inheritance

问题 I'm trying to wrap my head around inheritance for a uni assignment and I've ran into a few problems so far. I'm trying to construct a method in my Pet class which holds the following code: public class Pet { protected String printed; public Pet() { } public String checkFunc(String definitelyPrinted) { printed = "CheckFunc is working! Oh boy!"; System.out.println("Those variables were useless"); return printed; } } This is being called by: public class KennelDemo extends Pet { private String

问题 For Example: function Person() { //person properties this.name = "my name"; } Person.prototype = { //person methods sayHello: function() { console.log("Hello, I am a person."); } sayGoodbye: function() { console.log("Goodbye"); } } function Student() { //student specific properties this.studentId = 0; } Student.prototype = { //I need Student to inherit from Person //i.e. the equivalent of //Student.prototype = new Person(); //Student.prototype.constructor = Person; //student specific methods

问题 So I have a question about a superclass A and subclass B, where A has 2 public variables and B has 1 more. I saw this snippet of code: A a = new A(); B b = new B(); a = b; What does that last line do? I don't really understand what actually happens when you use "=" between 2 classes in an inheritance relationship. 回答1: It's simple assignment. = is an assignment operator. Lets be clear of below points. In Java when an Object is created and it is accessible via. reference. A reference refer to

问题 I have written a template BST class with the usual operations like this: template <class Key,class T> class BTree { public: BTree():root(0){}//crea un albero vuoto BTree<Key,T>& treeInsert(const Key& k,const T& val); BTree<Key,T>& treeDelete(const Key& k); Node<Key,T>& treeSearch(const Key& k); Node<Key,T>& treeMinimum(); void treeClear(); protected: BTree<Key,T>& transplant(Node<Key,T>& n1,Node<Key,T>& n2); Node<Key,T>* root; }; I would like to implements a template red-black tree class that

问题 I´d like to create my own plotting class as follows but I can not find a way to inherit from Figure while using the plt module (see below). Either it inherits from Figure or it changes the tick_params . Figure is a class so I can inherit but plt is not a module? I am just a beginner trying to find my way through... Can someone show me how it works? import matplotlib.pyplot as plt from matplotlib.figure import Figure class custom_plot(Figure): def __init__(self, *args, **kwargs): #fn = os.path

问题 With a pointer to an object of a derived type assigned to a pointer of its base class, I've found that you can reinterpet_cast a method from the derived class to a pointer of the base class, even if the base class doesn't have any such function (virtual, hidden, or otherwise). And it can be dereferenced and called from there and it "just works". But I'd like to make sure it's not UB. Is this UB? Is it portable? Compilable Example: #include <cstdio> struct A { /* no foo method */ }; struct B :

问题 I am trying to understand the C++ language behaviour that I have observed (I understood the first half of it). My setup: 2 templated classes: A and C . A can be converted to C but not the other way around. They have some common behaviour, so I was searching to implement some logic only with C and rely on the conversion from A to C to make A behave the same way as C . The examples uses an operator overloading, but the discussion I think is the same with a function or a method. What I tried

问题 I am trying to understand the C++ language behaviour that I have observed (I understood the first half of it). My setup: 2 templated classes: A and C . A can be converted to C but not the other way around. They have some common behaviour, so I was searching to implement some logic only with C and rely on the conversion from A to C to make A behave the same way as C . The examples uses an operator overloading, but the discussion I think is the same with a function or a method. What I tried

问题 I am working with separate programs, one will read in a .txt file and then that same program will store the read in values into another program containing a HashMap . The program that contains the HashMap , is named Hero.java and is an abstract class . I have a program that extends that program called Cop.java . With that in mind, I would like to know the proper way to transfer the files read in from my GameDriver.java over to the HashMap . To my knowledge, one way of doing this is

问题 I have a solution with one project. In that project are something live 40 or 50 forms. I've made 4 base forms that all the other forms can inherit. All 4 of those base forms inherit System.Windows.Forms.Form. Almost 90% of the forms inherit one of the first 2 base form. The rest inherits one of the last 2. But now I got this error out of nowhere, I made like 3 progs with the last 2 base forms and while I'm making the 5th, this errors occures and the designer is disabled. The designer must