extends

问题 I am trying to define a method to return all neighbours of a given vertex on a graph given by the signature public abstract class GraphClass<V extends Vertex<?>,E extends Edge<V,?>> implements UndirectedGraph<V,E>{ . . . public ArrayList<V> getNeighbors(V v) {...} } I wish to override this method from my KTree class which extends the above GraphClass as follows public class KTree extends GraphClass<KVertex,KEdge> {... public ArrayList<KVertex> getNeighbors(KVertex v) { return v.getAdjList();

问题 I have a template that includes another template. This included template has block tags in it. Example: base.html BASE {% block title %}Base Title{% endblock %} {% block content %}{% endblock %} template1.html {% extends 'base.html' %} {% block title %}Extended Title{% endblock %} {% block content %} Extended content {% include 'include.html' %} {% endblock %} include.html {% block title %}Include Title{% endblock %} {% block another_content %}Include Content{% endblock %} What I'm expecting

问题 I have two simple CFCs as shown below: Test1.cfc <cfcomponent> <cffunction name="initMethod1" access="private" returntype="boolean"> <cfreturn true /> </cfcomponent> Test2.cfc <cfcomponent> <cffunction name="initMethod2" access="private" returntype="boolean"> <cfreturn true /> </cfcomponent> During OnApplicationStart() of Application.cfc, I make the following calls: <cfset application["Test1"] = CreateObject("component","jbx.c.Test1") /> <cfset application["Test2"] = CreateObject("component",

问题 I noticed that if I have two methods with the same name, the first one accepts SomeObject and the second one accepts an object extending SomeObject when I call the method with SomeOtherObject , it automatically uses the one that only accepts SomeObject . If I cast SomeOtherObject to SomeObject , the method that accepts SomeObject is used, even if the object is an instanceof SomeOtherObject . This means the method is selected when compiling. Why? 回答1: That's how method overload resolution in

问题 Quick novice question: I want to extend a class as an array, like so public class Map extends Item[][] { } Is this possible, am I going about it the wrong way? Thanks! 回答1: Arrays are weird beasts. The have some properties, like length but they are not a class, so you can't extend them like you are attempting. I think you are better off using composition, i.e. create a class that contains an Item[][] and then extend that class (if you need to, having one class might be enough) 来源： https:/

问题 I have 3 classes in WordPress (the question itself is unrelated to it): class WP_Widget class Theme_Widget extends WP_Widget class Specific_Widget extends Theme_Widget Essentially Theme_Widget contains some extension functions to the basic WP_Widget. Inside Specific_Widget I call one of Theme_Widget's methods: class Specific_Widget { function __construct() { $this->some_method_that_belongs_to_Theme_Widget(); } } When I instantiate Specific_Widget, PHP throws a fatal error as follows: Fatal

问题 I need to have a variable in a class which is an instance of class "ClassA" but which also implements interface "InterfaceI". Obviously this can be done for one or the other easily: private ClassA mVariable; private InterfaceI mVaraible; but how can I enforce the object both extends ClassA and implements InterfaceB? Something like: private <? extends ClassA & InterfaceI> mVaraible; is what I need but I have no idea of the syntax or if it is even possible. I will also need a get and set method

问题 Last Thursday someone at work showed me a compile error that I wasn't able to fix in a clean way and it has been bothering me ever since. The problem is generics related and I've reconstructed a simplified version of the code that generates the compile error. The error occurs in the very last line of code shown below. I've been looking all over the interwebs but can't seem to find a decent explanation why the Java compiler doesn't accept the code. I guess that if it were to allow the code, it

问题 So I am reading about generic method and I am get confused. Let me state the problem here first: In this example: Suppose that I need a version of selectionSort that works for any type T, by using an external comparable supplied by the caller. First attempt: public static <T> void selectionSort(T[] arr, Comparator<T> myComparator){....} Suppose that I have: Defined vehicle class created VehicleComparator implementing Comparator while compare vehicles by their price. created Truck extends

问题 This is what I have in foo.php class Foo { public $foo = NULL; public $foo2 = NULL; public function setFoo ($foo, $foo2) { $this->foo = $foo; $this->foo2 = $foo2' } } This is what I have in foo3.php class Foo3 extends Foo { public $foo3 = NULL; public function setFoo3 ($foo3) { $this->foo = $foo3; } } This is how I require it in my third file run.php: require_once "foo.php"; require_once "foo3.php"; $foo = new Foo(); $foo->setFoo3("hello"); I get this error: Fatal error: Call to undefined