Does Kotlin's LinkedHashMap use reference identity...

# getting-started

[v79]

Does Kotlin's LinkedHashMap use reference identity or equals() in its get() method? I have two different objects with the same values, and an overridden equals method which returns true. But as a key to hashmap, they don't match.

[Joffrey]

Have you also overridden hashCode() accordingly? 2 equal objects must have the same hashcode, that's the contract between both methods. Hashmaps rely on this by first checking hashcode and then using equals when searching for keys

[v79]

... suddenly I feel dumb. Be right back!

[v79]

I've been a professional Java dev for about 10 years but now I'm just a manager. Clearly I'm forgetting the basics!

[Joffrey]

Note that if you use Kotlin's data classes, they will have autogenerated hashcode and equals based on the properties declared in the primary constructor. It's usually easier this way

[v79]

Yes, absolutely, but I needed to exclude something from equality checks in this case.

[Joffrey]

Then it may depend on your exact case, but just in case, you can exclude properties from the generated `equals`/`hashCode` if you declare them outside of the primary constructor (directly in the data class's body)

[ephemient]

https://youtrack.jetbrains.com/issue/KT-40850
I think I'd be ok with a change to the language to allow @Transient or some other annotation to exclude a property from the auto-generated equals and hashCode (but that's clearly not what we have now)