Functional interfaces

Functional interfaces - examples:

@FunctionalInterface 

interface Walkable {

    public String walk();

}

@FunctionalInterface  

interface Sayable{  

    void say(String msg);

} 

and after using:

        Walkable walkWithLambda = () -> {

            return "I want to walk around.";

        };

        walkWithLambda.walk();

        Sayable sayWithLambda = (msg) - > {

            System.out.println(msg);

        };

        sayWithLambda.say("I want to say something important!");

https://dzone.com/articles/introduction-functional-1

https://docs.oracle.com/javase/8/docs/api/?java/lang/FunctionalInterface.html

https://stackoverflow.com/questions/36881826/what-are-functional-interfaces-used-for-in-java-8

https://www.javaguides.net/2018/07/java-8-functional-interfaces.html

https://www.javaguides.net/2018/11/java-functionalinterface-annotation.html

https://github.com/RameshMF/java-8-tutorial/tree/master/src/com/ramesh/java8/functionalInterfaces