Implement java.io.Serializable on the JVM

Hello, Please make the Android actual types implement also java.io.Serializable (not Kotlin @Serializable as described in #37). This will allow us to make the complex types, which depends on kotlinx.datetime.* types either Serializable or Parcelable in Android app.

For instance, java.time.Instant IS Serializable, however the actual Android class kotlinx.datetime.Instant is NOT.

[smallufo]

Not related to android. I want to use kotlinx-datetime in wicket. But all wicket models mandate Serializable interface, otherwise NotSerializableException will be thrown.

[dkhalanskyjb]

What do you think about writing Serializable Adapters for our classes in place? We provide compatible toString and parse for everything.

An overly cautious example that can be slightly simplified if you know what you’re doing:

public data class LocalDateModel(@Transient var value: LocalDate): java.io.Serializable {
    private fun writeObject(oStream: ObjectOutputStream) {
        oStream.defaultWriteObject()
        oStream.writeObject(value.toString())
    }
    private fun readObject(iStream: ObjectInputStream) {
        iStream.defaultReadObject()
        value = LocalDate.parse(iStream.readObject() as String)
    }
    private fun readObjectNoData() {
        throw InvalidObjectException("Stream data required")
    }
}

(be careful to check out serialVersionUid if you plan to change this class)