code: public static <E> Collection<E> sampleWithoutReplacement(Collection<E> c, int n) {
      return sampleWithoutReplacement(c, n, new Random());
    }
docs: Samples without replacement from a collection.
  
  @param c
  The collection to be sampled from
  @param n
  The number of samples to take
  @return a new collection with the sample