Java中没有接口的构造函数？ [英] There is no constructor for interface in Java?

问题描述

在Java中，如果我有一个界面：

In Java, if I have an interface:

public interface MyInterface{
}

然后 MyInterface 实施是：

class MyClass implements MyInterface {
    public MyClass(int a) {
    }
}

所以我的意思是，如果用户想要声明一个 MyInterface 实例使用构造函数：

So what I mean is that if a user wants to do declare a MyInterface instance with constructor:

MyInterface mine = new MyInterface(2);

然后就不可能了吗？

推荐答案

MyInterface mine = new MyInterface(2);

那么这是不可能的吗？

这是对的。你永远不能做类似的事情

That's right. You can never do something like

MyInterface mine = new MyInterface(2);

在新之后你必须选择 class 实现接口^（*），例如 MyClass ：

After new you have to pick a class that implements the interface^(*), such as MyClass:

MyInterface mine = new MyClass(2);

为什么？

您可以想到接口作为类的属性。类比是形容词，例如红色。创建一个红球（ new RedBall（））或红色汽车（ new RedCar（）非常有意义$ c>），但只是创建红色（ new Red（））没有意义（red what ??） 。

Why?
You can think of an interface as a property of a class. An analogy would be an adjective, such as "Red". It makes perfect sense to create, say, a red ball (new RedBall()) or a red car (new RedCar()), but just creating "red" (new Red()) doesn't make sense ("red what??").

^{（*）您可以通过 new MyInterface（）{...创建动态实现接口的匿名类。 } 但从技术上讲，你还在实例化一个类。}

^{(*) You can create anonymous classes that implement the interface on the fly by doing new MyInterface() { ... } but technically speaking you're still instantiating a class.}

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