Creating Object - java help on CodeGym

Hi all, I'm trying to understand the logic on creating object and would appreciate it if someone can offer a clear explanation on the following example.

My question is on line 24 & 25. From what I understand, this is using user-defined data type, BodyPart and assigning the return value of robotFirst.attack() method, making the variable attacked to store the reference to the method. I think the class BodyPart is used as the data type because AbstractRobot is an abstract class(therefore, can't create an object of it), and because it seems logical that the BodyPart should be the class as the methods are about being attacked & defend. Isn't it true that however, if we had more classes that are not abstract, we could use any other classes, or actually use any interfaces as the reference type? Is there some more concrete method/reason for using BodyPart as the user-defined data type here? If anyone has any clear answer to this (not just an opinion), I'd appreciate it very much. Happy coding! :)

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Guadalupe Gagnon

Level 37 , Tampa, United States

4 June 2021, 17:13

The attack() and defend() methods both have the return type BodyPart. Therefore you need to store the object they return in a variable that is BodyPart. Being abstract has nothing to do with it. You could be specific and change the code to:

Leg attacked = robotFirst.attack();
Arm defended = robotFirst.defend();

But what if the methods returned a BodyPart that wasn't a Leg or Arm... the code would fail. If the BodyPart class had super classes or implemented any interfaces you could also use any of those as the variable type.

ImDevin

Level 15 , Old Town, United States

4 June 2021, 17:29

Of course, that makes sense. I knew there had to be a logical answer (I can't believe I didn't see that). I appreciate your answer and thanx for the additional info as well.

4 June 2021, 17:36

just an update. I fixed a typo in my original post. The last line originally said: "If the BodyPart class had super classes or implemented any methods you could also use any of those as the variable type." That underlined "method" should be "interface"

4 June 2021, 17:39

haha, I was wondering about that actually, as I have seen that done in the past. thx Lupe.