kotlinserializationdata-class

Is Kotlin data class serializable by default?

After knowing Kotlin, love the data class. I could replace Java classes that has equal and hash and toString to it. Most of these Java classes are serializable class. So my question is, when we convert to data class, do I still need to make it serializable explicitly? like

data class SomeJavaToKotlinClass(val member: String) : Serializable

Or it is okay to be

data class SomeJavaToKotlinClass(val member: String)
Solution

  • No, Kotlin data classes do not implicitly implement this interface. You can see from this example:

    import java.io.Serializable

data class Foo(val bar: String)

fun acceptsSerializable(s: Serializable) { }

fun main(args: Array<String>) {
    val f: Foo = Foo("baz")
    
    // The following line produces the compiler error:
    // Type mismatch: inferred type is Foo but Serializable was expected
    acceptsSerializable(f)
}