Challenge 2: Data Class Equality & toString — Solution

data class Book(val title: String, val author: String, val year: Int)

fun main() {
    val book1 = Book("Kotlin in Action", "Dmitry Jemerov", 2017)
    val book2 = Book("Kotlin in Action", "Dmitry Jemerov", 2017)

    println(book1 == book2)
    println(book1)
}

/*
Output:
true
Book(title=Kotlin in Action, author=Dmitry Jemerov, year=2017)

Notes:
- book1 and book2 are two separate instances, but == returns true because
  data class equals() compares property values, not object references
  (a plain "class Book(...)" without "data" would print false here).
- println(book1) uses the auto-generated toString(), which lists every
  constructor property by name — no manual toString() override needed.
*/