On 3/7/19 9:41 AM, Peter Levart wrote:
There is a benefit in the runtime though. The code can decide what to
do with the passed-in Iterable depending on it implementing
IterableOnce or not. Much like what RandomAccess interface does to
List(s). The code can decide to dump the iterable into a List and
iterate the List multiple times if the Iterable implements
IterableOnce or do direct multiple iteration on the passed-in Iterable
if it doesn't.
Expanding on this further, there could be help for multi-pass iteration
in the Iterable(Once) interfaces. For example:
public interface Iterable<T> {
Iterator<T> iterator();
default Iterable<T> toMultipassIterable() {
return this;
}
}
and then:
public interface IterableOnce<T> extends Iterable<T> {
@Override
default Iterable<T> toMultipassIterable() {
List<T> list = new ArrayList<>();
for (T t : this) {
list.add(t);
}
return list;
}
}
... so any new code that needs multiple passes can do so easily.
Regards, Peter
