Translate semantics, not only punctuation
Kotlin removes some Java ceremony but keeps important JVM behavior. == calls structural equality, while === compares reference identity. Classes are final by default. Nullable types explicitly describe values that may be absent, although Java interoperability can still expose platform types with weaker null guarantees.
data class Topic(val name: String)
fun main() {
val a = Topic("Kotlin")
val b = Topic("Kotlin")
println(a == b)
println(a === b)
val length = a.name.length
println(length)
}
This prints true, false, and 6. The data class generates equality using constructor properties, while these are still two distinct instances. Properties provide accessor syntax; they do not imply that all access is a direct field read.
Kotlin does not enforce checked exceptions. When calling Java, you still need to understand failures declared by that API even though Kotlin does not require a catch block.
Exercise
Translate a small Java value object into a Kotlin data class. Compare equality, mutability, constructors, and null handling. Test two separate instances with equal contents.
Check: explain what would change if Topic were an ordinary class with no custom equals implementation.