// Immutable User in Kotlin (Using val + Data Classes for True Immutability)
//
// Kotlin enforces immutability through:
//
// 1. `val` → prevents reassignment of variables
// 2. `data class` → fields are immutable unless declared `var`
// 3. No setters → no mutation path
// 4. `copy()` → creates new modified instances without altering the original
//
// Immutable User using a data class (all fields are val)
data class User(val id: Int, val name: String)
fun main() {
// Immutable user
val user = User(42, "Sophia")
println("ID: ${user.id}")
println("Name: ${user.name}")
// Attempt 1: modify id
// user.id = 100 // ERROR: 'val' cannot be reassigned.
// Attempt 2: modify name
// user.name = "Tom" // ERROR: 'val' cannot be reassigned.
// Instead, Kotlin uses copy() to create a new modified instance
val updatedUser = user.copy(name = "Tom")
println("Updated Name (new instance): ${updatedUser.name}")
// Original remains unchanged
println("Original Name: ${user.name}")
}
/*
run:
ID: 42
Name: Sophia
Updated Name (new instance): Tom
Original Name: Sophia
*/
