extends

问题 I have following folder structure (simplified): project - app.js - views - index.jade - layout.jade - public ... I want to generate an index.html file from index.jade and use the following command in my Terminal (Mac OS X): jade < index.jade > index.html However I receive an error saying: /usr/local/lib/node_modules/jade/lib/runtime.js:231 throw err; ^ Error: Jade:1 > 1| extends ./layout 2| 3| block mainContent 4| center the "filename" option is required to use "extends" with "relative" paths

问题 I am using the below code and tryin to add CHild object is the list: List<? extends Parent> list = new ArrayList<Child>(); list.add(new Child()); //error: The method add(capture#1-of ? extends Parent) in the type List<capture#1-of ? extends Parent> is not applicable for the arguments (Child) class Parent{ } class Child extends Parent{ } I want to know why compiler throws error here? 回答1: If you go through the Generic Guidelines stated by Oracle docs, these kind of list declarations are tend

问题 I'm officially mentally retarded. [Let me explain] I've never really given classes and their relationship any thought until today. I'm trying to figure out something that seems to be pretty obvious but since I'm stupid I can't see it. Let's say I have a Core Class that will be extended from different files. How can children classes call functions from other siblings (that is if those are considered childs at all). Sample Code: (don't kill me) class cOne { public function functionOne(){ echo

问题 I'm moving over to java from DotNet and this idea of extends is new. I've seen some posts that fully explain using List<? extends SomeAbstract> vs. List<? super SomeAbstract> vs. List<SomeAbstract> , but I'm guessing that there is no difference between using, and not using, extends in generics. Is that true? Would the answer change if using an abstract class as the parent? class My_AbstractExtends<T extends SomeAbstract> vs. class My_Abstract<SomeAbstract> EDIT Creates child classes as

问题 What is the difference between these two methods? Collection<Type> getTypes(); vs Collection<? extends Type> getTypes(); Does it matter if Type is a class or an interface? Especially, when designing an API, which version would be preferred and why? 回答1: Collection<Type> getTypes(); Here, getTypes() must return a Collection<Type> (e.g. ArrayList<Type> or HashSet<Type> ). Collection<? extends Type> getTypes(); Here, getTypes() can return a Collection of anything that is or extends Type , (e.g.

问题 Is it possible to create something like this in java public abstract class GenericView<LAYOUTTYPE extends AbstractLayout> extends LAYOUTTYPE so that public class MyView extends GenericView<HorizontalLayout> extends GenericView and HorizontalLayout and public class MyView2 extends GenericView<VerticalLayout> extends GenericView and VerticalLayout ? 回答1: The short answer - no. The type you extends must be an actual type, not a generic type parameter. 回答2: It sounds like you want to accomplish

问题 I'm struggling with EasyMock. I've written two small classes to illustrate my problem: public abstract class A { private AtomicReference<Integer> id = new AtomicReference<Integer>(null); public final int getId() { return id.get(); } public final boolean setId(int id) { return this.id.compareAndSet(null, id); } } public class B extends A { } Then I proceed to write a test method as follows: public class EasyMockTester extends EasyMockSupport { @Test public void test() { B b = EasyMock

问题 Lets say I have classes A and B , where B extends A . I also have a constructor in B with one argument which is of type A . I also have an object of type B called bObj . Is there a way to call B.class.getConstructor(new Class[] { bObj.getClass() }) and get the constructor since B extends A ? At the moment I'm getting a NoSuchMethodException . Regards, Stan 回答1: I suggest you have a look at the ConstructorUtils from Apache Commons Lang. They have all manners of constructor discovery methods.

问题 In Java type arguments, does mean strictly subtypes only? or would E also suffice? 回答1: Yes, super and extends gives inclusive lower and upper bounds respectively. Here's a quote from Angelika Langer's Generics FAQ: What is a bounded wildcard? A wildcard with an upper bound looks like ? extends Type and stands for the family of all types that are subtypes of Type , type Type being included . Type is called the upper bound . A wildcard with a lower bound looks like ? super Type and stands for

问题 This question already has answers here : Closed 8 years ago . Possible Duplicate: Can I extend a class using more than 1 class in PHP? I have a class that has several child classes, however I am now adding another class which I also want to be a child of the parent, however I would also like to utilize many of the functions from one of the other child classes. I've thought of just moving the respective functions from the other child class to the parent, however didn't think this was really