JSON to Kotlin Data Class

Data classes are a special Kotlin feature that automatically generates equals(), hashCode(), toString(), and copy() methods based on the properties declared in the primary constructor. They are ideal for representing data models, especially REST API responses, because they eliminate the boilerplate that Java would require writing manually or using Lombok.

By default, val (immutable) properties are generated, which is the recommended practice in Kotlin for data models. val means the value cannot be reassigned after initialization, making objects more predictable and thread-safe. Use var only if you need to mutate the object after creation.

Yes. The @Serializable annotation from kotlinx.serialization, Kotlin's official JSON serialization library, is added. @SerialName is also added when the JSON field name differs from Kotlin's camelCase convention, for example when the JSON uses snake_case.

When a value in the JSON is null, or when a field is not present in all objects of an array, the property is generated as a nullable type using the ? operator. For example, String? instead of String. In Kotlin, the distinction between nullable and non-nullable types is part of the type system and the compiler verifies it at compile time.

In Android development, Kotlin data classes are used mainly to model REST API responses with Retrofit, store data in local databases with Room, serialize objects to pass between Activities/Fragments as Parcelable, and as models in MVVM or MVI architectures. Since Google adopted Kotlin as the official language for Android in 2019, data classes are the de facto standard.