code: @SafeVarargs
      public static Integer[] box(final int... a) {
          if (a == null) {
              return null;
          }
  
          return box(a, 0, a.length);
      }
docs: <p>
  Converts an array of primitive ints to objects.
  </p>
  
  <p>
  This method returns {@code null} for a {@code null} input array.
  </p>
  
  @param a
  an {@code int} array
  @return an {@code Integer} array, {@code null} if null array input