Problem Statement
Explain Kotlin's null safety system and the different operators for handling nulls.
Explanation
Kotlin's null safety system distinguishes nullable types with question mark like String question mark from non-nullable types like String, making null checks part of the type system and preventing NullPointerExceptions at compile time. Use safe call question mark dot to safely access nullable properties returning null if the object is null, Elvis operator question mark colon to provide default values for null cases, let function with safe call to execute code only when non-null, and not-null assertion double exclamation only when absolutely certain value is not null as it throws exception if null. The system also includes safe casts with as question mark that return null instead of throwing ClassCastException, requireNotNull function to throw IllegalArgumentException with custom message if value is null useful for validation, and checkNotNull for similar checks. This comprehensive null safety eliminates billion-dollar mistake of null references while keeping code concise and readable.
