code: @SuppressWarnings({ "unchecked", "rawtypes" })
      public List<?> mergeLists(List<?> list1, List<?> list2) {
          List list = new ArrayList(list1.size() + list2.size());
          list.addAll(list1);
          list.addAll(list2);
          return list;
      }
docs: Create a new {@link ArrayList} instance adding all values of the given
  lists together.  The second list will essentially be added after the
  first list. Note that any duplicates between lists will remain as
  duplicates.
  
  @param list1 The first list to merge
  @param list2 The second list to merge
  
  @return The newly created list containing the merged lists