As I learn new components in Kotlin, I came accross requireNotNull and checkNotNull but the only difference I've found is that requireNotNull can throw an IllegalArgumentException while checkNotNull can throw an IllegalStateException. Is this the only reason why there are two methods, or I'm missing some under-the-hood implementation detail?
It is a semantic difference and hence it throws different exceptions. RequireNotNull is used to check input values, typically at the beginning of a method, while checkNotNull is used anywhere to check the current state.