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Updated to the latest stable version of intellij and I've been getting suggestions to change objects to data objects when they're subclassing a sealed class, 

What's the difference between the object and data object
Or they're the same?

data objects are objects with better `toString()` implementations, saving you from having to add that yourself.

Another important thing is that `data object`s have overriden `equals` and `toString`.  This may be important in the use cases when they are created using reflection bypassing their singleton nature.
I once had a situation where jackson was creating `object` using reflection on json deserialization. That object was subclassing sealed interface and out of nowhere my exhaustive `when` expression started throwing `NoWhenBranchMatchedException` because object created by jackson wasn't the same instance as the one which should be the singleton in memory. `data object`s ensure such issues would not happen