why is this allowed?

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this is from Java Core Level 3 Lesson 2, Beer part 2 Recovery. really want to know why this is allowed in Line 10 --> Drink beer = new AlcoholicBeer(); Drink is an interface, but here it's used as a Reference type. How is this possible? Someone did ask this question, but I could not understand the explanation (really tried). If someone could explain this well, I'd appreciate it.

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Gellert Varga

Level 23 , Szekesfehervar, Hungary

28 May 2021, 01:10

With some inaccuracy, you could say that AlcoholicBeer is a descendant (child) of the Drink interface. And a child object can easily be stored in a reference variable of type of its parent. This is the same as when you wrote this: List<Integer> list1 = new ArrayList<>(); List is an interface, ArrayList is a class. It's important to know that if you store a Drink object in a variable type of parent - instead of in a variable of type Drink - then only the methods within the parent class (interface) are available with this variable, the other Drink-methods not. If you have any further questions, feel free to ask.

ImDevin

Level 15 , Old Town, United States

28 May 2021, 02:39

thx for the reply Gellert. Let me chew on this for a while.