匿名内部类中的接口如何工作？

Question

interface MyInter {
    public void display();
}

class OuterClass8 {

    public static void main(String arg[]) {

        MyInter mi=new MyInter() {

            public void display() {
                System.out.println("this is anonymous class1");
            }
        };

        mi.display();
    }
}

As far as I know, we cannot instantiate an interface, so how did this happen?

Answer 1

By declaring

MyInter mi=new MyInter(){

    public void display() {
        System.out.println("this is anonymous class1");
    }
};

You are declaring an anonymous inner class that implements the MyInter interface. It's similar to doing

public class MyInterImpl implements MyInter {
    public void display() {
        System.out.println("this is anonymous class1");
    }
}

and creating an instance

MyInterImpl mi = new MyInterImpl();

but you are doing it anonymously.

---

You are correct in thinking that you cannot instantiate an interface. You cannot do

MyInter mi = new MyInter();

but you can do what is presented above.

Answer 2

您不能实例化接口，但是您可以提供接口的实现接口的类的对象的引用，因此在代码中您实现接口并创建该类的对象并提供该类的引用。

Answer 3

yes, keep in mind that YOU CAN NOT instantiate an abstract class or interface..

this is wrong:

MyInter mi = new MyInter();

but you must have read that a super class reference variable can hold the reference to the sub class object.

so by creating

MyInter mi=new MyInter(){

    public void display() {
        System.out.println("this is anonymous class1");
    }
};

you are creating an object , an anonymous object , that however has MyInter as the superclass..