overriding

问题 What are differences between declaring a method in a base type \" virtual \" and then overriding it in a child type using the \" override \" keyword as opposed to simply using the \" new \" keyword when declaring the matching method in the child type? 回答1: The "new" keyword doesn't override, it signifies a new method that has nothing to do with the base class method. public class Foo { public bool DoSomething() { return false; } } public class Bar : Foo { public new bool DoSomething() {

问题 Okay, I\'ve been reading and searching around, and am now banging my head against the wall trying to figure this out. Here\'s what I have so far: package com.pockdroid.sandbox; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Rect; import android.widget.ImageView; public class ShadowImageView extends ImageView { private Rect mRect; private Paint mPaint; public ShadowImageView(Context context)

问题 On pressing the back button, I\'d like my application to go into the stopped state, rather than the destroyed state. In the Android docs it states: ...not all activities have the behavior that they are destroyed when BACK is pressed. When the user starts playing music in the Music application and then presses BACK, the application overrides the normal back behavior, preventing the player activity from being destroyed, and continues playing music, even though its activity is no longer visible

问题 I am studying overriding member functions in JAVA and thought about experimenting with overriding member variables. So, I defined classes public class A{ public int intVal = 1; public void identifyClass() { System.out.println(\"I am class A\"); } } public class B extends A { public int intVal = 2; public void identifyClass() { System.out.println(\"I am class B\"); } } public class mainClass { public static void main(String [] args) { A a = new A(); B b = new B(); A aRef; aRef = a; System.out

问题 Two interfaces with same method names and signatures. But implemented by a single class then how the compiler will identify the which method is for which interface? Ex: interface A{ int f(); } interface B{ int f(); } class Test implements A, B{ public static void main(String... args) throws Exception{ } @Override public int f() { // from which interface A or B return 0; } } 回答1: If a type implements two interfaces, and each interface define a method that has identical signature, then in

问题 Can overridden methods have different return types ? 回答1: Java supports * covariant return types for overridden methods. This means an overridden method may have a more specific return type. That is, as long as the new return type is assignable to the return type of the method you are overriding, it's allowed. For example: class ShapeBuilder { ... public Shape build() { .... } class CircleBuilder extends ShapeBuilder{ ... @Override public Circle build() { .... } This is specified in section 8

问题 class Dad { protected static String me = \"dad\"; public void printMe() { System.out.println(me); } } class Son extends Dad { protected static String me = \"son\"; } public void doIt() { new Son().printMe(); } The function doIt will print \"dad\". Is there a way to make it print \"son\"? 回答1: Yes. But as the variable is concerned it is overwrite (Giving new value to variable. Giving new definition to the function is Override). Just don't declare the variable but initialize (change) in the

问题 I am trying to override equals method in Java. I have a class People which basically has 2 data fields name and age . Now I want to override equals method so that I can check between 2 People objects. My code is as follows public boolean equals(People other){ boolean result; if((other == null) || (getClass() != other.getClass())){ result = false; } // end if else{ People otherPeople = (People)other; result = name.equals(other.name) && age.equals(other.age); } // end else return result; } //

问题 I ran into an interesting (and very frustrating) issue with the equals() method today which caused what I thought to be a well tested class to crash and cause a bug that took me a very long time to track down. Just for completeness, I wasn\'t using an IDE or debugger - just good old fashioned text editor and System.out\'s. Time was very limited and it was a school project. Anyhow - I was developing a basic shopping cart which could contain an ArrayList of Book objects . In order to implement

问题 Has anyone got any experience with overriding the alert() function in JavaScript? Which browsers support this? Which browser-versions support this? What are the dangers in overriding the function? 回答1: It's definitely "supported". It is your web page, you do whatever you want to with it. I already did this to track analytics events without modifying a library but by sneaking into events. Use the proxy pattern: (function(proxied) { window.alert = function() { // do something here return