A modern programming language that makes developers happier.

kotlinlang

<https://www.reddit.com/r/Kotlin/comments/uzsjcy/seemingly_inconsistent_behavior_of_data_class/>

hashCode doesn't necessarily identify a unique object. 

It's perfectly valid for two different instances to have the same hashCode. 

the rule is that if two instances equal each other (via `.equals()`, which is `==` in Kotlin (except for NaN which we'll ignore here)), then they must have the same `hashCode()`. this implies the contrapositive (if two instances have different `hashCode()` then they must not be `==`), but does *not* imply the converse: it is allowed for two instances to have the same `hashCode()` but be `!=`

and of course, as Rob brings up, the same `hashCode()` can be returned by `!==` instances (I'm just clarifying that it *must* be, for `==` instances)