overriding

问题 I realize that with basic logic I cannot put a override function into a if else statement because it will override everything. However i still need to put in the if else statement the prepare for segue. So the way the code I am working works is if a user hits a button twice they win the game and therefore go to the winners view controller where a score is displayed. If they lose they go to a view controller with no score. So I need to put the override function segue in updateTimer() , In the

问题 On object of child class, static methos of super class are available but when we define same method in child class, now object of child class start pointing to child class method.this complete sounds like overriding but it is not,since static method can't override. How this is happen and what this functionality of java is called? class A extends B { public static void main(String[] args) { new A().method();//call class B's method if method is not in A otherwise A's } /* public static void

问题 I want to override a virtual method with a derived class type. What's the current best way to do this? So far I've found two approaches: Use an abstract base class for each derived type; bridge with protected methods. Use a protected implementation with a public accessor. Base case (no solution implemented, Clone always returns base type A1 ): public class A1 { public int X1 { get; set; } public A1(int x1) { this.X1 = x1; } public virtual A1 Clone() { return new A1(X1); } } public class A2 :

问题 When I try to override a method that takes a List<String> , I get the following compile error . Multiple markers at this line: - The method getname(List<Integer>) of type child must override or implement a supertype method - Name clash: The method getname(List<Integer>) of type child has the same erasure as getname(List<String>) of type parent but does not override it I was under the impression, that due to erasure , a method that takes a List<String> and a subclass method that takes a List

问题 Below is my code. I am not getting what is the mistake. Can anyone be able to guide. class State { static String country; static String capital; State() // Constructor { country = "America's"; capital = "Washington D.C"; } static void display() { System.out.println(capital + " " + "is" + " " + country + " " + "capital."); } } class Place extends State // Method Overriding { static void display() { System.out.println("Capital is Washington D.C."); } public static void main(String[] args) {

问题 I have a bean in module1-spring.xml - <bean id="parent" class="com.Parent"/> <bean id="service" class="com.Service"> <property name="parent" ref="parent"/> </bean> I want to override the bean in module2-spring.xml - <bean id="child" class="com.Child" parent="parent"/> I want child to be passed in service instead of parent . If I alias child as parent i.e. <alias id="child" alias="parent"/> then the parent attribute will read child instead of parent bean and fail on server startup with error-

问题 I've been working on an assignment that involves an abstract class that represents a generic animal, with subclasses for cat, dog, reptile, etc. The superclass has abstract methods that aren't actually used by each subclass. For example, there are accessors and mutators for breed and gender that are used by dog and cat but not the reptile class. I personally think this is an odd setup, but it's what is required by the assignment. At first I tried leaving out the abstract methods not used in a

问题 I have this simple piece of code. abstract class X { X() { read(); } private void read() { Object obj = new Object(); readValue(obj); } protected abstract void readValue(Object obj); } class Y extends X { Object obj = null; Y() { super(); } @Override protected void readValue(Object obj) { this.obj = obj; } void printer() { System.out.println("Object = " + obj); } } class Runner { public static void main(String[] args) { Y y = new Y(); y.printer(); } } When I run the above code, the object

问题 In the SCJP book by Kathey Sierra, an excerpt is as follows: If a method is overridden but you use a polymorphic (supertype) reference to refer to the subtype object with the overriding method, the compiler assumes you’re calling the supertype version of the method. If the supertype version declares a checked exception, but the overriding subtype method does not, the compiler still thinks you are calling a method that declares an exception (more in Chapter 5). Let’s take a look at an example:

问题 In the SCJP book by Kathey Sierra, an excerpt is as follows: If a method is overridden but you use a polymorphic (supertype) reference to refer to the subtype object with the overriding method, the compiler assumes you’re calling the supertype version of the method. If the supertype version declares a checked exception, but the overriding subtype method does not, the compiler still thinks you are calling a method that declares an exception (more in Chapter 5). Let’s take a look at an example: