docs: public static <T> T[] join(final T[] base, final T... add) {
          if (add == null) {
              return base;
          } else if (base == null) {
              return add;
          }
          if (add.length == 0) {
              return base;
          }
          final T[] result = Arrays.copyOf(base, base.length + add.length);
          System.arraycopy(add, 0, result, base.length, add.length);
          return result;
      }