Kotlin by Example: Data classes

Kotlin has a concept called "data classes". Data classes are similar to normal classes, but the compiler automatically generates `equals`, `hashCode`, `toString`, `componentN`, and `copy` functions for them.	class UserClass(val name: String, val age: Int)
A data class can be defined similarly to a normal class, but the definition is prefixed with the `data` keyword.	data class UserDataClass(val name: String, val age: Int) fun main() { val user1 = UserClass("Henk", 54) val user2 = UserClass("Henk", 54) val dataUser1 = UserDataClass("Henk", 54) val dataUser2 = UserDataClass("Henk", 54)
By default, classes use referential equality, which means that different instances of the class are never equal, even when all all the properties are.	println(user1 == user2)
The `equals` method (which is called by the equality operator) generated for data classes returns `true` iff all the properties are equal.	println(dataUser1 == dataUser2)
For data classes, a `toString` method is generated, so that we can print instances of data classes without needing to manually implement a `toString` method.	println(dataUser1)
For a data class with two properties, `component1` and `component2` functions are generated, which allows us to do a "destructuring declaration".	val (name, age) = dataUser1 println(name) println(age)
Data classes also have an autogenerated `copy` function, which allows you to make a shallow copy, while overwriting some values.	val anotherPerson = dataUser1.copy(name="Jaap") println(anotherPerson) }

$ kotlinc main.kt -include-runtime -d main.jar

$ java -jar Main.jar

false

true

UserDataClass(name=Henk, age=54)

Henk

UserDataClass(name=Jaap, age=54)