我应该如何解释接口和抽象类之间的区别?

在我的一次采访中，我被要求解释接口类和抽象类之间的区别。

以下是我的回答:

Methods of a Java interface are implicitly abstract and cannot have implementations. A Java abstract class can have instance methods that implements a default behaviour. Variables declared in a Java interface are by default final. An abstract class may contain non-final variables. Members of a Java interface are public by default. A Java abstract class can have the usual flavours of class members like private, protected, etc. A Java interface should be implemented using keyword “implements”; A Java abstract class should be extended using keyword “extends”. An interface can extend another Java interface only, an abstract class can extend another Java class and implement multiple Java interfaces. A Java class can implement multiple interfaces but it can extend only one abstract class.

然而，面试官并不满意，他告诉我这种描述代表了“书本知识”。

他让我给出一个更实际的回答，用实际的例子解释我什么时候会选择抽象类而不是接口。

我哪里错了?

当前回答

是的，从技术上讲，你的回答是正确的，但你的错误之处在于，你没有向他们表明你理解选择其中一个的利弊。此外，他们可能担心将来升级时代码库的兼容性问题。这种类型的回答可能有帮助(除了你说的):

"Choosing an Abstract Class over an Interface Class depends on what we project the future of the code will be. Abstract classes allow better forward-compatibility because you can continue adding behavior to an Abstract Class well into the future without breaking your existing code --> this is not possible with an Interface Class. On the other hand, Interface Classes are more flexible than Abstract Classes. This is because they can implement multiple interfaces. The thing is Java does not have multiple inheritances so using abstract classes won't let you use any other class hierarchy structure... So, in the end a good general rule of thumb is: Prefer using Interface Classes when there are no existing/default implementations in your codebase. And, use Abstract Classes to preserve compatibility if you know you will be updating your class in the future."

祝你下次面试好运!

2016-06-19 15:53:18

其他回答

在Java中选择接口是为了避免多重继承中的菱形问题。

如果你想让你所有的方法都由你的客户端实现，你可以选择接口。这意味着你要抽象地设计整个应用程序。

如果您已经知道它们的共同点，那么您就可以选择抽象类。例如，取一个抽象类Car。在更高的级别上实现常见的car方法，如calculateRPM()。这是一种常见的方法，你让客户端实现他自己的行为，比如 calculateMaxSpeed()等。也许你会举几个你在日常工作中遇到的真实例子来解释。

2013-09-13 04:35:28

你的回答是对的，但是面试官需要你从软件工程的角度来区分，而不是根据Java的细节。

简单的单词:

An Interface is like the interface of a shop anything that is shown on it should be there in the shop, so any method in the Interface must be there implemented in the concrete class. Now what if some classes share some exact methods and varies in others. Suppose the Interface is about a shop that contains two things and suppose we have two shops both contain sport equipment but one has clothes extra and the other has shoes extra. So what you do is making an abstract class for Sport that implements the Sports method and leave the other method unimplemented. Abstract class here means that this shop doesn't exist itself but it is the base for other classes/shops. This way you are organising the code, avoiding errors of replicating the code, unifying the code, and ensuring re-usability by some other class.

2016-11-27 18:06:07

接口是纯粹抽象的。我们在接口中没有任何实现代码。

抽象类包含方法及其实现。

点击这里观看接口和抽象类教程

2013-10-08 09:38:11

你的解释看起来还不错，但可能看起来像是你从课本上读的?: - /

我更关心的是，你的例子有多可靠?你是否费心去包括抽象和接口之间几乎所有的区别?

就我个人而言，我建议这个链接: http://mindprod.com/jgloss/interfacevsabstract.html#TABLE

对于差异的详尽列表..

希望它能帮助你和所有其他读者在未来的采访

2013-09-13 04:07:24

接口与抽象类的基本区别在于，接口支持多重继承，而抽象类不支持。