Confusion on call Java Interface method

Question

Let's say I have an interface A, defined as follows:

public interface A {   public void a(); } 

It includes method called void a();

I have a class which implements this interface and has only one method:

    public class AImpl implements A {        @Override        public void a() {            System.out.println("Do something");        }     } 

Q: If in the main class, I call interface method, will it call the implementation belonging to class which implements the interface?

For example:

public static void main(String[] args){   A aa;   aa.a(); } 

Will this print "Do something"?

Answer 1

A aa = new AImpl(); aa.a(); 

Here your reference variable is interface A type But actual Object is AImpl.

When you define a new interface, you are defining a new reference data type. You can use interface names anywhere you can use any other data type name. If you define a reference variable whose type is an interface, any object you assign to it must be an instance of a class that implements the interface.

Read more on Documentation

A Interface reference can hold Object of AImpl as it implements the A interface.