What is the difference between `isEmpty()` and `none()`?

# getting-started

[Aregev2]

What is the difference between isEmpty() and none()?

[Shawn]

have you read the docs? they’re very different functions

[Shawn]

assuming you’re talking about the methods defined on Iterable

[Aregev2]

yes

[Aregev2]

Not the methods with the predicates

[Aregev2]

But none() (not none { })

[adam-mcneilly]

Looks like they're similar, but the code seems slightly nuanced in that isEmpty() is on a collection but none() is on an Iterable specifically. I'm guessing it's possible for something to be iterable and not a collection and that's where you can use it?

[Aregev2]

🤔 Interesting...

[adam-mcneilly]

I'm guessing based on what I saw, I'm not claiming expertise here ha

[adam-mcneilly]

I clicked into the source on none()

[Aregev2]

And..?

[Aregev2]

It just return isEmpty() 😕

[adam-mcneilly]

only if it's of type collection

[adam-mcneilly]

if (this is Collection) return isEmpty()
return !iterator().hasNext()

[karelpeeters]

I don't really get why they added that method, they should have called it isEmpty() too.

[karelpeeters]

Same for find and firstOrNull, just pick one.

[elye]

You could use sequence.none() but not sequence.isEmpty(). What is sequence? Check out https://medium.com/@elye.project/kotlin-slow-list-and-lazy-sequence-61691fc974c5

[Andreas Sinz]

@karelpeeters I'd guess that they named it different because it behaves different. Collection.isEmpty() checks if there is anything inside the collection, Iterator.none() checks if any items are left to iterate over

[karelpeeters]

No it's Iterable.none, you don't start with an existing iterator.

[Andreas Sinz]

oh