I got this unwanted message

Question

Java uses unchecked or unsafe operations.
When i compile this code in my laptop.
Which line is causing this message.
And how to remove it.
https://code.sololearn.com/c58mwd4bCcdd/?ref=app

Answer 1

same as Coder Kitten:

public static Set<Object> join(Set<Cat> cats, Set<Dog> dogs) {
//HashSet pets = new HashSet();
HashSet<Object> pets = new HashSet<>();

Answer 2

Coder Kitten can you teach me how to edit?

Answer 3

Let me check it

Answer 4

Looks legit

Answer 5

Yeah I dunno if it's a bug or you did it wrong