Sealed classes can have subclasses outside the same file.

Sealed classes restrict inheritance hierarchy to a known set of subclasses:\n\n1. Declaration\n• All subclasses must be in the same file\n• Provides exhaustive when expressions\n• Example:\n\n\n2. Exhaustive When Expressions\n• Compiler ensures all cases are handled\n• No else clause needed\n• Example:\n\n\n3. Advanced Usage with Generics\n\n\n4. Benefits\n• Type safety with exhaustive checking\n• Better than enums for complex data\n• Compiler prevents missing cases\n• Clear state representation\n\n5. Common Use Cases\n• API response states\n• UI state management\n• Navigation states\n• Result handling patterns