overriding

问题 I have created a class that extends Array. I want to execute arbitrary code before calling the inherited push function. class newArray extends Array{ //execute any logic require before pushing value onto array this.push(value) } 回答1: The solution I found was to create a new function in the subclass that has the same name as the inherited function. In this case push. Then inside the overriding function the inherited function is called via the super keyword. class newArray extends Array{ push

问题 I'm trying to understand the name clash error I get with the following code: import java.util.*; import javax.swing.*; class Foo<R extends Number> { public void doSomething(Number n, Map<String, JComponent> comps) { } } class Bar extends Foo { public void doSomething(Number n, Map<String, JComponent> comps) { } } Error message: error: name clash: doSomething(Number,Map<String,JComponent>) in Bar and doSomething(Number,Map<String,JComponent>) in Foo have the same erasure, yet neither overrides

问题 I'm trying to understand the name clash error I get with the following code: import java.util.*; import javax.swing.*; class Foo<R extends Number> { public void doSomething(Number n, Map<String, JComponent> comps) { } } class Bar extends Foo { public void doSomething(Number n, Map<String, JComponent> comps) { } } Error message: error: name clash: doSomething(Number,Map<String,JComponent>) in Bar and doSomething(Number,Map<String,JComponent>) in Foo have the same erasure, yet neither overrides

问题 I want to build a rails app with two different protect_from_forgery strategies: one for the web application, and one for the API. In my application controller I have this line of code: protect_from_forgery with: :exception in order to prevent CSRF attacks, it works just fine. In my API namespace, I created an api_controller that inherits from my application controller, and that is the parent class of all the other controllers in the API namespace, and I changed the code above with: protect

问题 I have a few months of experience developing Extjs web application. I ran into this problem: When I override a class, I modified the method and followed the previous implementation and invoke callParent() . The overriding part works but the callParent() invoked the old implementation. my overriding code Ext.override(Ext.layout.component.Draw, { finishedLayout: function (ownerContext) { console.log("new layouter being overriden"); this.callParent(arguments); } }); The Extjs class method to be

问题 I'm having a little problem understanding variance of methods when overloading. While this perfectly works due to covariance in the return type class Bla class Fasel extends Bla trait Test[A] { def tester(): Bla = new Bla } class FooTest[A](a: A) extends Test[A] { override def tester(): Fasel = new Fasel } this one fails even though functions are contravariant in their parameter types. class Bla class Fasel extends Bla trait Test[A] { def tester(a: Fasel): Bla = new Bla } class FooTest[A](a:

问题 I'm having difficulty trying to override a property declared in a profile-specific application properties file on the classpath with another value declared in an overrides file on the file system. I have an auto-configured Spring-boot application (that is, using @EnableAutoconfiguration ) that has multiple profiles, which I launch using PropertiesLauncher rather than JarLauncher (the reason having to do with deployment constraints - I need to deploy an exploded directory rather than an

问题 My Parent class is : import java.io.IOException; public class Parent { int x = 0; public int getX() throws IOException{ if(x<=0){ throw new IOException(); } return x; } } I extend this class to write a subclass Child : public class Child1 extends Parent{ public int getX(){ return x+10; } } Notice while overriding the getX method in the Child class , I have removed the throws clause from the method definition .Now it results in an anomalous behavior by the compiler which is expected : new

问题 Per this answer and this answer, Java static methods aren't virtual and can't be overridden. Intuitively, therefore, this should work (even if in 99% of cases it's dangerous programming): class Foo { public static String frob() { return "Foo"; } } class Bar extends Foo { public static Number frob() { return 123; } } However, in practice this gets you: Foo.java:10: frob() in Bar cannot override frob() in Foo; attempting to use incompatible return type found : java.lang.Number required: java

问题 So I'm writing a class that extends a dictionary which right now uses a method "dictify" to transform itself into a dict. What I would like to do instead though is change it so that calling dict() on the object results in the same behavior, but I don't know which method to override. Is this not possible, or I am I missing something totally obvious? (And yes, I know the code below doesn't work but I hope it illustrates what I'm trying to do.) from collections import defaultdict class