Below is the program. But please clarify for me the line in the subject? It the new Food() selectable object part of Selectable interface? I thought you can't instantiate an interface? 
public class Solution {
    public static void main(String[] args) {
        Food food = new Food();
        Selectable selectable = new Food();
        Food newFood = (Food) selectable;

        foodMethods(food);
        selectableMethods(selectable);
    }

    public static void foodMethods(Food food) {
        //write your code here
        food.onSelect();
        food.onEat();
    }

    public static void selectableMethods(Selectable selectable) {
        //write your code here
        selectable.onSelect();
    }

    interface Selectable {
        void onSelect();
    }

    static class Food implements Selectable {
        public void onEat() {
            System.out.println("The food was eaten");
        }

        public void onSelect(){
            System.out.println("The food was selected");
        }
    }
}