docs: public static boolean isEqualOrNull( Object s1,
                                           Object s2 ) {
          if ( s1 == null
                  && s2 == null ) {
              return true;
          } else if ( s1 != null
                  && s2 != null
                  && s1.equals( s2 ) ) {
              return true;
          }
          return false;
      }