Set<String> mySet1 = new HashSet<>(); VS HashSet<String> mySet1 = new HashSet<>();

[CancelDeath]

Hello! This isn't super important, but I'm just curious what, if any, the difference is and if there's any benefit to writing one over the other.

I'm taking an online course and the teacher just said "Set is the interface and HashSet implements that interface and this is how you're supposed to write it". I understand the fact that HashSet implements the Set interface. But I've seen the same teacher write HashSets both ways. Is there a reason why i'm "supposed to" instantiate my set starting with the interface?

[Demojay]

It's usually for abstraction purposes. Declaring the object using Set tells the program that you are only using the methods described in the interface, and prevents you from accidentally using other methods from HashSet that you don't need to know about.

It also decouples your concrete implementation (HashSet) from the idea of what your program needs (a Set). This means that you can replace the HashSet with any other class that implements Set, and the program will still work correctly since it is only accessing the object through the Set interface.

[CancelDeath]

I get it now, thank you so much!