Coffee.java

package org.jugbd.quiz;

import java.util.function.Function;
import java.util.stream.Stream;

import static org.jugbd.quiz.Coffee.CoffeeDecoratorUsingLambda.getCoffeeWithExtras;

@FunctionalInterface
public interface Coffee {

    String getIngredient();

    static Coffee withSaltedCaramelFudge(Coffee coffee) {
        return () -> coffee.getIngredient() + " +Salted caramel fudge";
    }

    static Coffee withSweetenedMilk(Coffee coffee) {
        return () -> coffee.getIngredient() + " + Sweetened Milk";
    }

    static Coffee withDarkCookieCrumb(Coffee coffee) {
        return () -> coffee.getIngredient() + " + Dark Cookie Crumb";
    }

    static Coffee withVanillAlmondExract(Coffee coffee) {
        return () -> coffee.getIngredient() + " + Vanilla/almond extract";
    }

    class CoffeeDecoratorUsingLambda {

        public static Coffee getCoffeeWithExtras(Coffee coffee, Function<Coffee, Coffee>... ingradiants) {
            Function<Coffee, Coffee> reduced = Stream.of(ingradiants).reduce(Function.identity(), Function::andThen);
            return reduced.apply(coffee);
        }
    }

    class CoffeeApp {

        public static void main(String[] args) {
            var coffee = getCoffeeWithExtras(() -> "Main Ingredient",
                    Coffee::withDarkCookieCrumb,
                    Coffee::withSweetenedMilk,
                    Coffee::withVanillAlmondExract);
            System.out.println(coffee.getIngredient());
        }
    }
}