code: public static Object min(Comparable c1, Comparable c2) {
      if (c1 != null && c2 != null) {
        return c1.compareTo(c2) < 1 ? c1 : c2;
      } else {
        return c1 != null ? c1 : c2;
      }
    }
docs: Null safe comparison of Comparables.
  
  @param c1 the first comparable, may be null
  @param c2 the second comparable, may be null
  @return <ul>
  <li>If both objects are non-null and unequal, the lesser object.
  <li>If both objects are non-null and equal, c1.
  <li>If one of the comparables is null, the non-null object.
  <li>If both the comparables are null, null is returned.
  </ul>