code: public static boolean isEqualOrNull( Map s1,
                                           Map s2 ) {
          if ( s1 == null
                  && s2 == null ) {
              return true;
          } else if ( s1 != null
                  && s2 != null
                  && s1.size() == s2.size() ) {
              return true;
          }
          return false;
      }
docs: Check whether two Map are same size or both null.
  @param s1
  The fist Map..
  @param s2
  The other  Map.
  @return Whether two Map are same size or both null