subclass

In java at least, my compiler won't let me put two (or more) separate classes in a single class file. It forces me to create multiple files in the same package. I understand why this is, and I agree with this principle. However, I've realized that I could just as easily nest the classes and contain the entire program (excluding imported libraries) in a single file. I would imagine that this would be frowned upon, but I don't understand why. What are the dangers and disadvantages of nesting class as opposed to the standard system (outside of the severe loss in organization and neatness)? Well,

Hi I'm wondering if there is a simple solution to my problem, I have an ArrayList : ArrayList <Animal> animalList = new ArrayList<Animal>(); /* I add some objects from subclasses of Animal */ animalList.add(new Reptile()); animalList.add(new Bird()); animalList.add(new Amphibian()); They all implement a method move() - The Bird flies when move() is called. I know I can access common methods and properties of the super class by using this public void feed(Integer animalIndex) { Animal aAnimal = (Animal) this.animalList.get(animalIndex); aAnimal.eat(); } That's fine - but now I would like to

While creating a java program i encountered a problem, A subclass constructor is throwing an Error by calling the Superclass's method The code is similar to this : class Manage { public static void main(String[] args) { Manager m1 = new Manager ( 35 ); } } class Employee { int emp_id; public Employee(int id) { this.emp_id = id; } public int get_id() { return emp_id; } } class Manager extends Employee { public Manager(int id ) { this.emp_id = id ; } } class Engineer extends Employee { public Engineer(int id) { this.emp_id = id ; } } And the error is something like this : $ javac app.java app

This question is related to, but not a duplicate of, this , this , this , and this . Those links don't answer my question here. This though , almost answers my questions but doesn't, because the code in the answer doesn't run in Python 3.6 and in any case the question there isn't specifically about what I'm asking here. (See my own answer below. From the Python documentation page , I find the following text. __new__() is intended mainly to allow subclasses of immutable types (like int, str, or tuple) to customize instance creation. It is also commonly overridden in custom metaclasses in order

I'm trying to learn and grasp what and how C# does things. I'm historically a Visual Foxpro (VFP) developer, and somewhat spoiled at the years of visual inheritance by creating my own baseline of user controls to be used application wide. In trying to learn the parallels in C#, I am stuck on something. Say I derive my own label control (control is subclass of label) defined with a font "Arial", 10 point. Then, on any form I add it to, the Designer will automatically pre-fill in some property values which can be seen in the "Designer.cs" portion of the Form class. this.LabelHdr2.AutoSize = true

class BaseDoc { static Collection; static find(){ // which is expected to return an instance of SubDoc when run SubDoc.find() return this.Collection.find(); } } class SubDoc extends BaseDoc {} What I hope is: When running SubDoc.find(), the app knows the type of the return value to be an instance of SubDoc rather than BaseDoc. How can I achieve that? You can create a generic version of find that will have the this parameter inferred to the type of the class it's being called on, and use InstanceType<T> to extract the actual instance type from the class type: class BaseDoc { static Collection:

As mentioned here and here , this doesn't work anymore in numpy 1.7+ : import numpy A = numpy.array([1, 2, 3, 4], dtype=numpy.int16) B = numpy.array([0.5, 2.1, 3, 4], dtype=numpy.float64) A *= B A workaround is to do: def mult(a,b): numpy.multiply(a, b, out=a, casting="unsafe") def add(a,b): numpy.add(a, b, out=a, casting="unsafe") mult(A,B) but that's way too long to write for each matrix operation! How can override the numpy *= operator to do this by default? Should I subclass something? You can use np.set_numeric_ops to override array arithmetic methods: import numpy as np def unsafe