code: public static <T> List<T> multiply(List<T> self, Number factor) {
          return (List<T>) multiply((Iterable<T>) self, factor);
      }
docs: Create a List composed of the elements of this Iterable, repeated
  a certain number of times.  Note that for non-primitive
  elements, multiple references to the same instance will be added.
  <pre class="groovyTestCase">assert [1,2,3,1,2,3] == [1,2,3] * 2</pre>
  
  Note: if the Iterable happens to not support duplicates, e.g. a Set, then the
  method will effectively return a Collection with a single copy of the Iterable's items.
  
  @param self   a List
  @param factor the number of times to append
  @return the multiplied List
  @since 2.4.0