code: public <U> StreamEx<U> elements(U[] array) {
          return mapToObj(idx -> array[idx]);
      }
docs: Returns an object-valued {@link StreamEx} consisting of the elements of
  given array corresponding to the indices which appear in this stream.
  
  <p>
  This is an intermediate operation.
  
  @param <U> the element type of the new stream
  @param array the array to take the elements from
  @return the new stream
  @since 0.1.2