Kotlin basics: inheritance modifiers. final, open, abstract and override.

Photo by Slim Emcee (UG) the poet Truth_From_Africa_Photography on Unsplash

final: default

As we will see later, you need to mark a class with the open keyword to let it be extended. When we are changing a extended class the explicit open keyword, inform us that we should review the derived classes, and check if our changes in the super class are compatible with the subclasses.

open

abstract

override

Note: final by default and smart casting

if (input is Int) {
return input + 1 // Here there is no need for explicit casting.
}

Summary

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Android-Kotlin Developer

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