interface

问题 interface A { public void doSomething(); } interface B extends A { public void doSomethingElse(); } public class AClass implements A, B { public void doSomething() {} public void doSomethingElse() {} } Why does Java permit such a declaration? What's the use of implementing both interfaces when same thing can be achieved by implementing the SubInterface (B)? 回答1: I think the "why" question can only be answered by Java designers. One reason might be that it permits retrofitting extends A to B

问题 For larger VBA projects (40,000+ lines of code) I cannot properly use interfaces because the Application (I mainly use Excel) will crash quite often. Apparently, this is because the code cannot remain compiled (from my understanding VBA code gets compiled to P-code which is later interpreted). I mainly get this behavior when the VBA Project is password protected. The Debug/Compile menu is almost never "greyed out" when I open the hosting document: This article describes the same behavior. Go

问题 For larger VBA projects (40,000+ lines of code) I cannot properly use interfaces because the Application (I mainly use Excel) will crash quite often. Apparently, this is because the code cannot remain compiled (from my understanding VBA code gets compiled to P-code which is later interpreted). I mainly get this behavior when the VBA Project is password protected. The Debug/Compile menu is almost never "greyed out" when I open the hosting document: This article describes the same behavior. Go

问题 I have a class A in java and interface B in Kotlin. // kotlin interface B { fun optional() } // java class A implements B { } I want to write the default method (Java 8 feature) in Kotlin interface (B) and want to implement it in the class A. How can I achieve it? Thanks in advance. 回答1: In Kotlin, interface methods with bodies are by default compiled as following: // kotlin interface B { fun optional() { println("B optional body") } } is compiled roughly to: public interface B { void

问题 I'm have a parent class, and I would like to "force" everyone that will inherit from it to implement some specific class attributes. I don't have this problem with methods, since I have created a dummy method that raises NotImplementedError , which makes it very clear. As for class attributes- I do not want to create them in the parent class and set them to None since that doesn't force the developer to implement them in the child class. A little code to demonstrate the current situation:

问题 I simply want to call a Fragment method from my MainActivity. So I tried to use an Interface. public interface MyInterface { void testMethod(); } In my Fragment (TestFragment.java) I implement the interface and overrite the testMethod method. @Override public void testMethod() { Toast.makeText(getActivity(), "Test", Toast.LENGTH_LONG).show(); } but now I want to call this method from my MainActivity as soon as the onRewardedVideoCompleted get's called, but I'm not sure how to do it. I tried

问题 In java, an interface contains only the method type, name and parameters. The actual implementation is done in a class that implements it. Given this, how is it possible to create an instance of a interface and use it as if it were a class object? There are many such interfaces, such as org.w3c.dom.Node. This is the code that I am using: DocumentBuilderFactory fty = DocumentBuilderFactory.newInstance(); fty.setNamespaceAware(true); DocumentBuilder builder = fty.newDocumentBuilder();

问题 In java, an interface contains only the method type, name and parameters. The actual implementation is done in a class that implements it. Given this, how is it possible to create an instance of a interface and use it as if it were a class object? There are many such interfaces, such as org.w3c.dom.Node. This is the code that I am using: DocumentBuilderFactory fty = DocumentBuilderFactory.newInstance(); fty.setNamespaceAware(true); DocumentBuilder builder = fty.newDocumentBuilder();

问题 I have one abstract class -let's say myBase. And I want all the classes derived from myBase to have one static field called public static List<string> MyPArameterNames { get {return _myParameterNames;} } So, every child class can tell what parameter names it uses; I want static because I do not want to create an instance just for this. How can I achieve this? 回答1: You can't do that. Interfaces, abstract, etc. cannot apply to static members. If you want to accomplish this, you will have to

问题 I have one abstract class -let's say myBase. And I want all the classes derived from myBase to have one static field called public static List<string> MyPArameterNames { get {return _myParameterNames;} } So, every child class can tell what parameter names it uses; I want static because I do not want to create an instance just for this. How can I achieve this? 回答1: You can't do that. Interfaces, abstract, etc. cannot apply to static members. If you want to accomplish this, you will have to