Classes & Objects

A class's constructor parameters can be declared right in the class header, dramatically shortening what would be several lines in Java.

Example: a data class

data class Student(val name: String, val track: String)

fun main() {
    val ada = Student("Ada", "Frontend")
    println("${ada.name} is studying ${ada.track}")
}

Ada is studying Frontend

Compare this one line to Java's Student class from the Java tutorial — Kotlin's data class automatically generates useful boilerplate a Java class needs written by hand: a readable toString(), equality checks comparing actual field values instead of just object identity, and more. This is exactly what makes it the right choice for classes that are mainly just holding data — which is precisely what most Android UI models look like in practice.