extends

问题 regarding the following code: public class Test <T extends Comparable>{ public static void main(String[] args){ List<String> lst = Array.asList("abc","def"); System.out.println(func(lst)); } public static boolean func(List<**here**> lst){ return lst.get(0).compareTo(lst.get(1)) == 0; } } why writing " ? extends Comparable" here would compile , and writing "Comparable" would not compile? thanks in advance. 回答1: This happens because generics are invariant . Even if String is a Comparable ,

问题 regarding the following code: public class Test <T extends Comparable>{ public static void main(String[] args){ List<String> lst = Array.asList("abc","def"); System.out.println(func(lst)); } public static boolean func(List<**here**> lst){ return lst.get(0).compareTo(lst.get(1)) == 0; } } why writing " ? extends Comparable" here would compile , and writing "Comparable" would not compile? thanks in advance. 回答1: This happens because generics are invariant . Even if String is a Comparable ,

问题 I need to extend an interface in Typescript to contain a Date type. I have tried the following interface WithDate { [key: string]: Date; } But when I try to extend WithDate , I get the error: interface Person extends WithDate { id: number; // Property 'id' of type 'number' is not assignable to string index type 'Date' name: string; date: Date; } Any ideas how to fix this error? Many thanks 回答1: interface WithDate { [key: string]: Date; } With this interface you are telling TypeScript that

问题 I need to extend an interface in Typescript to contain a Date type. I have tried the following interface WithDate { [key: string]: Date; } But when I try to extend WithDate , I get the error: interface Person extends WithDate { id: number; // Property 'id' of type 'number' is not assignable to string index type 'Date' name: string; date: Date; } Any ideas how to fix this error? Many thanks 回答1: interface WithDate { [key: string]: Date; } With this interface you are telling TypeScript that

问题 It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center. Closed 8 years ago . I have two classes that need to extend one class. I am getting a compiler error since this cannot happen in Java. I know that you can implement as many interfaces you want to in Java but can only extend one other

问题 i have the following class which i want to extend. export class AngularComponent { constructor( private r: Renderer2, private editorService: AngularEditorService, @Inject(DOCUMENT) private doc: any, private sanitizer: DomSanitizer, private cdRef: ChangeDetectorRef, @Attribute("tabindex") defaultTabIndex: string, @Attribute("autofocus") private autoFocus: any ) } So i create the following class: export class EnhancedComponent extends AngularComponent{ constructor(private r: Renderer2, private

问题 I've got a question coming from the following two tsconfig.json files, they're in the same project, one extends the other: Parent { "compilerOptions": { "experimentalDecorators": true, "skipLibCheck": true, "module": "ESNext" } // ... Child { "extends": "./tsconfig.json", "compilerOptions": { "outDir": "./out-tsc/app", "module": "esNext", }, // ... } It's unclear: is the module param case sensitive? a setup like this, with a child config extending the parent, same module type, but with

问题 This question already has answers here : How do I determine if a class extends another class in Java? (4 answers) Closed 7 years ago . Is there any method for checking if a one class extends another class? Above code is snippet File[] fileList = file.listFiles(); if(fileList != null){ for(int i = 0; i < fileList.length; ++i){ ClassName = fileList[i].getName(); if (fileList[i].isFile() && (Class Extends Class2) && ClassName.endsWith(".class")){ String ClassName1 = ClassName.split("\\.")[0]; if

问题 On possible duplicate: This thread is not asking how to extend a final class. It is asking why a class declared as final could possibly extend another class. From this thread: A final class is simply a class that can't be extended . However, I have a helper class which I declared to be final and extends another class: public final class PDFGenerator extends PdfPageEventHelper { private static Font font; private PDFGenerator() { // prevent instantiation } static { try { BaseFont baseFont =

来源： https://stackoverflow.com/questions/28120111/why-can-i-create-an-variable-with-type-of-parent-class