Data Classes in Kotlin
From the Kotlin cheat sheet · Data Classes & Objects · verified Jul 2026
Data Classes
Classes for holding data
kotlin
// Data class
data class User(
val id: Int,
val name: String,
var email: String
)
val user = User(1, "Alice", "alice@example.com")
val copy = user.copy(email = "newemail@example.com")
// Destructuring
val (id, name, email) = user
// Generated methods
println(user.toString()) // User(id=1, name=Alice, email=alice@example.com)
println(user.hashCode())
println(user == copy) // false (different email)
// Data class requirements
// - Primary constructor with at least one parameter
// - All parameters marked as val or var
// - Cannot be abstract, open, sealed, or inner💡 Data classes auto-generate equals(), hashCode(), toString(), copy()
⚡ Destructuring declarations use componentN() functions
📌 Only properties in primary constructor are used in generated methods
🟢 Use copy() to create modified instances immutably
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