docs: public static int comp(Integer v1, String s1, Integer v2, String s2) {
          if (v1 != null && v2 != null) {
              return v1.compareTo(v2);
          }else if(v1!=null){
              return 1;
          }else if(v2!=null){
              return -1;
          } else if (null == s1 && null == s2) {
              return 0;
          } else if (null == s1) {
              return -1;
          } else if (null == s2) {
              return 1;
          } else {
              //compare lexicographically
              return s1.compareTo(s2);
          }
      }