overriding

问题 I'm trying to use vtk in my code, but I'm having problems running an example. I have almost no clue about the reasons since it's the first time I'm using it and I'm not very experienced. I'm using visual studio 2012 and x64 platform. Since I don't really know which libs should I use I added all of them to the "Additional Dependencies". The example is given in this link. The problem is that when I run it, the window shows this message Generic Warning: In C:\location\VTK6.0.0\Rendering\Core

问题 I know what overriding is in C++. But, is there overwriting ? If so, what does it mean? Thanks. 回答1: In C++ terminology, you have overriding (relating to virtual methods in a class hierarchy) and overloading (related to a function having the same name but taking different parameters). You also have hiding of names (via explicit declaration of the same name in a nested declarative region or scope). The C++ standard does not use the term "overwrite" except in its canonical English form (that is

问题 I just spotted this in some code: class Foo { [...] private: virtual void Bar() = 0; [...] } Does this have any purpose? (I am trying to port some code from VS to G++, and this caught my attention) 回答1: See this Herb Sutter article as to why you'd want to do such a thing. 回答2: This is a pure virtual function that happens to be private. This makes it so that a derived class must implement the method. In this case Bar. I think you may be confused b/c this is done to create "interfaces" in C++

问题 I'm trying to override a private method on a Java class using meta programming. The code looks something like this: // Java class public class MyClass{ private ClassOfSomeSort property1; private ClassOfSomeOtherSort property2; public void init(){ property1 = new ClassOfSomeSort(); property2 = new ClassOfSomeOtherSort(); doSomethingCrazyExpensive(); } private void doSomethingCrazyExpensive(){ System.out.println("I'm doing something crazy expensive"); } } // Groovy class public class

问题 public class Foo { public int a = 3; public void addFive(){ a += 5; System.out.print("f "); } } public class Bar extends Foo { public int a = 8; public void addFive(){ this.a += 5; System.out.print("b " ); } } public class Test { public static void main(String args[]){ Foo f = new Bar(); f.addFive(); System.out.println(f.a); } } I am getting output b 3 .why it is not giving b13 as output.Can anyone please explain. 回答1: Assuming class Foo is declared as below class Foo { public int a = 3;

问题 I'm learning java. I was trying to run the code, where I got this error: return type is incompatible . Part of code where it showed me error. class A { public void eat() { } } class B extends A { public boolean eat() { } } Why it is happening? 回答1: This is because we cannot have two methods in classes that has the same name but different return types. The sub class cannot declare a method with the same name of an already existing method in the super class with a different return type. However

问题 I have two classes: public class MyBase { public virtual void DoMe() { } } public class MyDerived:MyBase { public override void DoMe() { throw new NotImplementedException(); } } And I have the following code to instantiate MyDerived: MyDerived myDerived=new MyDerived(); The thing is how to call DoMe of the base class? If I use myDerived.DoMe(), then the derived method wil be called, resulting in an exception. I tried to cast myDerived to MyBase, yet it is still the derived version of the

问题 I'm having a hard time trying to understand the output of the following code: class Bar { public function test() { $this->testPublic(); $this->testPrivate(); } public function testPublic() { echo "Bar::testPublic\n"; } private function testPrivate() { echo "Bar::testPrivate\n"; } } class Foo extends Bar { public function testPublic() { echo "Foo::testPublic\n"; } private function testPrivate() { echo "Foo::testPrivate\n"; } } $myFoo = new foo(); $myFoo->test(); Output: Foo::testPublic Bar:

问题 I have a repository for one of my projects that has a nested repository using the svn:externals property to update files from an external library. The problem is that I need to comment out one of the function declarations from one of the headers in this library, and carry around the modified header with the root repository. Is there a way that this could be done, so that when the library is updated, it overrides that specific file with my version of it? 回答1: What you want sounds like a

问题 Consider the following snippet: import java.util.*; public class EqualsOverload { public static void main(String[] args) { class Thing { final int x; Thing(int x) { this.x = x; } public int hashCode() { return x; } public boolean equals(Thing other) { return this.x == other.x; } } List<Thing> myThings = Arrays.asList(new Thing(42)); System.out.println(myThings.contains(new Thing(42))); // prints "false" } } Note that contains returns false !!! We seems to have lost our things!! The bug, of