Kotlin Data Classes

Kotlin Data Class

In Kotlin, data classes are a concise way to declare classes that are primarily used to hold data.

They automatically generate useful methods such as toString(): to generate string representation of the object, equals(): to check if two data class objects are equal, hashCode(), and copy(): to copy a data class object. Also, you can override these methods with your own code in the class declaration, if required.

To declare a data class in Kotlin, you use the data keyword before the class keyword, and you list the properties of the class in the primary constructor.

For example,

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

In this example, Person is a data class with two properties: name and age. The compiler automatically generates the toString(), equals(), hashCode(), and copy() methods for you.

Example for Data Class

Now, let see an example program to understand how we can use this data class.

Kotlin Program

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

fun main() {
    val person1 = Person("John", 25)
    val person2 = Person("Jane", 30)

    println(person1)  // Output: Person(name=John, age=25)

    // Access properties using Destructuring declaration
    val (name, age) = person2
    println("Name: $name, Age: $age")

    // Copying an instance with modified properties
    val olderPerson = person1.copy(age = 26)

    // Equality check
    println("Is person1 equal to person2? ${person1 == person2}")


Person(name=John, age=25)
Name: Jane, Age: 30
Person(name=John, age=26)
Is person1 equal to person2? false