code: public static int[] unbox(final Integer[] a, final int valueForNull) {
          if (a == null) {
              return null;
          }
  
          return unbox(a, 0, a.length, valueForNull);
      }
docs: <p>
  Converts an array of object Integer to primitives handling {@code null}.
  </p>
  
  <p>
  This method returns {@code null} for a {@code null} input array.
  </p>
  
  @param a
  a {@code Integer} array, may be {@code null}
  @param valueForNull
  the value to insert if {@code null} found
  @return an {@code int} array, {@code null} if null array input