//By giving the annotation here, we are making sure that the compiler //gives us the error if we try to declare more than one abstarct method in here @FunctionalInterface interface A{ void show(); //declaration of the abstract method } class B implements A{ public void show(){ System.out.println("In show method..."); } } public class Functional_Interface{ public static void main(String[] args){ B obj = new B(); obj.show(); } }