Where can we use the scenario where we can create an anonymous class when we do it for an Interface?

Question

Interface :

public interface MyFirstInterface {
    void myFirstAbstractMethod();
    default void myDefaultMethod() {
        System.out.println("Hi I am default method in Interface.");
    }
}

Class:

public class MyFirstClass{
    public static void main(String[] args) {
    MyFirstInterface myFirstInterface = new MyFirstInterface() {
        @Override
        public void myMethod() {
            System.out.println("Main class : "+this.getClass());
        }

    };

    myFirstInterface.myMethod();
    myFirstInterface.defaultMethod();

    }
}

Now we know we are instantiating a anonymous class, what I want to know is Why would anyone use it? What is the advantage or disadvantage of doing it?

Huh? What abstract constructor? I only see a method with return type `A`. — fabian, Sep 22 '16 at 10:15
it is not a constructor, it is abstract method `a()` of type `A`. Constructors cannot be abstract. — DimaSan, Sep 22 '16 at 10:15
Possible duplicate of [There is no constructor for interface in Java?](http://stackoverflow.com/questions/6201489/there-is-no-constructor-for-interface-in-java) — DimaSan, Sep 22 '16 at 10:24
I'm voting to close this question as off-topic because it's a "misread" by the asker. — Kayaman, Sep 22 '16 at 10:26

score 0 · Answer 1 · answered Sep 22 '16 at 10:46

It is not a constructor. It is a method a() declaration with the return type A.

Also, we can instantiate an interface using an anonymous class. Runnable for example:

Runnable r = new Runnable() {
   @Override 
   public void run() { ... }
};

Runnable r = () -> { ... }

Where can we use the scenario where we can create an anonymous class when we do it for an Interface?

1 Answers1