first() will throw an exception if there is no suitable item in the list (e.g., the list is empty).

In contrast, firstOrNull() returns null if there is no suitable item in the list. So, in this case, noEvent will be null, as there is no matching Event.

You can learn more about this in:
Tags:
Accessing Elements via [] any() any() and Short Circuits Array Modification Arrays Combining Collections filter() first() first() Sans Lambda firstOrNull() firstOrNull() and the Elvis Operator fold() for Loop forEach() forEach() is a Function joinToString() Lists map() map() Type Conversions Maps Mutable Lists Sets Typed Arrays
any() any() and Short Circuits Chaining Higher-Order Functions first() first() Sans Lambda firstOrNull() firstOrNull() and the Elvis Operator fold() Function Reference Function Reference for Member Functions Function References and Receivers Function Types Function Types and Direct Invocation Function Types and Parameters Functional Interfaces joinToString() Type Aliases
Run Edit