kotlin-stdlib / kotlin.collections / addAll addAll Common JVM JS Native 1.0 fun < T > MutableCollection < in T > . addAll ( elements : Iterable < T > ) : Boolean (source) Adds all elements of the given elements collection to this MutableCollection . Common JVM JS Native 1.0 fun < T > MutableCollection < in T > . addAll ( elements : Sequence < T > ) : Boolean (source) Adds all elements of the given elements sequence to this MutableCollection . Common JVM JS Native 1.0 fun < T > MutableCollection < in T > . addAll ( elements : Array < out T > ) : Boolean (source) Adds all elements of the given elements array to this MutableCollection .