Easy way to convert Iterable to Collection
Solution 1:
With Guava you can use Lists.newArrayList(Iterable) or Sets.newHashSet(Iterable), among other similar methods. This will of course copy all the elements in to memory. If that isn't acceptable, I think your code that works with these ought to take Iterable
rather than Collection
. Guava also happens to provide convenient methods for doing things you can do on a Collection
using an Iterable
(such as Iterables.isEmpty(Iterable)
or Iterables.contains(Iterable, Object)
), but the performance implications are more obvious.
Solution 2:
In JDK 8+, without using any additional libs:
Iterator<T> source = ...;
List<T> target = new ArrayList<>();
source.forEachRemaining(target::add);
Edit: The above one is for Iterator
. If you are dealing with Iterable
,
iterable.forEach(target::add);