The open
keyword means “open for extension“:
The open
annotation on a class is the opposite of Java's final
: it allows others to inherit from this class. By default, all classes in Kotlin are final
, which corresponds to Effective Java, Item 17: Design and document for inheritance or else prohibit it.
You also need to be explicit about methods you want to make overridable, also marked with open
:
open class Base {
open fun v() {}
fun nv() {}
}
The public
keyword acts as a visibility modifier that can be applied on classes, functions etc.
Note that public
is the default if nothing else is specified explicitly:
If you do not specify any visibility modifier, public
is used by default, which means that your declarations will be visible everywhere
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