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Kotlin Academy · Lesson

Data Classes in Collections

Use in maps and sets.

Data Classes Meet Collections

Because data classes have value-based equals and hashCode, they behave perfectly inside collections.

This lesson shows how data classes work in lists, sets, and maps.

Data Classes in a List

Store data objects in a list and iterate over them like any other elements.

Their readable toString makes printing easy.

data class User(val name: String, val age: Int)

fun main() {
    val users = listOf(User("Alice", 30), User("Bob", 25))
    for (u in users) println(u)
}

All lessons in this course

  1. Declaring Data Classes
  2. copy and equals
  3. Destructuring Declarations
  4. Data Classes in Collections
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