在 Java 中实例化接口 [英] Instantiating interfaces in Java

问题描述

我有这个界面:

public interface Animal {
    void Eat(String name);
}

这里的代码实现了接口:

And this code here implements the interface:

public class Dog implements Animal {
    public void Eat(String food_name) {
        System.out.printf(food_name);
    }
    
    public static void main(String args[]) {
        Animal baby2 = new Dog(); // <- this line
        baby2.Eat("Meat");
    }
}

我的问题是，为什么代码有效?接口不能被实例化.然而在这种情况下，接口被实例化(用注释标记).

My question is, why does the code work? An interface cannot be instantiated. Yet in this case, interface was instantiated (marked with the comment).

这里发生了什么?

推荐答案

不，它不是 - 你正在实例化一个 Dog，但是因为一个 Dog 是一个 Animal，您可以将变量声明为Animal.如果您尝试实例化接口 Animal，它将是:

No it is not - you are instantiating a Dog, but since a Dog is an Animal, you can declare the variable to be an Animal. If you try to instantiate the interface Animal it would be:

Animal baby2 = new Animal();

试试那个，然后看着编译器惊恐地尖叫:)

Try that, and watch the compiler scream in horror :)

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