android/guava/src/com/google/common/collect/Iterables.java
public static int size(Iterable<?> iterable) {
    return (iterable instanceof Collection)
        ? ((Collection<?>) iterable).size()
        : Iterators.size(iterable.iterator());
  }
public static int size(Iterable<?> iterable) {
    return (iterable instanceof Collection)
        ? ((Collection<?>) iterable).size()
        : Iterators.size(iterable.iterator());
  }
Returns the number of elements in {@code iterable}.