default-method

is there a way to add a default constructor to an interface

由 那年仲夏 提交于 2019-12-09 09:46:54
问题 With default methods now added to Java 8, is there any way to create a default constructor? I've tried: public interface KadContent<T> { public default KadContent() { } ... Getting the error <identifier> expected from Netbeans Why Needed? I'm using Gson to serialize the objects and getting the "unable to invoke no-args constructor .." error and I do know that I can resolve this problem using Gson's InstanceCreator. But is there a way to create a default Constructor? Update I've found the

Visitor pattern with Java 8 default methods

由 戏子无情 提交于 2019-12-08 19:18:41
问题 Visitor pattern (double dispatch) is a very useful pattern in its own rights, but it has often been scrutinized of breaking interfaces if any new member is added to the inheritance hierarchy, which is a valid point. But after the introduction of default methods in Java 8, now that we can define default implementation in interfaces, the client interfaces will not break and clients can gracefully adopt the changed interface as appropriate. interface Visitor{ public void visit(Type1 type);

Fundamental difference between interface and abstract class in Java 8 [duplicate]

由 淺唱寂寞╮ 提交于 2019-12-07 10:49:56
问题 This question already has answers here : Interface with default methods vs Abstract class in Java 8 (15 answers) What are the differences between abstract classes and interfaces in Java 8? (5 answers) Closed 5 years ago . Considering that interfaces now can give an implementation to the methods it provides, I cannot properly rationalize the difference between interfaces and abstract classes. Does anyone know how to explain the difference properly? I was also told that interfaces are somewhat

Does Java have plan that default method (java8) Substitute for Abstract Class?

由 三世轮回 提交于 2019-12-06 13:28:07
Does Java have plan that default method substitute for Abstract Class ? I could not find a real case to use default method instead of Abstract? Default methods can't substitute abstract classes, as abstract classes can (and often do) have fields. Interfaces can only contain behaviour and not state, which is unlikely to change in the future as multiple inheritance of state in Java is seen (rightly or wrongly) as evil. They can also have final methods, which is another thing you can't mimic with default methods. If anything, interfaces with default methods resemble traits rather than abstract

Java 8 doesn't provide the same solution to allow multiple inheritance which they gave to solve interface default methods

由 帅比萌擦擦* 提交于 2019-12-06 08:17:13
问题 Problem: We know that Java doesn’t allow to extend multiple classes because it would result in the Diamond Problem where the compiler could’t decide which superclass method to use. With interface default methods the Diamond Problem were introduction in Java 8 . That is, because if a class implements two interfaces, each defining the same default method, and the implementing class doesn’t override the common default method, the compiler couldn’t decide which implementation to chose. Solution:

Confused about “super” keyword in this Java example

由 ↘锁芯ラ 提交于 2019-12-06 01:47:32
问题 In this example on java website's tutorial page. Two interfaces define the same default method startEngine() . A class FlyingCar implements both interfaces and must override startEngine() because of the obvious conflict. public interface OperateCar { // ... default public int startEngine(EncryptedKey key) { // Implementation } } public interface FlyCar { // ... default public int startEngine(EncryptedKey key) { // Implementation } } public class FlyingCar implements OperateCar, FlyCar { // ..

Should we do unit testing for default methods in interfaces (Java 8)? [closed]

由 一世执手 提交于 2019-12-05 20:28:39
问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 5 years ago . I feel a bit confused about the default methods implementations in interfaces introduced in Java 8. I was wondering if we should write JUnit tests specifically for an interface and its implemented methods. I tried to google it, but I couldn't find some guidelines. Please

Fundamental difference between interface and abstract class in Java 8 [duplicate]

由 好久不见. 提交于 2019-12-05 13:54:35
This question already has answers here : Interface with default methods vs Abstract class in Java 8 (15 answers) What are the differences between abstract classes and interfaces in Java 8? (5 answers) Closed 5 years ago . Considering that interfaces now can give an implementation to the methods it provides, I cannot properly rationalize the difference between interfaces and abstract classes. Does anyone know how to explain the difference properly? I was also told that interfaces are somewhat more light-weight compared to abstract classes, performance wise. Can someone confirm this? Interfaces

can marker interface like serializable contain default methods?

由 ╄→尐↘猪︶ㄣ 提交于 2019-12-04 18:29:46
问题 I think it can't, because marker interface principle is to not have any methods, but since default methods are not abstract I am not sure. 回答1: A "Marker" interface is just a regular interface as far as Java is concerned. Thus, it can have default methods just as any (Java-8) interface can. Now, as to whether this violates the principle of a Marker interface, I would have to say yes. A Marker interface should act as a flag of sorts, only identifying that a class meets some external criteria.

Java 8 doesn't provide the same solution to allow multiple inheritance which they gave to solve interface default methods

由 别来无恙 提交于 2019-12-04 11:54:31
Problem: We know that Java doesn’t allow to extend multiple classes because it would result in the Diamond Problem where the compiler could’t decide which superclass method to use. With interface default methods the Diamond Problem were introduction in Java 8 . That is, because if a class implements two interfaces, each defining the same default method, and the implementing class doesn’t override the common default method, the compiler couldn’t decide which implementation to chose. Solution: Java 8 requires to provide an implementation for default methods implemented by more than one interface
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