Wonder Shine Blog

Java @Override vs Kotlin override

•

Java

By default, if one class’s function have

  1. exactly same arguments
  2. same or subtype return type
  3. The access level is same or less restrictive
  4. non-final method
  5. …
  6. same function name

it overrides parent’s function.
@Override enables subclass to override parent’s method without 6) condition.
@Override is nothing to do with bytecode. It’s retention is source-code only. It’s just a hint for compiler.

Kotlin

Same rule for overriding with java, but the functions in Kotlin are defined as final, by default. That means you cannot override them.
That is:

  • java uses final to prevent override in inheritance. (default = enable)
  • kotlin uses open to allow override in inheritance. (default = disable)

References

https://thdev.tech/kotlin/2016/10/09/Kotlin-Class/ https://www.quora.com/Does-Override-have-any-effect-on-bytecode https://stackoverflow.com/questions/46399430/difference-between-open-and-override-methods-in-kotlin https://crunchify.com/java-method-overriding-examples-and-concepts-overriding-rules/ https://thdev.tech/kotlin/2016/10/09/Kotlin-Class/