overriding

问题 class One { void foo() { } } class Two extends One { private void foo() { /* more code here */ } } Why is the above snippet of code wrong? 回答1: I'm going to try to incorporate the ideas from the other answers to come up with a single answer. First off, let's take a look at what's going on in the code. A look at the code The One class has a package-private foo method: class One { // The lack of an access modifier means the method is package-private. void foo() { } } The Two class which

问题 If I have this function, what should I do to replace the inner function with my own custom version? def foo(): def bar(): # I want to change this pass # here starts a long list of functions I want to keep unchanged def baz(): pass Using classes this would be easily done overriding the method. Though, I can't figure out how to do that with nested functions. Changing foo to be a class (or anything else) is not an option because it comes from a given imported module I can't modify. 回答1: Here's

问题 I am a little confused over the two terminologies and would be glad to get some doubts clarified. As I understand function overloading means having multiple methods in the same class with same name but either with different number of arguments, different types of arguments or sequence of arguments irrespective of the return type which has no effect in mangled name of the functions. Does the above definition also include "....in the same class or across related classes(related through

问题 The topic of how C# virtual and override mechanism works internally has been discussed to death amongst the programmers... but after half an hour on google, I cannot find an answer to the following question (see below): Using a simple code: public class BaseClass { public virtual SayNo() { return "NO!!!"; } } public class SecondClass: BaseClass { public override SayNo() { return "No."; } } public class ThirdClass: SecondClass { public override SayNo() { return "No..."; } } class Program {

问题 I wonder why this is a valid override: public abstract class A { public abstract <X> Supplier<X> getSupplier(); public static class B extends A { @Override public Supplier<String> getSupplier() { return String::new; } } } Whereas this is not: public abstract class A { public abstract <X> Supplier<X> getSuppliers(Collection<String> strings); public static class B extends A { @Override public Supplier<String> getSuppliers(Collection<String> strings) { return String::new; } } } According to JLS

问题 Suppose I am extending a standard Sencha ExtJS 4 widget/component, and I found a bunch of things that don't work the way I want them to, or perhaps they are just broken and Sencha hasn't gotten around to fixing the issues with the component yet. I'm just going to use the Sencha ExtJS Ext.tree.Panel and Ext.tree.Store as two example components. What are the most basic steps to overriding the constructor, configs, properties, methods and events so I can find and fix the issues with that

问题 class Base {} abstract class A { abstract public List<Base> Items { get; set; } } class Derived : Base {} class B : A { private List<Derived> items; public override List<Derived> Items { get { return items; } set { items = value; } } } The compiler says that B.Items must be List of Base elements "to match overridden member" A.Items. How can i make that work? 回答1: What you've tried to accomplish initially is impossible - .NET does not support co(contra)variance for method overload. The same

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 This doesn't work: class Foo { public: virtual int A(int); virtual int A(int,int); }; class Bar : public Foo { public: virtual int A(int); }; Bar b; int main() { b.A(0,0); } It seems that by overriding Foo::A(int) with Bar::A(int) I have somehow hidden Foo::A(int,int) . If I add a Bar::A(int,int) things work. Does anyone have a link to a good description of what's going on here? 回答1: Essentially, name lookup happens before overload resolution so the function A in your derived class overrides

问题 I would like to create a CustomButton which has a predefined onClick . In fact, my object would do the same job than CustomButton mButton = getViewById(..); mButton.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { show_something() } Is there a way to embed the Listener into the CustomButton object that inherits from Button ? What I would like is to create a CustomButton in my layout XML file, and not having to mention this button in my activity, which would