code: public static <T> List<T> mergeLists(List<T> list1, List<T> list2) {
          List<T> merged = new LinkedList<T>();
          if (list1 != null) {
              merged.addAll(list1);
          }
          if (list2 != null) {
              merged.addAll(list2);
          }
          return merged;
      }
docs: Returns a new list containing the second list appended to the first list.