an Arg as input. B's definition says: the same

问题 This question has evolved in a confusing way. Some of its parts though, and specially some answers, might be useful for someone. Therefore I'll let this question unmodified and I'll try to reformulate the question here. Overriding the template folder_full_view_item.pt with z3c.jbot will override the template for all Content Types. How do I override it only for a single Content Type MyType in a Product with many types? Having the following structure: Folder (layout=folder_full_view) Document

问题 I am struggling to understand Variables Shadowed Methods Overriden Concept of inheritance with Java. Case 1: class Car{ public int gearRatio = 8; public String accelerate() { return "Accelerate : Car"; } } class SportsCar extends Car{ public int gearRatio = 9; public String accelerate() { return "Accelerate : SportsCar"; } public static void main(String[] args){ Car c = new SportsCar(); System.out.println( c.gearRatio+" "+c.accelerate() ); } } Output: 8 Accelerate : Sportscar. Case 2: public